Note: Descriptions are shown in the official language in which they were submitted.
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PREPARATION OF CHITOSAN-BASED MICROPOROUS
COMPOSITE MATERIAL AND ITS APPLICATIONS
CROSS R.EFFRENC/NCI TO RELATED APPLICATION
This application claims the benefit of and priority to U.S. Cif' Patent
Application 15/935,398, filed March 26, 2018, the entire contents of which is
incorporated
herein by reference for all purposes.
BACKGROUND
E Field
100021
Disclosed herein are methods for mEAification of chitosan that
increases their versatility as sorbents, particularly as sorbents of
radioisotopes, as well the
ability of these materials to function in environments where radioactivity is
present, Also
disclosed are the materials themselves, as well as methods of using them to
separate and
purify radioisotopes, and to separate and purify contaminated materials, in
particular those
radioactive and nonradioactive streams contaminated by metal ions,
particularly those of
heavy metals,
2. Description of Related Art
R.10031
Radioactive isotopes are 1,videly used, particularly in the field of
nuclear medicine, both for therapy and imaging. However, these materials can
present
production, storage, and disposal challenges due to their radioactivity, as
well as their often
sign ficant halfllves.
10011)41 More
particularly, in the radiopharmaceutical area, 99rfc (having a
half-life tv,2 6h), is
one of the most widely used radioisotopes in diagnostic medicines
obtained from the decay product of parent 'Nlo (11,e,kk.66 h). 99mIC is a pure
gamma emitter
(0,143 MeV) ideal for use in medical applications due to its short half-life
(6 hours).
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It is used in 80-85% of the approximately 25 million diagnostic nuclear
medicine procedures
performed each year.
[0005) The
parent 'Mo can be produced by the irradiation of 98Mo with
thermallepithermal neutrons in a nuclear reactor, but much of the world supply
of "Mc,
comes from the fission product of highly enriched uranium (1-1E1J) in a
reactor. The fiEU
process generates large quantities of radioactive waste and does not permit
reprocessing of
the unused uranium targets due to weapons proliferation concerns,
[00061 Low
enriched uranium (LIU, 20 percent 235U or less) could be used as
a substitute, but would yield large volumes of waste due to the large
quantities of un-useable
23sU present. Currently, most of the world supply of "Mo conies from sources
outside of the
United States, Recent 99Mo production outages at these sources have disrupted
medical
procedures and have demonstrated the unreliability of this supply chain. This
stresses the
need for economically feasible alternative sources to produce "mTc from q9Mo.
[0071 The main
concerns with neutron capture-produced "Mo, as compared
to the more common .fission-produced material described above, involves both
lower curie
yield and lower specific activity. The specific activity is significantly
lower and is of great
concern due to impacts on 99Mol"mTc generator size, efficiency, and
functionality.
Therefore, use of lower specific activity molybdate is only feasible with a
more efficient
sorbent to reduce the generator size and to yield a usable dose at the
radiopharinacy. Several
research works have been focused on the uses of a molybdenum gel generator.
See Marageh,
et al., "Industrial-scale production of 99mIc generators for clinical use
based on
zirconium molybdate gel," Nuclear Technology, 269, 279-284 (2010); Monoroy-
Guzmari,
et al., "9No.199mTc generators performances prepared from zirconium molyhdate
gels" .1,
Braz. Chem, Soc., 19, 3, 380-388 (2008). Others focused on preparation of
"Mol'rc
generator based on polymeric or inorganic oxide as an adsorbent material for
"Mb, See
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IVIasakazu, T. et al,, A i;t*Tc, generator using a new organic polymer
absorbent for (ri,y)
Appi. Radia. Isot, 48, 5, 607-711 (1997); Qazi, QM. et al., "Preparation and
evaluation of hydrous titanium oxide as a high affinity adsorbent for
molybdenum (99Mo) and
its potential for use inT generator," Radiochim. Acta, 99, 231-235 (201 1).
[MS!' However,
such medical uses require that the 99" TC he produced in
highly purified form For example, when 99mTc is produced from the decay of
"Nlo, it is
important to achieve a high degree of separation of the two elements in order
to meet
regulatory requirements.
[0009] One
approach to achieving this level of purity is to separate*Olc from
"Mo using a highly efficient, selective sorbent, e.g, by sorbing 99 M o and
eluting 99'Te.
Attempts have been made to use alumina as such a sorbent. However, this
alumina provides
an efficiency for Moof about 25 meg of sorbent. Accordingly, there remains a
need in the
art for a sorbent that is both efficient in the adsorption of 99Mo, and
resistant to the adverse
effects of ionizing radiation. In addition, there remains a need for a sorbent
that is highly
selective for 99 M o , i.e., that is capable of sorbineMo while providing good
release orrn'Tc.
[0010] More
generally, there remains a need for a sorbent that is readily
available, or producible from readily available materials, and that is
customizable by
modification to have one or more functional groups (which may be the same or
different)
allowing the material to remove constituents from a process stream requiring
such
purification, and that is resistant to degradation by ionizing radiation.
100111 The ion
exchange process, which has been used for decades to separate
metal ions from aqueous solution, is oflen compared to adsorption. The primary
difference
between these two processes is that ion exchange is a stoichioinetric process
involving
electrostatic forces within a solid matrix, whereas in adsorptive separation,
uptake of the
solute onto the solid surface involves both electrostatic and Van der Waals
forces. In an
3
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attempt to find a suitable ion exchange resin for the removal of cesium and
strontium from
waste solution, several investigators have tried a number of inorganic,
organic, and bio-
adsorbents, with a varying degree of success. See Gu, D., Nguyen, L., Philip,
C,V,
Flucktnen, M.E., and Anthony, R.G. "Cs ion exchange kinetics in complex
electrolyte
solutions using hydrous crystalline silicatitanates", 1nd, .F112. Chem. Res.,
36, 5377-5383,
1997; Pawaskar, C.S., Mohapatra, PAC., and Mancharida, V.K. "Extraction of
actinides
fission products from salt solutions using polyethylene glycols (PF,Cis)"
Journal of
Radioanalytieal and Nuclear Chemistry, 242 (3), 627-634, 1999; Dozol, J,F.,
Simon, N,,
Lamare, Võ et al. "A solution for cesium removal from high salinity acidic or
alkaline liquid
waste: The Crown calyx[4]arenas" Sep. Sci. Technol., 34 (6&7), 877-909, 1999;
Arena, G.,
Contino, Aõ Margi, A. et al. "Strategies based on calixcrowns for the
detection and removal
of cesium ions from alkali- containing solutions, lad. Eng. Chem. Res., 39,
3605-3610, 2000.
100121 However,
major disadvantages with the ion exchange process are the
cost of the material and regeneration for repeated use when treating
radioactive streams, See
Hassan, N,,Adu-Wusti, K., and Marra, J.C. "Resorcinol-fOrmaldellyde adsorption
of cesium
(Cs+) from Hanford waste solutions-Part I: Batch equilibrium study" .WSRC-MS-
2004. The
cost of disposal is also a major issue. The success of adsorption processes
depends largely on
the cost and capacity of the adsorbents and the ease of regeneration,
10013.1 Chitosan
is a partially acetylated glucosamine polymer encountered in
the cell walls of fungi. It results from the deacetylation of chitin, which is
a major
component of crustacean shells and available in abundance in nature. This
biopolymer is
very effective in adsorbing metal ions because of its ability for complexation
due to high
content of amino and hydroxyl functional groups. In their natural form,
ehitosan is soli. and
has a tendency to agglomerate or form gels in acidic medium. Moreover,
ehitosan, in its
natural form, is non-porous and the specific binding sites of this biopolymer
are not readily
4.
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available for sorption. However, it is necessary to provide physical support
and chemical
modification to increase the accessibility of the metal binding sites for
process applications, it
is also essential that the metal binding functional group should be retained
after any such
modification.
10014] It is
well known that polysaccharides can be degraded due to scission
of glycoside bonds by ionizing radiation. 1AEA-TECDOC-1422, "Radiation
processing of
polysaccharides' International Atomic Energy Agency, November, 2004. The
hydrogel
based on polysaccharides and their derivatives has been extensively studied,
but very limited
work has been reported so far on the impact of radiation on the chitosan-based
inicroporotis
composite materials and their metal ion uptake capacity,
100151 Chitosan is a non-toxic, biodegradable material, It has
been
investigated for many new applications because of its availability,
polycationic character,
membrane effect, etc. The amino group present in the chitosan structure is the
active metal
binding site, but it also renders chitosan soluble in weak acid. In acidic
media, chitosan tends
to form a gel which is not suitable for adsorption of metal ions in a
continuous process.
[011161 Several
reports indicated that the cross-linking of chitosan with
gluteraldehyde make chitosan acid or alkali resistant. See Elwakeel, KZ.,
Atia, A,A., and
Dania, A,M, " Removal of MOVI) as oxoanions from aqueous solutions using
chemically
modified magnetic chitosan resins, Hydrometaliurgy, 97, 21-28, 2009; Chassary,
P.,, Vincent,
T., and Guibal, E. " Metal anion sorption on chitosan and derivative
materials: a strategy for
polymer modification and optimum use" Reactive and Functional Polymers, 60,
I37-149,
2004; Velrntirtigan, N., Kurnar,G.0,, Han, S.S. Nahm, K.S,õ and Lee, Y.S.
"Synthesis and
characterization of potential fungicidal silver nano-sized particles and
chitosan membrane
containing silver particles" Iranian Polymer Journal, /8 (5), 383-392, 2009.
Gluteraidehyde
is a live carbon molecule terminated at both ends by aldehyde groups which are
soluble in
.5.
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water and alcohol, as well as in organic solvents. It reacts rapidly with
amine groups of
chitosan durine cross-linking through Schiff's reaction and generates
thermally and
chemically stable cross-links, See Migneault, L, Dartiguenave, C, Bertrand,
Mi., and
Waldron, K.C. "Gluteraldehyde; behavior in aqueous solution, reaction with
proteins, and
application to enzyme crosslinking"- Bio Techniques, 37 (5), 790-802, 2004.
The amine
groups are also considered as the active metal binding sites of chitosan.
Therefore, by cross-
linking with gluteraldehyde, the chitosan is reported to be acid or alkali
resistant but the metal
adsorption capacity will be reduced.
[00171 Li and
Bai (2005) proposed a method to cap the amine group of
chitosan by formaldehyde treatment before cross-linking with gluteraldehyde,
which was
then removed from the chitosan structure by washing thoroughly with 0.5M Ha
solution,
Li, Nan, and Bai, R. " A novel amine-shielded surface cross-linking of
chitosan hydrogel
beads for enhanced metal adsorption performance" Ind, Eng. Chem, Res,, 44,
6692-6700,
2005.
[00181
Crosslinking of chitosan with different functional groups is thought to
depend mainly on the crosslinking reaction conditions, such as pH,
temperature, ionic
concentration, and the surface charge of the materials.
[00119] Sine et
al. (2006) showed that swelling properties of chitosan hydrogel
cross-linked with formaldehyde depends on the responsive behavior of pH,
temperature, and
ionic strength. Singh, A., Narvi, Duttaõ
P,K., and Pandey, N.D. "External stimuli
response on a novel chitosan hydrogel crosslinked with formaldehyde" Bull.
Mater. Sci., 29
(3), 233-238, 2006,
10020/ The
surface charge of the chitosan that determines the type of bond
that will form between the cross-linking agent and chitosan, depends on the pH
of the
solution. Hasan, S., Krishriaiah, A., Ghosh,
Viswanath, Boddu, V.M., and Smith,
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E. D. "Adsorption of divalent cadmium from aqueous solutions onto ehitosan-
coated perlite
heads, Ind, Eng, Chem, Res., 45, 5066-5077, 2006, The point of zero charge
(PZC) value of
pure chitosari is in the pH range of 6,2-6.8, See Hasan, S., Ghosh, T.K,,
Viswanath, DS.,
Loyaika, S,K,, and Sengupta, 13, "Preparation and evaluation of fullers earth
for removal of
cesium from waste streams" Separation Science and Technology, 42 (4), 717-738,
2007,
Chilosan is not soluble in alkaline pH, but at acidic pH, the amine groups
present in the
ehitosan can undergo protonation to NH 3+ or (N112-1-130)+.
[0021] Li et at
(2007) reported cross-linked chitosanlpolyvinyl alcohol (PVA)
beads with high mechanical strength. They observed that the irr ions in the
solution can act
as both protection of amino groups of chitosan during the crosslinking
reaction, Li, M.,
Cheng, S., and Yen, H. "Preparation of crossliriked chitosanipoly(vinyl
alcohol) blend beads
with high mechanical strength", Green Chemistry, 9, 894-898, 2007,
I0022] Farris
et at (2010) studied the reaction mechanism for the cross-
linking of gelatin with gluteraldehyde. Farris, S., Song, J,, and Huang, Q.
"Alternative
reaction mechanism for the cross-linking of gelatin with ghtteraldehyde" I.
Agrie. Food
Cheat, 58, 998-1003, 2010. They suggested that, at higher pH values, the cross-
linking
reaction is governed by ScititT's base reaction, whereas at low pH, the
reaction may also
involve -OH groups of hydroxyproline and hydroxylysine, leading to the
formation of
hem iaceta Is.
[0023] Hardy et
at (1969) proposed that, at acidic pH, gluteraldehyde is in
equilibrium with its cyclic hemiacetal and polymers of the cyclic hemiacetal
and an increase
in temperature produces free aldehyde in acid solution, Hardy, P.M., Nicholas,
A.C., and
Rydon, 11,1\i. "The nature of gluteraidehyde in aqueous solution" Journal of
the Chemical
Society (D), 565-566, 1969.
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[00241 Several
studies focused on ehitosanbased cross-linked material for
medical and radiopharmaceutical uses with sonic success. See, e.g,, Hoffman,
B., Seitz,
Menke, A., Kokon. A., and Ziegler, a "Gluteraldehyde and oxidized dextran as
crosslinker
reagents for chitosan-based scaffolds for cartilage tissue engineering" J.
Mater Sci: Mater
Med, 20(7), 1495-1503, 2009; Salmawi, KM, "Gamma radiation-induced crosslinked
PVA?Chitosari blends for wound dressing" Journal of Macromolecular Science,
Part A: Pure
and Applied Chemistry, 44, 541-545, 2007; Desai, K, G,, and Park, Hi, "Study
of gamma-
irradiation effects on chitosan microparticles" Drug Delivery, 13, 39-50,
2006; Silva, R.N1.,
Silva, GA, Coutinho, 0.P., Marto, LP., and Reis, R.L. "Preparation and
characterization in
simulated body conditions of gluteralclehyde crosslinked chitosan membranes"
Journal of
Material Science: Materials in Medicine, 15 (10), 1105-1112, 2004,
[00251 However,
Sabharwal et al. (2004) reported that the radiation
processing of natural polymers has drawn less attention as the natural
polymers undergo
chain scission reaction when exposed to high energy radiation. Sabharwal, S.,
Varshney, L.,
Chaudhary, A.D., and Rainnani, SP. "Radiation processing of natural polymers:
Achievements & Trends" In Radiation processing of polysaccharides, 29-37,
IAEA,
November, 2004. lt is reported that irradiation of chitosan yields lower
viscosity and chain
scission of chitosan. See Kum, T., and Takehisa, M. "Effect of gamma-
irradiation on
sodium alginate and carrageenan powder" Agric, Biol, Chem, 47, 889-890, 1982;
Ulanski, P,.
and Rosiak, J.M. "Preliminary studies on radiation induced changes in
chitosan" Radiat,
Phys. Chem, 39(1), 53-57, 1992. The /V and Olt radicals formed by radiolysis
during
irradiation of water accelerate the molecular chain scission of chitosan. The
reaction between
the above free radical and chitosan molecules leads to rapid degradation of
chitosan in
aqueous solution. See 1AEA-TECDOC-1422, "Radiation processing of
polysaccharides'
International Atomic Energy Agency, November, 2004. These 5tudks suggest that
the use of
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chitosan in environments where it will be exposed to irradiation and potential
radiolysis is
problematic,
100261
Nevertheless, the current demands for biocompatible polymeric
materials in radiopharmaceutical and radioactive waste treatment have
increased the interest
in developing economically feasible alternative sources of acidic, alkaline,
and radiation
resistant polymer network structures. Recent development of chitosan-based
materials in the
area of medical, radiopharmaceuticals, and radioactive waste has drawn
attention due to their
availability and biocompatibility, See Alves, N.M., and Marto, ii-. "Chitosan
derivatives
obtained by chemical modifications for biomedical and environmental
applications"
International Journal of Biological Macromolecules, 43, 401-414, 2008; Berger,
J., Reist, M.,
Mayer, Felt,
O., Peppas, N.A., and Gurriy, R. "Structure and interactions in covalently
and ionically crosslinked chitosan hydrogels for biomedical applications,
European Journal of
Pharmaceutics and Biopharmaceutics, 57, 19-34, 2004. It is reported that the
chemical
changes in chitosan occur due to irradiation and the extent of radiation-
induced reaction
depends on the polymer network structure. See Zaino!, 1,, AU, HM., and
lvlastor, A. "Effect
of y-ray irradiation on the physical and mechanical properties of chitosan
powder" Material
Science and Engineering C, 29, 292-297, 2009; Chang, K.P, Chen, C.H., Chiang,
Lee, S.C. et al., "Irradiation of synthesized magnetic nanoparticies and its
application for
hyperthermia" Advanced Materials Research, 47-50, 1298-1301, 2008; Casm ire,
M.1-1.,
Botelho, M,L., Leal, J.P., and Gil, M.H. "Study on chemical, UV and gamma
radiation-
induced grafting or 2-hydroxyethyl inethacrylate onto chitosan" Radiation
Physics and
Chemistry, 72, 731-735. 2005; Park et al. "Radioactive chitosan complex for
radiation
therapy" US Patent 5,762,903, June 9, 1998; Wenwei, Z., Xiaoguang, Z., Li, Yu,
Yuefang,
Z., and Jiazhen, S. "Some chemical changes in chitosan induced by y-ray
irradiation"
Polymer Degradation and Stability, 41, 83-84, 1993; Um, L. V., Khor, E,, and
Koo, 0. "y
9
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irradiation of ehitosan" Journal of Biomedical Material Research, 43 (3), 282-
2909 199S;
Yoksan, R. Akashi, M., Miyata, M., and Chirachanchai, S. "Optimal y-ray dose
and
irradiation conditions for producing low molecular weight chitosan that
retains its chemical
structure" Radiation Research, 161, 471480, 2004; Lit, Wei,
GS.. and Peng, J.
"Radiation degradation of chitosan in the presence of R202" Chinese Journal of
Polymer
Science, 22 (5)9 439444, 2004. However, there is very limited information
available on the
radiation effect on cross-linked chitosan composite matrices.
l0027) Current
research in the area of radiation resistance adsorbent materials,
pertaining to the technology development, for the selective separation of
isotopes and their
applications in medical and nuclear environmental field are the forefront of
science and
engineering. One of the main concerns of the adsorption techniques is the cost
of the resin
and their performance under high radiation environment. The chemical
properties of the
functional groups of the resin, which is active metal binding sites for resin,
are subject to
change by the interaction with ionizing radiation. In adsorption process, this
may cause poor
selectivity of the resin materials for metal ions and therefore hinders their
application.
10028] The
active surface of the resin is considered to be the critical structures
of MPCM resin, In case of exposing the MPCM resin to higher radiation field,
the critical
structure of the resin, which will primarily interact with the imparted energy
from the
ionizing radiation, needs to be protected. It is evident from IR and XPS
analysis that MPCM
resin may undergoes radiation induced cross-linking reaction under high
radiation field but
the performance for metal ion uptake before and after the irradiation reported
to be remained
same. However, the main constituents of MPCM resin are low Z elements (with
less stopping
power), therefore, the negative impact of high energy particles on MPCM
surface can be
minimized by maintaining proper aspect ratio of the column. Furthermore, the
critical
19:
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structure of the resin, which is also porous in nature, is assumed to be thin,
due to range
consideration; it should he protected also from interaction of radiation.
SUMMARY
[00291 One embodiment disclosed herein relates to a radiation-
resistant
sorbent comprising g,Intaraldehyde-crosslinked chitosan.
100301 More particularly, disclosed herein are chitosan-based
microporous
composite micron-size particles and chitosan-titartia microporous composite
material which
was prepared by cross-linking chitosan with gluteraldehyde in the presence or
a catalyst,
[0031j Even more particularly, disclosed herein is a sorbent
containing a
microporous material of chitosan that has been erosslinked with glutaraldehyde
in the
presence of a catalyst, such as an acid (e,z., HCI) to a glutaraldehyde
concentration of about 2
to 4 wt%, and which is resistant to degradation from exposure to beta and
gamma radiation,
and to degradation from exposure to acids or alkaline solutions,
100321 Without wishing to be bound by theory, it is believed that the
cross
linked microporous chitosan matrix enhances the acid resistance and mechanical
strength of
the chitosan particle. As a result, the uptake capacity of the cross-linked
particles increases
for metal ions from acidic or alkaline radioactive solution in comparison to
available
commercial resins and commercial alumina& This increased uptake can result in
efficiencies
for molybdenum as high as 500-700 rrig/g or sorbent, more particularly, about
600 ingig of
sorbent,
[0031 Described herein are embodiments of chitosan-based microporous
composite materials which were prepared using solution casting and combination
of solution
casting and sol-gel method,
[00341 In one embodiment, chitosan was cross-linked with
gluteraldehyde in
the presence or acid as a catalyst at temperatures of around 70PC under
continuous stirring.
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Without wishing to be bound by theory, it is believed that amino groups
present in the
chitosa.n structure are protortated, and thus shielded from the reaction with
gluteraldehyde, it
is also believed that at temperatures of around 70 C., more aldehyde groups
are available for
reaction than are available at room temperature. In this case, without wishing
to be bound by
theory, it is believed that glutaraidehyde undergoes aldoi condensation and
the free aldehyde
group will react with OH groups of chitosan in the presence of an acid
catalyst, so that the
polymerization of chitosan with giutaraldehyde is a condensation
polymerization. Reaction
times generally range from about 4 hours to about 8 hours, In one embodiment,
the mole
ratio of ehitosan hydroxyl group to gluteraldehyde is desirably maintained at
around 411.
[00351 In a
particular embodiment, the crosslinked material can be further
processed by, washing to remove excess glutaraldehyde, drying, wet or dry
milling, and
additional chemical processing. One example of this additional chemical
processing that has
been found to be particularly suitable is at least partial oxidation with an
oxidizer. In
particular, oxidation with one of more of a permanganate (e.g., by a potassium
permanganate
solution containing at least about l4 mg ?AWL of solution), a peroxide, a
chlorite, a
hypochlorite, a dichromate, or a metal oxide, or other arnbiphilic oxidizer,
is especially
suitable for increasing the selectivity of the sorbent for Mo(til) with
respect to Tc(Vil), and
for the efficient and rapid elution and recovery of technetium from loaded
sorbent. More
particularly., an oxidizer comprising one or more of an alkali metal chlorite,
an alkali metal
hypochlorite, an. alkali metal dichromate, or a transition metal oxide is
desirably used. More
particularly, an oxidizer comprising one or more of sodium chlorite, sodium
hypochlorite,
potassium dichromate, or cerium oxide is desirably used. In addition to
oxidizing the
crosslinked sorbent material, these oxidizers can desirably be included in an
eluent solution
used to release technetium from the sorbent. Desirably, such oxidizers are
included in a
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saline-containing einem solution in concentrations ranging from about 5 to
about 40 ritM for
chlorites or hypochlorites.
[00361
Desirably, the sorbent has a surface area that ranges between about 10
and about 100 m2/g, and more particularly is about 25 mg, Also desirably, the
,sorbent has a
point of zero charge ranges from about 7.5 to about 8.8, and more particularly
is about 8.8,
[00371
Embodiments of the sorbents described herein have an excellent
holding capacity for molybdenum, and can sorb molybdenum in amounts of around
60 wt%,
based on the dry weight of the sorbent, or higher. This bolding capacity can
be around 6,25
minolig of sorbent, or higher. The sorhents also have excellent selectivity
for molybdenum
with respect to technetium, and are able to hold molybdenum while passing
pertechnate ion
in saline solution with an efficiency of at least about 80%. Embodiments of
the sorbents
disclosed herein also provide excellent capacity to sorb heavy metals,
including, e.g., the
ability to sorb H2 in amounts of 236 mmag dry sorhent or higher from aqueous
solution at
pH 6,
[00381 In
another embodiment, titanium oxide was incorporated into the
chitosan gluteraldebyde composite polymer matrix. The development of
crystalline silica
titariate (CST) and titanium-based oxide materials has paved the way for metal
ions
adsorption studies onto hydrous titanium oxide from the radioactive and non-
radioactive
waste streams. See Anthony, R. Gõ Dosch, R.Gõ Ga. Dõ and Philip, C.V. "Use of
silicotitanates for removing cesium and strontium from defense waste" Ind,
Eng, Chem. Resõ
33, 2702-2705, 1994; Maria, Põ Meng, Xõ Korfiatis, G.Põ and Jingõ C.
"Adsorption
mechanism of arsenic on nanoerystalline titanium dioxide" Environ, Sci.
Technol, 40, 1257-
262, 2006; Meng et al., "Methods of preparing a surface-activated titanium
oxide product
and of using same in water treatment process" US Patent 7,497,952 B2, March 3,
2009. Qazi
and Ahmed (201 l) reported the hydrous titanium oxide as an adsorbent for "Mo
and its
13.
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potential for use in ''""'Tc: generator, Qazi, Q,M., and Ahmed, M.
"Preparation and evaluation
of hydrous titanium oxide as a high affinity adsorbent for molybdenum (99Mo)
and its
potential for use in 99mIc generators" Radiochimica Acta, Doi:
10,1524tract,201 I ,1817201
It has been suggested that titanium oxide can form surface complex with metal
ion resulting
from a bidenate bonding mode to surface oxygen atoms, Flasart, S. Ghosh, T,K.,
Prelas,
Viswanath, D.S., and Boddu, V.M, "Adsorption of uranium on a novel
bioadsorbent
chitosan coated pulite" Nuclear Technology, 159, 59-71., 2007,
10039] However, none of these documents disclose that TiO2, when
dispersed
on chitosan matrix, would enhance the overall capacity for metal ions uptake
from
radioactive waste solution. In the method disclosed herein, hydrous titanium
oxide ni was
prepared using the sol-gel technique. The titanium oxide gel was incorporated
into the
chitosan and gluteraldehyde matrix in the presence of Ha as a catalyst,
10040] Thus, one embodiment relates to a method for preparing a
radiation
resistant sorbent, comprising:
[00411 combining chitosan with water in the presence of an acid to
form a
chitosan gel;
[00421 adding gititaraldehyde to the gel to form a semi-solid mass in
presence
of catalyst at 700C;
[00431 washing the semi-solid mass to remove unreacted giutaraidehyde
and
form a washed mass;
[0044I suspending the washed mass in aqueous base to form a
neutralized
erossi inked mass; and
[0045f drying the neutralized crosslinked mass to form the radiation-
resistant
sorbent,
[0046I Another embodiment relates to such a method further
comprising:
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[00471 forming an amorphous titania gel by acid catalyzed hydrolysis
and
condensation of titanium isopropoxide;
100481 mixing the amorphous titania gel with the chitosan gel under
conditions sufficient for the gels to react prior to said adding
glutaraldehyde.
[00491 In one embodiment, the chitosan-based microporotis composite
material was then suspended in a solution with pH 3 and irradiated at .50,000
krad using
"Coirradiatior, The specific objectives of this work were to I) prepare
chitosan-based
inicroporous composite particles to adsorb metal ions from highly acidic or
alkaline
radioactive waste solutions; and 2) optimize the cross-linking process to
obtain maximum
metal binding sites.
100501 Thus, another embodiment relates to a method of separating
isotopes
from mixtures thereof, comprising:
I 00511 contacting a mixture of at least two isotopes with a radiation
resistant
sorbent according to claim I that preferentially sorbs at least one of said
isotopes;
[00521 sorbing at least one of said isotopes onto or into said
sorbent while one
or more of the remaining isotopes are not significantly sorbed by the sorbent;
100531 removing said one or more remaining isotopes from said
sorbent.
[00541 Chitosan cross-linked composite is an excellent low cost
alternative
adsorption material compare to available resins, and thus a desirable
adsorbent material to
remove metal ions from radioactive and nonradioactive aqueous solutions. It
has been found
that the success of adsorption processes in the 99MaMmTe generator systems
depends largely
on the cost and capacity of the adsorbents and the ease of 9Tc release from
the generator.
The main problem with this particular method from a radiation safety
standpoint involves the
"breakthrough", or partial elution of the 99Mo parent along with the ""Te from
the generator,
which must be kept within Nuclear Regulatory Commission (NRC) standards.
Embodiments
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of the materials and methods described herein provide good, selective release
of 'Tc from
the generator, thereby solving this problem and fulfilling a need for such a
generator.
[00551 It is
believed that chemical element with a high atomic number of
protons in the nucleus, a high Z element, with higher stopping power will have
affinity for
certain isotopes can be crosslinked with MPCM resin matrix. It is also
envisaged that the
radiation tolerance limit and selectivity of the MPCM resin lbr certain
isotopes, can be
further enhanced by the high Z element crosslinked MPCM resin as it will not
be limited by
the radiolytic driven reaction. Therefore, it is a further embodiment to
provide a sorbent that
will reduce the primary impact of high radiation flux and minimize the
radiolytic effect on to
the MPCM's porous critical structure compared to regular organic based resin
such as
MPCM resin.
[00561 The
sorberit includes a microporous material including chitosan which
has been crossiinked with glutaraldehyde in the presence of a catalyst to a
tdutaraldehyde
concentration of about 2 to about 4 wt% to produce a cross-linked chitosan-
gluteraldehyde
composite matrix. The cross-linked chitosan-gluteraldehyde composite matrix is
resistant to
degradation from exposure to beta and gamma radiation and from exposure to
acids. A
plurality of nanoparticies of a. high Z element is disposed in the cross-
linked chitosan-
gluteraldehyde composite matrix and is integrated with the cross-linked
chitosan-
gluteraldehyde composite matrix.
100571 It is a
further embodiment to provide a method for preparing a
radiation-resistant sorbent, The method includes the steps of combining
chitosan with water
in the presence of an acid to form a chitosan gel. The method also includes a
step of adding
giutaraldehyde to the gel to form a semi-solid mass in the presence of
catalyst at 70C, in
where condensation polymerization of reaction mass occurs. The method further
includes a
step of washing the semi-solid mass to remove unreacted glutaraldehyde and
form a washed
:10.
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mass. The next step of the method is suspending the washed mass in aqueous
base to form a
neutralized crosslinked mass. Then, a plurality of nanoparticles of a high Z
element is
disposed on the neutralized crosslinked mass. Next, the neutralized
crosslinked mass
including the plurality of nanoparticles is dried under vacuum to form the
radiation-resistant
sorbent.
[00581 It is a
further embodiment to provide a method for preparing a plurality
of nanoparticles for use in a imdiation-resistant sorbent. The method includes
a first step of
grinding a salt of a high Z element with a surfactant under an inert
atmosphere. The method
also includes a step of adding deionized water of between 5m1 to 10ml during
the step of
grinding to form a homogenous mixture. The method further includes a step of
adding an
alkaline solution to the homogenous mixture under sonication to nucleate and
grow the
nanoparticles under an inert atmosphere. Next, the surfactant of the
homogenous mixture is
transferred into an alcohol solution containing the nanoparticies. Then, the
alcohol solution is
sonicated to obtain a uniform intermediate stage of the nanoparticles. The
precipitates, e.g.
intermediate stage of nartopartieles, are then sonicated and washed thoroughly
with ethanol
and deionized water to remove surfactant and impurities, respectively.
[00591 In
addition, embodiments of the chitosan crosslinked composites
disclosed herein can be used in a method for separating or concentrating or
both one or more
heavy metals from a liquid stream, such as a waste stream or a process stream,
by contacting
a liquid stream containing one or more heavy metals with the chitosan
crosslinked composite
and sorbing one or more of said heavy metals thereon,
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BRIEF DESCRIPTION OF DRAWINGS
PHI Various aspects of
the embodiments disclosed herein can be
understood more clearly by reference to the drawings, which should not be
interpreted as
limiting the claimed invention.
ilt.J61] FIG. I is a
scanning electron microscope photomicrograph that shows
chitosan and embodiments of modified chitosan (MPCM) disclosed herein, FIG la
shows
unmodified chitosan; FIG. lb shows an embodiment of MPCM material.
it1062) FIG. 2 is a graph
showing the results of a thermogravimetric analysis
(TGA) of chitosan and an embodiment of MPCM.
100631 FIG, 3 is a graph
showing an X-ray diffraction pattern of chitosan and
an embodiment of MPCM material.
100641 FIG. 4 is a graph
showing Fourier Transform Infrared (FTIR) spectra
of chitosan and an embodiment of MPCM material disclosed herein,
[00651 FIG. 5 is a graph
showing X-ray photoelectron spectroscopy (XPS)
survey scans for chitosan and an embodiment of MPetvl,
[00661 FIG, 6 is a graph
showing X-ray photoelectron spectroscopy (XPS)
spectra for chitosan and an embodiment of MPCM. FIG. 6a, 6b, and 6c show the C
Is, 0 Is,
and N I s positions, respectively,
PO67] FIG. 7 is a graph
of energy-dispersive X-ray spectrometry (EDS)
microanalysis spectra of an embodiment of MPCM herein. FIG 7a shows spectra of
chitosan
and an embodiment of MPCM before and after irradiation. FIG 7b shows
comparison of
chitosan and an embodiment of MPCM. FIG 7c shows comparison of an embodiment
of
MPCM before and after irradiation,
10068] FIG, 8 is a
schematic diagram showing a reaction pathway for the
preparation of an embodiment of MPCM described herein,
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100691 FIG. 9
is a graph showing FUR spectra fan embodiment of modified
chitosan disclosed herein before and after irradiation.
PON FIG. 10
is a graph showing X-ray photoelectron spectroscopy (XPS)
spectra for an embodiment of MPCM before an after radiation. FIG. I Oa, lab,
and 10c show
the C I s, 0 Is, and N I s positions, respectively.
100711 FIG. I I
is a graph showing surface charge of an embodiment of
MPCM with and without exposure to 1% of I'vlo (VI) in solution in the presence
of 1 M
NaNO3.
[00721 FIG. 12
is a graph showing the effect of pH on molybdate sorption on
an embodiment of MPCM, with initial conditions of a concentration of 5.21
mmolit and
temperature 298 K.
100731 FIG. 13
is a schematic diagram showing reaction mechanisms for
sorption of Mo (VI) onto an embodiment of MPCM from aqueous solution,
100741 FIG. 14
is a graph showing equilibrium sorption isotherms for Mo (V1)
uptake on an embodiment of MPCM, showing experimental data (?) correlated with
the
Langmuir isotherm model (solid line) under conditions where the concentration
of Mo(VI) in
solution is in the range of I mmon to 94 mmon, temperature 298 K, pH
100751 FIG. 15a
is a graph showing a breakthrough curve for Mo (V1)
sorption on a bed of MPCM, the inlet influent concentration was 5.21 mmole Mo
(vl).., at
the pH of 3.; FIG. 15b is a graph showing the effect of influent solution pH
on the
breakthrough. curve for Mc (VI) from a column packed with an embodiment of
MPCM, The
inlet influent concentration was 5,21 mmole Mo (VW., with 153,8 mmole NaCIA,
at the pH
of 4 to 7, respectively. For both figures, the bed height of the column was
3,2 cm, the inlet
influent flow rate was I mLmitt.
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10076/ Pia 16 is a graph showing breakthrough curves for pertechriate
from a
column packed with an embodiment of IVIPCI'vl without oxidation which was
loaded with
6.25 mM of Mo (V1)/gram of MPCM. The volume of the column was 2.5 em5, The
inlet
flow rate was 1 rnLi min. The inlet influent concentration was 0,25 mM
pertechnetate /L in
saline (0.9% NaCI) solution.
[00771 FIG. 17 is a graph showing the surface charge of oxidized and
non
-
oxidized MPCM exposed to 1% Mc (VI) in aqueous solution in the presence of IN
NaNO3,.
[0078] FIG, 18 is a graph showing an elution profile for 99"Te from
an
embodiment of MPCM loaded with Mo (VI) spiked with 99Mo,
108791 Fla 19 is a graph showing the relationship between number of
elution(s) and the percentages of '9"rfe and Mo (VI) release from an
embodiment of MPCM
as sorbent.
[00801 FIG. 20 is a flow diagram for a process using a 9Tc/99Mo
generator
systems and a 'IA production using neutrons capture method, using an
embodiment of
MPCM as the sorbent
[0081] FIG. 21 is a graph showing the effect of temperature on
molybdenum
uptake onto tv/PCM-C10, resin under conditions of initial solution
concentration of I% Mc
solution with 25 mivi Na0C1, pH of 3.0, and solid to liquid ratio of 1100 with
a contact time
of 0.5 hour..
[00821 Fla 22 is a graph showing heat of adsorption at different
loading and
temperature (240C to 500C) of the resin of FIG. 21.
100831 FIG. 23 is a graph showing the projected specific activity of
a
proposed MPCM based generator with a column volume of 6- rriL
[00841 FIG. 24 is a graph showing FT1R spectra of chitosan and
another
embodiment of modified chitosan disclosed herein.
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[00851 FIG, 25
is an IR spectra of unirradiated molybdenum loaded MPCM-Z
resin and the molybdenum loaded MPCM-Z resin irradiated at 250 kGy.
[00861 FIG, 26
is an IR spectra of unirradiated molybdenum loaded MPCM-Z
resin and the molybdenum loaded fvIPCN1-Z resin irradiated at 250 kGy
100871 FIG, 27 is a graph illustrating the relationship between
intensity ratios
from C-O-C group (ilwollw.io) and hydroxyl group (133Hiliei2,0) and radiation
doses (kGy).
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[00881 The
methods disclosed herein and the resulting modified chitosan
materials, as well as methods for the use thereof, can be better understood by
reference to the
following examples, which are intended illustrate, not to limit, the invention
or the appended
claims.
100891 Medium
molecular weight chitosan (about 190,000 to about 310,000,
as determined by viscosity data) that has been 75-85% deacetylated was
obtained from
Sigma-Aldrich Chemical Corporation, WI, USA, All chemicals used in the
examples were of
analytical grade,
[00901 The
modified chitosan disclosed herein can be prepared according to
the reactions shown schematically in FIG, 7, by crosslinking with
glutaraldehyde under acidic
conditions at temperature conditions set forth below. While the amount of
glutaraldehyde
used may vary somewhat, it has been found effective to use from about 2 ml to
about 10 ml,
more particularly from about 2 ml to about g ml, even more particularly, about
6 ml, of
glutaraldehyde per 4 g of chitosan. The pH of the crosslinking reaction
between
glutaraldehyde and chitosan may also vary somewhat, but it has been found
effective to use a
pH of between about 0,7 and about 3, more particularly between about 0.7 and
2, even more
particularly, of about I M. The temperature of the cross/inking reaction may
also vary, but is
desirably between about 50 0C and about 80 C, more particularly, around 70 C.
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10091] It is
another aspect of the present disclosure to provide a sorbent for
use in connection with separating isotopes From mixtures. The sorbent
comprises a
microporous material including chitosan which has been crosslinked with
glutaraldehyde in
the presence of a catalyst to a glutaraldehyde concentration of about 2 to
about 4 wt% to
produce a cross-linked chitosan-giuteraldehyde composite matrix. The cross-
linked chitosan-
giuteraldehyde composite matrix is resistant to degradation from exposure to
beta and gamma
radiation and From exposure to acids. The cross-linked chitosan-gluteraldehyde
composite
matrix includes a plurality of nartoparticles, made from a high Z element,
disposed in the
cross-linked chitosan-gluteraidehyde composite matrix and integrated with the
cross-linked
chitosan-gluteraidehyde composite matrix to reduce primary impact of high
radiation flux
and minimize radiolytic effect on said cross-linked chitosan-gluteraidehyde
composite
matrix.
[00921 Without
being bound by theory, it is believed that chemical element
with a high atomic number of protons in the nucleus, the high Z element, with
higher
stopping power will have affinity for certain isotopes can be crosslinked with
MPCM resin
matrix. It is also believed that the radiation tolerance limit and selectivity
of the MPCM resin
for certain isotopes, can be further enhanced by the high Z element
crosslinked MPCM resin
as it will not be limited by the radiolytic driven reaction. Therefore, it is
the inclusion of the
high Z element will reduce the primary impact of high radiation flux and
minimize the
radiolytic effect on to the MPCM's porous critical structure compared to
regular organic
based resin such as MPCM resin.
[0093] The main
objective of addition the high Z element, other than
Molybdenum (Mo), into the cross-linked chitosan-gluteraldehyde composite
matrix is to
protect the structure of the matrix from the Mo-99 related radiolytic impact.
Preferably, the
plurality of nanoparticles is made From the high Z element of Hafnium (HO, Hi
is a
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preferable high Z element for use in connection with the cross-linked chitosan-
glutcraldehyde
composite matrix because Hf has no known toxicity and, therefore, can be
qualified to use in
medical applications. More preferably, Flf is present in the cross-linked
chitosari-
eluteraidehyde composite matrix at a range of between 0./ 5g to 035 g per
grams of the
cross-linked chitosan-gluteraltiehyde composite matrix. It should be
appreciated that the
amount of HI added to the composite matrix directly corresponds to the amount
of activity of
Molybdenum. For example, the composite matrix with lower amount of Hi is
suitable for
lower specific activity, e.g, natural Moõ while the composite matrix with
higher amount of Hf
is suitable for higher activity enriched Mo, it should also be noted that
excess amount of Hi
also reduce resin capacity for molybdenum.
100941 It is
another aspect to provide a method for preparing a radiation-
resistant sorbent. The method includes a First step of combining chitosart
with water in the
presence of an acid to form a claitosan gel. The next step of the method is to
add
glutaraidehyde to the gel to form a semi-solid mass in the presence of
catalyst at 70C, in.
where condensation polymerization of reaction mass occurs. The semi-solid mass
is then
washed to remove unreacted glutaraldehyde and form a washed mass. Next, the
washed mass
is suspended in aqueous base to form a neutralized crosslinked mass. Then, a
plurality of
nanoparticles of a high Z element is disposed on the neutralized crosslinked
mass. It should
be appreciated that the high Z element being used is for the step or disposing
is made from
hafnium (Hi) between 0,15g and 0,35g per grams of the neutralized crosslinked
mass. After
disposing the high Z element the neutralized crosslinked mass including the
plurality of
nanoparticles is dried under vacuum to form the radiation-resistant sorbent.
It should be
appreciated that the high Z element such as hafnium can be integrated in to
the neutralized
crosslinked mass either self-assembles or radiation induced cross-linking
process
23
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1100951 It is
another aspect to provide a method for preparing a plurality of
nanoparticles lbr use in a radiation-resistant sorbento The method includes a
first step of
grinding a salt of a high Z element with a surfactant under an inert
atmosphere. It should be
appreciated that the salt of the high Z element is an aqueous salt that can be
soluble in water
such as Hafnium Chloride of Hir/20681120 The amount of surfactant. used for
making the
nanoparticles ranges between 4 wi.,% to 20 wt,%, The next step of the method
is adding
deionized water of between 5m1 to 10inl during the step of grinding to form a
homogenous
mixture. The deionized water is added to the surfactant and the high Z element
under
continuous grinding. It should be appreciated that, during the step of adding
the deionized
water, there is no chemical reaction formed instead the homogenous mixture of
the surfactant
and the high Z element is formed. The next step of the method is to add an
alkaline solution
to the homogenous mixture to nucleate and grow the nanoparticles. It should be
appreciated
the addition of the alkaline solution to the homogenous mixture of the
surfactant and the salt
of a high Z element can be conducted under sonication to obtain a
hornoeeriously dispersed
solution. Preferably, the alkaline solution added to the homogenous mixture is
selected from
NaOH or WWII. To avoid impurities and possible side reactions, the steps of
grinding,
adding the deionized water, and adding the alkaline solution are conducted hi
an inert
atmosphere, e.g, under Nitrogen. The growth of the nanoparticles can be
further facilitated
with the addition of excess amount of ethanol in the final solution obtain a
uniform
intermediate stage of the nanoparticles. The precipitates, e.g. the
intermediate stage of
Hafnium oxide nanoparticles, are then sonicated and washed thoroughly with
ethanol and
deionized water to remove the surfactant and impurities, respectively. In this
step, the mass of
the hafnium nanoparticles are mixed with chitosan gel before adding
glutaraldehyde in the
final step of MPCivi preparation process. By this way, the hafnium
nanoparticles can be
24
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deposited onto the MPCM resin matrix and the MPCM resin matrix can be dried
under
vacuum and at 120 C for 12 hours.
EXAMPLE!
IN961 The
ionic capacity of the chitosan used in this study was in the range of
9 to 19 milliequivalentsig, measured using a standard titrametric method.
About 4 g of
chitosan was added to 300 mL D1 water with 1 mL acetic acid and stirred for 2
hr at 70 C to
form a gel. Approximately 5 mL of fiCl/HNO3 was added into the chitosan gel
and kept
under continuous stirring for another 1 hr at 70 C to assist protonation of
the amino
substituent groups, which is beneficial for the reasons given below.
[00971 The
reaction with gluteraidehyde was performed by drop-wise addition
of approximately 6 mL gluteraldehyde solution, having a concentration of 50%,
to the acidic
chitosan gel under continuous stirring (established based on trial and error,
but generally from
200 rpm to 500 rpm) at 70 C. The final pH of the the mixture was approximately
1,0. The
amount of giuteraldehyde was used in this study was established based on trial
and error
basis. The mixture was kept under continuous vigorous stirring (500 rpm) at 70
C for another
1 hr to obtain semi-solid gel. The amino groups present in the chitosan are
much more
reactive with aldehyde throuth Schiff s reaction than the hydroxyl groups of
chitosan, It was
envisaged that, at 70 C, more free aldehyde groups will be present in the
solution than would
be present at room temperature. /n acidic solution, the protoriation of the
amine group will
inhibit the formation of complexes of aldehyde and amino groups. Moreover,
glutaraldehyde
may undergo aldol condensation and the reaction of hydroxyl groups or chitosan
with free
aldehyde can be catalyzed by acid at 70 C.
100981 The
resulting mass was then thoroughly washed with 2% monoethanol
amine to remove any unreacted gluteraldehyde. The mass was then suspended in
0.1M
NaOH solution for 4 to 6 hours. The cross-linked mass was separated from the
solution and
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washed with 0, / M 1-ICI and then with deionized water (DI) untii the pH of
the effluent
solution was 7. The eross-linked mass was then dried in a vacuum oven
overnight at 70C.
The cross-linked ehitosan-gluteraldehycle composite is referred to as "MPCM"
or
"microporous composite material" herein.
10t)991 The MPCM
was ground using a laboratory jar mill to a particle size in
the range of about 50 to 200 pniõAn amount of these MPCM particles was
suspended
overnight hi aqueous solution having pH 3. The pH of the solution was
maintained using
0.1M HNO3. The suspended MPCM particles were irradiated using 6To as a y
source, The
characterizations of the MPCM sample were performed using SEM, EDS X-ray
microanalysis, FTIR, and XPS spectroscopic analysis,
1001001 A
scanning electron micrograph (SEM) of chitosan and MPCM
material was taken to study the surface morphology and is shown in FIG. I. The
SEM
secondary electron micrograph of the samples were obtained using backscatter
electrons with
an accelerating potential of 10 keV. The SEM micrograph of the cross-section
of chitosan
and N(IPCIVI sample is shown in FIG. In and lb, respectively, It appears from
FIG. In that
chitosan is nonporous, and from FIG. I h the MPCM appears to he microporous in
nature.
[00101] TGA
analysis of the MPCM as-prepared in the lab and pure chitosan,
respectively, was performed using a TGA (TA Instruments) analyzer in a flowing
nitrogen
atmosphere (200 inUmin), For each experiment, approximately 20 ma of MPCM was
heated
to the temperature range from 30 to 600 C in an open alumina crucible at
predetermined
heating rate. TGA measures the amount and rate of weight change of the sample
as it is
heated at a specified rate. Thermogravimetrie analysis of both MPCM and
chitosan was
obtained providing complimentary information about changes in composition as
heating
progresses under controlled conditions. The heating rate in this analysis was
set to 50Ctinin.
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TGA profiles as shown in FIG. 2 indicate a two-step decomposition process for
pure chitosan
while for MPCM it decomposes slowly with the increase in temperature.
[00102]
Thermsgravimetric analysis (TGA) of the chitosan at a heating rate of
"C /min in nitrogen atmosphere (200 mUrnin) indicates that complete
dehydration occurs at
250 C with a weight loss of 8%. The anhydrous chitosan further decomposed in
the second
step with a weight loss of 32% at 360 C. It was burned out completely at 600"C
with a further
12% loss of weight,. The remaining 48% is the burnt residue of the chitosan at
600C.
1001031 In case
of MPCM, The complete dehydration occurs at 2300C with a
weight loss of 12%. The anhydrous MPCM burned out completely at 6000C with a
weight
loss of 36%. The remaining 52% is the burnt residue of MPCM at 600 C. It may
be noted
that the combustion product of MPCM is 4% less compared to chitosan, which
indicates that
MPCM contains 4% of crosslinking agent, such as glutaraldehyde, that was
burned out
completely in this heating range.
/001041 The
swelling behavior and acid tolerance of the MPCM material were
also evaluated. The swelling behavior of MPCM was performed by immersing it in
deionized water and saline solution using a process described by Yazdani-
Pedram et al,
"Synthesis and unusual swelling behavior of combined cationic/non-ionic
hydrogels based on
chitosan," Marromol. Biosei., 3, 577-581 (2003).
[00105j Swelling
behaviour of chitosan was also studied with deionized water
and saline solution.
[001061 The
swelling ratio of the chitosan and MPCM was calculated using the
following equation:
Swelling ratio (%) [(V, V)Nd] x100, 1
where V, is the volume of swollen MPCM and Vd is the volume of dry sample. In
deionized
water it was observed that the chitosan swelled by approximately 105% of its
original volume
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at 24 hours of equilibrium time. MPCM shows very fast swellina behavior
reaching
approximateiy 200% increase within five minutes and reaching equilibrium at 24
hours. The
swelling studies with &ionized water were performed within the pH range of 3
to 6. At.
equilibrium, the maximum volume of the MPCM was almost 219% more than its dry
volume.
[001071 Similar swelling behavior of MPCM was also observed for
saline.
(0.9% NaC1) solution. At equilibrium, the MPCM volume increases up to 223% of
its
original dry volume in saline solution. The results of the swelling studies
indicate that the
hydrophilicity of the MPCM is greater than chitosan. It is reported that the
swelling behavior
of chitosan hydrogel depends on the ionisable groups that are present within
the gel structure.
See Ray ct al,, Development and Characterization of Chitosan Based Polymeric
Hydrogel
Membranes, Designed Monomers & Polymers, Vol. 13, 3, 193-206 (2010), Due to
protonation of ¨NH2 groups of MPCM in the solution pH range of 3 to 6, the
rapid swelling
behavior of MPCM in deionized water can be attributed to high repulsion of ---
NH3+ groups.
In saline solution, at pH higher than 6, the carboxylic acid groups become
ionized and the
electrostatic repulsive forces between the charge sites (COO-) cause
increasing in swelling,
See Yazda.ni-Pedrarn et al,, supra; Radhakumari et al,, Biopolymer composite
of Chitosari
and Methyl Methaerylate for Medical Applications," Trends Biornater..Artif,
Organs, 18, 2,
(2005); Feiinto et al., The swelling behavior of chitosan hydrogel membranes
obtained by
UV- and 7-radiation," Nuclear instruments and Methods in Physics Research B,
265, 418-424
(,2007).
IOW 081 The MPCM sample was submerged in different concentrations of
HNO3, and 1+2,SO4 acid for 24 hours. Chitosan tends to form a gel in acidic
media making it
unsuitable for its use in an adsorption column for separation of metal ions
from aqueous
solutions. One of the main objectives of this study was to make a chitosan-
based acid
resistant material while exposing more ---NR-2 groups, which is the active
metal binding site
.2
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for chitosan. Table 1 shows the results for the acid tolerance capacity of
MPCM. It was
observed that MPCM material shows better FIC1 tolerance capacity than it does
tolerance for
1.-1NO3 and 112SO4. The physical size and shape of MPCM did not show any
significant
change up to 12M HCI, 12M 112SO4 and 3,9 M HNO3 solution but the MPCM appeared
to be
dissolved completely in 7,8 M HNO3 solution, it is evident that the MPCM is
more acid
resistant compared to chitosan.
Table 1 Effect of different concentrations of acid on the physical properties
of material
Sample HC1 11,SO4 HN 0,3
Strength Strength of Sulution Strength of Solution
of
solgtien
18 /2 9 7 I 5 3 15.6113.3 H1,7 --
7.8 3;9
MM MMMM M M M M M
Chitosan x ................ x x x x x x x
MPCM xv x \
t
not,dissolved
x tends to form gel or completely dissolve
(00109/ Figure 3
shows the XR.D pattern for pure chitosan and MPCM beads.
The chitosan sample showed a diffraction peak near 20, indicative of the
relatively regular
crystal lattices (1/0, 040) of chitosan. See Wan et al.., "Biodegradable
Polylactide/Chitosari
Blend Membrane.:," Biorriacromolecules 7(4): 1362-1372 (2006). The peak
observed for
MPCM is appeared to he broadened suggesting that the MPCM sample is amorphous
in
nature. It also indicates that chitosan and gititaraldehyde formed a complex
in the presence of
acid; therefore the crystalline structure of the chitosan was disrupted by the
chemical bonding
between chitosan and glutaraldehyde.
/01f1101 Fourier
Transformed infrared spectra ompo of the MPCM sample
prepared above were examined on a BRUKER FTIR spectrometer equipped with a
broad-
band, 142 cooled mercury-cadmium-telluride (MCI) detector and a KC1 beam
splitter. FT1R
spectra were collected in absorbance mode with 8 cm-1 resolution using 128
scans ranged
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from 400 to 4000 em The
intermolecular interactions between chitosan and
gluteraldelayde in the presence of fiCl acid are reflected by changes in the
characteristics of
IR peaks. FIG, 4 shows the comparison or R spectra of chitosan with MPCM . In
the region
of 2900 ein'i to 3500 cm-' of the spectrum, chitosan and MPCM exhibited peaks
at 3498 cm-1
and 2950 earl, respectively, corresponding to the stretching 0-H and N-H
groups and C-H
stretching vibration in CH, and --C1+,. The peaks at 1350 to 1450 ern indicate
alkane C-H
bending.
1001111 The
complicated nature of absorption spectrum in the 1650-1500 cm-4
region suggests that aromatic ring bands and double-bond (0C) vibrations
overlap the CO
stretching vibration bands and OH beading vibration bands. The peaks expected
in this
region of IR spectra include protonateci amine (-NH3 amine (-
NH), and carbonyl (-
CONVIR) band. FIG. 4 shows a peak at 1600 ere with a shoulder like peak
centered at
around 1570 cm1 and 1670 cm represent ¨N112 and amide I, respectively for
chitosan.
However, the presence of a comparatively sharper peak at 1590 ere in MPCM than
the peak
observed for chitosan suggests the presence of NH3' band in the MPCM sample.
1001121 The XPS
analysis of chitosan and the MPCM sample prepared above
was performed to gain a better understanding of intermolecular interaction
between c.hitosan
and gititeraldehyde. In the XPS analysis, a survey scan was used to ensure
that the energy
range was suitable to detect all the elements, The XPS data were obtained
using a KRATOS
model AXIS 165 XPS spectrometer with monochromatic Mg X-rays (1p,m-1253.6 eV)õ
which
were used as the excitation source at a power of 240W. The spectrometer was
equipped with
an eight-channel hemispherical detector, and the pass energy of 5-160 eV was
used during
the analysis of the samples. Each sample was exposed to X-rays for the same
period of time
and intensity, The XPS system was calibrated using peaks of UO2(4f712), whose
binding
energy was 379,2 eV. A 0' probe angle was used for analysis of the samples,
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[001131 FIG. 5
shows the peak positions of C is, 0 is, and N Is obtained by
the survey scan of chitosan and the MPCM sample prepared above, respectively,
FIG. 6
shows the peak positions in detail for C Is, 0 Is, and N Is present in
chitosan and MPCM.
The C-Is peak observed showed two peaks on deconvolution, one for C-N at 2843
eV and
the other one for C-C at 283,5 eV (FIG, 6a). In the MPCM sample, the C-Cs peak
appears to
be folded and shifted slightly, whereas the C-N peak showed higher intensity
compared to
chitosan (FIG, 6a), The peaks for oxygen containing groups (0 Is) were found
at 530.5 eV
and 531,1 eV for chitosan and PAPUA, respectively (Figure 6b).
l00114i Compared
with the C Is and 01 s peaks of MPCM, it was observed that
the C-C peak of chitosan at 283.5 eV folded and Ols peak shifted from 530.5 eV
to 53 LI eV
due to cross-linking reaction with glutaraldehyde. This suggests that the 0 s
component may
be single bonded corresponding to ¨OH or C-0 moiety in the structure for
different surface
oxygen containing functional groups, See Wen et al,õ "Copper-based nanowire
materials:
Templated Syntheses, Characterizations, and Applications," Langmuir, 21, 10,
4729-4737
(2005), Chemical shifts are considered significant when they exceed 0,5eV. See
Hasan et
al., "Adsorption of divalent cadmium from aqueous solutions onto chitosan-
coated perlite
beads," Ind. Eng. Chem. Res., 45, 5066-5077 (2006). As a result, shifting of
the 0 is peak in
MPCM sample also indicates that the glittaraldehyde reacted with oxygen-
containing
functional groups of chitosan. The XPS data suggests that the chemical binding
of
glutaraldehyde occurs with the --CH2OH or OH groups on the chitosan structure
which is also
in agreement with the data obtained from FTIR analysis (FIG, 4).
100115] The N is
peak for chitosan was at 397.5 eV (FWHM 1,87) for nitrogen
in the --NH:z group of chitosan (FIG. 5c); for the MPCM the N Is peak appeared
at 397,7 eV.
One of the objectives for investigating the N 15 peak was to identify whether
amine groups,
which are active metal binding sites for chitosari, were involved in cross-
linking reactions
31.
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with glutaraldehyde. FIG. 6c shows a strong Nis peak for MPCM at 3973 eV,
which can be
assigned to -NI-12 groups, suggesting that the amine groups of chitosan were
not affected by
the cross-linking reaction with glutaraldehyde. This is also evident from the
FTIR spectra
(FIG, 4),
1001161 Table 2
shows the XPS data for surface elemental analysis of the
sample of MPCM, as determined from the peak area, after correcting for the
experimentally
determined sensitivity factor ( 5%). It has been found that by preparing
porous chitosan
based material, in this case the embodiment of MPCM described above, results
in the
exposure of more NI-12 groups on the surface of the material. The nitrogen
concentration, as
determined from the N Is peak on the sample of MPCM, was almost twice that
calculated for
chitosan (Table 2), It is believed that the nitrogen content in the MPCM came
entirely from
chitosan. The high nitrogen content in the MPCM, as shown in the Table 2, was
due to the
microporous nature of the MPCM which makes more amine groups available on the
surface
than is the case in the nonporous chitosan, This is also consistent with the
results reported by
Hasari et alõ supra, obtained by dispersing chitosan onto perlite, The changes
in peak
intensity of C is and binding energy of 0 Is peaks at 53L0 eV of the MPCM
sample
compared to chitosan are believed to be due to the reaction with
giutaraldehyde in presence
of acid as a catalyst,
.32
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Table 2: Absolute Binding Energy (BE) for the elements present in the ehitosan
and MPCM
obtained from .X-ray Photoelectron Spectroscopy (XPS) Analysis,
Sample C s N Is 1
0 Is
BE Atomic BE Atomic BE Atomic
(eV) weight (eV) weight (eV) weight
s: = -
Ch itosan 283,5 57,61 397,5 3,91 530,5 28.11
MPCM 284 7209. 397,7 6,85 531,1 1929.
MPCM4* I 283,5 72.25 397,5 5.49 531,1 19.72
* MPCM-I sample after irradiation at 50,000 krad using 6 Co y-source.
(001171 The
energy dispersive spectroscopy (EDS) X-ray microanalysis was
performed on the same MPCM sample as was used for the SErvl micrograph, The
EDS
microanalysis was used for elemental analysis of MPCM (FIG. 7), The peaks for
carbon,
oxygen, and nitrogen are shown at 0,3 keV, 0,36, and 0,5 keV, respectively,
which are the
main components of chitosan (HG. 7a, 7b), Due to the reaction with
glutaraldehyde, the
intensity of the carbon peak for MPCM increases; whereas, the intensity of the
oxygen peak
decreases in comparison to chitosan (FIG. 7b). FIG, 7b also shows that the
nitrogen peak
present in the MPCM sample shifted, due to protonation of amine groups (-N112)
compared to
the nitrogen peak in chitosan. Based on the FTIR, EDS, and XPS analysis, and
without
wishing to be bound by theory, the possible reaction mechanisms of
glutaraldehyde with the
¨OH groups of chitosan through the formation of acetal bonds are given in FIG.
8.
l00118I The MPCM
sample described above was evaluated for radiation
stability by irradiation with a 60Co source. The IR spectra of the MPCM
composite sample
before and after being irradiated using a6 Co source are shown in FIG, 9. The
results in FIG,
9 shows that the MPCM sample suspended in water at pH 3.0 can tolerate -y-
radiation to about
50,000 krad without losing a substantial percentages of its identity.
1001191 FIG. 7c
shows EDS spectra of chitosan and MPCM particles before
and after irradiation at 50,000 krad with a 6 Co source. FIG, 7c indicates
that the intensity of
carbon, oxygen, and nitrogen peaks did not change substantially after
irradiation of the
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sample. FIG. 10 shows the peak positions of carbon, oxygen, and nitrogen
obtained by the
XPS analysis of the MPCM sample before and after irradiation. it was observed
that the
magnitude of total C Is peak binding energy changed after irradiation as shown
in Table 2.
The C Is peak for the MPCM sample was 283.5 eV, while for the MPCM sample
after
irradiation two peaks were observed at 283.5 and 284,5 eV (FIG. 10a). The Nis
peak present
in the MPCM sample after irradiation around 397,5 eV can be assigned to NH-2
groups in the
MPCM structure, No change was observed for 0-1s peak of the irradiated MPCM
sample.
The magnitude of the binding energy shift depends on the concentration of
different atoms, in
particular on the surface of a material. In comparison with the XPS (FIG. 10a-
e), the N Is and
0 Is peak of the MPCM sample did not shift before and after irradiation (Table
2), indicating
that the chemical state of N atoms was not much affected after irradiation.
This is also
reflected in the EDS and FTIR spectra as shown in FIG. 7 and 9.
1001201 The MPCM
sample described above was evaluated for molybdenum
sorption using batch techniques. About 1,0 gram of MPCM adsorbent was
suspended in
100mL solution containing ammonium molybdate in the range of I mmolelL to 94
mmoiel,õ
The initial pH values of solutions were adjusted from 2,0 to 8,0 using either
0.01 M Na011 or
0.1 NI liCl solution. The solutions were then kept in a shaker (160 rpm) Ibr
24 hrs at 298K.
After 24 hrs., the final pH was recorded for each solution and the solutions
were centrifuged
for 5 minutes at 3000 rpm to separate the supernatant from the solution. The
supernatant was
then filtered through a 0.45m membrane filter and the filtrate was analyzed
for
molybdenum removal by an Inductively Coupled Plasma (1CP) (Agilent 7700X) that
is
equipped with mass spectroscopy for molybdenum detection. The adsorption
isotherm was
obtained by varying the initial concentration of molybdenum in the solution.
The amount of
molybdenum adsorbed per unit mass of adsorbent (ep) was calculated using the
equation,
q,
34.
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where Ci and Ce represent initial and equilibrium concentrations in mg11.õ
respectively, V is
the volume of the solution in liters (1), and Al is the mass of the adsorbent
in gram (g).
[001211 The
surface charge of a bead of MPCM sample was determined by a
standard potentiometric titration method in the presence of a symmetric
electrolyte, sodium
nitrate, as per Hasan et alõ supra. The magnitude and sign of the surface
charge was
measured with respect to the point of zero charge (IPZC"). The pH at which the
net surface
charge of the solid is zero at all electrolyte concentrations is termed as the
point of zero
charge. The pH of the PZC for a given surface depends on the relative basic
and acidic
properties of the solid and allows an estimation of the net uptake of 1-1+ and
OH- ions from the
solution. The results are shown in FIG. I I.
[00122j The PZC
value of the sample of MPCM prepared as described above
was found to be 8.8, which was similar to that reported by Hasan et al.,
supra, for chitosan
coated perlite bead. However, it is reported that the PZC value of pure
chitosan is within the
pH range of 6.2 to 6.8. See Hasan et al, supra. It is observed from FIG. I I
that a positively
charged surface prevailed at a relatively low pH range. The surface charge of
MPCM was
almost zero in the pH range of 7.5 to 8.8. The protonation or the NIPCM.
sharply increased at
the pH range of 7.5 to 2.5 making the surface positive. At pH below 2.5, the
difference
between the initial pH and the pH after the equilibration time was not
significant, suggesting
complete protonation of amine (-N1112) groups present in MPCM. At higher pH,
7,5 to 8,8, the
surface charge of the MPCM slowly decreased, indicating slow protonation of
MPCM. In
ease or chitosan, the extent of protonation is reported to be as high as 97%
at a pH of 4,3.
However, it decreases as the pH increased, The extent of protonation of
chitosan surface is
reported to be 91%, 50%, and 9% at pH 53, 63, and 7.3, respectively. See Hasan
et al_ "
Dispersion of chitosan on perlite for enhancement of copper (II) adsorption
capacity" Journal
of Hazardous Materials, 52 2, 826-837, 2008.
35.
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1881231 Without
wishing to be bound by theory, it is believed that the PLC
value of 8,8 and the behavior of the surface charge of the MPCM is due to the
modification
of chitosan when cross-linked with glutaraldehyde in the presence of acid as a
catalyst, which
makes it amphoteric in nature in the pH range of 7.5 to 8.8.
The effect of pH on adsorption of molybdenum by MPCM was studied
by varying the pH of the solution between 2 and 8 (FIG. 12). The pH of
molybdenum
solutions were first adjusted between 2 and 8 using either 0,1N H,S0.4 or 0,IM
Na0H, and
then MPCM was addedõAs the adsorption progressed, the pH of the solution
increased
slowly. No attempt was made to maintain a constant pH of the solution during
the course of
the experiment. The amount of molybdenum uptake at the equilibrium solution
concentration
is shown for each different initial pH of the solution in FIG, 12, The uptake
of molybdenum
by MPCM increased as the pH increased from 2 to 4, Although a maximum uptake
was noted
at a pH of 3, as the pH of the solution increased above 6, the uptake of
molybdenum onto
MPCM started to decrease. Accordingly, experiments were not conducted at a pH
higher than
the PZC of the MPCM sample.
[001251 In order
to adsorb a metal ion on an adsorbent from a solution the
metal should form an ion in the solution. The types of ions formed in the
solution and the
degree of ionization depends on the solution pH. In the case of MPCM, the main
functional
group responsible rbr metal ion adsorption is the amine (-N112) group.
Depending on the
solution pH, these amine groups can undergo protanation to NH 3+ or (N1-12-
H30)+, and the
rate of protonation will depend on the solution pH. Therefore, the surface
charge on the
MPCM will determine the type of bond formed between the metal ion and the
adsorbent
surface. Depending on the solution pH, molybdenum in an aqueous solution can
be
hydrolyzed with the formation of various species. At relatively high and low
pH values both
the Mo04'.. and various isopolyanions (mainly )
predominate. The AloO:t.' anion
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undergoes formation of many different poiyanions in acidic solutions. See
G'uiba.1 et al,
"Molybdenum Sorption by Cross-linked Chitosa Beads: Dynamic Studies", Water
Environment Research, 71, 1, 10-17, 1999; Mercd et al, "Molybdenum (VI) Binded
to
Hurnic and Nitrohtimic Add Models in Aqueous Solutions, Salicylic, 3-
Nitrosaliculic, 5-
Nitrosalicylic and 3,5 Dinitrosalicylic Adds, Part 2" 1 Braz. Chem, Soc., 17,
3, 482-490,
2006, It is reported that even if the polyanion is present in the solution the
adsorption still
occurs via MoO, formation. See Jezlorowski et al., "Raman and Ultraviolet
Spectroscopic
Characterization of Molybdena on Alumina" The Journal od Physical Chemistry,
83,9, 1166-
173, 1979; El Shi.lfei et al., "Association of Molybdenum Ionic Species with
Alumina
Surface," Journal of Colloid and Interface Science, 228, 105-113, 2000. The
degradation of
polyanions in the solution occurs due to an increased local pH close to the
adsorbent surface.
[00126) As noted
above, it was observed that the MPCM had a maximum
adsorption capacity at a pH of around 3 from a solution of molybdenum ions.
Without
wishing to be bound by theory, it is believed that the amine group of the MPCM
has a lone
pair of electrons from nitrogen, which primarily act as an active site for the
formation of a
complex with a meta/ ion. As mentioned earlier, at lower pH values, the amine
group of
MPCM undergoes protonation, forming NHf leading to an increased electrostatic
attraction
between NW" and sorbate anion. Since the surface of MPCM exhibits positive
charge in the
pH range of 2,5 to 7.5, the anionic molybdenum (Mo (VI)) is presumably the
major species
being adsorbed by Couiombic interactions. As mentioned earlier, the pH of the
solution was
Ibund to increase after adsorption, which can be attributed to the 114. ions
released from the
surface of the MPCM as the result of sorption of the inolybdenum-containing
anions from
solution, la the case of MPCM, the protonation of NI-12 groups occurs at a
rather low pH
range. The fact that pH of the solution increased as the adsorption progressed
suggests that
Mo (VI) fOrmed a covalent bond with a NH: group,
3.1
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1001271 As the
equilibrium pH increased from lower pH toward the pH at the
PZC (plinc), the decreased percentage removal of Mo (VI) was attributed to the
decreasing
electrostatic attraction between the surface of MPCM and anionic Mo (VI)
species. It may be
noted that the PZC of MPCM is found to be shifted towards 4.5 in the presence
of
molybdenum ions, as compared to the PZC of MPCM without said ions (FIG. I).
The shift
of PZC of MPCM towards lower pH indicates strong specific adsorption and inner-
sphere
surface complexation occurs due to molybdenum adsorption. Similar findings
were reported
by with the adsorption of molybdenum onto gibbsite. See Goldberg, S.
"Competitive
Adsorption of Molybdenum in the Presence of Phosphorus or Sulfur on Gibbsite,"
Soil
Science, 175, 3, 105-110, 2010. Based on the surface charge analysis and pH
studies, the
reaction mechanisms that are occurs between the surface of MPCM and molybdenum
species
in solution are given in FIG. 13.
10011.281 The
equilibrium adsorption isotherm of molybdenum uptake on
MPCM was determined at 298K temperature in the concentration range of 1
tnmolelL to 94
rnmoleit. As mentioned in the previous section, the maximum adsorption
capacity of
molybdenum on MPCM occurs at a pH of 3. Therefore, the equilibrium isotherm
experiments
were carried out at a pH of 3, if not stated otherwise. The concentration
profiles during
molybdenum uptake by the MPCM from various concentrations of the solution
shows that
approximately 60% of molybdenum was adsorbed during the first 4 hears of an
experimental
run, The equilibrium was attained monotonically at 24 hours in most of the
experimental
runs.
[001291 The MPCM
material contains amino groups that are available for
characteristic coordination bonding with metal ions. Adsorption of metal ion,
when pH
dependent, may be described by the following one-site Langmuir equation, The
effect of pH
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was incorporated by introducing a parameter "a" that is dependent on pH of the
solution. The
expression is given below:
-SH 4- -S + S: surface concentration 3
-S + M km 1VL metal ion 4
maximum adsorption amount of metal ions (rnme.leg)
K
e _______________
H +[H1 6
where q is the adsorption capacity corresponding to meta/ ion concentration
[M], qm is the
Maximum adsorbed amount of molybdenum ions (mitrio4), [H] the hydrogen ion
concentration, Ku and Km are equilibrium concentration. Equation 5 was used to
correlate the
adsorption capacity of the MPCM. The equilibrium data for molybdenum could be
correlated
with the Langmuir equation within 5% of experimental value. The constants of
Equation 5
are obtained by non-linear regression of the experimental data and are given
in Table 3. It
was noted that Equation 5 represented the adsorption behavior of molybdenum on
the MPCM
adequately (Figure 14), The adsorption isotherm data obtained at pH 3 showed
Type I
behavior.
1001301 This
suggests a monolayer adsorption of molybdenum on MPCM.
Table 3 shows the maximum adsorption capacity of MPCM for Mo (VI), using
Langmuir
Equation (Equation 5). It was noted that the adsorption capacity of MPCM for
molybdenum
is approximately ¨6.25 mmol Moig of MPCM at 298K when the equilibrium
concentration of
Ivlo(V1) in the solution was 54./ mmol/L, and the initial pH of the solution
was 3.0 (FIG. 14).
The NH?, groups of MPCM are the main active sites for molybdenum adsorption.
As ran be
seen from the FIG, 13, two NH-, groups will be necessary for the adsorption of
one
molybdenum ion, Other surface sites such as CH-,01-1 or OH groups of MPCM
might have
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been involved in adsorbing molybdenum at the soiution pH of 3. The adsorption
capacity of
MPCM that was irradiated at 50,000 krad was also performed for molybdenum
uptake from
aqueous solution. ft was observed that the adsorption capacity of irradiated
MPCM did not
change substantially as shown in Table 3,
Table 3. Estimated parameters for the Langmuir model
Sample Metaf ion pH al KgP5 Maximum uptake
uptake capacity
(using Equation 5)
(mmoilu)
MPCM Mo(V1) 3 0.15 0.4708 7.34
*MPCM-I Mo(Vn 3 025 0.2194 6.54
MFCM-1: Sample after irradiation at 50,000 krad Co y-source.
1001311 A column was used to study the adsorption of Mo (VI) with or
without
the presence of ions in the solution under dynamic conditions. Approximately
1,125 gram of
MPCM was used to make a 2.5 crn3 column with 0.5 ern inner diameter and 3.2
ern height. A
flow rate oil mUminute was used during a run. The run was continued for 1500
minutes,
and samples at the bed out let were collected at a regular time intervals. The
bed becomes
saturated during this time period, as indicated by the outlet Nilo (V1)
concentration, When the
inlet concentration was 5.21 mmole Mo (VOIL at pH 3 and the flow rate was I
triLi minute
through the column, molybdenum broke through the column after 320 bed volumes
(FIG.
/5a), Complete saturation of the column occurred after 500 bed volumes.
Breakthrough
curves were also obtained from a mixed solution containing 5.21 mmole Mo (VI)
./ L and
153,8 miVINaCil L at pH 6,86 and 4,0, respectively (Figure 15 b). In both
cases, the solution
was passed through a similar size of column as mentioned earlier maintaining
same bed
height and flow rate. It was observed that column broke through quickly at 42
bed volume for
the mixed solution with pH 6.86 however approximately 125 bed volumes were
required to
break through the column for the mixed solution with pH 4,0. It is important
to note that the
break through time for molybdenum solution with 153.8 mM NaCV L can be
delayed,
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through the use of larger quantity of MPCM adsorbent and a longer column. The
objective
was to investigate the effect of inlet mixed solution pH on the breakthrough
characteristic of
Mo (Vi) from the column, therefore, no attempt were made to determine the bed
length to
prolong the breakthrough time for mixed solution.
I001321 The long
lived technetium (99Tc) was used to evaluate the performance
of MPCM to adsorb technetium with and without the presence of other ions from
an aqueous
solution in the pH range of 3 to I I. Technetium is chemically inert and has
multiple oxidation
states ranging from I to VII. The most dominant species of technetium that is
found in
aqueous waste streams is pertechnetate (Tc04-) See Gia et al., Development of
Novel
Bifunctional Anion-Exchange Resin with Improved Selectivity for Perteehnetate
sorption
from contaminated groundwater, Environ, Sci, Technol, 34, 1075-l080, 2000, The
adsorption of pertechnetate Tc-Q4 ) from an aqueous solutions on MPCM was
studied under
batch equilibrium conditions following a process outlined elsewhere. The
effect of pH on
technetium adsorption onto MPCM was evaluated over the pH range or 3 to I I
using a
solution containing of 0,H umole technetium IL with and without the presence
of 0,9%
NaCI, respectively, While studying the effect of pH on the adsorption
capacity, the initial pH
of the solutions was adjusted to a desired value by adding either 0.1 M HCI or
0,1 M NaOH
The pH of the solution was not controlled during the adsorption process.
Following the
adsorption experiments, the solutions were filtered and the activity of 99-Ic
in the filtrate,
which was collected hi a vial at a predetermined time, was evaluated using a
liquid-
scintillation counter (Packard Tricarb 2900TR), The amount of technetium
adsorbed onto
MPCM was determined following the Equation 2.
[001331 Table 4
shows that the adsorption of technetium onto MPCM is pH
independent in the solution pH range of 3 to II. It was observed that
approximately 95% of I
1./M technetium/I of solution was adsorbed onto MPCM in the pH range of 3 to I
I, whereas
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the technetium removal was reduced to 56% in present of 0,9% NaCI over the pH
range of 3
to I L As it was mentioned earlier, MPCM shows positive charge in the pH range
of 3 to 7,5,
FT1R spectrum of MPCM confirms the presence of --N1-11., CHOW, and Ch1,011
groups on
MPCM surface (FIG. 4), It was assumed that the positive charge occurs due to
protonation of
= the surface sites of MPCM in the pH range of 3 to 7,5 and technetium
undergoes covalent
bonding with the positive surface sites of MPCM. In the case of 0.9% NaCI in
solution, the
adsorption capacity of MPCM for technetium was reduced as the pertechnetate
ions had to
compete with the chloride ions in solution. Moreover, the uptake of technetium
in the pH
range of 9 to 11 in the presence of 0.9% NaCI solution may correspond to an
ion-exchange
reaction that occurs at this pH range. The result shown in Table 4 confirms
that MPCM has
strong affinity for perteehm.qate ion from aqueous solutions.
Table 4. Adsorption of technetium on to MPCM at different pH
; 99Tc Initial Amount Amount % uptake of 99-le on to MPCM at
solution concentration of of of different pH
prepared 99Te in the MPCM solution
ustrw solution
oH
3 4 6 8 9 10 11
De- 0.11 0.1 0.03 9 95 85 85 90 90 90
ionized i, 5 % % % % % %
water
........................................ +
0.9% 0,11 0,1 0.03 5 55 55 56 51 52 51
NaCI 6 % % % % %
solution
[00134] MPCM
was also used to adsorb Mo (VI) and To(VII) simultaneously
from a mixed solution containing I irimole of Mcp(Vln and 0.11urnole of
pertechnetateit
with or without the presence of 0,9% NaCI, MPCM was found to adsorb molybdenum
and
technetium simultaneously from the solution at solution pH 3. It was observed
that
approximately 95% of 0,1 I prnole pertechnetate was adsorbed onto MPCM
surface, whereas
99% of I mmole molybdenum was adsorbed from the mixed solution. In the
presence of
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molybdenum (Mo0) in the solution, pertechnetate (Te.-0,-) had to compete for
the positive
surface sites of MPCM. In another attempt, the adsorption of technetium onto
MPCM was
studied from a mixed solution containing 153.8 rnmole NaCl/L, I mmole Mo (VI)
/L of and
0.11mmole pertechnetate/L. Table 5 shows that molybdenum (,1,20-) was adsorbed
preferentially on to the MPCM surface, whereas the adsorption of pertechnetate
(7c0;) was
reduced to 55% of 0.11pmole technetium/I, in the mixed solution. It is assumed
that in the
presence of 0.9% NaC1, the sorption of pertechnetate (7-c0,1) onto MPCM
surface was
reduced due to the competition for surface sites with chloride ions at
solution pH 3. In
another attempt, a column with I cm inner diameter was used to study the
pertechnetate
adsorption onto MPCM. The column was prepared with MPCM that was loaded
initially with
Mo (111). Batch equilibrium process was used to adsorb 6.25 mmole Mc (VI)/ g
MPCM at
298 K when the equilibrium concentration of Mo (VI) in the solution was 54
mmole/L and
the initial pH of the solution was 3Ø Approximately L125 gram of Mo (VI)
loaded MPCM
was used to prepare a 2.5 cm3 bed. A saline (0,9% NaCI) solution spiked with
0.25 mM
pertechnetate/L was passed through the column using a peristaltic pump at a
flow rate of l
mUmin during the run.
Table 5. Adsorption of pertechnetate and molybdenum on to MPCM from a mixed
solution
Experi- Amount l Amount Concentration of pertechnetate, % uptake
ment of l of molybdenum, and sodium chloride
i
MPCM solution in the mixed solution
g I-, Tr0.- Mo0'..- NaC1 Mo(V1 Tc(V1I)
i
l (pM/L) (mM/L) (mMst) ) 0-.0
______________ i (%);
_ .............................................................
1 0,1 0,03 0,1 / __ 1,0 0,0 99 95 1
2 i .. 0.1 . 0.03 ____ 0.11 __ 0,0 153,8 i - 55
-------i
3 .... 0,1 0,03 i 0.11 __ 1.0 153,8 99 56 ___
0.1 ... 0.03 i 0,1 l ¨ 1,0 153,8 98.0 56 ,
1 ,
[001351 FIG, 16 shows that the pertechnetate anion has affinity
towards
available surface sites of MPCM in the presence of molybdenum (Mo0:-:--)
anion. It was
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observed that at 10 bed volumes, approximately 15% of the inlet concentration
of
pertechnetate was eluted with saline (0.9% NaC1) solution* It may
be noted that
approximately 60% of the inlet pertechnetate concentration was obtained in the
duent that
was collected at 20 bed volumes (FIG, 15), The column reaches saturation
fairly quickly for
technetium while an additional 40 bed-volume of technetium spiked saline
solution was
passed through the column. After the column reached its saturation for
technetium, more than
95% of the technetium fed to the column was collected at the column outlet as
eluent. The
objective of this study was to investigate the maximum amount of pertechnetate
(reO4. )
uptake onto MPCM loaded with 6.25 mM of Nilo (VI)/ gram of MPCM. No attempts
were
made to determine the bed length to reduce the pertechnetate release from the
Mo (VI) loaded
MPCM bed.
[00136] Although
batch and column studies show that MPCM exhibited
excellent adsorption capacity for Tc(V11), its removal from the bed was
challenging. A
technetium loaded MPCM bed was prepared in a column to study the desorption of
technetium from the MPCM sample, The adsorption or technetium onto MPCM was
conducted under batch equilibrium conditions. It was observed that
approximately 0,12uM of
99Tc was adsorbed per gram of MPCM from a 99-fc concentration of 0,480411,
solution at
298K temperature. For 'fc desorption studies, about 1,125 gram of MPCM
containing
0.12pM of 'Te / gram of MPCM was used to prepare the column. Pertechnetate is
soluble in
water; therefore, deionized water was used to regenerate technetium from the
column* It was
observed that only 1% of technetium was desorbed from the MPCM bed using 10
bed
volumes of water. Preliminary studies show that complete recovery of
technetium from the
MPCM is challenging even using when different concentrations of NaCI solution.
It was
observed that approximately 50 bed volumes of 1.5% NaC1 was required to
regenerate 10%
of99Tc from the column. Similar amounts of low concentration acid solutions (<
1M) of HO,
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H2SO4. and HNO3, were also used, without any significant regeneration. In
another attempt,
the MPCM sorbent was oxidized with different concentrations of potassium
permanganate or
hydrogen peroxide, to study the effect of oxidation on adsorption/desorption
of technetium on
to the oxidized MPCM sorbent.
EXAMPLE 2
I001371 In
another embodiment, MPCM was oxidized with different
concentrations or hydrogen peroxide with or without the presence of transition
metal
catalysts. Temperature was also varied. The oxidation studies of MPCM with
hydrogen
peroxide were performed to determine whether controlled oxidation alone would
improve
technetium recovery from the technetium loaded MPCM. The concentration of
hydrogen
peroxide was varied from 1% to 5%. Batch technique was used to adsorb
technetium onto
oxidized MPCM. The regeneration of technetium from the oxidized MPCM was
conducted
in a column. The column was prepared with 0,12 umole of '9Ici gram of oxidized
MPCM.
The column was regenerated to desorb technetium from the oxidized MPCM using
0,9%
NaC1 solution, It was observed that the recovery of technetium was not as high
as was
desired, since 10 to 17% of available technetium was recovered from the
oxidized MPCM
bed (Table 6). Moreover, the adsorption of Mo (VI) onto peroxide-oxidized MPCM
reduced
to 4,6 rnmoleig compared to 625 mmoleAz adsorbed by non-oxidized MPCM.
Table 6. Desorption 99Tc from oxidized MPCM using 0.9% NaC1 so/Wien
desorption of "Tr from column
pH Peroxide Peroxide of peroxide and their activation
activation by pH activation by by transition metal catalyst
temperature
I at 7tP0
0.05% 0,2% 0.05% 1 0.2% I% 2% 3% 4% 5%
/1,02 H2O, H202 H20, H202 H202 H202 H202 H2O
3 14.5 I 16,8 14.8 14.2
12,1 16,7 13.2 16.8 15.2 12.4 19.1 10.0 12.8
13.2 I5A 12A 14,7
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EXAMPLE 3
1001381 MPCM was
also oxidized using potassium permanganate in solution.
The concentration of potassium permanganate in the solution and the oxidation
time was
determined based on trial and error. The concentrations of potassium
permanganate and the
pH of the solution were varied from 0.1% to 5% and 3 to 11, respectively. The
oxidation
time was varied from 30 minutes to 24 hours. The surface charge analysis of
oxidized and
non-oxidized MPCM loaded with Mo (VI) was also performed to elucidate the
pertechnetate
) adsorption pattern on oxidized MPCM.
[00139/ It was
observed that permanganate solution containing 0.04 mrnole of
Mn A. of solution at the pH range of 3 to 4.5 and 12 hours time period was
sufficient to
oxidize MPCM partially to facilitate maximum uptake of molybdenum and
simultaneous
release of technetium from the MPCM sorbenL The performance of the oxidized
MPCM was
evaluated for molybdenum adsorption from aqueous solutions using batch
technique, it was
noted that oxidized MPCM can adsorb 6õ25 minole of Mo (VDS g of MPCM at 298K
when
the equilibrium concentration Mo (VI) in the solution was 54 mmon at pH 3Ø
[001401 In
another attempt, two separate columns were prepared using oxidized
MPCM and oxidized MPCM that was loaded with 6.25 mmol of Mo(V1)/ g,
respectively. A
0.9% NaCI solution spiked with about 0.11 .trnole Pertechnetate (Tc0;)/L of
solution was
passed through both columns at a 1 mlimin flow rate. It was interesting to
note that
pertechnetate (Tc04-) did not adsorb onto oxidized MPCM with or without hrlo
(VI) loading
and approximately 90% of pertechnetate (Tc0;) in the solution passed through
both types of
columns as an eluent, The results confirm that pertechnetate (Tc0,,-) did not
adsorb onto
both oxidized MPCM and MPCM loaded with Mo (VI). The objective of this work
was to
maximize Mo (V1) uptake and enhance technetium release simultaneously from the
MPCM
surface sites,
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[00141] MPCM
shows great affinity for both Mo (VI) and Tc(Vil) from the
aqueous solution. The surface charge of Mo (VI) loaded MPCM revealed (FIG. II)
that Mo
(VI) was adsorbed onto MPCM through an inner-sphere surface complexation
reaction. It
may be noted that Mo (VI) loaded MPCM exhibited positive charge in the pH
range of 3 to
4,5; therefore, anionic pertechnetate presumably formed covalent bonds with
the available
positive surface sites. Interestingly, the adsorption of pertechnetate on to
MPCM is
approximately 55% from a solution containing 0.9% Naa at the pH range 3 to 8
(Table 4).
Almost 95% of I inmole pertechnetate was adsorbed onto MPCM hi the presence of
I mmole
Mo (VI) in the solution. This confirms that pertechnetate (rc-04-) was
adsorbed onto MPCM
surface sites,
[001421 The
permanganate ion is arnbiphilic in nature. In acidic solution, Mn
(VII) ions of potassium permanganate change to possible intermediate products
such as Mn
(VI), Mn (V), Mn (1V)õ and Mn (III), which are ultimately reduced to Mn (II).
See Dash et
at,, "Oxidation by Permanganate: Synthetic and mechanistic aspect?'
Tetrahedron, 65, 707-
739, 2009. The permanganate (Mn0,....) content in the potassium permanganate
is reported to
be the reactive oxidizing species for acid catalyzed permanganate oxidation of
chitosan. See
Ahmed et al., "Kinetics of Oxidation of Chitosan polysaccharide by
Permanganate Ion in
Aqueous Perchlorate solutions" Journal of Chemical Research, v 2003, n 4, p,
182 183,
2003. In an acidic medium, the possible reactions between the MnO ion and 11+
are as
lot lows:
Mn O' H Mn 04 7
Mn0; 4H- MnO: 21-120 8
9
[001431 Due to
protonation of the ,(11n0,... ion in the acidic solution, the
species can be formed, which is also a powerful oxidant. See Sayyed et al,
"Kinetic
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and Mechanistic Study of Oxidation of Ester by KMn04" international Journal of
ChemTech
Research, v 2, a 1, p 242-.249, 20R) The formation of colloidal MK), is
possible due to the
reaction of MnO with ,fr and depending on the acidity of the solution which
may further
undergo reaction with H to produce Afr in solution. Ahmed et al, 2002 reported
permanganate oxidation of ehitosan as an acid catalyzed reaction that led to
formation of
diketo-acid derivatives of chitosan, See Ahmed et alõ "Kinetics of Oxidation
of Chitosan
polysaccharide by Permanganate Ion in Aqueous Perchlorate solutions" Journal
of Chemical
Research, v 2003, n 4, p, 182 183, 2003.
1001441 In acid
catalyzed permanganate oxidation of MPCM, permanganate
(Y1r047) ion can be considered as the reactive oxidizing agent. The effect of
permanganate
oxidation on MPCM for the adsorption and release of Mo (VI) and Tc (VII),
simultaneously,
from the oxidized MPCM surface was evaluated by the surface charge analysis of
the MPCM
sample. The oxidation of MPCM by potassium permanganate changes its adsorption
selectivity from aqueous solution. FIG, 17 shows the surface charge pattern
for Mo (VI)
loaded MPCM sample with or without oxidization. In the case of non-oxidized
MPCM
sample loaded with Mo (VI), the protonation of the surface appeared to be
increased
gradually at the pH range of 4,5 to 3. Therefore, at this pH range, the
formation of covalent
bonding by pertechnetate with the positive surface sites of Mo loaded MPCM
surface is
possible. At pH < 2,9, the difference between the initial pH and pH after the
equilibration
time for MPCM loaded with tvlo (VI) sample was not significant, suggesting
complete
protonation of the MPCM sample,
[00145! The
surface charge of Mo (VI) loaded oxidized MPCM shows almost
zero charge in the pH range of 3 to 4,5, compared to the Mo (VI) loaded onto
the non
oxidized MPCM sample (FIG. 17). In the acidic pH range from 3 to 4,5, the
surface
functional groups of non-oxidized MPCM show positive charge which may further
undergo
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reaction with MnO during the oxidation reaction. It is assumed that the
manganie ( )
ion entered into the porous matrix of MPCM and partially oxidized the positive
surface
functional groups by donating electrons followed by reduction to Mn2+ ion in
the solution. In
addition, formation of colloidal manganese in the solution was controlled by
controlling the
solution pH in the range of 3 to 4,5, more specifically at pH 4. Moreover the
ratio of
,Nin2' ion to positive surface sites of MPCM favors further adsorption of
Mri2+ onto MPCM
surface. It was observed from the both batch and column studies that
technetium did not
adsorb on to Mo (V1) loaded oxidized MPCM whereas it shows a strong affinity
tbr the Mo
(VI) loaded non-oxidized MPCM sample, This indicates that the lack of a
positive charge on
the Mo (VI) loaded oxidized MPCM surface did not attract technetium to form a
covalent
bond compared with the surface of non-oxidized MPCM loaded with Mo (VI). It is
interesting to note that technetium did not adsorb onto oxidized MPCM whereas
almost 95%
of I mmole solution of technetium was adsorbed onto non-oxidized MPCM. This
confirms
that technetium adsorbed onto the surface of non-oxidized MPCM and was not
adsorbed on
to the oxidized MPCM through covalent bonding.
100146]
Equilibrium batch adsorption studies were carried out by exposing the
oxidized MPCM to 1% Mo(V1) solution that was spiked with 5.0 mL of 99Mo (2
mCilmL),
Initially 1% molybdenum was prepared by dissolving 4,5 mL, of ammonium
hydroxide and
1.5 tz. of MoG.3 in 95 mIL of deionized water. The mixture was kept under
stirring until M003
completely dissolved in solution. A solution containing 5,0 iniL, of 99Mo (2
mei 99Mo1rriL)
was mixed thoroughly with 97,5 mIL of 1% molybdenum solution. The pH of the
spiked
solution was adjusted to 3 using either 0,1N HCI or Na01-1 solution. The final
specific
activity of the Mo (VI) in the solution was 78.12
[001471 About
0.5 gram of the oxidized MPCM was added to a 125 mL plastic
vial containing 50m1L of spiked solution. The solution was then kept on the
shaker (160 rpm)
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for 3 hrs at 25 1 C. Another set of similar experiments was also performed to
duplicate the
data. After 3 hrs, the final pH was recorded for the solution, and the
solution was centrifuged
For 5 minutes at 3000 rpm in order to separate the MPCM from the supernatant
solution, The
MPCM loaded with t4,i10 (VI) was then rinsed with deionized water couple times
to remove
any adhered Mo (VI) from its surface. The MPCM loaded with Mo (VI) and the
supernatant
and rinsed solutions were analyzed for molybdenum uptake using a dose
calibrator, and a
1CP-MS. It was observed that at equilibrium, the oxidized MPCM had a capacity
of 2.47
mmole Wig of MPCM where 1300 uCi of activity are from the spiked 'Mo.
1001481 The
activity for 99Ma and -99 1'Tc was evaluated using both a dose
calibrator and a gamma spectrometer. The dose calibrator (Atomlab 400) is
equipped with a
small lead sample vessel that effectively shielded of "'"Te gammas while
allowing the
majority of "Mo gammas to pass through the shield and into the detector.
Therefore,
readings taken while the sample is contained within the shielded vessel is
assigned solely to
'Mo activity. Readings taken without the shield are the sum of both 'Mo and
99"'Te
activities.
1001491
Following the batch adsorption run, the MPCM loaded with both 'No
and 'Mc was transferred to a column (0,5 cmx 12 cm with
polytetrafluoroethylene (PTFE)
frit at the bottom). Two ends of the column were closed with silicon rubber
septum. The
column was thoroughly rinsed with de-ionized water to remove any molybdenum
solution on
the surface of the MPCM. The rinsed sample was collected from the column using
evacuated
vials. The column was elated with saline (0.9% NaC1) solution after allowing
it maximum
time required to build-up the daughter product 9Tc from the decay of the
remaining '9Mo in
the column. The column was elated with 9 rill, saline solution that was
collected
subsequently in 3 individual evacuated vials of 3 rril, each. The cluate was
obtained from the
column at predetermined time intervals. The eluate from each collection was
analyzed for
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molybdenum and manganese released from the column using quadruple inductively
coupled
plasma mass spectrometry (1CP-MS) with an external calibrator. The activity
related to
perteehnetate or 99Mo was evaluated using dose calibrator and gamma
spectroscopy.
I001501 FIG. 18
shows the elution profile of the column consisting of 0,5 gram
of MPCM loaded with 2A7 inmole of Mo (Vi) /gram of oxidized MPCM where 1300
P,Ci
activity is from adsorbed 99M o. The column started eluting with saline (0.9%
NaC1) solution
on the day after the column was prepared and the elution was continued over
the period of 8
days. A note is that the first set of elution (Elution 1) was perfOrmed at 8
hours after the
column was prepared in order to .verify the desorption behavior of "'rift from
the MPCM
column, The rest of the elutioris, number 2 to 8, were performed at 24 hours
intervals except
elution number 5 were performed at least 45 hours after the elution number 4.
The elution
efficiency for the daughter product 99"rfc from the column was found to be
within the range
of 75 to 90% (FIG. 18). In elution I, as shown in FIG. 18, more than 80% of
the activity due
to 99mTc is obtained within 9 mIL of saline (0.9% Naa) in where 62% of the
available 99mTc
activity elated in first 3 rriL volume of normal saline, The second elution
was collected at 24
hours after the first elution and shows that the "mTe activity in the column
ranged from 70%
to 90% and can be recovered using 3 to 9 mL of saline solution. In all the
cases, the eluate
was clear, and the pH was in the range of 6 to 7. The column was continuously
eluted over
the period of 8 days with an average ¨82% of the whole 99mIc eluted from the
column.
I001511 FIG. 19
shows the percentage of 'mIc and Mo (VI) released from the
column over the period of 8 days. The concentration of the Mo (VI) in the
eluates was within
the range of 1% to 3% of the 6.25 mmole Mo (VW gram of MPCM in the column. The
process of capturing any molybdenum leakage from the column by passing it
through acid
catalyzed MPCM is possible as shown in FIG, 15 thus reducing the IVlo (VI) and
Mn(V11)
concentrations in the eluent to extremely low levels. Another way of
controlling molybdenum
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leakage from the column can be achieved by controlling the pH of the saline
(0,9% Na
solution within the range of 4 to 4.5 (FIG. 15). In that case, an additional
guard column will
not be necessary to control the leakage of Mo (VI) from the column.
EXAMPLE 4
1001521
Production of 'Mo via neutron capture method draws attention as an
alternative of fission derived Mo due to non-proliferation issues. The 991vlo
produced by the
neutron activation of natural molybdenum would provide a less complex, less
expensive, and
more practical route for indigenous production and use of 99mTe. However, it
is evident that
the specific activities produce by the neutron capture method are not
sufficiently high for the
preparation of small chromatographic generators. This limitation, however, can
be overcome
by the use of adsorbent such as MPCM, which has higher adsorption capacity for
molybdenum. It is demonstrated that MPCM is capable of adsorbing more than
6.25 mnriole
Mo (VI)/ gram (600 mg Ma (V1)/g of MPCM) from an aqueous solution at pH 3,
which is
also applicable to 99Mo obtained easily by the (rt, y) reaction of natural
molybdenum. The
generator in this case consists of MPCM loaded 'Mo thus combines the
performances of the
chromatographic generator and the use of (n, y) 99.Mo, in case of using as an
adsorbent in
99"rfc/99Mo generator, the MPCM is able to hold up to 60 wt% of its body
weight, in
comparison with only 0.2 wt% in the alumina. The potential for MPCM as an
absorbent for
the preparation of the 99Mo/99Ic generator has been explored using 1% Mo (VI)
solution
spiked with Mo (2 mCiirriL). It was observed that MPCM adsorbed Mo (VI) spiked
with
99Mo as per its demonstrated capacity from an aqueous solution at pH 3. It was
also observed
that '"'Tc, which was the decay product of 99Mo, was elated with normal (0.9%)
saline
solution to yield more than 80% elution. A typical 99mTcfi'Mo generator
preparation flow
sheet based on MPCM as an adsorbent is given in Figure 20,
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EXAMPLE 5
[001531 In an
attempt to maximize Mo (VI) uptake and enhance technetium
release from the column prepared using molybdenum loaded MPCM resin, MPCM
resin was
oxidized using sodium hypochlorite (NaC102) and sodium chlorite (3',4a0C1),
respectively.
The concentration of sodium chlorite or sodium hypochlorite in the solution
and the oxidation
time was determined based on trial and error. The concentrations of sodium
chlorite and the
pH of the solution were varied from 1 mmolelL to 10 mmole/L and 3 to I,
respectively. The
oxidation of MPCM by either sodium chlorite or sodium hypochlorite solution
was carried
out at a solid to liquid ratio of 1:100. The oxidation time was varied from 30
minutes to 24
hours. For both sodium chlorite and sodium hypochlorite, it was observed that
solution
containing ¨0.02% chlorine, calculated as C12 at a pH range of 3 to 4.5 and an
oxidation time
of 2 hours was sufficient to oxidize MPCM partially to facilitate maximum
uptake of
molybdenum and also release of technetium from the MPCM sorbent. The MPCM
resins that
were partially oxidized by sodium chlorite and sodium hypochlorite are denoted
as MPCM-
C102 and MPCM-OCI, respectively, herein, The performance of the MPCM-C102 and
MPCM-OC1 was evaluated for molybdenum adsorption from aqueous solutions using
batch
techniques. It was noted that oxidized MPCM can adsorb approximately 6..25 mM
(-600 mg)
of Mo (VI) per g of oxidized MPCM at 298K when the equilibrium concentration
Mo (VI) in
the solution was 54 mrriol/L at pH 3Ø
[001541 A
surface charge analysis of molybdenum loaded non-oxidized MPCM
and molybdenum loaded MPCM-CI02, was carried out using procedures described
above.
Similar surface charge experiments were also performed with molybdenum loaded
MPCM-
OCI and the data was compared with the surface charge of molybdenum loaded non-
oxidized
MPCM resin. The surface charge data of molybdenum loaded MPCM-C102 and MPCM-
OC1
=
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shows a similar pattern to that of molybdenum loaded MPCM that was oxidized by
potassium
permanganate.
10011551 In order
to evaluate Te-99 uptake capacity, two separate columns were
prepared using molybdenum loaded MPCM-C102 and MPCM-OC1, respectively. For
comparison, Tc-99 pass through tests with both of these oxidized MPCM resins
were
performed following the procedures described above. The results confirmed that
pertechnctate (Tc04- ) did not adsorb onto both MPCM-C102 and MPCM-OC1 loaded
with
Mo (VI). Table 7 shows the comparison of the effects of different oxidizers on
technetium
release from a column prepared with oxidized MPCM. The oxidized MPCM resins,
as shown
in Table 7, were exposed to 1% molybdenum solution that was spiked with
moiybdenum-99.
The activity of molybdenum-99 was varied from 45 inCi to 139 Ci (at the end of
irradiation,
or DOI), respectively. The molybdenum loaded MPCM resins that were oxidized by
different
oxidizers were used to prepare respective chromatographic columns. The columns
were then
flushed with saline solution and the data are shown in Table 7.
10/11156]
Technetium release was almost 100% from the column when the initial
activity of Mo-99 in the column was approximately 45 mCi (Table 7). The
release of
technetium from the column was comparatively very low for all oxidizing agents
when Mo-
99 with higher specific activity was used in the column. Without wishing to be
bound by
theory, it is believed that, at higher activity, technetium reduced from WW1)
to Tc(1V) and
the reduced anionic pertechnetate presumably formed covalent bonds with the
free surface
sites of MPCM resin, The release of technetium from the column was
approximately 10%.
when molybdenum-99 with activity of 900mCi was loaded onto MPCM sample that
was
oxidized with 31 mM potassium permanganate (Table 7). This combination also
released
more manganese in the eluent compared to the MPCM resin that was oxidized with
63 rnM
of potassium permanganate. In the case of higher activity of Mo-99 (1.39 Ci at
E01) in the
:54::
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column, a small increase of the percentage of technetium released from the
column was
observed ibr the MPCM-C102 and ropcm-clo resins compared to the resins that
were
oxidized by potassium permanganate or hydrogen peroxide (Table 7).
Table 7: Micro-porous composite resin (MPCM) resin treatment with different
oxidizer
Isotonic solution elution Percentages of "g'Te release from a column with "Mo
performed lo a column loaded with MPCM resin that was partially oxidized
with 99mo activity at E011 with oxidizer
(End of irradiation
Events KMn04 14202 Na0C1 NaC102
3mM 31mM 10% 5 inM 5mM
(0,1%) (0,5%)
45 mCi ............... 100% 100% I 00% I 0 trfa 100%
900 rriCi ____________ 4% __ 10%
i 1.39 Ci 2% =5% 5% ¨9.8% ¨10%
00157I At
higher specific activity (I ,39Ci at E01) of molybdenum in the
column, the release of technetium from the column was reduced significantly
compared to the
column prepared by MPCM resin loaded with low specific activity molybdenum-99.
Without
wishing to be bound by theory, it is believed that at higher activity, the
oxidation state of
metal ions that are present in the column may change; thus reducing technetium
release from
the column. It is believed that the presence of oxidizing agent in the
molybdenum solution
could keep the MPCM resin and molybdenum in the solution in oxidized state
throughout the
adsorption cycle, which may facilitate technetium release from the column.
Furthermore,
addition of oxidizing agent in the ekient saline solution was also considered
in order to
enhance further technetium-99 release from the molybdenum loaded oxidized MPCM
column,
The MPCM-C102 and MPCM-OC1 resins were further studied to
evaluate their potential for molybdenum adsorption in presence of different
concentrations of
oxidizing agent in the solution. The adsorption study was carried out for 24
hours using
different concentrations of sodium chlorite and sodium hypochlorite (5 niM to
50 mM) which
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were spiked with i% molybdenum in solution (prepared from molybdenum salt,
without
radioactive molybdenum (Mo-99)). The molybdenum solution pi-I was initially
adjusted at ¨
3,0 for all the experiments. The samples were collected at different intervals
and were
analyzed for molybdenum uptake onto the resin. Table 8 shows that, in the
presence of
sodium chlorite or sodium hypochlorite in the solution, the molybdenum uptake
capacity of
the oxidized MPCM resin was in the range of 5.21 ritM (500 mg/g) to 6.25 rrtM
(600 mg/a) of
oxidized MPCM. Molybdenum started precipitating out slowly in the solution
after 12 hours
of exposure when the oxidizer concentration in the solution was 45 rrifvt or
higher. No
molybdenum precipitation in the solution was observed for the solution in
which the
concentrations of either sodium chlorite or sodium hypochlorite were in the
range o15 rniVI to
40 m1V1. Molybdenum did not precipitate in the solution during first 4 hours
of the exposure
for any concentration of sodium hypochlorite that was used in this study.
Table 8: Adsorption cycle (1 gram oxidized MPCM in l% Molybdenum solution and
exposure time 24h at
items Coneentratio Oxidizer Mo(V1) uptake on to Mo(V1)
u of oxidizer in the MPCM oxidized with precipitation
in 1% Ma solution during
(VI) solution adsorption
cycle
,
....... I (mM) _____________
t (mM't)i Visual
_______________________________ Na0C1 ... NaCIO, ..
+ ¨1
1 ....... 0 - ........ ¨6.19 ..... ¨6.25 No ____
.i. -*,
2 5 Na0C1 ¨5.8 ¨6.1 No __
=NaC102 ____________________________________ ¨5.75 ¨5.8 No
=,,,
3 10 Na0C1 ¨5.4 ¨6.1 No ..
k
' NaC102 ! ..................... ¨5.5 ¨5.8 No __
4 75 l Na0C1 ¨5.9 .. ¨6.25 ¨I No ......
i NaC102 _____________________ ¨5.8 ¨5.98 ____ No
40 i Na0C1 ¨5.6 ¨5.7 ______ No __
____________________ NaC102 ¨5.5 ¨5.7 .......... No
. ..., .........
6 45 1 Na0C1 - yes .......
____________________ NaC10.3, __ -
7 50 .
Na0C1 - .............................................. yes
,
I NaC102 -
¨ yes
56
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p01591
Molybdenum uptake was found to be fairly consistent onto MPCNI-
C10, in presence of all concentrations of sodium hypochlorite in the 1%
molybdenum
solution (Table 8), Compared to the data obtained from oxidizer-free
molybdenum solution,
the uptake of molybdenum onto MPCM-C10, was approximately 6.25 mMig from a 1%
molybdenum solution containing of 25 mM of sodium hypochlorite (Na0C1) in the
solution
(Table 8). This suggests that presence of hypochlorite in the molybdenum
solution did not
affect molybdenum adsorption substantially onto MPCM resin that was partially
oxidized by
sodium chlorite
/001.601
Therefore, MPCM-C102 was considered in this attempt to adsorb
molybdenum in presence of different concentrations of sodium hypochlorite
(NaOCI) as
oxidizer in the 1% Mo solution. The molybdenum loaded MPCM-C102 was then used
to
prepare a chromatographic column., Sodium chlorite and sodium hypochlorite
were also
mixed with saline solution in order to investigate their oxidizing effects on
the release of both
technetium and molybdenum from the column. The columns were then flushed with
a saline
solution mixed with 5 ritM concentration of sodium chlorite and sodium
hypochlorite,
respectively, at pH 4. The eluate mixture was further spiked with Tc-99
(stoichiametrically
equivalent to ¨1Ci of 'T'c-99m per 10 inIL) before being passed through the
column.
10Ã116111 More
than 99% of Tc-99 passed through the column in the presence of
either sodium chlorite or sodium hypochlorite as oxidizing agent in the eluent
without being
adsorbed in the column (Table 9). The release of molybdenum from the column
during
elution with the saline solution mixed with sodium hypochlorite was similar to
the column
eluted with saline solution mixed with sodium chlorite (Table 9), For
instance, columns
prepared with MPCM-C102 adsorbed molybdenum from a solution containing 1%
molybdenum and 25mM sodium hypochlorite, were flushed with 5 mlvi sodium
chlorite and
sodium hypochlorite, respectively (Table 9). In the case of saline with sodium
chlorite, the
5,7
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release of molybdenum was found to be approximately 2% of the 6.25 mM adsorbed
molybdenum onto MPCM-C102 that was used to prepare the column, whereas
molybdenum
release was found to be approximately- 7.5% from a similar column that was
elated with
sodium hypoehlorite mixed saline solution as shown in Table 9. it was obvious
from this
study that MPCM-C102 is capable of adsorbing approximately 6.25 mM of
molybdenum
from a solution containing I% molybdenum and 25 rriM of sodium hypochlorite,
in the case
of a chromatographic column prepared using molybdenum loaded MPCM-C102 and
then
eluted with Tc-99 spiked saline mixed with sodium chlorite, it was found that
this system was
capable of holding maximum molybdenum and also releasing maximum Tc-99 from
the
column.
Table 9: Typical oxidizer concentration (5 mM) in the elution solution and
related metal ions
release from the column.
Items Concentration Molybdenum Reiease of metal ions from a mo loaded
of No.00I hi uptake onto MPCM-C102 column using 5 mM
I % mpcm-ao2 oxidizing agent in the saline solution,.
molybdenum = resin
solution
=(mM) (mMig) % of Tc-99 release "A
of molybdenum
release
_______________________________ JNooiL NaCl02 NaOC1 NaC102
1 5 ¨6.2 _______________ ¨98
98 .. 3 ! 1.45
2 10 ¨6.1 ¨t-98 ¨98 5 1.8
3 25 ¨6.25 4, ¨98 ¨98 7.5
4 40 ¨5.7 1 ¨98 ¨98 10 4
[00162l The
effect of different sodium chlorite concentration in the eluent for
releasing molybdenum and technetium from the column was further investigated.
Columns
were prepared with MPCM-C102 that adsorbed molybdenum from a solution
containing 1
molybdenum and 25 mtvl sodium hypochlorite. The columns were then flushed with
saline
mixed with different concentration of sodium chlorite, respectively (Table
10). The
concentration of sodium chlorite in the saline was in the range of 5 mM to 20
mM, The eluera
mixtures were further spiked with Tc-99 (stoichiometrically equivalent to ¨10
of Tc-99m
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per 10 till-) before being passed through the COIUMfl. It was observed that
more than 99% of
technetium-99 passed through the column in presence of sodium chlorite as
oxidizing agent
(5mM to 20 EnM concentration) in the eluent without being adsorbed in the
column (Table
/0), The amount of molybdenum release from the column was approximately 2% and
5% of
the molybdenum present in the column when the sodium chlorite concentration in
the saline
solution was 5mM and 20 rnM, respectively. This suggests that a guard column
is desirable in
order to obtain molybdenum-free technetium in the eluent solution.
Table 10, Effect of sodium chlorite concentration in the eluent on the release
of technetium
and molybdenum from column prepared using molybdenum loaded MPCM-C102.
Hems Concentration Mo % of Technetium and molybdenum removal
of NnOCI in uptake from column using NaC102; in elnent saline
1% on to solution
molybdenum MPCM-
________ solution a02
________ inM 5 WAHhnM ______________________________ 20 mM
%Tc %Tc % %Tc %
rvio ........................................... Mo Mo
25 ______________________________________________ ¨6,25 ¨98 0.80 ¨98 2.55
¨98
________ 25 6.2 ¨98 1.25 ,-98 2.4 H98 4,5
3 25 i'6.23 ¨98 ........ 1.45 H98 2.6 ¨98
= 4,9
4 l25 L625 ¨98 1,75 ¨98 2.6 k8 4.98
EXAMPLE 6
100163I The
potential of MPCM-C102 resin as an adsorbent for the preparation
of 99MoiIc generator was evaluated by exposing it to 1% neutron-captured
produced
molybdenum solution with an activity of 13,9 nriCifinl- irradiated at MURR
(the University of
Missouri Research Reactor, USA), A similar experiment was also carried out at
POI-ATOM
using 1% natural molybdenum solution that was spiked with fission molybdenum
(¨ 1,89 Ci
'Motg Mo). Batch adsorption experiments for molybdenum uptake on MPCM-Ci02
resin
were carried out at room temperature while the solution pH for both
experiments was initially
about 3,0. Molybdenum uptake onto the resin for both experiments was
approximately 60%
of the available molybdenum in the solution. In each experiment, a 99Moi99mTc
generator
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consisting of a 6 mL column containing MPCM-C102 resin loaded with "Nilo was
prepared,
99mIc, the decay product of 99Mo, was elated with saline solution (0.9% NaC1)
mixed with
sodium chlorite as an oxidizing agent. Table I shows the elution performance
of a typical
generator that was prepared by exposing Ii MPCM-C102 resin to 100 mL, of
1.39C1 "I'vlo in
total molybdenum solution at an initial pH o1-2L Analysis of the activity
distribution
indicated a Mo adsorption efficiency o163.4%. The time of exposure of MPCM-
C102 resin to
molybdenum solution was 24 hours for these experiments. Following the
adsorption cycle,
the resin was thoroughly rinsed with de-ionized water to remove any adhered
molybdenum
from the surface.
Table 11; Concentration of sodium chlorite in the eluent vs, 9Te release.
isotonic Concentration pH of Percentages of Tc-99rat release from the
solutionof sodium the column that loaded with MPCM resin that
with chlorite in eluent exposed to 1% Mo solution
NaC102 as the eluent mixture
oxidizer mixture
Items mM 0.5 Ci of Neutron 0.138 Ci fission based
activated "Mo 99Mo blended with
(time of elution) natural Mo (time of
_______________________________________________ elution) __
.......................... ¨4,0 6% ______ 4% __
7 5 __________ ¨4.0 40%
3 10 ¨4,0 56% 56 ,4
4 20 __________ 4,0 95%
-)5 I --4.0 100% 100%
6 j40 1-4,0 100% 100%
1001641 From Table II, the
amount of Tc-99rn released from the column
increases with the increase of the concentration of sodium chlorite in the
eluent solution.
Approximately 20 rriM of sodium chlorite concentration in the eluent saline
solution at pH
4.0 appears to be sufficient to remove more than 95% of the Tc-99m from the
column when
the column initial activity was approximately 1C1.
[001651 The Tc-99nri
radioisotope, in the form of an intermediate solution, is
then passed through a guard column with alumina as an adsorbent. The elution
data were
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collected tbr three consecutive days and the data revealed that the elution
contains a yield of
> 90% of the theoretical amount of "Ic available from the generator. The 99Mo
in the eluent
was less than Q.15 IACi of Nfo per triCi of .'"Te. The eluent solution was
hardier subjected to
treatment with either 1M sodium thiosulfate or sodium sulfite to neutralize
the presence of
oxidizer in the solution. The use of sodium sulfite can efficiently neutralize
the oxidizer that
may present in the final eluent. Typical composition of the eluent obtained
from these
experiments is given in Table 12,
Table 12. Typical composition of the final eluent
ItemsI Unit ....................................
Saline solution 0,9% NaC1
Te-99m ........................... 80% ..........
MoiTc 0,15 uCi1mCi of Tc-99m
Al' ______________________________ FDA Limit
NaSO4 ____________________________
. ............................... 0,1% to 0,5% .................
¨
LE1-1 FDA Limit
EXAMPLE 7
[00166]
Addition of potassium di-chromate (approximately 200 mg chromate)
and 5% cerium oxide were also investigated as oxidizers with saline solution
that was used to
flush a molybdenum loaded MPCM-C102 column with some success. In the case of
potassium dichromate or corium oxide in the saline as eluent, Tc-99 release
from the column
prepared from molybdenum loaded MPCM-C102 resin was approximately >75%. A
substantial amount of chromium or cerium was present in the final eluent
solution which
indicates a further requirement of a guard column unit to obtain oxidizer free
technetium in
the final eluent,
EXAMPLE 8
100167] The
effect of temperature and solid to liquid ratio in presence of
oxidizing agent (sodium hypochlorite) in the solution on molybdenum uptake
onto MPCM-
C102 resin were investieated. Batch studies were per/brined at predetermined
different
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temperatures following the procedures previously mentioned. For each
experiment,
approximately 1 gram of MPCM-C102 resin was exposed to 100 rrd.., of 1%
molybdenum
= solution with the presence of oxidizer (25 mM of Na0C1) for 4 hours at pH
¨3.0 (data are not
shown). Preliminary data as shown in Figure 21 reveals that the molybdenum
uptake on to
the MPCM-C102 resin at solution temperature ranging from 250C (298K) to 70"C
(343K) was
varied only slightly (ranging from 5.38 rnM to 5.53 rriM Mo(V1) / gram of MPCM-
C102
resin). In most cases, approximately 50% of the available molybdenum in the
solution was
adsorbed on to MPCM-C102 resin during the first 0.5 hours of operation without
any
precipitation, followed by slow movement toward equilibrium,
[001681 The
heat of adsorption at different loadings of molybdenum on
oxidized MPCM is shown in Figure 22. The heat of adsorption of molybdenum
decreased
with the increase of loading that can be attributed to heterogeneity of the
surface and multi
layer coverage. The heat of adsorption approached the integral heat of
adsorption (All value)
at higher loading. Without wishing to be bound by any theory, it is believed
that the surface
became saturated with molybdenum and the beat of adsorption was approaching
its
equilibrium value. The initial decrease in the values of heat of adsorption
can be attributed to
the heterogeneity of the surface and the multilayer coverage. The subsequent
increase in the
heat of adsorption may be attributed to lateral interactions between the
adsorbed molybdenum
ions, which are known to form complex molecules on a solid surface. It was
expected that
adsorption surface sites of the resin will be homogeneous energetically and,
therefore, a
constant heat of adsorption should be obtained. However, the resin surface
seems to become
heterogeneous energetically, because of the micro-porosity of the surface.
I001691 Batch
studies were carried out varying the solid to liquid ratio in the
presence of 25 rriM sodium hypochiorite as an oxidizer in 1% molybdenum
solution at 25'C
(298K). Almost 95% of the available molybdenum from a 1% solution was adsorbed
on to
.62
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the MPCM-C102. resin within IX, hour of exposure when the solid to liquid
ratio was 2:100 (2
gram MPCM-C102. in 100 rilL of a 1% molybdenum solution that was mixed with 25
rnIM
sodium hypochlorite). This ratio is found to be the optimum adsorbent dose
only for
molybdenum uptake on to MPCM-C102 in presence of 25 nriM sodium hypochlorite
in 1%
molybdenum solution. In the case of non-oxidized MPCIV1, using the same solid
to liquid
ratio and exposure time, the uptake of molybdenum was almost 35% less compared
to the
oxidized-MPCM (IvIPCM-C10-,) resin. The surface charge modification of MPCM by
oxidation and higher solid to liquid ratio in the process appear to be at
least part of the reason
for this phenomenon.
EXAMPLE 9
1001701 Initial
experimental data showed that oxidized-MPCM resin is capable
of adsorbing approximately 50 to 60% of available molybdenum from solution
after 24 hours
of exposure It is also estimated that almost 28% of the 99Mo activity decays
away during 24
hours of the adsorption cycle. Moreover, another 10 to 15% of " M o activity
losses incurred
due to processing and handling of the generator,. Figure 23 shows experimental
data of a 0.5
Ci (at the time elution) 'MoiTc generator described above that typically
requires
approximately 1.6 to 1,8Ci 99Mo (EN) from the very beginning.
1001711 However
the batch experiments suggest that at 25PC (298K)
temperature, the MPCM-C102 resin is capable of adsorbing almost 99% of the
available
molybdenum from a 1% molybdenum solution mixed with 25 rnM sodium hypochlorite
within 1 hour of exposure when a solid to liquid ratio of 2:100 was used.
After rinsing the
molybdenum loaded MPCM-C102 resin thoroughly using de-ionized water, at least
90% (or
up to 95%) molybdenum found to be retained in the resin, which can he used to
prepare a
column for a generator. This will ultimately reduce the losses of 99Mo
activity during the
adsorption cycle and during generator processing and handling. Considering the
loss or 99mo
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during 24 hours of the adsorption cycle to prepare a 6-mL generator column
with activity of
0.5CI at the time of elution), it is projected that a generator with specific
activity of 1.5Ci to
2Ci is possible when a solid to liquid ratio is maintained at 2:100 with a
25"C (298K) solution
temperature during the adsorption cycle (Figure 23), It is also estimated that
a 99Moi99n"Tt:
generator with activity of 4 to 6 Ci based on neutron captured 'Mo is possible
by adjusting
the volume and number of column(s) in the system,
EXAMPLE 10
[00172] About 4
g of chitosan was added to 300 mL deionized (DI) water with
I mL acetic acid and stirred for 2 hr at 70C. to form a gel. About 4 mL of HCI
was added
into the chitosan gel and kept under continuous stirring for another 1 hr at
700C,
100173] in this
example, an amorphous titania gel was prepared by acid
catalyzed controlled hydrolysis and condensation of titanium isopropoxide. See
Hasari, S.,
Ghosh, T.K, Prelas,
Viswanathõ D,S,, and Boddu, V.M. "Adsorption of uranium on a
novel bioadsorherit chitosan coated perlite" Nuclear Technology, 159, 59-71,
2007; Schatika,
Hõ Wong, E.
Antonietti, M., and Caruso, R.A. "Sol-gel templatingof membranes to
form thick, porous titania, titanialzirconia and titania/silica films" Journal
of Materials
Chemistry, 16, 1414-1420, 2006; Agotidjil, N., and Benkacem, T. "Synthesis of
porous
titanium dioxide membranes" Desalination, 206, 531-537, 2007. Equal volumes of
isopropanol (IF) and DI water were mixed in a given amount of titanium
isopropoxide under
continuous stirring at 70T. Drop-wise addition of MCI under continuous
stirring and heating
at 700C produced a clear solution. The hydrolysis and condensation reaction
was controlled
by the ratio of water and titanium and Fr and titanium in the mixture,
respectively. The final
pH of the mixture was approximately 2.0 and the final reactant stoichiometry
was Ti: IF:
0.0132:0.39:1.67:0.01.HO: I4 Based on
the concentration ratio of the reactants, the gel
time was varied between 25 and 45 minutes,
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1001741 At about
75% of the total gel time, a sol-gel solution of amorphous
titania was mixed with chitosan gel. The mixture was kept under stirring at
70'3C for another
1 hr for complete reaction of chitosan and amorphous titanium oxide. The
reaction with
gluteraidehyde was performed by drop-wise addition of about 6 rn.L
glitteraldehyde solution
having a concentration of 50% to the acidic chitosan titania gel under
continuous stirring at
70C. The pH of the final mixture was approximately 1.0, The mixture was kept
under
continuous viizorous stirring at 700C for another 1 hr to obtain a semi-solid
gel
1001751 The
resulting mass was thoroughly washed with 2% monoethanoi
amine to remove any unreacted gluteraldehyde. The mass was then suspended in
0.1M
NaOH solution for 4 to 6 hr. The cross-linked mass was separated from the
solution and
washed with 0.IM HO and then with &ionized water (DI) until the pH of the
washed
solution was 7. The cross-linked mass was then dried in a vacuum oven
overnight at 70"C.
The cross-linked chitosan gluteralclehyde composite prepared in this process
is referred to as
"CGST" herein,
1011761 in the
case of the CGST sample, the peak at 1590cm-1 is found to be
weakened, indicating that the amide groups may be involved in cross-linking
reactions with
titanium. The carbonyl (-CONHR) spectra at around 1650 cm'l is observed for
all three
samples. For primary aromatic amines, C-N stretching vibrations fall between
350 and
I ISO cm*
1001771 There is
a peak observed at 1170 cnO (FIG. 21) for chitosan and
CGST samples, respectively. In comparison to chitosan, the peak at 1170 cmi is
found to be
weakened and a new peak appears at 1090 cm-1 for the CGST samples.
1001781 The peak
that appears at 1090 cm i shows prominent shills due to CO
stretching vibrations of an ether linkage.
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[001791 In the
region of 1000 cm-' to 1200cre, chitosan shows two peaks at
1157 em-1 and 1070 cm, corresponding to the stretching of a C-0 bond of C3 of
chitosan
(secondary OH) and CO stretching of C6 of chitosan (primary OH), respectively.
f00180] Compared
with the CO spectrum of chitosan obtained at 1070 cm-1,
the absorption peaks of the secondary hydroxyl group of the COST samples
become folded,
as indicated in FIG. 24 , and the OH band was reduced and shifted from 3498,0
to 3450,0
supesting that the OH groups of chitosan may be involved in the reaction with
gluteraidehyde through the formation of hemiacetal in the presence of the acid
catalyst, The
evidence of the decrease of the chemical bond constant of CO and the
significant decline in
the OH stretching peaks intensities OH (1000 to 1200 cm') supports the
presence of a
complexing reaction of gluteraldehyde with the surface oxygen functional
groups, such as
secondary hydroxyl group in chitosan. In the case of the CGST sample, titanium
oxide
appears to be involved in a reaction with the amine group of chitosan (FIG,
24),
[001811] Various
embodiments of chitosan based micro-porous composite
material (MPCM) was prepared by cross-linking giuteraidehyde at 71PC in the
presence of
catalyst. MPCM was prepared in the laboratory via the phase inversion of
liquid slurry of
chitosan dissolved in acetic acid and the aldoi condensation of glutaraidehyde
for better
exposure of amine groups (N142), The MPCM was characterized by scanning
electron
microscopy (SEM), which revealed its porous nature. Two MPCM based derivatives
such as
oxidized-MPCM and acid-catalyzed-MPCM were also prepared. The stabilization
study for
MPCM was conducted at 50,000 krad using a ''Co irradiator as a y-source, FT/R,
XPS, and
EDS X-ray microanalysis spectra revealed that the intensity of C, 0, and N
peaks of MPCM
did not change substantially after irradiation. In case of Mo (VI) adsorption
from aqueous
solution at 298K, MPCM can hold up to 60% of its own body weight. The MPCM and
its
derivatives demonstrates the capacity to adsorb 99N4 o and release the
daughter product 'Te
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simultaneously under both batch and equilibrium conditions. It was also
observed that 9yre,
which was the decay product of 99Mo, was eluted with normal (0.9%) saline
solution to yield
more than 80% elution. Data shows that the high elution yield of 99mTc and the
leakage of Mo
(Vi) from the continuous column was minimum therefore the MPCM and its
derivatives can
be used as an adsorbent in the 99mTe/99Mo generator without using any guard
column,
1001821 As used
herein, the terms "around," "approximately," and "about" in
connection with a numerical value denote that some variation from the
numerical value may
be possible, to a maximum of 10% of the numerical value. The terms "a,"
"an," "the," and
the like which denote a single occurrence also should be understood to include
a plurality of
occurrences, unless clearly indicated otherwise,
[001831 A
'MoMmTc generator based on low specific neutron captured
produced molybdenum has been prepared using a novel MPCM resin as an
adsorbent. The
oxidized MPCM resin is found to be capable of adsorbing >95% of available
molybdenum
from the 1% solution at solution pH 3.0 when solid to liquid ratio is 2100.
Almost 90% of
available 99m Tc was eluted with mainly saline solution (0,9% NaC1) from the
generator. The
breakthrough of 99Mo and the pH of the eluent that pass through an alumina
guard column are
within the United States Pharmacopeia (USP) and European Union Pharmacopeia
(EIJI')
limits,
EXAMPLE II
[00184]
Nanoparticles of high Z element or Hafnium (HI) were prepared by
crystal growth or surfactant templating methods using Hafnium chloride as
precursor.
Hafnium nanoparticles were synthesized using either PEG-400 or Pitironic-l23
as surfactant,
The percentage of surfactant used to synthesize the nanopartieles was varied
from 4 to 20%
by weight. The synthesis procedure involved three steps. In the first step,
Hafnium Chloride
(1-IfCi20.81120) and a surfactant ¨either PEG-400 or Pluronic-I23 were mixed
thoroughly in
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a mortar and pestle, and 5 to On-ii of dcionized water was added under
continuous grinding,
in this step, a chemical reaction is not expected; only a homogeneous mixture
is formed, in
the second step, an alkaline solution NaOH¨ or NH401-
I was added to this mixture under
sonication to nucleate and grow the nanoparticles. Nitrogen gas was used to
continuously
purge the system during mixing and sonicatiom Ethanol was added to the mixture
to transfer
the surfactant into the alcohol phase. 'The solution was further sonicated
using 500 ml of
deionized water for 3 h to obtain uniform intermediate stage of hafnium
nanoparticles,
1001.851 The
obtained hafnium particles without further drying or any
processing were crosslinked or dispersed on to ropcm resin preparation matrix.
Finally, the
resin was dried at 120*C for 12 hours using vacuum oven, It was expected that
high Z
element such as Hafnium can be integrated in to the MPCM matrix either self-
assembles or
radiation induced cross-linking process. The prepared resin is termed as MPCM-
Z in this
study. The potential for this MPCM-Z resin as an adsorbent for the preparation
of99Mo/99'T'Tc
generator has been evaluated by exposing it to I% molybdenum solution using
both batch
and continuous process in presence of 5 mM sodium chlorite or hypoehlorite as
an oxidizer,
in case of neutron activated Mo-98 solution, it is important to note that
oxidizing agent keeps
i'vlo-98 at hexavalent state thus facilitating molybdenum loading onto the
resin without any
precipitation. Both experiments demonstrated that the MPCM-Z resin absorbs >60
IA%
molybdenum at solution pH 10. The molybdenum loaded MPCM-Z resin was further
subjected to irradiation up to 750 kGy using e-beam, to demonstrate its
radiation resistance
capability in presence of high radiation field. Figures 25 and 26 shows
typical IR spectra of
unirradiated molybdenum loaded MPCM-Z resin and the molybdenum loaded MPCM-Z
resin irradiated at 250 kGy and 750 kGy respectively,
1001861 As
illustrated in Figures 25 and 26, the absorption peaks that appears at
17 1620
crri'l, and 1030 cm' are ascribed for carbonyl, amide-I, and C-O-C groups
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respectively. Since MPCM-Z resin was loaded with molybdenum, it is reported
that the
amine absorption spectra is considered to be unchanged. Therefore, the
intensity ratio of
hydroxyl, carbonyl and C-O-C spectra were calculated in terms of respective
amine
absorption spectra. The relationship between these intensity ratios and
radiation doses are
shown in Figure 27 and provided in Table 13 below.
Table 11 Relationship between radiation dose and peak intensity
Item
[336C/1E620 03C -0-C
0/1E 620 Carbonyl __
Mo-MPCM-Z 0.916 1.51 ____________ 0.448
Mo.-MPCM-Z (250kGy) 0.867 _______ 1.67 ........... 447 ..
MO-MPCM-Z (750kG,y) 0.874 1.71 ............. 0A33
1001871
Figure 27 shows that the C-0-C group slightly increases with the
increasing of radiation dose, suggesting that there may not any chain scission
of CO bonds
occurs due to radiation. Weinwei et al reported that there are two kinds of CO
bond in
chitosan structure: a) half condensed aldehyde and glucosidic bonds, If the
half condensed
aldehyde bonds broken due to irradiation, carbonyl is believed to be formed.
It is evident
from Figure 27 that there is no substantial changes occur in the carbonyl peak
intensity at
peak position 1710 ore due to irradiation. On the other hand scission of
glucosidic bonds
leads to the formation of hydroxyl groups. Therefore, if chain scission of
glucosidic bond
occurs, the hydroxyl peak intensity will increase with the increase of
radiation dose. For
molybdenum loaded MPCM-Z resin, the hydroxyl group concentration or peak
intensity ratio
is appeared to be decreased due to irradiation. Without being bound by theory,
it was
believed that the Hafnium ions in the MPCM matrix interact with the imparted
energy from
the ionizing radiation and protect or insulates the CO bond therefore no chain
scission in
= MPCM matrix occurs due to radiation.
1001881
in this attempt, the MPCM-Z resin was further studied to evaluate their
potential for molybdenum adsorption. A generator consisting of MPCM-Z resin
loaded with
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Mo (lCilgram of resin) was prepared following a process mentioned elsewhere
The
molybdenum loaded MPCM-Z was then used to prepare chromatographic column, The
columns were then flushed with a saline solution at pH 4 to remove any loosely
bound
molybdenum, '''''"rfc, the decay product of '9Mo, was eluted with saline
solution (0,9% NaCI).
It was observed that about *50% of 'I`c was extracted from the column using 6
mL of
saline as an eluent. The saline solution used to elute ''''"Tc from the MPCM-
Z, was modified
with additives such as sodium nitrate (104 in an attempt to improve yield. The
99mTc
recovery was markedly better ¨ about 70%. It seemed evident that the MPCM-Z
resin
showed better performance in higher radiation field produced by the 'Mo
compared to
partially oxidized lVIPCNil resin. A guard column with alumina as an adsorbent
was used to
keep 'Ivlo in the eluent >I mCi ofMo per mCi of 99mIc. The pH of the eluent
was within
4,5 to 7,5, The elution contains a yield of > 80% of the theoretical amount
of 99Te available
from the "Nif o over the life of the generator,
[001891 The
present invention having been described with reference to certain
specific embodiments and examples, it will be understood that these are
illustrative, and do
not limit the scope of the appended claims,