Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ARSENIC REMOVAL
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application claims the benefit of U.S. Provisional Patent
Application
No. 60/500,259, filed September 5, 2003, which is incorporated by reference.
FIELD OF THE INVENTION
[0002] This invention pertains to polymer beads for removing arsenic from
aqueous
fluids such as groundwater.
BACKGROUND OF THE INVENTION
[0003] Arsenic is a toxic and ubiquitous metalloid element that can be found
in
groundwaters around the world at levels well above the maximum containment
level of 10
~g/L recommended by the World Health Organization (WHO). Arsenic poses a
serious threat
to millions of people worldwide, and geogenic (natural) contamination has been
reported in
many countries, including countries having large populations such as India and
China. In the
U.S., the Environmental Protection Agency (EPA) has recently decreased the
limit of arsenic
in drinking water from 50 ~g/L to 10 ~g/L, and all systems for treating
drinking water must
comply with the new standard by January 2006.
[0004] Arsenic occurs mainly as arsenate As(V) (having a +5 oxidation state)
and arsenite
As(III) (having a +3 oxidation state) in groundwaters. Different compounds can
be formed
with arsenic in groundwater depending on the arsenic oxidation state. The
distribution of
As(III)/As(V) varies significantly in groundwater. As(III) can represent in
the range of about
30% to about 98% of the total arsenic in groundwaters.
[0005] Conventional systems for removing arsenic have suffered from a number
of
drawbacks such as low efficiency and/or specificity. For example, some ion
exchange systems
have less affinity for As(V), particularly when other ions (e.g., sulfate,
chloride, and/or
phosphate ions) are present in the fluid being treated. Typically, As(III) is
pre-oxidized to
As(V) so that the oxidized form can subsequently be removed.
[0006] Alternatively, or additionally, some ion exchange systems require
regeneration
after a relatively short period of time. For example, Clifford has estimated
bed volumes for 10
percent and 50 percent breakthrough of influent arsenic (Figure 3-15, J. AWWA,
X6:4:10
(1995)), showing the regeneration frequencies for ion exchange columns as a
function of
influent sulfate concentration. Regeneration can involve using brine solution,
and this creates
another arsenic-containing waste stream that must also be processed. While
brine solutions
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can be re-used, the resultant arsenic concentration can exceed the technology
based local limits
(TBLL), and the spent solution must be treated andlor disposed of.
[0007] The present invention provides for ameliorating at least some of the .
disadvantages of the prior art. These and other advantages of the present
invention will be
apparent from the description as set forth below.
BRIEF SUMMARY OF THE INVENTION
[0008] An embodiment of the invention provides a chelate-forming material
comprising
a crosslinked polymeric bead having bound chelate-forming groups and a volume
capacity
of about 1.5 mmol/mL or less, wherein the chelate-forming groups comprise
protonated N-
methyl-D-glucamine, and have the capability of forming a chelate with As(V)
and/or
compounds thereof.
[0009] Alternatively, or additionally, another embodiment of the invention
provides a
chelate-forming material comprising a crosslinked polymeric bead having bound
chelate-
forming groups and a nitrogen content of about 2.4 mmol/g or more, wherein the
chelate-
forming groups comprise protonated N-methyl-D-glucamine, and have the
capability of
forming a chelate with As(V) and/or compounds thereof.
[0010] In some embodiments, the protonated N-methyl-D-glucamine is in chloride
form, or in sulfate form.
[0011] An embodiment of a method for treating an arsenic-containing aqueous
fluid
according to the invention comprises contacting an As(V)-containing fluid with
crosslinked
polymeric beads each having bound chelate-forming groups and a volume capacity
of about
1.5 mmol/mL or less, wherein the chelate-forming groups comprise protonated N-
methyl-
D-glucamine and have the capability of forming a chelate with arsenate(V)
and/or
compounds thereof, forming the chelate with As(V) and/or a compound thereof,
and
separating the chelated As(V) and/or compound thereof from the fluid.
[0012] Yet another embodiment of a method for treating an arsenic-containing
aqueous
fluid according to the invention comprises contacting an As(V)-containing
fluid with
crosslinked polymeric beads each having bound chelate-forming groups and a
nitrogen
content of about 2.4 mmol/g or more, wherein the chelate-forming groups
comprise
protonated N-methyl-D-glucamine and have the capability of forming a chelate
with
axsenic(V) andlor compounds thereof, forming the chelate with As(V) and/or a
compound
thereof, and separating the chelated As(V) and/or compound thereof from the
fluid.
[0013] In another embodiment, a process for preparing a chelate-forming
crosslinked
polymeric bead having a volume capacity of about 1.5 mmol/mL or less and/or a
nitrogen
content of about 2.4 mmol/g or more, wherein the bead is comprised of a
crosslinked
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polymer bound to chelate-forming groups, comprises obtaining a crosslinked
polymeric
bead having functional groups, reacting the functional groups with N-methyl-D-
glucamine,
and producing a protonated N-methyl-D-glucamine.
DETAILED DESCRIPTION OF THE INVENTION
[0014] An embodiment of the invention provides a crosslinked polymeric bead
having
bound chelate-forming groups and a volume capacity of about 1.5 mmol/mL or
less,
wherein the chelate-forming groups comprise protonated N-methyl-D-glucamine,
and have
the capability of forming a chelate with As(V) and/or compounds thereof. In a
preferred
embodiment, the bead has a volume capacity of about 1.3 mmol/mL or less.
[0015] Alternatively, or additionally, another embodiment of the invention
provides a
crosslinked polymeric bead having bound chelate-forming groups and a nitrogen
content by
dry weight basis of about 2.4 mmol/g or more, wherein the chelate-forming
groups
comprise protonated N-methyl-D-glucamine, and have the capability of forming a
chelate
with As(V) and/or compounds thereof. In a preferred embodiment, the bead has a
nitrogen
content by dry weight basis of about 2.5 mmollg or more.
[0016] In some embodiments of crosslinked beads according to the invention,
the
protonated N-methyl-D-glucamine is in chloride form, or sulfate form.
[0017] In an embodiment, the crosslinked polymeric bead comprises
poly(vinylbenzylchloride) ox chloxomethylated styrene wherein the chelate-
forming groups
are bound to at least a portion of the -CHZ groups of the benzyl moieties. In
another
embodiment, the crosslinked polymeric bead comprises poly(glycidyl
methacrylate)
wherein the chelate foaming groups are bound to at least a portion of the
glycidal groups of
the acrylate moieties.
[0018] In some embodiments, the crosslinked polymeric bead comprises a
polymerized
bi-, tri-, or tetra-functional monomer, or any combination thereof, to provide
the crosslinks.
The bi-, tri-, or tetra-functional monomer can be selected from the group
consisting of
ethylene glycol diacrylate, di(ethylene glycol) diacxylate, tetra(ethylene
glycol) diacrylate,
ethylene glycol dimethacrylate, di(ethylene glycol) dimethacrylate,
tri(ethylene glycol)
dimethacrylate, butanediol diacrylate, hexanediol diacrylate, N,N-
methylenebisacrylamide,
N,N-(1,2-dihydroxyethylene) bisacrylamide, and divinylbenzene, or any
combination
thereof.
[0019] A system for treating arsenic-containing aqueous fluid according to an
embodiment of the invention comprises a bed comprising crosslinked polymeric
beads each
bead having bound chelate-forming groups, and a volume capacity of about 1.5
mmol/mL
or less and/or a nitrogen content by dry weight basis of about 2.4 mmol/g,
wherein the
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chelate-forming groups comprise protonated N-methyl-D-glucamine, and have the
capability of forming a chelate with As(V) and/or compounds thereof.
[0020] An embodiment of a method for treating an arsenic-containing aqueous
fluid
according to the invention comprises contacting an As(V)-containing fluid with
crosslinked
polymeric beads, each bead having bound chelate-forming groups, and a volume
capacity of
about 1.5 mmol/mL or less and/or a nitrogen content by dry weight basis of
about 2.4
mmollg or more, wherein the chelate-forniing groups comprise protonated N-
methyl-D-
glucamine, and having the capability of forming a chelate with arsenic(V)
and/or
compounds thereof, forming the chelate with As(V) and/or a compound thereof,
and
separating the chelated As(V) or compound thereof from the fluid. A preferred
embodiment
of the invention comprises separating As(V) from groundwater.
[0021] In another embodiment, a process for preparing a chelate-forming
crosslinked
polymeric bead having a volume capacity of about 1.5 mmol/mL or less and/or a
nitrogen
content of about 2.4 mmol/g or more, wherein the bead is comprised of a
crosslinked
polymer bound to chelate-forming groups, comprises obtaining a crosslinked
polymeric
bead having functional groups, reacting the functional groups with N-methyl-D-
glucamine,
and producing a protonated N-methyl-D-glucamine. In some embodiment of the
process,
the crosslinked polymeric bead having functional groups comprises a
poly(vinylbenzylchloride) bead, a chloromethylated polystyrene bead, or a
poly(glycidyl
methacrylate) bead. The functional groups on the crosslinked polymer bead can
be
haloalkyl groups or epoxy groups.
[0022] The present invention is preferably used to treat source water, such as
municipal
drinking water, water from natural sources such as lakes, rivers, reservoirs,
surface water,
groundwater and storm water runoff, or industrial source water, or wastewater,
such as
industrial wastewater or municipal wastewater. Source water may also include
treated
wastewater which has, for example, been purified after industrial use.
[0023] Embodiments of the invention can also be used to treat As(V)-containing
brine.
[0024] Advantageously, in view of the affinity, selectivity, and sorption
capacities of
the beads according to the invention, beds including the beads can be used to
treat greater
volumes of water and/or treat the water for longer periods of time, before
replacement
and/or regeneration, than beds including conventionally available beads.
Additionally,
since the beds can be used for longer periods of time before regeneration,
less regeneration
treatment fluid is needed for a given period of time and/or there is less
process downtime
for the beds, compared to that for beds including conventionally available
beads.
[0025] The invention provides for the removal of As(V) from influent aqueous
fluids,
typically source water having a pH in the range of from about 1 to about 1 l,
preferably,
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having a pH in the range of from about 4 to about 6.5. As used herein, removal
of As(V)
includes removal of the axsenic-containing negatively charged compounds
typically formed
in natural waters at a pH in the range of 2 to 11, i.e., H2AsO41 and HAs04 2.
In some
embodiments, the invention provides for the removal of the arsenic-containing
uncharged
compound, H3As02, formed in aqueous fluids at a pH of about 1 to about 1.5.
[0026] Embodiments of the invention can efficiently remove As(V) from
groundwater
having a sulfate concentration of greater than 120 mg/L, e.g., up to about 800
mg/L, or more
and/or can efficiently remove As(V) from groundwater having a phosphate
concentration of
up to about 400 mg/L, or more. Alternatively, or additionally, embodiments of
the
invention can remove As(V) from aqueous fluids in the presence of 1M NaCI.
[0027] The chelate-forming groups of the present invention comprise protonated
N-
methyl-D-glucamine represented by formula (I):
OH
H
OH
-N 4
+~
CH3 (I)
[0028] The chelate-forming group, N-methyl-D-glucamine (NMDG), can be
quantified
by a variety of techniques, including elemental analysis. Elemental analysis
is performed to
determine the amount of nitrogen, or equivalents of nitrogen, present in the
chelate-forming
group. Since the chelate-forming group is the sole group that contains
nitrogen, the
equivalents of nitrogen are directly related to the equivalents of the chelate-
forming group
present on the bead. This can be further defined as "theoretical specific
capacity", (IUPAC
Compendium of Analytical Nomenclature, section 9.2.5.4, 1997, 3rd ed.) which
is the
amount (mmol) of ionogenic group per mass (g) of dry ion exchanger.
[0029] Illustrative elemental analytical techniques for determining the
nitrogen content
of beads according to the invention are ASTM D 5373 (2002) "Test Methods for
Instrumental Determination of Carbon, Hydrogen, and Nitrogen in Laboratory
Samples of
Coal and Coke" and ASTM D 5291 (2003) "Test Method for Instrumental
Determination of
Carbon, Hydrogen, and Nitrogen in Petroleum Products and Lubricants."
[0030] For example, when analyzed in accordance with ASTM D 5373, crosslinked
beads according to embodiments of the invention, comprising the protonated
N-methyl-D-glucamine, have a nitrogen content, on a dry weight basis, of 2.35
mmol/g or
more. Typically, when analyzed in accordance with ASTM D 5373, crosslinlced
beads
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according to embodiments of the invention have a nitrogen content, on a dry
weight basis,
of 2.46 mmol/g or more.
[0031] In accordance with some embodiments of the invention, the crosslinked
bead
comprising the protonated N-methyl-D-glucamine, has a nitrogen content, on a
dry weight
basis, of about 2.4 mmol/g or more, preferably, a nitrogen content of about
2.5 mmol/g or
more, more preferably, a nitrogen content of about 2.6 mmol/g or more, and in
some
embodiments, a nitrogen content of about 2.7 mmol/g or more.
[0032] In accordance with the invention, the bead (or particle) is preferably
a
non-porous bead, although it may have pores having diameters of 50 Angstroms
or less,
e.g., micropores. The bead is crosslinked. Preferred crosslinked polymeric
beads comprise
poly(vinylbenzylchloride) copolymer beads and poly(glycidyl methacrylate)
copolymer
beads. Other embodiments include, for example, crosslinked chloromethylated
polystyrene
copolymer beads, and crosslinked polymer beads functionalized with amine
reactive
chemistries such as epichlorohydrin and azlactone.
[0033] In some embodiments, the crosslinked polymeric bead comprises a
polymerized
bi-, tri-, or tetra-functional monomer, or any combination thereof, to provide
the crosslinks.
The bi-, tri-, or tetra-functional monomer can be selected from the group
consisting of
ethylene glycol diacrylate, di(ethylene glycol) diacrylate, tetra(ethylene
glycol) diacrylate,
ethylene glycol dimethacrylate, di(ethylene glycol) dimethacrylate,
tri(ethylene glycol)
dimethacrylate, butanediol diacrylate, hexanediol diacrylate, N,N-
methylenebisacrylamide,
N,N-(1,2-dihydroxyethylene) bisacrylamide, and divinylbenzene (DVB), or any
combination thereof.
[0034] A variety of crosslinkers can be used in preparing beads according to
the
invention. Preferred crosslinking agents include compounds with two or more
groups.
Exemplary crosslinkers include ethylene glycol di(meth)acrylate (EGDMA),
ethylene
glycol diacrylate, di(ethylene glycol) diacrylate, tetra(ethylene glycol)
diacrylate, ethylene
glycol dimethacrylate, di(ethylene glycol) dimethacrylate, tri(ethylene
glycol)
dimethacrylate; butanediol diacrylate, hexanediol diacrylate,
methylenebisacrylamide, N,N
methylenebisacrylamide, N,N-(1,2-dihydroxyethylene)bisacrylamide), and
divinylbenzene
(DVB).
[0035] The degree of crosslinking is preferably about 7% or less, more
preferably, about
5% or less, and in some embodiments, about 3% or less. The desired range can
be varied
depending on, for example, the hydrophilicity of the backbone polymer and the
structure of
the crosslinking agent. Illustratively, the degree of crosslinking can be in
the range of from
about 2% to about 7% (e.g., wherein the bead includes a more hydrophilic
backbone
polymer such as, for example, poly(glycidyl methacrylate)), or from about 2%
to about 5%
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(e.g., wherein the bead includes a more hydrophobic backbone polymer, such as,
for
example, poly(vinylbenzylchloride) or chloromethylated polystyrene).
[0036] Without being limited to any particular mechanism(s), it is believed
the polymer
chains (e.g., polystyrene backbone) forming the bead are flexible, and this
flexibility, and
the level of crosslinking are important, so that the lower level of
crosslinking (about 7% or
less) allows increased swelling of the bead, allowing more reactive groups to
bind NMDG
to the bead, providing more available surface area allowing a greater amount
of the NMDG
to be bound to the bead, and allowing more of the protonated NMDG to be
accessed by the
As(V) in the fluid to be treated. As a result, more of the protonated NMDG is
available for
selectively forming a chelate with the As(V) and/or compounds thereof.
[0037] In some embodiments of the invention, the crosslinked polymeric bead
having
bound chelate-forming groups has volume capacity of about 1.5 mmol/mL or less,
preferably, about 1.3 or less. In some embodiments, the volume capacity is in
the range of
from about 1.5 mmol/mL to about 1.1 mmol/mL. Without being bound to any
particular
mechanism, it is believed the volume capacity can be generally correlated with
the degree of
crosslinking.
[0038] As used herein, the volume capacity is, as defined in IUPAC Compendium
of
Analytical Nomenclature, section 9.2.5.4, 1997, 3rd ed., the amount (mmol) of
ionogenic
group per volume (cm3) of swollen ion exchanger. The ionic form of the ion
exchanger and
the medium should be stated. In accordance with the present invention, the
ionic form of
the ion exchanger is the protonated amine, and the medium is water.
[0039] In an embodiment of the invention, the swelling ratio is about 1.5 or
more,
preferably about 2.3 or more. Typically, the swelling ratio is in the range of
from about 1.5
to about 2.5, and in some embodiments, can be greater than about 2.5.
[0040] As used herein, the swelling ratio refers to the increase in volume
when
comparing the volume of the beads after a specified time in water to the
volume of vacuum
dried beads. The specific swelling ratios referenced in the Examples section
herein were
determined using 2 mL of vacuum dried beads that were placed in a 10 mL
cylinder of
water, wherein the volume was determined after 19 hours.
[0041] ~ In accordance with the invention, the process for preparing a chelate-
forming
crosslinked polymeric bead comprises obtaining a crosslinked polymeric bead
having
functional groups, and reacting these functional groups with NMDG to bind the
NMDG to
the crosslinked bead. Preferred functional groups are haloalkyl groups, i.e.,
chloromethyl,
or epoxy groups. In those embodiments wherein the crosslinked polymeric bead
comprises
poly(vinylbenzylchloride) or chloromethylated polystyrene, the reactive
functional groups
are chloromethyl groups, and the NMDG becomes bonded to the -CH2 groups of the
benzyl
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moieties via a nucleophilic substitution reaction at the chloromethyl group.
In those
embodiments wherein the crosslinked polymeric bead comprises poly(glycidyl
methacrylate) or epichlorohydrin, the reactive functional groups are epoxy
groups, and the
N-methyl-D-glucamine becomes bonded to the glycidal groups of the acrylate
moieties via
a ring-opening reaction of an epoxy group.
[0042] The resulting bead is conditioned with a dilute acidic solution such
as, for
example, HCl or HZS04, to produce a protonated amine moiety on the chelate-
forming
group. For example, the bead can be conditioned with HCl to provide protonated
N-methyl-
D-glucamine in chloride form, or conditioned with H2SO4 to provide protonated
N-methyl-
D-glucamine in sulfate form. If desired, one form can be exchanged to the
other, e.g., the
sulfate form can be exchanged to the chloride form, or the chloride form can
be exchanged
to the sulfate form. For example, the chloride form can be soaked in water,
and
subsequently conditioned with NaOH, water, H2S04, and water,
[0043] The following examples further illustrate the invention but, of course,
should not
be construed as in any way limiting its scope.
EXAMPLE 1
[0044] This example describes of the preparation of chelate-forming beads
according to
an embodiment of the invention.
[0045] 2.0 grams of crosslinked beads comprising polymerized
vinylbenzylchloride
(VBC) and divinylbenzene (DVB) (crosslink level 2 wt.%) were swelled in 50 ml
dioxane
and transferred into a 250 mL round bottom flask equipped with a condenser and
an
overhead stirrer. 20 g of NMDG was added to 10 mL of water and 100 mL 1,4-
dioxane.
The mixture was heated at reflux for 17 hours. After washing, the beads were
conditioned
with 1L each of water, 4% aq. NaOH, 4% aq. HCl, and water.
EXAMPLE 2
[0046] This example describes of the preparation of chelate-forming beads
according to
another embodiment of the invention.
[0047] 1.5 grams of crosslinked beads comprising polymerized glycidyl
methacrylate
(GMA) and DVB (crosslink level 8 wt.%) were swelled in 50 ml dioxane and
transferred
into a 250 mL round bottom flask equipped with a condenser and an overhead
stirrer. 10 g
of NMDG was added to 10 mL of water and 100 mL 1,4-dioxane. The mixture was
heated
at reflux for 3 hours. After washing, the beads were conditioned with 1L each
of water, 4%
aq. NaOH, 4% aq. HCI , and water.
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EXAMPLE 3
[0048] This example demonstrates the swelling ratio of chelate-forming beads
according to an embodiment of the invention.
[0049) 2 mL of the beads described in Example 1 are vacuum dried and placed in
a 10
mL cylinder filled with water. After 19 hours, the volume of the beads is 4.6
mL, and thus,
the swelling ratio is 2.3.
EXAMPLE 4
(0050] This example demonstrates the volume capacity of chelate-forming beads
according to an embodiment of the invention.
(0051] Beads are prepared as described in Example 1. Elemental analysis is
performed,
and combined with the swelling ratio determined as in Example 3, it is
determined the beads
have a volume capacity of 1.19 mmol Nitrogen/mL.
EXAMPLE 5
[0052] This example demonstrates the selective formation of chelates with
As(V) of
chelate-forming beads according to an embodiment of the invention as compared
to
commercially available beads and fibers including NMDG, particularly in the
presence of
sulfate.
[0053] Polymerized VBC-DVB (crosslink level 2 wt.%) beads including NMDG are
prepared as described in Example 1. Additionally, the following commercially
available
beads including NMDG are obtained: Diaion CRB-02 (Mitsubishi Chemical),
Purolite
S-108 (Purolite Co.), and Amberlite IRA-743 (Rohm and Haas). The following
commercially available cotton fibers including NMDG are also obtained: GCP,
GRY, and
GRY-L (Chelest Corp.). Each set of beads and fibers is placed in contact with
As(V)
solutions as described below.
[0054] The beads and fibers are all conditioned with 1 L each of water, 4%
NaOH,
water, 4% HCl and water, and vacuum dried at 70 °C. Nitrogen elemental
analysis is
performed on each set of beads and fibers, and beads and fibers containing 0.3
meq of
nitrogen are placed in contact with the As(V) solutions.
[0055] Two sets of As(V) solutions are prepared using sodium hydrogen arsenate
Na2HAs04, 7Ha0 (AlfaAesar). The solutions are 20 mL As(V) 100 ppm. One set of
As(V)
solutions includes a concentration of 560 mg/L 5042- (pH 6.0). The set of
As(V) solutions
without SO42- has a pH of 5.8.
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[0056] Each set of As(V) solutions is placed in contact with a separate set of
beads and
fibers, i.e., beads prepared in accordance with Example 1 are contacted with
the solutions,
and each of the commercially available beads and fibers are contacted with the
solutions. In
placing the As(V) solution in contact with the beads and fibers, 20 mL of the
solution is
placed in a Nalgene 40 mL bottle containing the beds or fibers, on a shaker.
The total
contact time is 3 days.
[0057] Arsenate concentrations are analyzed by the molybdenum blue method
(Charlot)
using a spectrophotometer Spectronic 21 D (Milton Roy) equipped with'/2 " test
tube. For
lower concentrations, solutions are analyzed by ICP-MS (Hewlet Packaxd)
[0058] All of the beads and the GRY and GRY-L fibers remove more than 99% (the
GCP fibers remove 98.6%) of the arsenic present in solution from the solution
without
5042-. CRB-02 achieves a residual As(V) concentration of 80 ppb, S-108
achieves a
residual As(V) concentration of 890 ppb, IRA-743 achieves a residual
concentration of 300
ppb, and the VBC-DVB beads prepared in accordance with Example 1 remove 99.9%
of the
arsenic with a residual As(V) concentration of less than 50 ppb.
[0059] The equilibrium solution concentrations (mg/L) and sorption capacities
(mg/g) at
equilibrium solution concentration are, respectively: 0.03 mg/L and 16.4 mg/g
(VBC-2%
DVB bead), 0.30 mg/L and 14.7 mg/g (IRA-741), 0.08 mg/L and 14.9 mglg (CRB-
02), 0.89
mglL and 14.8 mg/g (S-108), 1.42 mg/L and 8.88 mg/g (GCP), 0.04 mg/L and 6.92
mg/g
(GRY), and 0.04 mg/L and 7.45 mg/g (GRY-L).
[0060] With respect to the As(V) solution including a concentration of 560
mg/L SOø 2,
the efficiency of removal of As(V) drops for the commercially available beads
when
compared to the solution without 5042-, i.e., CRB-02 drops from 99.9% to
90.3%, S-108
drops from 99.1 % to 77.9%, and IRA-743 drops from 99.7% to 79.4%. The
efficiency of
removal for each of the GGP, GRY, and GRY-L fibers is, respectively, 98.8%,
97.8%, and
98.9%.
[0061] The equilibrium solution concentrations (mg/L) and sorption capacities
(mg/g) at
equilibrium solution concentration are, respectively: 20.7 mg/L and 13.3 mglg
(IRA-741),
9.70 mglL and 13.7 mg/g (CRB-02), 22.2 mg/L and 11.8 mg/g (S-108), 1.21 mg/L
and 9.06
mg/g (GCP), 2.22 mg/L and 6.87 mg/g (GRY), and 1.04 mg/L and 7.46 mg/g (GRY-
L).
[0062] The VBC-2% DVB beads prepared in accordance with Example 1 essentially
maintain the removal efficiency and sorption capacity, in that the removal
efficiency is
99.4%, and the sorption capacity (at an equilibrium solution concentration of
0.63 mg/L) is
16.6 mg/g.
EXAMPLE 6
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[0063] This example describes of the preparation of chelate-forming beads
according to
another embodiment of the invention, and the selective formation of chelates
with As(V) of
the chelate-forming beads.
[0064] 2.0 grams of beads comprising polymerized chloromethylated polystyrene
DVB
beads (Sybron Chemicals Inc.) (crosslink level 3 wt.%) were swelled in 20 ml
dioxane and
transferred into a 250 mL round bottom flask equipped with a condenser and an
overhead
stirrer. 20 g of NMDG was added to 10 mL of water and 100 mL 1,4-dioxane. The
mixture
was heated at reflux for 17 hours. After washing, the beads were conditioned
with 1 L each
of water, 4% aq. NaOH, 4% aq. HCl and water.
[0065] Nitrogen elemental analysis is performed in accordance with ASTM D 5373
and
beads containing 0.3 meq of nitrogen are placed in contact with the As(V)
solutions as
described in Example 5.
[0066) The beads remove 99.9% of the As(V) present in solution from the
solution
without 5042-, and achieve a residual As(V) concentration of 65 ppb. The beads
remove
96.3% of the As(V) present in solution from the solution with a concentration
of 560 mg/L
5042-.
EXAMPLE 7
[0067] This example describes of the preparation of chelate-forming beads
according to
another embodiment of the invention.
[0068] 2.0 grams of beads comprising polymerized VBG and EGDMA (crosslink
level
2 wt.%) are swelled and placed in a 250 mL round bottom flask equipped with a
condenser
and an overhead stirrer. 20 g of NMDG (Arcos Organics) is added to 10 mL of
water and
100 mL of dioxane. The mixture is heated at reflux for 17 hours. After
washing, the beads
are conditioned with 1 L each of water, 1N NaOH, water, 1N HCI, and water,
then vacuum
dried at 70° C for 17 hours and characterized by FTIR and nitrogen
elemental analysis.
EXAMPLE 8
[0069] This example demonstrates the selective formation of chelates with
As(V) using
crosslinked beads having the sulfate form of protonated NMDG according to
another
embodiment of the invention.
[0070] Beads are prepared as described in Example 7 to provide beads having
the
chloride form of protonated NMDG. The beads are treated to exchange the
chloride form
for the sulfate form by soaking the beads in 1 L of water for 2 hours,
followed by
conditioning with 1L of 1N NaOH, 1L of water, 1L of 1N H2S04, and 1L of water.
CA 02536178 2006-02-16
WO 2005/023409 PCT/US2004/028977
12
[0071] Six ml of the beads are arranged in a 1 cm diameter 10 cm long
minicolumn,
and, in accordance with the ANSI/NSF 53 protocol, challenge water containing
50 ppb
As(V), 50 ppm sulfate, 40 ppb phosphate, 2 ppm nitrate, 71 ppm chloride, and 1
ppm
fluoride ions is continuously passed through the column. The As(V)
concentration in the
effluent is consistently reduced below 10 ppb and no breakthrough is observed
after 1000
bed volumes.
EXAMPLE 9
[0072] This example describes of the selective formation of chelates with
As(V) of
chelate-forming beads according to an embodiment of the present invention in
the presence
of different concentrations of chloride or sulfate ions.
(0073] 1.6 grams of crosslinked beads comprising VBC and polymerized DVB
(crosslink level 2 wt.%) are swelled and placed in a 250 mL round bottom flask
equipped
with a condenser and overhead stirrer. 20 g of NMDG (Arcos Organics) is added
to 10 mL
of water, and 100 mL of dioxane. The mixture is refluxed for 17 hours. After
washing, ~tlie
beads are conditioned with 1 L each of water, 1M NaOH, water, 1 M HCI, and
water, then
vacuum dried at 70°C for 17 hours and characterized by FTIR and
nitrogen elemental
analysis.
[0074] Additionally, Amberlite IRA-900 beads (Rohm and Haas) are obtained and
conditioned and dried as set forth above.
[0075] Six sets of As(V) containing solutions are prepared, each containing
100 mg
As(V)/L in 0.01, 0.10, and 1.0 M of either Cl- or SO42-, respectively. 100 mg
of each type
of dry beads is contacted with 20 mL As(V), 100 mg/L, pH 6.5, at each
concentration of
either sulfate or chloride ions.
[0076] Arsenate is analyzed by the molybdenum blue method using a Spectronic
21D
spectrophotometer. At lower concentrations, and in the presence of phosphate,
solutions are
analyzed by ICP-MS (Hewlett-Packard 4500 series).
(0077] At 0.10 M of either Cl- or SO4a-, the beads prepared according to an
embodiment
of the invention sorb 96% and 83% of the arsenate, respectively, while IRA-900
sorbs less
than 10% As(V) in the presence of either competing ion. The trends are
identical at all
three concentrations. Sulfate ions interfere more than chloride ions. However,
with respect
to 0.01 M solutions, the effect is much more pronounced with IRA-900 than with
the beads
prepared according to an embodiment of the invention.
EXAMPLE 10
CA 02536178 2006-02-16
WO 2005/023409 PCT/US2004/028977
13
[0078] This example describes the preparation of chelate-forming beads
according to
other embodiments of the invention, and the selective formation of chelates
with As(V) of
the chelate-forming beads as compared to commercially available resins
including NMDG,
particularly in the presence of sulfate.
[0079] 1.6 grams of crosslinked beads comprising VBC and polymerized DVB
(crosslink levels 2 wt.%, 5 wt.%, 8 wt.%, and 12 wt.%) are swelled and placed
in a 250 mL
round bottom flask equipped with a condenser and overhead stirrer. 20 g of
NMDG (Arcos
Organics) is added to 10 mL of water, and 100 mL of dioxane. The mixture is
heated at
reflux for 17 hours. After washing, the beads are conditioned with 1 L each of
water, 1M
NaOH, water, 1 M HCI, and water, then vacuum dried at 70°C for 17
hours and
characterized by FTIR and nitrogen elemental analysis.
[0080] 1.6 grams of 3 wt.% DVB-crosslinked chloromethylated polystyrene beads
including NMDG are also prepared as described above.
[0081] Additionally, the following commercially available beads including NMDG
are
obtained as described in Example 5: Purolite S-108, Diaion CRB-02, and
Amberlite IRA-
743.
[0082] Beads containing 0.3 mmol of nitrogen are placed in contact with the
As(V)
solutions for 21 hours.
[0083] Two sets of As(V) solutions are prepared. One solution is 20mL As(V),
100
mglL, pH 6. The other solution is 20 mL As(V), 100 mg/L + 560 mg/L 5042-, pH
6.
[0084] Each set of As(V) solutions is placed in contact with a separate set of
beads, i.e.
NMDG beads prepared as described above at each crosslink density are contacted
with the
solutions, CRB-02 beads are contacted with the solutions, S-108 beads are
contacted with
the solutions, and IRA-743 beads are contacted with the solutions.
[0085] Arsenate is analyzed by the molybdenum blue method using a Spectronic
21D
spectrophotometer. At lower concentrations, solutions are analyzed by ICP-MS
(Hewlett-
Packard 4500 series).
[0086] With the exception of the 12 wt.% DVB-VBC NMDG beads, all of the beads
remove more than 99% of the arsenate present in solution from the solution
without 5042-.
The 12% DVB-VBC NMDG beads remove about 95% of the arsenate present in
solution
from the solution without 5042-.
[0087] With respect to the As(V) solution including a concentration of 560
mg/L S04 ~,
the efficiency of removal of As(V) drops for the commercially available beads
when
compared to the solution without SO42-, i.e., CRB-02 drops to about 73%, S-108
drops to
about 50%, and IRA-743 drops to about 55%.
CA 02536178 2006-02-16
WO 2005/023409 PCT/US2004/028977
14
[0088] With the exception of the 8 wt.% and 12 wt.% DVB-VBC NMDG beads, all of
the other prepared non-commercially available crosslinked NMDG beads (having
2%, 3%,
and 5% crosslinking levels) remove over 90% of the arsenate present in
solution from the
solution with 5042'. The 8 wt.% and 12 wt.% DVB-VBC NMDG beads remove about
55%
and about 40%, respectively, of the arsenate present in solution from the
solution with
5042'.
EXAMPLE 11
[0089] This example describes of the higher nitrogen content by dry weight
basis of the
chelate-forming beads according to other embodiments of the invention as
compared to
three commercially available products.
[0090] Crosslinked beads comprising polymerized VBC and DVB (crosslink levels
2
wt.%, 5 wt.%, 8 wt.%, and 12 wt.%) including NMDG are prepared as described in
Example 10. Crosslinked beads comprising polymerized VBC crosslinked with
EGDMA
(crosslink levels 2% and 4%) including NMDG are prepared as described in
Example 7.
[0091] The following commercially available beads including NMDG are also
obtained:
Amberlite IR.A-743, Diaion CRB-02, and Purolite S-108.
[0092] Nitrogen elemental analysis of the beads is performed in accordance
with ASTM
D 5373.
[0093] The results are as follows:
Bead including NMDG Nitrogen content (mmollg)
2% DVB gel polyVBC 2.62
3% DVB gel chloromethylated 2.68
polystyrene
5% DVB macroporous polyVBC 2.58
8% DVB macroporous polyVBC 2.21
12% DVB macroporous polyVBC 1.81
2% EGDMA polyVBC 2.69
4% EGDMA polyVBC 2.58
IRA-743 2.24
GRB-02 2.26
S-108 2.27
[0094] The table shows that, when analyzed in accordance with ASTM D 5373,
prepared beads having less than 8% crosslinking have a nitrogen content by dry
weight
CA 02536178 2006-02-16
WO 2005/023409 PCT/US2004/028977
basis of greater than 2.35 mmol/g, and commercially available beads have a
nitrogen
content by dry weight basis of 2.27 mmollg or less.
[0095] All references, including publications, patent applications, and
patents, cited
herein axe hereby incorporated by reference to the same extent as if each
reference were
individually and specifically indicated to be incorporated by reference and
were set forth in
its entirety herein.
[0096] The use of the terms "a" and "an" and "the" and similar referents in
the context
of describing the invention (especially in the context of the following
claims) are to be
construed to cover both the singular and the plural, unless otherwise
indicated herein or
clearly contradicted by context. Recitation of ranges of values herein are
merely intended to
serve as a shorthand method of referring individually to each separate value
falling within
the range, unless otherwise indicated herein, and each separate value is
incorporated into the
specification as if it were individually recited herein. All methods described
herein can be
performed in any suitable order unless otherwise indicated herein or otherwise
clearly
contradicted by context. The use of any and all examples, or exemplary
language (e.g.,
"such as") provided herein, is intended merely to better illuminate the
invention and does
not pose a limitation on the scope of the invention unless otherwise claimed.
No language
in the specification should be construed as indicating any non-claimed element
as essential
to the practice of the invention.
[0097] Preferred embodiments of this invention are described herein, including
the best
mode known to the inventors for carrying out the invention. Of course,
variations of those
preferred embodiments will become apparent to those of ordinary skill in the
art upon
reading the foregoing description. The inventors expect skilled artisans to
employ such
variations as appropriate, and the inventors intend for the invention to be
practiced
otherwise than as specifically described herein. Accordingly, this invention
includes all
modifications and equivalents of the subject matter recited in the claims
appended hereto as
permitted by applicable law. Moreover, any combination of the above-described
elements
in all possible variations thereof is encompassed by the invention unless
otherwise indicated
herein or otherwise clearly contradicted by context.
