Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRODMLYSIS-DISTILLATION HYBRID PROCESS FOR Ent RECOVERY OF
DIMETHY'LSULFOXIDE (DMSO) SOLVENT FROM INDUSTRIAL EFFLUENT
FIELD OF INVENTION
The present invention relates to the development of a suitable integrated
process for the recovery of
dimethyl sulfoxide (DMSO) from industrial effluents using membrane based
electrodialysis and
distillation process.
The present invention further relates to the separation of DMSO from
industrial process solution
containing undesirable components such as salts (sodium azide and ammonium
chloride) and small
amount of color imparting substances.
BACKGROUND OF JUL INVENTION
Reference may be made to patent US5746920, Mani, issued on 25th September,
2001, which
describes an apparatus and the process producing salts by an electrodialysis
operation.
Reference may be made to patent US 5324403, Baltazar, Varujan Jamaluddin Abul
K.M, Kennedy, -
Mark W, Na.zarko, Taras W, issued on 28'h June 1994, which describes a method
for the selective -
removal of alkali metal salts of sulphate (S042), and thiosulphate (S2032")
from hydrogen sulphide
(H2S) scrubber solutions of the liquid redox type using an electrodialysis
system. In the process of
this invention the H2S scrubber solution is directed to the diluting
compartments within an
electrodialysis stack, while collecting a solution with a minimal initial salt
content. With the
application of a direct current, a portion of the alkali metal salts of
sulphate and thiosulphate present
in the scrubber solution are transported through ion selective membranes into
the collecting solution.
Reference may be made to patent US 3755134, Francis, Leo H., Treleven, Gerald
J, issued on 28th
August 1973, which relates to an electrodialysis apparatus for reducing the
mineral salt content of
liquid materials having dispersed organic constituents (e.g., whey).
Reference may be made to patent US 5145569, Schneider, Michael, Miess, Georg
E, issued on 8th
September 1992, which relates to a process for desalting mixtures of water and
water-soluble highly
active organic solvents which contain metal salts. This process comprises
subjecting the mixtures to
electrodialysis employing commercially available ion exchanger membranes.
Reference may be made to U.S. Pat. No 4802965, Puetter, Hermann, Roske,
Eckhard, issued on 7th
February 1989, which relates to concentrating the aqueous solutions of organic
compounds that
contain salts, with simultaneous reduction of the salt content. Aqueous
solutions of organic
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compounds which contain salts are concentrated by electrodialysis with
simultaneous reduction of
the salt content of these solutions.
Reference may be made to U.S. Pat. No 7351311, Windecker, Gunther, Week,
Alexander, Fischer,
- Rolf-Hartmuth, Rosch, Markus, Bottke, Nils, Hesse, Michael, Schlitter,
Stephan, Borchert, Holger,
issued on 1 April, 2008, which relates to a continuous process for
distillative purification of
tetrahydrofuran (TI-IF).
. Reference may be made to U.S. Pat. No 4613416, Kau. Heinz Russow, Jurgen,
issued on 23rd
September, 1986, which relates to application of the process of
electrodialysis for concentrating the
sulfuric acid containing an alkali metal sulfate, sulfuric acid and alkaline
earth metal ions.
Reference may be made to patent US 6627061, Mani, K. N, issued on 30th
September, 2003,
which describes an apparatus and process produces salts by an electrodialysis
operation. The divalent
metals are removed by nanofiltration and further sent to electrodialysis to
remove multivalent
cations.
Reference may be made to patent US 6294066, Mani, K. N, issued on 25th
September. 2001, that
relates to a process that produces salts by electrodialysis operation by
nanofiltering the incoming
feed to remove divalent metals.
Reference may be made to patent US 4770748, Cellini, John V. Ronghi. Mario
F.Geren, James
G, issued on 13th September. 1988, which discloses the application of an
improved vacuum
distillation system for purifying contaminated liquids, such as seawater,
brackish water and chemical
effluents.
Reference may be made to patent US 4390396, Koblenzer, Heinz, issued on 28th
June, 1983, that
relates to an apparatus for the distillation of vaporizable liquids, more
particularly, to an energy-
conserving distillation system of compact construction for the distillation of
vaporizable liquids of all
types.
Reference may be made to patent US 4233120, Finlay-Maxwell, David, issued on
11th November
1980, which relates to solvent-recovery processes and provides a method and
apparatus whereby
substantial heat economy may be achieved in the recovery of a solvent which is
soiled by its use in,
,for example, a thy-cleaning operation, or which in use has become mixed with
another solvent.
Reference may be made to patent US 5312524, Barcomb, Lyle.B, issued on 17th
May, 1994, that
refers to a distillation system for recovery of volatile components of
contaminated liquids used in an
=
industrial process.
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The literature available from patents describe only the removal of organic or
inorganic salts from the
industrial process solutions. A proper process is absent for the recovery of
valuable solvents present
in the pharmaceutical effluents.
Therefore with increasingly strict environmental regulations, industrial
effluents require extensive
treatment prior to their safe disposal. Moreover, some of these effluents,
especially from
pharmaceutical industries may contain valuable solvents, which need to be
recovered.
Hence there still remains, a need for an improved, cost effective and
practical method for the
removal of inorganic salts, azide and also color imparting organic compounds
present if any,
particularly from these types of effluents which contain valuable solvents.
OBJECTIVE OF THE INVENTION
The main objective of the present invention is to provide a process for the
recovery of DMSO
solvent from a pharmaceutical effluent, useful in bulk drug manufacture.
An object of the invention is to provide a multi-stage process to facilitate
maximum possible
recovery of the DMSO.
Another objective of the present invention is to remove the ammonium chloride
and sodium azide
salts present in the pharmaceutical effluent.
Yet another objective of the present invention to provide a vacuum
distillation apparatus and a
method capable of effectively separating liquid mixture components.
Yet another objective of the present invention to provide a process which is
able to isolate pure
DMSO, as simply as possible and with a high yield, from the desalted liquor
obtained from
electrodialysis.
Yet another objective of the present invention is to identify the process
required to achieve the
maximum recovery of the DMSO with minimum losses.
Yet another objective of the present invention is to achieve around 99.8 % of
DMSO.
Yet another objective of the present invention is to produce not only as much
pure DMSO as
possible but at the same time to produce a correspondingly small amount of
residue requiring landfill
or incineration.
BRIEF DESCRIPTION OF Ilit., DRAWINGS:
FIG.1: Represents the schematic process flow diagram for recovering DMSO from
industrial
effluent.
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FIG.2: Represents electrodialysis (ED) stack arrangement.
FIG.3: Represents migration of ions to its respective electrodes.
FIG.4: Schematic showing the description of the whole process.
FIG.5: Graph representing variation of current with time
FIG.6: Graph representing variation of concentration with time
FIG.7: Graph representing variation of concentration with time of all three
solutions.
FIG.8: Overall material Balance for a four ED runs and subsequent
distillations to recover pure
DMSO.
SUMMARY OF THE INVENTION:
Accordingly, present invention provides an electrodialysis-distillation hybrid
process for the
recovery of pure dimethyl sulfoxide (DMSO) from industrial effluents and the
said process
comprising the steps of:
i. preffltering the effluent by passing through the micron filter cartridge
to remove the
suspended solids followed by an activated carbon column to reduce color and to
obtain diluate of conductivity ranging between 15 to 25 mScm-1;
ii. circulating rinse solution of conductivity ranging between 20-35 mScm-1
across the
electrodes of the electrodialysis stack system followed by diluate as obtained
in step
(i) and concentrate solutions of conductivity ranging between I to 2 inScm-1
to the
electrodialysis stack system until the conductivity of the diluate solution
dropped to
0.06 mScm-1 to obtain desalted diluate;
iii. charging desalted diluate as obtained in step (ii) into two distillation
column to
obtain water as distillate and impure DMSO as bottoms in the first stage and
= followed by second distillation to recover colorless pure DMSO as
distillate and
heavy impurities as bottoms.
= In an embodiment of the present invention, industrial effluents contain
NaN3, NH4CI salts, water,
non-volatile heavy organic compounds and small amount of color imparting
substances".
= In an another embodiment of the present invention, concentration of DMSO
in effluent is ranging
between 12 to 20 wt%.
In yet another embodiment of the present invention, concentration of NaN3 and
NI-14C1 in
pharmaceutical effluents is ranging between 0.5 to 2 wt%.
In yet another embodiment of the present invention, diluate containing DMSO,
NaN3, NH4C1 and
water.
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In yet another embodiment of the present invention, concentrating solution
contains tap water that
contains total dissolved solids (TDS) between 0.03 and 0.19%.
In yet another embodiment of the present invention, rinse solution contain 2.0
to 3.0 % by weight of
aqueous solution of sodium bisulphate.
In yet another embodiment of the present invention, electrolyte used in the
concentrate is an aqueous
solution of a common salt such as sodium chloride which will allow electrical
conduction.
In yet another embodiment of the present invention, the flow rate of diluate,
concentrate and rinse
solution across the membrane stack is ranging between 0.9 and 0.1 liters per
second.
A process as claimed in claim 1, wherein said process is carried out in a
continuous mode with the
solution recycled back.
In yet another embodiment of the present invention, recovery percentage of
DMSO is ranging
between 88 to 90% and purity percentage is ranging between 99.5 to 99.8%.
In yet another embodiment of the present invention, the re-boiler temperature
in the first distillation
column varied between 30 and 75 C, the reflux ratio was varied from 1:5 to
1:15 and the overhead
temperature was maintained between 30 and 32 C using chilled water available
at 5 C.
In yet another embodiment of the present invention, the re boiler temperature
in the second
distillation column varied between 45 and 120 C, the reflux ratio was varied
between 1:5 and 1:15 '
and the overhead temperature varied between 30 and 95 C.
In yet another embodiment of the present invention, the composition of the low
boilers leaving the
first and second distillation column is determined by a gas chromatograph
using a Tenax column,
thermal conductivity detector and hydrogen carrier gas with the oven
temperature initially
maintained at 70 C for 5 minutes and programmed to reach 230 C at the rate of
10 C per minute.
In yet another embodiment of the present invention, stages of distillation set
up consists of
electrically heated 20 L still over which mounted a 3" glass column packed
with 25mm ceramic
rasching rings and the height of the packing is about 5' ,wherein the DMSO can
be separated
efficiently with high degree of purity from water.
DETAILED DESCRIPTION OF THE INVENTION
The process of the present invention , is particularly directed towards the
recovery of solvents
generally seen as waste byproducts to be incinerated without energy recovery
or deposited in
protected dumps.
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The idea that led to the solution of the above problem was that of initially
removing the dissolved
salts by electrodialysis and further treating the obtained desalted aqueous
DMSO solution by
distillation for recovering pure DMSO.
Present invention provides a hybrid process including electrodialysis and a
simple distillation
process to achieve this object.
The present invention generally relates to a process of reducing the salts
present in aqueous DMSO
effluent, and to use the products obtained by such process. More specifically,
the present invention
relates to subjecting the effluent containing 2% salts (sodium azide and
ammonium chloride) to an
electrodialytic treatment to produce an aqueous DMSO solution having a reduced
content of salts.
The present invention accordingly provides a two stage process of distillation
for recovering pure
DMSO from the desalted diluate of electrodialysis process.
The process of this invention is further illustrated by making reference to an
example of aqueous
DMSO distillation carried out in a conventional distillation column operated
under vacuum. The
process of this invention could, however, be ,carried out under different
conditions, and by using
distillation columns designed for varying pressure operation and adjusting the
experimental
parameters in ways well known to the persons skilled in the art.
Present invention relates to a process for the recovery of DMSO from
industrial process solution
containing undesirable components such as ammonitun salts, sodium azide and
small amounts of
inorganic color imparting substances. These salts can be removed by membrane
based electrodialysis
technique to obtain desalted liquor wherein the said process comprising the
steps of pre filtration of
feed before it is fed into ED system to remove the suspended solids. The pre
filtered solution as a
feed solution through the electrodialysis system (Et) system) containing
alternate cation, anion
membranes stack with simultaneous application of direct current to enhance
separation of ions
towards the respective electrodes, wherein the solution is substantially
devoid of the salts and
undesirable components to obtain desalted liquor.
FIG.1 shows the schematic process flow diagram for recovering DMSO from
industrial effluent. In
brief, effluent from the storage tank is charged for pre filtration process to
remove the suspended
solids. Pre-filtration followed by the electrodialysis system for separation
of salts, for example
ammonium chloride and sodium azide from the aqueous solution.
Electrodialysis stack system contain at least 10 alternate anion and cation
exchange membranes in a
parallel arrangement between anode and cathode electrode plates.
electrodialysis stack system also
consist of diluating compartment, a concentrating compartment and a rinse
compartment where all
the three ED compartment solutions are operated under re-circulation mode.
Diluating compartments
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and concentrating compartments arranged in alternate fashion to provide an
effective area of 0.525 m
2 area each of cation and anion-exchange membranes. DC potential between 50
and 70 V is applied
across the stack to generate an average current of 3-4 A. Electrodialysis
operation results in
separation feed as diluate and concentrate. The process depicted in FIG.1 also
represents the 2- stage
distillation operation, where in water and (DMSO+ Impurities) is obtained in
the first stage and
followed by second distillation results in recovering colorless DMSO as
distillate and heavy
impurities as bottoms. However, in the industrial processes of use in the
practice of the invention,
the entire process may be conducted in a continuous mode with the solution
recycled back to the
respective tanks. Accordingly, in consequence, the feed composition will vary
with time as will the
diluate and concentrate tanks.
FIG. 2 represents electrodialysis stack arrangement for desalting the
effluent. The desalting
electrodialysis cell stack (1) is comprised of at least ten pairs of anion (2)
and cation (3) exchange
membranes creating diluate and concentrate compartments between the two
electrodes anode (A)
and cathode (C) electrodes. DC power supply (4) Provides the driving force for
separation through
_15 the arrangement of cell pairs, four of which are indicated as (5)
in the Figure. Each cell pair
comprises of one cation and one anion exchange membrane. The stack is arranged
in a systematic
manner, in the form of chambers, such that each chamber consists of respective
number and
arrangement of gaskets, distributors with alternate membranes. The cation
exchange membranes
may be of weak acidity (carboxylic acid exchange groups), moderate acidity (e.
g. phosphonic acid
20 type), or strongly acidity (e. g. sulfonic acid cation exchange
groups). The cation and anion exchange
membranes must be stable under the physical and chemical conditions applied in
electrodialysis cell;
the membranes should have a low resistance in the solution to be dialyzed,
high flux and low fouling
by colloidal and suspended materials. These may include perfluorinated
membranes such as Dupont =
Nafion. RTM. or any non-perfluorinated cation exchange membrane such as
Neosepta, CMX. The
25 anion exchange membranes may be strongly, mildly, or weakly basic
and comprised of quaternary or
tertiary ammonium groups. This type of membrane will improve the current
efficiency of the process
by preventing back-migration of protons from the concentrate compartment to
the feed compartment.
FIG.3 represents migration of ions to the respective electrodes. This Figure
diagrams the desalting
ED process and the membrane configuration in the ED membrane cell stack used
for separating
30 dissolved inorganic salts from pharmaceutical effluent containing
DMSO and the dissolved salts
such as sodium azide and ammonium chloride. The components of the
electrodialysis cell stack (10)
include an anode (A) and cathode (C) electrodes rinsed with an electrolyte,
having four diluate
compartments (D1,D2, D3,D4) and three concentrate compartment (CI,C2,C3)
disposed between the
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anode and cathode wherein the feed and concentrate compartments are separated
by alternating
cation and anion exchange membranes, (13) and (14), respectively. ED stack
arrangement is shown
in FIG. 2 and the movement of positive and negative ions through four membrane
ceil pairs of the
stack is described in FIG. 3 which is an enlarged view of the separation
process occurring in
indicated part (5) of FIG. 2.
FIG. 4 shows the process utilizing an electrodialysis system and two
distillation columns connected
in series. Typically, the feed solution derived from the pharmaceutical
industry comprises DMSO,
water and inorganic salts. A pretreatment step for the feed solution comprises
the following: (i)
filtration to remove particulates; (ii) carbon treatment to adsorb color
bodies and other organic
impurities. The process according to the invention is advantageously carried
out initially by
prefiltering the pharmaceutical effluent containing suspended solids by
passing through the activated
carbon and micron filter and then sending to the electrodialysis stack
containing alternate anion and
cation exchange membranes between two anode and cathode electrode plates made
of stainless steel
SS 316 L containing 3% molybdenum in a parallel arrangement, sealing the
compartments formed
by inserted spacer frames off against each other, passing the filtered
effluent with salts (diluate)
whose initial conductivity is between 15 to 25 mScnci through the feed
compartments which are
limited in the direction of the anode via an anion exchange membrane, and
passing tap water
(concentrate) whose initial conductivity is from 1 to 2 mScm-I throtigh those
compartments Iimitea
in the direction of the anode by a cation exchange membrane to receive the
salt. The electrolyte used
in the concentrate is in general an aqueous solution of a common salt such as
sodium chloride which
will allow electrical 'conduction. During the electrodialysis process, an
electrolyte-containing
solution is preferably guided past the electrodes in order to remove gases
which form from the
electrode compartments. The electrode rinse used is advantageously an aqueous
solution which
contains about 2.5 wt% of sodium bisulfate. The preferably obtained desalted
diluate from the
electrodialysis is charged to the distillative process carried out in two
columns connected in series as
shown by the Figure 4 for the purification of water- containing DMSO.
Introduction of the feed into the first colurmi¨is effected at the side
through the inlet (4). The inlet (4)
is conveniently disposed into the re-boiler of the column. Then the re-boiler
is heated to a
temperature in accordance to the boiling point of the lighter component
present. The lighter
component being water vaporizes through the packing material and is condensed
and collected as the
distillate of the first distillation column. The left out heavier components
being DMSO remains as
bottoms of the first distillation column. These bottoms of first distillation
column are sent to the
second distillation column (3) via line (la) as feed. The feed of the second
distillation column is
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heated in its re-boiler to a temperature above its boiling point and is
vaporized through the packed
column and condensed in the condenser and collected as colorless DMSO and the
leftover bottoms
are collected as heavier compounds via line (1w).
FIG. 4 show the flow of solution across the equipment involved in the
inventive process for the
recovery of DMSO from pharmaceutical industrial effluent. The Figure shows the
step wise
procedure of obtaining pure DMSO. In the process, dissolved salts in the
effluent are desalted by the
electrodialysis process. Then it is further sent to the distillation column
for recovering DMSO.
The pharmaceutical industrial effluent containing 2 % sodium azide and
ammonium chloride salts
and 15 % DMSO with a conductivity ranging between 15-25 mScm. is stored in the
storage tank
(4) and is pumped to the micron filter (5) through the line (11) to filter the
suspended solids present in
the effluent and then sent to the activated carbon column (6) to absorb the
contaminants present in
the effluent and is sent to the diluate tank (7). The concentrate tank (9) is
filled with 10 liters of tap
water having conductivity of about 1-2 mSctril Prepared 10 liters of 2.5 %
sodium bisulphate
solution in distilled water is charged to the rinse tank (8) having a
conductivity in the range 20-35
niScm-1. Initially the rinse solution is circulated across the electrodes of
the electrodialysis stack (1)
with a lcnown flow rate through pump via line (13), and then the diluate and
concentrate solutions are
pumped to the electrodialysis stack (1) through lines (12) and (14)
respectively at same flow rates
ensuring almost equal pressure drops. After stabilizing the flow an electrical
potential was applied
through DC (14) across the stack to attain a specific current density for a
desired period. All the
solutions were circulated through the ED stack until the conductivity of the
diluate solution dropped
to 0.06 inScrn.-1, to ensure that salt-free diluate solution is sent to the
first distillation column (2).
The desalted diluate solution containing water and DMSO of tank (7) is charged
to the re-boiler of
the first distillation column (2) through line (15) and heated to a
temperature of low boiling
component water and is evaporated through the column and collected as
distillate in (10) via line (17).
The bottoms of the first distillation column (2) that is left out with colored
DMSO is stored in
storage tank (11) through line (16) and this is sent to the bottoms of the
second distillation column (3)
via line (1) and heated at high temperature corresponding to the vacuum
applied and is distilled
through the column (3) and the colorless DMSO is collected as distillate
product with a purity of
99,8% in the tank (12) via line (19). And the left over bottoms of the second
distillation column (3) are heavier
components.
Re boiler temperature in the first distillation column varied between 30 and
75 C, the reflux ratio
was fixed at 1: 15 and the overhead temperature was maintained between 30 and
32 C using chilled
= water available at 5 C. Re boiler temperature in the second distillation
'column varied between 45
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and 120 C, the reflux ratio was fixed at 1:15 and the overhead temperature
varied between 30 and
95 C.
In the present invention the feed solution is tested at applying different
voltages like 30V, 40 V, 50V,
60V and 70V to find the optimum voltage and current density to be known for
the separation of salts
in the ED process. The conductivity of the solutions is determined after a
definite interval of time,
say, 20 or 30 minutes using a digital conductivity meter since the extent of
loss of salts from the feed
is estimated in accordance to the conductivity of the solutions.
We assume that all the salts have been removed from test solution when the
conductivity reaches
0.08 or 0.09 mScm."I.
In described process, five batches of 16 kg each of the desalted liquor from
electrodialysis unit are
fed into the first distillation column of height 100 cm and diameter 7.5 cm
packed with glass raschig
rings to remove water as the distillate under a vacuum between 30 and 40 mmHg
to obtain 16 kg of
DMSO-rich residue in the re-boiler of 20 L capacity. 16 L of the concentrated
residue from the first
distillation column is fed into a second distillation column of design similar
to that indicated in claim =
=
14, but operated under a vacuum between 20 and 30 mmHg to initially remove
water as the first
fraction followed by recovery of 11.28 kg of colorless DMSO of purity > 99.5 %
as the second
fraction to yield a final residue of 0.72 Kg in the re-boiler that is enriched
in nonvolatile color
= imparting organic compounds and is sent for incineration.
The process of the invention involves membrane cleaning and maintenance to
prevent its fouling and
keep the system at good efficiency and long working life.
Cleaning procedure:
== It is recommended to wash the stack with solution comprising of 1 % TSP,
0.5 %
EDTA and 0.5 % w/v sodium lauryl sulphate (SLS) in distilled water for 15
minutes.
= The former is followed with tap water wash for 15 minutes.
= Successively an acid wash is given for 30 minutes, this is achieved by
making a solution of 2
% v/v HC1 in tap water, which helps in removal metal salts and mineral scales
and
subsequently better electrical conductivity of the system.
= Finally a water wash is given for 15 minutes.
Routine repetition of the above mentioned last 3 steps after each run of
electrodialysis will ensure
better performance of the system in terms of batch time reduction.
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An example was taken for instance to note the trend followed by current w.r.t
varying time. From the
graph it can be depicted that as the time passes the current decreases as the
ions migrate from the
diluate tank.
Similarly, variation of pH and conductivity with change in time was also
noticed for all the three
tanks. It has been observed that, the time passes, the conductivity and pH of
the diluate tank
= decreases which can be because of loss of salts from the tank and that of
concentrate tank increase
linearly for some time and then remain constant. In the case of rinse tank
both conductivity and pH
remain almost constant through out the experiment. A digital conductivity
meter is used to analyze
the concentration of total inorganic salts present in the diluate, concentrate
and rinse solutions and a
digital pH meter is used to assess the pH of the three solutions at regular
intervals of time between 0
and 4 hours.
Data was collected using an experimental ultrex ion exchange membranes of area
for batch or
continuous operation. All runs were conducted at potential difference between
30V ¨ 70V.
The following examples are given by way of illustration of the working of the
invention in actual
practice and therefore should not be construed to limit the scope of present
invention in any way.
EXAMPLE .1
An electrodialysis device of the type as essentially outlined was used for the
electrodialysis treatment
of the pharmaceutical effluent Alum. The resin solution had a salt content of
2 % by weight, a
conductivity of 15-25 mScniland the treatment was started at a temperature of
30 degree C.
10 liters of filtered feed solution (effluent) containing 2% salts (sodium
azide + ammonium chloride)
in 15% aqueous dimethylsulfoxide (DNISO) was taken in the diluate tank. 10
liters of tap water was =
taken in the concentrate tank to facilitate conductivity and ion transfer. 7
liters of 2.5% sodium
bisulphate (w/v) was taken in the rinse tank to rinse both the electrodes.
After filling tanks with its respective solutions, control valves were
adjusted to maintain equal flow
rates in diluate and concentrate tanks ensuring almost equal pressure drop.
All the solutions were
pumped continuously through the electrodialysis stack at controlled flow
rates. After stabilizing the
flow an electrical potential was applied across the stack to attain a specific
current density for a
desired period. Initially a voltage of 30 V was applied through direct current
and achieved current in
the range of 0-4 amps due to high conductivity (24.9 mScnil) of the diluate
solution. About 30 ml of
samples of outlet streams of the three solutions were collected every 1 hr to
determine the
conductivity of salts by digital conductivity meter and back transferred into
their respective tanks to
maintain the constant volume through out the experiment. This process
continued until the diluate
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conductivity of 0.07 mSciril was reached. Since the amount of salt depleted in
the diluate tank is ,
measured through electrical conductivity of the solution. The flow rates of
diluate solution
concentrate solution and rinse solution are 252.72 L ht., 258 A8.L lift and
568.8 L hr-1 respectively.
. Voltage Applied: 30V. . .
.
The first trial lasted for approximately 18 hours. The results are as reported
in Table 1.
=
. .
,
- Table 1: Experimental data
Time Conductivity ( mScm-1) Voltage Current
= 10 (mm) Diluate Concentrate Rinse (V) (A)
0 24.9 1.2 33.9 30 3.4
60 18 20.2 30.2 30 4
120 14 28.4 35.9 30 3.3
180 8.41 243 20.1 30 1.5
240 6.35 26.4 19 30 1.5
315 4.74 27.4 16.8 30 1 -
375 2.96 29 15.5 30 0.8
435 2.36 27.1 15.8 30 0.5
495 1.1 27.5 15.8 30 0.5
570 1.04 29.4 14.2 30 0.7
630 0.6 30.3 14.5 30 0.3
690 0.4 31 14.7 30 0.25 .
705 0.4 31.3 14.3 30 0.2
765 0.22 31.8 14.4 30 0.2
825 0.1 33.2 14.9 30 0.2
885 0.1 33.8 15.2 30 0.2
995 0.097 32.4 12.3 ___
30 0.25 _
1055 0.1 33.1 , 12.4 30 0.2
1115 0.07 33.2 12.2 30 0.25
The following Table 1 summarizes the transport of the salts .from the diluate
tank to the concentrate
tank. During the test, the conductivity levels in the diluate decreased, while
these levels increased in '.
the concentrate, this is due to the transport of salts from the diluate tank
to the concentrate tank.
As the initial conductivity of the feed was very large and the applied voltage
was only 30 y this
experiment has taken a long time (more than 18 hrs) to reach a final
conductivity of 0.07 mScnil.
12 .
_ .
. .
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In this example, it was observed that the reduction in diluate conductivity
was rapid until the solution
reached a conductivity of 0.1 mScnil beyond which the process of ion transfer
was taking a longs
time to reach a conductivity of 0.07 mSerril.
This was due to decrease in the current as a result of depletion in ion
concentration. Further, the
organic solvent DMS0 that remains in the diluate is substantially prevented
from being transported
through the membrane.
EXAMPLE 2 j
z
The Example 2 was repeated as said in the first test with the same filtered
effluent and the same ED
stack and the same membranes. Ten liters of the filtered effluent having a
conductivity of 23 mScnil
was processed through the ED stack for the transfer of salts present in the
diluate solution at an
applied voltage of 40 V. The flow rates of diluate solution concentrate
solution and rinse solution
are 293.724 L.hr-1, 309.456 L.hfland: 498.96 Lhfl respectively.
Voltage Applied: 40V
=
Table 2: Experimental data =
Time Conductivity (mScrif Voltage Current
(min) Diluate Concentrate Rinse (V) (A)
0 18.73 2.82 21.8 40 4.8
, 30 15.64 12.43 21.8 40 7.5
90 6.74 27.3 21.8 40 . 7.0
150 2.80 29.6 21.8 40 3.9
205 1.36 29.4 21.8 40 0.6
265 1.16 25.4 21.8 40 1.0
320 0.65 27.1 21,8 40 0.4
390 0.33 28.4 21.8 40 0.3
450 0.29 29.2 21.8 40 0.3
540 0.08 30 21.8 40 0.3
600 0.07 30.3 21.8 40 0.2
665 0.06 30.4 - 21.8 40 0.2
715 = 0.06 30.2 - 21.8 40 0.2
r 750 0.06 30.2 21.8 40 0.2
This trial lasted for 750 minutes. As the initial conductivity of the diluate
solution was very large in
this case also and the applied voltage was only 40 V this experiment has taken
a long time (more
than 12 hrs) to reach a final conductivity of 0.06 mScrifl.
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= EXAMPLE 3 =
This test also follows the same procedure as said in the example 2. In this
example, the initial
conductivity of the diluate solution was 18.8 mScm-1 and the applied voltage
was 60 V. The -
electrodialyiis process Was continued until the diluate 'conductivity reached
0.07 rriScm-I.
The flow rates of diluate solution concentrate solution and rinse solution are
252.72 L.hr-1, 256.608
L.hr-1 and 571.32 L.hr -I respectively. Voltage Applied: 60V =
= = =
, Table 3: Experimental data .
Time Conductivity (mSem-1) Voltage Current '
1 .
(mm) Diluate I Concentrate Rinse (V) (A) .
0 18.8 1 1.3 28.2 60 9
60 11.2 I 35.3 31.9 60 9.5 '
120 3.7 47 ___ 31.9 ___ 60 5
180 3 37 28.2 60 1.5 -
240 1.6 ' 41.6 28.8 60 0.5 =
= 300 0.5 31.6 20.8 60 0,5
370 03 , 35.1 21.8 60 0.4
420 03 35.2 , 21.8 60 0.4 .
480 02 30.5 18 60 0.4
540 0.09 32 18 60 0.3
,
615 0.08 1 31.5 17 60 0.2
. 660 0.07 1 31.7 17 60 CO
. .
. .
As the initial conductivity of the diluate solution was 18.8 mS/crn in this
case and though the applied
voltage was 60 V this experiment has taken 11 hr to reach a fmal conductivity
of 0.07 mScrn-1. In
comparison of this experiment with example 1, the observation was that the
flow rates of all the
tanks=being almost same and the applied voltage being doubled to 60 V, there
is drastic decrease in
time to reach a conductivity of 0.07 mScm-I. So it can be concluded that at a
higher voltage the
. transfer of ions is faster.
=
EXAMPLE 4 .
14 . .
. .
'
,
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This test also follows the same procedure as said in the example 2. In this
example, the .
initial conductivity of the diluate solution was 16.9 mScrn-1 and the applied
voltage was 40
V. The electradialysis process was continued until the diluate conductivity
reached 0.054
mScm-1 .
The flow rates of diluate solution concentrate solution and rinse solution are
252.72 L.hf 1, 256.,608
L.hr-1 and 571.32 L.hr-1 respectively.
. Voltage Applied: 40V
. . Table 4: Experimental data
. .
=I0 .
Time Conductivity (mScm-µ) Voltage Current
=
(min) Diluate Concentrate Rinse (V) (A)
0 16.9 0.43 27.5 40 2.5
60 , 13.56 11.78 24.8 40 6
120 ., 6.5 , .24.3 21.8 40 3.2
,
180 .., 2.4 27.9 19.8 40 1.5
240 , 1.0 28.7 19.8 40 0.7
'
300 0.56 28.5 18.5 40 0.5
330 0.56 28.5 18.5 40 0.5
390 _ 0.52 25.7 15.2 40 0.5
455 0.22 26.7 , 15 40 0.4
515 0.14 27.2 14.9 40 0.3
575 0.12 27.7 14.8 40 0.25
635 0.1 28.0 14.6 40 0.25 .
695 0.08 28.8 14.6 40 0.25
..._
750 0.08 28.8 14.6 40 0.25
-
785 0.054 28.0 14.6 40 0.25 =
In this example, though the flow rates are same as mentioned in example 3 and
a little less
conductivity of 16.9 mScm-1 and the applied voltage was 40 V, it took more
than 13 hrs to reach a
conductivity of 0.058 mScm'I. So at low voltage the transfer rate of ions is
slow.
=
'EXAMPLE 5 .
. .
"
" =
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This test also follows the same procedure as said in the example 2. In this
example, the initial
conductivity of the diluate solution was 23 mSctn'i and the applied voltage
was 40 V. The
electrodialysis process waScontinued until the diluate conductivity reached
0.054 triScrtil .
The flow rates of diluate solution concentrate solution and rinse solution are
252.72 1..hr4, 256.608
L.hil and 571.32 L.hr-1 respectively.
Voltage Applied: 40V
Table 5: Experimental data
Time Conductivity (mSenfl) Voltage Current
(min) Dituate Concentrate Rinse (V)(A)
= t
o 23 1.318 20.9 ao 49
60 17.1 6.5 21.9 40 0.6
120 16.81 7.7 22.1 40 0.6
. .
180 15.97 - ----1 1032 - 222 40 3.6
" 300 839 22.3 20 40 1.7
380 , 5,44 27.1 20 40 1.2
440 237 253 16.89 40 1
500 1.42 27.2 17.4 40 0.6
560 , 1.2 27.6 ' 15.75 40 0.6
620 0.8 28.8 16,2 40 0,5
640 0.54 29.2 16.2 40 0.4
700 0.52 29.2 16.2 40 0.6
.=
760 039 27.9 ' 14.8 40 0.3 =
0-
820 0.33 28.2 15.17 40 ' 0.3
880 0.19 28.8 15.5 40 0.3
= 940 --', 0.08 ' 29.4 15.73 40
0.25 .
.
' 1000 0,07 29.7 ' 16.3 40 0.25
1180 0.05_ 30.1 ' 17.2 40 ' 0.1 ,
.
,
=
In this example, though the flow rates and applied voltage of 40V are same as
mentioned in example
4, as. the initial conductiVity of the diluate solution is 23 mScm.-1, this
experiment has take a very
long time of more than 19 hrs to reach a conductivity of 0,05 mSem-1.
,
,
16
,
,
,
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One reason for this long time may be due to high initial conductivity of 23
mScrifl but after reaching
a conductivity of 0.54 mScm-1 the current came down to 0.4 A and to reach a
conductivity of 0.05
mScm-1 form 0.19 mScnil it almost took 3 his.
These observations of this example demonstrate the progressive decrease in the
current throughput
arising from presence of the salts in the feed stream and their transport.
This example involved unscheduled downtime and reduced process throughput with
the potential for
mechanical damage to cell hardware due to heating, meltdown etc. There is also
potential long term
= damage to the membranes as a result of heavy surface precipitation,
blistering, etc.
The cell was opened and inspected after the above experiments conducted on the
eIectrodialysis
ID stack. Except the end cation and anion exchange membranes that were
adjacent to anode and cathode
electrodes remaining membranes were in excellent condition without any
physical evidence of
fouling. The end cation and anion membrane was cloudy/ opaque and appeared to
be fouled because '
they were badly affected by the gases formed at the electrodes during the
experiment. The internal
parts of the cell were clean, because the high retention of the ions. The
precipitation problems will
undoubtedly occur with higher levels of the salt concentration present in the
feed stream, or higher
process conversions.
All the membranes were well washed with a solution containing 1 % TSP (Tri
Sodium Phosphate),
0.5 % EDTA and 0.5 % SLS (Sodium Lauryl Sulphate) in distilled water for a
long time. The
membranes were neatly wiped out and restacked without replacing any membranes.
EXAMPLE 6
This example was also performed with the same procedure as said in the above
examples. In this
example the initial conductivity of the diluate solution was 23 mScm-1 and the
applied voltage was
50 V. The electrodialysis process was continued until the diluate conductivity
reached 0.054 mScm-1.
The flow rates of dihlate solution concentrate solution and rinse solution are
324 L.hfl; 328 L.hel
and 324 L.hr.-1 flpectively.
Voltage Applied: 50V
The resultsters are as follows in Table 6.
Table 6: Experimental data
Time Diluate Concentrate , Rinse Voltage Current
(min) Conductivity pH
Conductivity pH Conductivity _ pH (V) (A)
Pumps ON 19.7 8.9 0.58 6.3 25.6 3.05
DC Power ON 50 7.5
0 = 19.2 8.85 2.0 3.83 25.2 3.02 50
7.8
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30 13.8 8.83 11.6 5.83 22.2 - 3.08 50 8.1
-
60 7.1 8.81 19.9 6.02 19.4 3.14 50 5.0
90 3.6 8.87 23.2 6.14 18.8 3.1 50 2.4
120 1.92 8.57 25.4 6.28 19.9 3.07 50 1.3
150 0.88 6.82 25.8 6.4 19.3 3.07 50 0.9
180 0.36 5.46 26.6 6.51 19.4 3.09 50 0.8
195 0.21 4.98 26.2 6.52 18.9 3.05 50 0.4
210 0.15 4.58 27.0 6.55 19.4 3.09 50 0.3
240 0.12 4.41 27.0 6.55 19.1 3.10 50 0.25
_
260 0.11 , 4.40 26.5 6.54 19.1 3.09 50 0.20
_ .
270 0.11 - -
DC OFF
= 09/05 0.74 - -
Before ED was ON
DC ON 0.36 5.19 26.0 6.32 18.54 3.14 50
0.75
290 0.21 4.98 26.0 6.25 18.7 3.14 50 0.50
310 0.09 4.6 26.1 6.22 18.3 3.06 50 0.4
340 0.07 5.54 26.1 6.2 18.26 3.13 50 0.3 ,
In this example, as initial conductivity of the diluate solution was 19.7
mScnft and the applied
voltage was 50 V, this experiment has taken 5 hr 40 min to reach a final
conductivity of 0.07 mSenfl
by operating the three solutions at same flow rates. In comparison of this
experiment with the
previous examples, the observation was that there is drastic decrease in
time to reach a conductivity
of 0.07 mScitii and also the initial current was very high at 50V voliters,
which was not observed in
the previous examples. So it can be concluded that the experiment is fetched
by the acid wash given
to the membranes.
After this experiment was over the ED stack was given tap water wash followed
by 1% HC1 wash for
about 30 min each. This is because, 1% HC1 wash for about 30 min after
every run with effluent is
fetching the experiment time and also the life of the membranes is maintained
high.
EXAMPLE 7
This example was also performed with the same procedure as said in the above
example 6. In this
example the initial conductivity of the diluate solution was 16.55 mScrtil
and the applied voltage
was 50 V. The electrodialysis process was continued until the diluate
conductivity reached 0.08
,mScm-1 The flow rates of diluate solution concentrate solution and rinse
solution are 324 L.h.(1, 328
L.hfi and 324 L.hel respectively.
Voltage Applied: 50V
The results are as follows in Table 7.
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Table 7: Experimental data
Time Diluate Concentrate Rinse Voltage Current
(min) Conductivity pH Conductivity pH Conductivity pH (V) (A)
(mScm.-.1)
Pumps ON 16.55 8.87 0.55 6.85 26.6 3.02 -
DC Power ON - - 50 8
0 16.91 - 8.82 2.51 3.52 27.2 2.98 50 8.2
30 13.21 _ 8.67 13.19 5.61 25.3 2.98 50 8.5
60 7.08 8.55 28.3 6.14 22.7 3.06_ 50 5.6
90 4.12 _ 8.22 8.70 6.39 21.7 3.10 50 3.6
120 1.72 6.07 14.41 7.20 20.8 3.10 50
1.5
150 0.50 - 5.18 16.40 7.84 20.1 3.10 _ 50
0.75
180 0.19 4.28 16.9 7.85 20.3 3.06 50 0.5
210 0.16 4.26 17.5 7.41 20.3 3.08_ 50 0.5
240 0.12 4.28 17.04 6.88 20.2 3.06 50
0.4
255 0.08 4.46 16.56 6.49 19.7 3.06 50
0.3
This experiment has take less time, 4 hr 15 min to reach final conductivity of
0.08 mScm--1 when
compared to the previous experiment of example 6, this is because in this case
the initial
conductivity of the diluate solution was less (i.e.) 16.55 mScnfl.
After this experiment was over the ED stack was given acid wash followed by 1%
WI- wash for
about 30 min each so as to make the ED stack ready for the next experiment.
EXAM:ME 8
This example was also performed with the same procedure as said in the above
examples. In this
example the initial conductivity of the diluate solution was 16.68 mScm4 and
the applied voltage
was 50 V. The electodialysis process was continued until the diluate
conductivity reached 0.07
mScnil The flow rates of diluate solution concentrate solution and rinse
solution are 324 L.hfl, 328
L.hfl and 324 L.hfl respectively.
Voltage Applied: 50V
The results are as follows in Table 8.
Table 8: Experimental data
Time Diluate Concentrate I Rinse Voltage Current
(min) Conductivity pH
Conductivity pH _Conductivity pH (V) (A)
Pumps 16.68 8.76 0.57 5.90 29.0 1.67 -
ON
DC Power 50 8.0
ON
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0 16.72 8.81 1.56 2.50 29.0 1.69 50 7.5
35 10.40 8.64 49.8 5.08 24.5 1.77 50 5.5
65 6.28 8.66 27.5 5.37 23.8 1.72 50 3.5
80 4.36 8.64 31.0 5.55 23.1 1.70 50 2.6
110 2.33 8.42 33.0 5.74 23.0 1.71 , 50 1.6
140 1.18 6.87 36.1 5.95 22.5 1.69 50 1.0
165 0.54 4.86 36.9 6.16 22.3 1.69 50 0.8
195 0.18 3.96 36.8 6.44 22.1 , 1.72 50 ' 0.5
210 0.10 . 3.73 36.3 6.41 22.1 1.74 50 0.5
, 265 0.07 3.52 37.1 6.38 21.6 1.69 = 50 0.5
This experimental result is almost similar to that of the experiment performed
in the previous
example 7, since the diluate initial conductivity, flow rates and applied
voltage are same almost and
also the time taken to reach the desired conductivity is 4 hr 25 min. So we
can say that the results are
'5 reproduced in this example which was possible due to the maintenance of
the membrane in the ED
stack.
EXAMPLE 9 = ,
This example was also performed with the same procedure as said in the above
examples. In this
example the initial conductivity of the diluate solution was 18.68 mScnfl and
the applied voltage
was 50V. The electrodialysis process was continued until the. diluate
conductivity reached 0.09
mSem=-1.
The flow rates of diluate solution concentrate solution and rinse solution are
349 L.hfl, 398 L.hfl
and 596 L.hfl. '
Voltage Applied: 50V
,
The results are as follows in Table 9.
Table 9: Experimental data
Time Diluate Concentrate Rinse
Voltage Current
(min) Conductivity pH Conductivity pH Conductivity pH (V) (A)
Pumps 18.68 8.85 2.10 7.45 26.9 2.98 - -
ON
-
DC - - - - - - 50V 9.2
'
ON
0 18.4 8.83 4.20 3.41 26.80 2.98 50 8.7
14.7 8.80 8.30 5.43 24.30 , 2.98 50 8.1
40 10.50 , 8.82 14.30 5.68 21.90 3.05 50 7.0
60 6.90 8.79 18.0 5.74 20.20 3.08 50 5.0
80 4.81 8.73 20.90 5.84 18.90 3.13 50 3.5
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100 2.90 _ 8.59 22.80 5.89 18.30 3.14
50 2.7
120 1.80 8.26 23.30 5.93 18.00 3.16 50
1.5
145 1.03 6.27 , 23.70 6.03 17.70 3.20 ' 50
1.0
180 , 0.27 4.69 24.60 6.07 17.32 3.03 50 0.5
200 0.13 4.10 24.70 6.07 17.40 3.00 50
0.45
230 0.11 3.80 24.20 6.00 17.20 2.58 50
, 0.4
240 0.09 3.80 24.40 6.00 17.08 2.58 50
0.35
In this experimental the diluate initial conductivity was 18.68 mScm-1, and
the flow rates are varied
and applied voltage is same SO V. The time taken to reach the desired
conductivity of 0.09 mScm-1 is
4 hr. Though the initial conductivity was a bit high in this experiment the
time taken to reach final
conductivity of 0.09 mScm-1 is 4 hr only. So when the flow rates are varied
the time also varies.
EXAMPLE 10 .
This example was also Vperformed with the same procedure as said in the above
examples. In this
example the initial conductivity of the diluate solution was 18.35 mScrn-1 and
the applied voltage
was 50 V. The electrodialysis process was continued until the diluate
conductivity reached 0.07
= mScnil. The flow rates of diluate solution concentrate solution and rinse
solution are 349 L.hr-1, 398 ,
= L.h11 and 596 L.hr-1.
Voltage Applied: 50V
The results are as follows in Table 10.
V Table 10: Experimental data ,
Time Diluate Concentrate Rinse Voltage Current
(min) (V) (A)
Conductivity pH Conductivity pH Conductivity pH
_
Pumps ON 18.35 9.06 2.56 7.45 30.1 2.52 - -
DC Power ON - - - - - 50V 9.0
.
0 18.3 8.96 4.9 - 29.9 2.52 50 8.8
13.0 8.96 8.9 5.26 25.2 2.52 50 7.5
40 8.7 8.87 14.2 5.44 22.9 2.52 50
5.8
60 5.7 8.55 17.4 5.54 21.7 2.51 50
4.2
80 3.2 6.64 19.9 5.64 20.4 ' 2.51 50
2.6
100 1.8 6.44 20.8 5.71 19.5 2.60 50 1.8
120 0.86 4.84 21.4 5.80 18.9 .2.60 50 1.2
140 0.32 4.09 22.3 5.82 19.0 2.50 50 0.6
160 0.17 3.88 22.4 5.88 19.3 2.54 50 0.5
180 0.15 4.06 22.9 5.83 19.2 2.55 50 0.45
190 0.12 4.00 22.4 5.80 19.3 2.58 50 0.4
210 0.10 4.00 22.3 5.77 19.0 2.58 50 0.4
21
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215 0.07 _ 4.00 22.0 5.77 18.8 2.57 50 1 0.4 I
This experimental result is almost similar to that of the experiment performed
in the previous
example 7, since the diluate initial conductivity, flowrates and applied
voltage are same and also the
time taken to reach the desired conductivity is 3 hr 35 min. So we can say
that the results of the
previous example 9 are reproduced in this example.
EXAMPLE 11
This example was also performed with the same procedure as said in the above
examples. In this
example the initial conductivity of the diluate solution was 17.14 mScm-1 and
the applied voltage
was 70 V. The electrodialysis process was continued until the diluate
conductivity reached 0.08
mScm-1. The flow rates of diluate solution concentrate solution and rinse
solution are 3241,.hr4,
328 L.hr-1 and 324 L.hr-1
Voltage Applied: 70V
The results are as follows in Table 11.
Table 11: Experimental data
Time Diluate Concentrate Rinse Voltage Current
(min) Conductivity pH Conductivity pH Conductivity _ pH (V) (A)
Pumps ON 17.14 8.67 , 0.45 5.73 26.7 1.59
DC Power - 70 9.8
ON -
0 16.85 8.73 3.02 2.17 26.7 1.59 70 9.5
30 10.63 8.51 20.6 5.09 22.9 1.66 70 7.8
105 0.42 4.22 36.0 6.05 19.2 1.80 70 1.25
135 0.16 3.29 35.6 6.01 19.3 1.72 70 0.8
155 _ 0.14 4.06 35.1 _ 5.81 19.4 1.75 70
0.6
185 0.08 3.48 35.1 5.79 19.5 1.69 70 _ 0.5
This experiment lasted for 3 hr 5 min to reach a final conductivity of 0.08
mScrifl having an initial -
conductivity of 17.14 mScrn-1. So at higher applied voltage the experiment
takes less time to reach
the desired conductivity.
However, there is always the potential for concentration polarization in the
electrodialysis cell. It
should be pointed out that the membranes should be cleaned regularly and the
cell performance
should be improved, as had been done on occasion in the laboratory which is
described in the above
discussion.
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Distillation columns are employed in many processes to obtain desired
separations. The separations
, may range from single component to the more complex multiple separations
like those performed by
crude distillation towers. Typically, a feed stream containing at least first
and second components is
supplied to the fractional distillation column. A substantial portion of the
first component contained
in the feed stream is removed from the distillation column as an overhead
product and a substantial
portion of the second component in the feed stream is removed from the
distillation process as a
¨ bottoms product. However, heat is generally supplied to the
fractional distillation column in order to
effect the desired separation or the feed may be preheated.
The invention is further illustrated by the following examples which, however,
are not intended to
limit the scope of the invention. The solutions used in the examples are
aqueous solutions.
The batch distillation set-up consists of an electrically heated 20 L still
over which mounted a 3"
glass column packed with 25 mm ceramic raschig rings. Height of the packing is
about 5". A vertical
glass condenser with tube side cooling is attached on the top. Vacuum pump is
attached to the
column to maintain required vacuum. Unit is well instrumented to maintain and
control the required
reflux ratio and reboiler and condenser temperatures.
Due to difference in capacities of the ED unit and distillation column
demonstration runs are
conducted in the following way. Each batch of ED outlet produces about 10 kg
of the diluent which
consists of about 12-15 % DMSO and remaining water along with traces of some
non-volatile heavy
organics. As the capacity of the still is 20 liters, two batches of ED diluent
is charged into the still of
the column at a time. About 90 percent of the water is removed as a distillate
and the residue, which
. is
enriched DMSO that is discharged from the still and collected. Subsequently,
another batch of 20
liters of the diluent is charged into the still and treated in the same way
and the residue is collected.
Residues thus collected from the above two steps are charged into the still
and further distilled to
obtain pure DMSO. In this step first water is removed as the first cut and
pure DMSO with allowable
of moisture content is collected as the subsequent cut. Residue left over in
the reboiler is discarded.
In short two ED runs produces the required feed for the first step of
distillation and the residue
collected from two runs of the first step of distillation produces the
required feed for the second step
of distillation.
The following examples are given by way of illustration to portray the
efficacy of the separation
characteristics of the distillation operation in separating/purifying DMSO
from DMSO-water
mixture as described in Figure 4.
EXAMPLE 12
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A batch of diluate solution of volume 20 liters weighing 20.04 kg is fed to a
packed distillation
column (2). The distillation operation is carried out under a vacuum of 30
mmHg for about 7 hrs 55
mm. A vacuum pump is used to create vacuum which is supplied to the column
through the
condenser. A vacuum seal was also used which ensures that the column is vacuum
tight. Ice is used
with vacuum seal. This is because if any of the vapors penetrates the flask,
they will be condensed,
also ensuring the material balance. The feed charged to the distillation
column contained 15.1 wt%
DMSO and the rest water. During the course of the run, the. reboiler and
overhead temperatures are
noted for every 10 min duration. The reflux ratio of 1:15 is maintained. An
additional 9.1 kg of feed
containing 14.75 wt% DMSO is added to the column after which the heating is
resumed. After
incurring a loss of 2 kg of water into vacuum seal, 17.5 kg of distillate and
9.64 kg of bottoms is
obtained. The distillate obtained is pure water whereas the bottoms collected
contain 80.15 wt%
DMSO and 19.85 wt% water. The conductivity and pH of bottoms is 0.04 mScrril
and 6.6
respectively.
Table 12: Experimental data sheet : DMSO-water distillation.
Temperature (T) , Reflux _
Pressure
Time Reboiler Overhead Ratio (mmHg)
10:05 Heating on
= 10:10 33 30.1 1:15 30
10:20 42 31.5 1:15 30
10:30 44 31.5 1:15 30
. .
10:45 41 36.1 1:15 30
11:00 47 31.4 1:15 30
, 11:17 47 30.9 1:15 30
11:30 , 47 31 1:15 30
11:45 48 31.2 _ 1:15 30
12:00 = 48 31.2 1:15 30
12:17 49 30.5 1:15 30
_
12:30 49 31.5 1:15 ' 30
_
12:45 50 31.3 1:15 = 30
13:00 51 31.5 1:15 30
13:10 52 31.5 1:15 30
13:13 51 31.4 1:15 30
14:30 42 30.8 1:15 30
14:45 - 45 31 1:15 30
15:00 46 31.1 1:15 30
15:15 48 31.3 1:15 30
15:30 49 31.3 1:15 30
15:45 50 31.4 1:15 30
16:00 51 31.4 1:15 30
16:15 52 =. 31.6 1:15 = 30
_.
24
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,
16:30 ' 52 31.6_ 1:15 30 ,
16:45 53 31.6 1:15 30 .
17:00 55 31.6 1:15 30
. 17:15 57 32.1 1:15 30
17:30 59 32 1:15 30
17:45 63 31.6 1:15 30
-
17:55 , 60 31 1:15 30
18:00 i 57 30.8 1:15 30
. .
EXAMPLE 13
A batch of diluate solution of volume 20 liters weighing 19.3 kg is fed to a
packed distillation
column (2). The distillation operation is carried out for a period of 5hrs 36
min under a vacuum of 25
mmHg. A vacuum pump and a vacuum seal are used to apply vacuum to the column.
The
composition of the feed charged is 13.32 wt% DMSO and 86.68 wt% water.
Applying a reflux ratio
of 1:15, the distillation is carried out by making note of the reboiler and
overhead temperatures and
pressure in the column at every 10 min duration. 14.3 kg of distillate of pure
water is obtained whose
conductivity and pH are 0.01 mS per cm and 5.49 respectively. The bottoms
whose conductivity and
pH are 0.06 mS/cm and 5.51 respectively, weighing 4.8 kg consisting of 77.52
wt% DMSO and
22.48 wt% water is obtained. The loss incurred in this run is 0.2 kg water.
Table 13: Experimental data sheet: DMSO-water distillation.
-
Temperature CC) Refux Pressure
Time Reboiler Overhead ratio (mmHg) _
13:15 35 31.6 1:15 25
13:30 41 20.1 1:15 25
13:45 44 31.4 1:15 25
14:00 45 29 1:15 25
14:20 45 30.2 1:15 25
14:30 45 29.8 1:15 25
14:45 45 28.7 1:15 22
15:02 45 29 1:15 23
15:16 46 31.5 1:15 25
_
15:32 46 30.4 1:15 26
15:45 46 30.1 1:15 23
16:00 46 29.9 ' 1:15 24
16:15 46 29.4 1:15 25
16:30 47 30.7 1:15 25
16:45 46 28.8 1:15 23
17:00 , 47 29.3 1:15 23
17:15 , 48 29.4 , 1:15 23
17:30 _ 49 29 1:15 23
. /-
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17:45 50 28.1 1:15 23
,
18:00 51 27.8 1:15 23
18:15 - 55 27.7 1:15 24
18:30 59 27.9 1:15 22
18:40 54 26.7 1:15 , 22
_
18:51 62 29.7 1:15 22
EXAMPLE 14
In this example, distillation was carried on a batch of diluate solution
weighing 19.54 kg as fed
containing 14.38 wt% DSMO and the rest being water for a period of 5 firs 38
min. With the help of
vacuum pump, a vacuum of about 35 mmHg is applied. By carrying out the
distillation 9peration and
noting the temperatures at the top and bottom of the column and pressure in
the column, 14.54 kg of
distillate of 100% water is obtained. The left over bottoms of 4.5 kg with
90.6 wt% DMSO and 9.4
wt % water is obtained. The conductivity of distillate and bottoms is 0.09
mScm-1 and 0.39 mScrtil-
respectively. The pH of the distillate and bottoms is 6.05 and 8.79
respectively: The loss incurred in
this run is 0.5 kg of water.
Table 14: Experimental data sheet: DMSO-water distillation.
_
Temperature ( C) Reflux Pressure
Time Reboiler Overhead ratio , (mmHg) _
_
10:52 34 28.2 1:15 35
11:02 39 30.7 1:15 35
11:15 43 33 1:15 35 -
_ 11:30 46 33.4 1:15 35
11:45 47 33.3 1:15 35
12:00 47 33.3 1:15 35 .
12:15 47 33.7 1:15 36
12:30 47 32.8 1:15 36
12:45 47 33 1:15 35
_ 13:00 48 34 .1:15 36
13:25 48 32.2 1:15 33
13:50 48 33.4 1:15 35
14:05 49 33.6 1:15 35
, 14:20 49 33.5 1:15 35
14:35 49 33.1 1:15 35
14:50 51 , 33.3 1:15 35 .
15:05 52 33 1:15 35
' 15:20 , 54 33 1:15 35 .
15:35 56 33 1:15 35
15:50 59 32.4 1:15 35
_
16:05 65 32.7 1:15 35
, 26
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,
I 16:15 71 32.9 1:15
i35
16:30 72 25.6 1:15 35
EXAMPLE 15
In this example, similar to the ones above, 18.94 kg of feed consisting of
82.89 wt% DMSO and
,17.11 wt% water is charged to a' distillation column of 20 liters capacity
wherein a vacuum of 30
mmHg is applied for about 150 min. Similar to the above examples, the reboiler
and overhead
temperatures and pressure in the column are noted at every 10 min. After 100
min of operation the
reflux ratio was changed from 1:15 to 1:5. This experiment yielded in
distillate of 3.84 kg and
bottoms of 14.94 kg. The distillate recorded the conductivity of 0.14 mScrn4
and bottoms recorded
8.7 mScnfl whereas the pH of distillate and bottoms is 6.6 and 0.17
respectively. There has been a
loss of 0.16 kg of water. The distillate consists of 97.13 wt% DMSO and 2.087
wt% water.
Table 15: Experimental data sheet: DMSO-water distillation.
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
_
17:15 53 24 1:15 30
_
17:25 56 30.1 1:15 30
_
17:30 59 30.4 1:15 30
17:40 67 31.4 1:15 30
-
17:55 73 32.1 1:15 33
- -
18:40 89 35.8 1:15 36
18:50 81 31.6 , 1:15 30
18:55 81 29.1 1:5 25
19:00 83 - 27.7 1:5 23
19:10 87 27.9 , 1:5 21
19:15 90 29.9 1:5 21
19:20 92 36.3 1:5 26 .
19:25 95 47.3 1:5 .
19:30 97 63.1 1:5 24
, .
19:40 94 72.7 1:5 24
_
19:45 90 71.6 1:5 26
'
The reflux ratio is varied from 1:15 to 1:5 to achieve high purity of both
distillate and residue
15 depending upon composition in the re-boiler.
,
EXAMPLE 16 '
27
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In this example, 14.94 kg of composite bottoms obtained from above examples of
1 stage distillation
operation is charged into a rotavapor which has the capacity to hold 10 liters
of solution. The
conductivity and pH of the feed is 0.01 mScm-1 and 8.0 respectively. The feed
consisting of 97 %
DMSO is fed to the re-boiler and distillation is carried out for 2 hrs 48 mm
during which the pressure
and temperatures in the column are noted using digital meter. The intermediate
cut obtained which
weighed 1.14 kg consisted of 78.69% DMSO and 21.309%water. The distillate and
bottoms obtained
were pure water and pure DMSO which weighed 9.9 kg and 3.3 kg respectively.
There had been a
loss of 0.6 kg of water into the vacuum seal.
The conductivity of distillate (water) 0.003 mScnil and pH of 7.12 and that of
bottomSconductivity
and pH is 0.58 mScm-land 9.63 respectively.
Table 16: Experimental data sheet: DMSO-water distillation.
Temperature CC) Reflux Pressure
Time , Reboiler Overhead Ratio (mmHg) ,
12:12 43 38.4 1:5 20
12:22 54 38 1:5 16
12:30 78 37.8 1:5 22
12:45 100 60.3 1:5 26
13:00 114 79.6 1:5 22
13:05 120 81.4 = 1:15 24 _
13:10 124 83.8 1:15 24
13:15 118 93.5 1:15 26
13:30 118 94.8 , 1:15 30
13:40 122 95.8 1:15 30
13:50 126 97 1:15 31
14:00 128 98 1:15 33
-
14:08 129 95 1:15 33
14:18 116 95.4 1:15 29
14:30 115 92.4 1:15 25
14:42 121 96.4 1:15 30
14:52 106 85.5 1:15 18
15:00 102 75.3 1:15 20 =
= The reflux ratio is varied depending upon composition in the reboiler.
EXAMPLE 17
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The feed solution of 20 liters volume weighing 18.04 kg is fed to a packed
distillation column to
which a vacuum of 30 mmHg is applied for about 5 hrs 55 min. The feed charged
consists of 11.52
wt% DMSO and 88.48 wt% water which had a conductivity of 0.08 mS/cm and pH of
5.38. The
reflux ratio of 1:15 is applied and temperatures at the top and bottom of the
column are noted . This
distillation experiment resulted in 13.24 kg of distillate which had 1.06 wt%
DMSO and 98.94 wt%
water and 4.4 kg of bottoms which consisted of 81.15 wt%DMS0 and the rest
being water. The
conductivity of distillate and bottoms is 0.06 mScm-1 and 6.38 mScm'l
respectively. The pH of the
distillate and bottoms is 8.14 and 0.04 respectively. This run had a loss of
0.4 kg of water.
Table 17: Experimental data sheet: DMSO-water distillation.
t
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio mm of lig
. 11:25 32 47.9 , 1:15 , 30
11:30 34 47.9 1:15 30
_
.
' 11:45 41 35 1:15 30
12:00 _ 44 , 30.5 1:15 24
12:15 44 31.5 1:15 30
12:30 45 32.1 1:15 30
_
12:45 45 31.5 1:15 30
1 13:00 46 32.1 1:15 30
_ 13:15 47 33 1:15 30 ,
13:30 47 31 1:15 27
13:45 47 31.7 1:15 30
-
14:00 47 31.6 1:15 30
_
14:15 48 31.9 1:15 30 .
_
14:30 47 31.3 1:15 30
14:49 53 31.6 1:15 30
15:07 _ 51 33 1:15 30
15:15 51 31.7 1:15 30
15:55 73 35.3 1:15 30
16:00 52 31.5 , 1:15 30
16:15 - 49 , 31.3 1:15 30
16:30 52 31.9 1:15 30
16:45 57 31.7 1:15 30
17:00 61 31.6 1:15 _ 30 ,
17:12 66 31.6 1:15 30
17:20 66 29.5 1:15 30
,
EXAMPLE 18
= =
A batch of diluate solution of volume of about 20 liters weighing 21.04 kg is
fed to a packed
distillation column. The distillation operation is carried out for a period of
5hrs 28 min under a
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vacuum of 25 mmHg. A vacuum pump and a vacuum seal are used to apply vacuum to
the column.
The composition of the feed charged is 16.32 wt% DMSO and .83.68 wt% water.
Applying a reflux
ratio of 1:15, the distillation is carried out by making note of the reboiler
and overhead temperatures
and pressure in the column at every 10 min duration. 15.14 kg of distillate of
pure water is obtained
whose conductivity and pH are 0.01 mScm-1 and 5.52 respectively. The bottoms
whose conducitivity
and pH are 0.03 mScm-I and 6.92 mScm'l respectively, weighing 5.7 kg
consisting of 70.14 wt%
DMSO and 29.86 wt% water is obtained. The loss incurred in this run is the
loss of 0.2 kg water.
Table 18: Experimental data sheet DMSO-water distillation.
Temperature CC) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
10:10 ' 33 30.5 1:15 30
10:20 - 39 30.1 1:15 30
10:30 - 43 31.1 1:15 30
10:45 45 . 31.7 1:15 30
11:00 46 30 1:15 25
11:15 46 29.7 - 1:15 25
11:30 46 29.5 1:15 25
11:45 46 30.2 1:15 25
11:50 44 30 1:15 25
12:10 - 46 30.2 1:15 25
12:30 47 29.7 1:15 25
12:45 47 29.7 1:15 25
13:00 49 32.4 1:15 25
13:20 48 30 1:15 25
13:30 48 30,2 1:15 25
13:45 48 29.9 1:15 - 25
14:00 49 29.7 1:15 25
14:15 50 29.3 1:15 23
- 14:30 50 28.9 1:15 22
- 14:45 52 29.7 1:15 23
15:00 53 29 1:15 27
15:15 55 28.6 1:15 23
=
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1 15:30 60 I 29 1 1:15 1 23
__________________________________________________________ 1
EXAMPLE 19
In this example, similar to the ones above, 18.74 kg of feed consisting of
13.13 wt% DMSO and
. 86.86 wt% water is charged to a distillation column of 20 liters capacity
wherein a vacuum of 25
mmHg is applied for about 7 hrs. Similar to the above examples, the reboiler
and overhead
temperatures and pressure in the column are noted at every 10 min. This
experiment yielded in a
distillate of 14.14 kg and bottoms of 4.14 kg. The distillate recorded the
conductivity of 0.11 mScrh-1
and bottoms recorded 0.6 mScm.-I whereas the pH of distillate and bottoms is
6.94 and 8.75
respectively. There has been a loss of 0.46 kg of water. The distillate
consists of 0.92 wt% DMSO
and 99.08 wt% water.
Table 19: Experimental data sheet: DMSO-water distillation.
Temperature ( C) Reflux Pressure
mm of
Reboiler Overhead Ratio Hg
' 10:30 33 30.3 1:15 , 20
10:45 38 26.1 1:15 24
11:00 43 29.5 1:15 25
11:03 45 31.2 1:15 25
11:15 44 29.3 1:15 . 24
'
11:30 45 29.6 1:15 25
11:40 48 32.6 1:15 25
12:00 37 26.9 1:15 23
12:15 42 30.8 1:15 28
12:30 45 30.3 1:15 25 _
12:45 46 29.2 1:15 23
13:00..47 30 1:15 23
13:30 49 29.5 1:15 24
13:45 49 29.5 1:15 23
14:00 49 29.4 1:15 23 -
14:15 49 29.4 1:15 23
14:30 49 29 1:15 23
14:45 50 28.6 1:15 22
15:00 52 30.5 1:15 24
15:15 53 28.1 1:15 23
15:30 56 30.1 1:15 23
15:45 59 28.9 1:15 23
16:40 -,,67 33.5 1:15 25
31
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17:00 62 29.4 1:15 25
17:10 70 29.4 1:15 25
17:20 77 29.1 1:15 25
17:30 79 27.3 1:15 23
EXAMPLE 20
The feed solution of about 20 liters of volume weighing 19.34 kg is fed to a
packed distillation
column to which a vacuum of 25 mmHg is applied for about 6 hrs 45 min. The
feed charged consists
of '13.05 Wt% DMSO and 86.25 %water. The reflux ratio of 1:15 is applied and
temperatures at the.
top and bottom of the column are noted. This distillation experiment resulted
in 14.14 kg of distillate
which had pure water and 4.84 kg of bottoms which consisted of 75.15%DMS0 and
the rest being
water. The conductivity of distillate and bottoms is 0.16 mScm'l and 0.54 mScm
-I respectively. The
pH of the distillate and bottoms is 6.43 and 7.96 respectively. This run had a
loss of 0.36 kg of water.
Table 20: Experimental data sheet: DMSO-water distillation.
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
10:15 33 29.1 1:15 27
10:32 39 29.5 1:15 25
10:45 44 34.3 1:15 27
10:51 46 29.9 1:15 25
11:00 43 29.1 1:15 27
11:15 43 29.7 1:15 25
11:30 45 29.6 1:15 25
11:45 46 29.3 1:15 25
12:00 46 29.8 - 1:15 25
12:15 49 33.6 1:15 35
12:30 47 28.9 1:15 25
12:45 45 30.1 1:15 25
13:00 47 30.2 1:15 26,
13:15 49 30.9 1:15 26
13:30 49 30.6 1:15 25
13:45 51 30.4 1:15 25
14:00 47 28.3 1:15 24
32
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14:15 49 29 1:15. 23
14:30 49 28.9 1:15 23
14:45 49 29.4 1:15 25
15:00 50 29.8 1:15 25
15:15 51 29 1:15 24
16:00 50 28.6 1:15 24
16:15 51 28 1:15 25
16:30 55 28.5 1:15 25
16:45 61 29.2 1:15 25
16:50 62 29.3 1:15 25
17:00 - 60 27.8 - 1:15 25
EXAMPLE 21
This example consists of feeding 9.84 kg of desalted solution to rotavapor
wherein a vacuum of 25
mmHg is applied. The feed consists of 78.46 wt% DMSO and 21.54 wt% water. The
total operation
took 75 min to complete during which the temperature across the column and
pressure in the column
is noted. The reflux ratio maintained was 1:5. This run yielded 2.24 kg of
pure water as distillate.
The weight of bottoms obtained is 7.44 kg which consisted of 96.94 wt% DMSO
and 3.06 wt%
water. The weight of material lost is 0.16 kg. The conductivities of
distillate and'bottoms is 0.01
mScrn*-1 and 8.45 mScrn -1 respectively. The pH of distillate and bottoms is
6.14 and 0.07
respectively.
Table 21: Experimental data sheet: DMSO-water distillation.
Temperature (t) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
10:00 60 29.6 1:5 25
10:15 63 29 1:5 25
10:30 70 29.7 1:5 25
10:45 77 =29.9 1:5 27
11:15 103 27.1 1:5 27 * =
The reflux ratio is maintained constant at 1:5.
EXAMPLE 22
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In this example, similar to the ones above, 8.84 kg of feed consisting of
84.13 wt% DMSO and 15.87
wt% water is charged to a distillation column of 10 liters capacity wherein a
vacuum of 25 mmHg is
applied for about 150 mm. Similar to the above examples, the reboiler and
overhead .temperatures
and pressure in the column are noted at every 10 min. This experiment yielded
in. a distillate of 1.14
kg of pure water and bottoms of 7.6 kg. The distillate recorded the
conductivity of 0.12 mS/cm and
bottoms recorded 0.67 mS/cm whereas the pH of distillate and bottoms is 5.76
and 9.56 respectively.
There has been a loss of 0.1 kg of water. The bottoms consist of 98.66 wt%
DMSO and 1.34 wt%
water.
Table 22: Experimental data sheet: DMSO-water distillation.
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio ¨ (mmHg)
14:50 45 35.5 1:15 25
15:05 60 33.2 1:15 25 '
15:15 73 32.3 1:15 27
15:30 91 33.3 1:15 25
15:40 78 31.7 1:5 30
15:55 82 33.3 1:5 30
16:00 80 31.7 1:5 22
16:10 80 28.1 1:5 22
16:20 93 38 1:5 22
The reflux ratio is varied from 1:15 to 1:5 depending on reboiler composition.
EXAMPLE 23
In this example, the feed of weight 7.44 kg is charged into a rota vapor of 10
liters capacity wherein
a vacuum of 25 mmHg is applied for about 3 hrs. The feed contains about 96.94%
DMSO and the
rest being water. Similar to the above examples, the reboiler and overhead
temperatures and pressure
in the column are noted at every 10 min. The refhtx ratio was maintained
constant at 5:1. During
distillation, traces of water is removed as the first cut of the distillate.
Most of the DMSO with
permissible moisture content, which is colorless, is recovered as second cut
of the distillation.
Residue left over in the reboiler is discarded. The composition of DMSO in the
first and second cuts
is 90.67% and 99.43% respectively. The distillate of 4.63 kg and bottoms of
2.34 kg reported the
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DMSO levels of 99.17% and 98.41% respectively. The distillate recorded the
conductivity of 0.007
mScm-i and bottoms recorded 0.98 mScm-1 whereas the pH of distillate and
bottoms is 9.46 and
9.56 respectively. There has been a loss of 0.47 kg of water.
Since the feed is rich in DMSO, there arose a need for withdrawing various
cuts at different stages of
distillation operation before pure components are obtained.
Table 23t Experimental data sheet: DMSO distillation.
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
11:45 43 38.1 5:1 28
12:00 63 37.6 5:1 39
12:15 110 53.2 5:1 20
12:40 130 80 - 5:1 20
12:45 . 122 82.1 - 5:1 20
12:47 113 92.4 5:1 25
12:50 111 93.4 - 5:1 27
13:00 118 93.6 5:1 25
13:10 121 93.8 5:1 - 25
13:16 112 91.6 5:1 20
13:50 95 64.1 5:1 23
The reflux ratio is maintained constant at 5:1 for desirable purity of
distillate, which is the final
DMSO product.
EXAMPLE 24
The feed solution of about 10 liters of volume weighing 7.6 kg of composition
98.66 wt% DMSO
and 1.34 wt% water is fed to a rotating type distillation column to which a
vacuum of 30 trimHg is
applied for about 85 min. The reflux ratio of 1:5 is applied and temperatures
at the top and bottom of
the column are noted. This distillation experiment resulted in 4.25 kg of pure
water as distillate after
withdrawing first cut which consisted of 64.78 wt% DMSO. About 3.33 kg of pure
DMSO is
obtained as the bottom product. This run had a loss of 0.02 kg of water.
Table 24: Experimental data sheet: DMSO-water distillation.
Temperature ( C) Reflux Pressure
Time Reboiler Overhead Ratio - (mmHg)
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14:45 46 44.1 25
15:05 97 32.6 1:05 22
15:15 113 37.9 1:05 25
15:20 126 88 1:05 32
15:25 128 90.6 1:05 32
15:27 130 88.3 1:05 30
15:30 132 85.5 1:05 29
15:32 129 103.4 1:05 27
15:34 124 93.9 1:05 27 =
15:36 116 90.2 1:05 27
15:45 116 90.3 1:05 27
15:50 119 90.9 1:05 27
15:52 119 94.4 1:05 30
15:55 119 96 1:05 - 31
16:00 119 94.9 1:05 30
16:05 - 120 91.4 1:05 25
16:10 120 91.4 1 : 05 - 25
EXAMPLE 25
The feed solution weighing 8.97 kg of composition 99.25 wt% DMSO and 0.75%
water is fed to a
rotating type distillation column to which a vacuum of 30 mmHg is applied for
about 95 min. The
reflux ratio of 1:15 is applied and temperatures at the top and bottom of the
column are noted. This
distillation experiment resulted in 6 kg of pure water as distillate after
withdrawing first cut which
consisted of 95.72%DMSO. About 2.84 kg of pure DMSO is obtained as the bottom
product. This
run had a loss of 0.13 kg of water. The conductivity, pH of distillate and
bottom are 0.031 inScm
7.15 and 9.61 mScm-1, 1.58 respectively.
table 25: Experimental data sheet: DMSO-water distillation.
Temperature CC) Reflux Pressure
Time Reboiler Overhead Ratio (mmHg)
11:10 1:15
11:15 33 31.2 1:15 30
11:30 100 31.5 1:15 30
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11:45 122 87.9 1:15 23
12:00 119 95.7 1:15 30
12:15 124 94.8 1:15 28
12:30 - 121 94.8 1:15 30
12:45 120 95.8 1:15 30
The overall material balance for a four ED runs and subsequent distillations
carried out is presented
=
in the Figure 8.
DMSO RECOVERY
The water recovered during distillation has shown traces of volatiles and its
utility has to be explored
by the client. Inter-cut (DMSO rich) from second distillation can be recovered
and added to the next
batch of second distillation. All the remaining residues from the trials were
mixed and taken for
further DMSO recovery to study the overall recovery of DMSO. During the
demonstration,
approximately 25 kg of pure DMSO from a total diluate of 180 kg was recovered
which indicates
0.14 kg (89.33%) DMSO recovery was estimated. The final residue comprising
mostly of unknown
color imparting organics is to be discarded after DMSO recovery.
Chosen cation-exchange membrane (CMI-7000) and anion-exchange membrane (AMI-
7001) has
excellent chemical resistance to DMSO. =
The technical specifications of the CMI-7000 cation exchange membrane are
given in Table 26
Table 26: Technical Specifications of the CMI-7000 cation exchange membrane.
Functionality Strong Acid Cation Exchange Membrane
= Gel polystyerene cross linked with divinyl
Polymer Structure benzene
Functional group Sulphonic acid
Electrical resistance(Ohm cm-2)
0.5 mol NaCI <30
Permselectivity(0.5 mol NaClkg-1).(1.0
mol KCIkg-1)-1 94
Total Exchange Capacity(meq 1.3 0.1
Water Permeability(ml.hr1ft-2) @5psi <10
=37
CA 02779656 2012-05-02
WO 2011/055381 PCT/1N2010/000708
FThermal Stability (degree. C) 90
Chemical Stability Range (pH) 1-10 =
The technical specifications of the A11H-7001 anion exchange membrane are
given in Table 27.
=
Table 27: Technical Specifications of the AMI-7001 anion exchange membrane.
_ ______________________________________________________________________
Functionality Strong Acid Anion Exchange Membrane
Gel polystyerene cross linked with divinyl
Polymer Structure benzene '
Functional group Quaternary Ammonium
Electrical resistance(Ohm cm-2)
0.5 mol L1 NaC1 <40
Permselectivity(0.5 mol NaC1 kg -1).(1.0
mol KCI kg4).-1 90
Total Exchange Capacity(meq g') 1.0-10.1
_
Water Permeability(ml.he4ft-2) @5psi <10
Thermal Stability (degree. C) 90
Chemical Stability Range (pH) 1-10
,
ADVANTAGES OF THE INVENTION:
The developed process facilitates the recovery of DMS0 solvent from a
pharmaceutical effluent
through separation of hazardous compounds such as sodium azide. The process
also reduces the load
on the effluent treatment plant (ETP) which would otherwise have to undergo
extensive procedures
- 10 for neutralization of sodium azide and reduction in chemical oxygen
demand (COD). High recovery
of DMSO with high purity is possible through the developed process.
,
38
