U.S. patent application number 12/550990 was filed with the patent office on 2011-03-03 for reverse osmosis composite membranes for boron removal.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Lawrence Charles Costa, Jiang Ji, Michael Todd Luttrell, David Allen Olson, Joseph Anthony Suriano, Hua Wang, Gary William Yeager.
Application Number | 20110049055 12/550990 |
Document ID | / |
Family ID | 42712452 |
Filed Date | 2011-03-03 |
United States Patent
Application |
20110049055 |
Kind Code |
A1 |
Wang; Hua ; et al. |
March 3, 2011 |
REVERSE OSMOSIS COMPOSITE MEMBRANES FOR BORON REMOVAL
Abstract
Improved methods for reducing boron concentration in seawater or
brackish water, while simultaneously maintaining or improving the
salt rejection of membrane and flow performance of polyamide
reverse osmosis (RO) membranes include contacting the water with a
composite membrane comprising moieties derived from an aromatic
sulfonyl halide, a heteroaromatic sulfonyl halide, a sulfinyl
halide; a sulfenyl halide; a sulfuryl halide; a phosphoryl halide;
a phosphonyl halide; a phosphinyl halide; a thiophosphoryl halide;
a thiophosphonyl halide, an isocyanate, a urea, a cyanate, an
aromatic carbonyl halide, an epoxide or a mixture thereof.
Inventors: |
Wang; Hua; (Clifton Park,
NY) ; Olson; David Allen; (Minneapolis, MN) ;
Ji; Jiang; (North Billerica, MA) ; Luttrell; Michael
Todd; (Clifton Park, NY) ; Yeager; Gary William;
(Rexford, NY) ; Suriano; Joseph Anthony; (Clifton
Park, NY) ; Costa; Lawrence Charles; (Mansfield,
MA) |
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
42712452 |
Appl. No.: |
12/550990 |
Filed: |
August 31, 2009 |
Current U.S.
Class: |
210/654 ;
210/500.21; 210/500.27; 427/337; 528/332 |
Current CPC
Class: |
C02F 2103/08 20130101;
C02F 2101/108 20130101; C02F 1/441 20130101; Y02A 20/131
20180101 |
Class at
Publication: |
210/654 ;
210/500.21; 210/500.27; 528/332; 427/337 |
International
Class: |
C02F 1/44 20060101
C02F001/44; B01D 65/00 20060101 B01D065/00; B01D 71/06 20060101
B01D071/06; B05D 3/10 20060101 B05D003/10 |
Claims
1. A reverse osmosis method for reducing boron concentration in
water containing boron, said reverse osmosis method comprising
contacting the water with a composite membrane comprising moieties
derived from an aromatic sulfonyl halide, a heteroaromatic sulfonyl
halide, a sulfinyl halide; a sulfenyl halide; a sulfuryl halide; a
phosphoryl halide; a phosphonyl halide; a phosphinyl halide; a
thiophosphoryl halide; a thiophosphonyl halide, an isocyanate, a
urea, a cyanate, an aromatic carbonyl halide, an epoxide or a
mixture thereof.
2. A reverse osmosis method according to claim 1, wherein the
moieties are derived from an aromatic sulfonyl halide.
3. A reverse osmosis method according to claim 1, wherein the
moieties are derived from 4-nitrobenzenesulfonyl chloride.
4. A reverse osmosis method according to claim 1, wherein the
moieties are derived from 1,3-benzenedisulfonyl chloride.
5. A reverse osmosis method according to claim 1, wherein the
moieties are derived from 4-cyano benzenesulfonyl chloride.
6. A reverse osmosis method according to claim 1, wherein the
composite membrane additionally comprises a cross-linked
hydrophilic polymer.
7. A reverse osmosis method according to claim 6, wherein the
cross-linked hydrophilic polymer is polyvinyl alcohol.
8. A method for preparing a composite membrane comprising
contacting under interfacial polymerization conditions an organic
solution comprising a polyacid halide with an aqueous solution
comprising a polyamine to form a polyamide membrane, said
contacting being carried out on a surface of a porous base
membrane, said organic solution further comprising an aryl sulfonyl
halide.
9. A method according to claim 8, wherein the organic solution
additionally comprises a C.sub.3-C.sub.8 cyclic carbonyl
compound.
10. A method according to claim 9, wherein the C.sub.3-C.sub.8
cyclic carbonyl compound is cyclohexanone.
11. A method according to claim 8, additionally comprising
contacting the polyamide membrane with an oxidizing solution, such
as sodium hypochlorite.
12. A method according to claim 11, wherein the concentration of
free chlorine in the sodium hypochlorite solution ranges from about
10 ppm to about 4000 ppm.
13. A method according to claim 8, wherein the aryl sulfonyl halide
is present in an amount ranging from about 0.01% to about 2% by
weight.
14. A method according to claim 8, wherein the aryl sulfonyl halide
is 1,3-benzenedisulfonyl chloride or 1,3,6-naphthalenetrisulfonyl
chloride
15. A composite membrane prepared by the method of claim 8.
16. A reverse osmosis method for reducing boron concentration in
water containing boron, said reverse osmosis method comprising
contacting the water with a composite membrane comprising moieties
derived from an aromatic sulfonyl halide, a heteroaromatic sulfonyl
halide, a sulfinyl halide; a sulfenyl halide; a sulfuryl halide; a
phosphoryl halide; a phosphonyl halide; a phosphinyl halide; a
thiophosphoryl halide; a thiophosphonyl halide, an isocyanate, a
urea, a cyanate, an aromatic carbonyl halide, an epoxide or a
mixture thereof, wherein the composite membrane is prepared by
contacting under interfacial polymerization conditions an organic
solution comprising a polyacid halide with an aqueous solution
comprising a polyamine to form a polyamide membrane and contacting
the polyamide membrane with an oxidizing solution; said contacting
being carried out on a surface of a porous base membrane, said
organic solution further comprising a C.sub.3-C.sub.8 cyclic
carbonyl compound and an aryl sulfonyl halide.
17. A reverse osmosis method according to claim 16, wherein the
oxidizing solution is a sodium hypochlorite solution.
Description
BACKGROUND
[0001] Reverse osmosis (RO) membrane desalination uses membrane
technology to transform seawater and brackish water into fresh
water for drinking, irrigation, and industrial applications. Such
processes require substantially less energy than do thermal
desalination processes such as multi-stage flash, and so, reverse
osmosis membrane technology is increasingly used to produce fresh
water from seawater or brackish water.
[0002] Reverse osmosis is the process of forcing a solvent from a
region of high solute concentration through a membrane to a region
of low solute concentration by applying a pressure in excess of the
osmotic pressure. This is the reverse of an osmosis process, which
is the natural movement of solvent from an area of low solute
concentration, through a membrane, to an area of high solute
concentration when no external pressure is applied. The membrane
here is semipermeable, meaning it allows the passage of solvent but
not of solute. The membranes used for reverse osmosis have a dense
barrier layer in the polymer matrix where most separation occurs.
The membrane is designed to allow only water to pass through this
dense layer while preventing the passage of solutes such as salts.
The reverse osmosis process requires that a high pressure be
exerted on the high concentration side of the membrane, usually
2-17 bar (30-250 psi) for fresh and brackish water, and 40-70 bar
(600-1000 psi) for seawater, which has around 24 bar (350 psi)
natural osmotic pressure which must be overcome.
[0003] Over the years, better membrane technologies and energy
recovery devices have made reverse osmosis more affordable and
efficient. However, the RO process has not been very effective in
the removal of neutral contaminants such as boron despite its
capacity to efficiently remove up to 99.7% of ionic species.
[0004] Seawater in general has a boron concentration of 4 to 5
mg/L. Depending on location and seasonal effects, the boron
concentration can reach up to 7 mg/L, e.g. in the Arabian Gulf.
Toxicological effects of human exposure to excess boron, mostly
reproductive and developmental, are well documented. Excess boron
also harmful to plant growth; deleterious effects include massive
leaf damages, premature ripening, and reduced crop yields.
[0005] In aqueous environments, at acidic and neutral pH, boron is
mainly present as undissociated boric acid. Reverse osmosis
membrane is better at removing charged species over uncharged
species due to the larger apparent size of hydrated charged
species. Uncharged boric acid has a molecular diameter of 2.75
.ANG. and a molecular volume of 71.5 .ANG..sup.3, which is similar
to urea (75.3 .ANG..sup.3) and other small nonelectrolytes. Thus,
boric acid is significantly smaller than hydrated sodium (3.58
.ANG.) and chloride (3.32 .ANG.) ions, making the removal of boron
significantly more difficult than sodium chloride salt.
[0006] Thin films of cross-linked aromatic polyamide RO membranes
are typically composed of two types of pores, network pores having
radii of about 1-3 .ANG., and aggregate pores, having radii of
about 3.5-4.5 .ANG.. The radius of uncharged boric acid (2.75
.ANG.) is close to that of the network pores and substantially less
than that of the aggregated pores. As a result, it is difficult for
a RO membrane desalination process to achieve an average boron
rejection over 90%, which is typically required to produce a
permeate that meets the requirements of the many applications. This
has led to the adoption of procedures such as repeating the RO
membrane treatment process twice, or mixing treated water with low
boron concentration water from other sources. Although these
additional treatment steps lead to reduced boron concentration,
they increase costs substantially.
[0007] In recent years, specialized seawater reverse osmosis (SWRO)
membranes for boron removal have been introduced. However, even
with these membranes, it has been difficult for a single-pass
full-scale RO process to reduce the boron level to below 0.5 mg/L,
while achieving required system recovery, unless an additional
treatment step is employed. For example, the SWRO plant in
Ashkelon, Israel, uses a 4-stage cascade RO design to meet a boron
specification of <0.3 mg/L. U.S. Pat. No. 7,279,097, assigned to
Toray Industries Inc., discloses a method of treating reverse
osmosis membranes with aliphatic amines and aliphatic acid halide
for improving boron rejection of the membranes. Aliphatic acid
halides disclosed include "methanesulfonyl chloride, acetyl
chloride, propionyl chloride, butyryl chloride, oxalyl chloride,
malonic acid dichloride, succinic acid dichloride, maleic acid
dichloride, fumaric acid dichloride, chlorosulfonylacetyl chloride,
and N,N-dimethylaminocarbonyl chloride". However, there remains a
need for even better methods for making new seawater and brackish
membrane products with high boron rejection and salt rejection
performance.
BRIEF DESCRIPTION
[0008] The present invention relates to improved methods for
reducing boron concentration and improving flow performance of
polyamide reverse osmosis (RO) membranes, while simultaneously
maintaining or improving the salt rejection of membrane
[0009] Briefly, in one aspect, the present invention relates to
reverse osmosis methods for reducing boron concentration in water
containing boron, the method comprising contacting the water with a
composite membrane comprising moieties derived from an aromatic
sulfonyl halide, a heteroaromatic sulfonyl halide, a sulfinyl
halide; a sulfenyl halide; a sulfuryl halide; a phosphoryl halide;
a phosphonyl halide; a phosphinyl halide; a thiophosphoryl halide;
a thiophosphonyl halide, an isocyanate, a urea, a cyanate, an
aromatic carbonyl halide, an epoxide or a mixture thereof.
[0010] In another aspect, the present invention relates to reverse
osmosis methods for preparing a composite membrane by contacting
under interfacial polymerization conditions an organic solution
comprising a polyacid halide with an aqueous solution that includes
a polyamine to form a polyamide membrane. The contacting step is
carried out on a surface of a porous base membrane, and the organic
solution further includes an aryl sulfonyl halide. The composite
membranes so prepared may be used for reducing boron concentration,
and typically display good boron rejection performance.
DETAILED DESCRIPTION
[0011] The present invention relates to reverse osmosis methods for
reducing boron concentration in seawater or brackish water
containing at least 5 ppm boron, in a single step, by at least 90%,
preferably by at least 95% in a single step, and more preferably by
at least 96% in a single step. pH of the water is typically less
than or equal to about 8.5. Reverse osmosis processes are typically
operated at pressures ranging from 2-17 bar (30-250 psi) for fresh
and brackish water, and 40-70 bar (600-1000 psi) for seawater.
[0012] In the reverse osmosis methods of the present invention, the
seawater or brackish water is treated, by contacting it with a
composite membrane comprising moieties derived from an aromatic
sulfonyl halide, a heteroaromatic sulfonyl halide, a sulfinyl
halide; a sulfenyl halide; a sulfuryl halide; a phosphoryl halide;
a phosphonyl halide; a phosphinyl halide; a thiophosphoryl halide;
a thiophosphonyl halide, an isocyanate, a urea, a cyanate, an
aromatic carbonyl halide, an epoxide or a mixture thereof. In some
embodiments, the moieties are derived from an aromatic sulfonyl
halide, particularly 4-nitrobenzenesulfonyl chloride,
1,3-benzenedisulfonyl chloride, or 4-cyano benzenesulfonyl
chloride. The composite membrane may additionally include an
additional layer of cross-linked hydrophilic polymer such as
polyvinyl alcohol (PVA) coated on the separating layer.
[0013] The term "composite membrane" refers to thin film composite
(TFC) semipermeable membranes composed of a separating functional
layer formed on a porous substrate film. The separating functional
layer is thin in order to maximize membrane flux performance, and
is formed on a porous support or base membrane to provide
mechanical strength. Examples of TFC membranes that may be used in
the methods of the present invention include, but are not limited
to, reverse osmosis membranes composed of a polyamide separating
functional layer formed on a porous polysulfone support,
nanofiltration membranes, and other thin film composite
membrane.
[0014] The composite membranes for use in the reverse osmosis
methods of the present invention may be prepared by post-treatment
of a TFC membrane, particularly a polyamide TFC membrane with an
aromatic sulfonyl halide, a heteroaromatic sulfonyl halide, a
sulfinyl halide; a sulfenyl halide; a sulfuryl halide; a phosphoryl
halide; a phosphonyl halide; a phosphinyl halide; a thiophosphoryl
halide; a thiophosphonyl halide, an isocyanate, a urea, a cyanate,
an aromatic carbonyl halide, and/or an epoxide.
[0015] Alternately, the composite membranes may be prepared by
in-situ reaction of the same compounds during fabrication of the
membrane by interfacial polymerization. Accordingly, in another
aspect, the present invention relates to reverse osmosis methods
for preparing a composite membrane that may be used in methods for
reducing boron concentration. An organic solution including a
polyacid halide is contacted under interfacial polymerization
conditions, on a surface of a porous base membrane, with an aqueous
solution including a polyamine to form a polyamide membrane. The
organic solution further includes an aryl sulfonyl halide,
heteroaromatic sulfonyl halide, a sulfinyl halide; a sulfenyl
halide; a sulfuryl halide; a phosphoryl halide; a phosphonyl
halide; a phosphinyl halide; a thiophosphoryl halide; a
thiophosphonyl halide, an isocyanate, a urea, a cyanate, an
aromatic carbonyl halide, an epoxide, or a mixture thereof,
preferably an aryl sulfonyl halide, more preferably
1,3-benzenedisulfonyl chloride or 1,3,6-naphthalenetrisulfonyl
chloride. The aryl sulfonyl halide may be present in an amount
ranging from about 0.01% to about 2% by weight.
[0016] The organic solution may additionally include a
C.sub.3-C.sub.8 cyclic carbonyl compound. The C.sub.3-C.sub.8
cyclic carbonyl compound may be a cyclic ketone having from three
to eight carbon atoms for example cyclooctanone, cycloheptanone,
2-methylcyclohexanone, cyclohexanone, cyclohexene-3-one,
cyclopentanone, cyclobutanone, 3-ketotetrahydrofuran,
3-ketotetrahydrothiophene, and 3-ketoxetane; a cyclic ester having
from three to eight carbon atoms, for example 2-methyl caprolacone,
caprolactone, valerolactone, butyrolactone, diketene, and
propiolactone; or a C.sub.3-C.sub.8 cyclic carbonate, for example
ethylene carbonate, propylene carbonate, 1,2-butanediol carbonate,
1,2-penanediol carbonate, 1,2-hexanediol carbonate, and
1,2-heptanediol carbonate. In one embodiment, the cyclic carbonyl
compound is cyclohexanone.
[0017] The C.sub.3-C.sub.8 cyclic carbonyl compound may be present
in an amount corresponding to from about 0.1 to about 3.5 weight
percent of the total weight of the organic solution. In another
embodiment, the C.sub.3-C.sub.8 cyclic carbonyl compound is present
in an amount corresponding to from about 0.5 to about 2.5 weight
percent of the total weight of the organic solution. In yet another
embodiment, the organic solution comprises the C.sub.3-C.sub.8
cyclic carbonyl compound in an amount corresponding to from about 1
to about 1.5 weight percent of the total weight of the organic
solution.
[0018] Suitable porous base membranes include those composed of
polysulfone, polyethersulfone, polyester, polyphenyleneoxide,
polyphenylenesulfide, polyvinyl chloride, polyacrylonitrile,
polyvinylidine fluoride, polytetrafluoroethylene, polycarbonate,
polyimide, polyetherimide, polyetherketone, and
polyetherether-ketone. A wide variety of suitable porous base
membranes are either available commercially or may be prepared
using techniques known to those of ordinary skill in the art. In
one embodiment, a porous base membrane which is a polysulfone film
is used. In another embodiment, the porous base membrane is a
porous polyethersulfone film.
[0019] Interfacial polymerization includes contacting an aqueous
solution of one or more polyamine monomers onto a porous support
membrane; followed by coating an organic solution, generally in an
aliphatic solvent, containing one or more polyacid halide monomers.
At the interface of the two solution layers, which lies near the
surface of the porous support, a thin film polymer is formed from
condensation of the electrophilic and nucleophilic monomers and is
adherent to the porous support. The rate of thin film formation may
be accelerated by heating or addition of catalysts. The polyacid
halide monomer on contact with the polyamine monomer reacts on the
surface of the porous base membrane to afford a polyamide disposed
on the surface of the porous support membrane. Suitable polyacid
chlorides include trimesoyl chloride, terephthaloyl chloride,
isophthaloyl chloride, succinic acid diacid chloride, glutaric acid
diacid chloride, adipic acid diacid chloride,
trans-cyclohexane-1,4-dicarboxylic acid diacid chloride,
cis-cyclohexane-1,4-diarboxylic acid diacid chloride, the triacid
chloride of Kemp's triacid, and mixtures comprising two or more of
these polyacid chlorides. Suitable polyamines include
para-phenylene diamine (ppd), meta-phenylene diamine (mpd),
4,4'-diaminobiphenyl, ethylene diamine, 1,3-propane diamine,
1,6-hexanediamine, 1,10-decanediamine, 4,4'-diaminodiphenyl
sulfone, 1,3,5-triaminobenzene, piperazine,
cis-1,3,5-cyclohexanetriamine, and mixtures comprising two or more
of these polyamines. Suitable organic solvents include hydrocarbon
solvents, alcohol solvents, ketone solvents, ester solvents, ether
solvents, amide solvents, and mixtures thereof. The interfacial
polymerization reaction may be carried out at a temperature ranging
from about 5.degree. C. to about 60.degree. C., preferably from
about 10.degree. C. to about 40.degree. C.
[0020] In order to improve permeability and/or salt rejection, the
polyamide membrane may be post-treated with an oxidizing solution,
such as a sodium hypochlorite solution. The concentration of sodium
hypochlorite in the solution may range from about 10 ppm to about
4000 ppm.
EXAMPLES
Examples 1-11
Post-Treatment with 4-Nitrobenzenesulfonyl Chloride
[0021] Polyamide RO membrane were cut into 6''.times.12'' size and
then clamped between two aluminum hand-frames and sealed with 6
clamps around the edges. The membrane was rinsed with water for
about 10 seconds, then treated with a reagent solution containing
4-nitrobenzenesulfonyl (nosyl) chloride in methanol solution as
listed in Table 1 for the specified time (between 30 and 90
seconds) at ambient temperature, and let stand for 3 minutes. The
reagent mixture was poured off the membrane from the same corner
that it was administered. The membrane was then dried in a
ventilated oven at 55.degree. C. for 10 minutes, cooled to ambient
temperature, and stored in a refrigerator until testing on a
cross-flow testing bench.
Comparative Experiments 1-3
[0022] Control RO membranes were prepared as described above,
except no post-treatment was performed.
Protocol for Testing Coated RO Membranes for NaCl Rejection and
Permeability
[0023] Test coupons were cut and treated with a 40000 ppm NaCl
solution (in Dl water) at 800 psi at 20.degree. C. for 1 hour.
After this time, the permeate was collected, weighed and its
conductivity measured to obtain the salt rejection and membrane
permeability. The membrane was then treated with a sodium
hypochlorite solution (70 ppm free chlorine in Dl water) at 225 psi
at 20.degree. C. for 30 minutes. After this time, the membrane was
rinsed with Dl water for 0.5-1.0 h and again treated with a 40000
ppm NaCl solution at 800 psi at 20.degree. C. for 1 hour. The
permeate was again collected, weighed and its conductivity measured
to obtain the salt rejection and membrane permeability. The
post-chlorination samples were also analyzed by ICP (Inductively
coupled plasma mass spectrometry) or azomethine/UV method for boron
rejection characterization, using the method described in the Hach
DR/2400 Spectrophotometer procedures manual.
[0024] Results are shown in Table 1. Without any nosyl chloride
post-treatment, the control RO membrane had a boron rejection of
86.6% to 88.6% and salt passage of to 99.4%. However, after the
nosyl treatment, boron rejection increased to 91-97% and salt
rejection increased to 99.6-99.9%.
TABLE-US-00001 TABLE 1 Membrane permeability, salt passage, and
boron rejection performance (boron results characterized by ICP
method) Post- treatment Composition Re- Solution action Perme- %
Salt Boron (wt %) time PVA ability Rej. rejection Ex. No. Nosyl TEA
(sec) wt % (A-value) % % 1 1 0.1 60 1 1.1 99.6 92.8 2 1 0.3 30 1
1.1 99.8 95.6 3 1 0.3 90 1 1.2 99.7 92.3 4 1 0.3 90 3 0.9 99.9 94.4
5 1 0.5 30 2 1.1 99.7 92.6 6 1 0.5 90 2 1.2 99.6 94.2 7 1 0.3 60 2
0.9 99.8 95.4 8 1 0.3 60 2 1.2 99.9 91.3 9 2 0.5 60 2 0.8 99.8 95.2
10 2 0.3 60 1 0.9 99.5 96.2 11 2 0.3 60 3 0.7 99.9 97.1 Comp -- --
-- 1 1.7 99.4 88.3 Ex. 1 Comp -- -- -- 2 1.8 99.3 88.6 Ex. 2 Comp
-- -- -- 3 1.8 99.4 86.6 Ex. 3
Examples 12-16
Post-Treatment with Other Agents
[0025] RO membranes were treated with 1,3-benzenedisulfonyl
chloride (BDSC), 4-cyano benzenesulfonyl chloride (cyano BSC), and
methanesulfonyl chloride. The membranes showed increased boron
rejection compared to the control membranes.
Examples 17-31
In-Situ Treatment with Benzenedisulfonyl Chloride
Examples 17-22
Procedure for Membrane Fabrication Using Handframe Coating
Apparatus
[0026] Composite membranes were also prepared using a handframe
coating apparatus consisting of a matched pair of frames in which
the porous base membrane could be fixed and subsequently coated
with a polyamide coating comprising a C3-C8 cyclic carbonyl
compound and a C1-C8 amide compound. The following procedure was
used. The porous base membrane was first soaked in deionized water
for at least 30 minutes. The wet porous base membrane was fixed
between two 8 inch by 11 inch plastic frames and kept covered with
water until further processed. Excess water was removed from the
porous base membrane and one surface of the porous base membrane
was treated with 80 grams of an aqueous solution comprising
meta-phenylenediamine (MPD) (2% by weight) and triethylammonium
camphorsulfonate (TEACSA) (6% by weight), the upper portion of the
frame confining the aqueous solution to the surface of the porous
base membrane. After a period of 120 seconds, the aqueous solution
was removed from the surface of the porous base membrane by tilting
the assembly comprising the frame and the treated porous base
membrane until only isolated drops of the aqueous solution could be
observed on the surface of the treated porous base membrane. The
treated surface was further treated by exposure to a gentle stream
of air to remove isolated drops of the aqueous solution. The
treated surface of the porous base membrane was then contacted with
150 grams of an organic solution comprising trimesoyl chloride
(0.20% by weight) mesitylene (1.5% by weight), cyclohexanone (6% by
weight) and benzenedisulfonyl chloride (weight % as shown in Table
2 below), in Isopar G solvent. Excess organic solution was then
removed by tilting a corner of the frame and collecting the excess
organic solution in a suitable collection vessel. The treated
assembly was then placed in a drying oven and maintained at a
temperature of 60.degree. C. for a period of about 10 minutes after
which the composite membrane was tested.
TABLE-US-00002 TABLE 2 Hand Frame Organic Coating Solutions Example
No. Organic Additve 17 6% cycl + 1.5% mesitylene + 0% BDSC 18 6%
cycl + 1.5% mesitylene + 0.05% BDSC 19 6% cycl + 1.5% mesitylene +
0.10% BDSC 20 6% cycl + 1.5% mesitylene + 0.20% BDSC 21 0% cycl +
1.5% mesitylene + 0% BDSC 22 6% cycl + 1.5% mesitylene + 0.2%
BDSC
Examples 23-31
Procedure for Membrane Fabrication Using Pilot Coater
[0027] The handframe procedure was duplicated using a pilot coating
machine capable of coating a 12-inch wide web. A porous base
membrane was fed through an aqueous coating bath composed of 2.9 wt
% MPD and 6.6 wt % TEACSA in water. The porous base membrane coated
on one side with the aqueous solution was passed through a rubber
nip roller to remove excess fluid. The coated porous base membrane
was then fed through an organic coating bath composed of a
water-immiscible solvent, a polyacid halide, and the organic
additives, as shown in Table 3. Following passage through the
organic coating solution, the porous base membrane was passed
through a dryer to remove solvent and water to provide the product
composite membrane.
TABLE-US-00003 TABLE 3 Pilot Coater Organic Coating Solutions
Example No. Organic Additve 23 0% cycl + 1.5% mesitylene + 0% BDSC
24 1% cycl + 1.5% mesitylene + 0% BDSC 25 1% cycl + 1.5% mesitylene
+ 0.18% BDSC 26 1% cycl + 1.5% mesitylene + 0.36% BDSC 27 1% cycl +
1.5% mesitylene + 0.71% BDSC 28 1% cycl + 1.5% mesitylene + 0% BDSC
29 1% cycl + 1.5% mesitylene + 0.18% BDSC 30 1% cycl + 1.5%
mesitylene + 0.36% BDSC 31 1% cycl + 1.5% mesitylene + 0.71%
BDSC
The membranes were tested using the protocol described for Examples
1-11. Results are displayed in Table 4.
TABLE-US-00004 TABLE 4 Testing Conditions and Results for Examples
18-32 Pre-Chlorination Post-Chlorination Rinse Chlorination Test
Permeability Permeability Ex. Pressure Pressure Pressure NaCl (A-
Passage (A- Passage No. (psig) (psig) (psig) (ppm) value) (%)
value) (%) 17 225 225 225 2000 6.8 0.99 6.1 0.35 18 225 225 225
2000 6.4 0.63 5.8 0.25 19 225 225 223 2000 5.3 0.43 5.3 0.21 20 225
225 225 2000 2.8 0.31 43 0.21 21 225 225 300 32000 2.2 0.82 4.0
0.57 22 225 225 800 32000 2.1 0.30 3.8 0.30 23 115 115 115 500 2.1
0.30 12.3 0.87 24 115 115 115 500 24.4 2.91 25.3 1.27 25 115 115
115 500 14.6 0.91 26.2 0.85 26 115 115 115 500 3.9 0.78 27.4 1.26
27 115 115 113 500 6.7 0.81 27.8 0.94 28 115 115 115 500 14.1 0.37
14.3 0.69 29 115 115 115 500 7.3 1.15 16.5 0.86 30 115 115 115 500
6.3 0.72 19.3 0.69 31 115 115 115 500 5.6 1.42 23 0.94
A dramatic and simultaneous increase in % rejection and A-value
after chlorination was seen in many cases when BDSC was
present.
[0028] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *