Transcript Slide 1

Di-sulfonated Poly(Arylene Ether Sulfone)
Copolymers as Novel Candidates for
Chlorine-Resistant Reverse Osmosis
Membranes
M. Paul, H. B. Park*, B. D. Freeman*, Z. Zhang, G.
Fan, A. Roy, J. S. Riffle and J. E. McGrath.
Macromolecular Science and Engineering Program,
Macromolecules and Interfaces Institute (MII),
Virginia Polytechnic Institute and State University,
Blacksburg, VA 24061
*Center for Energy and Environmental Resources
The University of Texas at Austin
$$$- ONR
Project Goal
Objective
Develop new reverse osmosis membrane materials showing
excellent chlorine-tolerance, high water flux, good salt rejection, antifouling and arsenic removalproperties relative to the state
of the art.
Approach
• Synthesize systematic series of directly copolymerized sulfonated
copolymers and vary their structures
• Study fundamental properties (water permeability, salt permeability
and water/salt selectivity) of sulfonated polymers
• Preparing the most promising new materials as thin membranes.
1
Problem: a Shortage of Clean Water
• 41% of the Earth’s population (2.3 billion) live
in water-stressed areas; 3.5 billion by 2025.
• The number of people living without clean,
piped water is 1.2 billion (WHO).
• Water shortages limit economic development
and threaten human life.
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Source:
www.abc.net.au/news/newsitems/200609/s1733920.htm
2010
$1,200
$1,000
$800
$600
2005
$400
$200
Prediction
Water Desalinization Report, 42(35), 1, 2006,
www.bp.com, Ultrapure Water, 23(3), 14, 2006
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• >98% of U.S. water
treatment facilities use
chlorine - the most
economical disinfectant to
deactivate pathogenic
microorganisms in drinking
water
$1,400
ni
te
d
• Membranes (reverse
osmosis and nanofiltration) provide the most
economical desalinization.
VALUE OF REVERSE OSMOSIS (RO)
SYSTEM COMPONENTS
U
• There are currently more
than 15,000 desalinization
plants worldwide (1/4 in
US)
AnnualSal
sales
es ($($
m ilmillions)
lions)
New Desalination Capacity (million m3/d)
Desalination Market
Issues Facing Commercially Available
Membranes for Water Desalination
• Polyamides
low chlorine tolerance prevents use in potable water applications and
especially food and beverage, medical, biochemical, and pharmaceutical
applications where chlorination and other similar oxidative cleaners or
sterilants are commonly employed.
Feed water
Costly Pretreatment Steps
Chlorinate
(0.2-5 ppm)
Dechlorinate
(Free chlorine
< 0.01 ppm)
Polyamide
desalination
membrane
To protect
membrane
from chlorine
T. Knoell, Ultrapure Water, 2006, 23, 24-31
Rechlorinate
(1-2 ppm)
Product water
Search for Chlorine Resistant RO MembranesPrevious Sulfonated Polymer Studies
H3C
SO3H
SO3H
CH3
O
C
n
O
O
CH3
S
O
n
H3C
Sulfonated poly(2,6-dimethyl
phenylene oxide) (SPPO)
Sulfonated polysulfone (SPS)
•Fouling and chlorine tolerance of sulfonated polysulfone
was superior to that of aromatic polyamides.
Howerver, manufacturing reproducibility issues and inability to prepare
a product with flux/rejection capabilities equivalent to aromatic
polyamides led to limited commercial success.
Parise et al., Ultrapure Water, pp. 54-65 (Oct. 1987); Allegrezza et al.,
Desalination, 64, 285-304 (1987).
VT Breakthrough- Chlorine Tolerant sulfonated
Poly (arylene ether sulfone) RO
Membranes
0h
100
8h
NaCl rejection (%)
90
16 h
24 h
33 h
•
reproducible to manufacture & stable
against chemical attack.
•
Access to structural variations (e.g., new
comonomers, block copolymers, controlled
crosslink structures, etc.) to achieve high
rejection and high flux.
BPS 40N
80
BPS 40H
70
SW30HR
(FilmTec)
60
 Proposed New Process with VT Membrane
Cross-flow
pH = 9.5
Feed = 2000 ppm NaCl
Pressure = 400 psig
Flow rate = 0.8 GPM
Chlorine = 500 ppm
50
40
0
4000
8000
Feed
water
12000
SO -M+
VT
membrane
(BPS) outperforms
O
O
S
O
O
S
O
commercial
polyamide
membrane
x
O
O
(SW30HR) under chlorine exposure
BPS 40 (X = 0.4; M = H+ or Na+)
3
Chlorinate
New
membrane
Product
water
16000
Chlorine exposure (ppm-hours)
+M -O3S
 Sulfonated Poly (arylene ether sulfone) (BPS)
Cost savings via elimination of dechlorination
required by current membranes
O
1-x
 Extended
membrane lifetime

Disulfonated Poly(arylene ether sulfone)
(BPS)
SO3-M+
O
+
O
O
O
S
M-O3S
O
CO
O
S
x
Hydrophilic
O
O
Cl
S
Cl
O
Hydrophobic
NaOH
NaCl
SO 3
110 o C
6h
O
pH~7
Acronym: BPS-xx
Bi Phenyl Sulfone: salt (M =Na+)
n
1-x
form (BPS), acid (M = H+) form
SO 3 Na
NaO 3(BPSH)
S
O
xx= molar fraction of disulfonic
NaCl
Cl
S
Cl
acid units, e.g., 30, 40, etc.
O
Copolymer Synthesis by Nucleophilic Aromatic Substitution
SO 3 Na
NaO 3 S
O
O
Cl +
S
Cl
Cl +
S
Cl
O
HO
Ar OH
Ar =
O
K 2 CO 3
NMP / Toluene
140 o C / 4 h
190 o C / 24 h
C
H2 SO 4
C
SO 3 H
HO 3 S
O
S
O
C
O
O
O
Ar
O
n
S
O
O
Ar
1-n x
C
Effect of Sulfonation Degree (Ion Exchange Capacity) on
Water and Salt Transport in Random BPS Copolymers
HO3S
SO3H
O
O
S
O
O
O
5
O
B P S 20H
4
3
B P S 35H
2
B P S 30H
1
B P S 20H
1
1.2
1.4
IEC value (meq/g)
1.6
1.8
1-x
O
B P S 40H
0
0.8
O
100
NaCl rejection (%)
2
Water permreability (L.m/m .h.bar)
S
x
95
2000 ppm NaC l
400 ps i
25 o C
C ros s flow
90
B P S 35H
B P S 30H
85
80
0.8
1
1.2
B P S 40H
1.4
IEC value (meq/g)
1.6
1.8
Various Types of Salt Rejection
by BPS in Comparison to Commercial Membrane
100
Commercial SPS composite membranes
(Hydranautics)
BPS 35H
100
95
80
90
60
70
60
70
40
40
50
40
30
Rejection (%)
Salt rejection (%)
80
20
35
10
20
0
20
15
0
Na2SO4 KCl
Na2SO4
NaCl MgSO4 MgCl2 CaCl2
IS (M) =
0.03
(IS: Ionic strength)
0.01
• Dead-end
• Feed pressure: 400 psig
• Feed temperature: 25 oC
0.01
12
10
NaCl
4
MgSO4 MgCl
2
Sulfonation degree
0.04
2
1
Sulfonation degree
CaCl2
0.01
0.03
(www.membranes.com)
Chemically tolerant NF membranes for
aggressive industrial application
Salt rejection: Na2SO4 > KCl ≥ NaCl > MgSO4 > MgCl2 > CaCl2
BPS Type Materials with NaCl Rejection > 97%
Name
Comment
mol%
sulfonation or
IEC
Water
permeability
(L.μm/m2.h.bar)
NaCl rejection
(%)
PAEB35
Random copolymer
(salt form)
35 mol%
0.24
97.8
PA40
Random copolymer
(salt form)
40 mol%
0.43
97.5
6F25PAEB35
Random copolymer
(salt form)
35 mol%
0.64
98.0
BPS20
Random copolymer
(acid form)
20 mol%
0.11
98.7
Epoxy-crosslinked
BPS50
Crosslinked
(salt form)
50 mol%
1.41
97.2
BPS35:Radel
Blend (90:10)
Blend
(salt form)
35 mol%
0.71
97.2
BPS35:6F35
Blend (95:5)
Blend
(salt form)
35 mol%
0.86
98.0
BPSH-15-BPS-15
Block copolymer
(salt form)
IEC = 1.36 meq/g
0.05
99.2
Lab-Scale Fabrication of Thin-Film
Composite Membrane from BPS-40
0.5 % (wt./vol.)
Polymer solution
in formic acid (1 day)
Drying wet support
(PSf)
at 105 oC (5 min)
Brush coating
(2~3 times)
Air drying at 50 oC
for 5 min.
Chlorine-Tolerance of
Thin-Film Composite (TFC) Membranes
10 h
20 h
25 h
NaCl rejection (%)
90
BPS 40H TFC
80
70
SW30HR
(FilmTec)
60
50
40
30
0
5000
10000
BPS 40H TFC
30 h
3
Permeate flux (L/m2.h.bar)
100
0h
15000
20000
Chlorine exposure (ppm-hours)
2.5
2
1.5
1
0.5
1 GFD/psi = 24.6 LMH/bar
0
0
5
10
15
20
25
30
Chlorine exposure time (hr)
Cross-flow, pH = 9.5, Feed = 2000 ppm NaCl, Pressure = 400 psig,
Flow rate = 1.2 GPM, Chlorine = 500 ppm
35
Arsenic Rejection
of Sulfonated Copolymer Membranes
+M -O3S
SO3-M+
O
S
O
O
O
O
S
x
O
O
O
1-x
Sulfonated poly(arylene ether sulfone) (M = H+ or Na+)
100
100
pH = 4.5
pH = 8
As (III) rejection (%)
As (V) rejection (%)
pH = 4.5
pH = 8
95
90
85
80
95
90
85
80
BPS1 30H
BPS2 40H
BPS3 40N
BPS130H
A: BPS 30H, B: BPS 40H, C: BPS 40N
BPS
2 40H
BPS340N
Summary: Trade-off Relationship Between
Permeate Flux and NaCl Passage
0.01
NaCl Passage (%)
0.1
PA (for sea water)
PA (for brackish water)
1
Millipore SPS
10
SPS (this work)
SPS composite (BPS40)
PA (for NF)
100
0.01
0.1
1
10
2
Permeance (L/(m .h.bar))
100
Conclusions & Future Works
Sulfonated poly(arylene ether sulfone) copolymer membranes
• Stable and reproducible properties
• High water permeability
• Moderate salt rejection (between that of NF and RO)
with excellent chlorine tolerance
• Excellent arsenic removal properties
•
Further fundamental studies to define structure/property relations.
•
Prepare and characterize chlorine-resistant composite membrane
with higher salt rejection.