Studies on Separation Performance
of Interfacially Formed Membranes
Department of Chemical Engineering
Jennifer R. Du
IPR 20
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Outline
• Basic principles of membrane separation
• Interfacially formed membranes
• Separation performance in CO2 capture, natural gas dehydration,
desalination, and drinking water treatment
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Separation Spectrum
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Sieve Mechanism of Porous Membranes
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Solution-Diffusion Mechanism of
Nonporous Membranes
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3 Key Elements to Determine the
Performance (flux/selectivity)
1. Material Chemistry Film-formation and mechanical property
Inherent hydrophilicity, fouling tendency
Intrinsic permeability & selectivity
Bio-compatibility
Chemical resistance
2. Pore Size 0.3-0.5 nm for GS, PV
0.4-1.2 nm for desalination, separate low MW solutes
2-200 nm for UF, separate high MW solutes
50-1000 nm for MF
3. Selective Layer Thickness Controls the flux (productivity)
As thin as possible
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Interfacially Formed Thin-film-composite
(TFC) Membranes
contact withorganicvapor
Conventional method: monomer
Our work: polymer
Conventional method: liquid-liquid interfacial reaction
Our work: solid-liquid or solid-vapor interfacial reaction
7Conventional method: limited to RO or NF of liquid mixtures
Our work: good for GS, PV, NF, and UF processes
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Interfacially Formed Asymmetric Structure
top
bottom
Before
water
rinsing
After
water
rinsing
top
bottom
Bulk
crosslinking
Interfacial
crosslinking
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ideal for high flux IPR 20
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Interfacially Formed PDM membranes
Crosslinked PDM
NCH2O
CH3
O
CCH3 C
CH2
CH3
+ ClCH2 CH2ClCH2
CH3 C CH2 CH2
CH3
CH3
CH2CH2 O C
O
C CH3N+
CH2O
O
CH2C N+
CH3
CH3
Cl- Cl-
CH2 CH2
Poly(N,N-dimethylaminoethyl methacrylate) PDM
quaternization
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Chemical Properties of PDM Membranes
0 2 4 6 8 1050
60
70
80
Crosslinker Concentration (g/L)
Wa
ter
Co
nta
ct
An
gle
(o)
Low contact angle → High hydrophilicity
1. Weak alkalinity
2. High hydrophilicity
1% PDM aqueous solution: pH 7.7
3. Strong polarity
Dye sorption by
Acid orange
“ - ”
Neutral gray
“ 0 ”
Basic fuchsine
“ + ”
Du et al. J. Appl. Polym. Sci. 91 (2004) 2721-272810
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Flue Gas (CO2/N2) Separation
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Membrane α (CO2/N2) JCO2 (GPU)
Poly(4-vinylpyridine-co-acrylonitrile) 9 0.001
Poly(DMAEMA-co-acrylonitrile) 90 0.2
Plasma-grafted DMAEMA on polyethylene 130 5
Polyethylenimine/Polyvinyl alcohol 230 4
PDM/PSF (Bulk crosslinked) (our work) 50 30
PDM/PSF (Interfacially formed) (our work) 50 85
Comparison with Other Membranes
for CO2 Separation
low
pΔAt
VJ = Unit: GPU= 10-6cm3(STP)/cm2.s.cmHg
2N
2CO
J
Jα =
Du et al. J. Membr. Sci. 279 (2006) 76-85; 290 (2007) 19-28 12
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Natural Gas Dehydration
Wet Gas
Water Out
Membrane Dehydration
System
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Membrane Dehydration System
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Gas Dehydration Performance
JH2O (GPU) α (H2O/CH4)
PDM/PAN (our work) 4000 3500
Pilot test * (other polymer) 45 100
Du et al. Chem. Eng. Sci. accepted* Liu et al. Chem. Eng. Technol. 24 (2001) 1045-1048.
0.00 0.01 0.02 0.030.90
0.92
0.94
0.96
0.98
1.00
Molar fraction of H2O in feed
Mo
lar
fra
cti
on
of
H2O
in
pe
rme
ate
0
5
10
15
20
Wa
ter flu
x (
mo
l/m2.h)
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Glycol Regeneration System -
Pervaporation
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Glycol Regeneration Performance
• Selectivity of PV is much
higher than that of
distillation at low feed
water concentration
30oCDownstream pressure 1.3 kPa
0.0 0.2 0.4 0.6 0.8 1.00.80
0.85
0.90
0.95
1.00
Molar fraction of H2O in feed
Mo
lar
fra
cti
on
of
H2O
in
pe
rme
ate
0
100
200
300
400
500
Wa
ter flu
x (
mo
l/m2.h)
VLE (@40 kPa)
Du et al. Sep. Purif. Technol. 64 (2008) 63-7017
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Comparison with Other Membranes for
Glycol Regeneration
10 100 1000 100001
10
100
1000
25oC
F
lux
(m
ol/
m2h)
H
2O/EG
PVA/PSF (Texaco Inc, 1989)
SPE (Texaco Inc, 1993)
GFT1510 PVA/PAN (Jehle et al, 1995)
PVA/PES (Chen and Chen, 1996)
Chitosan/PSF (Feng and Huang, 1996)
PAA/PVA (Burshe et al, 1998)
Chitosan/PES (Nam and Lee, 1999)
SPEEK (Huang et al, 2002)
SPEEK/PMMA-PVDF (Shao et al, 2005)
PVA-GPTMS/TEOS (Guo et al, 2006)
NaA zeolite (Nik et al, 2006)
PDMAEMA/PSF (our work)
80oC
75oC
30oC
30oC
80oC
30oC
70oC
30oC
30oC
30oC
30oC
30oC
40oC
40oC
40oC
50oC
50oC
50oC
50oC
60oC
60oC
60oC
60oC
30oC
40oC
50oC
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Nanofiltration
• Commercially available
mostly negatively charged (aromatic polyamides, sulfonated polysulfone)
• Separation mechanism
Physical sieving – neutral organics (i.e., polysaccharide)Electrostatic repulsion/attraction – ions ( i.e., salts, dyes)
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0.8 MPa, 25oCIPR 20
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Salt
Rejection (%)
PDM NTR-7450 (Nitto Denko)*
MgCl2 98 13
MgSO4 91 32
NaCl 77.8 51
Na2SO4 66 92
Desalination Performance
*NTR-7450 (Hydranautics/Nitto Denko): sulfonated polysulfone20
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Solution ∆R (%) ∆F (%)
NaClO (5 ppm) -2 4
H2O2 (5 ppm) -8 -4
Chemical Resistance
MgSO4 1g/L; 3 weeks storage in solutions
Resistant to oxidants
N.B.- Commercial aromatic
polyamide NF membranes are
very sensitive to chlorine
At
VF = %100
C
CCR
F
PF ×=
Du et al. J. Membr. Sci. 239 (2004) 183-188 21
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Fouling Control in Water Treatment
Morphology Surface Chemistry
roughness hydrophilicity
porosity charge
tortuosity
thickness
pore size distribution
PVDF (polyvinylidene fluoride) membranes:
• Good film-forming property
• Good chemical, thermal resistance
• High hydrophobicity
• Rough surface
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CH2 CH
O
COCH3
xCH2 CH
yOH
poly(vinyl alcohol) (PVA)
y/(x+y) = 87 %
Material Selection for Modification - PVA
Good film-forming property
Good physical and chemical resistance
Non-toxic
Highly hydrophilic (active layer material for commercial PV)
Smooth surface (protective layer material for commercial
NF, RO)
Affinity to PVDFHydrophilicity
*Affinity to PVDF
23*Gholap and Badiger, J. Phys. Chem. B 109 (2005)13941-13947
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Interfacially Formed PVA Membrane
OH OH OH OH
PVDF layerPVA layer
Glutaraldehyde Vapor OHC-(CH2)3-CHO
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CH2 CH
O
CH2 CH
CH O
CH2 CH2 CH2 CHO
CH2 CH
O
COCH3
CH2 CH
CH2 CH
O
CH2 CH
CH
O
CH2 CH2 CH2
O
CH2 CHCH2
CH
CH2 CH
O
CH CH2 CH
OH
OH
O
COCH3
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Surface Comparison of PVDF and
PVA/PVDF Membranes
PVDF membrane
(Donated by Koch)
PVA/PVDF membrane
0200400600800
Binding Energy (eV)
PVA/PVDF membrane
PVDF membrane
O1SN1S
C1S
S2p
F1S F, N, S: PVDF >PVA/PVDF
O: PVA/PVDF > PVDF
Contact angle reduced ~ 10o, 16%
Roughness reduced
Du et al. Water Res. 43 (2009) 4559-4568 25
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Ultrafiltration Setup
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Fouling Resistance
PVA/PVDF membrane:
• ease of cleaning
• flux stability
• 95% higher flux than PVDF membrane 27
0
10
20
30
40
50
1 2 3 4 5 6 7 8
Flu
x r
eco
very
(%
)
Cleaning Cycle0
100
200
300
400
0 4 8 12 16 20
Wate
r fl
ux (
L/m
2·h
)
Operating time (h)
PVA/PVDF membrane
PVDF membraneIPR 20
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Effluent Quality
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0.08
118.1
0.46
0.13
6 5.8
0.01
0.1
1
10
100W
ate
r Q
uali
ty
Influent
Effluent PVDF
Effluent PVA/PVDF
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Summary
Porous/nonporous selective layers via solid-liquid or solid-vapor
interfacial reaction
Good permselectivity for gas separation, pervaporation,
nanofiltration and ultrafiltration processes
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Acknowledgements
• Dr. Amit Chakma, Dr. Xianshe Feng, Dr. Peter M. Huck, Dr.
Sigrid Peldszus, Dr. Jiasen Zhao
• Membrane Separation Processes Research Lab @UW
• NSERC Chair in Water Treatment @UW
• Industrial Research Partners
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