Studies on Separation Performance

of Interfacially Formed Membranes

Department of Chemical Engineering

Jennifer R. Du

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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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