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Membranes Technologies
For Water and Energy Applications
Dr. Chuyang Y. (CY) TangSchool of Civil & Environmental Engineering
& Singapore Membrane Technology Centre
Nanyang Technological University, Singapore
[email protected] 8, 2011 1
Outline• Background
• Ongoing membrane research works
• Fouling
• Trace organics
• Membrane fabrication/characterization
• Osmotic membrane processes
• Summary
2
3
What is a membrane?
Feed Retentate rich in B
Permeate rich in A
Membrane ∆P, ∆C, ∆T, ∆E
A selective barrier that allows the separation of components in a mixture.
Energy input or driving force is required to separate components that otherwise mix spontaneously
Driving forces:
∆P – pressure difference
∆C – concentration difference
∆T – Temperature difference
∆E – electrical potential difference
A B
AB
BA
4
Membranes in the water cycle
secondary wastewater
effluent
MF, UF, NFRaw Freshwater Conventional
treatment
Uses:DomesticIndustrial
AgriculturalEcological
Raw seawater
RO, electrodialysis
Distillation
Membrane Biological Reactor
Conventional wastewater plant
Sources
Legend:
Conventional treatment
Membrane treatmentUse Discharge
Nature
Conventional treatment
MF/UFRO
Water treatment
Wastewater treatment
Water reclamation
Singapore - a show case for membranes and the water cycle
WTP 274ML/d
Desal 136
NeWater 500 *
MBR 23
* Includes Changi. Target is 30 % reuse by 2011, 45ML/d to indirect potable
Barrage
700 km2
4.7 m pop.
5
Courtesy: Prof. Tony Fane
EN4556 Membrane Water Reclamation6
7
Where are membranes used?
Removal of CO2 from natural gas
Desalination & water treatment
Dialysis
Fabrics
Drug delivery devices
Fuel Cells
Membrane Bioreactors (MBR)
CY’s background• PhD, Stanford University (2002-2006),
James O. Leckie’s “water chemistry” group• Assistant Professor, (2006-current),
Nanyang Technological University– School of Civil & Environmental Engineering– Singapore Membrane Technology Centre
• IDA Fellow• FiDiPro Fellow
8
SMTC
SMTC
A centre specialized in membrane technology for water and energy applications
http://smtc.ntu.edu.sg 9
CY’s ongoing research
• Membrane fouling and fouling control• Trace organics removal• Membrane synthesis• Membrane characterization• Osmotic membrane processes
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Membrane Fouling
Permeate Flux
membrane
ConcentrateFeed Water Cross flow velocity
Pressurized vessel
)( fm RRPJ+
∆=
η
J – permeate fluxΔP – differential pressureη – permeate water viscosityRm – hydraulic resistance of membrane Rf – hydraulic resistance of foulant
Insoluble salts
Inorganiccolloids
Organicmacromolecules
Microorganisms
12
Membrane fouling
Membrane PropertiesHydrodynamic Conditions
Feedwater Composition
FluxCross flow velocity
Foulant concentrationpH, ionic strength, Ca2+
RoughnessChargeHydrophobicity Tang et al., Advances in Colloid and
Interface Science, accepted 2010.
13
RO/NF membrane fouling
Tang & Leckie, Env. Sci. & Tech., 41, p4767, 2007.
14
Effect of initial flux
AB
C
A: 689.5 kPa 1.2 m/day
Membrane MembraneMembrane
ESPA3 membrane at increasing initial flux
A B C
Scale bar for all TEM images
500 nm
B: 1379 kPa 2.0 m/day
C: 2758 kPa 3.8 m/day
5 mg/L PAHA, pH 7, 10 mM NaCl4 days
Limiting flux for protein
150 24 48 72 96
0
30
60
90
120
150
180 P180 P140 P110 P75 P50 P25
Flux
(L/m
2 .hr)
Time (hrs)
20 mg/L BSApH 7, IS=10mM, CF=9.5cm/s
Wang and Tang, JMS, 2011
Limiting flux for protein
16
20 mg/L BSApH 7, IS=10mM, CF=9.5cm/s
0 24 48 72 960
15
30
45
60
75
0.0
20.0
40.0
60.0
80.0
100.0
Nor
mal
ized
flux
(%)
NF270 XLE GM NF90
Flux
(L/m
2 .hr)
Time (hrs)Wang and Tang, JMS 2011
Limiting flux for protein
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0 50 100 150 200 250 300 350 4000
10
20
30
40
50
60
70
J @ 96 hr
Flux
@ 9
6 hr
(L/m
2 .hr)
Protein zeta potential squared (mV2)
Wang and Tang, JMS, 2011
18
Fouling Control1) Use of chemicals to improve RO desalination2) Membrane modification3) Pretreatment4) Optimization of operational parameter to minimize fouling
Spacer Design & Hydrodynamic in Spiral WoundModule
• Spacer & hydrodynamics• Ultrasound• Vibration• Aeration
Ongoing works on RO fouling control
19
Organic toxins• Pharmaceuticals• Endocrine disruptors• Pesticides/herbcides• Disinfection byproducts• Other emergent contaminants• …
Inorganics• Boron• Bromide• …
N-nitrosodimethylamine (NDMA )
Micropollutants
A4
Boric acid
• PFOS S
O
O
F OH
F
F
F
F
F
F
F
F
F
F
F
F F
F
F
F
0 200 400 600 800 1000Binding Energy (eV)
Virgin
15 min1 hr6hr
24 hr
96 hrC N
OF
F O
Test conditions: 10 ppm PFOS, 200 psi, 20 cm/s CF, 25C
XPS resultsBW30 at different contact time
Micropollutants
4 6 8 10 12 140.0
0.2
0.4
0.6
0.8
1.0Borate ionH2BO3
-Boric acid H3BO3
Frac
tion
of B
oron
pH
SWRO: 88-95%BWRO: 38-65%
−+ += 3233 BOHHBOH
A4
Experimental and Predicted Boron Rejection
0 4 8 12 160.0
0.2
0.4
0.6
0.8
1.0Bo
ron
Reje
ctio
n
Jw (µm/s)
Experimental PredictedRO AL-FW AL-DS
200 psi
260 psi
Micropollutants
PAEs = Phthalate Acid Esters
C
C
O
O
O
O
3CH
3CH
C
C
O
O
O
O
2 5CH
2 5CH
ChemPaster
C
C
O
O
O
O
4 9CH
4 9CH
C
C
O
O
O
O
CH
CH
2 5CH
2 5CH
5 11CH
5 11CH
ChemPaster
DMP DEP DnBP DEHP
PAEs M.W.(Da)
Log Kow
Dipole Moment(D)
Volume(A3)
Dimethyl phthalate (DMP) 194.2 1.66 2.80 173.1Diethyl phthalate (DEP) 222.2 2.65 2.90 206.7Di-n-butyl phthalate (DnBP) 278.4 5.6 2.75 273.9Di(2-ethylhexyl)phthalate (DEHP) 390.6 7.3 2.84 441.5
Pharmaceuticals
Carbamazepine (CB) Naproxen (NA)
Ibuprofen (IP) Diclofenac (DI)
24
The National Geography Magazinehttp://ngm.nationalgeographic.com/big-idea/09/desalination-pg2
Next generation membranes
25
Membrane Fabrication
Hollow Fiber Spinning Process
Spinneret
Water spray
Coagulation bath
Syringe pump
Dope fluid
Bore fluid
Flushing bath
very porous structure
relatively dense structure
Nonsolvent in-flow2
1
n
n
DKD
= =solvent out-flow
Membranes with Different Structures
NonsolventSolvent
open-cellstructure
dopeformulation
k <1
k<1
Polymer
A
B
C
D
K>1
Membrane fabrication
A thin film composite polyamide membrane for forward osmosis applications
Membranes fabricated using layer-by-layer method
Membrane Characterization
28
Contact angle
AFM adhesion force
Infrared XPS
Microscopic characterization
Electrokinetic characterization
O (%) N (%) C (%) Cl (%)
NF90Avg 15.61 10.08 63.71 10.59
STD 0.83 0.58 0.78 0.33
LEAvg 16.01 10.03 62.99 10.98
STD 1.19 0.64 1.35 0.26
XLEAvg 15.46 10.23 63.51 10.80
STD 0.46 0.49 1.11 0.39
BW30Avg 30.55 2.25 64.63 2.57
STD 0.79 1.05 1.07 0.75
LFC1Avg 29.95 2.7 64.87 2.57
STD 0.77 0.57 0.9 0.46
Table. Elements by atomic percent of degraded membranes at 2000ppmhr Cl and pH4
Membrane chlorination
Alternative disinfectants? Alternative membranes?
30
2) Ultrasonic time domain reflectometry(collaboration with MAST, Colorado)Based on acoustic properties of medium, provides thickness & density information, in-situmethod
Ultrasonic Transducer
Mass Flow Controller
1) Feed fouling monitor- Adaptation of Integrity Sensor (NTU patent)- Dual membrane based sensors to predict feed fouling propensity, online
monitoring and more sensitive than SDI and MFI
3) Electrical impedance spectroscopy (collaboration with INPHAZE Australia)
Based on electrical properties (conductance & impedance) of medium, provides structural information, in-situ method
Other membrane characterization works
20 min 40 min 70 min
Feed
Draw
Direct microscopic observation
31
Reverse osmosis vs. forward osmosis
Reverse osmosis(RO)
Pressure retarded osmosis(PRO)
Forward osmosis(FO)
Water flux
Applied pressure∆π, Osmotic pressure
High concentration solution
Membrane
Low concentration solution
FO, P = 0High concentration solution
Membrane
Low concentration solution
PRO, P < ∆πHigh concentration solution
Membrane
Low concentration solution
RO, P > ∆π
32Xu et al, JMS 348, 298-309, (2010)
FO desalination
McCutcheon, J. R.; McGinnis, R. L.; Elimelech, M., A novel ammonia-carbon dioxide forward (direct) osmosis desalination process. Desalination 2005, 174, (1), 1-11.
33
Forward Osmotic Membrane Bioreactor
Sludge
Diluted draw solution
Wastewater
Draw solution
Purified water
FO membraneH2O H2O
Advantages of FOMBR
- lower energy requirement
- better water quality for water reclamation 34
• To provide carbon-neutral biofuels and other useful product (e.g., fertilizer)
• To treat wastewater • To sequester carbon dioxide
35
FO Applications – NASA Omega
Suitable draw solutions high osmosis pressure good FO performance easy regeneration non-toxic seawater, RO brine??
Optimized membrane high water flux low solute passage strength stability
Major Challenges for FO Applications
The National Geography Magazine36
Pressure Retarded Osmosis
37
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PRO water flux and power density at various conditions
Draw (M) Feed (mM) ∆P (Pa) Jw (L/m2h) Power density (w/m2)0.5 10 0 7.70 00.5 10 3.52E+05 7.20 0.700.5 10 6.45E+05 5.61 1.000.5 10 1.15E+06 1.79 0.571 10 0 14.62 01 10 6.36E+05 12.22 2.161 10 1.19E+06 9.48 3.13
Bench scale PRO tests and optimization
Summary
• Membrane fouling and fouling control• Trace organics removal• Membrane synthesis• Membrane characterization• Osmotic membrane processes
• FiDiPro Programme – Tekes – VTT
• Funding support from the Singapore Environment and Water Industry Programme Office (EWI), National Research Foundation
• Support from Singapore Membrane Technology Centre
• Students/Post-docs/Collaborators
Acknowledgements
EN4556 Membrane Water Reclamation42
Monovalentions
Multivalentions
SuspendedsolidsWater Viruses Bacteria
Microfiltration
Monovalentions
Multivalentions
SuspendedsolidsWater Viruses Bacteria
Ultrafiltration
Selective skin layer
Porous substrate
Porous Membranes
Asymmetric structure
EN4556 Membrane Water Reclamation43
Nanofiltration
Reverse Osmosis
Non-porous skin
Porous substrate
Non-porous Membranes
Monovalentions
MultivalentionsWater
Organics NOM Colloids Viruses Bacteria
Monovalentions
MultivalentionsWater
Organics NOM Colloids Viruses Bacteria
