forward osmosis: progress and challenges
TRANSCRIPT
Forward Osmosis: Progress and Challenges
Department of Chemical and Environmental Engineering Yale University
New Haven, Connecticut
Menachem Elimelech
2014 Clarke Prize Conference, November 7, 2014, Huntington Beach, California
Water Flux Eqn:
Feed
Permeate
mw PAJ
Hydraulic Pressure
water
MEMBRANE
water
Wa
ter
flu
x, J
w
P
0
RO (P > )
Reverse Osmosis (RO)
MEMBRANE
water
water
Draw Solution
Feed
Permeate
Water Flux Eqn:
mw AJ
Wa
ter
flu
x, J
w
P
0
FO (P = 0)
Forward Osmosis (FO)
Wa
ter
flu
x, J
w
P
0
Flux reversal point (P = )
PRO (P < )
MEMBRANE
water
water
Pressurized Draw
Solution Feed
Permeate
Water Flux: PAJ mw
Pressure Retarded Osmosis (PRO)
Wa
ter
flux,
Jw
P
0
Flux reversal point (P = )
PRO (P < )
Engineered Osmosis
RO (P > )
FO (P = 0)
Overview of Presentation
Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
Membrane
Draw Solution Recovery Process
Product water
Feed Water
Concentrate
Diluted Draw Solution
Concentrated Draw Solution
Energy Input
The Forward Osmosis Process
Energy Input in FO: “No Free Lunch.”
Can’t beat thermodynamics Separation energy of draw solution is proportional to the osmotic pressure of draw solution Input energy > energy equivalent to draw solution osmotic pressure Potential innovations through use of low-cost forms of energy (e.g., low-grade heat), rather than prime (electric) energy
SE = ΔP ≥ πΒ (R) Permeate
Brine
SE: Specific energy ΔP: Applied pressure πΒ(R): Brine osmotic pressure at recovery R
RO Energy Consumption
Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
SEmin= πΒ
SEmin= πD
πD is always > πΒ
Permeate Brine Draw
Comparing Energy of RO and FO-RO
SEmin (FO-RO) = πD > πΒ = SEmin (RO)
Condition for net driving force in FO
FO-RO Always Requires More Energy than RO Alone
Overview of Presentation
Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
Organic Fouling Reversibility in Forward Osmosis
0 500 1000 1500 20000
2
4
6
8
10
0
7
14
22
29
36Flux of clean membrane
Flux after
cleaning
Flu
x (
l/m
2/h
)
Flu
x (m
/s)
Time (min)
Fouling Cle
an
ing
FO membrane: CA (Hydration Tech)
Organic foulant (200 mg/L alginate); 50 mM NaCl; 0.5 mM Ca2+
Cleaning: 50 mM NaCl, increased crossflow, 15 min
Mi and Elimelech, Journal of Membrane Science, 348 (2010) 337–345.
FO Exhibits Fouling Reversibility with a Wide Range of Foulants
Alginate BSA Gypsum Silica0.0
0.2
0.4
0.6
0.8
1.0
Flux recovery by rinsing
Flux after fouling
No
rma
lize
d F
lux
Foulant TypeShaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
In Situ Surface Modification for Fouling Resistance
C O Cl
C O Cl
C O Cl NH2-PEG
Interfacial Polymerization
Polysulfone Support Layer Nascent Polyamide Layer
PEGylation
In Situ Modified Membrane
C O NH
PEG
C O NH
PEG
MPD+TMC
Control In Situ Modified0
20
40
60
80
100
120
Control In Situ Modified
Con
tact
Ang
le (°
)
Lu et al. Environ. Sci. Technol. 2013, 47, 12219−12228.
Modified Membrane Exhibits Organic Fouling Resistance
Control In Situ Modifed
80
85
90
95
100
Nor
mal
ized
Wat
er F
lux,
Jw/J
w,0(%
)
Fouling Cleaning
0 100 200 300 400 500
80
85
90
95
100
Polyamide In Situ Modified
Nor
mal
ized
wat
er fl
ux, J
w/J
w,0(%
)
Cumulative Permeate Volume (ml)
Control
Lu et al. Environ. Sci. Technol. 2013, 47, 12219−12228
Overview of Presentation
Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
D
tK
s
Tortuosity,
Porosity,
Thickness, ts
thin film (active layer) support
layer
K Solute resistance to diffusion ts Support layer thickness Tortuosity
Porosity D Draw solute diffusivity
Membrane structural parameter,
S
Current Focus: Reducing Structural Parameter of Membranes
S = 9583 μm
TFC-RO
S = 390 μm
TFC-FO
Significant Progress in the Past 10 Years
Yip et al. Environ. Sci. Technol. 2010, 44, 3812–3818
Low Structural Parameter is Critical for Obtaining High Water Flux
Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Challenge: Minimize Reverse Draw Solute Flux
Membrane
Draw Solution Recovery Process
Product water
Feed Water
Concentrate
Diluted Draw Solution
Concentrated Draw Solution
Js
The Driving Force for Reverse Draw Solute Permeation
A highly concentrated draw solution generates the osmotic gradient that drives the flux of water
The high concentration of draw solute also drives the reverse permeation of draw solute.
w mJ A
n
s mJ f c
Js
Jw
Feed Draw
Analytical Expression for Reverse Solute Flux
, ,exp exp
1 exp exp
w wD b F b
s
w w
w
J S Jc c
D kJ A
J J SB
J k D
, ,exp exp
1 exp exp
w wD b F b
w
w w
w
J S J
D kJ A
J J SB
J k D
Model Predicts Reverse Solute Flux for Salt and Neutral Solutes
0.01 0.1 1 10 100
0.01
0.1
1
10
100
Urea
Ethylene Glycol
Glucose
NaCl
Experimental Solute Flux (mol m-2 h
-1)
Pre
dic
ted
So
lute
Flu
x (
mo
l m
-2 h
-1)
180.2 g/mol
60.1 g/mol
62.1 g/mol
0.72 nm
Yong et al., Journal of Membrane Science 392–393 (2012) 9–17
Defined as ratio of forward water flux to reverse salt flux
Representative of the volume of water produced per moles (or mass) of solute lost
Depends solely on the membrane active layer permeability and selectivity
Reverse Flux Selectivity (RFS): An Important Design Parameter
TnRB
A
J
Jg
s
w
Membranes Are Constrained by the Permeability-Selectivity Tradeoff
Yip et al. Environ. Sci. Technol. 2011, 45, 10273–10282
Geise et al., Journal of Membrane
Science 2011, 369 (1-2), 130-138.
TnRB
A
J
Jg
s
w
Goal: Maximize B
A
Overview of Presentation Energy Aspects of Forward Osmosis Fouling Propensity and Reversibility in Forward Osmosis Desired Membrane Properties and Reverse Solute Flux Applications of Forward Osmosis
The Goal of FO is NOT to Replace RO!
RO is the Gold Standard for Desalination
FO can be used in Applications where RO cannot
Potential Applications of FO
High salinity feed waters that cannot be treated by RO (RO limited to feed water up to about 40,000 ppm)
Very difficult to treat feed waters (i.e., feed waters with very high fouling potential)
Zero liquid discharge (ZLD)
Pre-treatment to improve the performance of conventional desalination processes
Applications in Oil and Gas
Gregory et al., Elements, Vol. 7, 2011, 181–186
Applications in Oil and Gas: Very Hard to Treat Shale Gas Waters
Gregory et al., Elements, Vol. 7, 2011, 181–186 Upper Limit Conc. (mg/L)
TDS: 260,000
Hardness: 55,000
Alkalinity: 1,100
Calcium: 31,000
Cannot be treated by pressure-driven membrane processes (RO/NF)
The “Green Machine”: Treatment of Water from Hydraulic Fracturing
Source: Hydration Technologies Innovation (HTI)
Low-Grade Heat
Nature, 452, (2008) 260
McCutcheon et al., Desalination, 174 (2005) 1-11.
FO Desalination with Thermolytic Draw Solutions
Desalination 312 (2013) 67–74
Brine Concentrator for Treatment of High Salinity Shale Gas Wastewater
Oasys Water Inc.
TDS = 75,000 mg/L
TDS = 300 mg/L
FO in ZLD Schemes as Brine Concentrator
Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Pre-treatment for Conventional Desalination Technologies
Shaffer et al. (2014), in press, 10.1016/j.desal.2014.10.031.
Concluding Remarks The Promise • Low fouling propensity • Can treat high salinity brines • Can treat challenging wastewaters • Can be integrated with established technologies (e.g. RO)
and zero liquid discharge (ZLD) schemes
The Challenges • Development of low-cost high performance membranes • Minimizing reverse draw solute flux • More pilot demonstrations • Development of full-scale systems
Acknowledgments Current and former research group at Yale Collaborations: Korea University (Prof. S. Hong), Wollongong University (Prof. Long Nghiem Funding: National Science Foundation, Office of Naval Research, Department of Energy, US EPA, Cornell-KAUST