Forward Osmosis: Progress and Challenges

Transcription

1 Forward Osmosis: Progress and Challenges Menachem Elimelech Department of Chemical and Environmental Engineering Yale University New Haven, Connecticut 2014 Clarke Prize Conference, November 7, 2014, Huntington Beach, California

2 Reverse Osmosis (RO) Water flux, J w 0 J Water Flux Eqn: w A P m Permeate RO (P > ) water water M E M B R A N E Feed Hydraulic Pressure P

3 Forward Osmosis (FO) Water flux, J w 0 Water Flux Eqn: J w A m FO (P = 0) Feed M E M B R A N E Permeate water Draw Solution water P

4 Pressure Retarded Osmosis (PRO) Water flux, J w J w 0 Water Flux: A m Flux reversal point (P = ) P PRO (P < ) Feed M E M B R A N E Permeate Pressurized Draw Solution water water P

5 Engineered Osmosis FO (P = 0) Water flux, J w 0 Flux reversal point (P = ) PRO (P < ) RO (P > ) P

6 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

7 The Forward Osmosis Process Feed Water Membrane Diluted Draw Solution Draw Solution Recovery Process Energy Input Concentrate Concentrated Draw Solution Product water

8 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

9 RO Energy Consumption Brine Permeate SE: Specific energy ΔP: Applied pressure π Β (R): Brine osmotic pressure at recovery R SE = ΔP π Β (R) Shaffer et al. (2014), in press, /j.desal

10 Comparing Energy of RO and FO-RO SE min = π Β π D is always > π Β SE min = π D Brine Permeate Draw

11 FO-RO Always Requires More Energy than RO Alone SE min (FO-RO) = π D > π Β = SE min (RO) Condition for net driving force in FO

12 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

13 Organic Fouling Reversibility in Forward Osmosis Flux (m/s) Flux of clean membrane Fouling Cleaning Flux after cleaning Time (min) 7 Flux (l/m 2 /h) FO membrane: CA (Hydration Tech) Organic foulant (200 mg/l alginate); 50 mm NaCl; 0.5 mm Ca 2+ Cleaning: 50 mm NaCl, increased crossflow, 15 min Mi and Elimelech, Journal of Membrane Science, 348 (2010)

14 FO Exhibits Fouling Reversibility with a Wide Range of Foulants 1.0 Flux recovery by rinsing Flux after fouling Normalized Flux Shaffer et al. (2014), in press, /j.desal Alginate BSA Gypsum Silica Foulant Type

15 In Situ Surface Modification for Fouling Resistance PEG PEG MPD+TMC O C Cl O C O Cl C Cl NH 2 -PEG O C NH O C NH Interfacial Polymerization PEGylation Polysulfone Support Layer Nascent Polyamide Layer In Situ Modified Membrane Lu et al. Environ. Sci. Technol. 2013, 47, Contact Angle ( ) Control Control In Situ Modified In Situ Modified

16 Modified Membrane Exhibits Organic Fouling Resistance Normalized water flux, J w /J w,0 (%) Control Polyamide In Situ Modified Cumulative Permeate Volume (ml) Normalized Water Flux, J w /J w,0 (%) Fouling Control Cleaning In Situ Modifed Lu et al. Environ. Sci. Technol. 2013, 47,

17 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

18 Current Focus: Reducing Structural Parameter of Membranes K t s D Membrane structural parameter, S Tortuosity, Thickness, t s Porosity, K Solute resistance to diffusion t s Support layer thickness Tortuosity support layer Porosity thin film (active layer) D Draw solute diffusivity

19 Significant Progress in the Past 10 Years TFC-RO TFC-FO S = 9583 μm S = 390 μm Yip et al. Environ. Sci. Technol. 2010, 44,

20 Low Structural Parameter is Critical for Obtaining High Water Flux Shaffer et al. (2014), in press, /j.desal

21 Challenge: Minimize Reverse Draw Solute Flux Feed Water Membrane Diluted Draw Solution J s Draw Solution Recovery Process Concentrate Concentrated Draw Solution Product water

22 The Driving Force for Reverse Draw Solute Permeation A highly concentrated draw solution generates the osmotic gradient that drives the flux of water J w J w A m J s The high concentration of draw solute also drives the reverse permeation of draw solute. n J s f cm Feed Draw

23 Analytical Expression for Reverse Solute Flux J s J ws J w cd, b exp cf, b exp D k A B J w J ws 1 exp exp J w k D J w J ws J w D, b exp F, b exp D k A B J w J ws 1 exp exp J w k D

24 Model Predicts Reverse Solute Flux for Salt and Neutral Solutes Predicted Solute Flux (mol m -2 h -1 ) Urea Ethylene Glycol Glucose NaCl Experimental Solute Flux (mol m -2 h -1 ) 60.1 g/mol 62.1 g/mol 0.72 nm g/mol Yong et al., Journal of Membrane Science (2012) 9 17

25 Reverse Flux Selectivity (RFS): An Important Design Parameter 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 J J w s A B nr g T

26 Membranes Are Constrained by the Permeability-Selectivity Tradeoff J J w s A B nr g T Goal: Maximize B A Yip et al. Environ. Sci. Technol. 2011, 45, Geise et al., Journal of Membrane Science 2011, 369 (1-2),

27 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

28 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

29 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

30 Applications in Oil and Gas Gregory et al., Elements, Vol. 7, 2011,

31 Applications in Oil and Gas: Very Hard to Treat Shale Gas Waters Upper Limit Conc. (mg/l) Gregory et al., Elements, Vol. 7, 2011, TDS: 260,000 Hardness: 55,000 Alkalinity: 1,100 Calcium: 31,000 Cannot be treated by pressure-driven membrane processes (RO/NF)

32 The Green Machine : Treatment of Water from Hydraulic Fracturing Source: Hydration Technologies Innovation (HTI)

33 FO Desalination with Thermolytic Draw Solutions Nature, 452, (2008) 260 Low-Grade Heat McCutcheon et al., Desalination, 174 (2005) 1-11.

34 Brine Concentrator for Treatment of High Salinity Shale Gas Wastewater TDS = 75,000 mg/l Oasys Water Inc. Desalination 312 (2013) TDS = 300 mg/l

35 FO in ZLD Schemes as Brine Concentrator Shaffer et al. (2014), in press, /j.desal

36 Pre-treatment for Conventional Desalination Technologies Shaffer et al. (2014), in press, /j.desal

37 The Promise Concluding Remarks 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

38 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