REVERSE OSMOSIS AND FORWARD OSMOSIS LABORATORY EXPERIMENTS

Transcription

1 REVERSE OSMOSIS AND FORWARD OSMOSIS LABORATORY EXPERIMENTS Jeffrey McCutcheon Associate Professor University of Connecticut Department of Chemical & Biomolecular Engineering

2 View video of lecture here:

3 Hartford Courant 3 A Story of a Thirsty University UConn Announces $2 Billion Expansion

4 4 If it is this bad in Connecticut a place that gets 50 inches of rain per year how bad must it be in truly arid regions?

5 Global Water Crisis Children Economic Every minute a child dies of a waterrelated disease Water Crisis For every $1 spent on water and sanitation there is a $4 economic return Women Sanitation Women and children spend 140 million hours a day collecting water References: Water 1 in 9 people lack access to safe water More people have a mobile phone than a toilet 5

6 Global water use (km 3 ) 6 Growing Markets for Water and Power Every million dollars of GDP = 22,000 m 3 /yr additional water Lux Research U.S. Water Usage (2000) Thermal power generation 48% Other 2% United States Geological Survey Industry 5% Public supply 11% Irrigation 34% GDP correlates strongly with energy use We must augment existing water supplies by tapping unconventional resources

7 Global Water Distribution References: Igor A.Shiklomanov, State Hydrological Institute (SHI, St. Petersburg) and United Nations Educational, Scientific and Cultural Organization (UNESCO, Paris),1999 7

8 A Lesson from Nature Biomimicry is common in membrane separations today. Membranes are designed to be like biological membranes with superior permselectivity Membranes are thin, selective barriers that allow certain chemical species to permeate through them while rejecting others Desalination Special Issue on Recent Advances in Forward Osmosis 8

9 Desalination around the world Membrane Technologies Thermal Technologies

10 Osmotic pressure p P> p J = Water flux A = Water permeability DP = Hydraulic pressure difference Dp = osmotic pressure gradient Saltwater Osmosis Reverse Osmosis Membrane Freshwater p RTC p = osmotic pressure R = gas constant T = temperature C = concentration of molecules J A( DP Dp ) W 10

11 Limitations of RO Elimelech, Science 333, 2011 Approaching the thermodynamic minimum energy for separation for desalination Unable to handle high salinity feeds Few breakthrough improvements that would reduce RO energy use are possible 11

12 Forward Osmosis J = Water flux A = Water permeability p draw = osmotic pressure of the concentrated draw solution p feed = osmotic pressure of the dilute feed solution Dilute solution Membrane Concentrated draw solution? J W A p p ( draw feed ) 12

13 Desalination, Reuse, and Dewatering Saline/Impaired Water Membrane Energy Input Draw Solution Draw Solute Recovery Brine Spontaneous Process Clean Water Adapted from McCutcheon, McGinnis, Elimelech, Desalination, 174 (2005)

14 14 Osmotic Dilution Membrane Saline Water Draw Solution Diluted draw solution Brine Spontaneous Process

15 Other Uses for Osmotic Pressure? Osmotic pressure is a physical manifestation of a chemical potential difference PRO offers a unique way of converting chemical potential energy into electrical energy by using a hydraulic energy intermediate J W = A(Dp DP) W = (E) x (DP) x (J W ) Achilli, Journal of Membrane Science 343, 2009,

16 16 Naturally Occurring Salinity Gradients Nile River Mississippi River Dead Sea Great Salt Lake Saline water acts as a source of chemical energy

17 Pressure Retarded Osmosis (Open Loop) Membrane Work Freshwater P X Draw Solution (Seawater) Diluted draw solute Mix and discard to draw source J W = A(Dp DP) Dp> DP W = (E) x (P) x (J W ) 17

18 Pressure Retarded Osmosis (Closed Loop) Membrane Work Energy Input P X Draw Solution Draw Solute Recovery Pure water working fluid J W = A(Dp DP) Dp> DP McGinnis, Journal of Membrane Science, 305, 2007, W = (E) x (P) x (J W ) 18

19 19 Misconception # 1 about FO Forward osmosis will replace reverse osmosis RO is an excellent technology for low to moderate salinity feeds, but. FO can do many things that RO cannot Handle high salinity waters Directly handle liquids with a high fouling propensity FO can often work in tandem with RO as a complimentary process

20 20 Misconception #2 about FO Forward osmosis uses less energy than reverse osmosis There is no such thing as a free lunch FO can use free or less costly energy than RO FO may lower the cost of desalination and reuse

21 21 Opportunities for FO Difficult waters High salinity High TDS/TSS Materials that are sensitive to heat and pressure Utilization of low grade energy Power production? Carl Lundin, CDM-Smith, IFOA Meeting, 2014

22 22 What folks care about Membrane Draw solution Process design

23 23 What folks care about Membrane Draw solution Process design

24 Types of Membrane Materials X X X X X Baker, R. Membrane Technology and Application, 3 rd Edition Dong, G., Li, H., Chen, V., Journal of Materials Chemistry A, 1, 2013,

25 Challenges with Membrane Design S t Conventional RO Membranes McCutcheon, McGinnis, Elimelech, Desalination, 174 (2005) Conventional asymmetric membranes structures cause severe mass transfer resistance during osmosis Commercial FO Membrane 25

26 The Problem with Asymmetry J W A p D p F J W A p D, m p F, m J W J W Ap A p J exp W F k, D, eff D, b p k eff D eff b DS JW S exp F D, S D, b p b J exp W DS t J exp W k D S F S k F McCutcheon, J.R., Elimelech, M. Influence of concentrative and dilutive internal concentration polarization on flux behavior in forward osmosis, Journal of Membrane Science 284, 2006, Low S means high water flux performance (as long as the membrane can be handled and manufactured)

27 Desired Properties of FO Membranes Properties of RO Membranes High permeability High selectivity Chemical resistance Thermal stability Requires anisotropic membrane with appropriate polymers (like TFC RO membranes) + Mechanically strong Easy to manufacture Tolerate high pressure For fabrication and handling Large areas needed For pressure retarded osmosis + Support layers that are thin, highly porous, non-tortuous (low S) and hydrophilic Requires new membrane designs, materials, and formation techniques 27

28 Commercial Membranes for FO 60 year old technology Easy to manufacture Low selectivity Low permeance Common in UF and MF, specialty RO 30 year old technology Tunable properties High selectivity High permeance Vast majority of RO membranes Garcia-Castello, E.M., McCutcheon, J.R., and Elimelech, M. Journal of Membrane Science 338, 2009, Ren, J., McCutcheon, J.R. Desalination 343, 2014, Arena, J.T., Manickam, SS, Reimund, K.K., Brodskiy, P., McCutcheon, J.R. Industrial & Engineering Chemistry Research. In revision

29 29 What folks care about Membrane Draw solution Process design

30 What Makes a Good Draw Solution: General Criteria 30 Osmotic efficiency: Low molecular weight and high solubility Removable, recoverable, or useable: Low value energy for reuse Non toxic: Trace amounts may reside in the water System compatible: Does not degrade the membrane or the system

31 What Makes a Good Draw Solution? 31

32 32 What Makes a Good Draw Solution? Criteria Osmotic Efficiency Recoverable Non Toxic System Compatible Comments

33 33 What Makes a Good Draw Solution? Criteria FO Osmotic Efficiency Yes Recoverable Essential Non Toxic Yes System Compatible Comments Yes Minimal leakage

34 34 What Makes a Good Draw Solution? Criteria FO Dewatering Osmotic Efficiency Yes Yes Recoverable Essential Optional Non Toxic Yes Optional System Compatible Comments Yes Minimal leakage Yes Minimal leakage

35 35 What Makes a Good Draw Solution? Criteria FO Dewatering Osmotic dilution Osmotic Efficiency Yes Yes Yes Recoverable Essential Optional No Non Toxic Yes Optional End use dependent System Compatible Yes Yes Yes Comments Minimal leakage Minimal leakage Direct use required

36 36 What Makes a Good Draw Solution? Criteria FO Dewatering Osmotic dilution Open Loop PRO Osmotic Efficiency Yes Yes Yes Yes Recoverable Essential Optional No No Non Toxic Yes Optional End use dependent No System Compatible Yes Yes Yes Yes Comments Minimal leakage Minimal leakage Direct use required Naturally Occurring

37 37 What Makes a Good Draw Solution? Criteria FO Dewatering Osmotic dilution Open Loop PRO Closed Loop PRO Osmotic Efficiency Yes Yes Yes Yes Yes Recoverable Essential Optional No No Essential Non Toxic Yes Optional End use dependent No No System Compatible Yes Yes Yes Yes Yes Comments Minimal leakage Minimal leakage Direct use required Naturally Occurring Leakage OK

38 38 Recoverable Draw Solutes Physically Recoverable Ionic solutes or magnetic nanoparticles Novel Draw Solutes Thermolytic Decomposition Solutes containing ammonia and/or carbon dioxide Thermal Solubility Polymers and hydrogels with low lower critical solution temperature Distillable Volatile solutes (ethanol, etc.) Phase Switching Switchable polarity solvents (CO 2 -catalyzed acid base reaction)

39 39 What folks care about Membrane Draw solution Process design

40 Commercialization of Forward Osmosis McGinnis, et. al., Desalination, 312 (2013)

41 Hydration Technology Innovations: Produced Water Saves nearly 1 million gallons of water per well (20% of total fluid need) Up to 150 fewer truck loads per well 41

42 Hydration Technology Innovation: Osmotic Dilution Can produce a clean, safe drink from nearly any water source Butler, Desalination 312 (2013),

43 Modern Water: Forward Osmosis Seawater Desalination Claims lower energy use and fouling combined with high boron rejection 43

44 Oasys Water: Oilfield Produced Water 42% reduction in cost compared to distillation McGinnis, et. al., Desalination, 312 (2013)

45 Statkraft: Open Loop Pressure Retarded Osmosis 45 Now divested from PRO

46 Your experiments

47 Reverse Osmosis Evaluate performance of reverse osmosis/nanofiltration membrane NaCl/MgSO4 Control temperature, flow rate, pressure Pure water permeance A = J w P Solute permeability J s = B C What you will measure m J w = A m ρ t J w = Water Flux m = Mass change in balance ρ = Density of water t = Time A m = Membrane area J s = c A m t J s = Solute flux c = Concentration difference between feed and permeate B = J w 1 R R exp J w k mt % Rejection R = 1 C p C b

48 Concentration Polarization Laminar masstransfer boundary layer c p Permeate water flux J W x c c m c b Solute balance: Turbulent CP modulus c c m b J c c m b W c exp c c p p D dc dx J JW D W c p Integrate over JW exp D c p << c m,c b exp k J k D 48 W

49 Forward Osmosis What you will measure m J w = A m ρ t J w = Water Flux m = Mass change in balance ρ = Density of water t = Time A m = Membrane area J s = c A m t J s = Solute flux c = concentration change from beginning to end of test Commercial FO membrane NaCl draw solution Evaluate effects of concentration polarization Control temperature, flow rate, draw concentration