Aaron D. Wilson, Ph.D. Frederick F. Stewart, Ph.D. Use of Switchable Solvents as Forward Osmosis Draw Solutes Mark L. Stone, Ph.D. [email protected] 2013 Osmotically Driven Membrane Process Forward Osmosis Applications Water Purification/Desalination Methods Industrial Leaders in FO • Pure water is moved from a feed • Established Dilute • Hydration Technology Innovations (HTI) – Reverse osmosis (RO) FO Draw solution across a porous (OD product) membrane to a draw solution – Established cellulose triacetate (CTA) membrane supplier , • Membrane fouling currently developing and releasing more robust membranes. driven by the high osmotic – Smalll plant FO systems to energy drink pouches • Requires pressures greater than 50 atm of pressure pressure of the draw solutions. Feed • OASYS Water applied to a membrane FornaG.; Holt, J. K.; Stadermann, M.; Solution Fully Processed – Commercialization of recently developed polyamide thin film Grigoropoulos, C. P.; Noy, A.; Bakajin, O. Ion • Recovers only 35-50% water from sea water Water • FO with Conventional draw composite membranes Exclusion by Sub-2-Nm Carbon Nanotube Pores. Concentrated (FO Product) – Distillation FO Draw solutes ensures a homogenized – Unconventional ammonium carbonate FO draw system PNAS 2008, 105, 17250–17255.siero, F.; Park, H. Concentrated • Mature Material feed solution for an RO finishing • Modern Water (DOC product) • Energy intensive. FO Cell RO Cell step which otherwise suffer from – FO systems and plants (Osmotic Driving Force debilitating fouling. – 2nd Plant - a 200 cubic meter per day FO desalination facility • An alternative PRO product) Forward osmosis desalination plant at Al Najdah, Oman completed September 2012. Modern Water at Al Khaluf, Oman. – Forward osmosis (FO) • Standing challenges in FO: • Porifera HTI and Emerald Surf Sciences • Reduced fouling vs RO – An unconventional draw solute that can be removed by means – Membrane developer other than RO while retaining significant osmotic pressure. – Conventional FO-RO system for the US Army which is more • Higher water recovery and reduced waste stream 1) Draw solute is incorporated into the product . 2) Draw solution must be removed through cost effective than RO. volume vs RO – A FO membrane that is more robust than cellulose tri-acetate • Emergencies energy drink production. reverse osmosis. (CTA). (many solution being pursued and delivered) • Fuji Film • Lower energy requirements than distillation • Water for evaporative cooling. • Desalination. – Unconventional draw system Cath, T. Y.; Childress, A. E.; Elimelech, M. Forward osmosis: Principles, applications, McCutcheon, J. R.; McGinnis, R. L.; • Frac completion fluid /recovery fluid. • Low-temperature food products concentration. – Membranes Elimelech, M. A novel ammonia--carbon Desalination of Seawater; American Water Works Association, 2011. and recent developments. Journal of Membrane Science 2006, 281, 70–87. • Landfill/Mining Lechate. dioxide forward (direct) osmosis desalination process. Desalination 2005, 174, 1–11.
Brief History of Switchable Materials Maximum Concentration of SPS Freezing Point Osmometry
• Switchable polarity solvents (SPSs) SPS as Next Generation FO Draw Solutes 18.0 5' 4 y = 1.7274x - 0.0303 are not limited to exotic guanadines 16.0 3.5 R² = 0.9988 and amidines but inlcude tertiary • High concentration in polar form. 14.0 3' 11' amines simple enough for production 1' 3 • Can be mechanically separated once switched to non-polar form. 12.0 on a massive scale. (logKOW listed) 6' 10.0 12' 15' 2.5 7' 6' 2 8.0 7' 16' 2' 11' 6.0 Osm/Kg
molal molal (mol/Kg) 1.5 y = 0.8806x - 0.0303
12' 4.0 15' R² = 0.9988 8' 1 2.0 4' 9' 13' 16' 10' 14' 16" 0.5 N,N-dimethylcyclohexylamine N,N-dimethylcyclohexylammonium 0.0 • Commodity scale polyurethane bicarbonate 5 6 7 8 9 10 11 12 13 14 0 0 1 2 3 4 5 Jessop, P. G.; Phan, L.; Carrier, A.; polymerization catalyst. • A concentration derived form 1:1 (v:v) Jessop, P. G.; Heldebrant, D. J.; Li, Jessop, P. G.; Kozycz, L.; Rahami, Z. G.; Carbon:Nitrogen Ratio mol/Kg Robinson, S.; Durr, C. J.; Harjani, J. Schoenmakers, D.; Boyd, A. R.; Wechsler, D.; Holland, • $62.40 per Liter from Aldrich amine:water solution forms 7.6 mol/Kg or • Comprehensive structure function screening X.; Eckert, C. A.; Liotta, C. L. Green R. A solvent having switchable Freezing point osmometry dimethylcyclohexylammonium A. M. Tertiary amine solvents having switchable (filled blue diamonds) maximum amine concentration chemistry: Reversible nonpolar-to- hydrophilicity. Green Chem. 2010, • ~$1.0 per Kg at the ton scale. 59wt% at 25 C with 1 atm CO2 which bicarbonate solution based on amine concentration (blue hydrophilicity. Green Chem. 2011, 13, 619–623. (1) Stone, M. L.; Rae, C.; Stewart, F. F.; Wilson, A. D. Switchable polar solvent. Nature 2005, 436, 1102. 12, 809-814. extrapolates to 13.2 Osm/Kg (open red diamonds) maximum carbonic acid concentration. polarity solvents as draw solutes for forward osmosis. diamonds) and total solute concentration (red squares). • It has since been demonstrated that 2:1 (v:v) Desalination 2013, 312, 124–129. • Two forms of SPS with different ratios of amine amine:water solution forms a solution which (2) Wilson, A. D.; Stewart, F. F. Deriving osmotic pressures of • The maximum solubility of NaCl is 6.14 mol/Kg with a 13.8 Osm/Kg. to carbonic acid. has a total solute concentration of 35.2 mol/Kg draw solutes used in osmotically driven membrane processes. • The maximum total solute concentration of a Journal of Membrane Science 2013, 431, 205–211. • Study indicates how additional switchable and 760 atm of osmotic pressure. dimethylcyclohexylammonium bicarbonate solution is 35.2 mol/Kg (3) Wilson, A. D.; Stewart, F. F. Structure-Function Study of materials can be designed. Tertiary Amines as Switchable Polarity Solvents. manuscript in or 31.0 Osm/Kg which should extract water from a fully saturated SPS as FO Draw Solute preparation 2013. brine solution resulting in the precipitation of NaCl. Experimental Set-Up
Water Flux Experiments Removal of Trace Organics 35 35 30 Hydrophobic 30 Positive Flux Against: SPS + Organics 25 25 5 mol/Kg NaCl
hr) 2
hr) 20
2 226,000 ppm TDS 20 + CO2
275 atm 15 15 Dilute - CO2
flux (L/(M flux 2 Organics flux (L/(M flux 18.8 L/(m h) Hydrophilic 10 10 weighted average SPS + Water for the removal of Organics 5 5 75% of the water
0 0 0 1 2 3 4 5 6 0 0.2 0.4 0.6 0.8 1 Hydrophilic 30 ⁰C NaCl (mol/Kg) vol fraction removed from NaCl 0.5 molKg solution 30 SPS PRO mode ⁰C • Persistent Organic Pollutants (POPs) are a growing concern to health
Draw solution 7.6 mol/Kg by amine (active layer draw solution) PRO mode and safety. The SPS FO system acts as a repeated solvent extraction 400 ml/min • NaCl at 0.5 mol/Kg is considered a reasonable model for 35 salinity sea water ~3.5 wt%. process which can concentrate organics for convenient disposal. • Our system has a 18.8 L/(m2h) weighted average for the removal of 75% of the water. • Toluene (water solubility 0.47 g/L, logKOW= 2.69) favors the organic 2 phase (1,200 µg/ml) over the aqueous phase (110 µg/ml). The majority • Instead of putting membranes under high pressures (50 atm) the HTI cartridge FO membrane: cellulose • Compares favorably with the 14-20 L/(M hr) used in commercial Sea Water RO for the of POPs have a higher logK (3.0-8.2) which would favor the organic solutions are exposed to carbon dioxide pressures that differ by as triacetate embedded about a polyester removal of less than 60% of the water. OW phase more dramatically. little as 1 atm. screen mesh
Conclusion Acknowledgements Total SPS FO System Energy Cost of • Switchable polarity solvents are draw solutes that allows an entirely new • LDRD Ammonia-CO2 vs. SPS FO FO process for the purification of water and concentration of solutions. • Royalty Fund Low and Constant Pressure – The SPS FO system is expected to save costs because its driven by heat rather than electricity. Heat is at least 1/10th the cost of RO Finishing electricity. • The SPS FO system demonstrated substantial osmotic pressures and • Phase separation of solute avoids “solution FO flux. polarization”, the increase in feeds solution – This osmotic pressure allows for greater concentration of the feed concentration with the removal of water. solution reducing the waste volume compared to RO and • Expected to require substantially lower pressures conventional FO systems. than conventional RO. • Demonstrated on a 4 L scale >95% was purified with • The material compatibility remains the greatest challenge but can be *X is the stoichiometric excess of NH used to maintain solute solubility. existing sea water RO technology (Polyamide Thin- 3 solved by: Film Composite Membrane) 99.65% rejection of • The SPS FO system will phase separate from water – designing and selecting materials/membranes stable to dimethylcyclohexylamine. without bring the solution to near reflux.** dimethylcyclohexylamine.
**HANCOCK, N. Engineered Osmosis for Energy Efficient – or designing a better SPS based on our structure function study. Separations: Optimizing Waste Heat Utilization FINAL SCIENTIFIC REPORT DOE F 241.3 DE-EE0003467; 2013.