(210f) Membrane Compatibility With Switchable Polarity Draw Solutions For Use In Forward Osmosis Applications

Water scarcity is problem being faced worldwide and present in every continent. Close to one-fifth of the world’s population has difficulty acquiring safe water, and the problem is worsening as populations continue to grow in poorer countries. As the availability of unimpaired freshwater sources dwindles, cew water sources, such as the oceans and saline groundwaters, must be tapped.  However, desalination technologies are very expensive due to a high energy requirement.  Forward osmosis (FO) is a process which may be able to replace or become integrated with existing desalination technologies like reverse osmosis. FO relies on an osmotic agent, or draw solution, to drive water from a saline water source by osmosis.  The water dilutes the draw solution and a secondary separation process where the solute is removed and recycled.  This secondary separation step is key to FO process economics.  Recently, a classification of draw solutes, known as switchable polarity solvents (SPSs) have emerged.  These solvents become highly miscible with water upon sparging with CO₂ and phase separate when stripped with an inert gas.  One such SPS is N,N-dimethylcyclohexylamine.  This SPS has shown promise in early testing at Idaho National Laboratories.  However, because it is a solvent, membranes, which are polymeric, may not be compatible with the solution.  . This study examines the longevity of conventional osmotic membranes after exposure to relevant SPS solutions.  Membrane performance metrics, such as permeance and salt rejection as well as osmotic flux, are presented.