Chemical Modeling of the TMA–CO2–H2O System: A Draw Solution in Forward Osmosis for Process Water Recovery

Abstract

Forward osmosis (FO) is an innovative membrane-based process that requires limited external energy input to recover water as it relies on the spontaneous osmotic pressure gradient between a process water stream and a more concentrated solution; the latter is termed a “draw solution”. A suitable draw solution should have properties that allow its solute to be separated into recoverable products that can, in turn, be used to regenerate the initial draw solution with minimum energy requirements. These properties are crucial for the economics of the FO process because the basic energy requirement in FO arises from the separation and regeneration of the draw solution. Recently, it was proposed that such a draw solution can be an aqueous carbonated trimethylamine solution (TMAH:HCO3). In this project, the properties, i.e., composition, pH, and vapor–liquid equilibria (VLE), of the binary TMA–H2O and the ternary TMA–CO2–H2O systems were studied to generate thermodynamic data required to enable accurate speciatio...