Assessment of physicochemical performance of draw compounds for desalination using multi-criteria analysis

Abstract The development of draw compounds for forward osmosis (FO) has been an active area of research. While a few studies have considered draw solutes for FO desalination, these are rarely presented with consistent units for objective performance comparison. To rectify this lack of knowledge, this study objectively compares draw solutes using a multi-criteria analysis (MCA) across a range of physicochemical properties (in consistent units), along with their flux performance when integrated with FO membranes. This analysis reveals that Ionic liquids (IL) have favorable physicochemical characteristics and generally higher flux performance in both nonresponsive and thermally responsive draw solute classes. In particular, magnesium chloride was found to be the optimal non-responsive draw solute. In addition, a diammonium cation-based iodide salt and an oligomer of choline chloride and an itaconic acid mixture were found to achieve the highest water flux of ~15LMH when treating seawater level salinity solutions within thermally responsive draw compounds. The MCA also revealed that hydrogels—particularly those based on poly(N-isopropylacrylamide) (PNIPAM)—are promising because they have the best dewatering capability but suffers from low water flux. Overall, we conclude that IL draw solutions and PNIPAM-based hydrogels represent some of the most promising FO draw compounds for future research.