A review on the recovery methods of draw solutes in forward osmosis

Recently, there has been an increasing use of forward osmosis (FO) technique for energy-efficient water treatment, leading to significant public concerns. One key know-how to make FO practical is developing an ideal draw solute characterized by high water flux, low reverse solute flux, and easy recovery. The recovery of draw solutes takes a significant energy cost in FO technology implementation. To this end, it is necessary to enhance the understanding of how different kinds of draw solutes are regenerated during the dewatering process. This review aims to provide a comprehensive overview of current knowledge of draw solutes in terms of recovery from water. A variety of existing recovery methods developed so far to overcome the recovery barriers, including thermal separation, membrane separation, precipitation, stimuli-response, combined processes, and direct use without recovery are presented. Discussions on the advantages and limits of the existing recovery methods are made based on acquired knowledge from the literature. Future directions for the effective and energy-efficient recovery of draw solutes are also provided. Information summarized in the paper further highlights the potential applications of the FO process.