Prospect of ionic liquids and deep eutectic solvents as new generation draw solution in forward osmosis process

Forward osmosis (FO) can aptly contribute to increased water reuse at the expense of low energy expenditure. The distinctive feature for FO lies with the exploitation of the natural osmotic pressure gradient generated by a concentrated draw solution for water transport across a semi-permeable membrane. The selection of a suitable draw solution remains to be a grey area of commercial development of FO process. The present review summarizes the importance of ionic liquid (IL) and deep eutectic solvent (DES) with natural product components and their potential as draw solutions in FO and their industrial applications. Various factors affecting performances of ILs and DESs as draw solutions are briefly assessed and critically compared with pertinent literature. Regeneration of IL and DES as spent solution from the process, as well as pure water recovery is discussed with special reference to heat energy optimization. A future pathway for research in IL and DES as draw solute and their economic aspects are also highlighted.