Deep eutectic solvents in membrane science and technology: Fundamental, preparation, application, and future perspective

Deep eutectic solvents (DESs) are green solvents alternative to ILs with remarkable chemical tunability, which have proved themselves as one of the most promising elements of the membrane technology. Because of their exceptional biodegradability, biocompatibility, and ease of preparation along with chemical tunability, low vapor pressure, low viscosity, and nontoxicity, DESs are appealing candidates for developing polymeric membranes. Very recently, DES-supported membranes (DSMs) have been centered in the attention of researchers in diversified fields from biotechnology, extraction, wastewater purification, and gas separation to energy conservation and storage. Their high reactivity towards polymer chains, especially hydrogen bonding, brings about ion conductivity, efficient separation, and biodegradation. This review highlights DES in the membrane technology applications and undertakes recent advancements in the use of DESs in gas separation, treatment of contaminated waterways, liquid-phase microextraction, fuel cell, and batteries. Due to elevated mechanochemical properties and high selectivity and permeability, the DES-supported membrane has exhibited a high potential ability to be employed as a promising solution for discarding pollutants from polluted water streams and tackling the upcoming water crisis. A particular focus is placed on the fundamentals and various preparation techniques adapted to the most conspicuous features of DES-based membranes (DSMs), characterization of DSMs, and the mechanism of DES selectivity, purification of effluents, gas separation, diffusivity, and permselectivity of gaseous/aqueous molecules through polymeric membranes.