Application of deep eutectic solvents in water treatment processes: A review

Over the past decade, deep eutectic solvents (DESs) have gathered considerable attention in the research for functional and green solvents. The significant focus on the utilization of DESs can be attributed to their economic benefits over ionic liquids (ILs), practical usage through their flexible design, and environmental safety linked to their potential biodegradability and low toxicity, as well as low vapor pressure. Since their development in 2003, DESs have proved to offer tremendous opportunities, opening new perspectives as novel and refined materials. To date, significant advances have been achieved in the synthesis and applications of DESs, with more than ten thousand journal papers documented on this topic across different scientific fields. In particular, the use of DESs in water and wastewater treatment has rapidly emerged as a promising application area for advancing industrial and analytical processes given their beneficial and unique physicochemical properties. This review surveys the state-of-the-art on the application of different classes of DESs in water purification treatment, focusing on membrane separation, and microscale extraction processes. The current problems in the integration of DESs in water treatment processes and technologies are mentioned, and potential research directions to address the challenges are recommended.