Ionic liquids in wastewater treatment: A review on pollutant removal and degradation, recovery of ionic liquids, economics and future perspectives

Wastewater treatment with ionic liquids is getting attraction worldwide among environmentalists and industrialists. Modernization of life and industrial expansion has let to generation of huge quantity of wastewater. It is of urgent need to treat wastewater for better usage for future generation. Most important parameter that defines the treatment strategy are wastewater composition, source, geographical location, etc. In this review we have focused on dye, heavy metal and organic wastewater sources and its role on environment damage. Further ionic liquids properties were explored for suitability in wastewater treatment process. Ionic liquids exhibit density of 1 to 1.6 g/cm(3) and viscosity of 4 to 730 mPa.s respectively. Ionic liquids showed removal efficiency of > 90% for dyes and phenolics. Ionic liquids exhibited 90 to 99% removal of heavy metals like cadmium, copper and zinc. Sodium hydroxide-based washing provided 97% of ionic liquids recovery after pollutant removal process. Ionic liquids exhibited pseudo-second-order kinetics and mechanisms like hydrogen bonding, hydrophobic effects, pi-pi and electrostatic interactions during the pollutant removal process. However, steps to reduce the overall economics of utilizing ionic liquid in wastewater treatment needs to be further explored as it a challenging factor in commercialization. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Ionic liquids have shown high removal efficiency in wastewater treatment, particularly for dyes, heavy metals, and organic pollutants. However, reducing the economic cost of using ionic liquids remains a challenge.