In this study, the quantum chemical descriptors such as highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy, HOMO‐LUMO energy gap, electrophilicity index, electronegativity, global hardness and global softness of five cations like 1‐butyl‐3‐methylimidazolium [BMIM]+, 1‐pentyl‐3‐methylimidazolium [PMIM]+, 1‐hexyl‐3‐methylimidazolium [HMIM]+, 1‐heptyl‐3‐methylimidazolium [HEPMIM]+ and 1‐octyl‐3‐methylimidazolium [OMIM]+ and five anions including butyl sulfate [BUSO4]−, pentyl sulfate [PENSO4]−, hexyl sulfate [HEXSO4]−, heptyl sulfate [HEPSO4]−, and octyl sulfate [OCTSO4]− and their combination of 25 ionic liquids (ILs) were predicted using ab initio method. To validate the findings, the sigma profiles and sigma potentials were generated for all the studied ILs. From this study, it was observed that imidazolium‐based ILs with smaller anion size is the most favorable IL for the removal of pollutants from their resources and/or effluents. © 2020 Wiley Periodicals, Inc.

Pollution by toxic, non-degradable metals is a rising health concern in the context of increasing industrialization and metal demand. Diseases may include brain damage, cardiovascular problems, gastrointestinal disorders and cancer, calling for advanced methods to clean soil, water, wastewater and air. Here, we review the use of ionic liquids, which are considered as eco-friendly solvents, to remove metals. Ionic liquids have unique properties such as no vapor emission, good solvation ability, higher thermal stability and tunability. Ionic liquids separate efficiently metal ions from aqueous solutions by electrostatic, Van der Waals and ion-pair interactions. Ionic liquids can be recovered by stripping, then reused several times for liquid-liquid extraction, adsorption and membrane separation. Ionic liquids improve membrane stability in membrane separation, and they act as surfactant for adsorption.

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