Novel-supported ionic liquid membranes for an effective removal of pentachlorophenol from wastewater

Abstract

Recently ionic liquids (ILs) have been useful in many areas of wastewater treatment and separation processes in environmental engineering, such as supported ionic liquid membranes (SILM) based separations and solvent extraction applications. In this work novel ILs, namely 1-butyl-2,3-dimethyl imidazolium hexafluorophosphate [C4DMIM][PF6], tetrabutyl–phosphonium exafluorophosphate [TBP][PF6] were immobilized on PVDF (polyvinylidene fluoride) membrane for the removal of organic pollutant such as pentachlorophenol (PCP) from the water phase by SILM. Operating conditions like pH, feed and permeate concentration, membrane flux, and the mechanism was also studied. The interactions of H+ bonding, hydrophobic interactions, and carbon–π bonding interactions are explained via the SILM transport mechanism. The membranes were characterized by SEM, EDX, and FTIR analysis. In the experimental study, a high zetapotential of −93.24 mV was achieved, which is an indication of the excellent stability of SILM. At a pH of 4, [TBP][PF6] had the highest penetration rate of 87%. In contrast, [C4DMIM][PF6] yielded 79% after 30 h of experimentation at the feed pH 4. Similarly, after 30 h, [TBP][PF6] got the highest rate of permeation (80.50%), followed by [C4DMIM][PF6] (73.00%). The 0.1 M NaOH was used as a stripping agent in this study. PCP was successfully separated from the aqueous phase using two different hydrophobic ionic liquids as [C4DMIM][PF6] and [TBP][PF6]. This SILM technique has the potential in the future for further developments and for extracting organic contaminants from wastewater on a laboratory or industrial scale.