Imidazolium polymerized ionic liquid-based membranes for the sustainable Cr(VI) recovery from industrial effluents

This study aimed to address the critical challenge of recovering chromate ions from industrial wastewater using stable functionalized membranes. We developed and evaluated the possibility of incorporating imidazolium-polymerized ionic liquids (PILs) into a polymeric matrix by using an original acrylate formulation to copolymerize a series of imidazolium-based PILs, thus chemically entrapping them within the membrane matrix. Notably, the PIL with the longest aliphatic chain produced dense, homogeneous membranes that were easy to manipulate and suitable for studies on Cr(VI) recovery. The resulting membrane enabled the quantitative recovery of chromate in a 0.1 M NaOH solution. Membrane stability was rigorously evaluated over 18 successive cycles (24 h each) and only a 20 % decrease in the recovery efficiency was observed, demonstrating reliable performance and the potential for repeated use despite exposure to the alkaline solution employed for chromate recovery. Importantly, the membrane required no regeneration or activation treatment, facilitating continuous Cr(VI) recovery through membrane permeation. Moreover, the effect of pH on the recovery efficiency of Cr(VI) was investigated in the range pH = 2–9, revealing a quantitative extraction for pH above 7. Selectivity experiments revealed the membrane's affinity for Cr(VI) extraction over Cr(III) and other metal ions in synthetic water mixtures. Furthermore, the imidazolium PIL-based membrane exhibited high efficiency (ranging from 63 % to 82 %) in recovering chromate from industrial wastewater samples, underscoring its practical suitability for environmental remediation. Overall, this study highlights the potential of PIL-based membranes as sustainable and efficient materials for water treatment applications.