Quaternary amine synthesized ionic polymer for efficient removal of Cr(VI) in waste water

Abstract

A series of imidazolium-based ionic polymer (ImIP2Br, ImIP3Br and ImIP4Br) were successfully prepared by quaternization reaction of 1,4-dimethyl bromide benzene, 1,3,5-tri(bromomethyl), 1,2,4,5-tetramethyl and 1,3,5-tri(1H-imidazol-1-yl)benzene. The as-prepared ImIP2Br, ImIP3Br and ImIP4Br ionic polymers were characterized by SEM, STEM, FTIR, TG and solid-state 13C NMR measurement. In the aqueous solution of [imidazolium] to [Cr] 1:1, the removal rate of Cr(VI) by ImIP4Br was 98.4%, which was much higher than that of ImIP2Br, ImIP3Br. In addition, the ImIP4Br was applied for efficient removal of Cr(VI) for extremely low concentration of Cr(VI) solution and electroplating industry wastewater by anion exchange. Finally, a series of experimentals studies were performed to study the enrichment of hexavalent chromium and evaluate the recycling and reproducibility of ImIP4Br. The result showed the concentration of the residual Cr(VI) is only 0.09 mg L−1, which is lower than the permissible limit of Cr(VI) discharge (0.10 mg L−1) according to the regulations of the US Environmental Protection Agency. For the actual electroplating wastewater, the adsorption efficiency of ImIP4Br for Cr(VI) is over 99.8%, despite the competitive adsorption of other ions in the solution. In a word, ImIP4Br shows outstanding enrichment ability, good regenerative ability and superior recyclability for removal of Cr(VI). The combination of promising removal performances endows ImIP4Br with great promises for capture and separation of Cr(VI) from contaminated water systems.