The degradation of 1-ethyl-3-methylimidazolium chloride ionic liquids by simulated and natural sunlight activated persulfate: Degradation kinetics, mechanisms and pathways

Abstract

Ionic liquids (ILs) have high chemical stability and resistance to biodegradation, and their highly efficient removal from the water environment is imminent due to their potential ecotoxicity and environmental risks. Yet, current degradation methods are inefficient for ionic liquids even if activation of persulfate (PS) is enhanced by vis with the presence of catalysts. In this study, a simple and high-efficient simulated solar to activate PS was conducted for the degradation of 1-ethyl-3-methylimidazolium chloride (C2mimCl). The results revealed that over 99 % of C2mimCl was degraded by solar activated PS within 4 h at 25 °C. The degradation of the C2mimCl still exhibited excellent performance under natural sunlight activated PS, providing the practical application value. Based on density function theory (DFT) calculation and major intermediates determined by ultra-high-performance liquid chromatography triple quadrupole mass spectrometry (UHPLC-TQ-MS), the first major sites of C2mimCl to be attacked were the C atoms on imidazolium ring, followed by the alkyl side chain, and the degradation of C2mimCl was mainly carried out by imidazolium ring oxidation, C–N bond breakage and elimination reactions. Consequently, the findings of this work may provide new insight on the degradation of ILs by solar activated PS with excellent practical application.