Study on degradation of benzothiazolium-based ionic liquids by UV-H2O2

Abstract

Ionic liquids (ILs) are considered to be a new type of solvent due to their low vapor pressure, some unique properties and are expected to be used widely in the following days. Given their water solubility, stable chemical structure, and biological toxicity, ILs probably reach aquatic environments and become long-term pollutants. We studied the fate of benzothiazolium-based ionic liquids catalyzed by UV-H2O2 in water. Due to the synergistic effect of UV and H2O2, the degradation efficiency can be significantly improved compared to any of them alone. Fitting results showed that the degradation reaction follows pseudo-first-order kinetics and reaction rate constants with hydroxyl radicals ranging from 0.0005 s-1 to 0.0529 s-1. The experimental data showed that satisfactory results can be obtained at a temperature of 45 °C, an initial concentration of ionic liquid of 0.1 M, and a hydrogen peroxide concentration of 0.1 M. We also explored the effects of chloride ions and pH on degradation reactions. In an appropriate situation, the degradation yield of [C4Bth]PF6 could achieve 97% in 60 min and 99% in 90 min. The UV-H2O2 combination process could provide an effective technique for the treatment of benzothiazolium-based ionic liquids in wastewater.