Photocatalytic degradation of alkyl imidazole ionic liquids by TiO2 nanospheres under simulated solar irradiation: Transformation behavior, DFT calculations and promoting effects of alkali and alkaline earth metal ions

Xuejing Xiao; Ruixue Guo; Yumeng Qi; Junyan Wei; Nannan Wu; Shengnan Zhang; Ruijuan Qu

doi:10.1016/j.jhazmat.2023.132616

Photocatalytic degradation of alkyl imidazole ionic liquids by TiO₂ nanospheres under simulated solar irradiation: Transformation behavior, DFT calculations and promoting effects of alkali and alkaline earth metal ions

J Hazard Mater. 2024 Jan 5:461:132616. doi: 10.1016/j.jhazmat.2023.132616. Epub 2023 Sep 22.

Authors

Xuejing Xiao¹, Ruixue Guo¹, Yumeng Qi¹, Junyan Wei¹, Nannan Wu¹, Shengnan Zhang¹, Ruijuan Qu²

Affiliations

¹ State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, PR China.
² State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing, Jiangsu 210023, PR China. Electronic address: quruijuan0404@nju.edu.cn.

PMID: 37757564
DOI: 10.1016/j.jhazmat.2023.132616

Abstract

In this study, TiO₂ nanospheres prepared by the sol-gel method were found to efficiently catalyze the photodegradation of 1-butyl-2,3-dimethylimidazolium bromide salt ([BMMIm]Br) under simulated solar irradiation through the main attack of hydroxyl radicals (•OH). The promoting effect of alkali metal (Li⁺→Cs⁺) and alkaline earth metal ions (Mg²⁺→Ba²⁺) was particularly emphasized. In-situ EPR tests showed that the introduction of alkali and alkaline earth metal ions could enhance the formation of •OH thus leading to a 7%-30.3% increase in the degradation efficiency of. [BMMIm]⁺. Moreover, the removal efficiency of [BMMIm]⁺ still reached > 96.19% in four real waters. A total of 23 products of [BMMIm]Br were detected, and hydroxyl substitution, bond breaking, direct oxidation and ring opening were considered as the main reactions during the photocatalytic degradation process. The results of toxicity evaluation showed that hydroxylation was a reaction process of increasing toxicity, while the bond breaking reaction had great detoxification capacity for [BMMIm]⁺. These findings may enhance our understanding on the effects of alkali or alkaline earth metal ions on the photocatalytic activity of TiO₂, which could also provide reference for the efficient and green removal of alkylimidazolium ionic liquids in waters.

Keywords: Alkali and alkaline earth metal ions; Alkyl imidazole ionic liquids; Photocatalysis; Reaction mechanism; TiO(2) nanospheres.