Layered double hydroxide driven 1O2 non-radical or •OH radical process for the degradation, transformation and even mineralization of sulfamethoxazole via efficient peroxymonosulfate activation

Abstract

As reported, PMS can be activated and decomposed into different reactive oxygen species such as 1O2, •OH and SO4•-, besides, coupling of non-radical (PMS direct oxidation) and radical (SO4•-) process could enhance the utilization efficiency of PMS. In this study, we proposed another strategy of 1O2-based non-radical and •OH-based radical process using layered double hydrotalcite (MgAl-LDH and MgAlCu-LDH) to regulate the degradation, transformation and even mineralization of sulfamethoxazole. Compared with PMS direct oxidation, SMX removal efficiency was increased from 41.8% to 71.7% by 1O2. However, there was almost no real degradation or mineralization since the ionization intermediates including C10H12N3O4S and C7H9N3O5S accumulated with reaction time according to DFT and LC-MSMS analysis. In comparison, 100% of SMX degradation was obtained via coupling 1O2 and •OH-radical process, in which the mineralization efficiency reached to 24.8%. Importantly, the above-mentioned intermediates of SMX were not detected and their accumulation were also significantly inhibited. Moreover, SMX degradation behavior and kinetics could be manipulated via direct oxidation, 1O2 and then •OH step by step, which was beneficial to enhance the PMS utilization efficiency. Finally, based on the results of zeta potential of MgAlCu-LDH, effect of solution pH on SMX degradation, the interfacial PMS activation process was responsible to regulate non-radical and radical process.