Trace benzoquinone inducing periodate for tetracyclines selective degradation: Role of the unstable intermediate

Abstract

The binding behavior of tetracyclines (TCs) with natural organic matter and the subsequent induction of degradation in advanced oxidation processes has been underestimated. In this study, based on the specific oxidative effects of periodate, the selective degradation of TCs by periodate was achieved with benzoquinone (BQ) that induced poor stability intermediates. The periodate achieved the near complete degradation of TC with a trace concentration of BQ under the alkaline condition, with the kobs at 0.3090 min−1. The degradation experiments for twelve micropollutants revealed that the periodate/BQ system had a considerably efficient degradation only for TCs, and combined with the electron paramagnetic resonance (EPR) analysis, the minor involvement of reactive oxygen species during the degradation process was confirmed. The evident correlation between the observed kobs and the pre-mixing duration of TC with BQ demonstrated the dependence of the degradation process on intermediate generation. Furthermore, theoretical calculations revealed the reaction sites between the TC and BQ; the product identification and energy barrier of 18.94 kcal/mol further confirmed the interaction pathway through the Michael addition reaction. Moreover, based on the narrow energy gap (0.5350 eV) with the intermediate, only the periodate demonstrated efficient degradation of TC under alkaline conditions among the various oxidants. Little toxic iodine species were produced during the reaction, and the system exhibited resistance to natural water substances, such as anions and humic acid, highlighting its potential for application. In conclusion, the interaction mechanisms between TCs and BQ were elucidated in this research, and an efficient approach was proposed for eliminating residual TCs from aquatic environments and selective degradation from wastewater matrices.