Computer Simulations to Study the Mechanisms of Cold Plasma-Induced Degradation of Amoxicillin

Due to the increasing water pollution worldwide, wastewater treatment remains one of the most important issues. Cold atmospheric plasma (CAP) has emerged as a promising and versatile technology for wastewater treatment in recent years, offering potential advantages in terms of effectiveness and cost-efficiency. Although several studies have been conducted, the mechanisms by which CAP degrades antibiotics, one of the main pollutants in pharmaceutical wastewater, remain unclear. In this study, we investigate the degradation mechanisms of the antibiotic amoxicillin using reactive molecular dynamics simulations. Specifically, we explore the interaction mechanisms between reactive oxygen and nitrogen species (i.e., O, OH, HO₂, H₂O₂, O₃, NO, NO₂, NO₂¯ and NO₃¯) generated by CAP and the amoxicillin molecule. Our simulation results reveal that some of these species form weak attractive (HO₂, H₂O₂, NO₂¯ and NO₃¯) and weak repulsive (NO and NO₂) interactions, whereas O₃ exhibits both weak attractive and weak repulsive interactions with the amoxicillin molecule. OH radicals exhibit the same interaction mechanisms as O atoms; in other words, O atoms react with amoxicillin in a manner similar to two OH radicals. The simulation results for O atoms show that their reactions with amoxicillin lead to the formation of hydroxyl and hydroperoxide groups, the opening or breakage of the β-lactam ring, the shortening or widening of the benzene ring, and the fragmentation of the structure. Our findings are consistent with experimental outcomes on CAP treatment of amoxicillin. This study provides a deeper understanding of the mechanisms of antibiotic degradation by CAP in wastewater treatment.