Attapulgite-supported sulfidated nano Zero-Valent Iron activated persulfate advanced oxidation technology for degradation of polyethylene microplastics: Optimal design, change of particle size and degradation mechanisms

Abstract

Microplastics (MPs), as a novel pollutant, have raised concerns about their potentialtoxicity and the wide-ranging ecological risks they may pose. In this study, a novel attapulgate-supported sulfidized nanoscale zero-valent iron (S-nZVI@ATP) catalyst was prepared for the activation of persulfate. We investigated the degradation efficiency and mechanism of polyethylene microplastics (PE) using the S-nZVI@ATP activated persulfate advanced oxidation process. Various factors, such as temperature,pH, catalyst dosage, and persulfate concentration, were evaluated for their influence on the oxidative reaction in the system to determine the optimal degradation conditions. The average particle size of PE decreased from 64.2±0.86μm to 28.1±0.91μm after 24 hours of oxidative degradation. The reaction progressed, TOC in the solution showed an initial increase, followed by a decrease. Some PE was oxidized into small molecules substances such as alkanes, alkenes, ketones, alcohols, and carboxylic acids. S-nZVI@ATP continuously supplied Fe2+ for persulfate activation, generating strong oxidants SO4•-, •OH, and 1O2, among which SO4•- played a dominant role in oxidation system. The heterogeneous advanced oxidation system provided in this study offers an effective reference for PE degradation and holds great promise as a method for degrading MPs in water.