Synergistic oxidation and adsorption of arsenic(III) by epigallocatechin gallate activated iron(III) peroxydisulfate system

Groundwater contamination in mining areas has become more severe, particularly due to elevated arsenic (As) pollution risks. Advanced oxidation processes by peroxydisulfate (PDS-AOPs) have demonstrated excellent efficiency in stubborn contaminants treatment. In this study, we propose a synergistic strategy involving polyphenol species and Fe(III) to enhance PDS activation, significantly enhancing arsenite (As(III)) oxidation and adsorption. The findings demonstrated that As(III) removal efficiency could achieve 98.2% within 10 min under the experimental condition (0.15 mM Fe(III), 0.2 mM PDS, and 0.02 mM epigallocatechin gallate (EGCG)), representing an increase of 84.4% compared to the Fe(III)/PDS without EGCG. This phenomenon is primarily due to the capacity of EGCG to chelate Fe(III) and facilitate its reduction, promoting the interconversion of Fe(III) and Fe(II) through enhanced redox cycling. The process in turn boosts the activation of PDS, leading to the production of reactive oxygen species such as SO₄^•⁻,·OH and O₂^•⁻, all of which contribute synergistically to the oxidation of As(III).This study also adopted density functional theory (DFT) calculation, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis to revealing the mechanism of As(III) removal. Besides, the As(V) adsorbed onto iron-based aggregate through the reaction is in the pentavalent state, indicating that the reaction system strengthens the oxidation of As(III). This study achieved efficient removal of As(III) and met the Chinese national standard of 0.01 mg/L, which provide the theoretical foundation for utilizing iron-based catalysts in PDS activation technology.