Enhanced Arsenite Remediation in Synthetic FeS ₂ /Fe(II)-Containing Arsenic Wastewater via Epigallocatechin Gallate-Initiated Persulfate Activation

High Resolution Image Download MS PowerPoint Slide The Fe(II)-catalyzed persulfate (PS) activation system demonstrated the ability to remove pollutants, such as As(III), from groundwater, including FeS 2 /Fe(II)-enriched mine drainage; however, the slow conversion rate of Fe(III) to Fe(II) limited the overall efficiency of the process. In this study, natural polyphenols (EGCG) was introduced in the FeS 2 /Fe(II)/PS system to enhance the long-term recycling of Fe(II), significantly improving the removal of As(III) within 10 min. The results showed that the addition of 0.025 mM EGCG to the FeS 2 /Fe(II)/PS system, under conditions of 0.1 g/L FeS 2, 0.1 mM Fe(II), and 0.25 mM PS, remarkably promoted the removal efficiency of As(III) from 50.7% to 89.3%. EGCG enhanced the reduction of Fe(III) to Fe(II) owing to the chelating, reducing, and electron-donating capabilities of ortho - or para -dihydroxybenzene groups in EGCG. The stable Fe(II) complex formed was continuously oxidized by PS, generating reactive oxygen species (ROS), such as hydroxyl radicals ( • OH), sulfate radicals (SO 4 –• ), and superoxide radical (O 2 •– ), which facilitated the oxidation of As(III). Density functional theory (DFT) calculations, combined with transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses, revealed that the resulting As(V) was primarily adsorbed onto the surfaces of colloid Fe 2 O 3 in the form of bidentate binuclear complex, as well as onto FeS 2 surfaces. This study presents an efficient approach to enhancing the FeS 2 /Fe(II)/PS process by incorporating natural polyphenols, offering a promising strategy for the removal of micropollutants in groundwater.