Enhanced degradation of tetracycline over FeS-based Fenton-like process: Autocatalytic decomposition of H2O2 and reduction of Fe(III)

Abstract

This study constructed a FeS-based Fenton-like process to explore the degradation of TTC in the presence of copper ions. The acidic condition of pH 3 was more favorable to the H₂O₂ decomposition and TTC degradation, and it was slightly enhanced by Cu(II). The production of •OH from H₂O₂ was revealed through radical scavenging and benzoic acid probe experiments, and the ratio of H₂O₂ decomposition to •OH production was about 1-1.5, which is comparatively consistent with the theoretical ratio. FeS-based Fenton process was proved to be a homogenous system, the slow release of Fe(II) source and the autocatalytic cycle of Fe(III) to Fe(II) resulting from the reductive species of TTC and dissolved S(-II) improved the production of •OH and the degradation of TTC, which was proved by comparing TTC degradation, TOC removal, H₂O₂ decomposition and Fe(II) concentration with different iron sources (FeS, Fe(II) and Fe(III)) and external addition of dissolved S(-II). The possible degradation pathways of TTC were subsequently inferred according to the detected products by LC-MS. Understanding these autocatalytic processes is essential to reveal the transformation of redox-active substances in environments and may have potential significance in applying FeS-based Fenton-like process for the treatment of wastewater containing reductive organic matters.

Keywords: Autocatalysis; Fe(III)/Fe(II) cycle; FeS; H(2)O(2) decomposition; Tetracycline.