Efficient Fe(III) reduction and persulfate activation induced by ligand-to-metal charge transfer under visible light enhances degradation of organics

Abstract

Efficient transformation of Fe(III) to Fe(II) enhances the efficiency of persulfate-based Fenton-like process (e.g., Fe(II)-PS system). Here, we developed a novel heterogeneous Fenton-like system driven by visible light (organic-Fe(III)-PS-TiO2-Vis) for effective reduction of Fe(III), activation of PS and degradation of organic pollutants without the need for external reducing agents or modifications in TiO2. The visible light-induced ligand-to-metal (organic-to-TiO2) charge transfer (LMCT) remarkably boosting Fe(III) reduction to increase reactive oxygen species (ROS) via PS activation, and further enhanced the self-degradation and mineralization of various organics, including phenolics (bisphenol A and phenol), antibiotics (ibuprofen and tetracycline), and dyes (methylene bule and rhodamine B). Compared with traditional Fe(II)-PS and Fe(II)–H2O2 systems, the organic-Fe(III)-PS-TiO2-Vis process requires a lower dosage of iron salt. The effective pH range has been broadened to neutral conditions due to effective prevention of Fe(III) precipitation and rapid circulation of Fe(III)/Fe(II). The comprehensive mechanistic study indicated that a synergistic effect was generated via Fe(III) reduction, PS activation, ROS generation and organic decomposition, resulting in sustainable and excellent catalytic performance of this novel Fenton-like process. Further, the results of cycling experiments and tests involving real industrial wastewater highlight the enormous potential of the proposed LMCT-mediated heterogeneous Fenton-like process in environmental remediation.