ZIF-67-derived Co3S4-modified cathode with high CoII content enhances the removal of chloroquine phosphate by the electro-Fenton system

Chloroquine phosphate (CQP), commonly used in treating autoimmune diseases and malaria, has been detected in various water bodies and poses potential hazards to the ecological environment. In this study, ZIF-67-derived Co3S4-modified graphite felt cathode (Co3S4/GF) was used to construct a heterogeneous electro-Fenton system for efficient CQP removal. The introduction of sulfur greatly improved the electron transfer rate and reduced the charge transfer resistance, garnering the Co3S4/GF composite cathode with excellent electrochemical activity. The Co3S4/GF electro-Fenton system completely removed CQP within 60 min at near-neutral initial pH and exhibited 19.3 % higher CQP removal efficiency than the ZIF-67/GF system. This enhanced performance was mainly attributed to the introduction of sulfur, which increased the proportion of low-valent metal in the material and promoted the CoIII and CoII cycle. The hydroxyl radical was identified as the main radical involved in CQP degradation. The intermediates of CQP degradation were detected, and four possible degradation pathways of CQP were obtained. The ecotoxicity of CQP and its intermediates decreased during the degradation process. This work proposes novel ideas for the rapid development of metal-organic framework-derived Co/S-based materials for their application in the field of environmental catalysis.