A novel Pac-Man structured Cu-Fe bimetallic catalyst for enhanced PAA activation: Unveiling the critical role of sulfur species in tetracycline hydrochloride degradation.

In this study, a novel porous carbon-supported bimetal oxide composite comprising copper ferrite and iron oxide (CuFeC), evoking the imagery of Pac-Man, was synthesized utilizing ion exchange resin as a template and was designed to activate peroxyacetic acid (PAA) for "devouring" tetracycline hydrochloride (TCH) in water. The characterization verified that CuFeC was made up of CuFe2O4 and Fe2O3 uniformly distributed on both the internal and external surfaces of the resin-derived carbon. Experimental results indicated that TCH removal reached 90.2 %-92.5 % within 30 min in the CuFeC/PAA system at the initial pH range of 3.0-9.0, where the reductive sulfur species on resin-derived carbon surface acted as electron donors to facilitate Cu(II)/Cu(I) and Fe(III)/Fe(II) cycles, thus enhancing the continued activation of PAA. During the degradation process, a variety of reactive oxygen species (ROS) were involved in the reaction, where R-O•, •OH and O2•- were the main contributors for the elimination of TCH. Furthermore, a potential degradation mechanism was proposed based on density functional theory calculations and product identification, the toxicity levels of the intermediate products were also evaluated. This study presented a novel methodology for the design of carbon-supported transition metal oxide catalysts in the realm of PAA-AOP for the comprehensive removal of contaminants.