Study on the performance regulation mechanism of in-situ Bi doping on the degradation of tetracycline by Prussian blue analogue activated PMS catalytic system

Prussian blue analogues (PBAs) show potential in pollutant degradation, but are often limited by crystal structure regulation and insufficient exposure of active sites. In this study, Bi doping was used to synergistically optimize the crystal structure and electronic environment of CuFe-PBA and construct an efficient CuFe-Bi-3 catalyst for peroxymonosulfate (PMS) activated degradation of tetracycline (TC). The introduction of Bi induces crystal plane reconstruction, enhances the Cu²⁺/Cu⁺ and Fe³⁺/Fe²⁺ cycles, and increases the exposure of active sites. The TC degradation rate of CuFe-Bi-3 increased from 72.2 % to 92.1 % within 80 min, and the reaction rate constant increased from 0.01133 to 0.02631 min⁻¹. Mechanistic studies have shown that Bi regulation promotes the directional generation and utilization of ¹O₂, constructing a synergistic oxidation pathway dominated by non-free radicals. A comprehensive comparison of EPR signals for various reactive oxygen species showed that the ¹O₂ signal was the strongest, significantly higher than O₂^•-, •OH and SO₄^•-. The system has good stability in various water qualities and a wide pH range, and toxicity assessment also shows that it can effectively reduce the toxicity of degradation products. This study provides theoretical support and application reference for the structure-electronic regulation of PBAs catalysts and Bi doping to construct an environmentally friendly and efficient PMS activation system in a complex water environment.