Synthesis of citrate-modified CuFeS2 catalyst with significant effect on the photo-Fenton degradation efficiency of bisphenol a under visible light and near-neutral pH

In this study, for the first time, citric acid was employed as a chelating agent in CuFeS2 synthesis in order to accelerate the regeneration of Fe2+ during the photo-Fenton reaction, promoting a faster production of (OH)-O-center dot radicals. The novel CuFeS2 material showed remarkable catalytic efficiency for bisphenol A (BPA) degradation during the photo-Fenton process under visible light and near-natural pH, with a rate 10 times faster than that of CuFeS2 prepared without citrate. Furthermore, CuFeS2 promoted rapid generation of (OH)-O-center dot radicals and showed efficient H2O2 consumption, sustaining the catalytic efficiency and stability even after 4 consecutive cycles of use. CuFeS2 was also efficient for BPA degradation from a municipal wastewater treatment plant effluent. BPA by-products were identified and a mechanism for BPA degradation was proposed. After the photo-Fenton process, no Fe3+ species were identified on the catalyst surface by X-ray photoelectron spectroscopy (XPS), indicating that citric acid accelerated the conversion of Fe3+/Fe2+, thus increasing the generation of (OH)-O-center dot and the process efficiency.