Enhanced persulfate-mediated photocatalytic oxidation of bisphenol A using bioelectricity and a g-C3N4/Fe2O3 heterojunction

Photocatalysis and sulfate radical based advanced oxidation processes have gained considerable popularity in the field of contaminant degradation. However, there are few reports focusing on the combination of these two promising technologies, especially the coupling of a visible light responsive catalyst with an electro-assisted persulfate activation system. Herein, a traditional g-C3N4/Fe2O3 (CNFe) heterojunction was prepared by a facile one-pot calcination and it could efficiently activate peroxydisulfate (PDS) for bisphenol A (BPA) decomposition with visible light and low-voltage bioelectricity supplied by a microbial fuel cell (MFC). The CNFe catalyst demonstrated good stability and could be reused at least five runs with negligible iron leaching. Sulfate and hydroxyl radicals and singlet oxygen were responsible for the BPA degradation. A mechanism for BPA destruction in the studied system is proposed based on the results of electron paramagnetic resonance (EPR), trapping experiments, X-ray photoelectron spectroscopy (XPS) and the band edge potential of g-C3N4 and Fe2O3. The effects of reaction conditions on the BPA oxidation were explored and 92.2% of BPA was removed after 60 min reaction using 10 mM of PDS, 0.5 g L-1 of CNFe, 100 mA m(-2) of current density and natural pH. The total organic carbon (TOC) removal was only 70.0%, but when the time was extended to 2 h, it rose to 91.0%, indicating high mineralization of the proposed system.