Fe-doped g-C3N4 derived from biowaste material with Fe-N bonds for enhanced synergistic effect between photocatalysis and Fenton degradation activity in a broad pH range

Inspired by animal blood as a biowaste rich in biological enzymes with molecular Fe–N centers, Fe doped g-C3N4 (FCN) photocatalyst was successfully prepared by one-step thermal polymerization with pig blood and melamine to produce an efficient photocatalyst with Fe–N active sites for photo-Fenton degradation of tetracycline (TC) under visible light irradiation. The photocatalytic TC degradation results exhibited that FCN-1 sample possesses optimal photocatalytic degradation activity for TC (50 mg/L) in the presence of H2O2 system and a broad range over pH adaptation. The optimum photo-Fenton degradation activities of TC (50 mg/L) under visible-light irradiation for FCN-1/H2O2 system reach to 84.9% and 0.034 min−1 within 120 min under acidic conditions (pH = 3.1) and to 85% and 0.093 min−1 (first 20 min) in alkaline environment. Enhanced photocatalytic activity is mainly attributed to the positive roles of Fe-N bonds in FCN during the photo-Fenton process as follows: (i) improving the absorbance and separation efficiency in electron-hole pairs; (ii) accelerating the catalytic cycles between Fe2+/Fe3+ to produce more •OH in acidic condition; (iii) serving as active sites to boost the production of more photon-generated carriers in alkaline environment. Our work overcame the defect of low photocatalytic activity in photo-Fenton process under alkaline conditions, and provided a simple design idea for the low-cost synthesis of visible-light-driven photocatalyst with high efficiency applied to photo-Fenton reaction.