Construction of Bi2WO6/g-C3N4 Z-Scheme Heterojunction and Its Enhanced Photocatalytic Degradation of Tetracycline with Persulfate under Solar Light

Abstract

Z-scheme heterojunction Bi2WO6/g-C3N4 was obtained by a novel hydrothermal process; its photocatalysis–persulfate (PDS) activation for tetracycline (TC) removal was explored under solar light (SL). The structure and photoelectrochemistry behavior of fabricated samples were well characterized by FT-IR, XRD, XPS, SEM-EDS, UV-vis DRS, Mott-Schottky, PL, photocurrent response, EIS and BET. The critical experimental factors in TC decomposition were investigated, including the Bi2WO6 doping ratio, catalyst dosage, TC concentration, PDS dose, pH, co-existing ion and humic acid (HA). The optimum test conditions were as follows: 0.4 g/L Bi2WO6/g-C3N4 (BC-3), 20 mg/L TC, 20 mg/L PDS and pH = 6.49, and the maximum removal efficiency of TC was 98.0% in 60 min. The decomposition rate in BC-3/SL/PDS system (0.0446 min−1) was 3.05 times higher than that of the g-C3N4/SL/PDS system (0.0146 min−1), which might be caused by the high-efficiency electron transfer inside the Z-scheme Bi2WO6/g-C3N4 heterojunction. Furthermore, the photogenerated hole (h+), superoxide (O2•−), sulfate radical (SO4•−) and singlet oxygen (1O2) were confirmed as the key oxidation factors in the BC-3/SL/PDS system for TC degradation by a free radical quenching experiment. Particularly, BC-3 possessed a wide application potential in actual antibiotic wastewater treatment for its superior catalytic performance that emerged in the experiment of co-existing components.