Enhanced degradation of organic water pollutants by photocatalytic in-situ activation of sulfate based on Z-scheme g-C3N4/BiPO4

In recent years, the excellent performance of sulfate radical (SO 4 · − ) in advanced oxidation process has attracted more and more attention. However, it requires the consumption of expensive persulphate (PMS/PDS), and the resulting sulfate ion (SO 4 2− ) requires subsequent processing procedures, which limits its practical application value. In this work, a Z-scheme heterojunction g-C 3 N 4 /BiPO 4 (CNB x ) photocatalyst was constructed to in-situ activate the residual SO 4 2− , H 2 O and dissolved O 2 in organic wastewater simultaneously and produce SO 4 · − , ·OH and O 2 · − efficiently, so as to realize enhanced organic pollutant treatment by using clean and renewable solar energy resources. Under the condition of 10 mM SO 4 2− addition and 100 mW·cm −1 illumination, the degradation rate of BPA ( C 0  = 20 mg·L −1 ) by optimized CNB 150 catalyst was 0.30 min −1 , which was 50% higher than that without SO 4 2− (0.20 min −1 ). Detailed characterizations shown that a direct Z-scheme heterojunction was formed between g-C 3 N 4 and BiPO 4 , which could be simultaneously stimulated by light, and then effective charge separation and migration could be achieved through the internal electric field caused by the Fermi-level difference between the g-C 3 N 4 (-0.12 eV) and BiPO 4 (0.01 eV). In general, this study makes full use of renewable solar energy and provides a feasible path for promoting the simultaneous in-situ utilization of small molecules (SO 4 2− , H 2 O and O 2 ) that originally exist in water, which makes organic wastewater treatment more economic, eco-friendly and sustainable.