Novel step-scheme red mud based Ag3PO4 heterojunction photocatalyst with enhanced photocatalytic performance and stability in photo-Fenton reaction

[Display omitted] •Heterostructure composite was constructed via in-situ growth of Ag3PO4 on red mud.•The composite (APRM) is a new cost-efficiency catalyst for photo-Fenton reaction.•APRM holds excellent catalytic activity and outstanding stability in use.•S-scheme heterojunction can account for the charge transfer pathway in APRM.•The toxicity of TC-HCl could be weakened via photo-Fenton catalyzed by APRM. In our work, using industrial waste red mud (RM) as a host material to grow silver phosphate (Ag3PO4), a low-cost and new heterogeneous Ag3PO4/RM (APRM) composite was successfully prepared through a facile in-situ deposition method. The characterization results demonstrated Ag3PO4 nanoparticles uniformly deposited on RM to form P-O-Fe bonds, and a semiconductor heterostructure was constructed between the two nanocrystalline components of Ag3PO4 and Fe2O3. The optimal composite of APRM-110 exhibited a remarkable photocatalytic activity for the degradation of tetracycline hydrochloride (TC-HCl) in photo-Fenton reaction. The enhanced photocatalytic performance and stability could be attributed to the S-scheme charge transfer in APRM-110, which accelerated the photo-generated carrier separation and then effectively restrained the photocorrosion of APRM-110. The APRM-110 composite held good reusability, stability and excellent settleability. The main intermediates were identified and the degradation pathway of TC-HCl in photo-Fenton reaction catalyzed by APRM-110 was proposed. The aquatic toxicity of TC-HCl solution could be effectively weakened by the photo-Fenton catalyzed by APRM-110. This work has designed a cost-efficiency and stable RM-based Ag3PO4 composite, and as a highly effective catalyst for TC-HCl degradation in photo-Fenton reaction.