Preparation of Fe3O4@GO@MIL-101 nanocomposites and efficient degradation of oxytetracycline hydrochloride by promoting charge separation during the photo-Fenton process

The combination of photocatalysis and Fenton oxidation technology is an efficient strategy to improve the ef-ficiency of oxytetracycline hydrochloride (OTC-HCl) degradation. Herein, a Fe3O4@GO@MIL-101 composite catalyst bridged with graphene oxide (GO) was obtained by a two-stage hydrothermal method. The introduced graphene oxide layer could inhibit the recombination of electron hole (e-- h+) pairs by attracting photo -generated electrons from MIL-101 and transferring them to Fe3O4, observably enhancing the photocatalytic performance of the composite Fe3O4/MOFs. Under the optimal conditions (initial pH, 10 mmol H2O2, 0.01 g/L catalyst), the Fe3O4@GO@MIL-101 + H2O2+Vis system could achieve a degradation effect of 97.26 % on 70 mg/ L OTC-HCl within 50 min Fe3O4@GO@MIL-101 nanocomposites exhibited good recyclability, were easy to recover after multiple uses, and maintained excellent removal efficiency for pollutants. A series of data demonstrated that in Fe3O4@GO@MIL-101 + H2O2+Vis system, the primary active substances involved in OTC-HCl degradation were holes and superoxide radicals, while the contributions of hydroxyl radicals and photo generated electrons were relatively weak. Finally, based on various characterization results and catalyst activity performance, a feasible mechanism for the removal of OTC-HCl by Fenton-like system was proposed.