Enhanced removal of ibuprofen by heterogeneous photo-Fenton-like process over sludge-based Fe3O4-MnO2 catalysts

Heterogeneous photo-Fenton-like catalysts with low cost, little hazard, high effectiveness and facile separation from aqueous solution were highly desirable. In this study, sludge-based catalysts combining nano Fe3O4-MnO2 and sludge activated carbon were successfully synthesized by high-temperature calcination method and then characterized. These synthetic materials were applied to remove ibuprofen in the heterogeneous photo-Fenton process. The preparation conditions of sludge-based catalysts optimized by orthogonal experiments were 2.0 M of ZnCl2, a temperature of 500 °C, a pyrolysis time of 60 min, and a sludge ratio: Fe3O4-MnO2 of 25:2. In batch experiments, the optimal experimental conditions were determined as catalyst dosage of 0.4 g·L−1, hydrogen peroxide concentration of 3.0 mL·L−1, pH value of 3.3, and contact time of 2.5 h. The degradation rate sludge/Fe3O4-MnO2 catalyst to ibuprofen is up to 95%. The removal process of ibuprofen fitted the pseudo-second-order kinetic model, and the photocatalytic degradation process was the main factor controlling the reaction rate. The catalytic mechanism was proposed according to the Fourier transform infrared analysis and mass spectrometry product analysis; it was mainly attributed to the interaction between hydroxyl groups and benzene rings.