Synthesis and characterization of BiFeO₃/LaFeO₃/graphene composites as persulfate activator for removal of 4-nitrophenol

4-Nitrophenol (4-NP) is used to manufacture drugs, fungicides, insecticides, and dyes. Discharge of industrial effluent containing 4-NP into the receiving water could result harmful effects on the environment and human beings. Therefore, in this study advanced oxidation process (AOP) using BiFeO₃/LaFeO₃/graphene (BFO/LFO/G) composites as catalysts is applied to evaluate the degradation of 4-NP in aqueous solution. LFO/BFO/G was synthesized and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, UV–Vis-diffuse reflectance spectroscopy (DRS), Photoluminesence (PL), Brunauer-Emmett-Teller (BET) surface area analysis, vibrating sample magnetometry (VSM), cyclic voltammetry, thermogravimetric (TGA) analysis and was further used to degrade 4-NP assists with peroxydisulfate (PS) and hydrogen peroxide (H₂O₂) under UV and visible light irradiation. Each experimental parameter was evaluated, including the initial NP concentration, pH, PS concentrations, and catalyst dosage. Compared to pure BiFeO₃, LaFeO₃ nanoparticles, and a BiFeO₃/LaFeO₃ composite, the BiFeO₃/LaFeO₃/graphene composites significantly increased the degradation of 4-NP. Optimal degradation was achieved with a BiFeO₃/LaFeO₃/graphene composite containing 5 wt% graphene and could degrade ∼90.2 % of 4-NP within 2 h, with assisted of PS. The degradation of 4-NP in the presence of PS was more efficient under irradiation with visible light than UV light. The dominant mechanism of the degradation process was discussed. Additionally, the LC-MS results proposed the degradation path of 4-NP. Based on the results, the synthesized composites showed their ability to degrade 4-NP in aqueous solutions.