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

Abstract

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.