Enhanced mineralization of bisphenol A by eco-friendly BiFeO3-MnO2 composite: Performance, mechanism and toxicity assessment

An eco-friendly BiFeO3-MnO2 composite with dual functionalities of adsorption and catalysis was successfully constructed by using a simple one-step hydrothermal method for the removal of bisphenol A (BPA) pollution from water. Several characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), were applied to verify the combination of BiFeO3 and MnO2. BiFeO3-MnO2 (BFO-MO) exhibited excellent adsorption and catalytic activity compared with those of pure BiFeO3. The adsorption process followed a pseudo-second-order kinetic model and matched the Langmuir isotherm model. Effects of the catalyst and peroxymonosulfate (PMS) concentrations, pH and real water matrix were also analyzed, and BFO-MO displayed perfect adsorption and degradation performance under different conditions. Meanwhile, mineralization performance was tested, and the total organic carbon removal rate was nearly 85%. Moreover, BFO-MO exhibited good stability and reusability after five cycles. Based on radical quenching experiments, SO4 center dot- and OH center dot were the primary reactive species responsible for BPA oxidation, and the possible reaction mechanism of BFO-MO/PMS was proposed. Finally, the degradation intermediates were identified, and the toxicity of intermediates was assessed. The novel BFO-MO composite is a promising catalyst for synchronous adsorption and degradation to purify wastewater.