High-efficiency degradation of bisphenol A by heterogeneous Mn–Fe layered double oxides through peroxymonosulfate activation: Performance and synergetic mechanism

Mn–Fe bimetal catalyst possesses excellent activation properties, and the enhancement of Mn/Fe redox cycle for electron transfer is related to the crystalline structure and surface functional groups. Therefore, material structure optimization is an effective strategy to improve its activation performance in advanced oxidation. In this study, Mn–Fe LDO catalyst with strong Mn/Fe synergistic effect was synthesized, and used for bisphenol A degradation. Under the condition of 0.4 g/L Mn-Fe LDO, 1.5 mM PMS and pH 7.0, Mn-Fe LDO/PMS system exhibited excellent degradation performance that 100% of BPA (20 mg/L) and 72.0% of COD could effective be degraded within 50 min. Five-run recycle and metal ions leaching experiments proved the excellent reusability and stability of Mn-Fe LDO. To deepen the understanding of catalytic mechanism, the synergistic effect and electron transfer between Mn and Fe were confirmed via XPS and CVs results. Moreover, the indispensable role of surface hydroxyl groups were clarified via phosphate masking experiment, ATR-FTIR and LSV analysis. The presence of Mn and Fe active sites and hydroxyl groups on Mn-Fe LDO surface could efficiently promote electron transfer, thus accelerating the redox cycles of Mn3+/Mn2+ and Fe3+/Fe2+. The generation of SO4·− and HO· as the main radicals was occurred on the surface of Mn-Fe LDO, and SO4·− played a major role during the reaction. On the basis of these experimental conclusions, the mechanisms of Mn–Fe LDO/PMS system for high-efficiency BPA degradation were proposed. GC-MS analysis was performed to detect the BPA degradation intermediates and propose the possible degradation pathways.