Peroxymonosulfate activation by CuMn-LDH for the degradation of bisphenol A: Effect, mechanism, and pathway

The remediation of water contaminated with bisphenol A (BPA) has gained significant attention. In this study, a hydrothermal composite activator of Cu₃Mn-LDH containing coexisting phases of cupric nitrate (Cu(NO₃)₂) and manganous nitrate (Mn(NO₃)₂) was synthesized. Advanced oxidation processes were employed as an effective approach for BPA degradation, utilizing Cu₃Mn-LDH as the catalyst to activate peroxymonosulfate (PMS). The synthesis of the Cu₃Mn-LDH material was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). According to the characterization data and screening experiments, Cu₃Mn-LDH was selected as the best experimental material. Cu₃Mn-LDH exhibits remarkable catalytic ability with PMS, demonstrating good degradation efficiency of BPA under neutral and alkaline conditions. With a PMS dosage of 0.25 g·L^-1 and Cu₃Mn-LDH dosage of 0.10 g·L^-1, 10 mg·L^-1 BPA (approximately 17.5 μM) can be completely degraded within 40 min, of which the TOC removal reached 95%. The reactive oxygen species present in the reaction system were analyzed by quenching experiments and EPR. Results showed that sulfate free radicals (SO₄^•-), hydroxyl free radicals (•OH), superoxide free radicals (•O₂^-), and nonfree radical mono-oxygen were generated, while mono-oxygen played a key role in degrading BPA. Cu₃Mn-LDH exhibits excellent reproducibility, as it can still completely degrade BPA even after four consecutive cycles. The degradation intermediates of BPA were detected by GCMS, and the possible degradation pathways were reasonably predicted. This experiment proposes a nonradical degradation mechanism for BPA and analyzes the degradation pathways. It provides a new perspective for the treatment of organic pollutants in water.