Degradation of Rhodamine B by MnFe-LDH/PMS/O3 Three-Phase Catalytic System: Performance, Mechanism and Ecotoxicity Studies

This study developed a novel MnFe-LDH/PMS/O3 three-phase catalytic system to degrade the organic dye RhB, which was used to address the drawbacks of persulfate oxidation and ozonation techniques. The structure, ionic and elemental composition, specific surface area, and magnetic properties of the LDHs were investigated using a variety of physicochemical characterization tools. The results showed that MnFe-LDH had a large specific surface area, a rich crystalline phase composition, and a functional group structure. The RhB degradation rate of MnFe-LDH/PMS/O3 was 0.34 min−1, which was much higher than that of other comparative systems. RhB could be completely degraded in 10 min after optimization and had a significant effect on TOC removal. The system was found to be effective over a wide pH range. Common anions were largely unaffected and humic acid acted as an inhibitor. At the same time, the system had generally effective degradation performance for different dyes. Combined with quenching experiments and EPR, it was found that SO4•−, •OH, O2•−, and 1O2 all participated in the reaction, and •OH contributed more. The degradation pathway of RhB was derived by LC-MS, and the T.E.S.T. evaluation found that the toxicity of the intermediate product was significantly reduced. Finally, the stability and availability of LDHs were verified using cycling experiments and metal ion leaching. This work provides a theoretical basis and data support for the synergistic catalysis of PMS/O3 and the deep treatment of dye wastewater.