Fabrication of 3D multi-layered ZnCo-LDH as a heterogeneous photoactivator of peroxymonosulfate for efficient degradation of rhodamine B

Peroxymonosulfate (PMS)-based advanced oxidation processes have been widely concerned because of their efficient treatment and wide applicability for the removal of various organic pollutants. In this study, ZnCo layered double hydroxide (ZnCo-LDH) were prepared by the hydrothermal method, analyzed by several characterization methods, and tested as a heterogeneous photoactivator to activate PMS for the removal of refractory organic dyes. The experimental results showed that 3D multi-layered ZnCo-LDH (1:1) catalyst can activate PMS to achieve the main degradation of 10 mg L-1 rhodamine B (RhB) under dark within 40 min. Moreover, the RhB can be completely degraded within 30 min by supplying the additional visible light under the same conditions. It can be seen that all degraded reaction processes were corresponded with the pseudo-first-order kinetic model, and the highest rate of RhB removal is 0.1303 min(-1) in visible light. The effect of various conditions including the reaction system, inorganic anions, and initial pH on the RhB degradation was analyzed in detail. The ZnCo-LDH (1:1) catalyst can still keep high catalytic activity to PMS and achieved more than 95% degradation efficiency even after continual four recycles. In addition, the reaction mechanism indicated that hydroxyl radical ((OH)-O-center dot) and sulfate radical (SO4 center dot-) can effectively oxidize RhB by the single activation of ZnCo-LDH catalyst, and this reaction process can also be enhanced under visible light irradiation. Briefly, the heterogeneous PMS-AOPs synergistic techniques could be a promising work for the integrated control of environmental pollution.

Automated summary

This study demonstrates that ZnCo layered double hydroxide (ZnCo-LDH) catalyst can efficiently remove refractory organic dyes by activating peroxymonosulfate (PMS). Under visible light, RhB can be completely degraded, and the catalyst maintains high activity even after four cycles.