A comprehensive study on the treatment of various organic pollutants by NiCoFe layered double oxide: Material synthesis and characterization, decomposition mechanism exploration, and real water applications

In this report, we successfully synthesized NiCoFe layered double oxide (NiCoFe-LDO) by heating a hydrothermally prepared NiCoFe layered double hydroxide in the air at 400–700 °C. The morphology, crystal structure, surface area, elemental composition and environment, functional groups, thermal stability, and magnetic properties of the materials were determined by SEM, XRD, BET, XPS, FTIR, TGA-DTG, EPR, and VSM analyses. The material was then used to activate potassium peroxymonosulfate (PMS) for degrading Rhodamine B (RhB) and other dyes in different conditions of water, surface water, and wastewater. The results showed that NiCoFe-LDO annealed at 500 °C can remove 97.86% RhB (20 mg/L) in 14 min at pH 7. Moreover, the presence of anions (i.e., HPO4-, HCO3–, CO32–, NO3–, Cl-, and SO42-) in the solution affected the RhB removal efficiency. In various dyes removal tests, the removal efficiency of the dyes was in the order of RhB > OG > DB71 ≈ MO ≈ TTZ ≈ JGB ≈ MB. In the radical scavenging tests, the occurrence and role of radicals in RhB decomposition were in the order of O2●- > 1O2 > SO4●- > HO●, thus the decomposition of RhB is based on both radical and non-radical reactions. Moreover, the intermediates formed during the reaction were detected. Accordingly, the mechanism of RhB decomposition by the NiCoFe-LDO under PMS activation was proposed. Finally, the durability of the materials and its high dyes and organics removal efficiency in both surface water and actual wastewater suggests a great potential for practical applications of NiCoFe-LDO/PMS in wastewater treatment, especially for the recalcitrant components.