A novel CoNi7O8/MnO2 nanocomposite supported on Ni foam as a peroxymonosulfate activator for the highly efficient singlet oxygen mediated removal of methylene blue

Abstract

Developing a highly efficient catalyst that can be easily separated for peroxymonosulfate (PMS) activation during wastewater remediation is still a great challenge. Herein, an immobilized CoNi₇O₈/MnO₂ nanocomposite on Ni foam (NF) was successfully synthesized via a multi-step route. XRD, SEM, TEM, and XPS characterization demonstrated that CoNi₇O₈ nanoparticles were deposited on the MnO₂ nanosheet surface. With respect to CoNi₇O₈/NF and MnO₂/NF alone, as-synthesized CoNi₇O₈/MnO₂/NF exhibited superb catalytic activity toward PMS activation, allowing 100% methylene blue (MB) removal within 15 min under near-neutral conditions, owing to the synergistic interactions between the components. Influential factors, including pollutant concentration, PMS dosage, and initial pH, were systematically investigated. Electrochemical measurements revealed interfacial electron transfer between the catalyst and PMS. Radical quenching experiments and electron spin resonance (EPR) studies corroborated the major contribution of singlet oxygen (¹O₂) to MB elimination. The reaction mechanism was also elucidated. Furthermore, CoNi₇O₈/MnO₂/NF presented decent cycling stability. This work offers important insight into constructing a highly active and durable catalyst for PMS-based refractory organic wastewater purification.