Synthesis, physical and electrochemical properties of CoMn2O4: application to photocatalytic Ni2+ reduction

Nickel is a hazardous metal with a harmful effect on the health and environment. In this work, the photocatalytic reduction of Ni2+ was examined onto the hetero-system CoMn2O4/TiO2 under visible light irradiation. The spinel CoMn2O4 is prepared by co-precipitation and characterized in detail to correlate its structural, textural, morphological, compositional, optical and photoelectrochemical features. The effects of pH, catalyst dose and Ni2+ concentration were optimized. The Ni2+ reduction increased with decreasing both the catalyst dose and pH. The highest performance was obtained at pH 7.4, a catalyst dose of 1 g/L and Ni2+ concentration of 10 mg L−1 with a removal abatement of 88% after 180 min irradiation. The data were suitably fitted by the pseudo-first-order kinetic reaction with an apparent constant of 0.027 min−1. Besides, the durability and the stability of the hetero-system CoMn2O4/TiO2 were evaluated by four consecutive catalytic cycles.