Decomplexation removal of Ni(II)-citrate complexes through heterogeneous Fenton-like process using novel CuO-CeO2-CoOx composite nanocatalyst

A novel CuO-CeO 2 -CoO x nanocatalyst was prepared for heterogeneous Fenton-like reaction to break the Ni 2+ -chelate into free Ni 2+ in electroless nickel plating wastewater, followed by separation of Ni 2+ in an insoluble form. The composite nanocatalysts prepared by co-precipitation method were characterized by XRD, TEM, and XPS, et al. Its catalytic activity as Fenton-like reagent was evaluated by the removal efficiency of Ni(II)-citrate after decomplexation and postprecipitation treatment. Subsequently, the effects of operating parameters on the decomplexation efficiency of the nanocatalysts were investigated including calcination temperature of catalysts, H 2 O 2 concentration, catalyst dosage, initial pH and reaction temperature. Under optimized condition, the Ni(II)-citrate complexes ( C 0  = 1.0 mM) achieved the complete decomplexation (>99.9%) within 60-min reaction using 0.3 g/L of CuO-CeO 2 -CoO x calcined at 450 °C and 75 mM of H 2 O 2 at pH 3.0 under 50 °C of reaction. Then, Ni 2+ after decomplexation could be completely removed by the subsequent precipitation at pH 11.0. In addition, the life test of CuO-CeO 2 -CoO x catalyst indicated that, after recycled 10 times, its activity for decomplexation of Ni(II)-citrate decreased no more than 8%. As a result, this new heterogeneous Fenton-like process is promising for decomplexation and purification of electroless nickel plating wastewater as a sludge reduction technology.