Synthesis of nickel ferrite precursors from low grade nickel matte

Fine nickel ferrite precursors NiFe2(C2O4)3·6H2O were obtained via co-precipitation method with low grade nickel matte as the raw material. Thermodynamic analysis of NiCl2-FeCl2-(NH4)2C2O4-H2O system for precipitation identified that the theoretical optimum co-precipitation pH value is 2, and C2O2+4 has strong complexation with Ni2+ and Fe2+ ions. Based on these theoretical considerations, the effects of parameters on the precipitation rates and precursors size were investigated systematically. The results show that the optimum co-precipitation conditions are pH=2, temperature 45 °C, 1.2 times theoretical amount of (NH4)2C2O4 dosage and 3% PEG400 addition. Under these conditions, the precipitation rates of Ni2+ and Fe2+ are both over 99.8%, with the precursors size of 1-2 um. Furthermore, X-ray diffraction (XRD) and thermogravimetry-differential thermal analysis (TG-DTA) demonstrate that the precursors are single-phase solid solution, wherein the nickel/iron atoms are replaced by the iron/nickel atoms reciprocally.