Effect of CaO on Fluorine in Spent Cathode Carbon during Nickel Laterite Reduction

Abstract

Large amounts of solid waste-spent cathode carbon (SCC) was produced in aluminum electrolysis process. At present, landfill and storage methods are widely used, which will not only cause great harm to the environment, but also cause a lot of waste of resources. Nickel and iron were recovered from laterite nickel ore by reduction roasting-magnetic separation using SCC as reducing agent. The fluorine in SCC was fixed in roasted ore by adding CaO. The feasibility of the method was verified by thermodynamic analysis and experiments, and the optimum conditions for CaO addition were determined. The recovery of nickel and iron reached 91.23% and 89.63% respectively when the addition of SCC was 14 wt. % and CaO was 8 wt. %. Adding 8 wt.% CaO under the condition of SCC as reducing agent can change the viscosity of roasted ore and promote the aggregation of ferronickel particles. The concentration of soluble F- in roasted ore was reduced and fixed in roasted ore in the form of insoluble calcium fluoride. Under the condition of adding 8 wt.% CaO, the fluorine fixation rate was 95.99%, and the concentration of F- in roasted ore was only 31 mg·L−1.