Enhanced froth flotation recovery of nickel sulphides from concentrator tailings

This study explored the floatability and concentration potential of flotation tailings with a P80 size of 80 μm using the Box–Behnken experimental design method for optimising surface properties through multivariate analysis. The mean nickel content in the tailings was 0.22%, with pentlandite (Fe,Ni)9S8 contributing to 38.7% of this composition. Three key flotation parameters—air flow rate, agitation speed, and pulp concentration—were varied across three levels, while the pulp pH was maintained at 9.5. The air flow rate ranged from 4 to 7 L/min, agitation speed from 1500 to 2000 rpm, and pulp concentration from 30% solids to 60% solids. The average Ni recovery was 76%, whereas the average Ni grade and mass pull were 1.4% and 15.6%, respectively. A comprehensive analysis of the flotation response dataset revealed that 5.5 L/min, 50% solids, and 2000 rpm were the optimal levels for maximum Ni recovery. All three flotation variables significantly influenced the nickel recoveries at 95% CI: air flow rate (p = 0.00), agitation speed (p = 0.00), and pulp concentration (p = 0.04). The interaction effect of the air flow rate and the pulp concentration on the flotation performance was statistically significant with a p-value of 0.02. Future work could focus on other flotation parameters, such as reagent addition rates and alternative flotation reagents to optimise Ni recovery, grade, and mass pull.