The Critical Role of Pulp Density on Flotation Separation of Nickel-Copper Sulfide from Fine Serpentine

A nickel-copper sulfide system usually coexists with serpentine in deposits. Low nickel-copper recovery and high content of serpentine in concentration adversely affects subsequent metallurgical processes. In this study, test data showed different rheological results at various densities. When the solid ratio of sulfide to serpentine was 1:1, lower pulp density (20 wt %) contributed to better rheological and flotation outcomes. Generally, the addition of SHMP (sodium hexametaphosphate) is beneficial to reduce the amount of serpentine mineral into the concentration as a depressant through changing the surface electrical behavior of serpentine. However, the different dosages of SHMP have little impact on pulp rheology at 40 wt % of slurry, but there is a huge difference on flow property at 20 wt % pulp. The results revealed that rheology, which is caused by pulp density, played a key role in flotation performance. The decline in density (from 40 wt % to 20 wt %) increased the nickel and copper recoveries from 70.7% to 79.5% and 82% to 85.4% respectively in the artificial mixture (1:1). The content of serpentine in concentration decreased by around 20% by using SHMP at the same time.