New perceptions into the detrimental influences of serpentine on Cu-Ni sulfide flotation through rheology studies and improved the separation by applying garnet

Abstract

The flotation separation between sulfides and fine serpentine has always been a difficult problem due to their hetero-coagulation. To acquire a better understanding on the adverse effect of fine serpentine on Cu-Ni sulfide flotation, rheology measurements and flotation tests on Cu-Ni sulfide/serpentine system were explored under different conditions in this study. Rheology results revealed that in the aqueous solution at pH 9.5–10, serpentine particles could partially aggregate in pulp, whereas Cu-Ni sulfide particles did not aggregate. In the mixed Cu-Ni sulfide/serpentine system, the higher the total solid concentration was, the greater the influence of serpentine proportion on pulp rheology was. When pulp solid concentration was higher than 10 %, pulp viscosity increased obviously as serpentine proportion increased no matter in the absence or presence of potassium butyl xanthate (PBX). However, with the increase of serpentine proportion, pulp yield stress gradually increased in aqueous solution, indicating the hetero-coagulation between sulfide and serpentine occurred, while in the presence of PBX, the pulp yield stress increased first and then decreased. The deterioration of the flotation performance of Cu-Ni sulfide suggested that the hetero-coagulation was not the only factor affecting the flotation of Cu-Ni sulfide containing serpentine, high pulp viscosity could also worsen that. However, with the addition of coarse garnet particles (-104 + 44 μm), the pulp yield stress decreased remarkably, illustrating that the hetero-coagulation between sulfide and serpentine was limited. Furthermore, pulp viscosity also decreased obviously, and the synthetic actions improved Cu-Ni sulfide flotation. Micro-flotation and batch flotation results verified that the Ni recovery in concentrate increased significantly with a remarkable decrease in SiO2 content after adding garnet (-104 + 44 μm). This study offered some new insights into the adverse effect of serpentine on sulfide flotation, and the employment of stir medium such as garnet, might be a potential way to improve the flotation separation of sulfides from serpentine.