Selective flotation of pyrite from serpentine using phytic acid as the depressant

The flotation of sulfide minerals has been always a problem due to the slime coating of serpentine. In this study, phytic acid (PA) was introduced as a selective depressant to eliminate the adverse effect of serpentine on the flotation of pyrite. Micro-flotation tests showed that the flotation performance of pyrite depressed by serpentine could be regained with the addition of PA. In addition to micro-flotation tests, the action mechanism of PA was systemically investigated based on a series of analyses including zeta potential tests, adsorption measurements, turbidity studies and X-ray photoelectron spectroscopy (XPS) analyses. It was found that PA could chemically react with the active Mg sites and then selectively adsorb onto serpentine surface. In this case, the surface potential of serpentine was shifted from positive to negative at pH 9, thus resulting in the transformation of electrostatic interaction between pyrite and serpentine from electrostatic attraction to electrostatic repulsion. Hence, the slime coating of serpentine on pyrite surface was removed and the adsorption amount of potassium butyl xanthate (PBX) onto pyrite surface was regained. In this way, the adverse effect of serpentine on the flotation of pyrite was eliminated.