Tune surface physicochemical property of fluorite particles by regulating the exposure degree of crystal surfaces

Abstract

Grinding for mineral liberation is a prerequisite for a successful flotation separation and different grinding media produce mineral particles with different morphologies and surface properties. In this paper, a systematic investigation was carried out on surface physicochemical properties of fluorite particles produced by ball and rod mills through such methods as single mineral flotation experiment, wettability measurement, X-ray diffraction (XRD) test and scanning electron microscopy (SEM) observations. XRD and SEM observations indicate that the predominant surfaces exposed for both mill particles follow the order of {1 1 1} > {1 1 0} > {3 1 0} > {1 0 0} surfaces. The difference lies in that the rod mill particles possess a higher exposure of more reactive {1 1 0} and {3 1 0} surfaces of higher calcium-atom reactivity, which show a stronger interaction with the collector and hence a higher monolayer coverage degree. This difference also leads to a higher elongation and lower roundness values of rod mill particles that are beneficial to the particle-bubble attachment by shortening the induction time. The results of wettability and flotation show that when treated with the collector solution, the particles produced by rod mill possess a lower critical surface tension and greater hydrophobicity, hence exhibiting a higher flotation recovery. This study signifies the importance of the exposure of crystal surfaces in determining the shape factors and reactivity of mineral particles, which will help to guide the optimization of flotation separation and particle surface modification.