The effect of bulk iron concentration and heterogeneities on the copper activation of sphalerite

Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study the Cu activation of the (1 1 0) surface of sphalerites with Fe content varying from 0 to 14.79 wt%. Time resolved AFM images show the development of surface oxidation products at high-energy step edges. These small protrusions evolve into larger conglomerates and finally full surface coverage with time. Surface morphology changes show an increase in the number of cleavage steps and the size of precipitates as a function of Fe concentration. Both of these factors contribute to the increased rate of Cu activation of high Fe sphalerite as compared to low Fe sphalerite. XPS analysis of the sphalerites Cu activated for 1 h at pH 5, indicates an increased Cu concentration and the formation of disulphide and polysulphide that correlates with an increase in bulk Fe content.