New insights into the effects of particle size on the surface modification by low-temperature plasma from a perspective of surface oxidation degree

Particle size is an important parameter to determine the surface modification degree of sulfide minerals by plasma as well as the floatability of minerals. However, little studies have been reported to quantitatively relate surface oxidation and sample particle size to flotation performance. In this study, X-ray photoelectron spectroscopy (XPS) was used to characterize the surface species of arsenopyrite and pyrite at different plasma modification times. The critical oxidation degree was quantified as the proportion of hydrophilic oxidation species to hydrophobic species and correlated with flotation recovery. The results showed that the flotation recoveries of minerals with different particle sizes were determined by surface oxidation rate and critical oxidation degree. Fine particles were more likely to become hydrophilic under low-temperature plasma modification and yet the critical oxidation degree was also higher. The coarse particles being plasma modification presented a poor flotation recovery due to its low adsorption density of collector, although its oxidation degree was lower than the fine size fraction. The critical oxidation degree of pyrite was expected to be less than arsenopyrite, but its flotation recovery was higher under the same plasma medication time because of its slower oxidation rate.