Investigating the evolution of surface physico-chemistry in arsenide minerals during flotation process: A study of skutterudite, gersdorffite, and nickeline

Abstract

Skutterudite ((Co,Ni,Fe)As3), gersdorffite (NiAsS), and nickeline (NiAs) are some common arsenic- and nickel-bearing minerals often encountered worldwide in mine ores and mine wastes. These arsenides can be the source of arsenic- and nickel-contaminated neutral drainage (CND) when subjected to atmospheric conditions. Environmental desulphurization by froth flotation is a promising technique used to prevent this contamination. This study fills a knowledge gap in the evolution of the surface physicochemistry of these arsenides under different conditions, in order to determine the best conditions for flotation and successful environmental desulfurization. This work evaluates the impact of grinding, air-oxidation (aging), and conditioning on the mineral surfaces, as well as their interaction with potassium amyl xanthate (PAX) as a flotation collector. The effect of activation by copper sulphate (CuSO4) was also examined. The adsorption of PAX was analyzed by ultraviolet–visible (UV–Vis) spectrophotometry and zeta potential measurements, and the surface was characterized using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) allowing the speciation of the oxidation layer across the different mineral surfaces. Dry grinding and aging of the minerals produces thin heterogenous oxide and hydroxide layers that are mainly enriched in arsenic oxides, especially in the form of arsenate (as an oxidation product of arsenite), and arsenic, cobalt, and nickel sulphates and hydroxides. Arsenides conditioning under alkaline conditions enhances the oxidation effect on the mineral surfaces compared to natural conditions. Copper sulfate activation was found to be effective on the arsenides and improves the adsorption of xanthate on the oxidized arsenide surfaces, especially under alkaline conditions. The results of this study provide a better understanding of the surface chemistry of these minerals before and after collector adsorption, which should impact their flotation behavior.