Alternative flotation collectors for the environmental desulfurization of gersdorffite (NiAsS) bearing mine tailings: Surface chemistry

Abstract

Environmental desulfurization by froth flotation is a promising technique for the control of acid mine drainage (AMD) and has already been applied in a wide variety of mining operations to prevent environmental risks. This paper aims to address the flotation challenges of gersdorffite for environmental purposes. Gersdorffite, a Ni-As-sulfosalt (NiAsS) frequently encountered in many gold mine wastes, is a major source of contamination. Gersdorffite surface characterization was conducted using diffuse reflectance infrared fourier transform (DRIFT) spectroscopy and optical microscopy, to gain a better understanding of the physicochemical evolution of the mineral surface. The main parameters evaluated were the impact of air-oxidation (aging) and the effect of pH at different values using different reagents (soda ash (NaOH) and lime (CaO)) on the mineral surface chemistry. Collector adsorption behavior was also studied using four collector types as alternatives to xanthate, mainly based on dithiophosphates (DTP) and mercaptobenzothiazole (MBT). Dry grinding of the gersdorffite generated a thin and heterogeneous particle coating mainly composed of arsenic oxides (arsenite and arsenate) and nickel sulfates (NiSO4), with minor elemental sulfur. Hydroxylated Ni species (Ni-OH) were also observed. MBT molecules were found to be the most active compound responsible for the adsorption of the collectors as demonstrated by the adsorption isotherms and the DRIFT spectra. The results of this study have led to a better understanding of gersdorffite surface chemistry before and after the collector adsorption, which should impact its flotation behavior.