Sphalerite activation in the presence of iron ions

Zhang, Qingsong, 1963-; Zhang, Qingsong, 1963-

Thesis

Sphalerite activation in the presence of iron ions

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Creator

Zhang, Qingsong, 1963-

Contributors

Finch, James A. (Supervisor)

Abstract

English

Flotation of sphalerite with xanthate in the presence of iron ions has been studied as a function of pH. Sphalerite floated readily at pH 8-11 in the presence of ferrous ions, but not in the presence of ferric ions. The Fe$ sp{2+}$ ion concentration, pH and oxygen concentration were shown to be factors in controlling flotation. Electrokinetic measurements indicated that the surface charge increased in the presence of Fe$ sp{2+}$ ions and oxygen, and decreased upon adding xanthate and in the presence of Fe$ sp{2+}$ ions with the absence of oxygen. As a prelude to surface analysis to try to identify the species responsible for the sphalerite flotation, bulk precipitates formed from iron salt and xanthate solutions under various conditions were obtained and analysed. Analysis techniques included ultraviolet spectroscopy, infrared spectroscopy, x-ray diffraction and Mossbauer spectroscopy. It was tentatively concluded that the bulk precipitates contained three ferric components: two hydroxy xanthates, Fe(OH)$ sb2$X and Fe(OH)X$ sb2$ and an iron oxide, FeO$ sb{ rm x}.$ Iron xanthate precipitates prepared over the pH range 6-12 showed a flotation response and electrokinetic behaviour similar to those of Fe$ sp{2+}$/xanthate-treated sphalerite. An ex situ X-ray photoelectron spectroscopic (XPS), ex situ infrared (DRIFTS) and in situ infrared (ATR) investigation of the interaction of sphalerite with ferrous, ferric and xanthate ions at pH 10 was undertaken. The formation of the hydrophobic surface species was found to involve initial adsorption of Fe$ sp{2+},$ followed by oxidation to Fe$ sp{3+}$ and subsequent reaction with xanthate. There was no significant incorporation of Fe$ sp{3+}.$ A three-step reaction mechanism is proposed to account for Fe$ sp{2+}$ ion activation of sphalerite: (i) adsorption of Fe(OH)$ sp+,$ (ii) oxidation to Fe(OH)$ sp{2+}$ on the surface, (iii) reaction with xanthate to form Fe(OH)$ sb2$X or Fe(OH)X$ sb2.$

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