Secondary ion mass spectrometry investigation of the interaction of xanthate with galena

Abstract

Static SIMS has been used to study the interaction of xanthate with freshly cleaved and oxidised galena surfaces in neutral and alkaline pH conditions. Three xanthate fragments together with O and S negative ion images have been compared. At low xanthate concentration (10 −5 mol dm −3) and high Eh (pH 7.1), freshly cleaved galena surfaces show very low xanthate adsorption due to dissolution. At low xanthate concentration and low Eh (pH 8.7), surface oxidation and dissolution are reduced with an overall higher concentration of mono-molecularly adsorbed xanthate. At high xanthate concentrations (10 −2 mol dm −3, pH 8.7–9.9), freshly cleaved galena surfaces adsorb colloidal PbX 2 from solution. Oxidised galena surfaces have relatively low concentrations of adsorbed xanthate compared with freshly cleaved galena surfaces at both low and high xanthate concentrations and at low and high Eh (pH 7.1–9.9). Adsorbed colloidal PbX 2 is not found even at high xanthate concentrations apparently due in part to surface oxidation products passivating against continuing dissolution. Colloidal lead oxide/hydroxide particles have been imaged after 10 −5 mol dm −3 lead nitrate addition at pH 7. Following xanthate addition (10 −5 mol dm −3) at pH 8.7, large, roughly circular regions (25–75 μm) of high xanthate concentration were obtained in initial images apparently nucleating at lead oxide/hydroxide precipitate sites. The behaviour of this system is consistent with ion exchange between xanthate and hydroxide followed by oxidation to dixanthogen and diffusion of this species across the surface. The precipitated lead oxide/hydroxide may play a catalytic role in the formation of the dixanthogen on the galena surface.