Infrared investigation of amylxanthate Adsorption on galena: Influence of oxidation, pH and grinding

Abstract

A dynamic method (chromatographic saturation front analysis), batch adsorption tests and Fourier-transform infrared diffuse reflectance spectroscopy have been used to investigate the adsorption/abstraction of amylxanthate on galena surfaces. The galena was either pretreated in order to obtain “clean” galena (i.e. unoxidized), and then oxidized by dissolved oxygen in aqueous solutions, or wet ground under controllable conditions (pH 4 and natural pH 9.3). The oxidation of galena by dissolved oxygen is insufficient to provide the degree of surface oxidation necessary for important adsorption/abstraction. In this case the surface products are stoichiometric lead xanthate and xanthate radicals coordinated with one metal atom. The amount of amylxanthate abstracted is drastically reduced, if dissolved oxygen is eliminated. Air during wet grinding provokes an oxidation of the galena surface. The surface oxidation products mainly consists of PbCO 3 and PbS 2O 3. Amylxanthate is readily adsorbed onto this surface: (i) as monocoordinated lead xanthate in near monolayer thickness and (ii) as non-stoichiometric (natural pH) and/or stoichiometric (pH 4) lead amylxanthate multilayers which replace the oxidation products at higher concentrations. Other adsorption products form in the multilayer regions: amyldixanthogen and the dimer of monothiocarbonate. At high concentration, dixanthogen forms preferentially. Acid wet grinding favours the adsorption/abstraction of xanthate.