ADSORPTION OF ETHYL XANTHATE ON FRESHLY EXPOSED GALENA SURFACES

The coverage of xanthate on freshly abraded galena surfaces after immersion in ethyl xanthate solutions in equilibrium with air has been determined by cathodic stripping voltammetry. The coverage varied from a small fraction of a monolayer to multilayers depending on xanthate concentration and time of immersion. Galena surfaces, formed by fracture under ethyl xanthate solutions in equilibrium with air, and left immersed for selected periods, were also examined by electron spectroscopy. For all conditions investigated, except treatment in 10(-4) mol dm-3 xanthate at pH 9.2 for less than 1 h, adsorbed xanthate was evident from the presence of a shifted component in the S(2p) spectrum. The absence of such a component at shorter times in this medium is explained in terms of a low xanthate coverage and the relatively large analysis depth associated with the S(2p) photoelectrons. The more surface sensitive S(L2,3MM) and Pb(N6,7OO) X-ray induced Auger spectra were also recorded for these experimental conditions and changes in the relative intensities of the peaks were consistent with xanthate adsorption. The xanthate coverage was also determined as a function of potential by stripping voltammetry. Comparison with the potential dependence of flotation recovery of galena with ethyl xanthate reported in the literature indicates that flotation commences when very low coverages of xanthate are established, and that maximum recovery is attained when only a fraction of a monolayer is adsorbed.