Sur l'electrosorption d'ethylxanthate au cours de la polarisation anodique d'electrodes de platine et de galene

Abstract

The main results concerning the galena flottation by xanthates which are relevant from an electrochemical point of view are presented. The usual kinetic theories were unable to explain the results obtained in previous electrochemical studies on xanthate oxidation at various electrodes. A modified treatment is reported. It reconciles data indicating the same phenomenology as that taking place when a monolayer is chemisorbed as well as quantitative results suggesting the presence of a thick layer. The result previously obtained with platinum and galena electrodes can thus be quantitatively interpreted. It is concluded that the complexity of the chronoamperometric data derives more from the adsorbed layer structure than from the reaction scheme. The latter is composed of the xanthate physisorption followed by chemisorption. The adsorbed phase with tens of monolayers is assumed to be analogous to a lamellar phase of a liquid crystal. It is electrically conducting and its thickness is not dependent on the substrate. However. the nature of the latter controls the oxidation rate and the possible occurrence of passivation. The electrochemical results and those obtained by other technics on dispersed systems are well can be interpreted by the proposed model.