A Quantitative Examination of the Mixed Potential Mechanism in Mineral Flotation

The origin of the present work lies in a suggestion by Salamy and Nixon, which was implemented by Tolun and Kitch-ener, and has become the principal theory of some types of flotation. However, it has never been subject o quantitative verification. The electrochemical kinetics of oxygen reduction a d those of the anodic oxidation of potassium ethyl xan-thate were examined first individually and then together. The mineral substrates used were iron pyrites and galena. The cathodic Tafel slope on pyrites was 110 mV, and the order of reaction 1.2. On galena, the slope was 120 inV. In anodic reac-tions, the Tafel slope on pyrites was 95 mV, and the order 0.7. On galena, the slope was 240 inV. Results obtained with O2 alone and xanthate alone verified the theory. Results obtained when the components were mixed gave agreement only if the excess of the adsorbed xanthate on the oxygen kinetics was taken into account. In mechanisms suggested for flotation of sulfide minerals in the presence of xanthate collectors, one may distinguish ear ly views, e.g., chemical (xanthate xanthic acid ~--- adsorbed acid) (1), and ion ex-change theories (replacement of sulfide ions of the mineral by xanthate) (2, 3). However, these were no