Interaction of pyrite pulps with Ag+ and Hg2+ ions. Electrochemical characterization of micrometric grains Original Research Article

We have characterized, using voltammetry, pyrite grains from previously conditioned pulps with Ag+ or Hg2+ ions either singly, with a new technique developed in the laboratory, or with carbon paste electrodes. Formation conditions of Ag2S and Ag0 on pyrite surfaces in terms of Ag+ ion concentration are specified. The excellent resolution of voltammograms obtained with single particles and the choice of an appropriate supporting electrolyte allow detection of the oxidation of Ag2S, even though its potential is very close to that of pyrite. Concerning interactions of pyrite with mercury, this contribution of electrochemistry makes clear the presence of two different species of mercury (reducible at −100 and −500 mV vs. SCE) that had never been shown until now by other methods. Even if the maximum amount of sorbed silver (6.6 × 10−4 mol/g) is ca. 20 times higher than that of mercury (3.4 × 10−5 mol/g), when both cations Ag+ and Hg2+ are present simultaneously in the solution, only mercury is sorbed on pyrite.