| Popis: |
Eh-pH diagrams have been constructed for chalcocite in the presence of xanthate. Stability regions for cuprous xanthate have been shown to be dependent on the sulfur oxidation state. As oxidation proceeded from elemental sulfur to sulfate, the copper xanthate stability region under alkaline conditions extended to lower potentials. The voltammograms indicated that xanthate reacted with chalcocite to form cuprous xanthate and a nonstoichiometric copper sulfide starting near −40 mV. This is in agreement with the thermodynamic calculations made for the case involving oxidation to elemental sulfur. However, the voltammograms showed that the initial xanthate adsorption peak, which is attributed to chemisorbed xanthate, started between −275 and −295 mV. Based on this information, chemisorbed xanthate is calculated to have a standard free energy relative to the xanthate ion of between −12.6 and −13.1 kcal/mol. |
