Evaluation of disodium carboxymethyl trithiocarbonate as a depressant reagent for chalcocite: An electrochemical approach

Abstract

The effect of the organic depressant disodium carboxymethyl trithiocarbonate (Orfom® D8) on the mineral chalcocite (Cu2S) was investigated with mixed potentials (Em), microflotation, UV–vis spectrophotometry, electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FTIR). The mixed potential measurements revealed a decrease in the potential as the depressant dosage was increased, which was attributed to adsorption of the depressant. Microflotation results showed that the mineral recovery percentage decreased from 56.37 % to 5.20 − 11.94 %, depending on the depressant concentration and solution pH. The fits of the experimental data indicated that the depressant was chemically adsorbed, and this was corroborated by EIS studies that indicated an electrochemical mechanism involving the depressant and the mineral. The proposed adsorption mechanism involved oxidation of the depressant for the formation of Cu(D8–)2 and CuD8– complexes on the chalcocite surface in addition to the formation of CuD8– complexes on the oxidized surface (Cu1.95S and Cu1.8S); thus, these complexes were responsible for depression of the mineral. AFM measurements revealed roughness changes associated with depressant adsorption and surface oxidation of the mineral. Finally, the FT-IR spectra showed that adsorption of the D8 depressant on chalcocite occurred through the trithiocarbonate group, which oriented the carboxylate group away from the mineral surface, thus conferring hydrophilic character. The observed behavior indicated that the Orfom® D8 depressant can be used as a chalcocite depressor in a selective flotation separation stage with an adsorption mechanism different from that proposed for chalcopyrite but with a similar depressor effect.