Redox processes in sulfide minerals biochemical solutions reactions

Abstract

Rebellious gold-bearing ores contains among the most abundant minerals as arsenopyrite and pyrites, such natural minerals as chalcopyrite (CuFeS2) and sphalerite (ZnS) impacting the redox processes behavior in these ores leaching. The anodic current maximum (peak) was identified on the sphalerite polarization curve that evidently proves a single-stage process. Curves within –1.5–0 V potentials range are not tending to reach an ultimate current with increasing potentials. Only a log-linear increasing of anodic current with increased values of potentials density defining redox process rate was found. The effects of sphalerite bacterial pretreatment on its oxidation were identified. Sphalerite was treated through 80 days exposure to alkali solution (рН = 9–9.5) containing 108–1010 cells/cm3 of Pseudomonas aureofaciеns bacteria. Polarization current density at anodic oxidation of sphalerite treated with solution of рН = 9 within 0.3–2.0 V potentials range increased by 20 % as compared to an untreated sphalerite. Temperature effects on sphalerite electrochemical oxidation with solution of рН = 9 were studied for 25–55°С temperatures. Sphalerite oxidation rates substantially increased at 0.5–2.0 V (by 1.7–2.3 times) with temperature increasing from 25°С to 55°С. Values of effective energy of anodic sphalerite oxidation process activation were determined by temperature-kinetic method (through lni –1/Т dependence) at рН=9. Study data proved that the oxidation process rates within 0.6–2.0 V potentials range are limited by electrochemical reaction rates (49.0–52.8 kJ/mole). Oxidation proceeded at diffusion-kinetic conditions (20.9–32.4 kJ/mole) within 0.4–0.5 V potentials range. Thus, increased chalcopyrite and sphalerite oxidation rates were identified for alkali-cyanide solutions through pretreatment with Pseudomonas aureofaciеns bacterial solution.