O. Herreros

Copper extraction from reverberatory and flash furnace slags by chlorine leaching

Abstract The effects of the stirring speed, temperature, initial chlorine and chloride concentrations, particle size, addition order of the reactants and slags on the copper and iron dissolution from reverberatory and flash furnace slags were investigated. Extractions in the range of 75 and 80% Cu and about 5% Fe were obtained at room temperature. The most significant parameters were the particle size and the initial chlorine concentration. A mineralogical characterization of the reverberatory and flash smelting slags, using X-ray diffraction (XRD), optical microscopy, scanning electron microscopy (SEM) coupled to an X-ray energy dispersive spectrometer (EDS) and microanalysis (EPMA), was made. This characterization indicated that most of the copper is in the form of metallic copper, chalcocite, bornite and other complex sulphides of very small size, mainly 5–10 μ m. Iron is present principally as the matrix of a vitreous phase, fayalite and magnetite. An average only 0.2–0.4% of the copper was found in the silicate phases.

Dissolution kinetics of enargite in dilute Cl2/Cl- media

Abstract A study was made of the dissolution kinetics of enargite, Cu 3 AsS 4 , with chlorine generated in solution by the reaction between sodium hypochlorite and hydrochloric acid. The effects of stirring speed, initial chlorine concentration, particle size, and temperature were investigated. The kinetics of the dissolution were characterized by two sequential stages: relatively fast reaction initially, while later the reaction became very slow. In the first stage, the fraction of copper extracted varied linearly with time according to α = k 1 t , whereas in the second stage, the dissolution was well represented by the shrinking core model controlled by diffusion through a porous product layer with kinetic equation: 1−3(1− α ) 2/3 +2(1− α )= k 2 t . The S 0 product layer acts as a diffusion barrier. The calculated activation energies were 15.0 kJ mol −1 (3.5 kcal/mol) for the first stage and 21.0 kJ mol −1 (5.0 kcal/mol) for the second. For the first stage, an apparent reaction order of 1.0 was found with respect to the chlorine concentration; for the second stage, an apparent reaction order of 1.8 was obtained.

Kinetics of the aqueous chlorination of gold in suspended particles

Abstract The effects of the particle geometry and size, stirring speed, pH, chlorine and chloride concentrations and temperature on the kinetics of the aqueous chlorination of gold were studied. Surface examinations of gold samples leached in different conditions were carried out by SEM/EDS and XPS. The kinetics appear to be chemically controlled in conditions of full suspension of the particles. The dependence of pH and the chlorine and chloride concentrations indicate that the rates were essentially determined by the concentration of the trichloride ion. The expression obtained for the specific rate was: Rate (mol cm−2 min−1) = 4.25 105 [Cl3−] exp ( −43.5 R T ) A discussion of the possible mechanism is included, based on the kinetic dependence, previously reported electrochemical studies and mixed potential measurements.

Dissolution kinetics of copper, white metal and natural chalcocite in Cl2/Cl- media

In order to explain the model of kinetics control on the dissolution of metallic copper, white metal, and natural chalcocite, the effects of the stirring speed, pH, initial chlorine and chloride concentrations, particle size, and temperature were investigated. The kinetics appear to be mass transport-controlled in conditions of full suspension of the particles, with activation energies of 17.9 kJ/mol (4.3 kcal/mol), 23.3 kJ/mol (5.6 kcal/mol), and 22.4 kJ/mol (5.4 kcal/mol) for copper, chalcocite, and white metal, respectively. The dependence of pH, temperature, and chloride concentration indicate that the rates were essentially determined by the concentration of chlorine.