The effect of glue, thiourea, and chloride on the kinetics of copper reduction in CuSO₄–H₂SO₄ solutions of copper composition, and temperatures like those used in the copper electrorefining plants, were studied. The kinetic study was conducted by determining the kinetic parameters ${\mathrm{i}}_0$ and $\mathsf{\beta }$ under the activation control of the Tafel approximation, which is applied to polarization curves obtained via linear voltammetry. The results show that the incorporation of glue and thiourea decreases the exchange current density, while chloride does not significantly affect the kinetic parameters. The data on the fraction of the surface covered by glue and thiourea fitted to the Temkin adsorption isotherm indicate that the mechanism of action during the reduction of copper to low overpotentials is the adsorption of these additives on the electrode surface. The adsorption of additives reduces the cathodic area available for Cu²⁺ adsorption and lateral diffusion of Cu atoms to continue the reduction process and the growth of the crystalline deposit. The kinetic study was complemented with a comprehensive analysis of the effect of the additives on the morphological and textural characteristics of the deposits. The results of this work contribute to the understanding of the mechanisms of the main additives used during the copper electrorefining process.

The mining industry is facing emerging challenges as a result of the increase in energy consumption and environmental demands. These facts have promoted the use of renewable energy sources, such as wind, geothermal and, mainly, solar energy. This paper discusses the role of solar energy (UV-VIS-NIR) in leaching processes, evaluating its potential application in metal extraction from sulfide minerals, based on photochemical mechanisms that promote the regeneration of ferric iron or the so called ferrous iron cycling. The present paper discusses the possibility that ultraviolet, visible light and near infrared irradiation (e.g., sunlight provided) can assist the leaching processes in two main ways: by the oxidation of sulfide minerals through in-situ generated Fenton-like reactions, and by the photochemical activation of semiconductor minerals that contain transition metals (Fe, Cu, and Cr, among others). Thus, this paper provides theoretical support to move towards the future application of photoleaching, which consist of a leaching process assisted by UV, VIS, and NIR irradiation. This technology can be considered a promising mineral processing route, using direct photochemical solar energy that can reduce the energy consumption (electricity, fuels) and the environmental impact, opening an opportunity for an alternative method of metal extraction from sulfide ores.

The distribution of copper, iron, and sulfur during the oxidation of La Caridad copper concentrate particles under simulated flash smelting conditions was studied in a laboratory reactor. Six wet-sieved size fractions and the unsieved copper concentrate were oxidized at 1123 K and 40% and 70% O₂ by volume in the process gas during the experiments. Samples of partially oxidized particles were collected at 0.2, 0.8, and 0.9 m from the point of entry and analyzed in a QEMSCAN^® unit to determine the elemental composition within the population of particles. The distribution of the major elements during oxidation was strongly dependent upon the size and chemical composition of the initial particles. Overall, the copper content tended to increase and sulfur content decreased along the reactor length within all sizes. In contrast, the distribution of iron did not follow a general trend, as it was found to increase, decrease, or remain unchanged depending on the particle size. This finding may represent a key feature to further investigate the reaction path followed by particles during flash smelting, especially those associated with particle fragmentation. In general, the larger the particle size was, the larger the change in the content of the major elements within the particle population. Based on the experimental results, particles within a size fraction of <45 µm tended to follow a reaction path consisting of rapid melting followed by the collision and coalescence of reacting droplets during flight. In contrast, particles within the fraction of 45–53 µm tended to react individually. The oxidation behavior of the unsieved concentrate particles showed a combination of both reaction paths.

The conversion of copper sulfide mattes lacks fundamental kinetic information for understanding the process. This work presents the results of the experimental measurement of the rate of oxidation of molten white metal by supplying individual air bubbles. The bubbles were characterized from information collected during the experiments and through theoretical and empirical correlations. Conversion tests were carried out at different temperature conditions and injection dynamics of the oxidizing gas. The results indicate that the conversion is controlled by the transport of oxygen into the bubble. A dependency between the characteristics of the injector and the shape, size and surface of the bubbles was identified. The oxidation rate of the white metal depended on the characteristics of the bubbles and the oxygen available for conversion. The results of this research provide relevant information to improve the operation of industrial conversion furnaces by controlling gas injection through the tuyeres. The criterion for improving conversion systems is the balance between the retention of the bubbles in the molten white metal and their size, such that the availability of oxygen for the conversion is guaranteed.