Developing of a Counter-Current Copper Leaching Process Using Response Surface Methodology

Abstract

ABSTRACT Due to the scarcity of water in many parts of the world, wastewater generated by hydrometallurgical processes has been recognized as a valuable resource for recovery or reuse. A method for reusing hydrometallurgical raffinate in the leaching of low-grade oxide copper ore in a counter-current leaching process was evaluated. In the first stage of the investigation, the influential factors on copper leaching, such as the amount of acid consumed (200–400 g/kg of ore), the initial iron concentration of the raffinate (5–25 g/L), the liquid-to-solid ratio (2–10 mL/g), and the duration of the leaching process (15–75 min), were examined using response surface methodology coupled with central composite design. Two responses, copper recovery and final copper concentration, were selected to determine the optimal conditions for the leaching process. Based on the statistical model, it was found that using 325 g/kg of ore of consumed acid, an initial iron concentration of 10 g/L, a liquid-to-solid ratio of 4 mL/g, and a leaching time of 60 min would result in higher values for both responses. Confirmation runs were conducted to validate the selected conditions and the suitability of the statistical model. Additionally, compositional and morphological characterization of samples before and after the leaching process was conducted using field diffusion scanning electron microscopy and X-ray diffraction analysis, which showed the dissolution of compounds such as tenorite and cuprite. In the second stage, a two-unit counter-current leaching system was adopted, as hydrometallurgical processes are usually carried out in multiple stages on an industrial scale. This leaching system was designed to maximize copper dissolution by considering the information obtained from the response surface methodology. The use of this leaching system increased the overall leaching efficiency by up to 80%. By characterizing the solid samples, it was found that the copper extraction percentage in a counter-current leaching system could be increased by simultaneously precipitating iron-bearing compounds.