Optimization Of Sulfuric Acid Leaching Of Copper From A Cu–Fe Oxidized Ore From Kongo Central Province, Democratic Republic Of Congo

Abstract

The Democratic Republic of Congo (DRC) is among the world’s major copper-producing countries and possesses significant reserves of oxidized copper ores. In order to sustain the growth of the mining sector and improve the economic valorization of low-grade polymetallic deposits, the optimization of hydrometallurgical extraction processes remains a major industrial challenge. This study aimed to optimize the sulfuric acid leaching of copper from a Cu–Fe oxidized ore originating from Kongo Central Province, while minimizing iron dissolution. The investigated ore was mainly composed of cuprite (Cu₂O), malachite (Cu₂CO₃(OH)₂), and limonite (5Fe₂O₃·2SiO₂·9H₂O). Mineralogical and chemical characterizations were performed using X-ray diffraction, atomic absorption spectrometry, inductively coupled plasma analysis, and conventional chemical methods. Leaching experiments were carried out using a fractional factorial experimental design in order to evaluate the effects of acid formality, particle size, temperature, slurry density, and stirring speed on copper and iron dissolution. The results showed that acid formality (AF) and slurry density (SD) were the most influential parameters controlling copper extraction. The developed optimization model for copper leaching was expressed as: Y = 0.284 + 0,183FA - 0.070 DS + ε Optimal operating conditions were obtained at an acid formality of 0.40 mol·dm⁻³, a particle size between 90 and 125 µm, a temperature of 50–60°C, an agitation speed of approximately 550 rpm, and a solid/liquid ratio of 1/10. Under these conditions, copper extraction reached 65.9%, whereas iron dissolution remained limited to 1.02%. Kinetic investigations revealed that an optimal residence time of two minutes allowed selective copper extraction with minimal iron co-dissolution. One extraction stage theoretically yielded 54.7% copper extraction while dissolving only 0.5% iron. Repetition of the leaching process over several stages could therefore selectively exhaust copper from the ore. This study demonstrates the potential of sulfuric acid hydrometallurgy combined with factorial experimental design for the selective recovery of copper from oxidized Cu–Fe ores in the Democratic Republic of Congo.