Enhancement of copper mobilization using acidic AlCl3 − rich lixiviant

Copper (Cu) extraction from low-grade ores is limited by the formation of secondary minerals that can passivate the surfaces of Cu-sulphide minerals in these ores. Hence, a novel approach utilizing AlCl₃ as a lixiviant was developed to modify coupled dissolution-reprecipitation processes at the mineral interface. The formation of Al-rich phases instead of Fe-hydroxysulphates enhanced Cu extraction through combined ferric-iron and proton-promoted dissolution. AlCl₃ accelerated chalcopyrite and bornite dissolution by forming soluble intermediate Cu-phases (e.g., covellite) at consistently high Eh (550–650 mV) and acidity due to the Lewis acid property of AlCl₃. X-ray diffraction analysis revealed that Na-bearing jarosite [(K_0.61Na_0.41) Fe₃(SO₄)₂(OH)] and sideronatrite [Na₂Fe(SO₄)₂(OH)(H₂O)] formation in lixiviants without AlCl₃ decreased Fe³⁺_(aq) availability for Cu-sulphide minerals dissolution. In contrast, significant amounts of AlSO₄⁺_(aq) formed in the AlCl₃-rich lixiviant at pH 1–3, which reduced the sulphate activity and decreased the saturation state of the Fe-hydroxysulphates. Further, AlCl₃ promoted the formation of amorphous, porous Al-rich phases, facilitating quick Fe diffusion through the passivating layer and improving Cu recovery compared to lixiviants containing CaCl₂, NaCl, or acid-only.