TL Leaching: Experimental Studies For The Lo Aguirre Leach Project

The Lo Aguirre ore deposit of Sociedad Minera Pudahuel is expected to have a life of 12 years, producing 16,500 mt per year of copper cathodes. The total copper content of the ore ranges from 2% in acid-soluble form to 2% as sulfides. Sociedad Minera Pudahuel chose TL leaching, solvent extraction, and electrowinning as the processing steps to give low investment and operating costs. Design and operating criteria of the TL leach plant have been obtained in an experimental program carried out since 1974. Bench scale tests indicated that 90% of the oxidic copper and 35% of the sulfidic copper could be extracted to give 5 gpl copper by treating crushed ore with acid, curing, and rinsing in a column with a dilute acid solution containing ferric sulfate which is requllred to solubilize the sulfides. These results were verified in a pilot plant which combined leaching, solvent extraction, and electrowinning. Raffinate was recycled to the leaching circuit after oxidation to regenerate ferric ion. Refinements in the processing have resulted in significant improvements in extraction to give 95% to 98% recovery of the oxidic copper and 55% and 60% of the sulfidic copper. The plant is expected to give this degree of recovery. As a consequence, the original plan to include a concentrator in the plant has been abandoned.