Abstract

Sulfide ores will be the main resources exploited in the Chilean copper industry in the coming years because of the exhaustion of oxide. The primary process currently used for copper extraction from sulfide ores is mineral concentration. That means that a decrease of 50% in the production of electrowon cathodes together with an increase in copper production is expected in Chile with the concomitant loss of advantages like additional revenues from valuable metals contained in the concentrates. In addition, copper leaching in concentrated chloride media under ambient conditions is already used in several Chilean operations to benefit secondary sulfide ore and has gained broad attention in hydrometallurgy due to its faster kinetics and higher recovery when compared to bioleaching. Furthermore, validation tests for chloride leaching of crushed primary sulfide ores are under development. Copper bioleaching, mainly of run-of-mine (ROM) copper ores, is a better option for marginal materials than concentration because of the energy cost impediments of crushing and grinding. On the other hand, the main aspects considered in evaluating the economic advantage of leaching in concentrated chloride media under ambient conditions versus bioleaching process are copper grade and expected solution inventory, salts availability and cost, environmental restrictions, and surface availability. It is foreseen that bioleaching will play a complementary role to sulfide mineral concentration mainly in operations that have vacant solvent extraction and electrowinning (SX/EW) plants because of the exhaustion of oxide ores. We will present and discuss the main variables considered, and the metallurgical tests that should be performed for the process’s evaluation and the scenarios for processes combination. In addition, we´ll present the ROM bioleaching at Minera Escondida Ltd. (MEL) that has played that complementary role since 2006, and where more than 250,000 t of copper as cathodes were produced in 2021, and 60% of them by bioleaching.