Selective alkaline glycine leaching of a high-carbonate copper ore

Processing high-carbonate copper oxide ores via conventional acid leaching can be economically challenging due to excessive acid consumption by the gangue. This study investigates glycine-based alkaline leaching as a selective alternative for copper recovery from a carbonate-rich oxide ore. Response Surface Methodology (RSM) was used to evaluate the effects of key operating variables (glycine-to-copper ratio, pH, and temperature) on copper extraction. A Benchmark sulfuric acid leaching using 625 kg H 2 SO 4 / t ore yielded negligible copper extraction (∼0%), consistent with the exceptionally high carbonate content of the ore (>71 wt% calcite and dolomite) and its correspondingly high theoretical acid-neutralisation demand. In contrast, alkaline glycine leaching achieved approximately 50% Cu extraction while substantially limiting the dissolution of major gangue elements, including Fe, Al, Ca, and Mg. Automated mineralogical analysis (TIMA) showed that Cu was distributed primarily among Cu-bearing goethite (46.4% of total Cu), delafossite (26.8%), and Cu-carbonate phases (23.2%), providing a mineralogical basis for the observed differences in leaching response. The extraction plateau of approximately 50% under the investigated conditions is attributed to progressive depletion of the more readily leachable Cu phases and increasing control by less reactive and/or less accessible Fe-associated Cu phases. Finally, sulfide precipitation enabled effective Cu recovery from the leach solution and reuse of the glycine-bearing solution over four consecutive leaching cycles with limited deterioration in Cu extraction. Overall, alkaline glycine leaching provides a selective approach for treating high-acid-consuming carbonate-rich copper ores and offers a potentially sustainable pathway for future evaluation under column- and heap-leaching conditions.