Pilot tests for processing oxidized copper ores from the Erdenetiin Ovoo deposit using heap leaching

In the current context of declining reserves of high-grade copper sulfide ores, oxidized ores are becoming an important source of mineral raw materials containing non-ferrous and precious metals. Traditional flotation processing of these ores results in low-grade concentrates with poor metal extraction rates (40–60 %). Heap leaching is considered the most promising method for processing such ores. As a result of prolonged intensive mining at the Erdenetiin Ovoo deposit (Erdenet, Mongolia), approximately 800 million tonnes of oxidized ore dumps with an average copper content of 0.45–0.48 % have accumulated within the open-pit boundary. Global experience in processing such secondary raw materials demonstrates the high economic efficiency of copper extraction through heap leaching, followed by solvent extraction and electrowinning (SX-EW) of copper from the pregnant leach solution. For the State-owned Enterprise Erdenet, it is essential to conduct leaching studies on oxidized ores and pilot testing of this technology on the ore from existing ore dumps. To achieve this, 35 boreholes were drilled in the dumps (16 in dump No. 8a and 19 in dump No. 12), from which core samples were collected. The mineralogical composition of the oxidized copper ore samples was analyzed, and the effect of heap leaching parameters (ore particle size, solution acidity, etc.) on copper recovery into the pregnant leach solution was determined. To more accurately assess the recoverable copper from the two dumps, composite samples were collected from each borehole, and large-scale heap leaching tests were conducted in 30 open-cycle columns. The test results showed that copper extraction rate from dump No. 8a ranged from 35.8 % to 69.1 %, with an average of 56.0 %, while dump No. 12 exhibited extraction rates ranging from 51.8 % to 77.4 %, with an average of 63.6 %.

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