Dump leaching

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Dump leaching is one of several leaching methods. Dump leaching is carried out on rejected off-grade material that during normal mining has been put aside in big dumps at the mine site. The particle size of the material is generally big and the ore is processed for many years by sprinkling acidified water on the dump surface. The leach solution percolates through the dump and is collected in ditches at the base of the dump. It can be considered to be a crude version of heap leaching where no special arrangements are made to increase the leaching rate. Therefore, metal recoveries from dump leaching operations are low and the duration of the operation is relatively long. Problems may arise if the base of the dump is not properly prepared, causing losses of solution. This might become a source of environmental pollution if leachate escapes collection and flows into natural water-supplies. The initial plants for copper recovery by dump leaching from oxide ore were a success and led to the development of heap leaching for ores with higher grade.

Comments on dump bioleaching

Dump bioleaching has been performed on some waste dumps containing chalcopyrite but both leaching rates and recoveries are low. In cases where dump bioleaching of chalcopyrite has been practised it is as a side operation where infrastructure for metal extraction, i.e. solvent extraction and electrowinning (SX-EW) already exists. One example of such operations is at Gibraltar Mines in Canada.

Examples of in-situ bioleaching operations

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