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The chelators bind the copper ions (and no other ions, ideally), the resulting complexes dissolve in the organic phase. This organic solvent is evaporated, leaving a residue of the copper complexes. The copper ions are liberated from the residue with sulfuric acid. The barred (denuded) sulfuric acid recycled back on to the heaps.
This method is an acid heap leaching method like that of the copper method in that it utilises sulfuric acid instead of cyanide solution to dissolve the target minerals from crushed ore. The amount of sulfuric acid required is much higher than for copper ores, as high as 1,000 kg of acid per tonne of ore, but 500 kg is more common.
Biological substances can experience leaching themselves, [2] as well as be used for leaching as part of the solvent substance to recover heavy metals. [6] Many plants experience leaching of phenolics, carbohydrates, and amino acids, and can experience as much as 30% mass loss from leaching, [5] just from sources of water such as rain, dew, mist, and fog. [2]
In-situ leaching of copper was done by the Chinese by 907 AD, and perhaps as early as 177 BC. [4] Copper is usually leached using acid (sulfuric acid or hydrochloric acid), then recovered from solution by solvent extraction electrowinning (SX-EW) or by chemical precipitation.
Leading up to World War I, many new ideas for leaching processes were experimented. [4] This included using ammonia solutions for copper sulfides, and nitric acid for leaching sulfide ores. [4] Most of these ideas were phased out into obscurity due to the high cost of the leaching agents required. [4]
In the case of oxide copper ore, a heap leaching pad will dissolve a dilute copper sulfate solution in a weak sulfuric acid solution. This pregnant leach solution (PLS) is pumped to an extraction mixer settler where it is mixed with the organic phase (a kerosene hosted extractant). The copper transfers to the organic phase, and the aqueous ...
Production from the capping of oxidised minerals, which required mere leaching in sulphuric acid to dissolve the copper and the recovery of the copper by electrolysis was the sole means of production until the 1950s.
Leaching involves the use of aqueous solutions to extract metal from metal-bearing materials which are brought into contact with them. [3] In China in the 11th and 12th centuries, this technique was used to extract copper; this was used for much of the total copper production. [4]