Heap copper

In unsteady-state leaching a common method used in the mineral industries is in-place leaching, where the solvent is allowed to percolate through the actual ore body. In other cases the leach liquor is pumped over a pile of crushed ore and collected at the ground level as it drains from the heap. Copper is leached by sulfuric acid solutions from sulfide ores in this manner. 

Table 1 gives the average metal content of the earth s cmst, ore deposits, and concentrates. With the exceptions of the recovery of magnesium from seawater and alkaU metals from brines, and the solution mining and dump or heap leaching of some copper, gold, and uranium (see Uranium and uranium compounds), most ores are processed through mills. Concentrates are the raw materials for the extraction of primary metals. 

In the most common hydrometallurgical process, the ore is leached with ammonia or sulfuric acid to extract the copper. These processes can operate at atmospheric pressure or as pressure leach circuits. Copper is recovered from solution by electrowinning, a process similar to electrolytic refining. The process is most commonly used for leaching low-grade deposits in situ or as heaps. 

The sulfuric acid needed to solubilize copper from chalcocite is balanced by the acid recovered from the copper electrowinning step this acid is recycled to the heaps. The overall acid requirements for the process are, therefore, dependent on the acid consumption by the gangue minerals in the ore and the acid production by pyrite oxidation. If the pyrite associated with the ore is significant and the acid consumption by the ore is low, excess sulfuric acid can be neutralized by lime. 

The present description pertaining to copper refers to solvent extraction of copper at the Bluebird Mine, Miami. When the plant became operational in the first quarter of 1968 it used L1X 64, but L1X 64N was introduced in to its operation from late 1968. The ore consists of the oxidized minerals, chrysocolla and lesser amounts of azurite and malachite. A heap leaching process is adopted for this copper resource. Heap-leached copper solution is subjected to solvent extraction operation, the extractant being a solution of 7-8% L1X 64N incorporated in kerosene diluent. The extraction process flowsheet is shown in Figure 5.20. The extraction equilibrium diagram portrayed in Figure 5.21 (A) shows the condi-... 

Recovery of copper from solutions generated in heap/dump leaching with sulfuric acid by cementation with iron. 

Copper leaching Copper concentrate, sulfuric acid Uncontrolled leachate Heap leach waste... 

Heap leaching of copper oxides and transition ores and acid/neutral leaching of zinc calcine are well-established processes to generate the feed solutions for the hydrometallurgical recovery of these metals.2... 

The application of solvent extraction to copper recovery has been a major growth area since the last review of this series.11,13 Almost 30% of world production in 2000 involved the use of sulfuric acid heap leaching, solvent extraction, and electrowinning, far exceeding earlier predictions.136... 

Figure 5 A simplified flowsheet and materials balance for the recovery of copper from oxidic and transition ores by heap leaching, solvent extraction and electrowinning.

Nord Copper Johnson Camp Heap (oxide) 3,000 1990... 

The uranium heap leaching technology is an ex situ adaptation of a 20-year-old heap leach mining (i.e., of gold, silver, and copper) technique used to treat soil. Each soil/contaminant chemical treatment combination is unique and must be developed separately. The equipment required for field-scale uranium heap leaching is basically the same as the equipment used in standard mining practices. 

The Terra Vac heap leaching technology is an ex situ hazardous remediation process that has been previously applied by the mining industry to recover gold, uranium, copper, and other... 

Hydrometallurgical methods4,5 use reactions in aqueous solution (often involving metal complex formation) to concentrate and/or separate the metal ions of interest. A commercially important example is the heap leaching of low-grade copper ores with acid. 

Heap (dump) acid leaching of copper sulfide ores is possible with the aid of microbial oxidation. Not all copper minerals are sulfidic, however— malachite, azurite, and chrysocolla are basic copper carbonates—and sulfuric acid heap leaching of low-grade copper carbonate ores can give solutions from which the Cu2+ ion can be separated by solvent extraction (Section 17.3) and copper metal obtained by electrowinning. 

Several such schemes have been developed to recover copper from dilute solutions obtained (usually) by acid heap leaching of low-grade copper ores.9 The required properties of a complexing agent L in the extractant axe ... 

The formation of the chlorides is effected in the dry way by calcination with sodium chloride or in the wet way by interaction with ferrous chloride and hydrochloric acid or with ferric chloride. The wet way is only adopted if fuel is scarce, or the escape of noxious vapours into the atmosphere is not permissible. In the dry method the ore is oxidized by a preliminary roasting, and then chloridized by calcination with sodium chloride or Abraum salts in a furnace of the reverberatory or muffle type, the principal product being cupric chloride. The Dotsch modification of the wet process, worked at Rio Tinto, depends on the action of ferric-chloride solution on a mixture of the ore with sodium sulphate and ferric chloride. The liquid drawn off from the bottom of the heaps of ore contains cuprous chloride in solution as a complex salt. The copper is liberated by the action of iron, the ferrous chloride simultaneously formed being chlorinated in towers to ferric chloride, and the product employed for moistening the heaps of ore. 

In the patio process the finely ground ore is mixed in a patio or paved courtyard with mercury, common salt, and a mixture of copper and iron sulphates called magistral, prepared by roasting copper pyrites. The ore-heap or torta is kept moist. The reactions involved are obscure and complex, but it is supposed 1 that some of them can be represented thus ... 

This reaction has been utilised in the separation of copper from pyrites, a solution of ferric chloride being allowed to slowly percolate through the ore raised in heaps, the residual ferrous chloride being oxidised to ferric and used over again.3... 

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