Heap leaching

Vat leaching is a more complex technique as compared with the techniques described earlier. Here, the ore meant to be leached is loaded into vats that are typically made of concrete and are a few meters deep and several meters in horizontal dimensions. The vats are often fitted with filter-type bottom to facilitate solution flow through the ore bed. Usually, several vats are employed and leaching solution is pumped continuously from one tank to the top 

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Fig. 2. SQM s heap leaching of caUche tailings for iodine recovery from diluted iodate solutions.

Diluted iodate solution is obtained by hydrothermal vat leaching of caUche ore during nitrate recovery. Concentrated iodide solutions are obtained by heap leaching of old waste dumps (tailings) and low grade nitrate caUche, such as blasted overburden, left over by former nitrate producers. 

Modem heap leaching practice has also made possible the treatment of extremely lean (ca 1 g/1) gold ores, which had been considered uneconomic... 

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. 

Percolation In addition to being applied to ores and rock in place and by the simple technique of heap leaching (usually on verv large scale see Wadsworth, loc. cit.) percolation is carried out in batcJi tanks and in continuous or dump extractors (usually on smaller scale). 

In the most common hydrometallurgical process for zinc manufacturing, the ore is leached with sulfuric acid to extract the lead/zinc. These processes can operate at atmospheric pressure or as pressure leach circuits. Lead/zinc is recovered from solution by electrowinning, a process similar to electrolytic refining. The process most commonly used for low-grade deposits is heap leaching. Imperial smelting is also used for zinc ores. 

Gold recovery Operation of carbon in leach, carbon in pulp, and heap leach circuits Recovery of gold from tailings dissolved in sodium cyanide... 

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-... 

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.

Holtum, D. A. Murray, D. M. Bacterial heap leaching of refractory gold sulfide ores. Miner. Eng. 1994, 7, 619-631. 

Hydrometallurgical methods are normally employed for recovery of gold from oxidized deposits (heap leach), low-grade sulphide ores (cyanidation, CIP, CIL) and refractory gold ores (autoclave, biological decomposition followed by cyanidation). 

Health R D (research and development) expenditures, 27 612 Health standards, at nuclear power facilities, 7 7 551-554 Health uses, for iodine, 74 372-373 Heap and dump leaching, 76 153 Heap leaching, 72 689-690, 699-700 76 128... 

Determining the effects of impurity build-up on recycle of the extraction raffinate to the heap leaching operation, and on recycle in the extraction and electrowinning circuits ... 

T0486 Los Alamos National Laboratory, Uranium Heap Leaching Technology... 

T0746 STC Remediation, Inc., Solidification/Stabilization Technology T0756 Supercritical Water Oxidation—General T0773 Terra Vac, Heap Leaching... 

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