How does gold leaching work?
Leaching dissolves the gold out of the ore using a chemical solvent. The most common solvent is cyanide, which must be combined with oxygen in a process known as carbon-in-pulp. As the cyanide and oxygen react chemically, gold in the pulp dissolves.
Is o2 required in leaching of gold?
Compared to air injection, oxygen in the leaching step increases the rate of gold dissolution, in some cases enhances the final gold recovery and is often accompanied by savings in cyanide, especially when oxygen is used during pre-aeration.
How do you leach gold?
A sodium cyanide solution is commonly used to leach gold from ore. There are two types of leaching: Heap leaching: In the open, cyanide solution is sprayed over huge heaps of crushed ore spread atop giant collection pads. The cyanide dissolves the gold from the ore into the solution as it trickles through the heap.
What is used for leaching of gold?
Leaching gold with a cyanide solution remains the most widely used hydrometallurgical process for the extraction of gold from ores and concentrates.
How long does it take to leach gold?
Generally, the finer the gold, the quicker it will dissolve. A 45 micron particle of gold would dissolve in 10-13 hours, while a 150 micron particle might take from 20 to 44 hours to dissolve in the same solution. Oxygen plays an important role in the leaching of gold in a cyanide solution, also.
What chemicals can leach gold?
Gold leaching is the key stage in process of gold mining. There are a few well-reputed leaching methods using a variety of different reagents. Nowadays the most popular industrial processes include cyanide, thiourea, and thiosulfate leaching methods.
What chemicals will leach gold?
What is the most common solvent used for leaching gold?
Cyanide solutions are a solvent for the precious metals, while a sodium chloride solution dissolves some chlorides. In all cases the leach solvent should be cheap and available, strong, and preferably selective for the values present.
Can you leach gold without cyanide?
A new technology that delivers commercial-scale, cyanide-free gold processing has been released by Australian-based company Clean Mining. The process replaces cyanide with a safer, less hazardous chemical reagent called thiosulphate.
What is the disadvantage of leaching?
Drawbacks of leaching include its lower efficiency and the often significant quantities of waste effluent and tailings produced, which are usually either highly acidic or alkali as well as toxic (e.g. bauxite tailings).
What is a substitute for cyanide?
The substitutes for cyanide can be classified as traditional and novel non-cyanide gold leaching reagents. The traditional alternatives mainly include thiourea, halide, polysulfide, thiocyanate, lime sulfur synthetic solution (LSSS), and thiosulfate (Hilson and Monhemius, 2006, Sun et al., 2020, Xing et al., 2019).
What dissolves gold other than cyanide?
The solution replaces cyanide with a safe, alternative reagent known as thiosulphate. Thiosulphate dissolves the fine gold out of ores (the gold that has not recovered by gravity) at similar rates to conventional techniques.
Is leaching good or bad?
Leaching removes vital nutrients and micronutrients, such as water-soluble boron, from the soil, causing potential deficiencies in crops.
How can you dissolve gold without cyanide?
Thiosulphate leaching is a process that removes gold from gold bearing ores without the use of cyanide. Although not as aggressive a leaching agent as cyanide, thiosulphate offers several technological advantages including its lower toxicity and greater efficiency with gold deposits associated with preg-robbing ores.
How does temperature affect gold leaching?
The increase in temperature would be expected to increase the activity of the solution and thus increase the rate of dissolution of gold. At the same time the amount of oxygen in the solution would decrease because the solubility of gases decreases with increasing temperature.