What is thiosulfate leaching?
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.
What reagent is used for leaching of gold?
Sodium cyanide has been the preponderant leaching reagent for gold due to its excellent extractions from a great variety of ores and its low cost. Although cyanide is poisonous, it has safe industrial and environmental records at the high pH range required in cyanide leaching.
What is the leaching process for gold?
Cyanide leaching has been the industry standard for gold processing for more than 100 years. During the cyanide leach process, a cyanide solution, or lixiviant, is percolated through ore contained in vats, columns or heaps. Gold is dissolved by the cyanide and then removed from the heap or columns.
How do you leach gold from ore?
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 the chemical formula for gold I thiosulfate?
Gold(I) Thiosulfate Au2S2O3 Molecular Weight — EndMemo.
Is thiosulfate cheaper than cyanide?
Thiosulfate leaching appears to be an innovative and eco-friendly alternative for the upcoming replacement of cyanidation; besides, thiosulfate is cheaper than cyanide.
What is leaching reagent?
Leaching is a solid-liquid extraction method in which the process of separating solid metal waste was mixed with leaching reagent, a liquid solvent to dissolve the metal in it. The commonly used leaching reagents are strong acids such as sulfuric acid, nitric acid and hydrochloric acid.
Which toxic element is used in gold extraction?
Another method of Au extraction uses cyanide in a two-stage process; extraction and recovery. Gold is first dissolved using cyanide in the extraction stage and the dissolved gold is then recovered from the cyanide solution by cementing with zinc or adsorption onto activated carbon.
Why is gold leaching important?
It is the most commonly used leaching process for gold extraction. Production of reagents for mineral processing to recover gold represents more than 70% of cyanide consumption globally. Other metals are recovered from the process include copper, zinc, and silver, but gold is the main driver of this technology.
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.
How do you remove impurities from gold?
Chlorine Gas Method – Miller Process The unrefined gold is first melted and then a stream of pure chlorine gas is blown over it, turning the impurities into salts that are then removed.
What is gold sodium thiosulfate used in?
Gold sodium thiomalate is used for treatment of rheumatoid arthritis, a treatment with a high frequency of adverse skin reactions.
How do you make thiosulfate?
Formation. Thiosulfate is produced by the reaction of sulfite ion with elemental sulfur, and by incomplete oxidation of sulfides (pyrite oxidation), sodium thiosulfate can be formed by disproportionation of sulfur dissolving in sodium hydroxide (similar to phosphorus).
How do you extract gold without 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. It’s safe and lowers environmental impacts.
Which microorganism is involved in gold leaching?
Two cyanogenic bacteria, i.e., P. aeruginosa and B. megaterium, were used by Gorji et al. (2020) for the bioleaching of gold from pure gold particles and an oxidized gold-bearing ore (6.2 g/ton gold) prepared from the Kalchuyeh mine located in Isfahan, Iran.
How does pH affect gold leaching?
3.5 Effect of pH Value Jeffrey et al. (2008a,b) observed that increasing the pH value from 8.5 to 10.5 increased the gold leaching efficiency from 7% to 70% from a pressure-leach residue of a refractory gold ore after 1 h in 50 mmol/L (NH4)2S2O3 and 0.5–2 mmol/L CuSO4.