Cyanide Research Paper
Extraction of gold from ore using cyanide.
Before cyanide was used in extracting gold the recovery rate of gold was low. Cyanide was first used worldwide at the Crown Mine at Karangahake near Waihi in 1889. In the next three years six more plants were created on The Coromandel. Cyanide has been used all over the world to make the extraction of gold easier. Although cyanide is helpful in terms of recovering gold it has been used throughout history as a deadly poison. Hydrogen cyanide has been used to disinfect buildings and sodium cyanide was used for over 50 years to control coyote numbers in the US.
Cyanide is an ion with a single negative charge formed between carbon and nitrogen. There is a triple bond formed between the carbon and nitrogen. …show more content…
To do this the gold needs to be made into a soluble form so that it is easier to separate. Gold itself is insoluble so to make it soluble sodium cyanide is added (NaCN). The cyanide ion the forms a complex ion with the gold and has the formula [Au(CN)2]⁻. Cyanide is used as it quickly forms this soluble complex with the gold and has been used this way for many years.
How is the gold processed?
The first step is to crush and grind the ore, this may lead to finding any free gold which may go through a gravity recovery process as the gold could be too big to dissolve quickly with the cyanide. Once the ore has been crushed and the aqueous sodium cyanide gets added in a process known as leaching. The cyanide and gold react to form a gold cyanide soluble complex ion which is know as Elsener's equation.
4Au + 8CN⁻ + O2 + 2H2O ⇌ 4[Au(CN)2]⁻ + 4OH⁻
The gold in this form is now soluble. Oxygen is added in the form of dissolved oxygen. This oxygen is also added because it oxidises some of the possible cyanide left over. Sodium cyanide has lime added to it so that the pH is now about 10-11. This is due to the cyanide ion/hydrogen cyanide equilibrium CN⁻ (aq) + H20 ⇌ HCN (aq) + OH⁻ (aq). This ensures that the cyanide ion is not converted to hydrogen cyanide in the hydrogen cyanide
Before cyanide was used in extracting gold the recovery rate of gold was low. Cyanide was first used worldwide at the Crown Mine at Karangahake near Waihi in 1889. In the next three years six more plants were created on The Coromandel. Cyanide has been used all over the world to make the extraction of gold easier. Although cyanide is helpful in terms of recovering gold it has been used throughout history as a deadly poison. Hydrogen cyanide has been used to disinfect buildings and sodium cyanide was used for over 50 years to control coyote numbers in the US.
Cyanide is an ion with a single negative charge formed between carbon and nitrogen. There is a triple bond formed between the carbon and nitrogen. …show more content…
To do this the gold needs to be made into a soluble form so that it is easier to separate. Gold itself is insoluble so to make it soluble sodium cyanide is added (NaCN). The cyanide ion the forms a complex ion with the gold and has the formula [Au(CN)2]⁻. Cyanide is used as it quickly forms this soluble complex with the gold and has been used this way for many years.
How is the gold processed?
The first step is to crush and grind the ore, this may lead to finding any free gold which may go through a gravity recovery process as the gold could be too big to dissolve quickly with the cyanide. Once the ore has been crushed and the aqueous sodium cyanide gets added in a process known as leaching. The cyanide and gold react to form a gold cyanide soluble complex ion which is know as Elsener's equation.
4Au + 8CN⁻ + O2 + 2H2O ⇌ 4[Au(CN)2]⁻ + 4OH⁻
The gold in this form is now soluble. Oxygen is added in the form of dissolved oxygen. This oxygen is also added because it oxidises some of the possible cyanide left over. Sodium cyanide has lime added to it so that the pH is now about 10-11. This is due to the cyanide ion/hydrogen cyanide equilibrium CN⁻ (aq) + H20 ⇌ HCN (aq) + OH⁻ (aq). This ensures that the cyanide ion is not converted to hydrogen cyanide in the hydrogen cyanide