What Are the Processes for Cyanide Leaching Gold Extraction?

01Gold extraction by activated carbon adsorption

The gold extraction process by activated carbon adsorption is to make the gold ions adsorbed by activated carbon by contacting the cyanide leaching solution with activated carbon. Usually, carbon-in-place (CIP) or carbon-in-place (CIL) is used. The former is to first cyanide leaching the ore, and then add activated carbon to the leaching solution for adsorption; the latter is to add activated carbon for adsorption while cyanide leaching. The gold-loaded carbon after adsorption is recovered by desorption, electrolysis or replacement.

Desorption generally uses a mixed solution of sodium hydroxide and sodium cyanide to desorb gold from activated carbon at a certain temperature and pressure to form a gold-rich desorption solution, which is then electrolytically deposited or replaced with zinc powder to obtain gold mud. Finally, the gold mud is refined to obtain high-purity gold. This gold extraction method has a good adsorption effect on various gold mine cyanide leaching solutions, and is simple to operate and easy to realize automatic control. The activated carbon can be recycled. However, activated carbon also has a certain adsorption capacity for impurities, which may affect the purity of gold.

02Gold extraction with ion exchange resin

Gold extraction with ion exchange resin is to select ion exchange resin with selective adsorption capacity for gold ions, add it to the cyanide leaching solution, so that the gold ions exchange with the active groups on the resin and are adsorbed. The adsorption saturated resin is eluted, and the gold ions are eluted from the resin using a specific eluent to form a gold-rich eluent. The gold-rich eluent is further treated, such as electrolysis or displacement, to obtain gold mud, which is then refined. This gold extraction process has high selectivity and the resin has a fast adsorption and desorption rate. However, the price of the resin is relatively high, and there are certain requirements for the pH value and impurity content of the leachate during adsorption.

03Solvent extraction for gold extraction

Solvent extraction is the process of gold extraction from cyanide leaching solution into organic phase by using organic solvent to selectively extract gold ions. The organic phase after extraction is stripped, and gold is stripped from organic phase into aqueous phase using acid solution or other stripping agent to form gold-rich stripping solution. The gold-rich stripping solution is then subjected to subsequent treatment, such as electrowinning or displacement, to obtain gold mud, which is then refined. At present, commonly used extractants are amines and phosphines, which have high selectivity for gold and can effectively separate gold from other impurities. However, the price of the extractant is relatively high, and the extraction and stripping processes have high requirements for temperature, pH value, etc.

04Zinc powder replacement gold extraction

Zinc powder replacement is to directly add zinc powder to the cyanide leaching solution, and the gold ions and zinc powder undergo a replacement reaction to generate gold and zinc ions, and the gold precipitates to form gold mud. The gold mud is then filtered, washed, impurities removed, and refined. This gold extraction method is simple, easy to operate, has a fast replacement reaction speed, and is low in cost, but the consumption of zinc powder is large and the purity of the leaching solution is required to be high.

In summary, various processes for gold extraction from cyanide leaching solution have their advantages and disadvantages. In practical applications, it is necessary to comprehensively consider factors such as ore properties, production scale, and cost requirements to select the appropriate gold extraction process. At the same time, with the continuous advancement of technology, new gold extraction processes are constantly emerging, providing more options for gold production.