Gold cyanide leaching

Cyanide gold extraction is one of the main methods for extracting gold from gold ore. The explanation of the mechanism of cyanide on the dissolution of gold is still inconsistent. Most people think that gold can form a gold complex in the presence of oxygen in cyanide solution and dissolve it. The basic reaction formula is: 4Au+8KCN+O 2 + 2H 2 O-4KAu(CN) 2 +4KOH

The surface of the gold gradually dissolves in the cyanide solution from the surface and the inside. The concentration of oxygen in the solution is related to the dissolution rate of gold. The concentration of cyanide during leaching is generally more than 15 parts per million, and the dissolution rate of gold rises linearly to the maximum with increasing cyanide concentration. Then slowly rise, when the cyanide concentration is reached, the dissolution rate of gold is independent of the cyanide concentration, and even decreases. Reasonable cyanide concentration should be guided by the test results to ensure maximum benefits!

The dissolution rate of gold increases with increasing oxygen concentration, and the dissolution of gold can be enhanced by oxygen-enriched or high-pressure aerated cyanidation. Ability to dissolve gold and silver cyanide as reagent: ammonium cyanide> sodium cyanide, calcium cyanide> potassium cyanide. Potassium cyanide is the most expensive, and most of it currently uses sodium cyanide.

The nature of the material affects the leaching rate of gold. Although cyanidation is the main method of extracting gold, gold-bearing ore, but some material not directly employed cyanidation process, if the copper in the ore, arsenic, antimony, bismuth, sulfur, phosphorus, a magnetic iron ore, iron ore and other white When the content of the component is high, the cyanide consumption is greatly increased to consume oxygen in the slurry. When the leaching rate of gold is lowered, when carbon is high in the ore, carbon will adsorb dissolved gold and lose with tailings. Pre-oxidation roasting or flotation methods remove the effects of harmful impurities. The cyanide hydrolysis reaction is: KCN+H 2 OyKOH+HCN will therefore volatilize toxic HCN; the addition of lime reduces the hydrolysis of cyanide, and the above reaction proceeds to the left, reducing the loss of cyanide. Lime also neutralizes the action of acid substances and can precipitate harmful ions in the slurry, so that the dissolution of gold is in the best condition, and lime is commonly used as a protective base. The amount of lime added is such that the pulp value is 11 to 12, and the pulp lang=EN-value is too high to be unfavorable for the gold. The size of the gold particles mainly affects the cyanide time, and the dissolution rate of the crude gold (>74 microns) is slow. Therefore, it is reasonable to pre-recover coarse gold by amalgamation , re-election or flotation before cyanidation. Dissociation of fine gold particles from the monomer during the grinding process is still an important factor in increasing the leaching rate of gold.

The clay content and slurry concentration during cyanidation directly affect the diffusion rate of the components. The pulp concentration should be less than 40%. The concentration of slurry in the mud should be less than 30%, but the concentration should not be too low, otherwise the consumption of cyanide will increase, and the leaching time will be shortened, resulting in an increase in production cost. Because general mines use zero emission standards, high cyanide leaching is not good for future production.

The cyanide time varies depending on the nature of the material, the cyanidation mode and the cyanide conditions. Usually stirring time is cyanide leaching often greater than 24 hours, usually about 48 hours, 72 hours required when tellurium cyanide, cyanide leaching diafiltration required more than five days. Some mines now employ reasonable concentrate was triturated using expensive grinding Abandon mechanical agitation with air agitation leaching, transporting slurry with air lift, will shorten the leaching time and greatly improve the leaching rate.

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Shangqiu Sihai Energy Technology Co., Ltd ,