Non-toxic and environmentally-friendly gold-selecting agent

Gold extraction process CIP process is one cyanidation process. It is a process of carbon adsorption of monovalent gold cyanide [KAu(CN)2] after completion of cyanidation leaching of gold-containing materials. It has long been found that activated carbon can adsorb the characteristics of precious metals from a solution, and initially only adsorbs gold from the supernatant, and smelts the gold-bearing charcoal to recover gold. Since cyanide pulp has to be separated by solid-liquid separation to obtain a clear liquid and activated carbon cannot be returned, this method cannot be industrially competitive with the widely used zinc substitution method. Later, activated carbon adsorption of pulp from low gold, thus eliminating the need for solid-liquid separation operations; gold loaded activated carbon desorption mixture was neutralized with sodium hydroxide and sodium cyanide gold and silver, the process may return the activated charcoal used. Therefore, in recent years, the development of carbon slurry has become a new process for gold extraction. China has built a production plant using the carbon slurry process in the Linghu Gold Mine in Henan Province and the Chiweigou Gold Mine in Jilin Province.

The carbon slurry process includes the main operations such as raw material preparation and activated carbon regeneration. The process flow is shown in Figure 8-2.

Carbon slurry

(1) Preparation of raw materials

Grinding the gold-containing material to a suitable cyanide particle size, generally requiring less than 28 mesh and removing impurities such as wood chips, and concentration and dehydration to achieve a concentration of 45 to 50% of the leaching slurry;

(2) Stirring leaching

As with the conventional cyanidation method, it is generally 5 to 8 stirring tanks.

(3) Carbon adsorption

The cyanide slurry enters the agitation adsorption tank (carbon slurry tank). The Linghu gold mine in Henan Province is equipped with a format sieve and a slurry riser in the suction slag, which is used to realize the reverse flow of the activated carbon and the slurry, and adsorb the dissolved gold in the slurry. Bridge screens reduce the wear of activated carbon. At present, the sieve holes of the bridge sieve are easily blocked by activated carbon, and are cleaned with compressed air.

(4) Desorption of gold-loaded charcoal

At present, four methods can be used for desorption; (1) desorption of hot caustic sodium cyanide solution; (2) desorption of sodium caustic cyanide solution plus alcohol desorption; (3) desorption with caustic sodium cyanide solution under heating and pressure; (4) Desorption of high concentration caustic sodium cyanide solution.

(5) Electrowinning method or conventional zinc powder replacement precipitation gold

Desorption of gold-loaded carbon can obtain a high-grade noble liquid containing gold up to 600 g/m3, and gold powder is obtained by electrowinning and zinc replacement, and sent to obtain a gold ingot.

(6) Recycling of activated carbon

The desorbed activated carbon is first acid washed with dilute sulfuric acid (nitric acid) to remove carbonates and the like, and after several times of use, thermal activation is required to restore the adsorption activity of the carbon.

The carbon slurry method is mainly applied to gold-bearing oxidized ore with high sludge content. The ore is high in mud and difficult to separate solid and liquid. The existing filter can not effectively separate the precious liquid and the slag, so the conventional cyanidation method cannot Get better technical and economic indicators. Practice shows that the carbon slurry method has achieved good results in industrial production. The gold content of Linghu Gold Mine is about 8 g/ton, and the total recovery rate of gold is 93%~94%.

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