Indonesia 100tpd Gold Extraction Project

5 Factors Affecting Gold Extraction Efficiency by Cyanide

2022-08-08 XinHai Views (74)

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When the all-slime cyanidation method is used to treat gold ore with a high degree of oxidation, there are many influencing factors. Among them, there are main five factors. They are the grinding particle size, the amount of sodium cyanide, the amount of lime, the concentration of leaching pulp and the leaching time. From the article, you can know the effects of these five factors on the gold extraction efficiency with finely embedded and encapsulated natural gold by cyanidation.

100m² xinhai pregnant liquid purification tank

01Grinding particle size of gold ore

Before all-slime cyanidation gold extraction, gold ore needs to be pretreated, that is, crushing, screening, grinding and grading. Pretreatment can separate gold from gangue minerals as much as possible, so as to achieve monomer dissociation of concentrate. It is also a necessary condition for cyanide leaching. In the pretreatment, the grinding operation is the key process to realize the dissociation of gold monomer. "More crushing and less grinding" is the principle that the concentrator has always adhered to. Once over-ground, in addition to increasing the cost of grinding consumption, it will also increase the risk of leachable impurities mixing into the leachate. At the same time, overgrinding will hinder the solid-liquid separation, resulting in the waste of cyanide and the loss of dissolved gold. When the gold ore with fine embedded and encapsulated natural gold particle size is used, the grinding particle size is -38 μm and the content ratio is 75%, which can ensure better leaching effect and grinding cost.

filter used in gold leaching

02Lime amount used in gold ore cyanidation leaching

A certain amount of sodium cyanide solution will be added during the all-slime cyanidation test. Due to the unstable chemical properties of cyanide ions in solution, it is easy to become hydrogen cyanide gas and volatilize, resulting in the loss of sodium cyanide solution. Therefore, a certain amount of lime needs to be added to the cyanide solution. Lime is added to the cyanidation solution as a protective alkali to keep the pulp at a suitable alkalinity. According to the test analysis, the leaching rate of gold is also greatly improved after adding lime. When the amount of lime added is 2kg/t and above, the pH value of the pulp is between 11-12, and the leaching rate of gold in the pulp is close.

desorption column used in gold leaching

03Sodium cyanide dosage used in gold leaching

Within a certain range, the amount of cyanide is proportional to the leaching rate of gold ore pulp. Too much or too little cyanide will affect the leaching efficiency. When the cyanide content is low, the gold leaching effect is not good and the speed is slow, resulting in a certain time cost. However, when the amount of cyanide is too much, after the leaching efficiency of gold reaches a certain level, the change will not be obvious, so it will cause waste of cyanide and increase the production cost. In order to reduce the amount of cyanide and the cost of production chemicals, and at the same time ensure the leaching efficiency, it is critical to add an appropriate amount of sodium cyanide solution. When extracting gold concentrate from gold ore with finely embedded particle size, the dosage of sodium cyanide is more suitable at 1.5-3.0kg/t. In actual production, the concentrator also needs to determine the amount of sodium cyanide according to the characteristics of its own ore and beneficiation tests.

desorption electrolysis system designed by xinhai

04Slurry concentration during gold ore cyanidation leaching 

Slurry concentration is a factor that directly affects the leaching speed and efficiency of gold concentrate. In general, when the concentration of the leaching pulp is low and the fluidity is good, the leaching efficiency of the gold concentrate will be higher. However, this situation will require an increase in the amount of the added agent, and at the same time, the size of the equipment and the investment cost will also increase. In order to balance the gold leaching efficiency and production cost, it is necessary to determine the appropriate slurry concentration. For gold ore with finely embedded particle size, the pulp concentration can be maintained at about 20%-33% to ensure a good leaching effect. If it is higher than this range, the leaching efficiency of gold will not increase but decrease. In actual production, the concentrator can appropriately adjust the concentration according to the specific situation, but it should not be too high.

Cyanidation equipment manufactured by xinhai

05Gold ore cyanide leaching time

The leaching time is also one of the important factors affecting the leaching efficiency in the cyanidation process. Selecting the appropriate leaching time can fully dissolve the gold particles. While dissolving gold particles, other impurities in the pulp will also continue to dissolve, thus affecting the speed of gold dissolving. The prolongation of leaching time is not only unfavorable for the dissolution of gold particles, but also requires the configuration of larger leaching equipment and sites, thereby increasing production costs. Therefore, it is also important to determine a suitable gold leaching time. For gold ore with fine embedded particle size, it is better to keep the cyanidation leaching time at about 4 hours. If the leaching time is more than 24 hours, the leaching of gold is inhibited, and the gold ion concentration in the precious liquid also decreases. Therefore, a suitable leaching time not only improves the leaching efficiency, but also reduces the time cost of production to a certain extent.

Desorption Electrowinning System

The above are the five factors that affect the cyanidation leaching efficiency. The above data is for reference only. Concentrators can conduct ore beneficiation tests to determine the properties and characteristics of their own ore before leaching gold ore. In this way, factors such as the appropriate dosage of chemicals, leaching time, and grinding particle size can be judged. In addition to the above five factors, there are other factors that may affect the cyanidation leaching efficiency. Xinhai has more than 20 years of experience in beneficiation process design and equipment production. You can consult us for more precautions about the gold cyanation process.

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