Gold leaching is an important gold beneficiation process. It uses specific chemical reagents to dissolve the gold in the ore to form a gold-containing solution, and then extracts the gold from the solution through further processing methods. The gold leaching process has the characteristics of high efficiency and good selectivity. It can extract gold from low-grade ores and improve the utilization rate of gold resources.
During the leaching process, the efficiency of gold leaching is affected by many factors, which can be mainly divided into four categories, namely ore properties, leaching reagents, leaching conditions and stirring intensity. Let's learn about these influencing factors together.
The physical and chemical properties of the ore have a significant impact on the gold leaching efficiency, including ore type, particle size, grade and mineral composition.
1. Ore type: Different types of ores have different effects on gold leaching. Gold in oxide ores is usually easier to leach, while gold in sulfide ores requires pretreatment before leaching; the difficulty of leaching gold in mixed ores is between oxide ores and sulfide ores.
2. Ore particle size: The effect of ore particle size on gold leaching is mainly manifested in two aspects. On the one hand, the smaller the ore particle size, the larger the contact area between gold and leaching reagents, and the faster the leaching speed; on the other hand, the smaller the ore particle size, the greater the viscosity of the ore pulp, which affects the diffusion and mass transfer of the leaching reagents, thereby reducing the leaching speed.
3. Ore grade: The effect of ore grade on gold leaching is mainly manifested in the amount of leaching reagents and the leaching time. The higher the ore grade, the less leaching reagents are required and the shorter the leaching time. On the contrary, the lower the ore grade, the more leaching reagents are needed and the longer the leaching time.
4. Mineral composition: The mineral composition of the ore also has a great influence on gold leaching. Some minerals such as pyrite, arsenopyrite, etc. will react with the leaching reagents, consume the leaching reagents, and thus reduce the leaching rate of gold. In addition, some minerals such as quartz and feldspar will adsorb the leaching reagents, affecting the diffusion and mass transfer of the leaching reagents, thereby reducing the leaching rate.
During the gold leaching process, the reagent undergoes a specific chemical reaction with gold, and then dissolves the gold from the ore to form a gold-containing solution. The reagent has many effects on gold, including: the type of leaching reagent, concentration, pH value, etc.
1. Type of leaching reagent: Different types of leaching reagents have different effects on gold leaching. Cyanide is currently the most widely used gold leaching reagent, with fast leaching speed, good selectivity and low cost. However, cyanide is toxic and has great harm to the environment and human health. Thiourea and chloride are also commonly used gold leaching reagents, which have good leaching speed and selectivity, but high cost.
2. Concentration of leaching reagents: The effect of the concentration of leaching reagents on gold leaching is mainly reflected in the leaching speed and gold leaching rate. The higher the concentration of the leaching reagent, the faster the leaching speed and the higher the gold leaching rate. However, too high a concentration of leaching reagents will lead to increased costs and greater pollution to the environment. Generally, the cyanide concentration is controlled within the range of 0.05% to 0.1%.
3. The pH value of the leaching reagent: The pH value of the leaching reagent also has a great influence on gold leaching. Different leaching reagents have different leaching effects at different pH values. Generally speaking, the reasonable pH value of cyanide leaching is about 10, the pH value of thiourea leaching is about 1.5, and the pH value of chloride leaching is about 2. In actual production, it is necessary to select the appropriate pH value of the leaching reagent according to the type of leaching reagent and the nature of the ore.
The influence of leaching conditions on gold leaching mainly includes: leaching temperature, time and solid-liquid ratio.
1. Leaching temperature: The influence of leaching temperature on gold leaching is mainly reflected in the leaching speed and gold leaching rate. The higher the leaching temperature, the faster the leaching speed and the higher the gold leaching rate. However, too high leaching temperature will lead to decomposition and volatilization of leaching reagents, increase costs, and also cause greater pollution to the environment. Therefore, in actual production, it is necessary to select a suitable leaching temperature according to the properties of the ore and the requirements of the leaching process.
2. Leaching time: The influence of leaching time on gold leaching is mainly reflected in the gold leaching rate. The longer the leaching time, the higher the gold leaching rate. However, too long leaching time will lead to increased costs and reduce production efficiency. Therefore, in actual production, it is necessary to select a suitable leaching time according to the properties of the ore and the requirements of the leaching process.
3. Liquid-solid ratio: The liquid-solid ratio refers to the ratio of the volume of the leaching solution to the mass of the ore. The effect of liquid-solid ratio on gold leaching is mainly reflected in the leaching speed and gold leaching rate. The larger the liquid-solid ratio, the faster the leaching speed and the higher the gold leaching rate. However, too large a liquid-solid ratio will increase the amount of leaching reagents used, increase costs, and increase the difficulty of subsequent treatment. Therefore, in actual production, it is necessary to select a suitable liquid-solid ratio based on the properties of the ore and the requirements of the leaching process.
The effect of stirring intensity on gold leaching is mainly reflected in the leaching speed and gold leaching rate. The greater the stirring intensity, the faster the leaching speed and the higher the gold leaching rate. This is because stirring can make the leaching reagent fully contact with the ore, increase the diffusion and mass transfer rate of the leaching reagent, and thus speed up the leaching speed. However, excessive stirring intensity will cause the temperature of the slurry to rise, the decomposition and volatilization of the leaching reagent to accelerate, and it will also increase the wear and energy consumption of the equipment. Therefore, in actual production, it is necessary to select the appropriate stirring intensity according to the properties of the ore and the requirements of the leaching process.
In actual production, it is necessary to select the appropriate leaching reagent and leaching conditions according to the properties of the ore and the requirements of the leaching process, and control the stirring intensity to improve the efficiency of gold leaching and the leaching rate of gold, reduce production costs, and reduce pollution to the environment. Therefore, it is recommended to conduct mineral processing tests and determine the leaching conditions through test analysis.
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