Effect of activated carbon Properties on carbon adsorption i
2020-08-14 15:16Introduction：Effect of activated carbon Properties on carbon adsorption in Gold Mine carbon slurry process Different kinds of activated carbon have different micropore structures due to their different raw materials and activation methods, which show t
Effect of activated carbon Properties on carbon adsorption in Gold Mine carbon slurry process
Different kinds of activated carbon have different micropore structures due to their different raw materials and activation methods, which show that there are also great differences in the properties related to the adsorption of gold. Therefore, what kind of activated carbon is used as adsorbent of carbon slurry process is related to the technical and economic index of the whole carbon slurry process.
1.The influence of adsorption ability of carbon
The adsorption capacity of activated carbon for gold includes adsorption capacity and adsorption rate. Adsorption capacity determines the amount of activated carbon used in production and the scale and operation requirements of gold recovery system. The carbon with large adsorption capacity needs less carbon to reach the same production target, and the concentration of activated carbon in the adsorption system can be controlled less, which is conducive to the smooth flow of carbon adsorption system and reduces the loss of carbon and metal. In addition, the high adsorption capacity of the carbon can be controlled higher grade of gold-loaded carbon, so the desorption equipment can be designed to be smaller. The length of adsorption process depends on the adsorption rate of activated carbon. It is generally believed that the adsorption rate of carbon is a more important activity index than adsorption capacity.
In actual production, activated carbon is usually used to determine the adsorption capacity and adsorption rate according to the specified items, and then to determine the variety of carbon, which is a commonly used and more reliable method at present. Determination of the relative adsorption efficiency of activated carbon can also be used to evaluate the relative adsorption capacity of various activated carbon. The so-called relative adsorption efficiency is the ratio of the experimental carbon quantity to the reference carbon quantity when the concentration of tailing solution is reduced to a certain value by adsorption from a solution containing a certain concentration of Au(CN)2-.The results show that the adsorption ability of various activated carbon to Au(CN)2- is very different. The adsorption characteristics of Coconut shell charcoal and apricot shell charcoal were much better than those of coal coke and activated carbon.
2.Influence of carbon strength
As mentioned earlier, strength is one of the important indexes to evaluate the properties of activated carbon. The strength is closely related to the activity of carbon. The activated carbon with lower adsorption capacity generally has a higher strength, and this kind of carbon often shows great anti-wear ability in the process flow of carbon slurry, which makes the activated carbon keep a low loss under the strong impact and grinding action. In the process of carbon slurry, the amount of gold loaded by activated carbon increases with the increasing of carbon particles. Activated carbon, which is worn out, is easy to pass through the sieve and run off with the tailings. This is not only a loss of carbon, but also a large amount of gold and silver adsorbed on it. Therefore, reducing the loss of activated carbon by every possible means is a long-term important work in the process management of carbon slurry. Firstly, when selecting activated carbon, the properties of carbon should not be simply evaluated according to its adsorption ability, but the strength of carbon should be paid more attention to, so that the wear of carbon and the loss of metal can be reduced to a minimum. Secondly, in order to prevent the loss of fine carbon with tailings, a screen is usually equipped after the adsorption system, which is called safe screen, and its function is to recover the fine carbon lost from the adsorption system. The size of the sieve hole of the safety screen is always smaller than that of the interstage sieve, but it must be proved that the slurry can pass smoothly. In spite of this, a small amount of fine charcoal will be removed from the sieve. Some charcoal pulp plants install two-stage safety sieves to recover more fine carbon. Third, efforts to reduce the loss of activated carbon should not be confined to the adsorption system, but throughout the whole process.
3.Effect of carbon particle size
The technology of extracting gold from carbon slurry has strict requirements on the granularity of activated carbon. In theory, the larger the size of the activated carbon, the smaller the size of the activated carbon, the lower the specific surface area, the lower the activity and the worse the adsorption efficiency. On the contrary, the smaller active carbon is relatively larger than the surface area, and the activity is higher and the adsorption capacity is stronger. Most of the fine granular activated carbon in the production is worn down from the coarse carbon. As mentioned earlier, this part of carbon has the characteristics of high activity and low strength, which will continue to wear out in the process and easily drain with the tailings. In process, the activated carbon is reverse flow with the pulp. This flow mode depends on the sieves and the carbon extraction equipment. The fine grain is easy to plug the sieve, and the flow is not smooth. When the granular carbon passes through the carbon extraction equipment and pipeline, the wear amount is relatively large.
In order to achieve good adsorption effect, carbon must be in full contact with pulp. If the carbon particle size is not uniform, it is easy to segregate in the slurry, which will seriously affect the uniformity of the char string, make the contact time between the different sizes of carbon and the pulp uneven, and reduce the adsorption effect. Therefore, the granularity of activated carbon for gold extraction should not be too large or too small, and should be as uniform as possible. General purpose activated carbon granularity is 6~16 mesh in production,the content of activated carbon in the upper and lower sieve level is less than 3%.
In order to ensure the particle size characteristics of the carbon , the fine carbon recovered from the safety screen should not be returned to the carbon adsorption system . The regenerated carbon contains a large amount of fine carbon , and the regenerated carbon must be screened out before the regeneration charcoal is added to the adsorption system .
