Cyanidation is one of the main gold extraction technologies, which mainly contains cyanidation leaching process and precipitation extraction process. Cyanidation leaching process is an key point influencing the gold recovery rate, and the leaching process is complex. There are many technology indexes are involved in the leaching process. Therefore, the strict leaching process experiment is needed to determine the indexes to get a higher recovery rate under the condition maintaining the whole cost of mineral processing plant.
So what are the aspects involving in the leaching process experiment? The experiment test items are similar with the factors influencing gold leaching.
Use the table of contents below to navigate through the guide:
Gold monomer separation or bare gold surface is the essential factor of cyanidation leaching process, while the grinding grain size is the key point influencing the mineral monomer dissociation. The smaller grinding grain size is, the larger specific surface area of ore sample is, so is the contact area with leaching agent. The leaching agent can easily dissolve the metal minerals, thus the leaching efficiency is encouraged. It needs to pay attention that excessive pursuit of small grinding particle size can lead to over grinding. It not only increases grinding costs and the possibility of mixing impurities, but also causes difficulties in solid-liquid separation and the loss of cyanide and molten gold. The grinding particle size is determined by leaching process experiment in further way.
Extraction time is an important factor influencing the gold leaching process. The cyanidation leaching process need to make sure the suitable extraction time. If the extraction time is too short, gold can’t fully dissolve; while if the extraction time is too long, not only do larger processing facilities and sites need to be deployed, but other impurities in the pulp also continue to dissolve, preventing the dissolution of gold. The suitable extraction time should be determined by the leaching process experiment, to increase the leaching efficiency and reduce the costs.
CN- is not stable in the solution, which easily create HCN gas volatilization and the loss of HCN. The lime is added as the protective alkali to maintain the pH of pulp. The lime can avoid the cyanide volatilization in solution. It also promote the precipitation of Fe3+ into Fe(OH)3, avoid the consumption of cyanide. The lime dosage test is essential to determine the lime agent.
The pulp density test directly influences the gold leaching speed and leaching rate. The higher pulp density is, the higher pulp viscosity is, the weaker the liquidity is, thus the smaller gold leaching speed and gold leaching rate are. On the other hand, the lower pulp concentration is, the better liquidity is. The gold leaching is higher and so is the agent dosage and volume of equipment and investment cost. Therefore, to balance the gold leaching rate and production cost, it need to determine the suitable pulp concentration.
Oxidation pretreatment with oxidant can effectively improve the recovery rate of cyanide leaching. The gold leaching process needs the pretreatment agent selection test. The pretreatment agent includes calcium peroxide, sodium hypochlorite, sodium peroxide, hydrogen peroxide, citric acid, lead nitrate, etc. In general, the leaching effect after pretreatment is compared with that without pretreatment under normal conditions. The purpose is to determine whether a pretreatment job is required.
In the cyanidation leaching process, the dosage of cyanide and the gold leaching rate is in proportional relation in a certain scope. If the cyanide is overdosed, increasing the cost while the gold leaching rate is nearly the same. At the same time, the adding method also influencing the gold leaching rate and leaching speed. Therefore, on the basis of grinding fineness test, in order to further reduce the dosage of cyanidation agent and the production cost, and to determine the addition method of cyanidation agent, the dosage and addition method of cyanidation agent should be tested.
The above is the aspects of gold leaching process experiment. We command you to carry out the mineral processing experiment entrusting the manufacturers with mineral processing plant construction qualification, making sure the indexes in leaching process according to different characteristic of ores to reach a higher recovery rate of investment.