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The surface of gold monomer dissociated or exposed gold is a necessary condition for gold leaching with environmental gold dressing agent. Therefore, appropriately increasing the fineness of the grinding can increase the leaching rate of gold. However, over-grinding not only increases the grinding cost, but also increases the possibility that the impregnable impurities enter the environmental gold dressing agent, resulting in the loss of cyanide or environmental gold dressing agent and dissolved gold. In order to determine the appropriate grinding fineness, the grinding fineness test must be carried out first.
The pretreatment agent selection test is necessary for gold leaching process, it usually requires the use of conventional pretreatment agents such as calcium peroxide, sodium hypochlorite, sodium peroxide, hydrogen peroxide, citric acid, and lead nitrate. Pretreatment is added for comparison to determine if a pretreatment is required.
Calcium peroxide, sodium hypochlorite and sodium peroxide are all very stable and widely used multi-functional inorganic peroxides, and have the characteristics of long-term oxygen release. In the leaching pulp, oxygen can be slowly released for a long time, which is beneficial to increase the leaching rate of gold.
Hydrogen peroxide and citric acid provide sufficient oxygen during leaching, which is the main reagent for oxygen generation. Lead ion of lead nitrate (appropriate amount) can destroy the gold passivation film during cyanide leaching process, accelerate the dissolution rate of gold and reduce the cyanidation time, increases the leaching rate of gold.
In order to protect the stability of the environmental gold dressing agent solution and reduce the loss of the chemical, an appropriate amount of alkali must be added in the leaching agent to maintain the pulp with a certain alkalinity.
The alkalinity is within a certain range. With the increase of alkali concentration, the gold leaching rate is constant, and the dosage of environmental gold dressing agent is correspondingly reduced. If the alkalinity is too high, the dissolution rate and leaching rate of gold decrease. It is necessary to determine the appropriate amount of protective alkali and the pH of the pulp. Tests and production usually use lime, which is widely sourced and inexpensive, as a leaching protection base. In order to determine its specific usage, it provides guidance for actual production.
In gold leaching process, the amount of environmental gold dressing agent and gold leaching rate are proportional to a certain range. When the amount of environmental gold dressing agent is too high, the production cost is increased, but the leaching rate of gold doesn’t increase.
To this end, on the basis of the grinding fineness test, in order to further reduce the environmental gold dressing agent dosage and production agent cost, an environmental gold dressing agent dosage test is conducted to determine an appropriate dosage.
In order to achieve high leaching rate during the leaching process, the leaching time can be extended to fully dissolve the gold particles to increase the gold leaching rate. As the leaching time is prolonged, the gold leaching rate is gradually increased, and finally reaches a stable value. However, the leaching time is too long, and other impurities in the slurry are continuously dissolved and accumulated, which hinders the dissolution of gold. When using an environmental gold dressing agent for gold leaching, a leaching time test is performed to determine the appropriate leaching time.
When leaching gold with environmental gold dressing agent, the concentration of slurry directly affects the leaching rate and leaching speed of gold. The higher the concentration, the higher the viscosity of the slurry, the lower the fluidity, and the lower the leaching rate of gold. When the concentration of the slurry is too low, although the leaching speed and leaching rate of gold are high, it will increase the equipment volume and equipment investment, and will also increase the dosage of environmental gold dressing agent and the corresponding production cost. Therefore, in order to determine the appropriate leaching slurry concentration, a leaching slurry concentration test is performed.
For CIL gold process, hard and wear-resistant activated carbon must be used to avoid the generation of fine-grained carbon into the leaching residue during the agitation leaching process, resulting in loss of gold and reduced gold recovery. The test generally uses coconut shell activated carbon with a particle size ranging from 6 to 40 mesh. The activated carbon was pretreated under the conditions of water: carbon = 5:1, stirred for 4 hours, and the stirring speed was 1700 rpm. The activated carbon after stirring for 4 hours was sieved with a 6 mesh and 16 mesh sieve. The fine carbon under the sieve is removed. That is, carbon dioxide leaching and carbon adsorption tests are carried out using activated carbon with a particle size of 6 ~ 16 mesh.
In the gold ore leaching test using environmental gold dressing agent, it is generally determined to use 6-16 mesh coconut shell activated carbon to adsorb and recover the leached gold. After the carbons loaded with gold is produced, the mature activated carbon is used for analysis and electrolytic gold. The density of the bottom carbon directly affects the carbon adsorption rate. For the choice of the appropriate bottom carbon density, the bottom carbon density test will be carried out.
In order to determine the appropriate carbon adsorption time and reduce the consumption of gold-loaded carbon, it is necessary to carry out pre-leaching and carbon adsorption time test after determining the total leaching time of gold leaching process.
In order to verify the stability of the carbon leaching test and the repeatability of the test results, it is necessary to carry out the parallel test of the whole process comprehensive conditions of the carbon leaching test, that is, after determining the above nine detailed condition tests, a comprehensive verification test of the optimal conditions for each final condition test is required.
In summary, before using environmental gold dressing agent for gold ore leaching, it must first pass the grinding fineness test, pretreatment agent selection test, protection of alkali lime dosage test, environmental gold dressing agent dosage test, leaching time test, slurry concentration test, activated carbon pretreatment test, bottom carbon density test, carbon adsorption time test and carbon leaching process comprehensive conditions parallel test, finally determine a complete carbon slurry leaching gold ore test ore dressing process test study. In addition, sometimes the carbon leaching process tail water (lean liquid) return utilization test and carbon slag sedimentation rate measurement will be carried out according to the actual production needs.