First, the basic principle and principle process of gold amalgamation ?
Mercury amalgamation is a simple and ancient method. It is based on the principle that gold particles are easily wetted by mercury, and mercury is then diffused into the gold particles to form gold amalgam (including amalgam). The amalgamation reaction can be expressed by the following formula:
Au +2Hg = AuHg2
The composition of gold amalgam (paste) varies with its gold content. When the mercury is mixed, the surface of the gold particles is first wetted by mercury, and then the mercury diffuses into the interior of the gold particles to form AuHg2, AuAg, Au3Hg, and finally forms the solid solution Au3Hg in the mercury. When the mercury paste is heated to above 375 degrees, the mercury volatilizes in the form of elemental mercury, and the gold exists in the form of sponge gold.
Mercury amalgamation is generally not an independent process and often forms a joint process with other methods of separation. In most cases, amalgamation is only an aid to recovery. Due to the poor working conditions of mercury operation, the labor intensity is high, it is easy to cause mercury poisoning, and the waste water containing mercury should be purified. It is gradually being replaced by flotation or re-election. However, the amalgamation method can recover the natural gold of the monomer, which can be used as a real estate gold, so it still occupies a certain position in the gold beneficiation .
Second, the recovery rate of gold extraction by mercury amalgamation depends on what factors?
The recovery rate of gold during amalgamation depends on the particle size of natural gold, the color of gold particles, the quality of mercury, the temperature of amalgamation, the concentration of slurry, the way of mercury mixing, the slope of mercury plate and equipment factors.
The particle size shape and monomer dissociation degree of gold are mainly related to the grinding operation, especially the influence of monomer dissociation degree. Appropriately improving the fineness of grinding can improve the recovery rate of amalgamation, and it is suitable for gold particles mixed with mercury. It is 0. 2-0. 3 mm, the lower limit of the particle size of the mercury-mixing plate in the grinding cycle is 0. 015 mm, but the fine gold particles are lost with the slurry.
The color of gold is higher than that of pulse gold. The gold color in the oxidation zone is higher than that of the original ore. The gold with high color is easy to mix with mercury. The amalgamation ability of the gold particle surface is significantly reduced. Mercury is divided into internal amalgamation and external amalgamation. External amalgamation is a process of amalgamation and gold extraction outside the crushing mill. Externally mixed mercury is commonly used in domestic fixed mercury amalgamation plates and vibrating amalgamation plates. In the process of crushing and grinding, the gold and gold extraction process is carried out in South Africa and the United States. The gold mines in South Africa and the United States often carry out internal amalgamation in the mining machine. The small and medium-sized gold mines in the Soviet Union often use the smashing machine. Internally mixed mercury is more efficient than externally mixed mercury, and the quality of mercury is good. The concentration of the externally mixed mercury slurry should not be too large to form a loose thin slurry flow, and the flow rate should not be too high, so that the gold particles settle to the mercury plate. The concentration of the internal mixed mercury slurry is preferably 30-50%, and the mercury should be suspended.
The pH of the slurry has a great influence on the mercury mixing effect. The effect of mixing mercury in the acidic medium and the cyanide solution is good, but in the case of a large amount of slime, the acidic medium cannot aggregate the slime, and the slime contaminates the surface of the gold particles, affecting the effect of mercury mixing. Mercury is mixed in an alkaline medium, such as the use of lime as a conditioning agent to precipitate soluble salts and eliminate the adverse effects of oil quality. When PH=8-8. 5, the effect of mixing mercury is better.
The quality of mercury has a great influence on the effect of mercury amalgamation. Pure mercury is not good for the wetting of gold. Mercury contains a small amount of gold, silver and strontium metal to reduce the surface tension of mercury and improve the wetting effect. Oil and other organics can contaminate soil and fine gold particle surface, ore sulfide ore, talc, graphite, arsenic compounds easily attached to the surface of the mercury, mercury also affects wetting ability of gold. Ccc
When adding mercury, the amount of mercury should be increased. Too much will reduce the elasticity and consistency of the mercury paste, so that the mercury paste will be lost with the slurry. Insufficient mercury addition makes the mercury paste hard, loses its elasticity, and reduces the gold-trapping performance. After the mercury plate is put into production, the initial mercury application amount is 15-30 g/m3. After 6-12 hours, mercury is added. The mercury addition amount is 2-5 times of the ore gold content, and the mercury consumption is usually 3-8. Grams per ton of ore.
Mercury plate slope affects slurry flow rate and mineral stratification. Generally, the mercury plate slope is 7-9 degrees.
In addition, the temperature also affects the effect of mercury mixing. Too low a temperature will increase the viscosity of mercury and affect the effect of mercury mixing. If the temperature is too high, the mobility of mercury will increase, and part of the mercury will be lost with the loss of mercury. Therefore, the mercury-mixing index is prone to seasonal changes, and the mercury-mixing temperature should generally be greater than 15 degrees. The effect of adding mercury and adjusting the concentration of the slurry is used to eliminate the influence of temperature.
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