The wetting of gold by mercury depends on a number of factors, of which the following are more important:
1. The particle size of gold and the degree of monomer dissociation The effect of gold particle size, shape and structure on the amalgamation effect is mainly determined by the degree to which gold particles dissociate from the minerals encapsulating it. Production practice shows that grainy, spherical or dendritic gold particles are easily amalgamated, and the key to amalgamation is the monomer dissociation of gold particles. Therefore, when dealing with sand mines, the shredding operations should be as full as possible. When processing the pulse gold, in the case of ensuring no pulverization, appropriately increasing the fineness of the grinding can improve the recovery rate of the amalgamation operation. The gold particle size generally suitable for amalgamation is 0.2 to 0.03 mm. When a mercury amalgamation plate is used in the grinding cycle, the lower limit of the particle size of the amalgamation is 0.015 mm.
2. The color of gold in the color ore of gold particles directly affects the recovery rate. The most easily amalgamated is pure gold, but it is difficult to encounter chemically pure gold in nature. In addition to gold, gold particles usually contain impurities such as silver , copper and iron . Due to the presence of these impurities, the ability of gold to be amalgamated is reduced. For example, when gold contains 10% silver, the ability to be wetted by mercury is significantly reduced. The gold color of gold in gold mines is often higher than that of vein gold. The coloration in the oxidized zone ore is generally higher than the coloration of gold in the primary ore.
Fresh and clean surface of gold particles is an important condition to improve the recovery rate of mercury. When the surface of the gold particles is contaminated or "rusted", its ability to amalgamize is reduced, and even amalgamation cannot be carried out. The main causes of surface contamination of gold particles are: 1) Gold particles are deformed during the grinding process, and some iron chips or quartz particles are pressed into the surface of the gold particles. 2) The oil mixed into the ore particles during the grinding process adheres to the surface of the gold particles. A similar phenomenon occurs when the ore contains talc , graphite or other carbonaceous materials; 3) particles suspended in the slurry or impurities dissolved in the water cover the surface of the gold particles to form an adsorption film. The so-called "rusting" of the surface of gold particles refers to the formation of an oxide film or a silicate film on the surface. Gold amalgamation of the surface "rusty" is difficult, and gold in the coating layer does not constitute a mercury paste at all. This is a good preparation, first removing the stained cover, usually by mechanical grinding. When gold particles are dissociated from the ore, they are most likely to be mixed. Therefore, the internal amalgamation is better than the external amalgamation.
3. Working temperature Mercury is liquid at room temperature, its melting point is minus 38.89 ° C, and the boiling point is 357.25 ° C. The activity of mercury increases with the increase of slurry temperature, so increasing the temperature of the slurry can increase the wetting ability of mercury to gold particles. However, if the temperature is too high, the mobility of mercury will increase, and part of the gold will be lost with the loss of mercury. At the same time, the evaporation rate of mercury will increase. As the evaporation of mercury also produces slow oxidation, the surface of mercury is denser. The oxide layer affects the progress of the amalgamation operation. When the temperature is too low, the viscosity of mercury increases, which reduces the wetting effect on the gold particles. The temperature of the amalgamation operation is generally maintained above 15 °C, but should not be higher than 26.7 °C. When using a mercury-mixing cylinder, it should be kept above 65 °C.
4. When the concentration of the slurry is single, the concentration of the slurry should not be too large, usually 10 to 25%. A thin slurry flow is formed on the mercury plate, so that the gold particles are at a large sedimentation speed, otherwise the fine particles or It is difficult for the fine particles to settle completely onto the mercury plate. When mixing a mixture of externally mixed mercury and other beneficiation methods, for example, when the externally mixed mercury is placed between the grinding and grading circuits, it is sometimes necessary to take care of the subsequent processes. The slurry concentration should be reduced as much as possible while meeting the entire selection requirements. The slurry concentration of the externally mixed mercury is preferably 25%. The most suitable concentration of slurry for internal amalgamation is 30-50%.
5. The practice of pH production of pulp shows that the pH value of the amalgamation operation is 8-8. The effect of mixing mercury in an acidic medium or a cyanide solution (0.05% sodium cyanide) is better. This is because the film of base metal oxide formed on the surface of gold particles and mercury can be dissolved by acid or cyanide solution during the amalgamation process. However, the slime is not easy to agglomerate in the acidic medium, which will contaminate the surface of the gold particles. The soluble salt entering the pulp will form a base metal amalgam covering the surface of the mercury, which will worsen the gold amalgamation operation. Alkaline media can improve amalgamation conditions. If lime is used as a modifier, it can precipitate soluble salts, eliminate the influence of oils mixed into the slurry, and also make the slime agglomerate and reduce the viscosity of the medium. However, the addition of lime should not be excessive, otherwise the amalgamation rate will be lowered.
6. Mercury quality The quality of mercury has a significant impact on the amalgamation effect. Pure mercury has a poor wetting effect on gold particles due to excessive surface tension. When mercury contains a small amount of gold, silver and barium metal, the surface tension is lowered to improve the wetting effect. If mercury contains 0.1 to 0.2% of gold, it can accelerate the amalgamation process of mercury to gold. When mercury contains 0.1% silver, the ability to wet gold can be increased by 0.7 times, and when the gold and silver content is 5%, it can be doubled. When mercury contains less than 0.1% of copper, lead and zinc , it also promotes the wetting of gold by mercury. However, the ore arsenic, antimony, bismuth sulfide and pyrite and galena, etc., easily attached to the surface of the mercury, the mercury wetting ability to reduce the gold.
7. The amount and frequency of mercury addition The amount of mercury added and the number of additions directly affect the gold extraction effect. The amount of mercury added should be appropriate. Adding too much mercury will reduce the elasticity and consistency of the mercury paste, causing the loss of mercury paste and mercury with the slurry. If the amount of mercury added is insufficient, the mercury paste will be hard and the ability to capture gold will lower you. The mobility of mercury in summer should be increased.

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