The five factors that affect the flotation effect of gold ore include: particle size of gold particles, flotation pH value of pulp, pulp concentration, slime content, mineral composition, etc.
The particle sizes of gold particles are extremely inconsistent, and different particle sizes have different floatability. The floatability of gold particles can be divided into four categories according to particle size:
+0.8mm, not floating;
-0.8mm+0.4mm, only 5% - 6% can float;
-0.4mm+0.25mm, the floating amount is about 25%;
-0.25mm, the flotation recovery can reach 96%.
Generally, the flotation gold particles should not be greater than 0.2mm, otherwise all coarse gold particles greater than 0.2mm must be selected by gravity separation, mercury mixing or other methods. The limit size of floating particles is also closely related to the shape and surface state of gold particles. Flat gold particles (flaky and tuberculous) are easy to float, while spherical ones are poor.
The best pH value of flotation is 7 ~ 9, and soda is generally used as the medium regulator. Lime will inhibit gold bearing pyrite and natural gold to a certain extent. In order to float gold smoothly, activators must be used, strong agitation must be carried out, a high pulp level must be maintained in the flotation machine, and foam must be quickly scraped out.
Pulp concentration is also very important. It is generally believed that thick pulp [liquid: solid = (2 ~ 2.5): 1] is beneficial to improve the recovery of coarse-grained gold, but if only flake fine-grained gold is contained, the liquid-solid ratio can be very large (for example, it can be diluted to 10:1).
When the content of primary slime is large, it often makes flotation difficult. Talc, mica, carbonaceous substances and other scaly minerals contained in the ore are easy to float out, which makes the concentrate lean. Clay slime is easy to cover the surface of gold particles, making it difficult to float and reducing the recovery rate.
The slime composed of iron and manganese oxides will also increase the consumption of reagents. Inhibit carbonaceous substances and available starches such as talc and mica. When restraining and dispersing clayey slime, attention must be paid to controlling the pH value of the medium to achieve the maximum gelation. Therefore, soda and a small amount of sodium silicate are often used to adjust the pH value of the medium and disperse the slime, and sometimes sodium sulfide is also used. These agents are usually added to the grinding circuit to avoid or reduce the adhesion of the slime to gold particles.
If there is soluble oxide in the ore, adding soda can also precipitate iron ions to avoid silicate gangue floating due to iron ion activation. A large amount of excess lime will inhibit gold, especially pyrite, which is not conducive to the flotation of gold bearing minerals.
Mineral composition has a great influence on the flotation of gold bearing ores. When there is free gold, it is generally necessary to use a strong collector and increase the amount of foaming agent, especially to strengthen the foaming effect at the end of flotation. The amount of free gold in the ore is usually relatively small, and the specific gravity is large, which is more difficult to float than sulfide. Good results can be obtained by using thick slurry. If there is an oxide film on the surface of gold particles, the contact time with the agent should be increased. In order to activate pyrite, copper sulfate and soda can be added to the grinding circuit. Sometimes, the cationic collector is used to select quartz in the tailings scavenging circuit, and the latter is reground to dissociate the dispersed fine gold.
As a professional Chinese beneficiation service provider, Xinhai mineral equipment can provide gold flotation general contracting services. Please contact us if necessary.
