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Click to add WeChatWith the decreasing of high-grade and easy-to-select gold ore resources, low-grade, complex and difficult-to-select gold ore has gradually become the main investment resource of mining companies, and carbon-containing gold ore, as one of the difficult-to-process gold ore, has become an important resource to be mined at this stage. So the following editor will introduce why carbon-containing gold ore is difficult to process, why it is pretreated, and the pretreatment method of carbon-containing gold ore.
Usually, the gold particle size in carbon-containing gold ore is fine (0.002~0.005mm), and it has a close symbiotic relationship with pyrite, carbonaceous materials, and gangue minerals. The physical phases of carbon in carbonaceous gold ore include solid (elemental) carbon and organic carbon (humic acid, long-bond hydrocarbons). During the gold leaching process, solid carbon and humic acid have a strong adsorption effect on gold complexes, resulting in the inability of activated carbon to effectively recover gold, that is, the "gold robbing" effect of carbonaceous substances; at the same time, long-bond hydrocarbons are adsorbed on the surface of activated carbon, reducing the adsorption efficiency of activated carbon on gold complexes. In addition, chlorite, chalcopyrite, layered silicates, etc. in the ore will produce a certain "gold robbing" effect.
In the pyrite solution system contaminated by carbon or graphite, carbon and graphite not only have a "gold robbing" effect, but also enhance the adsorption of gold on the surface of pyrite, and non-graphite carbonaceous substances have a stronger promoting effect on the adsorption of gold on the surface of pyrite. The carbon or graphite attached to the surface of pyrite reduces the electronegativity of the pyrite surface, thereby enhancing the physical adsorption effect of pyrite on the gold-cyanide complex. Although the "gold robbing" of pyrite or the "gold robbing" effect on the surface of graphite can be eliminated in a high-concentration cyanide environment, the "gold robbing" effect of carbonaceous matter attached to pyrite still exists, and fine grinding will further enhance the pollution of graphite and carbonaceous matter on mineral particles, making the "gold robbing" effect in the selection process of carbon-containing gold ore more serious. In addition to the "gold robbing" effect of carbonaceous matter leading to a decrease in gold leaching rate, the gold encapsulated in carbonaceous matter cannot be leached, and the floccules of fine carbon produced during the grinding process adsorb on the leached gold, etc., will lead to a significant decrease in gold leaching rate. Therefore, it is necessary to use pretreatment methods to eliminate the interference of carbonaceous matter on the selection of carbon-containing gold ore.
At present, the main pretreatment methods for carbon-containing gold ores include flotation decarbonization, carbon suppression gold extraction, oxidation roasting, chemical oxidation, etc.
Usually when the carbonaceous material in the ore is not the main gold-bearing mineral, non-polar oil can be used to pre-select the carbonaceous material, and the tailings are then treated by flotation-cyanidation process to obtain a higher gold recovery rate; when the carbonaceous material is the main gold-bearing mineral, the priority flotation-oxidation roasting-cyanidation gold extraction process is often used. Through flotation decarbonization pretreatment, gold-bearing carbonaceous materials can be directly extracted, and then gold can be recovered after oxidation and decarbonization. It is also possible to remove part of the carbonaceous materials by flotation and then extract gold. Both methods have achieved good results in production practice.
Before cyanidation, kerosene, heavy oil, petroleum, turpentine, marigold yellow, cresol acid, etc. are added to passivate or inhibit the activity of carbon, thereby reducing its adsorption capacity. This is also one of the commonly used pretreatment methods for carbon-containing gold ores.
Oxidation roasting is currently the main method for treating high-carbon gold ores. It has the advantages of simple process and feasible method. In recent years, the roasting efficiency has been effectively improved and pollution has been reduced through the transformation of roasting process and equipment.
The chemical oxidation method uses chemical oxidants such as potassium permanganate, chlorine, hypochlorite, nitric acid, and peroxide to oxidize carbonaceous materials. Its advantages are high efficiency and low investment, and its disadvantages are high price of oxidants and potential environmental pollution.
The above is an introduction to why carbon-containing gold ore is difficult to process, why it needs pretreatment, and the pretreatment methods. In the actual beneficiation process, whether the gold ore needs pretreatment depends on the type of impurities in the gold ore. When conventional methods cannot effectively separate them, gold pretreatment will be performed first to improve the gold ore beneficiation efficiency and the grade of gold concentrate.
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