Companion gold in polymetallic mines often contains minerals such as arsenic and carbon, which have a certain impact on the flotation of gold ore. The mineral processing methods include cyanide leaching, flotation, gravity separation, and so on. This article will provide answers to three questions: how to process gold sulfide ore, how to process arsenic-containing gold ore, and how to process organic carbon-containing gold ore.
How to process gold sulfide ore
Flotation is the main method of processing gold sulfide ore. The main characteristics of this type of ore are that they often contain minerals such as gold, silver, lead, sulfur, etc. Metallic minerals include pyrite, sphalerite, galena, chalcopyrite, etc. The gangue minerals are mainly quartz, with some other minerals such as calcite, fluorite, etc. Gold minerals and sulfide minerals have similar flotation properties, especially the flotation properties of copper sulfide minerals, so the flotation process of gold is similar to that of copper sulfide.
The collector used in gold flotation includes xanthate, black medicine, ammonium black medicine, etc. There are usually two ways to use these collectors: individually or combined. Commonly used foaming agents include pine oil, cresylic acid, 730 series foaming agents, etc. The inhibitors include lime, sodium sulfide, chromic acid salts, etc., and the composition of reagents is selected according to the specific properties of the ore.
Due to the complex intergrowth relationship of this type of mineral, it is necessary to control the appropriate grinding fineness. In the process of determining the grinding fineness and reagent system, ore mineral processing experiments are particularly important.
How to process arsenic-containing gold ore
Arsenic not only has a great impact on the quality of gold concentrate but also causes environmental pollution. Arsenic in gold ore generally exists in the gangue mineral arsenopyrite, which is closely intergrown with gold minerals and difficult to separate.
Common methods to reduce the arsenic content in the concentrate include soda method, lime method, oxidation method, etc. Oxidation method is a more significant and widely used method. The main principle of this method is to use an oxidant to increase the free oxygen content in the solution, thereby oxidizing the surface of arsenic minerals and achieving the effect of inhibiting arsenic minerals.
On the basis of inhibiting arsenic, the free oxygen content in water can be increased and the flotability of arsenic minerals can be reduced by adjusting the pH value and temperature, thus reducing the arsenic content in gold concentrate. Generally, arsenic minerals have good flotability under weakly acidic conditions, while the flotability of arsenic minerals decreases under neutral and weak alkaline conditions. Gold minerals still have good flotability under these conditions. Therefore, the pH value of around 8 is usually used as the flotation pH value for arsenic-containing gold ore.
For different arsenic-containing gold ores, the specific oxidants, pH values, and temperature ranges are different. Using ore mineral processing experiments to determine suitable conditioning factors is a more scientific and reasonable approach.
How to process organic carbon-containing gold ore
Organic carbon minerals in gold ores not only have good flotability but also strong adsorption capacity. They not only affect the grade of gold concentrate but also waste a large amount of flotation reagents. Therefore, it is necessary to remove organic carbon to reduce its impact on gold flotation.
Decarburization can be achieved by calcination, adding reagents, etc. Calcination is mainly aimed at gold ores with high carbon content. For gold ores with relatively low carbon content, sodium silicate, No.2 oil, kerosene, etc. can be used to first select carbon. CMC can also be added to the pulp to inhibit the flotability of carbon. However, the method of adding inhibitors has a great impact on the gold recovery rate, so it is better to remove organic carbon by selecting carbon first.
The above are the common problems and their solutions in extracting gold from polymetallic mines. Polymetallic mines have a relatively complex ore composition. The gold plant needs to determine the parameter range through mineral processing experiments and adjust it according to the production needs of the plant. Specific mineral processing schemes are determined for different gold ores to achieve the desired recovery rate and gold concentrate grade.