In order to expose the gold is disseminated ore pyrite wrapped arsenic, arsenic minerals To eliminate the influence of the cyanide leaching of gold, gold ore containing arsenic several common pretreatment method.
1. Calcination Oxidation Method The arsenic gold ore is placed in a one-stage (or two-stage) roaster or in a rotary kiln, and calcined at 650 to 800 °C. Dearsenic is removed in a lower temperature, weak oxidizing atmosphere, and desulfurized in a higher temperature, oxidizing atmosphere. China's rotary kiln (7 tons / day) roasting arsenic-bearing gold ore, arsenic volatilization rate of more than 99%, sulfur volatilization rate of about 80%, arsenic recovery rate of up to 90%.
2. Pressurized oxidation method In a pressurized container, oxygen (or air) is introduced into the acidic (or alkaline) slurry of arsenic gold ore, and arsenic and sulfur are oxidized to arsenate and sulfate, thereby causing arsenic and sulfur. Mineral-coated gold particles are exposed for cyanide leaching. The temperature during pressurization oxidation was 170 to 190 ° C, the pressure was 1500 to 2000 kPa, and the treatment time was 2 hours. The leaching rate of gold after treatment by this method can be increased from 5 to 74% to 87 to 99%.
3. Bacterial Oxidation Bacterial leaching is carried out at 25 ° C at room temperature in three steps: 1) cultivation of Thiobacillus ferrooxidans in a bacterial culture medium to prepare a sulfuric acid bacterial leachate having a pH of 1.5 to 2.5; 2) bacterial catalysis, oxidative removal of arsenic, Sulfur; 3) The slag obtained after pretreatment is further cyanidated. The pretreatment solution activates the bacteria and then reuses them. South Africa used this method to leach -75 micron arsenopyrite. At pH 1.7, after 7 weeks of pretreatment, the ore cyanide leaching rate increased from 8.6% to 89.8%.
4. Other methods add a catalyst to accelerate the chemical oxidation process of arsenic mineral decomposition; use a highly conductive alkali (NaOH) solution as a medium to make the slurry undergo electrooxidation pretreatment under the action of the electrode; use the strong oxidizing property of nitric acid to arsenic And a nitric acid oxidation process in which sulfur is oxidized to arsenious acid and sulfuric acid.
Among the above various methods, the calcination oxidation method is widely used, and the investment in the pressurized oxidation method is relatively high, and the bacterial oxidation method is relatively low in investment and production cost, but the bacterial reproduction requires suitable conditions, and the reaction time is long, so Affected the industrial application of the law.
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