In nature, sulfide minerals are subjected to the action of air or water oxygen and water ions to form oxidized minerals. Sulfide minerals form oxidized minerals when oxygen and water ions react with them in nature. The oxidation process usually occurs in the upper part of the deposit, and the thickness of the oxide layer can reach 10-50m according to different geological conditions. Ores can be divided into oxide ore, the sulfide ore, and mixed ore according to the ore oxidation rate (referring to the percentage of metal in the state of oxidized mineral). Generally speaking, if the oxidation rate is above 30%, it is oxidized ore, and if the oxidation rate is below 10%, it is sulfide ore, and it is mixed ore between the two. The main minerals of non-ferrous metal oxide ore are copper oxide, lead oxide, and the zinc oxide ore. Non-ferrous metal oxide ore has the following characteristics: 1. The structure is more complex, the dissemination particle size is fine, it is not easy to dissociate, it is generally very brittle, and it is easy to sludge when finely ground; The buoyancy varies greatly; (3) it often contains a large amount of slime and soluble salt; (4) the properties of oxidized ores in different deposits are very different, and even the degree of oxidation and the properties of ore in different sections of the same deposit vary greatly. Therefore, the flotation of oxide ore is more difficult. Flotation beneficiation process study and test for copper metal and its mixed ore.
The common main test for copper metal are: malachite (CuCO3 Cu(OH)2), containing 57.4% copper, density 4g/cm3, hardness 4); azurite (azurite, 2CUCO3 Cu(OH)2), copper 55.2%, density 4g/cm3, hardness 4). Followed by: malachite (CuSiO3 2H2O, copper content 36.2%, density 2~2.2g/cm3, hardness 2~4) and cuprite (Cu2O, copper content 88.8%, density 5.8~6.2g/cm3, hardness 3.5 to 4).
Due to poor selectivity (especially when gangue is carbonate minerals), fatty acid collectors do not perform well on non-ferrous metal oxide minerals. Among the xanthate-type collectors, only high-grade xanthate can collect non-ferrous metal oxide minerals. Direct flotation test for copper oxide metal with xanthate has not been used in the industry without vulcanization.
① Sulfidation method—the most common and simple process, this method can be used for flotation of any copper oxide ore that can be sulfided. Oxidized ore after sulfide has the properties of sulfide ore and can be floated with xanthate. With sodium sulfide, malachite and azurite are easily sulfided, while malachite and cuprite are more difficult.
During vulcanization, sodium sulfide levels can reach 1-2kg/(t raw ore). Sodium sulfide and other vulcanizing agents are easy to be oxidized, and the action time is short, so they should be added in batches without prestirring, and directly to the first tank of the flotation machine. The vulcanized film is unstable and easily falls off when vigorously stirred, so it should be added in batches without pre-stirring. Vulcanization is sped up by a lower pH of pulp during vulcanization.
The ore slime needs to be dispersed with a dispersant, usually water glass. Black medicine or butyl xanthate are usually used as collectors. Pulp usually has a pH value of 9 or 10. An appropriate amount of lime can be added when it is too low.
② Organic acid flotation method——Organic acid and its soaps can flotate malachite and azurite well. This method can be used when gangue minerals are not carbonating minerals. Otherwise, the flotation will lose its selectivity. When the gangue contains a large amount of floatable iron and manganese minerals, the same effect will be produced and the flotation index will have deteriorated. As gangue inhibitors and slurry conditioners, sodium carbonate, water glass, and phosphate are usually added to organic acid collectors for flotation.
There are also examples of the mixed application of vulcanization and organic acid flotation. First, use sodium sulfide and xanthate to float copper sulfide and part of copper oxide, and then use organic acids to float the remaining copper oxide.
③ leaching-precipitation-flotation method—used when neither the sulfurization method nor the organic acid method can obtain satisfactory results. In this method, copper oxide minerals are easier to dissolve. The oxide ore is first leached with sulfuric acid, and then replaced with iron powder to precipitate metallic copper, and then float the precipitated copper by flotation. The method should firstly grind it to the monomer dissociation according to the mineral-embedded particle size (-200 mesh accounts for 40% to 80%). The leaching solution is 0.5%-3% dilute sulfuric acid solution, and the amount of acid varies from 2.3-45kg/(t raw ore) with the properties of the ore. For the ore that is difficult to leaching, heating (45-70℃) can be used for leaching. The flotation is carried out in an acidic medium, and the collector is cresol black or double xanthate. The undissolved copper sulfide minerals float up together with the precipitated metallic copper and enter the flotation concentrate.
④ Ammonia leaching – sulfide precipitation – flotation method – if the ore contains a lot of alkaline gangue, it is used when the consumption of acid leaching is large and the cost is too high. In this method, after the ore is finely ground, sulfur powder is added, and then ammonia is leached. During the leaching process, the copper ions in the copper oxide ore interact with NH3 and CO2, and at the same time, they are precipitated by sulfide ions to become new copper sulfide particles. The pH of the pulp is 6.5-7.5, and good indicators can be obtained by using the flotation reagents of general copper sulfide ore. This method should pay attention to the recovery of ammonia, otherwise it will cause environmental pollution.
⑤ Segregation – flotation method – the essence is to mix ore with appropriate particle size with 2% to 3% coal powder and 1% to 2% salt, and perform chlorination reduction roasting at 700 to 800 ° C to generate copper. The chlorides are volatilized from the ore, reduced to metallic copper in the furnace, adsorbed on the coal particles, and then separated from the gangue by flotation. This method is suitable for the treatment of refractory copper oxide ores, especially the refractory copper oxide ores with a large amount of mud and more than 30% of the total copper, and ores containing a large amount of malachite and cuprite. In the comprehensive recovery of gold, silver and other rare metals, the segregation method is superior to the leaching-flotation method. The disadvantage is that the heat consumption is large and the cost is high.
⑥ Flotation of mixed copper ore—Mixed copper test for copper metal. The process of simultaneous flotation of oxidized minerals and sulfide minerals after sulfide can be adopted, or the first selection of sulfide minerals and tailings sulfide can be adopted. Then select the process of oxidizing minerals. At the same time, the process conditions for the flotation of copper oxide minerals and copper sulfide minerals are basically the same as those for the flotation of oxidized minerals, but the amount of sodium sulfide and collectors should be reduced correspondingly with the reduction of oxide content in the ore.