Flotation of Copper Oxide Mines and Their Mixed Ores

  The common main Copper Oxide minerals include: Malachite (CuCO3-Cu(OH)2, Copper 57.4%, density 4g/cm³, hardness 4); Azurite (2CuCO3 · Cu (OH)2, Copper 55.2%, density 4g/cm³, hardness 4). In addition, there are also Chrysocolla (CuSiO3 · 2H2O, Copper 36.2%r, density 2-2.2g/cm³, hardness 2-4) and Chalcopyrite (Cu2O, Copper 88.8%, density 5.8-6.2g/cm³, hardness 3.5-4).

  Fatty acid collectors have good collection performance for non-ferrous metal oxide minerals, but due to poor selectivity (especially when the gangue is a carbonate mineral), it is difficult to improve the concentrate grade. Among the xanthate collectors, only high-grade xanthate has a certain collection effect on non-ferrous metal oxide minerals. However, the method of directly using xanthate flotation to Oxidize Copper ore without sulfurization treatment has not been widely used in industrial applications due to its high cost. In practical applications, the following methods are more common:

  ① Sulfurization method -- the most common and simple process, suitable for flotation of all sulfidizable Copper Oxide ores. After sulfurization treatment, the oxidized ore has the characteristics of sulfide ore and can be floated using xanthate. Malachite and Chalcopyrite are easy to sulfide with sodium sulfide, while Siliceous Malachite and Chalcopyrite are more difficult to sulfide.

During the sulfurization process, the dosage of sodium sulfide can reach 1-2kg/(t of raw ore). Due to the easy oxidation and short reaction time of sulfurizing reagents such as sodium sulfide, the generated sulfurized film is not stable enough, and strong stirring can easily cause detachment. Therefore, it should be added in batches without prior stirring and directly added to the first tank of the flotation machine. During sulfurization, the lower the pH value of the slurry, the faster the sulfurization rate.

When there is a large amount of mineral mud that needs to be dispersed, a dispersant should be added, usually using sodium silicate. Generally, butyl xanthate or mixed with dithiophosphate is used as a collector. The pH value of the slurry is usually maintained at around 9. If it is too low, lime can be added appropriately to adjust it.

  ② Organic acid flotation method -- Organic acids and their soaps can effectively float Malachite and Chalcopyrite. If the gangue mineral does not contain carbonates, this method is applicable; Otherwise, flotation will lose its selectivity. When the gangue is rich in floatable iron and manganese minerals, it can also lead to a deterioration of flotation indicators. When using organic acid collectors for flotation, sodium carbonate, sodium silicate, and phosphate are usually added as gangue depressants and slurry adjusters.

There are also cases in practice where sulfurization method is combined with organic acid flotation method. Firstly, sodium sulfide and xanthate are used to flotation Copper Sulfide and partial copper oxide, followed by organic acid flotation of the remaining Copper Oxide.

  ③ Leaching-precipitation-flotation method--used when both sulfurization and organic acid methods cannot obtain satisfactory results. This method utilizes the easy solubility of Copper Oxide minerals by first leaching the oxide ore with sulfuric acid, then replacing it with iron powder to precipitate Copper metal, and finally floating the precipitated Copper through flotation. Firstly, it is necessary to grind the mineral to a monomer dissociation state (-200 mesh accounting for 40%~80%) according to its embedding particle size. The leaching solution adopts a dilute sulfuric acid solution of 0.5%~3%, and the amount of acid is adjusted between 2.3~45kg/(t of raw ore) according to the properties of the ore. For ores that are difficult to leach, heating (45~70℃) leaching can be used. The flotation process is carried out in an acidic medium, and the collector is chosen to be cresol dithiophosphate or bis xanthate. The undissolved Copper sulfide minerals float up together with the precipitated Copper metal and eventually enter the flotation concentrate.

  ④ Ammonia leaching-sulfide precipitation-flotation method -- suitable for situations where ores are rich in a large amount of alkaline gangue, acid leaching consumes a large amount and is costly. This method first grinds the ore finely, and then adds sulfur powder for ammonia leaching treatment. During the leaching process, Copper ions in the oxidized copper ore react with NH3 and CO2, while being precipitated by sulfur ions to form new copper sulfide particles. Next, ammonia is recovered by evaporation and copper sulfide flotation is carried out. The pH value of the slurry needs to be controlled between 6.5 and 7.5, and excellent flotation results can be achieved using conventional copper sulfide flotation reagents. It is worth noting that the recycling of ammonia must be taken seriously to prevent environmental pollution.

  ⑤ Segregation-flotation -- its core is to mix ore with suitable particle size, 2%~3% coal powder, and 1%~2% salt, and then perform Chlorination reduction roasting in a high temperature environment of 700-800℃ to generate copper chloride. These chlorides evaporate from the ore and are reduced to metallic Copper in the furnace, which then adsorbs onto the surface of coal particles. Subsequently, Copper metal was effectively separated from gangue through flotation method. This method is particularly suitable for processing difficult to select copper oxide ores, especially complex Copper oxide ores with high mud content and combined Copper accounting for more than 30% of the total Copper content, as well as ores rich in Malachite and Chalcopyrite. In the comprehensive recovery of Gold, Silver, and other rare metals, the separation method exhibits significant advantages compared to the leaching flotation method. However, its disadvantage is that it consumes a large amount of heat energy, resulting in relatively high costs..

  ⑥ Flotation of mixed Copper ore -- the flotation process of mixed Copper ore should be determined based on experimental results. The available processes include: firstly, synchronous flotation of oxidized minerals and sulfide minerals after sulfidation; The second is to first flotation sulfide minerals, and then flotation oxidized minerals after sulfidizing tailings. When simultaneously flotation Copper oxide minerals and Copper sulfide minerals, the process conditions are basically the same as those for flotation of oxide minerals, but it should be noted that as the oxide content in the ore decreases, the amount of sodium sulfide and collector should be correspondingly reduced.

There are usually two main processes used for the treatment of Copper Oxide ores abroad: sulfide flotation and acid leaching precipitation flotation.