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Click to add WeChatAs a strategic resource, lithium resources play an important role in the energy revolution and green and low-carbon development. With the increase of application scenarios such as new energy vehicles and energy storage, the demand for lithium resources has increased rapidly. About 35% of the world's lithium resources come from lithium-rich minerals and clays. my country's lithium-containing minerals are mainly spodumene, lepidolite and a small amount of lithium phosphate, all of which are present in lithium-rich granite pegmatites. Due to the difference in ore types, the beneficiation processes of these lithium ores are also different.
As a typical lithium ore, spodumene ore has various crystal forms, including columnar, granular or plate-like, and has a monoclinic crystal structure. In the beneficiation process of spodumene ore, flotation is the main beneficiation method, in addition to magnetic separation and gravity separation as auxiliary means. Flotation is further divided into direct flotation and reverse flotation.
Spodumene direct flotation utilizes the difference in the surface chemical properties of spodumene and gangue minerals and is carried out in an alkaline medium. First, the ground mineral is added to a strong alkaline medium for high-concentration strong stirring. The high-concentration slurry is treated with sodium hydroxide to remove the slurry under the action of alkalinity, and after multiple washing and desludging, fatty acids or soap collectors are added to directly float spodumene. In this process, the added sodium hydroxide reacts with the silicate gangue minerals in the slurry to form a sodium silicate (water glass) inhibitor. This activates the silica leached from the surface of spodumene, while the gangue minerals generate insoluble compounds due to the activated cations (iron, calcium, copper, etc.) on their surfaces, which are then suppressed, thus achieving the flotation of spodumene.
The combination of "three alkalis and two soaps" is commonly used in the flotation process. "Three alkalis" refers to sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and sodium sulfide (Na2S), which are used as adjusters to optimize the chemical environment of the slurry. "Two soaps" refer to oxidized paraffin soap and cyclohexane acid soap, which are used as collectors with foaming properties to promote the adhesion of spodumene minerals to bubbles. In addition, sodium carbonate and sulfuric acid are used to adjust the pH value. Sodium carbonate is also used to disperse the sludge and precipitate multivalent harmful metal ions to help remove gangue minerals.
The reverse flotation method of spodumene mainly uses lime to create an alkaline environment, adds starch, dextrin, etc. to inhibit the floating of lithium ore, and uses pine oil as a foaming agent. Under alkaline medium (pH 10.5~11.0), dextrin adjuster can effectively inhibit spodumene, and then amine cationic collectors are used to capture silicate gangue minerals such as quartz, feldspar, and mica, leaving the spodumene concentrate in the tank to achieve reverse flotation. Magnetic separation and gravity separation are used as auxiliary methods to remove impurities and further improve the purity of spodumene concentrate.
Lepidolite ore is a monoclinic layered silicate mineral with flaky or scaly aggregates and a rose or light purple color. The mineral processing technology of lepidolite ore mainly relies on flotation method, which uses the difference in physical and chemical properties of the mineral surface to achieve mineral separation. Since lithium mica has good floatability, the positive flotation method is widely used in this process.
In the flotation process, a suitable collector should be selected first to enhance the affinity of lithium mica minerals with bubbles and promote their floating. Commonly used collectors include anionic fatty acids, combined collectors of fatty acids and amines, and cationic amine collectors. In particular, cationic amine collectors, such as octadecylamine, have a good flotation effect on lithium mica in acidic and neutral media. However, lithium mica that has not been activated cannot be effectively captured by oleic acid collectors. Therefore, it is usually necessary to pre-treat the lithium mica with an activator such as hydrofluoric acid to improve its floatability and obtain better flotation indicators. After the flotation process, the lithium mica minerals are selected with the foam, and then washed, concentrated and dried to obtain high-grade lithium concentrate.
The method of lithium aluminum phosphate beneficiation is to first obtain lithium aluminum phosphate concentrate from lithium and phosphate-rich minerals by flotation, and then grind it for pretreatment. Then, concentrated sulfuric acid is used for leaching to convert lithium and aluminum into soluble sulfates, and fluorides and phosphates are extracted to produce enriched leachate. Acidic impurities are removed by adding limestone, lime, monovalent carbonates or hydroxides for precipitation, and lithium is recovered as a lithium salt product.
In actual beneficiation plants, it is necessary to conduct beneficiation test analysis first for the types and properties of ores in different deposits. Through beneficiation tests, suitable lithium extraction methods are designed, and lithium ore beneficiation equipment is customized according to these methods to determine the appropriate beneficiation process plan. At the same time, the selection and usage of reagents also need to be reasonably adjusted according to the characteristics of the ore, the requirements of the benefiting technology and the product quality standards. This can ensure the smooth progress of the entire beneficiation process and achieve efficient lithium extraction.
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