Separation and beneficiation of spodumene

Spodumene is a lithium-containing aluminosilicate mineral, and lithium resources mainly exist in salt lakes and granite pegmatite deposits. Among them, salt lake lithium resources account for 69% of the global lithium reserves, accounting for 87% of the global lithium reserves. It is mostly produced in granite pegmatites, and sometimes coarse crystals can be formed. Spodumene (spodumene) is a high-quality mineral source for industrial extraction of lithium. But the beautifully colored and crystal-clear kunzite (emerald spodumene, purple spodumene) is used as a gem material. Typically gem quality spodumene can weigh over 1 carat, and spodumene over 5 carats is not uncommon.

In order to separate high-quality minerals, different separation methods are required for sorting. The separation methods of spodumene mainly include hand selection, thermal cracking, flotation, magnetic separation and gravity separation.

1. Hand separation method

In the 1950s and 1960s, artificial beneficiation was one of the main beneficiation methods for the production of lithium concentrate and beryl concentrate at home and abroad. In 1962, the output of beryl concentrate in the world was 7,400 tons, of which hand-selected concentrate accounted for 91%. This is mainly because most of the lithium ore comes from pegmatite deposits, and major industrial minerals such as spodumene and beryl have large crystals and are easy to choose. The artificial seed selection method has low technical requirements, simple operation process, no special site and equipment, and only needs to be carried out on a simple hand selection belt or a hand selection table, which can initially separate the ore from the gangue and improve the ore. Choose quality. But for now, manual separation is still the main method of producing lithium concentrate in developing countries where labor is cheap.

2. Flotation separation method

Spodumene is one of the main sources of lithium. Produced in muscovite and lepidolite granite pegmatites, it is a metasomatous mineral in the process of pegmatites. It often coexists with lepidolite, beryl, niobium-tantalite, tourmaline, muscovite, etc., and these gangue minerals belong to silicate minerals. In flotation separation, spodumene is often used to purify lithium ore by flotation. Spodumene is commonly used in positive flotation, reverse flotation and combined flotation.

Positive flotation: The positive flotation of spodumene is completed in an alkaline medium, and an anion collector is often used, and the ground minerals are added to a strong alkaline medium for high concentration and strong stirring operations. The high-consistency pulp is treated with sodium hydroxide, and the pulp is removed under the action of alkali. After scrubbing for several times to remove mud, add fatty acid or soap collector to make spodumene float directly.

Reverse flotation process: Spodumene reverse flotation process is also completed in alkaline medium, mainly using lime, starch and dextrin as corrosion inhibitors, and terpineol oil as foaming agent. Under alkaline medium conditions (pH 10.5~11.0), dextrin can effectively inhibit spodumene, and then use amine cationic collectors to capture silicate gangue minerals such as quartz, feldspar, and mica.

Combined chemical flotation process: suitable for salt lake lithium ore, using this method to extract lithium salt. The method is to evaporate the brine on the drying field, so that sodium salt and potassium salt are precipitated, and the concentration of lithium chloride is increased to about 6%. It is then sent to a factory where the lithium chloride is converted into the solid product lithium carbonate using the soda process.

3. Magnetic separation method

It is often used to remove iron-containing impurities in lithium concentrate or to separate weak magnetic lepidolite. In production practice, the spodumene concentrate obtained by flotation is used. Sometimes there are more iron impurities, in order to reduce the content of iron impurities, magnetic separation can be used for treatment. Magnetic separation equipment includes permanent magnetic drum magnetic separator, wet strong magnetic plate magnetic separator, vertical ring high gradient magnetic separator. The main component of spodumene tailings is feldspar, which can also be removed by vertical ring high gradient magnetic separator and electromagnetic slurry magnetic separator to obtain feldspar products that meet the requirements of ceramic raw materials.

4. Dense medium beneficiation method

Dense media beneficiation or heavy liquid beneficiation is an effective method for spodumene beneficiation. The beneficiation staff of the U.S. Bureau of Mines also used tetrabromoethane as the heavy liquid (density 2.9529 g/cm3) to conduct continuous tests on the heavy liquid cyclone separation of spodumene ore. Satisfactory results have been obtained. The feed particle size is -35 mesh, containing 20% spodumene, and the resulting concentrate contains 92-95% spodumene. The recovery rate is 86-89%, and the heavy liquid recovery rate is over 95%.

5. Thermal cracking method

It is a method of separating spodumene ore. The method is based on the fact that when the natural spodumene is roasted at about 1100°C, its crystal changes from α-type to β-type, and at the same time the volume expands and breaks into powder, so that the spodumene gangue can be obtained through selective grinding and screening. separation between minerals.

Which separation method is used to cooperate with each other to complete the selection of target minerals, so that the product can meet the requirements of sales grade, needs to be selected according to the intercalation characteristics, mineral composition and selectivity of the minerals. In the selection of spodumene, flotation is undoubtedly the most researched, mature and utilized process. Optional tests before beneficiation are very necessary.