[Lithium extraction technology] Lithium extraction process with lepidolite: Lithium extraction with sulfate

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In the application of lithium extraction technology, the main raw materials are spodumene and lepidolite. The content of spodumene in our country is not high and we need to rely on large quantities of imports. However, our country is relatively rich in lepidolite. . Has high mining value. At present, the main methods for extracting lithium from lepidolite include: lime sintering method, sulfate method, sulfuric acid method, chloride roasting method and soda ash pressure cooking method. Among them, the sulfuric acid method is currently the most widely used method for extracting lithium.

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Suitable ore types for lithium extraction by sulfuric acid

Lithium extraction by sulfuric acid can be used to process spodumene, lepidolite, and lithium aluminite. In addition, it can also be used to process low-grade lithium-containing ores (Li₂O content is 1.0~1.5 %).

Lithium extraction process with sulfuric acid

The lithium extraction process with sulfuric acid is to roast lepidolite at a high temperature of 950℃~1100℃, so that its crystal form changes from monoclinic system to The tetragonal crystal system has enhanced chemical activity; then, after mixing concentrated H₂SO₄ with β-lithium mineral, control the roasting temperature to 250~300℃ for roasting to make it Replacement occurs. The replacement reaction is as follows:

The roasted product generated after the replacement is leached with dilute sulfuric acid in a stirring tank to purify and remove a large amount of Ca²⁺ , Mg²⁺, Fe³⁺, Al³⁺ and other impurities, and then use Na₂CO₃ Further remove Ca²⁺ and Mg²⁺ to obtain pure Li₂SO₄; Evaporate and concentrate the solution, add Na₂CO₃ and react with Li₂SO₄ to generate Li< sub>2CO₃; the precipitate can be washed and dried to obtain pure Li₂CO₃. Lithium recovery The rate can reach 90%.

Characteristics of sulfuric acid lithium extraction process

The sulfuric acid lithium extraction process has the advantages of low energy consumption, high production efficiency, and high recovery rate of lithium and potassium. However, the sulfuric acid method has problems such as high impurity content in the leachate, large consumption of sulfuric acid and soda ash, and severe corrosion of equipment.

Lithium extraction from lepidolite can be carried out by the sulfuric acid method. Specifically, the sulfuric acid leaching method or the sulfuric acid roasting and impregnation method can be used. Among them, the sulfuric acid leaching method mainly uses sulfuric acid to fully soak lepidolite, so that it can directly generate lithium. Although the application of this method does not require high-temperature roasting treatment, there will be no higher production capacity requirements in the production process, but it is accompanied by sulfuric acid. Soaking, a large amount of aluminum will appear at the same time. The subsequent separation of aluminum and lithium will also face high difficulties, and will also bring serious sulfuric acid loss. There are also high requirements for the fineness of lepidolite, which is not suitable for Lepidolite material used.

The application of the sulfuric acid roasting and impregnation method is mainly to use high-temperature roasting while applying sulfuric acid materials to further improve the extraction rate of lithium. Although the applicability of this method is ideal, it suffers from the loss of energy consumption. It is too serious and has strict requirements for roasting. It is currently phased out and the salt roasting method is used for optimization.

In the practical application of the sulfuric acid method, it is generally necessary to use 55% sulfuric acid to treat 150-mesh lepidolite, and ensure that the mass ratio of lepidolite to concentrated sulfuric acid is 1:2 during the reaction. , ensure that the reaction environment temperature is 135°C, and given sufficient time, lithium can be effectively leached.