Method for extracting ultrahigh-purity lithium carbonate from salt lake brine with high magnesium-lithium ratio

Abstract

The invention discloses a method for extracting ultrahigh-purity lithium carbonate from chloride brine with a high magnesium-lithium ratio. The method comprises the following steps of: preparing a lithium chloride concentrated solution by an adsorption, desorption and evaporation concentration process; purifying, and precipitating lithium carbonate by using ammonium bicarbonate pulp; and converting into a lithium bicarbonate solution, filtering, and decarburizing. By improving steps and parameters of the conventional process, the purity of a product is more than 99.99 weight percent and the total amount of major impurities is not more than 0.002 weight percent without the introduction of additional high-cost purification steps such as ion exchange resin / membranes; and additional sodium ions are not introduced in the production process, byproducts at all stages can be recycled, and only an extremely small amount of waste solution is generated.

Description

[0001] technical field [0002] The invention relates to an inorganic salt extraction process, in particular to a method for extracting ultra-high-purity lithium carbonate from high-magnesium-lithium ratio salt lake brine, especially chloride-type brine. [0003] Background technique [0004] Lithium is an important strategic resource, which mainly exists in nature in two forms of solid minerals and liquid minerals, among which lithium reserves in salt lake brine account for 69% of the world's reserves. Lithium carbonate is the most critical product in the lithium industry. It can not only be used to make ceramics, medicines, catalysts, etc., but also the basic material for the production of secondary lithium salts and lithium metal. [0005] Many methods for extracting lithium carbonate from salt lake brine have been disclosed in the prior art. These methods mainly include the steps of concentrating salt solution, removing impurity ions and using ammonium carbonate or sod...

AI Technical Summary

Problems solved by technology

[0006]However, there are still deficiencies in the current preparation method, the most notable of which is that it is difficult to further improve the product purity, and it is difficult to meet some ultra-high purity applications such as medicine, catalyst and atomic energy industry and other special field requirements

Moreover, as a key step to obtain lithium concentrate, the evaporation and concentration process is not effective when directly applied to high-magnesium-lithium ratio salt lake brine, especially chloride-type brine; sodium carbonate as a precipitant will bring a large amount of sodium ions, It takes a lot of water to remove, the sodium content in the product is relatively high, and a large amount of sodium chloride waste solution is produced at the same time, which cannot achieve sustainable production