Method for enriching lithium in lithium-containing brine of salt lake

Abstract

The invention discloses a method for enriching lithium in lithium-containing brine of a salt lake. The method comprises the following steps of firstly, performing impurity removal and thinning pretreatment on the lithium-containing brine of the salt lake; then, sequentially treating the obtained enriching concentrated liquid by a membrane separation system, a reverse osmosis system, an electrodialysis system, a deep magnesium removal system and an MVR (mechanical vapor recompression) system; finally, obtaining third-level concentrated liquid, wherein the content of Li<+> can reach the concentration required by lithium precipitation, and the third-level concentrated liquid can be directly used as a precipitate to prepare a lithium product. The method has the advantages that in each enriching phase, the concentrations of Li<+> and the magnesium-lithium ratios in correspondingly obtained first lithium-rich solution, first-level concentrated liquid, second-level concentrated liquid, second lithium-rich solution and third-level concentrated liquid are strictly controlled; by effectively coupling the separating systems, the lithium ions in the lithium-containing brine of the salt lake can be efficiently enriched, and the high recycling rate of lithium in the process is guaranteed; furthermore, the reverse osmosis produced water, electrodialysis produced water and MVR produced water produced in different enriching phases can be reasonably recycled, the high recycling rate of fresh water is guaranteed, the energy consumption is decreased, and the cost is reduced.

Description

technical field [0001] The invention belongs to the technical field of solution separation and purification, and in particular relates to a method for enriching lithium in lithium-containing brine of a salt lake. Background technique [0002] Salt lake lithium resources account for more than 69% of the world's industrial reserves of lithium resources, and my country's lithium resource reserves rank fifth in the world, of which salt lake lithium resources account for 71%; it is estimated that Qinghai salt lake lithium salt (in Li 2 (2) The reserves are as high as 13.92 million tons, ranking first in the country. Therefore, extracting lithium from salt lake brine has become the top priority for my country to compete for the strategic highland of energy, and is a major strategic demand of the country. [0003] The salient feature of Qinghai Salt Lake brine is the high magnesium-lithium ratio (i.e. the mass ratio of magnesium ions to lithium ions). For example, the magnesium-lit...

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Problems solved by technology

Although the above method has played the role of enriching and separating lithium ions to a certain extent, the above methods (1) and (2) all have certain disadvantages. For example, the concentrated solution obtained through reverse osmosis needs to be further evaporated in salt fields to achieve precipitation. Lithium ion concentration required for conversion, but impurity ions, insoluble matter, etc. will be introduced in the process, which will affect the purity of the final product, and a large amount of fresh water cannot be effectively recycled, and at the same time, the concentration efficiency of the salt field evaporation process is poor and the recovery rate of lithium is low; method (3) There is also the problem that using the reverse osmosis process for enrichment and concentration under high concentration conditions will increase investment costs and equipment energy consumption.

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