Method for reducing ratio of magnesium to lithium in salt lake through solar-assisted salt crystallization

Abstract

The invention relates to a method for reducing the ratio of magnesium to lithium in a salt lake through solar-assisted salt crystallization. The method comprises the following steps: (1) adding a Mg<2+> salt at a molar ratio of the added Mg<2+> salt to Mg<2+> in saturated brine at (1:5)-(1:10) to the saturated brine which has a molar ratio of magnesium to lithium at (200:1)-(10:1), and drying thesaturated brine in the sun for 1-7 days so as to obtain a clear liquid and a granular precipitated crystal MgCl2.6H2O; (2) heating the precipitated crystal MgCl2.6H2O so as to obtain MgCl2.4H2O, MgCl2.2H2O or MgCl2; (3) adding a Mg<2+> salt to the clear liquid at a molar ratio of the added Mg<2+> salt to Mg<2+> in the clear liquid in the step (1) at (1:5)-(1:10), wherein the added Mg<2+> salt comprises MgCl2.4H2O, MgCl2.2H2O or MgCl2 obtained in the step (2); and drying the clear liquid in the sun for 1-7 days so as to obtain a clear solution and a granular precipitated crystal MgCl2.6H2O again; and (4), repeating the steps of (2) and (3), and repeating the cycle 2-8 times. According to the method, the products are generated through cyclic induction of the products, the entire salt dryingcycle is shortened, the production process is simple, less equipment investment is required, and no contaminants is introduced in the production process.

Description

technical field [0001] The invention belongs to the technical field of extracting lithium from salt lake sun-dried salt, and in particular relates to a method for assisting crystallized sun-dried salt to reduce the ratio of magnesium to lithium in a salt lake. Background technique [0002] A salt lake is a saline water body, usually referring to the salinity w(NaCl eq )>3.5% (greater than the average salinity of seawater), including dry brine lakes with dried-up surface brine and composed of saline deposits and intergranular brine. The brine contains a large amount of sodium, potassium, magnesium, lithium, chlorine, and sulfur It is one of the important raw materials for extracting lithium at present. [0003] There are many salt lakes in my country. Among them, the Qinghai salt lake area is the lake area with the most abundant salt lake resources in my country. The drying conditions are good, but the magnesium-lithium ratio of the salt lake resources itself is very high...

AI Technical Summary

Problems solved by technology

Among them, the solvent extraction method has high requirements on the acid corrosion resistance of the equipment, the acid and alkali consumption is high, and the organic phase residue of the raffinate pollutes the surrounding environment of the salt lake; the adsorption method consumes a lot of power and water, the eluent has a low lithium content, and the production The stability is poor; the HCl gas generated by the calcination water immersion method is highly corrosive, the energy consumption is high, and the amount of by-products is too large. The total recovery yield is low, and there are still difficulties in practical application; for brine with high lithium content and low magnesium-lithium ratio, evaporation crystallization separation method and precipitation method are generally used. The precipitation method is divided into two steps: salt field evaporation concentration and precipitation separation. Evaporation concentration is The process of naturally evaporating, concentrating, and separating high-concentration lithium-containing brine through salt field sun exposure, but this process has a long production cycle (15-30 days) and is greatly affected by natural conditions, resulting in low production efficiency.

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