Method for separating magnesium from lithium and extracting lithium from brine

Abstract

The invention provides a method for separating magnesium from lithium and extracting the lithium from high magnesium-lithium ratio brine (brine from a saline lake, from underground and from an oil-gas field). The method comprises: sodium salt and potassium and magnesium mixed salt are separated from the brine by evaporation of a saltpan; after boron extraction, sodium hydroxide is used for precipitating Mg<2+> from obtained old brine, and crystallized Mg(OH)2 is obtained by modification and precipitation condition control; filtration and separation are carried out to remove the Mg(OH)2 to realize separation of magnesium and lithium; after filtered mother solution is vaporized and concentrated for 2-4 times, Na2SO4 and NaCl are separated by crystallization, and pure caustic soda can be added to form lithium carbonate from lithium; or the operation of further evaporation is carried out until Na2SO4 and NaCl are separated by multiple times of natural evaporation or forced evaporation concentration and multiple times of cooling crystallization; the operations of evaporation and concentration are carried out until LiCl saturation, and LiCl products can be prepared after the operation of cooling crystallization is carried out. Compared with the prior art for separating the magnesium from the lithium and extracting the lithium from the brine, the method obtains the crystallized Mg(OH)2 by modification and precipitation condition control, solves the existing technical problem of hard filtration of Mg(OH)2, solves the defects of high energy consumption, complex process and high cost of the existing calcination method, and solves the fundamental defects of low Li<2+> recovery ratio and complex technical process of the traditional precipitation method. The Li<2+> recovery ratio ranges from 85-93%, Mg<2+> removal ratio is more than 99.5%, and the method solves the problem of extracting Li<+> and Mg<2+> from high-magnesium and low-lithium brine with Mg<2+> / Li<+>>=20 mass ratio.

Description

technical field [0001] The invention relates to the technology of separating magnesium and lithium from brine (salt lake brine, underground brine, oil and gas field brine) and preparing inorganic lithium salt products, in particular to high magnesium-lithium ratio (Mg 2+ / Li + ≥20 mass ratio) brine magnesium lithium separation technology problem. Background technique [0002] Lithium and its compounds have extremely important and extensive applications, especially occupying an irreplaceable position in the field of new energy (lithium batteries). There are abundant lithium resources in brines, and plateau salt lakes, underground brines in basins, and brines in oil and gas fields all contain a large amount of lithium. However, since lithium in brine often coexists with a large amount of alkali metal and alkaline earth metal ions in trace amounts, and their chemical properties are very similar, it is difficult to extract and separate lithium from brine, especially from high-...

AI Technical Summary

Problems solved by technology

Although this method overcomes some shortcomings of the above-mentioned method, the process is relatively simple, and Li + The loss rate has been reduced, but the fundamental disadvantage of this method is that the precipitates are mostly colloidal precipitates, and the amount is large, and it is difficult to filter, resulting in Li + The loss is relatively large, reaching 15-20%, and the utilization of boron is more difficult, so it has not been used in industry so far.

[0004] Magnesium sulfate subtype salt lakes in western my country (such as Lake Xitaijinel in Qinghai) brine contains a large amount of Mg 2+ 、K + 、Na + , SO 4 2- , Cl - , Li + In addition, it also contains a large amount of B 2 o 3 , after precipitation of sodium salt, potassium and magnesium mixed salt through the salt field, Li + with large amounts of Mg 2+ 、B 2 o 3 , SO 4 2- Coexistence, using the general sodium hydroxide precipitation method to remove magnesium, because magnesium hydroxide is colloidal precipitation, not only extremely difficult to filter, but also leads to a large amount of lithium loss, which is difficult to achieve in engineering, making lithium extraction technology very difficult

Existing research results and technologies are difficult to solve this technical problem economically and effectively

Images