Method for extracting alkali metal from salt lake brine and seawater through membrane extraction-back extraction

Abstract

The invention discloses a method for extracting high-value alkali metal from salt lake brine or seawater through membrane extraction-back extraction. The method is implemented through continuous operation and comprises the following steps of: fixing an ion exchange blend membrane in a membrane component, allowing an organic solution containing an extracting agent to contact salt lake brine or seawater which contains alkali metal ions by a first ion exchange membrane, and allowing alkali metal ions to pass through the ion exchange membrane and be combined with the organic solution containing the extracting agent to obtain metal complex; then transmitting an organic solution of the metal complex to a second ion exchange membrane and allowing the organic solution of the metal complex to contact a back extraction solution by the second ion exchange membrane, and allowing the metal ions to pass through the ion exchange membrane to enter the back extraction solution; during membrane extraction-back extraction, and circulating feed liquid, the back extraction solution and the organic solution containing the extracting agent on one side of the first ion exchange membrane, on one side of the second ion exchange membrane and between the first and second ion exchange membranes; and performing back extraction until a certain concentration of the back extraction solution is reached, and separating lithium, rubidium or caesium precipitates to obtain the final product. The invention provides a high-efficiency, low-cost and feasible route for industrial production of alkali metal salts.

Description

technical field [0001] The invention relates to a technology for extracting high-value alkali metals from solutions, and is especially suitable for extracting high-value alkali metals such as lithium, rubidium, and cesium from low-concentration lithium-containing seawater or high-magnesium-lithium ratio salt lake brine, and extracting high-value alkali metals such as lithium, rubidium, and cesium from seawater or salt lakes. Brine is used as raw material to produce high-value alkali metal salts such as lithium, rubidium, and cesium. Background technique [0002] High-value alkali metals mainly refer to lithium, rubidium, and cesium. Because of their low density and low melting point, their application fields are becoming wider and wider, and they have attracted people's attention. Lithium is widely used in the ceramic industry, glass industry, aluminum industry, lubricants, refrigerants, high-energy batteries, controlled nuclear fusion reactors and optoelectronic industries....

AI Technical Summary

Problems solved by technology

In the 20th century, the production of lithium salts in the world mainly used solid lithium-containing ores as raw materials. The output was low and the cost was high, which was far from meeting the needs of economic development, and the solid lithium-containing ores continued to decrease and their grades gradually declined. Lithium resources in salt lakes and seawater Rich, the process of producing lithium from solution is simple, and the cost is relatively low compared with solid ore. Therefore, salt lake brine and seawater have gradually become the focus of research on lithium extraction at home and abroad.

It can be seen that the high cost and low adsorption capacity of the resin used in the ion adsorption method also limit its development and application.

[0008] Chinese patents CN1724372A and CN1724373A disclose a method for producing lithium carbonate by calcining and leaching. The process flow of the method is spray drying, calcining, washing with water, evaporation and concentration, and precipitation to obtain lithium carbonate products. The calcining temperature is 554-1200 ° C. Li after evaporation and concentration + The content is 14-21g / L. This method can effectively separate and produce lithium carbonate from high-magnesium lithium-containing brine, but the energy consumption is high, the equipment requirements are high, and the environment pollution is large.

[0009] Chinese patent CN1335263A discloses the carbonization method to produce lithium carbonate from salt lake brine with high magnesium-lithium ratio. The method is to add precipitation to the old brine after the magnesium sulfate subtype salt lake brine is evaporated to precipitate potassium-magnesium mixed salt and then deboroned. Mg 2+ , Li + Precipitate in the form of hydroxide, carbonate, phosphate or oxalate respectively; the precipitate is calcined and decomposed, and through carbonization or carbonation, Li + into solution, Mg 2+ Still remain in the precipitation, so as to achieve the separation of magnesium and lithium, and then carry out deep removal of impurities on the lithium-rich solution, followed by evaporation and concentration or precipitation with soda ash to prepare lithium carbonate. This method is also very costly

The problem of this method is that diisobutyl ketone has high solubility in water, and the price is high, the iron salt recovery process is cumbersome, the extraction rate of lithium is low, and the extraction rate of seven-stage lithium is only about 80%.

Dipicrylamine and its derivatives, negative compounds, etc. are difficult to overcome due to many difficulties in themselves, so there are few applications in recent years, and the solvent extraction method uses a large amount of extraction solvent, and the extraction solvent has a large loss due to dissolution or reaction with strong acid and strong base. Directly cause high cost; the extraction process is long, graded and segmented, and it is difficult to realize automatic control; corrosion factor; direct contact between organic extractant and raw water will inevitably cause mixing, and the additional separation process is the weakness of the whole process

Therefore, although this method has obvious advantages over other methods in terms of recovery rate, it is difficult to realize industrialization.

[0015] Chinese patent CN93104780.3 discloses a method for separating and enriching rubidium in brine by ion exchange. The ion exchanger used is synthesized from copper nitrate and potassium ferricyanide. The rubidium-collected exchange column was soaked in dilute nitric acid and washed with H 2 O rinsing, the primary adsorption rate reaches 70%. This method cannot be used in large-scale production processes due to the high dissolution rate of reagents in brine and the limited saturation capacity of ion exchange capacity.

However, because this method needs to be operated under high temperature and high radioactivity conditions, the requirements for experimental equipment are high, the safety of the method is not good, and it is difficult to popularize and apply.

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