WO2017005113A1

WO2017005113A1 - Method for extracting lithium from salt lake brine

Info

Publication number: WO2017005113A1
Application number: PCT/CN2016/087443
Authority: WO
Inventors: 杨发平; 刘炳生
Original assignee: 青海恒信融锂业科技有限公司
Priority date: 2015-07-03
Filing date: 2016-06-28
Publication date: 2017-01-12
Also published as: CN104961143B; CN104961143A

Abstract

Provided is a method for separating and extracting lithium from brine, comprising: 1) acidification to remove boron: adding an acid to the brine to precipitate boric acid, and performing solid-liquid separation to obtain a first supernatant; 2) pre-treatment: removing a part of sulfate ions and magnesium ions from the first supernatant by precipitation, to obtain a second supernatant; 3) lithium-magnesium separation: separating lithium and magnesium in the second supernatant using a lithium-magnesium separation membrane, to obtain a high-magnesium and low-lithium produced water and a high-lithium and low-magnesium produced water; 4) lithium concentration: concentrating, using a lithium-concentration membrane, the high-lithium and low-magnesium produced water obtained in step 3), to obtain a concentrated solution and a diluted solution; and 5) lithium purification and precipitation: increasing a pH of the concentrated solution obtained in step 4), removing Mg²⁺ by precipitating Mg(OH)₂ to obtain a third supernatant, introducing CO₃ ^2- in the third supernatant to precipitate Li⁺ in the form of Li₂CO₃, and separating, rinsing and drying a precipitate to obtain a battery-grade lithium carbonate product.

Description

Method for extracting lithium from salt lake brine

Technical field

The present disclosure relates to the field of membrane separation technology, and more particularly to a method of extracting lithium from salt lake water in combination with a chemical precipitation method and a membrane separation method.

Background technique

In recent decades, humans have been striving to find new energy sources that can replace fossil energy. The most common way to use new energy sources is to convert various forms of energy into electrical energy for storage. Lithium-ion batteries are widely used in mobile communication equipment and various digital products because of their outstanding specific capacity, wide operating temperature range, low self-discharge rate, long cycle life and good safety performance. It is an ideal power source for electric vehicles. Therefore, even if the global economic growth slows down in recent years, the performance of the lithium industry is particularly prominent. Lithium products are one of the few industrial products with rising prices. Therefore, the acquisition of lithium resources has become a hot spot in the world.

Summary of the invention

Embodiments of the present invention provide a method for separating and extracting lithium from brine, comprising:

1) Acidizing and removing boron, adding acid to the brine, precipitating boric acid, separating solid and liquid to obtain the first clear liquid;

2) pretreatment, removing a portion of the sulfate and magnesium ions in the first supernatant by precipitation to obtain a second supernatant;

3) separating lithium and magnesium, separating lithium and magnesium in the second clear liquid by using a lithium magnesium separation membrane to obtain high magnesium low lithium water production water and high lithium low magnesium water production;

4) Lithium concentration, using the lithium concentrated membrane to concentrate the high lithium and low magnesium water produced in the step 3 to obtain a concentrated liquid and a light liquid;

5) Purifying the lithium, raising the pH of the concentrated liquid obtained in the step 4, removing Mg ²⁺ as a precipitate of Mg(OH) _{2 to} obtain a third clear liquid, and introducing CO ₃ ^2- into the third clear liquid. Li ⁺ was precipitated in the form of Li ₂ CO ₃ , and the precipitate was separated and washed to obtain a battery-grade lithium carbonate product.

In one embodiment of the present invention, for example, at least one of the high magnesium low lithium product water of the above step 3 and the light liquid of the step 4 may be returned to the second clear liquid of the step 2.

In one embodiment of the present invention, for example, step 2 of the pretreatment comprises steps 2A and 2B, and step 2A comprises: adjusting the pH of the first supernatant of step 1 to 7-9, SO ₄ in the brine A part of ^2- and Mg ²⁺ is precipitated in the form of calcium sulfate and magnesium hydroxide. After solid-liquid separation, clear liquid 2A is obtained, and the process proceeds to step 2B to continue the treatment or proceeds to step 3 to continue the treatment; step 2B includes: returning the supernatant with the subsequent step. After the combination, a portion of the remaining SO ₄ ^2- and Mg ²⁺ remaining in the brine continues to precipitate as calcium sulfate and magnesium hydroxide, and after solid-liquid separation, the supernatant 2B is obtained and proceeds to step 3 for further treatment.

In one embodiment of the present invention, for example, step 3 of lithium magnesium separation comprises step 3A and step 3B, step 3A comprises: adding acid to the supernatant obtained in step 2, adjusting the pH to 7-8.5, using lithium magnesium separation Membrane separation clear liquid obtains high magnesium and low lithium water production 3A and high lithium low magnesium water production 3A, wherein high magnesium and low lithium water production 3A is returned to the salt field for concentration and enrichment, and then combined with raw material brine, high lithium and low magnesium water production 3A Go to step 3B to continue the process or proceed to step 4 to continue the process; step 3B includes: adding a complexing agent to the high-lithium and low-magnesium water-producing water 3A, and separating the high-lithium and low-magnesium water-producing water 3A by using the lithium-magnesium separation membrane to obtain high-magnesium and low-lithium water-producing water. 3B and high-lithium and low-magnesium produced water 3B, wherein the high-magnesium-low-lithium product water 3B returns to the supernatant of step 2A, and the high-lithium low-magnesium produced water 3B proceeds to step 4 to continue the treatment.

In one embodiment of the present invention, for example, step 4 of lithium concentration includes step 4A, step 4B, and step 4C, and step 4A includes: concentrating the high-lithium and low-magnesium produced water of step 3 with a lithium concentration membrane to obtain a concentration. Liquid 4A and light liquid 4A, wherein the light liquid 4A returns to the clear liquid of step 2A, the concentrated liquid 4A proceeds to step 4B to continue the treatment or proceeds to step 5 to continue the treatment; step 4B includes: using the lithium concentrated membrane for the concentrated liquid of step 4A 4A is concentrated to obtain a concentrate 4B and a light liquid 4B, wherein the light liquid 4B is returned to be combined with the clear liquid of the step 2A, the concentrated liquid 4B is further advanced to the step 4C or the processing proceeds to the step 5; the step 4C includes: using the lithium concentrated film The concentrate 4B of the step 4B is concentrated to obtain a concentrate 4C and a light liquid 4C, wherein the light liquid 4C is returned to the supernatant of the step 2A, and the concentrate 4C is advanced to the step 5 to continue the treatment.

In one embodiment of the present invention, for example, the acid removal of the step 1 of the above step comprises: adding acid to adjust the pH of the salt lake brine to 2-4 to precipitate crystals of boric acid, solid-liquid separation to obtain a clear liquid and crude boric acid.

In one embodiment of the present invention, for example, the above step 2B comprises: adding a filter aid to the supernatant 2A, and combining the remaining supernatants of the subsequent steps, the remaining SO ₄ ^2- and Mg ²⁺ in the brine A part of the mixture was continuously precipitated in the form of calcium sulfate and magnesium hydroxide, and the CaSO ₄ and Mg(OH) ₂ flocs were separated by a polytetrafluoroethylene microfiltration membrane to obtain a clear liquid 2B, and the treatment was continued in step 3.

In one embodiment of the present invention, for example, the above-mentioned high magnesium and low lithium water production 3A lithium ion concentration The degree is less than 150ppm, the lithium ion concentration in the high lithium and low magnesium water production 3A is more than 300ppm; the lithium ion concentration in the high lithium and low magnesium water production 3B is more than 300ppm and the lithium to magnesium mass ratio is greater than 1.

In one embodiment of the present invention, for example, the concentration of lithium ions in the concentrated liquid 4A is greater than 1000 ppm and the mass ratio of lithium to magnesium is greater than 1; the concentration of lithium ions in the concentrated solution 4B is greater than 2000 ppm and the mass ratio of lithium to magnesium is greater than 1; The medium lithium ion concentration is greater than 16000 ppm and the lithium to magnesium mass ratio is greater than 1.

In one embodiment of the present invention, for example, in step 2A, the manner of adjusting the pH of the first supernatant of step 1 comprises adding NaOH, NH ₄ OH, KOH or Ca(OH) ₂ .

In one embodiment of the invention, for example, the filter aid is perlite, diatomaceous earth or cellulose, and the filter aid is added in an amount of 30-50 ppm.

In one embodiment of the present invention, for example, in step 3A, the acid added to the supernatant obtained in step 2 includes one of hydrochloric acid, sulfuric acid, nitric acid, or a combination thereof.

In one embodiment of the present invention, for example, in step 3B, the complexing agent added in the high lithium low magnesium product water 3A is a compound EDTA sodium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid. Salt, aminotrimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, hydroxyethylidene diphosphonic acid or sodium hexametaphosphate, at a concentration of 3-6 ppm.

In one embodiment of the present invention, for example, the method for obtaining the clear liquid in the step 5 is: adding sodium hydroxide to the concentrated liquid of the step 4 to obtain a slurry, and a part of the Mg ²⁺ in the slurry is Mg ( Precipitation in the form of OH) ₂ , solid-liquid separation of the above slurry to obtain magnesium hydroxide precipitate and a leachate, magnesium hydroxide precipitation and more than one leaching with water or filtrate, solid-liquid separation to obtain magnesium hydroxide precipitate and filtrate, This filtrate was used to configure sodium hydroxide to continue to be reused, and a leachate was filtered to obtain a clear solution.

In one embodiment of the present invention, for example, the method of solid-liquid separation includes high speed centrifugation, plate and frame solid-liquid separation, polytetrafluoroethylene microfiltration membrane separation and/or filtration.

DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below. It is obvious that the drawings in the following description relate only to some embodiments of the present invention, and are not intended to limit the present invention. .

1 is a flow chart of a method for separating and extracting lithium from brine in accordance with an embodiment of the present invention;

2 is a flow chart of a method for separating and extracting lithium from brine in accordance with still another embodiment of the present invention. Figure

3 is a flow chart of a method for separating and extracting lithium from brine according to a third embodiment of the present invention;

4 is a flow chart of a method for separating and extracting lithium from brine in accordance with a fourth embodiment of the present invention.

detailed description

The technical solutions of the embodiments of the present invention will be clearly and completely described in the following with reference to the accompanying drawings. It is apparent that the described embodiments are part of the embodiments of the invention, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the described embodiments of the present invention without departing from the scope of the invention are within the scope of the invention.

Unless otherwise defined, technical terms or scientific terms used herein shall be taken to mean the ordinary meaning of the ordinary skill in the art to which the invention pertains. The words "first", "second" and similar terms used in the specification and claims of the present invention do not denote any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the words "a" or "an" and the like do not denote a quantity limitation, but mean that there is at least one.

Unless otherwise defined, ppm is a mass ratio, and Chinese has the same meaning as chemical formula, such as magnesium ion and Mg ²⁺ , sulfate ion and SiO ₄ ^2- .

Among the proven lithium resources in the world, lithium brine resources accounted for 61%, ore lithium resources accounted for 34%, and oil and geothermal water lithium resources accounted for 5%. As far as the current economic and technological status quo is concerned, lithium extraction from salt lake brines is superior to ore extraction in terms of cost and scale. 70% of the world's lithium products come from salt lake brines. China's salt lake brine lithium accounted for more than 80% of the total reserves, however, lithium extracted from salt lake brines only accounted for 8% of the total extraction, for a variety of reasons. The main reason is that China's salt lake brine is mostly high-magnesium-lithium brine. Because Mg ²⁺ and Li ⁺ are very similar in physicochemical properties, it is difficult to separate magnesium and lithium, and it is impossible to use simple chemical methods (such as precipitation method). The direct extraction of lithium, the current methods for extracting lithium from high magnesium lithium than brine include organic solvent extraction, ion exchange, electrodialysis, nanofiltration membrane and the like. The organic solvent extraction method has high production cost and serious corrosion to equipment, and is still in the experimental stage; the adsorbent used in the ion exchange method has high price, low productivity, and is easily contaminated, and cannot be mass-produced; the electrodialysis method requires a large amount of consumption. Electrical energy, and a large amount of toxic chlorine gas is produced in the production process; the nanofiltration membrane method has great advantages over the above methods. In principle, the nanofiltration membrane is a pressure-driven membrane with a charged group on the membrane, which produces a Donnan effect through electrostatic interaction, and has different selective permeability to ions of different valence states. Separation of different valence ions. In general, the nanofiltration membrane has a rejection rate of monovalent ions of 10% to 80%, and has a relatively high permeability, while the retention rates of both divalent and polyvalent salts are above 90%, thereby realizing monovalent lithium ions and Separation of divalent magnesium ions. Domestic companies have used this technology to extract lithium from salt lake brines, but there are still some problems that lead to low production efficiency and high cost.

There are several nanofiltration membranes in the field for separating and extracting lithium from brine. Chinese Patent Application No. 0310808088.X of Qinghai Lake Research Institute of Chinese Academy of Sciences separates magnesium and enriched lithium from salt lake brine through commercial multi-stage nanofiltration membrane. However, the brine does not remove impurity ions such as sulfate and borate before entering the nanofiltration membrane, resulting in low membrane separation efficiency, and the pores of the nanofiltration membrane are often clogged by flocculent precipitates during use, affecting production and increasing costs. The lithium-rich brine obtained by using this technology can not reach the concentration and purity of practical industrial applications; Wang Hui's Chinese Patent Application No. 201010295933.X first dilutes the high-salt raw material brine with water, and then passes the first or more stages. The membrane separates magnesium and lithium and is finally concentrated by a reverse osmosis membrane or membrane distillation system. This technique also does not take into account the influence of ions other than magnesium on the separation process. The membrane separation efficiency is not high, and the method also uses a nanofiltration membrane. In multiple stages of series, the next stage of concentrated water returns to the upper stage feed, which leads to an increase in the magnesium to lithium ratio and a decrease in membrane separation efficiency.

For the above problems existing in the prior art, embodiments of the present invention provide a comprehensive lithium ion (Li ⁺ ) extraction method combining a chemical reagent method, a physical impurity removal method, a nanofiltration membrane separation method, a concentrated membrane method, and the like. In the method, other impurities such as Mg ²⁺ , SO ₄ ^2- , B ^{2+ ,} etc. existing in the salt lake brine are removed before the membrane separation by a method other than the membrane separation method such as a chemical method or a physical impurity removal method. It creates favorable conditions for membrane separation, greatly improves membrane separation efficiency, and optimizes separation effect; in the membrane separation process and after membrane separation, the above method is also combined to further improve the efficiency and purity of lithium extraction. Before the advent of the present invention, the extraction of lithium from a salt lake by a membrane separation method can generally only reach the industrial grade, and due to the presence of a large amount of impurity ions, a large amount of precipitation often occurs in the membrane separation process to cause fouling of the membrane, which affects the production progress on the one hand. On the other hand, it also increases production costs. By extracting lithium from salt lake brine by the method of the invention, the purity of the battery can be achieved, and a large amount of impurity ions are removed before the membrane separation, and the fouling problem in the membrane separation process is also solved, which greatly prolongs the production cycle. , reducing production costs.

It should be noted that, herein, the "high magnesium and low lithium water production" in the lithium magnesium separation step does not mean The concentration of magnesium is higher than that of lithium, and “high lithium and low magnesium water production” does not mean that the concentration of lithium is higher than that of magnesium, but in the same step (such as step 3A), “high magnesium and low lithium water production” The lithium to magnesium ratio (mass ratio) is lower than the lithium to magnesium ratio (mass ratio) in "high lithium and low magnesium water production".

Example 1

As shown in Figure 1, the feedstock is a lithium-containing brine from a salt lake or a lithium-containing brine from other sources. The salt lake brine used in the examples of the present invention is a salt lake brine with a high magnesium to lithium ratio, and the magnesium to lithium ratio (Mg ²⁺ : Li ⁺ mass ratio) is generally above 20.

Acid is added to the raw material brine to adjust the pH of the brine to 2-4 to precipitate crystals of boric acid, and solid-liquid separation is carried out to obtain a clear liquid and crude boric acid. The crude boric acid can be further processed for sale, and the supernatant is passed to step 2 for pretreatment.

In the pretreatment step, some sulfate and magnesium ions in the brine are removed by precipitation (the sulfate removal rate is about 90%, the magnesium ion removal rate is about 10-15%), the solid-liquid separation, and the clear liquid proceeds to the next step. deal with. The manner of precipitation includes a conventional chemical or physical precipitation method such as adding a lye to precipitate magnesium ions in the form of magnesium hydroxide, adding cerium ions to precipitate sulfate ions, or changing the temperature of the solution so that the solubility of calcium sulfate is changed to precipitate or the like.

The lithium magnesium separation membrane is used to separate the lithium liquid from the supernatant of the pretreatment step to obtain high magnesium low lithium water production and high lithium low magnesium water production, wherein high lithium and low magnesium water production proceeds to the next step to continue processing. The lithium ion content in the high lithium and low magnesium produced water is greater than 300 PPM, and the lithium magnesium mass ratio is greater than 1:1. The lithium magnesium separation membrane may employ a nanofiltration membrane that can separate monovalent ions and divalent ions. The nanofiltration membrane is a pressure-driven membrane. Because of the charged groups on the membrane or in the membrane, the Donnan effect is generated by electrostatic interaction, and the ions of different valence states have different selectivity, thereby achieving different prices. Separation of state ions. Commercially available lithium-magnesium separation membranes have been available in the art, and companies such as Membrane Products, Nitto, and Osmonics have related product lines. Of course, the above process provided by the embodiments of the present invention can also utilize a lithium-magnesium separation membrane prepared by itself.

The high-lithium and low-magnesium produced water obtained in the previous step is concentrated to obtain a concentrated liquid and a light liquid, and the concentrated liquid is further processed in the next step. The method of concentration can use a lithium concentrated membrane to treat high lithium and low magnesium water. The lithium concentrated membrane is generally a reverse osmosis membrane, and a commercial product such as Dow, KOCH, HYDRANAUTICS, GE, TORAY, and the like can be used. The above process provided by the embodiments of the present invention can also utilize a self-prepared lithium concentrated film. The concentration of lithium in the concentrate obtained by concentration is greater than 16000 PPM, and the mass ratio of lithium to magnesium is greater than 1:1.

Purifying the lithium, raising the pH of the concentrate in the previous step, removing Mg ²⁺ as a precipitate of Mg(OH) _{2 to} obtain a clear liquid, introducing CO ₃ ^2- in the clear liquid, and Li ⁺ as Li ₂ CO Precipitate in the form of ₃ , the precipitate was separated and washed and dried to obtain a battery grade lithium carbonate product with a purity of >99.5%.

Example 2

As shown in FIG. 2, another embodiment of the present invention provides a method for separating and extracting lithium from brine. Compared with the method provided in Embodiment 1, the method provided by the embodiment has more subdivided steps, including :

1) Acidizing and removing boron, the clear liquid proceeds to the next step to continue processing;

2) pretreatment to remove a portion of the sulfate and magnesium ions in the brine by precipitation; the pretreatment step 2 comprises a step 2A and a step 2B, the step 2A comprising: raising the pH of the supernatant of the step 1 to adjust the pH to 7-9 a part of SO ₄ ^2- and Mg ²⁺ in the brine is precipitated in the form of calcium sulfate and magnesium hydroxide, and after the solid-liquid separation, the supernatant 2A is obtained, and the treatment is continued in step 2B; the step 2B includes: adding the auxiliary in the clear solution 2A A filter (such as a homogenous perlite, added in an amount of 30-50 ppm), a portion of the remaining SO ₄ ^2- and Mg ²⁺ remaining in the brine continues to precipitate as calcium sulfate and magnesium hydroxide, and a solid solution is obtained to obtain a clear liquid. 2B proceeds to step 3 to continue processing.

3) Lithium and magnesium separation, lithium and magnesium separation membrane is used to separate lithium and magnesium to obtain high magnesium low lithium water production and high lithium low magnesium water production; step 3 includes step 3A and step 3B, step 3A includes: clear liquid obtained in step 2B Adding acid, adjusting the pH to 7-8.5, separating the clear liquid by lithium-magnesium separation membrane to obtain high-magnesium low-lithium water production 3A and high-lithium low-magnesium water production 3A, high-lithium low-magnesium production water 3A proceeds to step 3B to continue the treatment; 3B includes: adding a complexing agent to the high-lithium and low-magnesium water-producing water 3A (the complexing agent may be a scale inhibitor commonly used in the field of water treatment, for example, it may be a compound of EDTA sodium salt, ethylenediaminetetraacetic acid, and ethylene. Amine tetraacetate, aminotrimethylenephosphonic acid, diethylene triamine penta methylene phosphonic acid, hydroxyethylidene diphosphonic acid or sodium hexametaphosphate, at a concentration of 3-6 ppm), separated by a lithium magnesium separation membrane High lithium and low magnesium water production 3A to obtain high magnesium and low lithium water production 3B and high lithium low magnesium water production 3B, high lithium and low magnesium water production 3B to proceed to step 4 to continue processing.

4) Lithium concentration, using a lithium concentrated membrane to concentrate the high-lithium and low-magnesium water produced in the step 3, to obtain a concentrated liquid and a light liquid, wherein the concentrated liquid proceeds to the next step to continue the treatment; the step 4 of the lithium concentration includes the step 4A, the step 4B and Step 4C, step 4A comprises: concentrating the high-lithium and low-magnesium produced water of step 3 by using a lithium concentrated membrane to obtain concentrated liquid 4A and light liquid 4A, and the concentrated liquid 4A proceeds to step 4B to continue processing; Step 4B includes: concentrating the concentrated liquid 4A of the step 4A with a lithium concentrated membrane to obtain a concentrated liquid 4B and a light liquid 4B, and the concentrated liquid 4B proceeds to the step 4C for further processing; and the step 4C includes: using the lithium concentrated film for the concentrated liquid of the step 4B 4B is concentrated to obtain a concentrate 4C and a light liquid 4C, and the concentrate 4C is advanced to the step 5 to continue the treatment.

5) Purifying the lithium, raising the pH of the concentrated liquid of the step 4, removing Mg ²⁺ as a precipitate of Mg(OH) _{2 to} obtain a clear liquid, introducing CO ₃ ^2- in the clear liquid, and Li ⁺ as Li ₂ The form of CO ₃ precipitated, the precipitate was separated and dried to obtain a battery grade lithium carbonate product having a purity of >99.7%. The method for obtaining the supernatant is as follows: adding sodium hydroxide to the concentrated liquid of the step 4 to obtain a slurry, in which part of Mg ²⁺ is precipitated as Mg(OH) ₂ , and the slurry is solid-liquid separated. Magnesium hydroxide precipitation and a leachate, magnesium hydroxide precipitation and more than one leaching with water or filtrate, solid-liquid separation to obtain magnesium hydroxide precipitate and filtrate, the filtrate is used to dispose sodium hydroxide solution, a leachate Filter to obtain a clear solution.

The above method provided in Example 2 has more subdivision steps, on the one hand, the lithium-magnesium separation effect is better, and the purity of the final product lithium carbonate is also higher; on the other hand, the removal of the precipitate in the brine is more thorough and reduced. The fouling condition in the membrane separation process makes the continuous operation of the method greatly extended, and the automation degree of the whole process is improved. Taking pretreatment step 2 as an example, using two pretreatment steps of 2A and 2B, the sulfate ion and magnesium ion in the brine can be reduced more, the precipitate entering the next step is reduced, and the membrane separation is reduced. The probability of fouling in the process is conducive to the subsequent separation of lithium and magnesium. It should be noted that steps 2, 3, and 4 do not need to be subdivided at the same time, and some steps may be subdivided according to actual needs, and other steps are completed in one step. The lithium carbonate finally obtained in this example has a purity of >99.6%.

Example 3

As shown in FIG. 3, another embodiment of the present invention provides a method for separating and extracting lithium from brine. Compared with the method provided in Embodiment 2, the method provided in this embodiment recovers the Li ⁺ content produced in each step. A low solution to increase the overall lithium ion extraction rate. The same contents as in Embodiment 2 in the present embodiment will be omitted, and the different portions will be mainly described. As shown in FIG. 3, the high magnesium and low lithium water produced in step 3A is returned to the salt field for concentration and enrichment, and then combined with the raw material brine, and the high magnesium and low lithium produced water 3B obtained in step 3B is returned to be combined with the clear liquid of step 2A. The light liquid 4A obtained in the step 4A is returned to the clear liquid in the step 2A, the light liquid 4B obtained in the step 4B is returned to be combined with the clear liquid in the step 2A, and the light liquid 4C obtained in the step 4C is returned to be combined with the clear liquid in the step 2A. Since the solution with lower Li ⁺ content produced in each step is recycled, the extraction rate of Li ^{+ in the} brine is improved from 40% to over 80%. It should be noted that the above-mentioned solution with a lower Li ⁺ content does not need to be simultaneously recovered, and in actual production, a part of the recycling can be reasonably selected according to the situation, taking into consideration the cost and the lithium ion extraction rate. The purity of lithium carbonate finally obtained in this embodiment is >99.7%, and the recovery rate of lithium in brine is above 80%.

Example 4

As shown in FIG. 4, another embodiment of the present invention provides a method for separating and extracting lithium from brine. Compared with the method provided in Embodiment 3, the method provided in the embodiment adds an auxiliary agent to further optimize each The processing effect of the steps. The same contents as those of the foregoing embodiments in the present embodiment will be omitted, and the different portions will be mainly described. As shown in FIG. 4, step 2A includes raising the pH of the supernatant of step 1 to 7-9, and a part of SO ₄ ^2- and Mg ²⁺ in the brine is precipitated as calcium sulfate and magnesium hydroxide. The method of raising the pH includes, but is not limited to, adding NaOH, KOH, Ca(OH) ₂ or ammonia water to the solution, forming a precipitate and separating by solid-state centrifugation or plate-and-frame solid-liquid separation, and the solid matter can be further treated as a raw material of the magnesium product. An increase in pH promotes the removal of magnesium, which removes 20 to 30% of magnesium.

As shown in Figure 4, a filter aid was introduced in Pretreatment 2B. A filter aid such as homogenous perlite is added to the clear liquid 2A in an amount of 30-50 ppm, and a part of the remaining SO ₄ ^2- and Mg ²⁺ in the brine is continuously precipitated in the form of calcium sulfate and magnesium hydroxide. The polytetrafluoroethylene microfiltration membrane separates the CaSO ₄ and Mg(OH) ₂ flocs to obtain the supernatant 2B, and proceeds to step 3 to continue the treatment. A filter aid is a substance that increases the filtration efficiency of the filtrate. In general, in order to prevent the filter residue from being too dense and the filtration to proceed smoothly, the filter aid may be an insoluble inert material having a different degree of fineness. Examples of the above filter aids in the present invention include, but are not limited to, perlite, diatomaceous earth, cellulose, and the like.

As shown in Figure 4, a complexing agent can be introduced in step 3B. Adding a complexing agent to the high-lithium and low-magnesium water-producing water 3A, such as compounding EDTA sodium salt, 3-6ppm, separating high-lithium and low-magnesium water-producing water 3A by using a lithium-magnesium separation membrane to obtain high-magnesium-low-lithium water-producing water 3B and high-low lithium Magnesium produced water 3B, in which high magnesium and low lithium produced water 3B returns with the clear liquid of step 2A, and high lithium low magnesium produced water 3B proceeds to step 4 to continue processing. The above complexing agent functions to complex with calcium, barium, strontium, etc., and prevents calcium sulfate, calcium carbonate, barium sulfate, barium sulfate and the like from scaling on the surface of the film to cause damage to the film. Examples of the above complexing agent in the present invention include, but are not limited to, a compound of EDTA sodium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, aminotrimethylenephosphonic acid, diethylenetriaminepentamethylphosphonic acid. , hydroxyethylidene diphosphonic acid or sodium hexametaphosphate.

The above is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims.

The present application claims the priority of the Chinese Patent Application No. 201510392024.0 filed on Jul. 3, 2015, the entire disclosure of which is hereby incorporated by reference.

Claims

A method for separating and extracting lithium from brine, comprising:

1) Acidizing and removing boron, adding acid to the brine, precipitating boric acid, and then performing solid-liquid separation to obtain a first clear liquid;

2) pretreatment, removing a portion of the sulfate and magnesium ions in the first supernatant by precipitation to obtain a second supernatant;

3) separating lithium and magnesium, separating lithium and magnesium in the second clear liquid by using a lithium magnesium separation membrane to obtain high magnesium low lithium water production water and high lithium low magnesium water production;

4) Lithium concentration, using the lithium concentrated membrane to concentrate the high lithium and low magnesium water produced in the step 3 to obtain a concentrated liquid and a light liquid;

5) Purifying the lithium, raising the pH of the concentrated liquid obtained in the step 4, removing Mg 2+ as a precipitate of Mg(OH) 2 to obtain a third clear liquid, and introducing CO 3 2 into the third clear liquid. - , Li + precipitates in the form of Li 2 CO 3 , and the precipitate is separated and washed to obtain a battery-grade lithium carbonate product.
The method according to claim 1, wherein at least one of the high magnesium low lithium product water of step 3 and the light liquid of step 4 is returned to be combined with the second liquid of step 2.
The method according to claim 1 or 2, wherein step 2 comprises step 2A and step 2B,

Step 2A includes: adjusting the pH of the first supernatant of step 1 to 7-9 so that a part of SO 4 2- and Mg 2+ in the brine is precipitated in the form of calcium sulfate and magnesium hydroxide. After the solid-liquid separation, the clear liquid 2A is obtained, and the clear liquid 2A is advanced to the step 2B to continue the treatment or the third step is continued;

Step 2B includes: a part of SO 4 2- and Mg 2+ remaining in the brine continues to precipitate as calcium sulfate and magnesium hydroxide, and after solid-liquid separation, clear liquid 2B is obtained, and the clear liquid 2B is advanced to step 3 for further treatment. .
The method of claim 3 wherein step 3 comprises steps 3A and 3B,

Step 3A includes: adding acid to the clear liquid obtained in step 2, adjusting the pH to 7-8.5, separating the clear liquid by using the lithium magnesium separation membrane to obtain high magnesium and low lithium water production 3A and high lithium low magnesium water production 3A, wherein After the high magnesium and low lithium water production 3A is returned to the salt field for concentration and enrichment, it is combined with the raw material brine, and the high lithium low magnesium water production 3A proceeds to step 3B to continue the treatment or proceeds to step 4 to continue the treatment;

Step 3B includes: adding a complexing agent to the high-lithium low-magnesium water-producing water 3A, and separating the high-lithium low-magnesium water-producing water 3A by using the lithium-magnesium separation membrane or the new lithium-magnesium separation membrane in the step 3A to obtain a high Magnesium low lithium produced water 3B and high lithium low magnesium produced water 3B, wherein the high magnesium low lithium produced water 3B is returned to be combined with the clear liquid of step 2A, and the high lithium low magnesium produced water 3B is further processed in step 4.
The method of claim 3, wherein step 4 comprises step 4A, step 4B, and step 4C,

Step 4A includes: concentrating the high-lithium low-magnesium product water of step 3 with the lithium concentration membrane to obtain a concentrate 4A and a light liquid 4A, wherein the light liquid 4A is returned to be combined with the clear liquid of step 2A, and the concentration is Liquid 4A proceeds to step 4B to continue processing or proceeds to step 5 to continue processing;

Step 4B includes: concentrating the concentrated liquid 4A of the step 4A by using the lithium concentrated film or the new lithium concentrated film in the step 4A to obtain a concentrated liquid 4B and a light liquid 4B, wherein the light liquid 4B returns to the clearing of the step 2A. The liquid is combined, and the concentrated liquid 4B proceeds to step 4C to continue the treatment or proceeds to step 5 to continue the treatment;

Step 4C includes: concentrating the concentrated liquid 4B of the step 4B by using the lithium concentrated film in the step 4A or the lithium concentrated film in the step 4B or a new lithium concentrated film to obtain a concentrated liquid 4C and a light liquid 4C, wherein the The light liquid 4C returns to the supernatant of step 2A, and the concentrated liquid 4C proceeds to step 5 to continue the treatment.
The method according to claim 1 or 2, wherein, in the step 1, the acid is added to adjust the pH of the brine to 2-4 to precipitate the boric acid crystal, and then the solid-liquid separation is performed to obtain the first A clear solution and crude boric acid.
The method according to claim 3, wherein in said step 2B, a filter aid is added to said supernatant 2A, and then combined with the supernatant returned in the subsequent step, the remaining SO 4 in the obtained treatment liquid is obtained. A part of 2- and Mg 2+ continues to precipitate in the form of calcium sulfate and magnesium hydroxide, and then the precipitated calcium sulfate and magnesium hydroxide floe are separated by a polytetrafluoroethylene microfiltration membrane to obtain a clear liquid 2B. Step 3 continues processing.
The method according to claim 4, wherein the lithium ion concentration in the high magnesium low lithium product water 3A is less than 150 ppm, and the lithium ion concentration in the high lithium low magnesium product water 3A is greater than 300 ppm; the high lithium low magnesium product The lithium ion concentration in water 3B is greater than 300 ppm and the lithium to magnesium mass ratio is greater than 1.
The method according to claim 5, wherein the concentration of lithium ions in the concentrated solution 4A is greater than 1000 ppm and the mass ratio of lithium to magnesium is greater than 1; and the concentration of lithium ions in the concentrated solution 4B is greater than 2000 ppm. And the lithium magnesium mass ratio is greater than 1; the concentration of lithium ions in the concentrate 4C is greater than 16000 ppm and the mass ratio of lithium to magnesium is greater than 1.
The method according to claim 3, wherein in the step 2A, the manner of adjusting the pH of the first supernatant of the step 1 comprises adding NaOH, NH 4 OH, KOH or Ca(OH) 2 .
The method according to claim 7, wherein the filter aid is perlite, diatomaceous earth or cellulose, and the filter aid is added in an amount of 30 to 50 ppm.
The method according to claim 4, wherein in the step 3A, the acid added to the supernatant obtained in the step 2 comprises one of hydrochloric acid, sulfuric acid, nitric acid or a combination thereof.
The method according to claim 4, wherein in step 3B, the complexing agent added in the high lithium low magnesium product water 3A comprises a compound of EDTA sodium salt, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate. Aminotrimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, hydroxyethylidene diphosphonic acid or sodium hexametaphosphate, the complexing agent having a concentration of 3-6 ppm.
The method according to claim 1 or 2, wherein in step 5, sodium hydroxide is added to the concentrate of step 4 to obtain a slurry, and a part of Mg 2+ in the slurry is Mg(OH) 2 . In the form of precipitation, the slurry is subjected to solid-liquid separation to obtain magnesium hydroxide precipitate and immersion liquid, and the immersion liquid is filtered to obtain the third supernatant.
The method according to claim 14, wherein the magnesium hydroxide is precipitated and then subjected to more than one leaching with water or an immersion liquid, and solid-liquid separation is carried out to obtain a magnesium hydroxide precipitate and a filtrate, and the filtrate is used for arranging hydrogen hydroxide. Sodium continues to be reused.
The method according to claim 1 or 2, wherein the method of solid-liquid separation comprises high-speed centrifugation, plate and frame solid-liquid separation, polytetrafluoroethylene microfiltration membrane separation and/or filtration.