CN112209412A - Method for extracting lithium and battery-grade lithium hydroxide monohydrate - Google Patents
Method for extracting lithium and battery-grade lithium hydroxide monohydrate Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/02—Oxides; Hydroxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2006/80—Compositional purity
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
- C01P2006/82—Compositional purity water content
Abstract
The present disclosure relates to a method for extracting lithium and a battery grade lithium hydroxide monohydrate, the method comprises the following steps: carrying out impurity removal and concentration treatment on lithium-containing brine to obtain a lithium-rich concentrated solution; carrying out bipolar membrane alkali preparation treatment on the lithium-rich concentrated solution to obtain mixed alkali liquor and hydrochloric acid solution; carrying out evaporation crystallization treatment on the mixed alkali liquor to obtain an evaporation crystallization precipitate and an evaporation crystallization end point mother liquor; subjecting the evaporated and crystallized precipitate to a first dissolution recrystallization treatment to obtain a first recrystallized precipitate and a first recrystallization mother liquor; subjecting the first recrystallized precipitate to a second dissolution recrystallization treatment to obtain lithium hydroxide monohydrate and a second recrystallization mother liquor; the method disclosed by the invention can be used for preparing high-purity battery-grade lithium hydroxide monohydrate, and has a high recovery rate of lithium ions.
Description
Technical Field
The disclosure relates to the field of lithium ion extraction, in particular to a method for extracting lithium and battery-grade lithium hydroxide monohydrate.
Background
In recent years, the rapid development of new energy industries has greatly stimulated the demand for upstream lithium resources. The battery-grade lithium hydroxide monohydrate and lithium carbonate are used as main raw materials for synthesizing the ternary positive electrode material and the lithium iron phosphate material of the lithium ion battery, and the demand of the lithium iron phosphate ternary positive electrode material is greatly increased.
At present, lithium salt products in China are mainly obtained by extracting lithium from lithium ore and extracting lithium from salt lake brine, the lithium extraction technology by the lithium ore method is long in development time and relatively mature in technology, then the resource reserve of lithium ore in China is very limited, and the ever-increasing market demand cannot be met by simply depending on lithium ore. The salt lake brine in China contains abundant lithium resources and has great exploitation value, so that the heat of extracting lithium from the salt lake brine is higher and higher in recent years. However, since the starting is late and the technology is relatively lagged, the content of impurities of the lithium hydroxide monohydrate or the lithium carbonate extracted from the salt lake brine is high, and the battery grade standard is difficult to achieve. Lithium carbonate produced by the prior art can only reach the industrial grade and cannot be used as lithium salt for preparing the anode material of the lithium ion battery, so that the value of the lithium carbonate is greatly reduced. At present, the technology for extracting the lithium hydroxide monohydrate from the salt lake brine is more lagged, and the technical route is not mature, mainly because the sodium ions and the potassium ions in the salt lake brine are difficult to remove, so that the sodium ions and the potassium ions in the product exceed the standard and cannot reach the battery grade standard. In addition, the recovery rate of lithium resources is low by the existing lithium extraction technology, so that the lithium resources are greatly wasted, and the production cost is high.
Disclosure of Invention
The purpose of the present disclosure is to provide a method for extracting lithium and a battery-grade lithium hydroxide monohydrate, in order to overcome the problems of low purity of lithium hydroxide monohydrate and lithium carbonate and low lithium ion yield when lithium hydroxide monohydrate and lithium carbonate are prepared from salt lake brine in the prior art.
In order to achieve the above object, a first aspect of the present disclosure provides a method for extracting lithium, including the steps of:
s1, carrying out impurity removal and concentration treatment on the lithium-containing brine to obtain a lithium-rich concentrated solution;
s2, performing bipolar membrane alkali preparation treatment on the lithium-rich concentrated solution to obtain mixed alkali liquor and a hydrochloric acid solution;
s3, carrying out evaporation crystallization treatment on the mixed alkali liquor to obtain an evaporation crystallization precipitate and an evaporation crystallization end point mother liquor;
s4, subjecting the evaporation crystallization precipitate to a first dissolution recrystallization treatment to obtain a first recrystallization precipitate and a first recrystallization mother liquor;
s5, subjecting the first recrystallized precipitate to a second dissolution recrystallization treatment to obtain lithium hydroxide monohydrate and a second recrystallization mother liquor.
Optionally, the impurity removal and concentration treatment includes: and contacting the lithium-containing brine with a lithium adsorbent to carry out impurity removal and concentration treatment, and then sequentially carrying out membrane separation and concentration treatment and resin separation treatment.
Alternatively, the lithium adsorbent used in the concentration treatment contains xLiCl.2Al (OH)3·nH2O, wherein, 0.2<x<1.2，0<n<2; based on the total volume of the lithium-containing brine, the dosage of the lithium adsorbent is 30-150 g/L;
the membrane separation concentration treatment sequentially comprises two-stage nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment; or the membrane separation concentration treatment sequentially comprises primary nanofiltration treatment, reverse osmosis treatment, secondary nanofiltration treatment and electrodialysis treatment; or the membrane separation concentration treatment sequentially comprises the primary nanofiltration treatment, the secondary nanofiltration treatment and the high-pressure reverse osmosis treatment; or the membrane separation concentration treatment sequentially comprises the primary nanofiltration treatment, the high-pressure reverse osmosis treatment and the secondary nanofiltration treatment;
the adsorption resin used in the resin separation treatment comprises one or more of strong-acid cation type resin, weak-acid cation type resin and chelate type ion exchange resin.
Optionally, the concentration of calcium ions in the lithium-rich concentrated solution is lower than 1ppm, the concentration of magnesium ions is lower than 1ppm, the concentration of lithium ions is 5000-10000ppm, the concentration of sodium ions is 3000-6500ppm, and the concentration of potassium ions is 1200-2400 ppm.
Optionally, the membrane current of the bipolar membrane alkali preparation treatment is 400-1000A/m2The voltage of the single pair of membranes is 0.5-3V.
Optionally, the method further comprises: returning the second recrystallization mother liquor to step S4 to mix with the evaporative crystallization educt to perform the first dissolution recrystallization treatment; and/or the presence of a gas in the gas,
and returning the first recrystallization mother liquor to the step S3 to be mixed with the mixed alkali liquor, and performing the evaporative crystallization treatment.
Optionally, the temperature of the evaporative crystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the evaporative crystallization end point mother liquor is 6-11 wt% and the concentration of potassium ions in the evaporative crystallization end point mother liquor is 3-7 wt% based on the total weight of the evaporative crystallization end point mother liquor;
the temperature of the first dissolution recrystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the first recrystallization mother liquor is 2-6 wt% and the concentration of potassium ions in the first recrystallization mother liquor is 1-3 wt% based on the total weight of the first recrystallization mother liquor;
the temperature of the second dissolution recrystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the second recrystallization mother liquor is 0.1-2 wt% and the concentration of potassium ions in the second recrystallization mother liquor is 0-1 wt% based on the total weight of the second recrystallization mother liquor.
Optionally, the method further comprises: and carrying out carbonization lithium precipitation treatment on the evaporation crystallization end point mother liquor to obtain lithium carbonate.
Optionally, the lithium carbide precipitation treatment comprises: cooling the evaporation crystallization end point mother liquor to separate out sodium hydroxide/potassium hydroxide, then carrying out centrifugal separation, carrying out contact reaction on the obtained separation mother liquor and a carbon source to obtain lithium carbonate precipitate, and carrying out optional washing treatment on the lithium carbonate precipitate to obtain the lithium carbonate;
the temperature of the carbonization lithium precipitation treatment is 60-100 ℃, and the precipitation rate of the lithium carbonate is 2-150 g/h;
the carbon source contains carbon dioxide and/or sodium carbonate.
In a second aspect of the present disclosure, a battery grade lithium hydroxide monohydrate prepared by the method provided in the first aspect of the present disclosure is provided.
Through the technical scheme, the method disclosed by the invention can reduce the concentration of sodium ions and potassium ions in the mother liquor at the crystallization end point through two times of dissolution and recrystallization treatments, and effectively inhibit the crystallization precipitation of Na/K ions, so that the content of Na/K impurities in the extracted lithium hydroxide monohydrate can be reduced, and the purity of the lithium hydroxide monohydrate can be effectively improved. The method disclosed by the invention can be used for extracting high-purity battery-grade lithium hydroxide monohydrate from lithium-containing brine, is far higher than the lithium hydroxide prepared by the method in the prior art, is low in production cost and is easy to industrialize.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Detailed Description
The following describes in detail specific embodiments of the present disclosure. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
In a first aspect of the present disclosure, there is provided a process for preparing lithium hydroxide monohydrate and lithium carbonate from a lithium-containing brine, the process comprising the steps of:
s1, carrying out impurity removal and concentration treatment on the lithium-containing brine to obtain a lithium-rich concentrated solution;
s2, performing bipolar membrane alkali preparation treatment on the lithium-rich concentrated solution to obtain mixed alkali solution and hydrochloric acid solution;
s3, carrying out evaporation crystallization treatment on the mixed alkali liquor to obtain an evaporation crystallization precipitate and an evaporation crystallization end point mother liquor;
s4, subjecting the evaporation crystallization precipitate to a first dissolution recrystallization treatment to obtain a first recrystallization precipitate and a first recrystallization mother liquor;
s5, subjecting the first recrystallized precipitate to a second dissolution recrystallization treatment to obtain lithium hydroxide monohydrate and a second recrystallization mother liquor.
The method disclosed by the invention can effectively improve the purity of the lithium hydroxide monohydrate prepared from the lithium-containing brine by combining two times of dissolving and recrystallization treatments, wherein the purity can reach 99.0-99.8%, and the method is simple, low in production cost and easy to industrialize. Specifically, the concentration of Na/K ion impurities in the mother liquor at the crystallization end can be reduced by carrying out twice dissolving and recrystallization treatments on evaporated and crystallized precipitates, and the Na/K ion impurities caused by the adhesion of the mother liquor can be effectively reduced under the condition of a certain mother liquor adhesion amount, so that the content of Na/K ions in the lithium hydroxide monohydrate of the crystallized product is lower, and the lithium hydroxide monohydrate reaches the battery-level standard.
According to the present disclosure, the impurity removal concentration treatment may be conventional in the art, and for example, includes one or more of an adsorption impurity removal concentration treatment, a membrane separation concentration treatment, and a resin separation concentration treatment. Preferably, the impurity removal concentration process may include: the lithium-containing brine is contacted with a lithium adsorbent to carry out adsorption, impurity removal and concentration treatment, and then membrane separation and concentration treatment and resin separation treatment are sequentially carried out. Through the concentration treatment process, the lithium-containing brine can be subjected to deep impurity removal to remove calcium ions and magnesium ions, and the concentration of the lithium ions is improved, so that the impurities of the calcium ions and the magnesium ions are effectively prevented from being brought into the lithium hydroxide monohydrate and the lithium carbonate in the subsequent treatment process to influence the product purity.
In one embodiment, the lithium adsorbent used in the impurity removal and concentration process may contain xLiCl 2Al (OH)3·nH2O, wherein, 0.2<x<1.2，0<n<2; the dosage of the lithium adsorbent can be 30-150g/L based on the total volume of the lithium-containing brine, and the lithium-containing brine can be treated by the lithium adsorbent to obtain the lithium-containing desorption solution with higher concentration. The concentration and removal of impurities can be performed in a device known to those skilled in the art, such as an adsorption column, and other types of devices will not be described herein.
The membrane separation concentration treatment may be conventionally employed by those skilled in the art, and may include, for example, one or more of nanofiltration treatment, reverse osmosis treatment, and electrodialysis treatment. In a specific embodiment, the membrane separation concentration treatment may sequentially include two-stage nanofiltration treatment, reverse osmosis treatment, and electrodialysis treatment, and the two-stage nanofiltration treatment may be performed continuously or intermittently, which is not limited herein. In another embodiment, the membrane separation concentration treatment may include a primary nanofiltration treatment, a reverse osmosis treatment, a secondary nanofiltration treatment, and an electrodialysis treatment. In another embodiment, the membrane separation concentration treatment may include a primary nanofiltration treatment, a secondary nanofiltration treatment, and a high pressure reverse osmosis treatment. In another embodiment, the membrane separation concentration treatment may include a primary nanofiltration treatment, a high pressure reverse osmosis treatment, and a secondary nanofiltration treatment. Nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment are well known to those skilled in the art, and the treatment conditions may be conventional and will not be described herein.
The resin separation treatment refers to the deep impurity removal treatment of the lithium-containing brine by adopting resin adsorption, the used adsorption resin can comprise one or more of strong-acid cation type resin, weak-acid cation type resin and chelating type ion exchange resin, and after the resin deep impurity removal treatment is carried out by the adsorption resin, the concentration of calcium ions and magnesium ions in the concentrated solution can be further reduced, so that the deep impurity removal of the lithium-containing brine is realized.
According to the disclosure, the concentration of calcium ions in the lithium-rich concentrated solution obtained after the concentration treatment can be lower than 1ppm, the concentration of magnesium ions can be lower than 1ppm, the concentration of lithium ions can be 5000-10000ppm, the concentration of sodium ions can be 3000-6500ppm, and the concentration of potassium ions can be 1200-2400 ppm. Preferably, the concentration of calcium ions in the lithium-rich concentrated solution can be 0-0.5ppm, the concentration of magnesium ions can be 0-0.5ppm, the concentration of lithium ions can be 5500-9800ppm, the concentration of sodium ions can be 3000-5000ppm, and the concentration of potassium ions can be 1200-2000 ppm. The concentration of calcium ions and magnesium ions in the lithium-rich concentrated solution after concentration treatment is obviously reduced, the enrichment of lithium ions is realized, the reduction of impurity ions in the prepared lithium hydroxide monohydrate is facilitated, and the extraction efficiency of lithium ions is improved.
According to the disclosure, the membrane current of the bipolar membrane alkali-making treatment can be 400-1000A/m2Preferably 600-800A/m2(ii) a The single pair of membrane voltage can be 0.5-3V, preferably 0.7-1.5V, the bipolar membrane alkali preparation process can be operated in a constant pressure mode, the desalted raw material can be recycled as stock solution before membrane concentration, and the lithium-rich concentrated solution can be treated by the bipolar membrane to obtain mixed alkali solution containing lithium hydroxide, sodium hydroxide and potassium hydroxide, so that lithium ions in the lithium-containing brine can be fully converted into lithium hydroxide, and the recovery rate of the ions can be further improved.
The bipolar membrane alkalinizing treatment is well known to those skilled in the art, and in particular, the bipolar membrane alkalinizing treatment may be performed in a bipolar membrane system, which may include, for example, an acid compartment, an alkali compartment, a raw material compartment, and an electrode water compartment. Wherein the acid compartment may be constituted by an area between the bipolar membrane surface anode membrane and the anion permselective membrane in the bipolar membrane system, the base compartment may be constituted by an area between the bipolar membrane surface cathode membrane and the cation permselective membrane in the bipolar membrane system, and the raw material compartment may be constituted by an area between the cation permselective membrane and the anion permselective membrane in the bipolar membrane system. Bipolar membranes are well known to those skilled in the art and are composite membranes which may comprise an anionic permselective membrane and a cationic permselective membrane on the surface with a catalytic layer sandwiched therebetween. Water molecules generate hydrogen ions and hydroxide ions in the dissociation process of a catalyst layer of the bipolar membrane, and the hydrogen ions and chloride ions in the lithium-rich concentrated solution penetrate through the cation permselective membrane and enter the acid chamber to form a hydrochloric acid solution; the hydroxide ions and the cations (lithium, sodium and potassium) in the lithium-enriched concentrated solution permeate the anion permselective membrane to enter the alkali chamber to form mixed alkali liquor.
In one embodiment, the method may further comprise: the second recrystallization mother liquor is returned to step S4 to be mixed with the evaporated crystal precipitate, and the first dissolution recrystallization treatment is performed. In another specific embodiment, the method may further include: and returning the first recrystallization mother liquor to the step S3 to be mixed with the mixed alkali liquor, and performing the evaporation crystallization treatment. The mother liquor obtained by twice dissolution and recrystallization is recycled as the stock solution of the last-stage evaporative crystallization and/or dissolution crystallization, so that the recovery rate of the comprehensive lithium can be effectively improved.
According to the present disclosure, the temperature of the evaporative crystallization treatment may be 50-100 ℃ with a crystallization rate of 40-200 g/h; preferably, the temperature is 60-85 ℃ and the crystallization rate is 50-150g/h to further reduce the content of impurities in the mother liquor. Based on the total weight of the evaporation crystallization end point mother liquor, the concentration of sodium ions in the evaporation crystallization end point mother liquor can be 6-11 wt%, and the concentration of potassium ions can be 3-7 wt%; preferably, the concentration of sodium ions in the mother liquor at the end of the evaporative crystallization is 6-9 wt%, and the concentration of potassium ions is 3-6 wt%; the temperature of the first dissolution recrystallization treatment may be 50 to 100 ℃ and the crystallization rate may be 40 to 200g/h, preferably, the temperature is 60 to 85 ℃ and the crystallization rate is 50 to 150 g/h; the concentration of sodium ions in the first recrystallization mother liquor may be from 2 to 6 wt%, and the concentration of potassium ions may be from 1 to 3 wt%, based on the total weight of the first recrystallization mother liquor; preferably, the concentration of sodium ions in the first recrystallization mother liquor is from 2.5 to 4% by weight, and the concentration of potassium ions is from 1 to 2% by weight; the temperature of the second dissolution recrystallization treatment may be 50 to 100 c, the crystallization rate may be 40 to 200g/h, preferably 60 to 85 c, the crystallization rate may be 50 to 150g/h, and the concentration of sodium ions in the second recrystallization mother liquor may be 0.1 to 2% by weight and the concentration of potassium ions may be 0 to 1% by weight, based on the total weight of the second recrystallization mother liquor; preferably, the concentration of sodium ions in the second recrystallization mother liquor is 0.1 to 0.4% by weight, and the concentration of potassium ions is 0 to 0.3% by weight.
Within the above condition range, on one hand, the phenomenon of local supersaturation of the solution in the processes of evaporation crystallization and twice dissolution recrystallization can be effectively relieved, and the crystallization separation of impurity Na/K ions in the mother liquor is avoided; on the other hand, the method can inhibit the formation of a large amount of new nuclei in the crystallization stage to cause the generation of a large amount of fine particles, thereby avoiding the increase of the adhesion amount of the mother liquor to impurities and the increase of the impurity content in the prepared lithium hydroxide monohydrate and lithium carbonate. Wherein the evaporative crystallization treatment may be performed in an evaporative crystallizer, and the first dissolution recrystallization treatment and the second dissolution recrystallization treatment may be performed in a dissolution recrystallization crystallizer, respectively.
In one embodiment, the first dissolution recrystallization process may include: mixing and dissolving the evaporated and crystallized precipitate and pure water to form a saturated solution, and allowing the saturated solution to enter a dissolving and recrystallizing device for evaporation to generate a first recrystallized precipitate and a first recrystallized mother liquor, wherein the sodium/potassium concentration of the first recrystallized mother liquor is reduced, but still contains a certain amount of lithium, and the first recrystallized mother liquor can flow back to the evaporating and crystallizing device for recycling; the first recrystallized precipitate can be further refined again using a second dissolution recrystallization process to bring it to battery grade standards. The second dissolution recrystallization may include: and mixing and dissolving the first recrystallization precipitate and pure water to obtain a saturated solution, and carrying out second dissolution and recrystallization treatment to obtain battery-grade lithium hydroxide monohydrate and second recrystallization mother liquor, wherein the second recrystallization mother liquor has low Na/K impurity content and can be refluxed into a dissolution and recrystallization device for carrying out the first dissolution and recrystallization treatment for recycling.
According to the present disclosure, the method may further comprise: and carrying out carbonization lithium precipitation treatment on the mother liquor at the end point of evaporation crystallization to obtain lithium carbonate. And the carbonization lithium precipitation treatment can carry out secondary extraction on lithium ions in the mother liquor at the end point of the evaporation and crystallization, thereby further improving the comprehensive recovery rate of lithium.
In one embodiment, the lithium carbide deposition process may include: cooling the mother liquor at the end of evaporation crystallization to separate out sodium hydroxide/potassium hydroxide, then carrying out centrifugal separation, carrying out contact reaction on the obtained separated mother liquor and a carbon source to obtain lithium carbonate precipitate, and carrying out optional washing treatment on the lithium carbonate precipitate to obtain the lithium carbonate. And the washing treatment is to pump pure water into the centrifuge to quickly clean the lithium carbonate so as to obtain the battery-grade lithium carbonate.
The conditions of the lithium carbide deposition treatment can be changed in a large range, preferably, the temperature of the lithium carbide deposition treatment can be 60-100 ℃, the precipitation rate of the lithium carbonate can be 2-150g/h, further preferably, the temperature is 80-95 ℃, and the precipitation rate is 60-100 g/h. In the preferable range, the crystal growth process can be strictly carried out according to the process of nucleation and growth, so that the phenomenon that a large area of new nuclei is generated again in the crystal growth stage to cause a plurality of fine particles is avoided, the adhesion amount of the mother liquor is increased, and the content of impurities is increased. Under the conditions, lithium ions in the mother liquor at the end point of evaporation and crystallization can be in full contact reaction with a carbon source, so that the recovery rate of the lithium ions is improved. The carbon source may contain carbon dioxide and/or sodium carbonate. In one embodiment, the carbon source is carbon dioxide, and the contacting reaction of the separation mother liquor and the carbon source may include introducing carbon dioxide gas into the separation mother liquor obtained by cooling and centrifugal separation to form a lithium carbonate precipitate.
In a second aspect of the present disclosure, a battery grade lithium hydroxide monohydrate prepared by the method provided in the first aspect of the present disclosure is provided.
The present disclosure is further illustrated by the following examples, but is not to be construed as being limited thereby.
Example 1
S1, taking a lithium-rich concentrated solution obtained by treating salt lake brine with aluminum salt lithium adsorbent, nanofiltration, reverse osmosis, nanofiltration, electrodialysis and resin as a raw material, wherein the lithium-rich concentrated solution has a Li ion concentration of 7000ppm, a Na ion concentration of 4500ppm, a K ion concentration of 1685ppm, a Ca ion concentration of less than 1ppm and a Mg ion concentration of less than 1 ppm.
S2, the lithium-rich concentrated solution enters a material chamber of a bipolar membrane system as a stock solution, the voltage of a single pair of membranes is 2V, and the current density of the membranes is 800A/m2The bipolar membrane alkali preparation treatment is carried out under the condition of (1), so as to obtain the mixed alkali liquor of lithium hydroxide, sodium hydroxide and potassium hydroxide with the total alkali molar concentration of 2.1mol/L, wherein the concentration of the lithium hydroxide is 4.06 percent, the concentration of the sodium hydroxide is 1.32 percent, and the concentration of the potassium hydroxide is 0.41 percent.
S3, feeding the mixed alkali liquor into an evaporative crystallizer, and carrying out evaporative crystallization under the conditions that the temperature is 80 ℃ and the crystallization rate is 120g/h to obtain an evaporative crystallization precipitate and an evaporative crystallization end point mother liquor, wherein the concentration of Na ions in the evaporative crystallization end point mother liquor is 7 weight percent, the concentration of K ions is 4 weight percent, and the evaporative crystallization precipitate and the evaporative crystallization end point mother liquor are used as a carbonization lithium precipitation stock liquor to carry out secondary lithium extraction.
S4, mixing and dissolving the evaporated and crystallized precipitate and a proper amount of pure water to prepare a saturated solution, and putting the saturated solution into a first dissolving and recrystallizing device to perform first dissolving and recrystallizing treatment, wherein the temperature of the first dissolving and recrystallizing treatment is 80 ℃, and the crystallizing speed is 120g/h, so that a first dissolved and recrystallized precipitate and a first recrystallizing mother liquor are obtained. Wherein the concentration of Na ions in the first recrystallization mother liquor is 3 wt%, and the concentration of K ions is 1.5 wt%, and the first recrystallization mother liquor is reused as the evaporation crystallization stock solution.
S5, mixing and dissolving the first dissolved and recrystallized precipitate and a proper amount of pure water to form a saturated solution, putting the saturated solution into a second dissolved and recrystallized crystallizer for second dissolved and recrystallized treatment, and performing second dissolved and recrystallized treatment under the conditions that the temperature is 80 ℃ and the crystallization rate is 120g/h to obtain the high-purity battery-grade lithium hydroxide monohydrate and a second recrystallization mother liquor. The concentration of Na ions in the second recrystallization mother liquor is 0.2 wt%, and the concentration of K ions is 0.1 wt%, and the second recrystallization mother liquor is recycled as the first dissolution recrystallization stock solution.
And S6, cooling the mother liquor at the evaporation crystallization end point to room temperature, precipitating sodium hydroxide/potassium hydroxide, then performing centrifugal separation, introducing carbon dioxide into the obtained separation mother liquor to perform carbonization lithium precipitation, wherein the reaction temperature of the carbonization lithium precipitation is 92 ℃, the lithium precipitation rate is 80g/h, and the lithium carbonate crude filter cake obtained after the lithium precipitation is washed by pure water to obtain the battery-grade lithium carbonate.
Example 2
The preparation was carried out in the same manner as in example 1 except that in step S1, a lithium-rich concentrated solution obtained by treating salt lake brine with an aluminum salt lithium adsorbent, nanofiltration, reverse osmosis, electrodialysis, and a resin was used as a raw material, and the lithium-rich concentrated solution had a Ca ion concentration of 0.7ppm, a Mg ion concentration of 0.9ppm, a Li ion concentration of 4500ppm, a Na ion concentration of 2890ppm, and a K ion concentration of 1083 ppm.
In step S3, the concentration of Na ions in the mother liquor at the end of evaporative crystallization was 8 wt%, and the concentration of K ions was 4.5 wt%.
In step S4, the first recrystallization mother liquor had a Na ion concentration of 3.5 wt% and a K ion concentration of 2 wt%.
In step S5, the concentration of Na ions in the second recrystallization mother liquor was 0.25 wt%, and the concentration of K ions was 0.15 wt%.
Example 3
Prepared by the same method as example 1, except that the membrane current of the bipolar membrane alkali preparation treatment is 300A/m2And the single-pair membrane voltage is 1.5V, so that the mixed alkali liquor of lithium hydroxide, sodium hydroxide and potassium hydroxide with the total alkali molar concentration of 1.8mol/L is obtained, wherein the concentration of the lithium hydroxide is 3.48 percent, the concentration of the sodium hydroxide is 1.13 percent, and the concentration of the potassium hydroxide is 0.35 percent.
In step S3, the concentration of Na ions in the mother liquor at the end of evaporative crystallization was 7 wt%, and the concentration of K ions was 4 wt%.
In step S4, the first recrystallization mother liquor has a Na ion concentration of 4 wt% and a K ion concentration of 2 wt%.
In step S5, the concentration of Na ions in the second recrystallization mother liquor was 0.3 wt%, and the concentration of K ions was 0.15 wt%.
Example 4
The same procedure as in example 1 was followed, except that the temperature of the evaporative crystallization treatment was 95 ℃ and the crystallization rate was 170 g/h. Based on the total weight of the mother liquor at the end of the evaporation crystallization, the concentration of Na ions in the mother liquor at the end of the evaporation crystallization is 7 wt%, and the concentration of K ions in the mother liquor at the end of the evaporation crystallization is 4 wt%.
In step S4, the first recrystallization mother liquor had a Na ion concentration of 3 wt% and a K ion concentration of 1.5 wt%.
In step S5, the concentration of Na ions in the second recrystallization mother liquor was 0.2 wt%, and the concentration of K ions was 0.1 wt%.
Example 5
The same procedure as in example 1 was followed, except that the temperature of the first dissolution recrystallization treatment was 50 ℃ and the crystallization rate was 45 g/h. The concentration of Na ions in the first recrystallization mother liquor was 3.5 wt% and the concentration of K ions was 2 wt% based on the total weight of the first recrystallization mother liquor.
In step S5, the concentration of Na ions in the second recrystallization mother liquor was 0.3 wt%, and the concentration of K ions was 0.15 wt%.
Example 6
The same procedure as in example 1 was conducted except that the temperature of the second dissolution recrystallization treatment was 90 deg.C, the crystallization rate was 162g/h based on the total weight of the second recrystallization mother liquor, the concentration of Na ions in the second recrystallization mother liquor was 0.3% by weight, and the concentration of K ions was 0.15% by weight.
Example 7
The same procedure as in example 1 was followed, except that the temperature of the evaporative crystallization treatment was 120 ℃, the crystallization rate was 210g/h, the concentration of Na ions in the mother liquor at the end of the evaporative crystallization was 7% by weight, and the concentration of K ions was 4% by weight;
the temperature of the first dissolution recrystallization treatment was 120 ℃, the crystallization rate was 210g/h, the concentration of Na ions in the first recrystallization mother liquor was 3 wt%, and the concentration of K ions was 1.5 wt%;
the temperature of the second dissolution recrystallization treatment was 120 ℃, the crystallization rate was 210g/h, the Na ion concentration in the second recrystallization mother liquor was 0.2 wt%, and the K ion concentration was 0.1 wt%.
Example 8
The same procedure as in example 1 was followed, except that the reaction temperature for precipitating lithium by carbonization was 80 ℃ and the rate of precipitating lithium was 160 g/h.
Example 9
The same procedure as in example 1 was followed, except that step S6 was not included, and the mother liquor from the evaporative crystallization was not further treated.
Comparative example 1
The same procedure as in example 1 was followed, except that step S5 was not included, and the first dissolved recrystallized precipitate from step S4 was obtained directly as a lithium hydroxide product.
Test example
Elemental analysis tests were performed on examples and comparative examples using an AAS-atomic absorption spectrophotometer [ AAS201701], an ICP-OES-plasma atomic emission spectrometer [ ICP200601] apparatus, the sodium ion concentration and the potassium ion concentration in table 1 respectively represent the sodium ion concentration and the potassium ion concentration in lithium hydroxide monohydrate, and the test results are shown in table 1.
The lithium recovery rate is the percentage of the lithium in the lithium hydroxide monohydrate and lithium carbonate in the product to the total lithium in the mixed alkali solution.
TABLE 1
The method disclosed by the invention can be used for extracting high-purity lithium hydroxide monohydrate from lithium-containing brine through two times of dissolving and recrystallization treatments, and has the advantages of high recovery rate of lithium ions, low production cost and easiness in industrialization.
The preferred embodiments of the present disclosure have been described in detail above, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.
Claims (10)
1. A method for extracting lithium is characterized by comprising the following steps:
s1, carrying out impurity removal and concentration treatment on the lithium-containing brine to obtain a lithium-rich concentrated solution;
s2, performing bipolar membrane alkali preparation treatment on the lithium-rich concentrated solution to obtain mixed alkali liquor and a hydrochloric acid solution;
s3, carrying out evaporation crystallization treatment on the mixed alkali liquor to obtain an evaporation crystallization precipitate and an evaporation crystallization end point mother liquor;
s4, subjecting the evaporation crystallization precipitate to a first dissolution recrystallization treatment to obtain a first recrystallization precipitate and a first recrystallization mother liquor;
s5, subjecting the first recrystallized precipitate to a second dissolution recrystallization treatment to obtain lithium hydroxide monohydrate and a second recrystallization mother liquor.
2. The method of claim 1, wherein the impurity removal concentration process comprises: and contacting the lithium-containing brine with a lithium adsorbent to carry out impurity removal and concentration treatment, and then sequentially carrying out membrane separation and concentration treatment and resin separation treatment.
3. The method according to claim 2, wherein the impurity removal and concentration treatment is carried out byThe lithium adsorbent contains xLiCl 2Al (OH)3·nH2O, wherein, 0.2<x<1.2，0<n<2; based on the total volume of the lithium-containing brine, the dosage of the lithium adsorbent is 30-150 g/L;
the membrane separation concentration treatment sequentially comprises two-stage nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment; or the membrane separation concentration treatment sequentially comprises primary nanofiltration treatment, reverse osmosis treatment, secondary nanofiltration treatment and electrodialysis treatment; or the membrane separation concentration treatment sequentially comprises the primary nanofiltration treatment, the secondary nanofiltration treatment and the high-pressure reverse osmosis treatment; or the membrane separation concentration treatment sequentially comprises the primary nanofiltration treatment, the high-pressure reverse osmosis treatment and the secondary nanofiltration treatment;
the adsorption resin used in the resin separation treatment comprises one or more of strong-acid cation type resin, weak-acid cation type resin and chelate type ion exchange resin.
4. The method as claimed in any one of claims 1 to 3, wherein the concentration of calcium ions in the lithium-rich concentrated solution is less than 1ppm, the concentration of magnesium ions is less than 1ppm, the concentration of lithium ions is 5000-10000ppm, the concentration of sodium ions is 3000-6500ppm, and the concentration of potassium ions is 1200-2400 ppm.
5. The method according to any one of claims 1-3, wherein the membrane current of the bipolar membrane alkali-making treatment is 400-1000A/m2The voltage of the single pair of membranes is 0.5-3V.
6. A method according to any one of claims 1-3, characterized in that the method further comprises: returning the second recrystallization mother liquor to step S4 to mix with the evaporative crystallization educt to perform the first dissolution recrystallization treatment; and/or returning the first recrystallization mother liquor to the step S3 to be mixed with the mixed alkali liquor, and carrying out the evaporation crystallization treatment.
7. The method according to claim 1, wherein the temperature of the evaporative crystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the evaporative crystallization end-point mother liquor is 6-11 wt% and the concentration of potassium ions is 3-7 wt% based on the total weight of the evaporative crystallization end-point mother liquor;
the temperature of the first dissolution recrystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the first recrystallization mother liquor is 2-6 wt% and the concentration of potassium ions in the first recrystallization mother liquor is 1-3 wt% based on the total weight of the first recrystallization mother liquor;
the temperature of the second dissolution recrystallization treatment is 50-100 ℃, the crystallization rate is 40-200g/h, and the concentration of sodium ions in the second recrystallization mother liquor is 0.1-2 wt% and the concentration of potassium ions in the second recrystallization mother liquor is 0-1 wt% based on the total weight of the second recrystallization mother liquor.
8. The method of claim 1, further comprising: and carrying out carbonization lithium precipitation treatment on the evaporation crystallization end point mother liquor to obtain lithium carbonate.
9. The method of claim 8, wherein the lithium carbide precipitation treatment comprises: cooling the evaporation crystallization end point mother liquor to separate out sodium hydroxide/potassium hydroxide, then carrying out centrifugal separation, carrying out contact reaction on the obtained separation mother liquor and a carbon source to obtain lithium carbonate precipitate, and carrying out optional washing treatment on the lithium carbonate precipitate to obtain the lithium carbonate;
the temperature of the carbonization lithium precipitation treatment is 60-100 ℃, and the precipitation rate of the lithium carbonate is 2-150 g/h;
the carbon source contains carbon dioxide and/or sodium carbonate.
10. A battery grade lithium hydroxide monohydrate prepared by the process of any one of claims 1 to 7.
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