Method for separating lithium and boron in solution with high boron-lithium ratio

Abstract

The invention discloses a method for separating lithium and boron in a solution with a high boron-lithium ratio. The separation method comprises the following steps: carrying out primary homogeneous electrodialysis concentration separation on a solution with a high boron-lithium ratio under an alkaline condition to prepare primary lithium-rich concentrated water; diluting the first-stage lithium-rich concentrated water to prepare first-stage diluted lithium-rich concentrated water; performing high-pressure RO concentration on the primary diluted lithium-rich concentrated water under an acidic condition to prepare lithium-rich RO concentrated water; performing first-stage homogeneous phase electrodialysis concentration separation on the lithium-rich RO concentrated water under an acidic condition to prepare first-stage lithium-rich concentrated water; carrying out adsorption boron removal and desorption treatment on the first-stage lithium-rich concentrated water by adopting boron removal adsorption resin under an alkaline condition to prepare mixed lithium-rich concentrated water and boron-containing desorption liquid; carrying out MVR (mechanical vapor recompression) evaporation on the mixed lithium-rich concentrated water for preparing battery-grade lithium carbonate; and mixing the secondary boron-rich fresh water with the boron-containing desorption solution, and carrying out MVR evaporation to obtain a boric acid product. According to the method, a reasonable boron removal process combination is adopted, and boron in the solution with the high boron-lithium ratio is removed.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium-boron separation, and particularly relates to a method for separating lithium-boron in a high boron-to-lithium ratio solution. Background Art

[0002] Lithium, known as the "white oil" of the 21st century, plays a crucial role in the development of the new energy industry. Over 70% of global lithium resources are found in salt lake brines, and adsorption-based lithium extraction from brine has become the industry's most mainstream process. While adsorption-based lithium extraction offers high selectivity, it still introduces a certain amount of other ions into the desorption solution, such as calcium, magnesium, and borate. To produce battery-grade lithium carbonate, it is essential to remove these impurities from the desorption solution. A multi-stage nanofiltration membrane system coupled with adsorption-based lithium extraction can achieve a high degree of separation of calcium and magnesium ions from the desorption solution. This can be supplemented by resin purification and impurity removal to achieve complete removal of these ions. However, during operation, boric acid molecules and borate ions can also permeate the nanofiltration membranes, resulting in the presence of boron in the actual nanofiltration product water, with high residual boron concentrations and poor boron-lithium separation. Removing boron from high-boron, lithium-rich concentrates is crucial for producing battery-grade lithium carbonate from salt lake brines.

[0003] The main methods for extracting boron from brine include borate precipitation, extraction, adsorption, nanofiltration, and electrodialysis. The borate precipitation method utilizes alkaline earth metal ions, such as calcium and magnesium, to react with boron to form a borate precipitate. This method utilizes inexpensive and readily available raw materials, making it suitable for high-boron brines. However, the precipitation rate is low, at only 50%, and the brine is prone to introducing excessive calcium and magnesium ions, making impurity removal more difficult. Boron removal by extraction utilizes the chelation effect of boric acid with polyols and hydroxylamine extractants under strong acid conditions, transferring boron from the aqueous phase to the organic phase to achieve boron removal. Solvent extraction offers excellent separation, keeping the boron concentration in the raffinate below tens of ppm. However, the solvent is highly volatile, and back extraction can easily produce emulsification and form a third phase. The adsorption method uses boron ion exchange resin as the adsorbent. Under alkaline conditions, the chelating ligands in the resin phase form stable chelates with boron, achieving boron exchange and separation in the brine. However, due to the low adsorption capacity of boron ion exchange resin, the resin quickly reaches saturation, making the adsorption method suitable for brines with low boron content. However, high boron content requires significantly increased resin dosage and frequent resin regeneration, which increases acid consumption during the desorption process and increases treatment costs. During nanofiltration membrane operation, boric acid molecules and ions can also pass through the nanofiltration membrane. Therefore, boron elements are still present in the permeate of the nanofiltration membrane, and the residual boron concentration is high, resulting in poor boron removal.

[0004] When the brine boron concentration is low, electrodialysis membranes can effectively separate lithium and boron from the brine, maintaining the boron concentration in the lithium-rich concentrated water below 100 ppm. Continuing to use resins for boron removal can quickly achieve the goal of brine refining and impurity removal to produce battery-grade lithium carbonate. However, when the brine boron concentration remains high, such as above 2 g / L, regardless of brine pH adjustment, the boron concentration in the lithium-rich concentrated water obtained by electrodialysis remains high, exceeding 700 ppm. This significantly reduces the boron removal efficiency, and continuing to use resins for refining and boron removal will inevitably increase resin input and operating costs. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for separating lithium and boron in a high boron-to-lithium ratio solution to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] An embodiment of the present invention provides a method for separating lithium and boron in a high boron to lithium ratio solution, comprising:

[0008] Providing a high boron-to-lithium ratio solution; wherein the lithium ion concentration in the high boron-to-lithium ratio solution is 3-6 g / L, the boron ion concentration is 3.5-6 g / L, and the boron-to-lithium mass ratio is 0.58 to 2:1;

[0009] The high boron-lithium ratio solution is regulated to undergo a first-stage homogeneous electrodialysis concentration separation under alkaline conditions to produce a first-stage lithium-rich concentrated water and a first-stage boron-rich fresh water;

[0010] diluting the first-level lithium-rich concentrated water to obtain first-level diluted lithium-rich concentrated water;

[0011] The primary diluted lithium-rich concentrated water is regulated to undergo high-pressure RO concentration under acidic conditions to produce lithium-rich RO concentrated water and low-boron RO fresh water; wherein the operating pressure of the high-pressure RO concentration is 5-10 MPa;

[0012] The lithium-rich RO concentrated water is regulated to undergo a homogeneous electrodialysis concentration separation under acidic conditions to produce a lithium-rich concentrated water section and a boron-rich fresh water section;

[0013] Controlling the first-level boron-rich fresh water to perform secondary homogeneous electroosmotic concentration and separation under acidic conditions to produce secondary lithium-rich concentrated water and secondary boron-rich fresh water;

[0014] The secondary lithium-rich concentrated water is regulated to undergo two-stage homogeneous electrodialysis concentration separation under acidic conditions to produce second-stage lithium-rich concentrated water and second-stage boron-rich fresh water;

[0015] The first-stage lithium-rich concentrated water and the second-stage lithium-rich concentrated water are mixed and subjected to adsorption and deboron removal and desorption treatment using a boron removal adsorption resin under alkaline conditions to obtain a mixed lithium-rich concentrated water and a boron-containing desorption liquid; wherein the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm;

[0016] The mixed lithium-rich concentrated water is subjected to MVR forced evaporation and concentration for the preparation of battery-grade lithium carbonate;

[0017] Furthermore, the secondary boron-rich fresh water is mixed with the boron-containing desorption liquid and subjected to MVR forced evaporation and concentration to obtain a boric acid product.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention addresses the drawback that the electrodialysis boron removal efficiency of high-boron, high-lithium, and high-boron-to-lithium ratio solutions is greatly reduced, and adopts a reasonable boron removal process combination to achieve the removal of boron in high-boron, high-lithium, and high-boron-to-lithium ratio solutions;

[0020] (2) The separation method of the present invention successfully reduces the boron ion concentration in the electrodialysis lithium-rich concentrated water to below 100 ppm. The boron ion concentration in the electrodialysis lithium-rich concentrated water is close to 1 / 10 of that in the existing process technology, which greatly reduces the difficulty of subsequent resin refining and impurity removal and the consumption of resin and acid and alkali, and has obvious process and economic advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a process flow chart for separating lithium and boron from a high boron-to-lithium ratio solution in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0023] In view of the shortcomings of the prior art, the inventors of this case, after long-term research and extensive practice, have proposed the technical solution of the present invention. The technical solution of the present invention will be clearly and completely described below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making any creative effort shall fall within the scope of protection of the present invention.

[0024] Specifically, as one aspect of the technical solution of the present invention, a method for separating lithium and boron from a high boron to lithium ratio solution includes:

[0025] The high boron-lithium ratio solution is provided; wherein the lithium ion concentration in the high boron-lithium ratio solution is 3-6 g / L, the boron ion concentration is 3.5-6 g / L, and the boron-lithium mass ratio is 0.58-2:1.

[0026] The high boron-lithium ratio solution is regulated to perform primary homogeneous electrodialysis concentration separation under alkaline conditions to obtain primary lithium-rich concentrated water and primary boron-rich dilute water.

[0027] The primary lithium-rich concentrated water is diluted to obtain primary diluted lithium-rich concentrated water.

[0028] The primary diluted lithium-rich concentrated water is regulated to perform high-pressure RO concentration under acidic conditions to obtain lithium-rich RO concentrated water and low-boron RO dilute water; wherein the operation pressure of the high-pressure RO concentration is 5-10 MPa.

[0029] The lithium-rich RO concentrated water is regulated to perform one-stage homogeneous electrodialysis concentration separation under acidic conditions to obtain one-stage lithium-rich concentrated water and one-stage boron-rich dilute water.

[0030] The primary boron-rich dilute water is regulated to perform two-stage homogeneous electrodialysis concentration separation under acidic conditions to obtain two-stage lithium-rich concentrated water and two-stage boron-rich dilute water.

[0031] The two-stage lithium-rich concentrated water is regulated to perform two-stage homogeneous electrodialysis concentration separation under acidic conditions to obtain two-stage lithium-rich concentrated water and two-stage boron-rich dilute water.

[0032] The one-stage lithium-rich concentrated water and the two-stage lithium-rich concentrated water are mixed and subjected to adsorption and desorption treatment of boron using boron-removing adsorption resin under alkaline conditions to obtain mixed lithium-rich concentrated water and boron-containing desorption liquid; wherein the boron ion concentration in the mixed lithium-rich concentrated water is <10 ppm.

[0033] The mixed lithium-rich concentrated water is subjected to MVR forced evaporation concentration for preparation of battery-grade lithium carbonate.

[0034] And the two-stage boron-rich dilute water and the boron-containing desorption liquid are mixed and subjected to MVR forced evaporation concentration to obtain a boric acid product.

[0035] The high boron-lithium ratio solution in the application is a high-boron, high-lithium, and high-boron-lithium ratio solution.

[0036] In some preferred embodiments, the separation method specifically comprises: regulating the pH value of the high boron-lithium ratio solution to 7-12 to perform primary homogeneous electrodialysis concentration separation to obtain primary lithium-rich concentrated water and primary boron-rich dilute water; wherein the lithium ion concentration in the primary lithium-rich concentrated water is 10-18 g / L, the boron ion concentration is 1-2.5 g / L, and the boron-lithium mass ratio is 0.06-0.25:1.

[0037] In some preferred embodiments, the separation method specifically includes: diluting the first-level lithium-rich concentrated water to obtain first-level diluted lithium-rich concentrated water; wherein the lithium ion concentration in the first-level diluted lithium-rich concentrated water is 3-6 g / L, and the boron ion concentration is 0.3-0.7 g / .

[0038] In some preferred embodiments, the separation method specifically includes: regulating the pH value of the first-stage diluted lithium-rich concentrated water to 3-5 for high-pressure RO concentration to produce lithium-rich RO concentrated water and low-boron RO fresh water; wherein the operating pressure adopted by the high-pressure RO concentration is 5-10 MPa; the lithium ion concentration in the lithium-rich RO concentrated water is 8-12 g / L, and the boron ion concentration is 0.4-0.9 g / L; the lithium ion concentration in the low-boron RO fresh water is 0.2-0.3 g / L, and the boron ion concentration is 0.25-0.5 g / L.

[0039] Furthermore, the low-boron RO fresh water is used for adsorption and extraction of lithium.

[0040] In some preferred embodiments, the separation method specifically includes: regulating the pH value of the lithium-rich RO concentrated water to 3-7 to perform a stage of homogeneous electrodialysis concentration separation to produce a stage of lithium-rich concentrated water and a stage of boron-rich fresh water; wherein the lithium ion concentration in the stage of lithium-rich concentrated water is 13-20 g / L, and the boron ion concentration is 0.06-0.1 g / L; the lithium ion concentration in the stage of boron-rich fresh water is 0.8-1.2 g / L, and the boron ion concentration is 0.5-1 g / L.

[0041] Furthermore, the first stage of boron-rich fresh water is used as dilution fresh water to dilute the first stage of lithium-rich concentrated water.

[0042] In some preferred embodiments, the separation method specifically includes: regulating the pH value of the first-level boron-rich fresh water to 3-5 to perform secondary homogeneous electroosmotic concentration separation to produce secondary lithium-rich concentrated water and secondary boron-rich fresh water; wherein, the lithium ion concentration in the secondary lithium-rich concentrated water is 5-8 g / L, and the boron ion concentration is 0.4-1 g / L; the lithium ion concentration in the secondary boron-rich fresh water is 0.03-0.1 g / L, and the boron ion concentration is 4-4.5 g / L.

[0043] In some preferred embodiments, the separation method specifically includes: regulating the pH value of the secondary lithium-rich concentrated water to 3-5 to perform two-stage homogeneous electrodialysis concentration separation to produce two-stage lithium-rich concentrated water and two-stage boron-rich fresh water; wherein, the lithium ion concentration in the second-stage lithium-rich concentrated water is 13-20 g / L, and the boron ion concentration is 0.06-0.1 g / L; the lithium ion concentration in the second-stage boron-rich fresh water is 0.8-1.2 g / L, and the boron ion concentration is 0.5-1.1 g / L.

[0044] Furthermore, the second-stage boron-rich fresh water is used as dilution fresh water to dilute the first-stage lithium-rich concentrated water.

[0045] In some preferred embodiments, the separation method specifically includes: mixing the first-stage lithium-rich concentrated water with the second-stage lithium-rich concentrated water and adjusting the pH value to 10-12, using a boron removal adsorption resin to perform adsorption and boron removal and desorption treatment to obtain a mixed lithium-rich concentrated water and a boron-containing desorption liquid; wherein the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm, and the boron concentration in the boron-containing desorption liquid is 3-5 g / L.

[0046] Furthermore, the adsorbed boron removal adsorption resin is desorbed using hydrochloric acid; wherein the concentration of the hydrochloric acid is 0.5-2 mol / L.

[0047] In some preferred embodiments, the separation method specifically includes: subjecting the mixed lithium-rich concentrated water to MVR forced evaporation and concentration, and then transporting it to a lithium precipitation section for the preparation of battery-grade lithium carbonate.

[0048] In some preferred embodiments, the separation method specifically includes: mixing the secondary boron-rich fresh water with the boron-containing desorption liquid and performing MVR forced evaporation concentration to obtain a crude boric acid product, followed by washing and drying to obtain a boric acid product.

[0049] Furthermore, the content of boric acid in the boric acid product is greater than 99%.

[0050] In some preferred embodiments, the process flow chart for separating lithium and boron from a high boron to lithium ratio solution of the present invention is as follows: Figure 1 shown.

[0051] In some more specific embodiments, the method for separating lithium and boron from a high boron to lithium ratio solution comprises:

[0052] (1) Using hydrochloric acid or sodium hydroxide solution, the pH of the initial high boron-lithium ratio solution is adjusted and controlled within the range of 7-12, and a first-stage homogeneous electrodialysis concentration separation is performed to obtain a first-stage lithium-rich concentrated water and a first-stage boron-rich fresh water. The initial high boron-lithium ratio solution has a lithium ion concentration of 3-6 g / L, a boron ion concentration of 3.5-6 g / L, and a boron-lithium mass ratio of 0.58 to 2:1; the first-stage lithium-rich concentrated water has a lithium ion concentration of 10-18 g / L, a boron ion concentration of 1-2.5 g / L; and the first-stage boron-rich fresh water has a lithium ion concentration of 0.5-2 g / L, and a boron ion concentration of 4-6.5 g / L. The boron removal rate reaches 65%-70%.

[0053] (2) The first-stage lithium-rich concentrated water is diluted with fresh water to obtain the first-stage diluted lithium-rich concentrated water. The first-stage diluted lithium-rich concentrated water has a lithium ion concentration of 3-6 g / L and a boron ion concentration of 0.3-0.7 g / L.

[0054] (3) Using hydrochloric acid solution, the pH of the first-stage diluted lithium-rich concentrated water is adjusted to within the range of 3-5, and high-pressure RO concentration is performed. The operating pressure is controlled within the range of 5-10 MPa to obtain lithium-rich RO concentrated water and low-boron RO fresh water. The lithium ion concentration of the lithium-rich RO concentrated water is 8-12 g / L, and the boron ion concentration is 0.4-0.9 g / L; the lithium ion concentration of the low-boron RO fresh water is 0.2-0.3 g / L, and the boron ion concentration is 0.25-0.5 g / L. The stage boron retention rate reaches 75%. The low-boron RO fresh water is returned to the adsorption lithium extraction stage for reuse.

[0055] (4) The pH of the lithium-rich RO concentrate is controlled within the range of 3-7, and the lithium-rich RO concentrate is subjected to a first stage of homogeneous electrodialysis concentration separation to obtain a first stage of lithium-rich concentrate and a first stage of boron-rich freshwater. The lithium ion concentration of the first stage of lithium-rich concentrate is 13-20 g / L, and the boron ion concentration is 0.06-0.1 g / L; the lithium ion concentration of the first stage of boron-rich freshwater is 0.8-1.2 g / L, and the boron ion concentration is 0.5-1 g / L. The boron removal rate reaches 80%-90%. The first stage of boron-rich freshwater is returned to the first stage of lithium-rich concentrate dilution and reused as diluted freshwater.

[0056] (5) The pH of the first-stage boron-rich freshwater is adjusted to a range of 3-5, and a second-stage homogeneous electroosmotic concentration separation is performed to obtain a second-stage lithium-rich concentrated water and a second-stage boron-rich freshwater. The second-stage lithium-rich concentrated water has a lithium ion concentration of 5-8 g / L and a boron ion concentration of 0.4-1 g / L; the second-stage boron-rich freshwater has a lithium ion concentration of 0.03-0.1 g / L and a boron ion concentration of 4-4.5 g / L. The boron removal rate in this stage exceeds 95%.

[0057] (6) The pH of the secondary lithium-rich concentrated water is adjusted to within the range of 3-5, and a second stage of homogeneous electrodialysis concentration separation is performed to obtain a second stage lithium-rich concentrated water and a second stage boron-rich fresh water. The lithium ion concentration of the second stage lithium-rich concentrated water is 13-20 g / L, and the boron ion concentration is 0.06-0.1 g / L; the lithium ion concentration of the second stage boron-rich fresh water is 0.8-1.2 g / L, and the boron ion concentration is 0.5-1.1 g / L. The boron removal rate reaches 80%-90%. The second stage boron-rich fresh water is returned to the first stage lithium-rich concentrated water dilution stage for reuse as diluted fresh water.

[0058] (7) Mixing the first-stage lithium-rich concentrated water and the second-stage lithium-rich concentrated water, adjusting the pH to within the range of 10-12, and performing refined boron removal using a boron removal adsorption resin. After refining and impurity removal, the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm. The adsorbed boron removal resin is subjected to hydrochloric acid desorption regeneration at a hydrochloric acid concentration of 0.5-2 mol / L to obtain a boron-containing desorption solution, wherein the boron concentration in the boron-containing desorption solution is 3-5 g / L.

[0059] (8) The mixed lithium-rich concentrated water after purification and impurity removal is subjected to MVR forced evaporation and concentration and then sent to the lithium precipitation section for the preparation of battery-grade lithium carbonate.

[0060] (9) mixing the secondary boron-rich fresh water and the boron-containing desorption liquid, performing MVR forced evaporation and concentration, and precipitating a crude boric acid product; washing and drying the crude product to obtain a boric acid product, wherein the boric acid content in the product is higher than 99%.

[0061] Through the process optimization of the present invention, the boron ion concentration in the electrodialysis lithium-rich concentrated water is successfully reduced to below 100 ppm. The boron ion concentration in the electrodialysis lithium-rich concentrated water is close to 1 / 10 of that in the existing process technology, which greatly reduces the difficulty of subsequent resin refining and impurity removal and the consumption of resin and acid and alkali, and has obvious process and economic advantages.

[0062] This invention utilizes a coupled process of "alkaline electrodialysis concentration + high-pressure RO concentration + acidic electrodialysis concentration" to achieve truly efficient lithium-boron separation in high-boron-to-lithium ratio solutions. The alkaline electrodialysis concentration maximizes lithium-boron separation, achieving a boron removal rate of 65%-70%. Based on the properties of the electrodialysis concentrate, the high-pressure RO ensures lithium concentration while maximizing boron permeation into the freshwater stream, achieving a boron retention rate of 75%. Furthermore, based on this dual lithium-boron separation, the acidic electrodialysis concentration is continued, where the boron retardation effect is minimal, resulting in even better lithium-boron separation. The boron ion concentration in the resulting lithium-rich concentrate is reduced to below 100 ppm. These three processes are seamlessly integrated and essential.

[0063] The primary homogeneous electrodialysis concentration separation in the present invention is carried out under alkaline conditions because the boron ion concentration in the initial high boron-to-lithium ratio solution is 3.5-6 g / L. Under acidic conditions, there is a high risk of boric acid precipitation, which accumulates on the membrane surface and affects the stable operation of the equipment. Under alkaline conditions, the supersaturation of boron increases, and a higher concentration of boron can be stably present in the solution in the form of polyborate, ensuring the stable operation of the homogeneous electrodialysis. At the same time, the migration rate of polyborate is much lower than that of chloride ions, and the hydrated ion radius is large, so that a large amount of polyborate is retained on the fresh water side during the electrodialysis operation, thereby achieving efficient separation of lithium and boron.

[0064] The reason why high-pressure RO concentration, one-stage homogeneous electrodialysis concentration and separation, two-stage homogeneous electrodialysis concentration and separation, and two-stage homogeneous electrodialysis concentration and separation in the present invention can only be carried out under acidic conditions is because:

[0065] (1) Under acidic conditions, boron in the primary diluted lithium-rich concentrate is primarily present as boric acid, which has a relatively small molecular size. During high-pressure RO system operation, some boron can penetrate the RO membrane and enter the RO fresh water side, achieving partial boron removal. Under neutral and alkaline conditions, boron exists in the form of borate or polyborate, which has a very large hydrated ion radius. During the RO concentration process, most of the boron and lithium are retained in the concentrate side, and lithium and boron cannot be separated.

[0066] (2) Due to the continuous concentration of the first-stage electrodialysis and high-pressure RO, the cations in the lithium-rich RO concentrate are concentrated to the same degree. In particular, after the calcium and magnesium ions are concentrated to a certain degree, the continued homogeneous electrodialysis concentration separation under alkaline conditions will easily form hydroxide precipitation on the membrane surface, affecting the membrane transmission efficiency and even causing irreversible changes in the membrane structure. This situation can be avoided under acidic conditions, allowing the homogeneous electrodialysis to operate stably.

[0067] (3) The properties of the primary boron-rich freshwater are lithium-poor and boron-rich freshwater. Boron-containing anions dominate the anions and combine with lithium ions to form lithium borate. Under alkaline conditions, bipolar membrane electrodialysis concentration is carried out. Due to the large ion radius, the hydrated boron-containing anions cannot penetrate the anion membrane and remain in the freshwater chamber. Due to the electrical neutrality of the solution, the boron-containing anions will attract lithium ions to remain on the freshwater side, preventing them from migrating to the concentrated water chamber, making it impossible to achieve lithium-boron separation. Under acidic conditions, boron is mainly in the form of boric acid in the solution and is electrically neutral. Under the action of the DC electric field, it does not migrate and remains in the freshwater chamber. At this time, lithium ions will still migrate into the concentrated water chamber, thus achieving lithium-boron separation.

[0068] (4) The second stage electrodialysis concentration separation is operated under acidic conditions, which is more concerned with the connection with the previous and next stages. While reducing the consumption of acid and alkali, it also avoids the risk of scaling caused by mixing during operation.

[0069] The present invention can be widely applied to the existing salt lake brine adsorption lithium extraction process, and has great advantages especially for high-boron brine.

[0070] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0071] Unless otherwise specified, the experimental materials used in the following examples can be purchased from conventional biochemical reagent companies.

[0072] Example 1

[0073] (1) Using hydrochloric acid or sodium hydroxide solution, adjust and control the pH of the initial high boron-lithium ratio solution within the range of 7-12, and perform a first-stage homogeneous electrodialysis concentration separation to obtain a first-stage lithium-rich concentrated water and a first-stage boron-rich fresh water.

[0074] (2) The first-stage lithium-rich concentrated water is diluted with fresh water to obtain the first-stage diluted lithium-rich concentrated water.

[0075] (3) Using hydrochloric acid solution, adjust the pH of the primary diluted lithium-rich concentrated water to within the range of 3-5, and perform high-pressure RO concentration. The operating pressure is controlled within the range of 5-10 MPa to obtain lithium-rich RO concentrated water and low-boron RO fresh water. The low-boron RO fresh water is returned to the adsorption lithium extraction stage for reuse.

[0076] (4) The pH of the lithium-rich RO concentrate is controlled within the range of 3-7, and the lithium-rich RO concentrate is subjected to a homogeneous electrodialysis concentration separation to obtain a lithium-rich concentrate and a boron-rich freshwater. The boron-rich freshwater is returned to the first lithium-rich concentrate dilution section for reuse as dilution freshwater.

[0077] (5) The pH of the first-stage boron-rich fresh water is adjusted to be within the range of 3-5, and a second-stage homogeneous electroosmotic concentration and separation is performed to obtain a second-stage lithium-rich concentrated water and a second-stage boron-rich fresh water.

[0078] (6) The pH of the secondary lithium-rich concentrated water is adjusted to within the range of 3-5, and a second stage of homogeneous electrodialysis is performed to concentrate and separate the secondary lithium-rich concentrated water and the second stage of boron-rich fresh water. The second stage of boron-rich fresh water is returned to the primary lithium-rich concentrated water dilution stage for reuse as diluted fresh water.

[0079] (7) Mixing the first-stage lithium-rich concentrated water and the second-stage lithium-rich concentrated water, adjusting the pH to within the range of 10-12, and performing refined boron removal using a boron removal adsorption resin. After refining and impurity removal, the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm. Desorption and regeneration of the adsorbed boron removal resin are performed using hydrochloric acid at a concentration of 0.5-2 mol / L to obtain a boron-containing desorption solution.

[0080] (8) The mixed lithium-rich concentrated water after purification and impurity removal is subjected to MVR forced evaporation and concentration and then sent to the lithium precipitation section to prepare battery-grade lithium carbonate.

[0081] (9) mixing the secondary boron-rich fresh water and the boron-containing desorption liquid, performing MVR forced evaporation and concentration, and precipitating a crude boric acid product; washing and drying the crude product to obtain a boric acid product.

[0082] The specific parameters and results of this embodiment are shown in Table 1;

[0083] Table 1

[0084]

[0085] Example 2

[0086] The method is the same as in Example 1. The specific parameters and results are shown in Table 2.

[0087] Table 2

[0088]

[0089] Example 3

[0090] The method is the same as in Example 1. The specific parameters and results are shown in Table 3.

[0091] Table 3

[0092]

[0093]

[0094] Comparative Example 1

[0095] The method is the same as Example 3, except that the first-stage homogeneous electrodialysis concentration separation is carried out under acidic conditions. During the pH adjustment process, boric acid crystals begin to precipitate, causing the homogeneous electrodialysis equipment to be unable to operate.

[0096] Comparative Example 2

[0097] The method is the same as Example 1, except that: the fresh water dilution step is missing, and when the high-pressure RO membrane system is operated, the water inlet pressure quickly reaches the upper limit of the operating pressure, and the water production is extremely low, which cannot achieve the partial removal effect of boron.

[0098] Comparative Example 3

[0099] The method is the same as Example 1, except that the high-pressure RO concentration is carried out under alkaline conditions. The test results show that the boron and lithium concentration ratios on the retained concentrate side are similar, and the lithium-boron separation effect is not achieved.

[0100] Comparative Example 4

[0101] The method was the same as Example 1, except that the first homogeneous electrodialysis concentration separation was performed under alkaline conditions. During operation, white flocculent matter appeared on the surface of the electrodialysis membrane to varying degrees, blocking the pores. Detection results showed that these were calcium and magnesium hydroxide crystals.

[0102] Comparative Example 5

[0103] The method is the same as Example 1, except that the secondary homogeneous electroosmotic concentration and separation is carried out under alkaline conditions. The test results show that lithium and boron are enriched and concentrated on the same side, but the purpose of lithium and boron separation is not achieved.

[0104] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0105] It should be understood that the technical solution of the present invention is not limited to the above-mentioned specific implementation cases. Any technical variations made according to the technical solution of the present invention without departing from the scope of protection of the purpose of the present invention and the claims shall fall within the scope of protection of the present invention.

Claims

1. A method for separating lithium and boron from a high boron to lithium ratio solution, characterized in that: include: Providing a high boron-to-lithium ratio solution; wherein the lithium ion concentration in the high boron-to-lithium ratio solution is 3-6 g / L, the boron ion concentration is 3.5-6 g / L, and the boron-to-lithium mass ratio is 0.58 to 2:1; The high boron-lithium ratio solution is regulated to undergo a first-stage homogeneous electrodialysis concentration separation under alkaline conditions to produce a first-stage lithium-rich concentrated water and a first-stage boron-rich fresh water; diluting the first-level lithium-rich concentrated water to obtain first-level diluted lithium-rich concentrated water; The primary diluted lithium-rich concentrated water is regulated to undergo high-pressure RO concentration under acidic conditions to produce lithium-rich RO concentrated water and low-boron RO fresh water; wherein the operating pressure of the high-pressure RO concentration is 5-10 MPa; The lithium-rich RO concentrated water is regulated to undergo a homogeneous electrodialysis concentration separation under acidic conditions to produce a lithium-rich concentrated water section and a boron-rich fresh water section; Controlling the first-level boron-rich fresh water to perform secondary homogeneous electroosmotic concentration and separation under acidic conditions to produce secondary lithium-rich concentrated water and secondary boron-rich fresh water; The secondary lithium-rich concentrated water is regulated to undergo two-stage homogeneous electrodialysis concentration separation under acidic conditions to produce second-stage lithium-rich concentrated water and second-stage boron-rich fresh water; The first-stage lithium-rich concentrated water and the second-stage lithium-rich concentrated water are mixed and subjected to adsorption and deboron removal and desorption treatment using a boron removal adsorption resin under alkaline conditions to obtain a mixed lithium-rich concentrated water and a boron-containing desorption liquid; wherein the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm; The mixed lithium-rich concentrated water is subjected to MVR forced evaporation and concentration for the preparation of battery-grade lithium carbonate; Furthermore, the secondary boron-rich fresh water is mixed with the boron-containing desorption liquid and subjected to MVR forced evaporation and concentration to obtain a boric acid product.

2. The separation method according to claim 1, wherein Specifically include: The pH value of the high boron-lithium ratio solution is regulated to 7-12, and a first-stage homogeneous electrodialysis concentration separation is performed to produce a first-stage lithium-rich concentrated water and a first-stage boron-rich fresh water; wherein the first-stage lithium-rich concentrated water has a lithium ion concentration of 10-18 g / L, a boron ion concentration of 1-2.5 g / L, and a boron-lithium mass ratio of 0.06-0.25:

1.

3. The separation method according to claim 1, characterized in that Specifically include: The first-level lithium-rich concentrated water is diluted to obtain first-level diluted lithium-rich concentrated water; wherein the first-level diluted lithium-rich concentrated water has a lithium ion concentration of 3-6 g / L and a boron ion concentration of 0.3-0.7 g / L.

4. The separation method according to claim 1, characterized in that Specifically include: The pH value of the first-stage diluted lithium-rich concentrated water is controlled to be 3-5 for high-pressure RO concentration to produce lithium-rich RO concentrated water and low-boron RO fresh water; wherein the operating pressure of the high-pressure RO concentration is 5-10 MPa; the lithium ion concentration of the lithium-rich RO concentrated water is 8-12 g / L, and the boron ion concentration is 0.4-0.9 g / L; the lithium ion concentration of the low-boron RO fresh water is 0.2-0.3 g / L, and the boron ion concentration is 0.25-0.5 g / L; Preferably, the low-boron RO fresh water is used for adsorption and extraction of lithium.

5. The separation method according to claim 1, characterized in that Specifically include: The pH value of the lithium-rich RO concentrated water is controlled to be 3-7, and a homogeneous electrodialysis concentration separation is performed to produce a lithium-rich concentrated water and a boron-rich fresh water; wherein the lithium-rich concentrated water has a lithium ion concentration of 13-20 g / L and a boron ion concentration of 0.06-0.1 g / L; and the boron-rich fresh water has a lithium ion concentration of 0.8-1.2 g / L and a boron ion concentration of 0.5-1 g / L; Preferably, the first stage of boron-rich fresh water is used as dilution fresh water to dilute the first stage of lithium-rich concentrated water.

6. The separation method according to claim 1, characterized in that Specifically include: The pH value of the first-level boron-rich fresh water is regulated to 3-5 for secondary homogeneous electroosmotic concentration and separation to produce secondary lithium-rich concentrated water and secondary boron-rich fresh water; wherein the lithium ion concentration of the second-level lithium-rich concentrated water is 5-8 g / L, and the boron ion concentration is 0.4-1 g / L; the lithium ion concentration of the second-level boron-rich fresh water is 0.03-0.1 g / L, and the boron ion concentration is 4-4.5 g / L.

7. The separation method according to claim 1, characterized in that Specifically include: The pH value of the secondary lithium-rich concentrated water is controlled to be 3-5, and a two-stage homogeneous electrodialysis concentration separation is performed to produce a second-stage lithium-rich concentrated water and a second-stage boron-rich fresh water; wherein the lithium ion concentration in the second-stage lithium-rich concentrated water is 13-20 g / L, and the boron ion concentration is 0.06-0.1 g / L; and the lithium ion concentration in the second-stage boron-rich fresh water is 0.8-1.2 g / L, and the boron ion concentration is 0.5-1.1 g / L; Preferably, the second-stage boron-rich fresh water is used as dilution fresh water to dilute the first-stage lithium-rich concentrated water.

8. The separation method according to claim 1, characterized in that Specifically include: The first-stage lithium-rich concentrated water and the second-stage lithium-rich concentrated water are mixed and the pH value is adjusted to 10-12, and a boron removal adsorption resin is used for adsorption and desorption treatment to obtain a mixed lithium-rich concentrated water and a boron-containing desorption liquid; wherein the boron ion concentration in the mixed lithium-rich concentrated water is less than 10 ppm, and the boron concentration in the boron-containing desorption liquid is 3-5 g / L; Preferably, hydrochloric acid is used to desorb the boron removal adsorption resin after adsorption; wherein the concentration of the hydrochloric acid is 0.5-2 mol / L.

9. The separation method according to claim 1, characterized in that Specifically include: The mixed lithium-rich concentrated water is subjected to MVR forced evaporation and concentration, and then transported to the lithium precipitation section for the preparation of battery-grade lithium carbonate.

10. The separation method according to claim 1, characterized in that Specifically include: The secondary boron-rich fresh water is mixed with the boron-containing desorption liquid and subjected to MVR forced evaporation and concentration to obtain a crude boric acid product, which is then washed and dried to obtain a boric acid product; Preferably, the boric acid content in the boric acid product is greater than 99%.

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