Pretreatment method of high-magnesium boron-containing brine and application thereof

Abstract

The application relates to the technical field of lithium extraction from brine, and provides a pretreatment method of high-magnesium boron-containing brine and application thereof. Before entering a lithium extraction device by electrodialysis, the high-magnesium boron-containing brine is pretreated, and the pretreatment method comprises the following steps: diluting the high-magnesium boron-containing brine by adding water to obtain diluted high-magnesium boron-containing brine; adding crystal seeds into the diluted high-magnesium boron-containing brine, stirring, and then standing and settling to obtain supernatant, and the supernatant is first pretreated high-magnesium boron-containing brine; and adding acid into the first pretreated high-magnesium boron-containing brine to adjust the pH value to 5.0-6.5. By the above method, the concentration of boron ions in the brine can be reduced, the influence of magnesium borate precipitation on the electrodialysis membrane can be reduced, and the stability and continuity in the lithium extraction process by electrodialysis can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium extraction from brine, in particular to a pretreatment method of high-magnesium and boron-containing brine and application thereof. BACKGROUND

[0002] More than 70% of the world's lithium resource industrial reserves come from salt lakes. With the development of new energy vehicles, the demand for lithium resources is growing rapidly, which has attracted more attention to lithium extraction technology from salt lakes. There are many methods for extracting lithium from salt lake brine, such as evaporation crystallization, precipitation, extraction, adsorption, calcination, electrodialysis and electrochemical deintercalation. Electrodialysis is a lithium extraction operation that separates or enriches ions from lithium-containing solution using the selectivity of ion exchange membrane driven by potential difference. Currently, lithium extraction by electrodialysis has achieved industrialization, with stable production and good economic benefits.

[0003] Electrodialysis uses lithium-containing old brine as raw material for electrodialysis operation. The lithium-containing old brine usually contains a large amount of magnesium ions and boron ions (high-magnesium and boron-containing brine). During the electrodialysis process, magnesium borate is often precipitated to contaminate the electrodialysis membrane, causing a decrease in current efficiency, an increase in energy consumption, a decrease in lithium extraction efficiency, and a decrease in membrane life, which seriously affects the stability and continuity of the lithium extraction process by electrodialysis. In order to solve the problem of magnesium borate precipitation and contamination of the electrodialysis membrane, high-concentration acid is usually added to adjust the pH of the high-magnesium and boron-containing brine to 1-2 for acidification and boron removal. However, this method consumes a large amount of high-concentration acid, which not only increases the cost but also causes environmental pollution.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] The present application aims to provide a pretreatment method of high-magnesium and boron-containing brine and application thereof. The purpose is to reduce the boron content in high-magnesium and boron-containing brine and inhibit the precipitation of magnesium borate, thereby reducing the precipitation of magnesium borate in the lithium extraction process by electrodialysis, preventing the contamination of the electrodialysis membrane, prolonging the service life of the electrodialysis membrane, and improving the stability and continuity of the lithium extraction process by electrodialysis.

[0006] In a first aspect, the present application provides a pretreatment method of high-magnesium and boron-containing brine, which comprises the following steps:

[0007] S1: diluting the high-magnesium and boron-containing brine with water to obtain diluted high-magnesium and boron-containing brine;

[0008] S2: adding seed crystals to the diluted high-magnesium and boron-containing brine, stirring and then standing and settling, and taking the supernatant to obtain first pretreated high-magnesium and boron-containing brine;

[0009] S3: adding acid into the first pretreated high-magnesium boron-containing brine to adjust the pH to 5.0-6.5, to obtain second pretreated high-magnesium boron-containing brine.

[0010] In an optional embodiment, the volume ratio of the high-magnesium boron-containing brine and the water dilution is 1: (0.1-2).

[0011] In an optional embodiment, the seed crystal is a magnesium borate salt, including at least one of inesite, priceite, magnesium hexaborate, pinite, chongite and tsumebite.

[0012] In an optional embodiment, the mass ratio of boron in the seed crystal to boron in the dilution high-magnesium boron-containing brine is (0.001-0.05):1.

[0013] In an optional embodiment, the stirring time is 1h-48h, and the stirring temperature is -15℃ to 25℃.

[0014] The standing and settling time is 7d-60d, and the standing and settling temperature is -15℃ to 25℃.

[0015] In an optional embodiment, the step S2 comprises: adding seed crystal into the dilution high-magnesium boron-containing brine, stirring, standing and settling, taking supernatant for ultrafiltration treatment, to obtain first pretreated high-magnesium boron-containing brine.

[0016] In an optional embodiment, the acid comprises at least one of hydrochloric acid, sulfuric acid and nitric acid.

[0017] In a second aspect, the application provides an application of the pretreatment method of high-magnesium boron-containing brine as described in the first aspect, which is used in the technical field of electrodialysis lithium extraction, and the high-magnesium boron-containing brine is a lithium-containing magnesium saturated solution.

[0018] The pretreatment method of high-magnesium boron-containing brine can reduce the boron content in the brine, thereby effectively inhibiting the precipitation of solid magnesium borate salt in the brine during electrodialysis. The dilution of the high-magnesium boron-containing brine and the addition of seed crystal synergistically accelerate the precipitation of solid magnesium borate salt in the brine, reducing the concentration of boron ions and magnesium ions in the brine; and the addition of acid to adjust the brine to be weakly acidic can further inhibit the precipitation of magnesium borate salt. The method is simple, efficient, energy-saving and environmentally friendly, can prolong the service life of the electrodialysis membrane, and is conducive to improving the stability and continuity of the electrodialysis lithium extraction process. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation to the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0020] Figure 1 Process flow diagram of the embodiment of the present application;

[0021] Figure 2 Current density change diagram of the embodiment 1 of the present application in the process of lithium extraction by electrodialysis;

[0022] Figure 3 Current density change diagram of the comparative example 1 of the present application in the process of lithium extraction by electrodialysis. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will clearly and completely describe the technical solutions in the embodiments of the present application. The known technologies, methods and devices for the related field may not be discussed in detail, but in appropriate cases, the said technologies, methods and devices should be regarded as a part of the specification. The specific conditions are not mentioned in the embodiments, and the conventional conditions or the conditions suggested by the manufacturer are adopted. The reagents or instruments are not mentioned by the manufacturer, and are all the conventional products which can be purchased in the market.

[0024] The pretreatment method and application of high-magnesium boron-containing brine provided by the present application will be described in detail below.

[0025] The present application provides a pretreatment method of high-magnesium boron-containing brine, which comprises the following steps:

[0026] S1: diluting the high-magnesium boron-containing brine with water to obtain diluted high-magnesium boron-containing brine;

[0027] S2: adding seeds to the diluted high-magnesium boron-containing brine, stirring and then standing and settling, and taking the supernatant to obtain first pretreated high-magnesium boron-containing brine;

[0028] S3: adding acid to the first pretreated high-magnesium boron-containing brine to adjust the pH to 5.0-6.5 to obtain second pretreated high-magnesium boron-containing brine.

[0029] Specifically, the present application will be described one by one for each of the above steps to obtain the treated high-magnesium boron-containing brine.

[0030] In some embodiments, the volume ratio of the high-magnesium boron-containing brine and water for dilution is 1: (0.1-2), preferably 1: (0.5-1).

[0031] The high-magnesium boron-containing brine system has abnormal phenomena such as "supersaturation solubility" and "dilution into salt", and the present application promotes the precipitation of magnesium borate by diluting the high-magnesium boron-containing brine. The principle is that the high-magnesium boron-containing brine forms high-concentration brine after evaporation and concentration, and the borate anion mainly exists in the form of high-polymer boron-oxygen complex anion, which is not easy to form salt with magnesium ions and precipitate; dilution with water causes depolymerization between the high-polymer boron-oxygen complex anion and water in the solution to generate low-polymer boron-oxygen complex anion, which is more likely to form salt with magnesium ions and crystallize and precipitate. At the same time, according to the acid-base balance theory, the magnesium borate salt is a strong base and weak acid salt, and has a large solubility in an acidic environment; the high-polymer boron-oxygen complex anion releases OH - ions during the water-dilution depolymerization process, which increases the pH of the brine system and reduces the solubility of magnesium borate in the diluted high-magnesium boron-containing brine, so that the magnesium borate salt is more likely to precipitate.

[0032] The volume ratio of the high-magnesium boron-containing brine and water will affect the precipitation of magnesium borate. When the mixed dilution water is too much, the boron concentration in the diluted high-magnesium boron-containing brine decreases, resulting in a decrease in the supersaturation concentration and a decrease in the precipitation rate of magnesium borate; when the mixed dilution water is too little, the viscosity of the diluted high-magnesium boron-containing brine is high, the diffusion effect is weakened, and the precipitation rate of magnesium borate is reduced.

[0033] In some embodiments, the seed crystal is a magnesium borate salt, including at least one of inesite, priceite, magnesium hexaborate, pinite, chongite, and tisinite.

[0034] In some embodiments, the mass ratio of boron in the seed crystal to boron in the diluted high-magnesium boron-containing brine is (0.001-0.05):1, preferably (0.001-0.01):1.

[0035] In some embodiments, the stirring time is 1h-48h, for example, it can be any one of 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 20h, 28h, 38h, 48h or a range value between any two of them; the stirring temperature is -15℃ to 25℃, for example, it can be any one of -15℃, -10℃, -5℃, 0℃, 4℃, 5℃, 10℃, 15℃, 20℃, 25℃ or a range value between any two of them.

[0036] In some embodiments, the time for standing is 7d-60d, for example, it can be any one of 7d, 10d, 15d, 20d, 25d, 30d, 35d, 60d or a range value between any two of them; the standing temperature is-15℃ to 25℃, for example, it can be any one of-15℃, -10℃, -5℃, 0℃, 4℃, 5℃, 10℃, 15℃, 20℃, 25℃ or a range value between any two of them.

[0037] Lower stirring temperature or standing temperature can cause the solubility of magnesium borate in the diluted high-magnesium boron-containing brine to decrease, which is beneficial to the crystallization and precipitation of magnesium borate salt. However, if the stirring temperature or standing temperature is too low, impurity salts such as magnesium sulfate and magnesium chloride are easily precipitated, which can cause the loss of lithium in the brine during the precipitation of the impurity salts. The dilution and salting often need a long time of standing to promote the precipitation of magnesium borate salt. In the present application, the addition of crystal seeds to the diluted high-magnesium boron-containing brine can further accelerate the precipitation of magnesium borate salt.

[0038] In some embodiments, crystal seeds are added to the diluted high-magnesium boron-containing brine, and after stirring, standing and sedimentation, the supernatant is taken for ultrafiltration treatment to obtain a first pretreated high-magnesium boron-containing brine.

[0039] In some embodiments, acid is added to the first pretreated high-magnesium boron-containing brine to adjust the pH to 5.0-6.5, for example, the pH can be any one of 5.0, 5.2, 5.4, 5.8, 6.0, 6.2, 6.4, 6.5 or a range value between any two of them.

[0040] Similarly, according to the acid-base balance theory, the solubility of magnesium borate salt can be greatly improved in an acidic environment, thereby effectively reducing the precipitation of magnesium borate salt in the process of lithium extraction by electrodialysis. Therefore, the addition of a small amount of acid to the first pretreated high-magnesium boron-containing brine to make the system weakly acidic with a pH of 5.0-6.5 can reduce the problems such as membrane pollution, membrane life reduction and membrane performance attenuation caused by the precipitation of magnesium borate salt.

[0041] In some embodiments, the acid includes at least one of hydrochloric acid, sulfuric acid and nitric acid.

[0042] The present application also provides an application of the pretreatment method of high-magnesium boron-containing brine in the technical field of lithium extraction by electrodialysis. The pretreated high-magnesium boron-containing brine is placed in a lithium extraction by electrodialysis device to prepare a high-lithium-content solution by electrodialysis separation. Then, the high-lithium-content solution is subjected to steps such as deep impurity removal, concentration, lithium precipitation, magnetic removal and drying to obtain lithium carbonate.

[0043] In some embodiments, the high-magnesium boron-containing brine is a lithium-containing magnesium saturated solution, and the concentration of boron ions is preferably 3g / L-15g / L.

[0044] The features and characteristics of the present application are further described in detail below in conjunction with the accompanying drawings, examples and comparative examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

[0045] Example 1

[0046] The present example provides a pretreatment method of high-magnesium boron-containing brine, comprising the following steps:

[0047] S1: Take 400L of high-magnesium boron-containing brine from Dongtai lithium resource old brine salt field and mix with water in a volume ratio of 1:1 to obtain diluted high-magnesium boron-containing brine.

[0048] S2: Add 100g of hydroboracite to the diluted high-magnesium boron-containing brine, slowly stir at 15℃ for 4h, then stand for 15d, take the supernatant for ultrafiltration treatment to obtain first pretreated high-magnesium boron-containing brine.

[0049] S3: Add hydrochloric acid to the first pretreated high-magnesium boron-containing brine to adjust its pH to 6.22 to obtain second pretreated high-magnesium boron-containing brine.

[0050] The precipitation rate of boron is 18.6%.

[0051] The accompanying drawings of the specification Figure 2 The second pretreated high-magnesium boron-containing brine obtained in the present example is shown in the current density change graph during the 256h continuous electrodialysis lithium extraction process at a constant voltage in Test Example 3. It can be seen that the current density change is relatively stable, which means that the electrodialysis lithium extraction process is stable and runs, and there is no magnesium borate precipitation in the membrane and pipeline, circulating tank and the like.

[0052] Example 2

[0053] The present example provides a pretreatment method of high-magnesium boron-containing brine, comprising the following steps:

[0054] S1: Take 20L of high-magnesium boron-containing brine from Bolivia Uyuni Salt Lake and mix with water in a volume ratio of 1:1 to obtain diluted high-magnesium boron-containing brine.

[0055] S2: Add 5g of Zhang's boron-magnesium stone and 5g of trillium boron-magnesium stone to the diluted high-magnesium boron-containing brine, slowly stir at 5℃ for 6h, then stand for 25d, take the supernatant for ultrafiltration treatment to obtain first pretreated high-magnesium boron-containing brine.

[0056] S3: Add nitric acid to the first pretreated high-magnesium boron-containing brine to adjust its pH to 6.07 to obtain second pretreated high-magnesium boron-containing brine.

[0057] The precipitation rate of boron is 41.5%.

[0058] Example 3

[0059] The embodiment provides a pretreatment method of high-magnesium boron-containing brine, which comprises the following steps:

[0060] S1: 400 L of high-magnesium boron-containing brine from Uyuni Salt Lake in Bolivia and water are mixed at a volume ratio of 1:2 to obtain diluted high-magnesium boron-containing brine.

[0061] S2: 1360 g of hydroboracite is added to the diluted high-magnesium boron-containing brine, and then the mixture is slowly stirred at -15 DEG C for 48 h, and then is left to settle for 60 d; the supernatant is taken and subjected to ultrafiltration treatment to obtain first pretreated high-magnesium boron-containing brine.

[0062] S3: hydrochloric acid is added to the first pretreated high-magnesium boron-containing brine to adjust the pH of the first pretreated high-magnesium boron-containing brine to 6.5, and then second pretreated high-magnesium boron-containing brine is obtained.

[0063] The boron precipitation rate is 15.11%.

[0064] Example 4

[0065] The embodiment provides a pretreatment method of high-magnesium boron-containing brine, which comprises the following steps:

[0066] S1: 400 L of high-magnesium boron-containing brine from old brine salt field of Dongtai lithium resources and water are mixed at a volume ratio of 1:0.1 to obtain diluted high-magnesium boron-containing brine.

[0067] S2: 18.2 g of zhans boracite is added to the diluted high-magnesium boron-containing brine, and then the mixture is slowly stirred at 25 DEG C for 1 h, and then is left to settle for 7 d; the supernatant is taken and subjected to ultrafiltration treatment to obtain first pretreated high-magnesium boron-containing brine.

[0068] S3: hydrochloric acid is added to the first pretreated high-magnesium boron-containing brine to adjust the pH of the first pretreated high-magnesium boron-containing brine to 5.0, and then second pretreated high-magnesium boron-containing brine is obtained.

[0069] The boron precipitation rate is 11.10%.

[0070] Comparative Example 1

[0071] The embodiment does not pretreat the high-magnesium boron-containing brine.

[0072] The accompanying drawings of the specification Figure 3 The current density change graph of the high-magnesium boron-containing brine in the comparative example 1 in the process of the lithium electrodialysis of the test example 3 at a constant voltage for 256 h can be seen. As the lithium electrodialysis process proceeds, the current density shows a downward trend, and at the same time, the magnesium borate is precipitated when the mold stack is checked, the membrane and the pipeline, the circulating tank and the like.

[0073] Test Example 1: Ion concentration test

[0074] The ion concentration in the solution was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES), and the test results are shown in Tables 1-4.

[0075] Test Example 2: Calculation of boron precipitation rate

[0076]

[0077] The boron precipitation rate ω was calculated using the above formula (B) , wherein is the mass of the precipitated solid (g), is the content of B in the precipitated solid (%), is the mass of the added seed crystal (g), is the content of B in the seed crystal (%), is the B content of the feed brine (g / L), is the volume of the feed brine (L).

[0078] Test Example 3

[0079] A lithium electrodialysis device with a single membrane effective area of 0.02 m 2 containing 40 pairs of electrodialysis membrane stacks was used to continuously electrodialyze lithium from the brine obtained in the above examples and comparative examples for 256 h under a constant voltage. The membrane pair voltage for the electrodialysis lithium extraction was 0.5 V, and the lithium extraction temperature was 33°C.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] Table 3

[0085]

[0086] Table 4

[0087]

[0088] From Tables 1-4, it can be seen that the high-magnesium boron-containing brine of the examples will crystallize and precipitate magnesium borate to varying degrees after dilution and the addition of seed crystals, and the boron ion concentration in the first pretreated high-magnesium boron-containing brine obtained after ultrafiltration is significantly reduced, which is beneficial to reducing the precipitation of magnesium borate salt during electrodialysis.

[0089] The above merely describes the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily conceived by those skilled in the art, and all such changes and replacements fall within the protection scope and disclosure scope of the present application.

Claims

1. A pretreatment method for high-magnesium boron-containing brine, characterized in that, The preprocessing method includes the following steps: S1: Dilute high-magnesium boron-containing brine with water to obtain diluted high-magnesium boron-containing brine; S2: Add seed crystals to the diluted high-magnesium boron brine, stir, let it stand to settle, and take the supernatant to obtain the first pretreated high-magnesium boron brine; the seed crystals are magnesium borate salts, and the mass ratio of boron in the seed crystals to boron in the diluted high-magnesium boron brine is (0.001-0.05):1; the stirring time is 1h-48h; S3: Add acid to the first pretreated high-magnesium boron-containing brine to adjust its pH to 5.0-6.5 to obtain the second pretreated high-magnesium boron-containing brine.

2. The pretreatment method for high-magnesium boron-containing brine according to claim 1, characterized in that, The volume ratio of the high-magnesium boron brine to water dilution is 1:(0.1-2).

3. The pretreatment method for high-magnesium boron-containing brine according to claim 1 or 2, characterized in that, The seed crystals include at least one of the following: hydrous boromagnesia, kuhnite, magnesium hexaborate, columnar boromagnesia, zhang's boromagnesia, and trigonal boromagnesia.

4. The pretreatment method for high-magnesium boron-containing brine according to claim 1, characterized in that, Step S2 satisfies at least one of the following conditions ①-②: ① The stirring temperature is from -15℃ to 25℃; ②The settling time is 7-60 days, and the settling temperature is -15℃ to 25℃.

5. The pretreatment method for high-magnesium boron-containing brine according to claim 1, characterized in that, Step S2 includes: adding seed crystals to the diluted high-magnesium boron brine, stirring and allowing it to settle, taking the supernatant for ultrafiltration to obtain the first pretreated high-magnesium boron brine.

6. The pretreatment method for high-magnesium boron-containing brine according to claim 1, characterized in that, The acid includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

7. An application of the pretreatment method for high-magnesium boron-containing brine according to claim 1, characterized in that, The pretreatment method for high-magnesium boron-containing brine is used in the field of electrodialysis lithium extraction technology, wherein the high-magnesium boron-containing brine is a magnesium-saturated solution containing lithium.

Images