Method for enriching rubidium from magnesium sulfate subtype salt lake brine

Abstract

The invention provides a method for enriching rubidium from magnesium sulfate subtype salt lake brine. The method comprises the following steps: evaporating the magnesium sulfate subtype salt lake brine, stopping evaporation when the potassium concentration and the magnesium concentration in the brine respectively reach 1.5-3wt% and 3-7wt%, and carrying out solid-liquid separation to obtain a first solid and a first liquid; the first liquid is diluted and then subjected to nanofiltration treatment, at least part of magnesium ions and sulfate ions in the first liquid are removed, and first concentrated water and first produced water are obtained; the first produced water is evaporated, concentrated and crystallized, sodium and potassium in the first produced water are separated out in the form of salt, the rubidium concentration is increased, evaporation is stopped when the preset rubidium concentration is reached, and second liquid, namely the rubidium-rich brine is obtained. The method has the advantages of high rubidium comprehensive recovery rate, full utilization of natural evaporation, no need of other chemical precipitators, low cost, effective reduction of the yield loss of rubidium in the whole concentration process, realization of effective enrichment of rubidium in the magnesium sulfate subtype brine, and provision of a high-quality raw material for subsequent separation of rubidium resources.

Description

Technical Field

[0001] The invention belongs to the technical field of salt lake brine treatment, and particularly relates to a method for enriching rubidium from magnesium sulfate subtype salt lake brine. Background Art

[0002] Due to its unique properties, rubidium metals and compounds are not only used in traditional fields such as electronic devices, catalysts, biochemistry and medicine, but are also widely used in high-tech fields such as aerospace, new energy, new materials and communications. Therefore, its demand is increasing. Through natural evaporation experiments, making full use of natural energy to efficiently enrich rubidium is a key step in the comprehensive utilization of salt lake resources. However, during the evaporation enrichment process, due to the complex composition of the brine system and the influence of various factors, it is difficult to continue enriching rubidium after it has been enriched to a certain level. Dispersed precipitation or entrainment in the mother liquor is serious, resulting in a waste of resources.

[0003] Rubidium in magnesium sulfate subtype salt lake brine coexists with a large amount of sodium, potassium, magnesium and other ions, making extraction extremely difficult. One of the reasons why rubidium separation in brine is difficult is that rubidium cannot be effectively enriched during the entire process of brine evaporation and concentration. Among them, the biggest influence on rubidium enrichment is the carnallite precipitated during the evaporation and crystallization of brine. In the early stage of carnallite precipitation, almost all of the rubidium enters the carnallite solid phase. For example, in most natural evaporation methods in the existing technology, when the concentration of rubidium in the liquid phase reaches a certain value, a phase chemical transition will occur, and rubidium and carnallite will form a solid solution (K(Rb)Cl·MgCl2·6H2O). At this point, further natural evaporation will not effectively enrich rubidium in the liquid phase, so most natural evaporation processes will stop at this point.

[0004] In order to avoid the appearance of carnallite during the evaporation and concentration of brine, the prior art usually uses a precipitation method to remove magnesium from the brine first, for example, using precipitants such as NaOH and Na2CO3 to make magnesium ions form Mg(OH)2 and MgCO3 precipitates. However, due to the presence of a large amount of magnesium in the brine, the consumption of NaOH and Na2CO3 is huge, and the cost generated far exceeds the value of rubidium in the brine, and a large amount of solid waste is also generated, and separation is difficult. For example, the prior art CN 115044779 A performs multi-stage evaporation crystallization on sodium sulfate subtype brine, performs solid-liquid separation before the brine reaches light brine saturation, and then adjusts the pH of the liquid brine to make the Mg in the brine 2+ Remove it in the form of Mg(OH)2 precipitation to avoid the precipitation of carnallite. This technical process is relatively complicated, the brine node is not easy to control, and NaOH solution is needed to precipitate Mg in the brine. 2+, consuming a large amount of chemical reagents. Furthermore, the Mg(OH)2 precipitate produced in this process is fine and will adsorb the scattered elements in the brine, causing the loss of Rb and a decrease in the rubidium yield. Furthermore, the filtration of the fine Mg(OH)2 particles is extremely difficult, increasing the complexity of the entire process.

[0005] It can be seen that how to effectively enrich rubidium from magnesium sulfate subtype salt lake brine is one of the urgent problems to be solved in the development and utilization of rubidium resources. Summary of the Invention

[0006] In order to solve all or part of the above technical problems, the present invention provides the following technical solutions:

[0007] One of the objects of the present invention is to provide a method for enriching rubidium from magnesium sulfate subtype salt lake brine, comprising:

[0008] S1. Evaporating magnesium sulfate subtype salt lake brine, and stopping evaporation when the potassium concentration and magnesium concentration in the brine reach 1.5-3wt% and 3-7wt%, respectively, and performing solid-liquid separation to obtain a first solid and a first liquid;

[0009] S2. diluting the first liquid and then performing nanofiltration treatment to remove at least part of the magnesium ions and sulfate ions in the first liquid to obtain a first concentrated water and a first produced water;

[0010] S3. Evaporating, concentrating and crystallizing the first produced water to precipitate sodium and potassium in the first produced water in the form of salts and increase the rubidium concentration. When the preset rubidium concentration is reached, evaporation is stopped, and solid-liquid separation is performed to obtain a second solid and a second liquid, where the second liquid is rubidium-rich brine.

[0011] The "magnesium sulfate subtype salt lake brine" described in the present invention mainly contains Na + , K + Mg 2+ 、Cl - and SO4 2- In addition to the main ions, it also contains other trace ions, including Rb+, and also including but not limited to Li + , Ca 2+ 、Cs + 、B4O7 2- 、HCO3 - and CO3 2- etc., where the brine water chemical coefficient R is 1.5-0.01,

[0012] The method provided by the present invention achieves high-yield and low-cost enrichment of rubidium through "evaporation node control-nanofiltration treatment-evaporation concentration crystallization." The existing technology uses precipitation to convert magnesium ions into precipitates such as Mg(OH)2 and MgCO3. These precipitates are small and have a high surface area, which can adsorb and entrain rare elements in the brine, causing Rb loss and thus low rubidium yield. The method provided by the present invention eliminates the need for chemical reagents to precipitate magnesium, resulting in a higher rubidium yield and reducing costs by avoiding the use of high-consumption precipitants.

[0013] When the magnesium sulfate subtype salt lake brine is evaporated to a potassium concentration of 1.5-3wt% and a magnesium concentration of 3-7wt%, the brine is close to or reaches a state of carnallites saturation and no carnallites are precipitated. During the evaporation process, the quinary system phase diagram can be used to control the brine evaporation node to ensure that the brine is close to the carnallites saturation stage and no carnallites are precipitated. On the one hand, this avoids the loss of rubidium caused by the precipitation of carnallites, and on the other hand, it can reduce the brine treatment volume of the subsequent nanofiltration process as much as possible.

[0014] In some embodiments, the method further comprises washing the first solid to obtain a first washing liquid, mixing the first washing liquid with the first liquid to obtain a first mixed liquid, and subjecting the first mixed liquid to the aforementioned nanofiltration treatment. The first solid may contain some rubidium entrained in the brine. Washing the first solid and mixing the washing liquid with the first liquid before nanofiltration can improve the final rubidium yield. The first solid primarily comprises NaCl and may also contain KCl, MgSO4·7H2O, and other components.

[0015] In some embodiments, the method further includes: returning at least a portion of the first concentrated water obtained by the nanofiltration treatment to the first mixed liquid to continue the nanofiltration treatment.

[0016] In some embodiments, the pressure of the nanofiltration treatment is 0.6 MPa to 1.5 MPa.

[0017] The nanofiltration membrane device used in the nanofiltration treatment can be a nanofiltration membrane system known in the art for removing divalent ions, particularly magnesium ions and sulfate ions, and the present invention is not particularly limited thereto. For example, the nanofiltration membrane device used may include a nanofiltration membrane assembly, a booster pump, a reflux valve, and a concentrate tank and a product water tank connected to the nanofiltration membrane assembly. The concentrate tank is used to store the first concentrate, and the product water tank is used to store the first product water. The booster pump is used to adjust the pressure of the nanofiltration treatment, for example, to control the pressure of the nanofiltration treatment to 0.6 MPa to 1.5 MPa. The reflux valve is used to allow the first concentrate to be incorporated into the first liquid or the first mixed liquid.

[0018] In some embodiments, the method further comprises: diluting the first liquid to a total salt content of 10-65 g / L, preferably 15-50 g / L, and then performing the nanofiltration treatment.

[0019] In some embodiments, the magnesium ion concentration in the first produced water obtained by the nanofiltration treatment is less than 0.05%, and the sulfate ion concentration is less than 0.03%. 2+ 、SO4 2- By controlling the concentration of divalent ions within the above-mentioned range, the system can be simplified to a chloride system, enabling the subsequent extraction of rubidium.

[0020] In some embodiments, the method further includes washing the second solid to obtain a second washing liquid, mixing the second washing liquid with the first produced water to obtain a second mixed liquid, and subjecting the second mixed liquid to evaporation, concentration, and crystallization. The second solid will contain some rubidium. Washing the second solid and mixing the washing liquid with the first produced water before evaporation, concentration, and crystallization can improve the final rubidium yield. The second solid is primarily composed of NaCl and KCl.

[0021] In some embodiments, the preset rubidium concentration is 0.01-0.10 wt%. That is, when the evaporation, concentration, and crystallization process reaches a rubidium concentration of 0.01-0.10 wt%, the process is stopped and solid-liquid separation is performed. The resulting rubidium-rich brine contains 0.01-0.10 wt% rubidium and can be used as a high-quality raw material for the production of rubidium products.

[0022] In some embodiments, the rubidium yield of the method can reach more than 80%, and in some preferred embodiments, it can reach more than 85%, which is a relatively high rubidium yield.

[0023] In some embodiments, the method further comprises a step of recovering lithium and / or potassium.

[0024] The step of recovering potassium includes: removing NaCl from the sodium salt and potassium salt precipitated from the first produced water in step S3, for example, removing NaCl by hot dissolution and cold crystallization to obtain a KCl product, thereby realizing potassium recovery.

[0025] For magnesium sulfate subtype salt lake brine, the existing technology for enriching rubidium by precipitation can only precipitate Mg 2+ , SO4 still exists in brine 2-Ions, which will cause sulfate precipitation during the evaporation and crystallization process, causing certain difficulties for the subsequent separation of lithium and potassium resources; and the method provided by the present invention removes Mg ions and sulfate ions simultaneously through nanofiltration treatment, which can achieve high-yield enrichment of rubidium and will not produce sulfate precipitation to affect the subsequent separation of lithium and potassium resources. Specifically, the present invention removes Mg ions and sulfate ions simultaneously through nanofiltration treatment to change the water chemical properties of the brine. The sodium salt and potassium salt precipitated from the first produced water in step S3 are mainly precipitated as mixed salts of KCl and NaCl. NaCl can be removed by a simple process of hot dissolution and cold crystallization to obtain a KCl product, that is, potassium recovery is achieved at the same time, the process is simple, and the yield of potassium is high. For lithium separation, the existing technology usually separates magnesium and lithium by concentrating the old brine (saturated MgCl2 solution) after potassium extraction to obtain a lithium-rich solution and the original brine adsorption to extract lithium. A large amount of carnallite minerals are precipitated during the production of potassium chloride. Carnallite minerals have a very strong hygroscopicity for brine, and brine entrainment is very serious. It is the main loss stage of lithium in the brine concentration process. Raw brine adsorption and lithium extraction is to use lithium adsorbent to adsorb and separate Li in raw brine. Although raw brine lithium extraction can avoid the loss of lithium during brine evaporation, the lithium content in raw brine is low and the brine processing volume is large. The present invention places the magnesium-lithium separation process before the precipitation of carnallite, which can avoid the main lithium loss stage, greatly reduce lithium loss, and reduce the brine processing volume. Since the brine after nanofiltration separation is mainly chloride, and the solubility of lithium chloride is much greater than that of sodium chloride and potassium chloride, lithium can be enriched in a large amount of sodium chloride and potassium chloride and precipitated. Lithium can be enriched by simple evaporation and concentration separation, that is, the rubidium-rich brine obtained in step S3 is also enriched with lithium, and lithium enrichment and recovery are achieved at the same time.

[0026] Compared with the prior art, the present invention has at least the following technical effects:

[0027] (1) The method provided by the present invention has a high rubidium yield. In some embodiments, the rubidium yield can reach 80% or even more than 85%. Compared with the method of using an alkaline precipitant to remove magnesium and enrich rubidium in the prior art, the yield can be increased by more than about 13%.

[0028] (2) The method provided by the present invention does not require the use of other chemical reagents and avoids the use of precipitants such as NaOH and Na2CO3, which can reduce costs. The solution provided by the present invention can reduce the cost by about 30% or more compared with the precipitation method of the prior art.

[0029] (3) The rubidium enrichment method provided by the present invention does not produce sulfate precipitation in the entire process, thereby solving the problem that the method of using an alkaline precipitant to remove magnesium to enrich rubidium in the prior art will produce sulfate precipitation, thereby affecting the subsequent separation of lithium and potassium resources;

[0030] (4) The rubidium enrichment method provided by the present invention is simple and easy to control, and is easy to process for production, thereby solving the problem that the fine particles of Mg(OH)2 and MgCO3 generated in the prior art are difficult to filter and remove. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application 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 this application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 This is a process flow chart for enriching rubidium from magnesium sulfate subtype salt lake brine in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching those skilled in the art to employ the present invention in various ways in virtually any appropriate detailed embodiment.

[0034] In addition, unless otherwise specified, the various raw materials used in the following examples can be purchased from the market and other channels, the various production and testing equipment used are also equipment known in the art, and the testing methods used are also methods known in the art.

[0035] Example 1

[0036] Example 1 provides a method for efficiently enriching rubidium from magnesium sulfate subtype salt lake brine. Figure 1 : is a process flow chart of this embodiment 1, which specifically includes the following steps:

[0037] S1: 57.54 kg of brine L0 from a salt lake in the Qaidam Basin was first subjected to natural evaporation. Using the quinary phase diagram, the evaporation nodes were controlled to achieve a state close to carnallite saturation without carnallite precipitation. Solid-liquid separation was then performed to obtain solid S1 (11.18 kg) and liquid L1 (17.44 kg). Solid S1 was washed with fresh water to obtain washing liquid L2 (2.3 kg).

[0038] S2: Liquid L1 and washing liquid L2 are mixed and diluted to form 197.4 kg of liquid L3. The dilution results in a salt content of 29.2 g / L. Liquid L3 is nanofiltered using a nanofiltration membrane system to produce product water L4 and concentrated water L5. During the nanofiltration process, a reflux valve allows concentrated water L5 to flow back into the nanofiltration-treated feed liquid (liquid L3).

[0039] S3, the water L4 obtained in step S2 is subjected to natural evaporation, concentration and crystallization to make at least part of the Na + and K + The product precipitates as chloride, and solid-liquid separation is performed to obtain solid S2 (1.863 kg) and liquid L6 (0.646 kg). Liquid L6 is the Rb-rich brine. Solid S2 is washed with deionized water to obtain washing liquid L7, which is then fed into the produced water L4 for cyclic evaporation, concentration, and crystallization.

[0040] In the above-mentioned process for efficiently enriching rubidium from magnesium sulfate subtype salt lake brine, the chemical compositions of the salt lake brine L0, the liquids obtained at each stage, and the solids are shown in Table 1:

[0041] Table 1

[0042]

[0043]

[0044] The rubidium yield in this embodiment is:

[0045]

[0046] The calculated yield of rubidium in the entire process is 84.5%.

[0047] Example 2

[0048] Example 2 provides a method for efficiently enriching rubidium and cesium from magnesium sulfate subtype salt lake brine, which specifically includes the following steps:

[0049] S1: 66.94 kg of deep brine L0 from a salt lake in the Qaidam Basin was first subjected to natural evaporation. Using the quinary phase diagram, the evaporation nodes were controlled to achieve a state close to carnallite saturation without carnallite precipitation. Solid-liquid separation was then performed to obtain solid S1 (18.80 kg) and liquid L1 (7.50 kg). Solid S1 was washed with fresh water to obtain washing liquid L2 (1.50 kg).

[0050] S2: Liquid L1 and washing liquid L2 are mixed and diluted to form 75 kg of liquid L3. The dilution results in a salt content of 32.94 g / L. Liquid L3 is nanofiltered using a nanofiltration membrane system to produce product water L4 and concentrated water L5. During the nanofiltration process, a reflux valve allows concentrated water L5 to flow back into the nanofiltration-treated feed liquid (liquid L3).

[0051] S3, the water L4 obtained in step S2 is subjected to natural evaporation, concentration and crystallization to make at least part of the Na + and K + It precipitates as chloride, and solid-liquid separation is performed to obtain solid S2 (0.3142 kg) and liquid L6 (0.5174 kg). Liquid L6 is Rb-rich brine. Solid S2 is washed with deionized water to obtain washing liquid L7, which is then fed into the produced water L4 for cyclic evaporation, concentration, and crystallization.

[0052] In the above-mentioned process for efficiently enriching rubidium from magnesium sulfate subtype salt lake brine, the chemical compositions of the salt lake brine L0, the liquids obtained at each stage, and the solids are shown in Table 2:

[0053] Table 2

[0054]

[0055]

[0056] The rubidium yield in this embodiment is:

[0057]

[0058] The calculated yield of rubidium in the entire process is 86.16%.

[0059] Comparative Example 1

[0060] Comparative Example 1 provides a method for enriching rubidium using an alkaline precipitant, which specifically includes the following steps:

[0061] Take 57.54 kg of brine L0 from a salt lake in the Qaidam Basin (rubidium content 0.000376 wt%), the same evaporation path as in Example 1 to obtain liquid L1 and washing liquid L2, mix L2 with L1, and the combined brine volume is 19.74 kg, of which Mg 2+ The content of Mg is 3.74wt%, according to 2+According to the stoichiometric method, 2.43 kg of NaOH is required to precipitate Mg(OH)2 in a 1:1 ratio. Since the Mg(OH)2 precipitate is difficult to filter, centrifugal separation is used to obtain 2.83 kg of wet solid Mg(OH)2. After filtering out Mg(OH)2, the remaining brine L3 is 19.24 kg, of which the rubidium content is 0.000884 wt%. L3 is further evaporated and concentrated, and solid-liquid separation is performed to obtain 0.675 kg of L4, of which the rubidium content is 0.02312 wt%.

[0062] The yield of rubidium in the whole process was calculated to be 72.1%.

[0063] The rubidium yield of the entire process in Comparative Example 1 was 72.1%, which is relatively low. This is because the resulting Mg(OH)2 precipitate has fine particles and a high specific surface area, which adsorbs and entrains rare elements in the brine, causing the loss of Rb. In addition, the fine Mg(OH)2 is difficult to filter. Compared with Comparative Example 1, the yield of Example 1 is increased by 13.3%, and there is no need to face complex processes such as filtering Mg(OH)2, thereby improving the processing efficiency.

[0064] Comparative Example 1 uses a precipitant to precipitate Mg, and 2.43 kg of NaOH is consumed when treating 57.54 kg of salt lake brine L0, which is relatively costly. When the quality of brine L0 treated is the same, compared with Comparative Example 1, Example 1 can reduce the cost by about 34%.

[0065] It can be seen that the method provided by the present invention has a high comprehensive recovery rate of rubidium, makes full use of natural evaporation, does not require the use of other chemical precipitants and has low cost, can effectively reduce the yield loss of rubidium in the entire concentration process, realizes the effective enrichment of rubidium in magnesium sulfate subtype brine, and provides high-quality raw materials for the subsequent separation of rubidium resources.

[0066] The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and are not intended to limit the present invention, the scope of which is defined solely by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0067] 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.

[0068] Although the present invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions, and / or additions may be made and that substantial equivalents may be substituted for the elements of the embodiments without departing from the spirit and scope of the present invention. Additionally, many modifications may be made to adapt specific circumstances or materials to the teachings of the present invention without departing from the scope of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for carrying out the present invention, but rather to include all embodiments within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another.

Claims

1. A method for enriching rubidium from magnesium sulfate subtype salt lake brine, characterized in that: include: S1, evaporating magnesium sulfate subtype salt lake brine, and stopping evaporation when the potassium concentration and magnesium concentration in the brine reach 1.5-3wt% and 3-7wt%, respectively, and performing solid-liquid separation to obtain a first solid and a first liquid; S2. diluting the first liquid and then performing nanofiltration treatment to remove at least part of the magnesium ions and sulfate ions in the first liquid to obtain a first concentrated water and a first produced water; S3. Evaporating, concentrating and crystallizing the first produced water to precipitate sodium and potassium in the first produced water in the form of salts and increase the rubidium concentration. When the preset rubidium concentration is reached, evaporation is stopped, and solid-liquid separation is performed to obtain a second solid and a second liquid, where the second liquid is rubidium-rich brine.

2. The method according to claim 1, characterized in that Also includes: The first solid is washed to obtain a first washing liquid, the first washing liquid is mixed with a first liquid to obtain a first mixed liquid, and the first mixed liquid is subjected to the nanofiltration treatment.

3. The method according to claim 2, characterized in that Also includes: At least a portion of the first concentrated water obtained by the nanofiltration treatment is refluxed into the first mixed liquor to continue the nanofiltration treatment.

4. The method according to claim 1, wherein: The pressure of the nanofiltration treatment is 0.6 MPa to 1.5 MPa.

5. The method according to claim 1, wherein Also includes: The first liquid is diluted to a total salt content of 10-65 g / L, and then the nanofiltration treatment is performed.

6. The method according to claim 1 or 3, characterized in that The first produced water obtained by the nanofiltration treatment has a magnesium ion concentration of less than 0.05% and a sulfate ion concentration of less than 0.03%.

7. The method according to claim 1, characterized in that Also includes: The second solid is washed to obtain a second washing liquid, the second washing liquid is mixed with the first produced water to obtain a second mixed liquid, and the second mixed liquid is subjected to the evaporation, concentration and crystallization.

8. The method according to claim 1, wherein: The preset rubidium concentration is 0.01-0.10 wt %.

9. The method according to claim 1, wherein: The rubidium yield of the method is above 80%.

10. The method according to claim 1, wherein: The hydrochemical coefficient R of the magnesium sulfate subtype salt lake brine is 1.5-0.01.

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