Method and device for utilizing lithium precipitation waste liquid

Abstract

The invention provides a method and a device for utilizing lithium precipitation waste liquid. The method comprises the steps that S1, the lithium precipitation waste liquid is subjected to boron removal treatment, boron-removed waste liquid and resin regeneration boron-containing enriched liquid are obtained, the lithium precipitation waste liquid contains sodium ions, carbonate ions, chloride ions and / or sulfate ions and boron ions, and the concentration of lithium ions in the lithium precipitation waste liquid is smaller than 10.5 ppm; s2, the boron-removed waste liquid enters a nanofiltration membrane system to be separated, and concentrated water and permeate liquid are obtained; and S3, adjusting the pH value of the permeate liquid, and pumping the permeate liquid into a bipolar membrane electrodialysis system to obtain an acid liquid and an alkali liquid. The lithium precipitation waste liquid is subjected to boron removal treatment and boron regeneration, boron resources in the waste liquid are recycled, and the enriched boron solution is used for preparing borax; and then the wastewater enters a nanofiltration membrane system, a sodium carbonate solution in the wastewater is separated out, residual permeate enters a bipolar membrane electrodialysis system, and acid liquor and alkali liquor are obtained.

Description

TECHNICAL FIELD

[0001] The application relates to lithium extraction from salt lake brine and efficient comprehensive utilization of salt lake resources, in particular to a lithium precipitation waste liquid utilization method and device. BACKGROUND

[0002] Although the industrial extraction of sodium, potassium, lithium and magnesium elements from salt lake resources has been realized, there are still systematic defects in the aspect of green and cyclic development. Taking the lithium extraction process as an example, the existing industrial-grade lithium precipitation mother liquor recovery technology (including the sunning method, the adsorption method and the extraction method) generally has the problem of process chain breakage: the lithium precipitation waste liquid is generally treated by the crude method of pH neutralization and external discharge or return to the salt field, which not only causes residual loss of lithium components, but also causes the associated boron and magnesium valuable elements to enter the tail brine system without being effectively extracted. It is particularly worth noting that the salt lake boron resources have a low comprehensive utilization rate due to the lack of adaptive industrial extraction technology, and the boron-rich intermediate products generated in the development process are mostly abandoned as industrial solid waste, which not only causes waste of strategic resources, but also poses a potential threat to the ecological environment of the plateau salt lake. In the existing technical system, the resource synergistic utilization mechanism has not been established, and the by-products of each process are difficult to be converted into raw materials for the downstream process, which seriously restricts the realization of the efficient utilization of all components of salt lake resources and the cyclic economy mode. Therefore, it has become a core proposition to break through the technical bottleneck of green development of salt lake resources to build a salt lake element cascade extraction system based on the directional conversion of by-products.

[0003] In the lithium carbonate preparation process of salt lake brine, the lithium precipitation waste liquid formed after the lithium recovery of the lithium precipitation mother liquor has a typical high-alkali and high-carbonate characteristic system, the lithium ion concentration of which is reduced to below 10 ppm, the boron ion concentration is 100-150 mg / L, the carbonate concentration is as high as 9.9-19 g / L, the hydroxyl ion concentration is between 2.0-4.0 g / L, and the pH value is in the range of 9.5-13. The existing process has double resource waste: on the one hand, the high-value carbonate in the waste liquid is not directionally recovered, and a large amount of acid agent needs to be consumed for neutralization treatment, which not only increases the production cost, but also causes carbon footprint due to CO2 emission; on the other hand, the boron resources are lost due to the lack of adaptability of the existing recovery technology. In the current main technology for extracting boron from salt lakes, the precipitation method is limited by high boron concentration and has a recovery rate of less than 70%; the adsorption method is difficult to handle medium and high concentration boron systems due to the limitation of material adsorption capacity (usually <20 mg / g); the extraction / flotation method can achieve a boron extraction efficiency of more than 80%, but there is a secondary pollution risk caused by the loss of reagents; the membrane separation technology has the advantage of selectivity, but the investment cost of the membrane assembly is high and there is a problem of membrane pollution and decay in long-term operation. Therefore, the development of a process coupling system based on the characteristics of the lithium precipitation tail brine realizes the directional enrichment of boron, the in-situ conversion of carbonate and the acid-base synergistic regulation technology, realizes the recovery of valuable resources and the near-zero discharge of waste liquid, realizes the comprehensive development and green and cyclic development, and puts forward new thinking for the construction of a world-class salt lake industrial base.

[0004] In the prior art system, there are the following technologies for extracting boron resources from lithium extraction tail brine of salt lake. For example, patent technology CN118206131A discloses a production system for preparing borax from lithium extraction tail brine of salt lake and its use method. The invention uses carbon alkali method + membrane separation to solve the problems of low comprehensive yield and environmental pollution in the current brine boron extraction. However, the precipitation method is suitable for high content boron-containing brine and the total yield is not high. The precipitation of impurity ions and the high-temperature separation operation of the rotary membrane separation device increase the energy consumption of the system, and high temperature accelerates the aging of the membrane material. Patent technology CN118439636A discloses a method for comprehensive utilization of lithium resource recovery type salt lake brine. It proposes a "magnesium oxide pretreatment + membrane method for boron extraction" synergistic process. Although lithium and boron are extracted step by step through adsorption-filtration coupling, the process chain has multiple bottlenecks, the pretreatment cost increases, and the enrichment of brucite increases the loss rate of lithium, which exposes the defects of the existing system in the selectivity of the multi-ion coupling system. Moreover, the synergistic mechanism of boron enrichment process and lithium loss inhibition has not been established, making it difficult to break through the economic efficiency of resource recovery.

[0005] In the prior art system, there are the following technologies for resource utilization of lithium precipitation mother liquor. For example, patent technology CN214060200U discloses a salt lake lithium extraction system and method based on membrane separation, in which the pH value of the lithium precipitation mother liquor is adjusted to 5-6 for lithium-sodium adsorption separation, and then the pH value of the lithium-removed liquid is adjusted to 3-5 for bipolar membrane electrodialysis to prepare acid and base. For example, patent technology CN116239132A discloses a method for recovering carbonate in the preparation of battery-grade lithium carbonate from salt lake brine. The patent uses nanofiltration membrane to recover carbonate and lithium in the lithium precipitation mother liquor simultaneously. The above-mentioned method discloses a method for recovering valuable resources from lithium precipitation mother liquor, but there are problems of carbon dioxide emission and resource waste. According to the public data, the solubility of lithium carbonate at room temperature is 1.33g / 100mL. Since the lithium carbonate in the lithium precipitation mother liquor is a saturated solution, the simultaneous recovery of carbonate and lithium has the problem of lithium carbonate scaling on the membrane surface. At the same time, too high a solution pH will reduce the service life of the membrane. In order to ensure the yield of valuable lithium resources, a large amount of process water needs to be added for dialysis.

[0006] In the current lithium extraction technology field, many existing methods have significant shortcomings. The present invention aims to break through these limitations and innovatively combines traditional adsorption method with new membrane separation process to achieve simultaneous extraction of boron and sodium carbonate in lithium extraction waste liquid. This method focuses on optimizing the operation process and process steps, and selects a resin with excellent selectivity and renewability to efficiently treat low-boron lithium extraction waste liquid. After boron extraction is completed, a new type of membrane system is used in combination with dialysis nanofiltration technology to further recover carbonate in the waste liquid, thereby greatly improving the comprehensive utilization rate of various resources in lithium extraction waste liquid and providing a more efficient and environmentally friendly solution for the sustainable development of lithium extraction industry. SUMMARY

[0007] The main purpose of the present application is to provide a lithium precipitation waste liquid utilization method and device to solve the problem of large water resource consumption and low recovery utilization efficiency in the lithium precipitation waste liquid recovery process in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a lithium precipitation waste liquid utilization method is provided, which comprises: step S1, performing boron removal treatment on the lithium precipitation waste liquid to obtain boron-removed waste liquid and resin regeneration boron-rich liquid, the lithium precipitation waste liquid containing sodium ions, carbonate ions, chloride ions and / or sulfate ions and boron ions, and the concentration of lithium ions in the lithium precipitation waste liquid being less than 10.5 ppm; step S2, allowing the boron-removed waste liquid to enter a nanofiltration membrane system for separation to obtain concentrated water and permeate; and step S3, pumping the permeate into a bipolar membrane electrodialysis system after adjusting the pH value of the permeate to obtain acid liquid and alkali liquid.

[0009] Further, the lithium precipitation waste liquid is the waste liquid after lithium extraction or lithium adsorption of the lithium precipitation mother liquor in the lithium carbonate preparation process.

[0010] Preferably, in the lithium precipitation waste liquid, the concentration of carbonate is 9.5-19 g / L, and the concentration of hydroxide is 2.0-4.0 g / L.

[0011] Preferably, the pH value of the lithium precipitation waste liquid is 9.5-13.

[0012] Further, step S1 comprises: first adjusting the pH value of the lithium precipitation waste liquid to 9.5-10, and then performing boron removal treatment.

[0013] Preferably, the pH adjusting agent for adjusting the pH value is any one or more of hydrochloric acid, nitric acid and carbon dioxide.

[0014] Preferably, in the lithium precipitation waste liquid, the concentration of sodium ions is 40-90 g / L, the concentration of carbonate ions is 9.9-19 g / L, the concentration of boron ions is 100-500 mg / L, and the concentration of chloride ions is 40-120 g / L.

[0015] Further, the boron removal treatment is performed by using a resin boron removal system.

[0016] Preferably, the concentration of boron ions in the boron-removed waste liquid is 0-5 mg / L.

[0017] Preferably, in the boron-removed waste liquid, the concentration of sodium ions is 40-60 g / L, the concentration of carbonate ions is 9.9-19 g / L, and the concentration of chloride ions is 20-100 g / L.

[0018] Further, the concentration of boron ions in the resin regeneration boron-rich liquid is 100-600 mg / L; and preferably, the resin regeneration boron-rich liquid is adjusted to have a pH value of 10 for configuring borax (Na2B4O7) for a lithium precipitation system.

[0019] Further, the concentration of carbonate in the concentrated water is 20-60 g / L, the concentration of sodium ion is 30-80 g / L, and the concentration of chlorine ion is 5-30 g / L; preferably, the concentration of boron ion in the concentrated water is 0-10 mg / L; preferably, the concentrated water is used to configure a sodium carbonate solution in the lithium precipitation system;

[0020] Further, the concentration of carbonate in the concentrated water is 20-60 g / L, the concentration of sodium ion is 30-80 g / L, and the concentration of chlorine ion is 5-30 g / L; preferably, the concentration of boron ion in the concentrated water is 0-10 mg / L; preferably, the concentrated water is used to configure a sodium carbonate solution in the lithium precipitation system;

[0021] Further, the nanofiltration membrane of the nanofiltration membrane system is an alkali-resistant high-pressure membrane, and preferably, the pore size of the nanofiltration membrane is 1-2 nm.

[0022] Further, in step S3, the pH value of the permeate is adjusted to 3-4.

[0023] Further, in step S3, 0.40-0.55 m 3 acid solution, the concentration of the acid solution is 1.9-2.5 mol / L; preferably, the acid solution is used in the system process before the lithium extraction from salt lake brine by the adsorption method;

[0024] Further, in step S3, 0.40-0.55 m 3 alkali solution, the concentration of the alkali solution is 1.9-2.5 mol / L; preferably, the alkali solution is used in the system process before the lithium extraction from salt lake brine by the adsorption method.

[0025] According to another aspect of the present application, a device for implementing any of the above-mentioned utilization methods of the lithium precipitation waste liquid is provided, comprising: a boron removal resin system configured to perform boron removal treatment on the lithium precipitation waste liquid to obtain a boron-removed waste liquid; a nanofiltration membrane system configured to separate the boron-removed waste liquid into concentrated water and permeate; and a bipolar membrane electrodialysis system configured to convert the permeate into an acid solution and an alkali solution.

[0026] By applying the technical solution of the present application, the lithium precipitation waste liquid is subjected to boron removal treatment and boron regeneration, the boron resource in the waste liquid is recovered, the enriched boron solution is subjected to preparation of borax, and then the lithium precipitation waste liquid enters the nanofiltration membrane system, the sodium carbonate solution is separated therefrom, and the remaining permeate enters the bipolar membrane electrodialysis system to obtain an acid solution and an alkali solution. The recovered boron in the process can be used for preparation of boric acid or borax, and the sodium carbonate solution, the acid solution and the alkali solution can be applied in the lithium extraction process from salt lake brine, so as to fully realize the resource utilization and zero emission of the lithium precipitation waste liquid. The technical solution can reduce the production cost of lithium carbonate prepared by lithium extraction from salt lake, reduce the emission of carbon dioxide, further reduce the production cost, and has considerable economic benefits, and is suitable for industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings, which form a part of this specification, are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification. The drawings illustrate one exemplary embodiment of the application and, together with the description, serve to explain the application. In the drawings:

[0028] Figure 1 A technical process flow diagram of a lithium precipitation waste liquid utilization method according to an embodiment of the application is shown. DETAILED DESCRIPTION

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] As analyzed in the background of the present application, in the prior art, after recovering lithium from the lithium precipitation mother liquor, the lithium precipitation waste liquid is adjusted to neutral pH and then discharged or returned to the salt field system for intercrystalline brine ore dissolution. On the one hand, a large amount of acid is consumed, and on the other hand, a large amount of carbonate in the waste liquid is not fully utilized, which further causes associated boron, magnesium and other valuable elements to enter the tail halogen system without being effectively extracted, resulting in waste of resources. Or, the carbonate and lithium in the lithium precipitation mother liquor are recovered synchronously. Due to the low solubility of lithium carbonate, lithium carbonate is prone to scale on the membrane surface, affecting the service life of the equipment. In order to prevent lithium carbonate from scaling, a large amount of process water is required, so the process effect is not good and the cost performance is low. Or, boron elements are extracted from tail halogen for lithium extraction to prepare borax. This process is suitable for a high-boron system with low total yield and high system energy consumption. Based on this, the present application provides a lithium precipitation waste liquid utilization method and device.

[0031] According to a typical embodiment of the present application, a lithium precipitation waste liquid utilization method is provided, which includes: step S1, performing boron removal treatment on the lithium precipitation waste liquid to obtain a boron-removed waste liquid, the lithium precipitation waste liquid containing sodium ions, carbonate ions, chloride ions and / or sulfate ions, and the concentration of lithium ions in the lithium precipitation waste liquid being less than 10.5 ppm and the concentration of boron ions being 100-500 ppm; step S2, causing the boron-removed waste liquid to enter a nanofiltration membrane system for separation to obtain concentrated water and permeate; and step S3, adjusting the pH value of the permeate and then pumping it into a bipolar membrane electrodialysis system to obtain an acid liquid and an alkali liquid.

[0032] The application first carries out boron removal treatment and boron regeneration on the lithium precipitation waste liquid, recovers the boron resource in the waste liquid, and prepares borate from the enriched boron solution; then the lithium precipitation waste liquid enters the nanofiltration membrane system, separates the sodium carbonate solution therein, and the remaining permeate enters the bipolar membrane electrodialysis system to obtain an acid solution and an alkali solution. The recovered boron in the process can be used to prepare boric acid or borate, and the sodium carbonate solution, the acid solution and the alkali solution can be applied to the lithium extraction process of salt lake brine, fully realizing the resource utilization and zero emission of the lithium precipitation waste liquid. The technical scheme can reduce the production cost of lithium carbonate prepared by lithium extraction from salt lake, reduce carbon dioxide emission, further reduce production cost, and has considerable economic benefits, and is suitable for industrial application.

[0033] The lithium ion concentration in the lithium precipitation waste liquid in the application is low, and it is not necessary to add water for dilution, and it is not easy to form solid precipitation on the surface of the nanofiltration membrane or the bipolar membrane, causing fouling phenomenon, so the process is relatively easy to implement. In some embodiments of the application, the lithium precipitation waste liquid is the waste liquid after lithium extraction or lithium adsorption of the lithium carbonate preparation process. In some embodiments of the application, the concentration of carbonate in the lithium precipitation waste liquid is 9.5-19 g / L, the concentration of hydroxide is 2.0-4.0 g / L, and the pH value of the lithium precipitation waste liquid is 9.5-13, which can be fully recovered and utilized by the method of the application. Preferably, the concentration of sodium ions in the lithium precipitation waste liquid is 40-90 g / L, the concentration of carbonate ions is 9.9-19 g / L, the concentration of boron ions is 100-500 mg / L, and the concentration of chloride ions is 40-120 g / L, and the recovery and utilization efficiency is higher by the method of the application.

[0034] In order to further improve the recovery efficiency of boron element, in some embodiments of the application, step S1 comprises: first adjusting the pH value of the lithium precipitation waste liquid to 9.5-10, and then carrying out boron removal treatment; the pH adjusting agent for adjusting the pH value includes but is not limited to any one or more of hydrochloric acid, nitric acid and carbon dioxide, and the pH adjusting agent is preferably carbon dioxide, which can increase the content of carbonate in the lithium precipitation waste liquid and be separated and utilized in the subsequent steps.

[0035] The specific method of the above boron removal treatment can be selected in the prior art, and the application does not limit it. In some embodiments of the application, a resin boron removal system is used for boron removal treatment, and the boron removal efficiency is high. The resin boron removal system includes an adsorption tower containing a boron adsorbent, a matching tank and the like. Exemplarily, the boron adsorbent includes but is not limited to boron selective chelating resin, ion exchange resin, activated carbon, metal oxide and composite, biological adsorbent and the like. The specific process parameters of the resin boron removal system can be determined by those skilled in the art according to the prior art, which will not be introduced here.

[0036] The researchers of the present application found in the experiment that the boron ions in the waste liquid would enter the concentrated water mainly containing sodium carbonate during the nanofiltration process, and the excessive concentration of boron ions would reduce the purity of lithium carbonate in the subsequent use process. In some preferred embodiments of the present application, the concentration of boron ions in the lithium precipitation waste liquid is 100-170 mg / L, which not only fully absorbs the boron ions, but also does not adversely affect the subsequent process. Preferably, the concentration of boron ions in the boron removal waste liquid is 0-5 mg / L, the recovery efficiency is higher, and the application effect of the concentrated water obtained by subsequent separation is better.

[0037] In some embodiments of the present application, the concentration of sodium ions in the boron removal waste liquid is 40-60 g / L, the concentration of boron ions is 0-5 mg / L, the concentration of carbonate ions is 9.9-19 g / L, and the concentration of chloride ions is 20-100 g / L.

[0038] In the above nanofiltration membrane system, the nanofiltration membrane has a special pore size structure and separation performance, which can effectively retain ions with a valence of two or more, while blocking other types of particulate matter. During the entire filtration process, water molecules and monovalent ions can smoothly pass through the nanofiltration membrane, thereby achieving efficient separation of sodium carbonate and other components in the lithium extraction waste liquid. In actual application, the nanofiltration membrane can be reasonably selected according to existing technology. For example, a commercial alkali-resistant high-pressure membrane, which can maintain good stability and separation performance when dealing with lithium extraction waste liquid containing alkaline substances. Preferably, when the pore size of the nanofiltration membrane is in the range of 1-2 nm, the separation efficiency of the target substance is relatively high. The specific operation method and other process parameters of nanofiltration can refer to existing technology, which is not limited in the present application.

[0039] In some embodiments of the present application, the concentration of boron ions in the boron-rich liquid after resin regeneration is 100-600 mg / L; preferably, the pH of the boron ion solution is adjusted to about 10, and the boron-rich liquid is used to configure borax (Na2B4O7) in the lithium precipitation system. In the concentrated water of the nanofiltration system, the concentration of carbonate ions is 20-60 g / L, the concentration of sodium ions is 30-80 g / L, and the concentration of chloride ions is 5-50 g / L; preferably, the concentration of boron ions in the concentrated water is 0-10 mg / L. Preferably, the concentrated water is used to configure a sodium carbonate solution in the lithium precipitation system. The recovery of sodium carbonate in unit volume of lithium precipitation wastewater is 22.7-43.8 kg / m 3 , which can reduce the sodium carbonate consumption of 0.3-1.0 tons in the lithium carbonate preparation process, reduce the carbon dioxide emission of 9.39-18.22 kg / m 3 in unit volume of lithium precipitation waste liquid, and realize the comprehensive utilization of waste liquid.

[0040] In some embodiments of the present application, the concentration of carbonate ions in the nanofiltration system permeate is 0.5-5.4 g / L, the concentration of sodium ions is 40-60 g / L, and the concentration of chloride ions is 20-50 g / L.

[0041] In step S3, the bipolar membrane used in the bipolar membrane electrodialysis system is generally a bipolar membrane composed of a positive membrane, a catalytic layer and a negative membrane. Under the action of a direct current electric field, the bipolar membrane can dissociate water and obtain hydrogen ions and hydroxide ions on both sides of the bipolar membrane, and the adjacent compartments can enrich acidic solution and basic solution, respectively. The bipolar membrane can be selected in the prior art, such as a commercial special ion membrane system. Those skilled in the art can select the corresponding process parameters of the bipolar membrane electrodialysis system according to the prior art, and the present application does not have special requirements.

[0042] In order to improve the separation effect of the bipolar membrane electrodialysis system, in some embodiments of the present application, the pH value of the permeate is adjusted to 3-4.

[0043] In some embodiments of the present application, 0.40-0.55 mol / L of lithium carbonate can be prepared from each cubic meter of permeate. 3 The acid solution has a concentration of 1.9-2.5 mol / L; preferably, the acid solution is used in the system process before the adsorption method is used to extract lithium from salt lake brine, for example, in the refining process of the lithium-containing solution.

[0044] In some embodiments of the present application, 0.40-0.55 mol / L of lithium carbonate can be prepared from each cubic meter of permeate. 3 The alkali solution has a concentration of 1.9-2.5 mol / L; preferably, the alkali solution is used in the system process before the adsorption method is used to extract lithium from salt lake brine, for example, in the refining process of the lithium-containing solution.

[0045] In some typical embodiments of the present application, the treatment of the lithium precipitation waste liquid utilizes a method as shown in Figure 1 After adjusting the pH value of the lithium precipitation waste liquid to 9.5-10, the lithium precipitation waste liquid is subjected to boron removal treatment to obtain boron removal waste liquid and separated boron-containing concentrated liquid, wherein the boron-containing compound is used to prepare boric acid or borax; the boron removal waste liquid is separated by a nanofiltration system to obtain concentrated water and permeate, wherein the concentrated water is used to prepare sodium carbonate solution; the permeate is adjusted in pH value and then enters the bipolar membrane electrodialysis system to be converted into acid, alkali and brine, wherein the brine is subjected to treatment by a reverse osmosis system and then enters the bipolar membrane electrodialysis system again.

[0046] According to another typical embodiment of the present application, a device for implementing the utilization method of the lithium precipitation waste liquid is provided, which comprises: a boron removal resin system configured to subject the lithium precipitation waste liquid to boron removal treatment to obtain boron removal waste liquid; a nanofiltration membrane system configured to separate the boron removal waste liquid into concentrated water and permeate; and a bipolar membrane electrodialysis system configured to convert the permeate into acid and alkali.

[0047] The aforementioned device first treats the lithium precipitation wastewater to remove boron. Using specific boron removal technology and adsorption materials, boron is efficiently recovered from the wastewater. The recovered boron is then fed into a nanofiltration membrane system to separate the sodium carbonate solution. The remaining permeate enters a bipolar membrane electrodialysis system to obtain acid and alkali solutions. The recovered boron can be used to prepare borax, and the recovered sodium carbonate solution, along with the prepared acid and alkali solutions, can be applied to the lithium extraction process from salt lake brine, fully realizing the resource utilization and zero discharge of lithium precipitation wastewater. This device recovers and reuses useful components from lithium precipitation wastewater, reducing the production cost of lithium carbonate production from salt lakes, reducing carbon dioxide emissions, and further lowering production costs. It offers considerable economic benefits and is suitable for industrial applications.

[0048] The beneficial effects that this application can achieve will be further illustrated below with reference to embodiments and comparative examples.

[0049] Example 1

[0050] This embodiment provides a method for the efficient utilization of waste liquid during lithium extraction from salt lake brine, such as... Figure 1 As shown, proceed as follows:

[0051] 1. The raw material to be treated is the lithium precipitation waste liquid after lithium extraction, with a lithium ion concentration of 10 ppm, a sodium ion concentration of 43.58 g / L, a carbonate concentration of 10.14 g / L, a boron ion concentration of 163.79 mg / L, a chloride ion concentration of 49.15 g / L, and a pH of 12.86; 31% hydrochloric acid is added to adjust the pH to 9.5. The lithium precipitation waste liquid is fed into a resin boron removal system for boron removal treatment. The resin boron removal system includes an adsorption tower containing boron adsorbent and a matching tank. The boron adsorbent is D870B type ion exchange resin. After treatment by the resin boron removal system, boron-removed waste liquid and resin-regenerated boron-enriched liquid are obtained. The boron ion concentration in the resin-regenerated boron-enriched liquid is 399 mg / L, which is used to prepare borax with a boron ion recovery rate of 93%. In the boron-removed waste liquid, the sodium ion concentration is 41.12 g / L, the boron ion concentration is 1.95 mg / L, the carbonate ion concentration is 10.63 g / L, and the chloride ion concentration is 42 g / L.

[0052] 2. The boron-removed wastewater is pumped into a nanofiltration membrane system. The nanofiltration membrane is a commercially available membrane (2 nm pore size, domestic GH-4040-F34 type membrane), yielding nanofiltration concentrate and nanofiltration permeate. The nanofiltration concentrate has a carbonate concentration of 25.93 g / L and a boron ion concentration of 5.29 mg / L. This portion of the solution is used for preparing the sodium carbonate solution in the lithium precipitation system, reducing carbon dioxide emissions per unit volume of lithium precipitation wastewater by 14.9 kg / m³. 3 The concentration of carbonate ions in the nanofiltration permeate was 3.50 g / L, the concentration of sodium ions was 45.61 g / L, and the concentration of chloride ions was 40.52 g / L.

[0053] 3. The nanofiltration permeate is pumped into a bipolar membrane electrodialysis system after adjusting the pH value to 10.5-3.5, and 0.5m 3 / m 3 of 2mol / L hydrochloric acid and 0.5m 3 / m 3 of 2mol / L sodium hydroxide solution with a concentration of 2mol / L are generated per unit volume of nanofiltration permeate, which is returned to the system process before the lithium extraction from salt lake brine by the adsorption method.

[0054] Example 2

[0055] 1. The raw material to be treated is lithium precipitation waste liquid after lithium extraction, with a lithium ion concentration of 9.5ppm, a sodium ion concentration of 44g / L, a carbonate ion concentration of 11.98g / L, a boron ion concentration of 162.58mg / L, a chloride ion concentration of 50g / L, and a pH of 12.85; carbon dioxide is introduced to adjust the pH to 10. The lithium precipitation waste liquid is introduced into a resin boron removal system for boron removal treatment, and the resin boron removal system includes an adsorption tower containing a boron adsorbent and a matching tank. The boron adsorbent is the same as that in Example 1. After treatment by the resin boron removal system, boron removal waste liquid and resin regeneration boron-rich liquid are obtained. The boron ion concentration of the resin regeneration boron-rich liquid is 366mg / L, which is used to prepare borax. The boron removal waste liquid has a sodium ion concentration of 44.52g / L, a boron ion concentration of 2.2mg / L, a carbonate ion concentration of 9.93g / L, and a chloride ion concentration of 43.9g / L.

[0056] 2. The above boron removal waste liquid is pumped into a nanofiltration membrane system. The nanofiltration membrane is a commercialized membrane and is the same as that in Example 1. The nanofiltration concentrate recovers a carbonate ion concentration of 33.42g / L and a boron ion concentration of 8.38mg / L. This part of the solution is used to prepare a sodium carbonate solution for the lithium precipitation system, which reduces the carbon dioxide emission of 16.03kg / m 3 for unit volume of lithium precipitation waste liquid. In the nanofiltration permeate, the carbonate ion concentration is 1.8g / L, the sodium ion concentration is 52.3g / L, and the chloride ion concentration is 48g / L.

[0057] 3. The nanofiltration permeate is pumped into a bipolar membrane electrodialysis system after adjusting the pH value to 3, and 0.45m 3 / m 3 of 2.2mol / L hydrochloric acid solution and 0.45m 3 / m 3 of 2.2mol / L sodium hydroxide solution are generated per unit volume of nanofiltration permeate waste liquid, which is returned to the system process before the lithium extraction from salt lake brine by the adsorption method.

[0058] Example 3

[0059] 1. The raw material to be treated is lithium extraction waste liquid with lithium ion concentration of 9.3 ppm, sodium ion concentration of 43.19 g / L, carbonate ion concentration of 12.53 g / L, boron ion concentration of 160.52 mg / L, chloride ion concentration of 49.39 g / L, and pH of 12.88. 31% hydrochloric acid is added to adjust the pH to 10, and the lithium extraction waste liquid is introduced into a resin boron removal system for boron removal treatment. The resin boron removal system comprises an adsorption tower containing boron adsorbent and a matching tank. The boron adsorbent is the same as that in Example 1. After treatment by the resin boron removal system, boron removal waste liquid and resin regeneration boron-rich liquid are obtained. The boron ion concentration of the resin regeneration boron-rich liquid is 357 mg / L, which is used to prepare borax. The boron removal waste liquid has a sodium ion concentration of 42.87 g / L, a boron ion concentration of 0.87 mg / L, a carbonate ion concentration of 11.75 g / L, and a chloride ion concentration of 47.97 g / L.

[0060] 2. The above boron removal waste liquid is pumped into a nanofiltration membrane system. The nanofiltration membrane is the same as that in Example 1. The nanofiltration concentrated water has a carbonate ion concentration of 37.35 g / L and a boron ion concentration of 8.68 mg / L. This part of the solution is used to prepare sodium carbonate solution for the lithium precipitation system, reducing the carbon dioxide emission of 18.2 kg / m 3 ; The nanofiltration permeate has a carbonate ion concentration of 1.32 g / L, a sodium ion concentration of 50.20 g / L, and a chloride ion concentration of 45.30 g / L.

[0061] 3. After adjusting the pH of the nanofiltration permeate to 3, it is pumped into a bipolar membrane electrodialysis system. At the same time, 0.45 m 3 / m 3 of 2.1 mol / L hydrochloric acid solution and 0.45 m 3 / m 3 of 2.1 mol / L sodium hydroxide solution are generated per unit volume of nanofiltration permeate, which are returned to the adsorption method salt lake brine lithium extraction system.

[0062] Example 4

[0063] The difference from Example 1 is that after boron removal treatment, the boron ion concentration in the boron removal waste liquid is 5 mg / L.

[0064] After treatment by the same process as Example 1, the boron ion concentration of the resin regeneration boron-rich liquid is 327 mg / L; the nanofiltration concentrated water has a carbonate ion concentration of 41.71 g / L and a boron ion concentration of 11.5 mg / L.

[0065] Example 5

[0066] The difference from Example 1 is that after boron removal treatment, the boron ion concentration in the boron removal waste liquid is 10 mg / L.

[0067] After the same process as example 1, the boron ion concentration of the resin regeneration boron-rich liquid is 358 mg / L; the carbon dioxide concentration of the nanofiltration concentrated water is 42.57 g / L, and the boron ion concentration is 15.83 mg / L.

[0068] Comparative example 1

[0069] The B2O3 content in the lithium extraction tail brine of salt lake is 2.937 g / L, the lithium content is 36 mg / L, the sodium content is 1.42 g / L, the sulfate content is 9.508 g / L, the chlorine content is 136.841 g / L, and the pH is 6-7. Sodium hydroxide and sodium carbonate are added to adjust the pH to 10.8; pumped into the membrane separation device, carbon dioxide is supplied, the internal temperature of the membrane separation device is 60-90℃, the clear liquid enters the constant temperature crystallization tank at 0-25℃, and the borax mother liquor (boron content is greater than 80 g / L) is crystallized and separated out by stirring and cooling; after centrifugation, borax product is obtained, and the yield of boron ions is 90%.

[0070] Comparative example 2

[0071] The difference from example 1 is that step 1 is not performed, and the lithium precipitation waste liquid after lithium extraction (the same as example 1) is directly pumped into the nanofiltration membrane system. The carbon dioxide concentration of the nanofiltration concentrated water is 35.6 g / L, and the boron ion concentration is about 50 mg / L. This part of the solution is used for preparing the sodium carbonate solution in the lithium precipitation system. The concentrated water with a carbon dioxide concentration of 30 g / L is heated to 60℃, and then a sodium carbonate solution with a concentration of 375 g / L is prepared. The solution is continuously used in the lithium precipitation process, and the carbon dioxide emission of unit volume of lithium precipitation waste liquid is reduced by 14.8 kg / m 3 .

[0072] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects: first, the lithium precipitation waste liquid is treated to remove boron, and the boron is recovered, then the lithium precipitation waste liquid is introduced into the nanofiltration membrane system, the sodium carbonate solution is separated out, and the remaining permeate is introduced into the bipolar membrane electrodialysis system to obtain an acid solution and an alkali solution. The recovered boron in the process can be used to prepare boric acid, and the sodium carbonate solution, the acid solution and the alkali solution can be applied to the lithium extraction process of salt lake brine, fully realizing the resource utilization and zero emission of the lithium precipitation waste liquid. The technical scheme can reduce the production cost of lithium carbonate prepared by lithium extraction from salt lake, reduce the carbon dioxide emission, further reduce the production cost, and has considerable economic benefits, and is suitable for industrial application.

[0073] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for utilizing lithium precipitation waste liquid, characterized in that, include: Step S1: The lithium precipitation waste liquid is subjected to boron removal treatment to obtain boron removal waste liquid and resin regeneration boron enrichment liquid. The lithium precipitation waste liquid contains sodium ions, carbonate ions, chloride ions and / or sulfate ions and boron ions, and the concentration of lithium ions in the lithium precipitation waste liquid is less than 10.5 ppm. Step S2 involves introducing the boron removal waste liquid into a nanofiltration membrane system for separation to obtain concentrated water and permeate; Step S3: After adjusting the pH value of the permeate, pump it into the bipolar membrane electrodialysis system to obtain acid solution and alkaline solution.

2. The method for utilizing lithium precipitation waste liquid according to claim 1, characterized in that, The lithium precipitation waste liquid is the waste liquid after lithium extraction or lithium adsorption of the lithium precipitation mother liquor during the lithium carbonate preparation process. Preferably, the lithium precipitation waste liquid has a carbonate concentration of 9.5-19 g / L and a hydroxide concentration of 2.0-4.0 g / L. Preferably, the pH value of the lithium precipitation waste liquid is 9.5-13.

3. The method for utilizing lithium precipitation waste liquid according to claim 2, characterized in that, Step S1 includes: first adjusting the pH value of the lithium precipitation waste liquid to 9.5-10, and then performing boron removal treatment; Preferably, the pH adjuster for adjusting the pH value is any one or more of hydrochloric acid, nitric acid, and carbon dioxide; Preferably, in the lithium precipitation waste liquid, the sodium ion concentration is 40-90 g / L, the carbonate ion concentration is 9.9-19 g / L, the boron ion concentration is 100-500 mg / L, and the chloride ion concentration is 40-120 g / L.

4. The method for utilizing lithium precipitation waste liquid according to claim 1, characterized in that, The boron removal process is performed using a resin boron removal system. Preferably, the boron ion concentration in the boron removal wastewater is 0-5 mg / L; Preferably, the sodium ion concentration in the boron removal waste liquid is 40-60 g / L, the carbonate ion concentration is 9.9-19 g / L, and the chloride ion concentration is 20-100 g / L.

5. The method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 4, characterized in that, The boron ion concentration in the regenerated boron-containing enriched solution is 100-600 mg / L; preferably, the pH of the regenerated boron-containing enriched solution is adjusted to 10 for use in the lithium precipitation system to prepare borax.

6. The method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 4, characterized in that, The concentrated solution has a carbonate concentration of 20-60 g / L, a sodium ion concentration of 30-80 g / L, and a chloride ion concentration of 5-30 g / L; preferably, the concentrated solution has a boron ion concentration of 0-10 mg / L; preferably, the concentrated solution is used to prepare a sodium carbonate solution in a lithium precipitation system. And / or, in the permeate, the concentration of carbonate is 0.5-5.4 g / L, the concentration of sodium ions is 40-60 g / L, and the concentration of chloride ions is 20-50 g / L.

7. The method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 4, characterized in that, The nanofiltration membrane of the nanofiltration membrane system is an alkali-resistant high-pressure membrane, preferably with a pore size of 1-2 nm.

8. The method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 4, characterized in that, In step S3, the pH value of the permeate is adjusted to 3-4.

9. The method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 4, characterized in that, In step S3, 0.40-0.55 m³ of permeate is prepared per cubic meter of the permeate. 3 The acid solution has a concentration of 1.9-2.5 mol / L; preferably, the acid solution is used in the pre-process of lithium extraction from salt lake brine using the adsorption method. And / or, in step S3, 0.40-0.55 m³ of the permeate is prepared per cubic meter. 3 The alkaline solution has a concentration of 1.9-2.5 mol / L; preferably, the alkaline solution is used in the pre-process of lithium extraction from salt lake brine using the adsorption method.

10. An apparatus for implementing the method for utilizing lithium precipitation waste liquid according to any one of claims 1 to 9, comprising: The boron removal resin system is configured to treat lithium precipitation waste liquid to remove boron, resulting in boron-removed waste liquid. A nanofiltration membrane system is configured to separate the boron removal waste liquid into concentrated water and permeate; and The bipolar membrane electrodialysis system is configured to convert the permeate into acid and alkali solutions.

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