Low-concentration lithium and boron comprehensive extraction process based on gravel type underground brine

Abstract

The invention relates to the field of comprehensive recycling of underground brine, and particularly discloses a low-concentration lithium and boron comprehensive extraction process based on gravel-type underground brine, which comprises the following steps: S1, evaporating and concentrating the gravel-type underground brine to obtain concentrated brine; s2, the concentrated brine is subjected to dynamic adsorption through an adsorption column filled with a lithium adsorbent, lithium extraction tail liquid is obtained, then the adsorbent is desorbed, and lithium desorption liquid is obtained; s3, carrying out nanofiltration reverse osmosis on the lithium desorption solution to obtain a lithium enrichment solution; s4, the lithium extraction tail liquid is subjected to dynamic adsorption through an adsorption column filled with a boron adsorbent, boron extraction tail liquid is obtained, then the adsorbent is desorbed, and boron desorption liquid is obtained; and S5, evaporating and concentrating the boron desorption solution, and cooling to separate out a boric acid product.

Description

Technical Field

[0001] The invention relates to the field of comprehensive recovery and utilization of underground brine, and specifically to a low-concentration lithium and boron comprehensive extraction process based on gravel-type underground brine. Background Art

[0002] Since 2008, new gravel-type deep brine has been discovered in Dalangtan-Heibei Depression, Chahansilatu Depression, Kunteyi Depression and Mahai Depression in the western part of Qaidam Basin. It has the characteristics of wide distribution, large scale, strong water-richness and easy exploitation. Existing research shows that the gravel-type deep brine in the western Qaidam Basin K + The content is 1.64~3.76g / L, Na + The content is 93.09~112.77g / L, Ca 2+ The content is 3.77~6.19g / L, Mg 2+ The content is 2.26~10.82g / L, Cl - Content is 169.05~188.27g / L, SO4 2- The content is 1.33-2.51 g / L, and the mineralization is 276.9-311.4 g / L (Li Hongpu, Hou Xianhua, Zheng Mianping, et al. Discussion on the mineralization model and prospecting direction of the Pleistocene gravel-type deep brine potash deposit in the western Qaidam Basin [J]. Lake Science, 2022, 34(03): 1043-1054.), and the mineral resources are rich.

[0003] The current development process of salt lake brine is mostly focused on high-concentration brine resources. There is still a lack of efficient extraction methods for low-concentration underground brine, especially gravel-type brine. Due to the low concentration of valuable elements such as lithium and boron, the large number of impurity ions, and the extremely high magnesium-lithium ratio, the lithium-boron extraction efficiency is low. How to improve the extraction efficiency through process optimization while minimizing energy consumption and costs is still a difficult point in the development of technology in this field. The current industry generally has the following problems: the extraction cost of low-concentration brine is high and the economic benefits are low; most of the existing processes are aimed at the extraction of a single element and fail to effectively and comprehensively recover multiple valuable elements; the energy consumption problem in the process needs to be optimized. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a low-concentration lithium and boron comprehensive extraction process based on gravel-type underground brine, so as to at least achieve the effects of process optimization, high resource utilization and green environmental protection.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A low-concentration lithium and boron comprehensive extraction process based on gravel-type underground brine, characterized by comprising the following steps:

[0007] S1: Evaporating and concentrating gravel-type underground brine to obtain concentrated brine;

[0008] S2: dynamically adsorbing the concentrated brine through an adsorption column filled with a lithium adsorbent to obtain a lithium extraction tail liquid, and then desorbing the adsorbent to obtain a lithium desorption liquid;

[0009] S3: subjecting the lithium desorption solution to nanofiltration reverse osmosis to obtain a lithium-enriched solution;

[0010] S4: dynamically adsorbing the lithium extraction tail liquid through an adsorption column filled with a boron adsorbent to obtain a boron extraction tail liquid, and then desorbing the adsorbent to obtain a boron desorption liquid;

[0011] S5: evaporating and concentrating the boron desorption liquid, and cooling the liquid to precipitate the boric acid product.

[0012] Preferably, the gravel-type underground brine is gravel-type deep brine in the Qaidam Basin.

[0013] Furthermore, in step S1, the evaporation concentration is evaporation until sodium salt is precipitated.

[0014] Furthermore, in step S2, the lithium adsorbent includes: aluminum-based, manganese-based and titanium-based adsorbents.

[0015] Furthermore, in step S2, the desorption method is washing with water.

[0016] Furthermore, in step S3, the nanofiltration reverse osmosis specifically uses a nanofiltration membrane and a reverse osmosis membrane to separate and concentrate the lithium desorption solution.

[0017] Furthermore, in step S4, the boron adsorbent includes: chelate adsorption or ion exchange resin.

[0018] Furthermore, in step S5, the cooling is to reduce the temperature to -20 to 5°C.

[0019] It is worth noting that gravel-type underground brine is widely distributed and has large reserves. However, due to the low lithium-boron content of gravel-type underground brine, current research focuses on potassium extraction. If the lithium-boron extraction step is placed at a later stage, the yield of lithium-boron will be reduced. The present invention directly uses adsorption method to extract lithium-boron after enriching lithium-boron to a certain concentration before potassium salt is precipitated, that is, lithium-boron extraction is placed in advance, thereby improving the yield and selectivity of lithium-boron.

[0020] The beneficial effects of the present invention are:

[0021] 1. Process optimization: Through the efficient combination of evaporation, adsorption, membrane concentration and other steps, not only the extraction efficiency of lithium and boron is improved, but also the energy consumption of the extraction process is greatly reduced.

[0022] 2. Comprehensive utilization of resources: The process realizes the step-by-step extraction and enrichment of lithium and boron through adsorption, which greatly improves the comprehensive recovery rate of resources and reduces resource waste.

[0023] 3. Green and environmentally friendly: It optimizes the energy consumption of evaporation and membrane separation steps, reduces the risk of environmental pollution, and meets the requirements of modern environmental protection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a simplified process flow diagram of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0026] The underground brine used in the following examples is gravel-type underground brine from the Huangshi area in the western part of the Qaidam Basin. The chemical analysis of the main elements is shown in Table 1 (Note: * is mg / L), in which the main valuable elements are lithium and boron.

[0027] Table 1 Chemical analysis of main elements in gravel-type underground brine (g / L)

[0028] Potassium* sodium calcium magnesium 148.55 41.74 9.05 1.86 Sulfate boron* lithium* chlorine 0.85 61.30 31.20 76.21

[0029] The lithium adsorbent used is an aluminum-based adsorbent: it is homemade and its main component is Li 0.4 Mn 0.3 Al 0.3 O 2.9 The preparation method is to mix aluminum sulfate, lithium sulfate and manganese sulfate, and obtain the mixture through the steps of coprecipitation, aging, solid-liquid separation, washing and calcination.

[0030] The boron adsorbent used is a boron chelate adsorption resin with polystyrene as the skeleton: it is homemade, and the preparation method is to mix polystyrene, a cross-linking agent, a functional monomer, an initiator, etc. in a certain proportion, polymerize to form a polystyrene copolymer, and then introduce a boron chelate group for functionalization reaction to prepare it.

[0031] The nanofiltration membrane used was purchased from Nanjing Membrane Material Industry Technology Research Institute Co., Ltd., model NF-1812.

[0032] The reverse osmosis membrane used was purchased from Nanjing Membrane Material Industry Technology Research Institute Co., Ltd., model RO-1812.

[0033] Example 1

[0034] The underground brine was concentrated by evaporation until sodium salt was precipitated, and the lithium concentration was detected to be increased to 146.6 mg / L and the boron concentration was increased to 275.2 mg / L. Passing through the adsorption column (the adsorbent is a lithium adsorbent) at a flow rate of 5 Bv / H, the adsorption amount of the lithium adsorbent is 3.11 mg / g. 1.0 Bv of deionized water was used to elute and remove impurities at a flow rate of 15 Bv / H. After the elution was completed, 5.56 Bv of deionized water was used for analysis at a flow rate of 5 Bv / H to obtain 352 mg / L of lithium-rich analytical solution, and the lithium analysis rate was 97%. The lithium-rich analytical solution was removed from most of the impurity ions such as calcium, magnesium, potassium, and sodium through the "nanofiltration-reverse osmosis" operation (i.e., passing through a nanofiltration membrane and a reverse osmosis membrane), and the lithium concentration of the reverse osmosis solution was further enriched to 3-5 g / L. The reverse osmosis solution was used as a feed liquid for the subsequent preparation of lithium carbonate.

[0035] The boron concentration of the lithium extraction tail liquid is 268 mg / L. It is passed through an adsorption column (boron adsorbent) at a flow rate of 5 Bv / H to adsorb boron. When the adsorption amount reaches about 15 mg / g, it is stopped. It is analyzed with 6 Bv of 6% dilute hydrochloric acid at a flow rate of 2 Bv / H to obtain a boron-rich analysis liquid with a boron concentration of 1.7 g / L and a boron analysis rate of nearly 100%. It is evaporated and enriched to a boron concentration of about 10 g / L, and then frozen and cooled to 0-5°C to obtain boric acid, with a boron yield of up to 58%.

[0036] Example 2

[0037] The raw brine is concentrated by evaporation until sodium salt is precipitated, and the lithium concentration is increased to 146.6 mg / L and the boron concentration is increased to 275.2 mg / L. It passes through the adsorption column (the adsorbent is a lithium adsorbent) at a flow rate of 10 Bv / H, and the lithium adsorption amount is 3.54 mg / g. It is washed and removed with 0.5 Bv of deionized water at a flow rate of 10 Bv / H. After the elution is completed, 3.89 Bv of deionized water is used for thermal analysis at a flow rate of 10 Bv / H to obtain 368 mg / L of lithium-rich analytical solution with a lithium analysis rate of 62%. The lithium-rich analytical solution is removed by "nanofiltration-reverse osmosis" operation to remove most of the impurity ions such as calcium, magnesium, potassium, and sodium, and the lithium concentration of the reverse osmosis solution is further enriched to 3-5 g / L. The reverse osmosis liquid is used as a feed liquid for the subsequent preparation of lithium carbonate.

[0038] The boron concentration of the lithium extraction tail liquid is 261 mg / L. It is passed through an adsorption column (boron adsorbent) at a flow rate of 10 Bv / H to adsorb boron. When the adsorption amount reaches about 15 mg / g, it is stopped. It is analyzed with 3.33 Bv of 6% dilute hydrochloric acid at a flow rate of 6 Bv / H to obtain a boron-rich analysis liquid with a boron concentration of 2.1 g / L and a boron analysis rate of about 67%. It is evaporated and enriched to a boron concentration of about 10 g / L, and then frozen and cooled to -5 to 0°C to obtain boric acid, with a boron yield of up to 64%.

[0039] Example 3

[0040] The raw brine is concentrated by evaporation until sodium salt is precipitated, and the lithium concentration is increased to 146.6 mg / L and the boron concentration is increased to 275.2 mg / L. It passes through the adsorption column (the adsorbent is a lithium adsorbent) at a flow rate of 15 Bv / H, and the lithium adsorption amount is 3.9 mg / g. 1.11 Bv of deionized water is used for elution and impurity removal at a flow rate of 15 Bv / H. After elution, 5.56 Bv of deionized water is used for thermal analysis at a flow rate of 15 Bv / H to obtain 333 mg / L of lithium-rich analytical solution, and the lithium analysis rate is about 75%. The lithium-rich analytical solution is removed by "nanofiltration-reverse osmosis" operation to remove most of the impurity ions such as calcium, magnesium, potassium, and sodium, and the lithium concentration of the reverse osmosis solution is further enriched to 3-5 g / L. The reverse osmosis liquid is used as a feed liquid for the subsequent preparation of lithium carbonate.

[0041] The boron concentration of the lithium extraction tail liquid is 272 mg / L. It is passed through an adsorption column (boron adsorbent) at a flow rate of 10 Bv / H to adsorb boron. When the adsorption amount reaches about 12 mg / g, it is stopped. It is analyzed with 6 Bv of 6% dilute hydrochloric acid at a flow rate of 14 Bv / H to obtain a boron-rich analysis liquid with a boron concentration of 1.3 g / L and a boron analysis rate of about 92%. It is evaporated and enriched to a boron concentration of about 10 g / L, and then frozen and cooled to -10 to -5 ° C to obtain boric acid, with a boron yield of up to 73%.

[0042] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A low-concentration lithium and boron comprehensive extraction process based on gravel-type underground brine, characterized in that: The following steps are involved: S1: Evaporating and concentrating gravel-type underground brine to obtain concentrated brine; S2: dynamically adsorbing the concentrated brine through an adsorption column filled with a lithium adsorbent to obtain a lithium extraction tail liquid, and then desorbing the adsorbent to obtain a lithium desorption liquid; S3: subjecting the lithium desorption solution to nanofiltration reverse osmosis to obtain a lithium-enriched solution; S4: dynamically adsorbing the lithium extraction tail liquid through an adsorption column filled with a boron adsorbent to obtain a boron extraction tail liquid, and then desorbing the adsorbent to obtain a boron desorption liquid; S5: evaporating and concentrating the boron desorption liquid, and cooling the liquid to precipitate the boric acid product.

2. The process according to claim 1, characterized in that: In step S1, the evaporation concentration is to evaporate until sodium salt begins to precipitate.

3. The process according to claim 1, characterized in that: In step S2, the lithium adsorbent includes: aluminum-based, manganese-based and titanium-based adsorbents.

4. The process according to claim 1, characterized in that: In step S3, the nanofiltration reverse osmosis specifically uses a nanofiltration membrane and a reverse osmosis membrane to separate and concentrate the lithium desorption solution.

5. The process according to claim 1, characterized in that: In step S4, the boron adsorbent includes: chelate adsorption or ion exchange resin.

6. The process according to claim 1, characterized in that: In step S5, the cooling is to reduce the temperature to -20 to 5°C.

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