Chelate polymer for synchronously separating lithium, rubidium and cesium from lepidolite ore and preparation method of chelate polymer

Abstract

The invention belongs to the technical field of functional polymer adsorption materials, and particularly relates to a chelate polymer for synchronously separating lithium, rubidium and cesium from lepidolite ore and a preparation method of the chelate polymer. The polymer comprises a porous skeleton formed by crosslinking styrene-divinyl benzene, a 12-crown-4 derivative on an outer layer, a benzo-16-crown-5 amine monomer on a middle layer and sulfonated calix [6] arene on an inner layer which form a gradient distribution coordination layer, and carboxylic acid is used as an auxiliary coordination group. The polymer can realize efficient, synchronous and selective adsorption of Li < + >, Rb < + > and Cs < + > in an acid solution, has the advantages of high adsorption capacity, strong selectivity, good acid resistance, excellent cycle stability and the like, and is suitable for application scenes of lepidolite resource separation and purification, scattered metal recovery and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of functional polymer adsorption materials, and particularly relates to a chelate polymer for synchronously separating lithium, rubidium and cesium from lepidolite ore and a preparation method thereof. Background Art

[0002] As a typical lithium-containing silicate mineral, lepidolite is an important supplementary source of lithium resources. In the development of lepidolite resources, the Li + Leaching, accompanied by a large amount of Rb + 、Cs + Alkali metal coexisting ions, due to Rb + and Cs + It has important application value in high-end materials such as electronics and optics, and its simultaneous separation and recycling have become key links in improving resource utilization and realizing the coordinated development of multiple metals.

[0003] Currently, Li + The extraction methods mainly include precipitation, extraction and adsorption, among which ion exchange resins and functional polymers have been widely used in adsorption separation technology. However, most traditional resins are single functional ligands (such as sulfonic acid type, amino type), which are not very effective for Rb + 、Cs + The recognition of alkali metals with large radii is insufficient; and it is easily deactivated in a strong acid system, making it difficult to meet the continuous separation requirements under the high acid and high impurity conditions of lepidolite acid leaching.

[0004] While some studies have attempted to introduce crown ether and calixarene ligands into functional materials to enhance selectivity, existing technologies often employ a "co-grafting" approach, where multiple ligands are grafted onto the polymer backbone. This can lead to disordered functional group distribution and recognition interference between ligands, affecting adsorption capacity and selectivity. Furthermore, these materials suffer from poor structural stability, leading to significant performance degradation during recycling, limiting their industrial application.

[0005] Existing technology for simultaneous separation of Li in lepidolite acid leaching solution + , Rb + 、Cs + However, there are still problems such as insufficient selectivity, unstable structure, low adsorption capacity and limited material life in the process. It is urgent to develop a chelating functional material with hierarchical structure recognition ability, suitable for strong acid environment, and capable of efficiently and simultaneously adsorbing multiple alkali metal ions, so as to improve the synergistic recovery efficiency and economic value of rare metals. Summary of the Invention

[0006] The present invention aims to provide a chelating polymer for synchronously separating lithium, rubidium, and cesium from lepidolite ore and a preparation method thereof, which can achieve efficient, selective recognition and renewable separation of multiple alkali metal ions in an acidic environment, has excellent adsorption capacity, structural stability, and regeneration ability, and is suitable for the collaborative extraction and recovery of rare and dispersed metal resources in industrialization.

[0007] To achieve the above object, the present invention proposes the following technical solutions:

[0008] A chelating polymer for synchronously separating lithium, rubidium, and cesium from lepidolite ore, the chelating polymer comprising:

[0009] A cross-linked polymer backbone: a network structure formed by copolymerizing styrene and divinylbenzene, and the cross-linking degree of divinylbenzene is 8%-15%;

[0010] A gradient coordination layer, including: an outer layer: a 12-crown-4 derivative grafted on the surface of the backbone, and its structural formula is -O-(CH2CH2O)3-CH2-CH2-NH-CO-R1, where R1 is vinyl or acryloyloxy; an intermediate layer: a benzo-16-crown-5-amine monomer distributed in the pores of the backbone; an inner layer: sulfonated calix[6]arene bonded to the deep pores, and its lower edge contains 3-5 sulfonic acid groups (-SO3H);

[0011] An auxiliary coordination group: a carboxyl group (-COOH) formed by hydrolysis of acrylic acid or maleic anhydride connected in the backbone, and the content is 5wt%-12wt%.

[0012] Furthermore, the pore diameters of the cross-linked polymer backbone are distributed in a gradient, and the average pore diameters of the outer layer, middle layer, and inner layer are 100-200nm, 200-300nm, and 300-500nm, respectively.

[0013] Furthermore, the cavity diameter of the sulfonated calix[6]arene is The sulfonic acid group substitution degree is 4.

[0014] Furthermore, in the lepidolite leaching solution with pH = 2, the adsorption capacities for Li + , Rb + , Cs + are 30-35mg / g, 40-45mg / g, and 48-55mg / g, respectively.

[0015] Furthermore, after gradient elution with 0.1mol / L HNO3, 0.5mol / L HCl, and 3mol / L NH4NO3, the adsorption capacity attenuation rate after 50 cycles of use is less than 10%.

[0016] The present invention also provides a method for preparing a chelate polymer for synchronously separating lithium, rubidium and cesium from lepidolite ore, comprising the following steps:

[0017] a) Skeleton synthesis: styrene, divinylbenzene, a porogen and an initiator are mixed and subjected to suspension polymerization to prepare porous microspheres;

[0018] b) Outer layer grafting: The microspheres are immersed in a Li-containing + The template was in a 12-crown-4-acrylate solution and a free radical grafting reaction was initiated by 365 nm UV light for 2-4 hours;

[0019] c) Middle layer assembly: RAFT polymerization is used to polymerize benzo-16-crown-5-amine monomers layer by layer within the backbone pores;

[0020] d) Inner layer bonding: Sulfonated calix[6]arene is fixed in deep pores via a thiol-ene click reaction at a temperature of 50-70°C using AIBN as the initiator;

[0021] e) Carboxylation treatment: The obtained microspheres are placed in a mixture of acrylic acid and ammonium persulfate for hydrolysis to introduce carboxylic acid groups.

[0022] Furthermore, the porogen in step a) is a mixture of toluene and n-heptane in a volume ratio of 1:1-3:1, the stirring speed of the suspension polymerization reaction is 300-500 rpm, and the polymerization temperature is 75-85°C.

[0023] Furthermore, in step b), the Li + The template concentration is 0.5-1.0 mol / L, and the UV radiation intensity is 10-20 mW / cm 2 .

[0024] Furthermore, in step c), the concentration of the benzo-16-crown-5-amine monomer is 0.2-0.6 mol / L, and the RAFT chain transfer agent is cyanoisopropyl dithiobenzoate.

[0025] Furthermore, in step e), the hydrolysis reaction conditions are 60° C. for 6 hours, and the molar ratio of acrylic acid to ammonium persulfate is 10:1-20:1.

[0026] The beneficial effects of the present invention are:

[0027] (1) A gradient coordination layer with a spatial hierarchical recognition structure was constructed to effectively avoid the recognition interference between different ligands in traditional mixed grafting materials and achieve Li + , Rb + and Cs + The prepared chelating polymer can selectively adsorb Li+ , Rb + and Cs + have adsorption capacities of up to 35 mg / g, 44 mg / g, and 53 mg / g respectively, and the Li / K selectivity coefficient exceeds 5000, significantly superior to commercially available materials;

[0028] (2) The chelating polymer of the present invention still has high stability in a strong acid environment with pH = 1, and the retention rate of the adsorption capacity is greater than 98%, showing good acid resistance; [[ID=⑨]]

[0029] (3) After multiple rounds of adsorption - elution cycles, the attenuation rate of the adsorption capacity is less than 10%, and it has excellent structural stability and regenerability, suitable for continuous industrial operation;

[0030] (4) The overall preparation method has a mature process, mild reaction conditions, and controllable ligand introduction in each step, and is easy to be scaled up and applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of the results of the adsorption capacity comparison test of the present invention;

[0032] Figure 2 is a schematic diagram of the results of the acid stability comparison test of the present invention;

[0033] Figure 3 is a schematic diagram of the results of the adsorption cycle performance comparison test of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0034] The following examples further illustrate the present invention, but do not limit the scope of the present invention. Unless otherwise stated, the raw materials used in the examples are all commercially available qualified products.

[0035] Example 1:

[0036] Raw material ratio:

[0037] 80 g of styrene, 20 g of divinylbenzene (cross - linking degree 12%); initiator: 1.5 g of benzoyl peroxide; pore - forming agent: toluene and n - heptane are mixed in a volume ratio of 2:1, with a total volume of 120 mL; template grafting solution: 0.8 mol / L LiNO3 solution containing 40 mmol / L of 12 - crown - 4 - acrylate; middle - layer polymerization solution: 0.5 mol / L of benzo - 16 - crown - 5 - acrylate; chain transfer agent: 0.1 mol / L of cyanopropyl isopropyl dithiobenzoate, and the solvent is an ethanol / water mixture (volume ratio 3:1); click reaction solution: 3 mmol / L of sulfonated calix[6]arene, mercaptoacrylic acid (molar ratio 1.5:1, relative to calixarene), AIBN (1 wt% of the mass of mercaptoacrylic acid); carboxylation solution: an aqueous solution prepared by mixing acrylic acid and ammonium persulfate in a molar ratio of 15:1, and adjusting the pH to 6.5 - 7.0. Note: There is a misspelling in the original text where "⑨" should be "[[ID=⑨]]". It has been corrected in the translation for consistency.

[0038] Preparation method:

[0039] Skeleton synthesis: Styrene and divinylbenzene are mixed, a pore-forming agent and an initiator are added, and the mixture is emulsified until uniform; it is placed in an 85 °C water bath and reacted for 8 hours to form a porous spherical structure; the obtained product is subjected to Soxhlet extraction with ethanol for 24 hours to remove the pore-forming agent, and dried in a vacuum drying oven at 60 °C for 12 hours, and sieved to obtain skeleton microspheres with a particle size of 0.5 - 0.8 mm.

[0040] Outer layer functionalization: The skeleton microspheres are immersed in the template grafting solution, placed in a nitrogen atmosphere, irradiated with 365 nm ultraviolet light for 3 hours to complete the grafting reaction of 12-crown-4 groups, and then rinsed with 0.1 mol / L HCl to remove the Li + template.

[0041] Middle layer functionalization: The grafted microspheres are added to a solution of benzo-16-crown-5 acrylate (0.5 mol / L) and a chain transfer agent (0.1 mol / L) prepared in ethanol, and reacted at 50 °C for 6 hours under nitrogen protection to complete the RAFT polymerization reaction, so that the middle layer functional groups are fixed layer by layer in the skeleton pores.

[0042] Inner layer functionalization: The above-treated microspheres are transferred into an anhydrous ethanol solution containing sulfonated calix[6]arene (3 mmol / L), mercaptoacrylic acid (molar ratio 1.5:1), and AIBN (1 wt% of the mass of mercaptoacrylic acid), and reacted in a 60 °C water bath for 6 hours.

[0043] Carboxylation treatment: The functionalized microspheres are transferred into an aqueous solution prepared with a molar ratio of acrylic acid to ammonium persulfate of 15:1, the pH is adjusted to 6.5 - 7.0, and the mixture is stirred and reacted in a 60 °C water bath for 4 hours to complete the hydrolysis introduction of carboxyl functional groups and generate a -COOH structure.

[0044] To verify the influence of structural stratification and functional group configuration on performance, the following 3 groups of comparative samples are set up for comparative experiments. Except for the following differences, the remaining formulations and preparation methods in the comparative examples are the same as those in Example 1.

[0045] Comparative Example 1:

[0046] A mixed grafted chelating polymer without gradient structure; the difference lies in the way of introducing functional groups: instead of adopting a layered grafting strategy, 12-crown-4 acrylate, benzo-16-crown-5 acrylate and sulfonated calix[6]arene are mixed in a molar ratio of 1:1:1 and added at one time; anhydrous ethanol is used as the solvent, and the total ligand concentration is 0.2 mol / L; AIBN (the amount is 1wt% of the total mass of the ligand) is added under a nitrogen atmosphere, and the reaction is carried out at 60°C for 6 hours to achieve free radical co-grafting of functional groups; no template assistance is set, and no RAFT or click reaction control is adopted to form a copolymer material without structure layering.

[0047] Comparative Example 2:

[0048] The difference is that no carboxylation treatment is performed, and after the outer crown ether, the middle crown ether and the inner calixarene are functionalized, no carboxylation liquid is added.

[0049] Comparative Example 3:

[0050] Commercially available resin (DOWEX TM M4195).

[0051] In order to verify the effects of functional structure hierarchy, ligand distribution and auxiliary groups on the performance of the adsorption material, comparative tests on adsorption capacity, acid stability and multi-cycle performance were carried out using Example 1 and three comparative samples.

[0052] (1) Adsorption capacity and separation selectivity test

[0053] Using simulated lepidolite acid leaching solution (Li + 1000ppm, Rb + 800ppm, Cs + 500ppm; K + 2000ppm; Al3 + 300ppm) as the adsorption target, and the pH was adjusted to 2. The dynamic column method (filler 20mL, column height 30cm, flow rate 2BV / h) was used to test the adsorption capacity of each sample for the target ion and the Li / K separation selectivity, and the Li / K selectivity coefficient (K before and after adsorption) was calculated. + The experimental results are shown in the table below:

[0054] Table 1 Comparative data of adsorption capacity and selectivity

[0055] sample <![CDATA[Li + (mg / g)]]> <![CDATA[Rb + (mg / g)]]> <![CDATA[Cesium + (milligrams per gram)]]> Li / K selectivity coefficient Example 1 35.0 44.0 53.0 5200 Comparative Example 1 19.5 25.0 31.5 480 Comparative Example 2 26.0 30.5 37.0 980 Comparative Example 3 0.6 1.2 18.5 190

[0056] The gradient structure chelate polymer prepared in Example 1 was + , Rb + and Cs +in terms of adsorption capacity are much higher than those of the three comparative examples, especially for Li + exhibits outstanding adsorption ability. Its Li / K selectivity coefficient exceeds 5000, while that of Comparative Example 1 is only 480, indicating that non-stratified grafting leads to mutual interference between ligands and significant competition for adsorption sites, severely affecting the separation selectivity of the material. Although Comparative Example 2 has a gradient structure, due to the lack of carboxylic acid auxiliary groups and the absence of electrostatic complexation, the adsorption capacity decreases, especially for Li + with an obvious decline in adsorption ability, reflecting the important auxiliary role of the -COOH structure in the adsorption process. Comparative Example 3 is a commercially available single-functional ion exchange resin, which has almost no recognition ability for Li + and Rb + and mainly adsorbs Cs + , and its performance far from meets the requirements for synchronous separation.

[0057] (2) Acid stability test

[0058] To evaluate the stability of the materials in a strong acid environment, each sample was immersed in a sulfuric acid solution with pH = 1 for 72 hours, and samples were taken to test their adsorption abilities for Li + , Rb + and Cs + , and the capacity retention rate was calculated. The test results are as follows:

[0059] Table 2 Comparative data of acid stability

[0060]

[0061]

[0062] Example 1 maintained extremely high structural stability and adsorption ability under strong acid conditions. After 72 hours, the retention rates of the three ions were all approximately equal to 98%. The sulfonated calix[6]arene structure and carboxylic acid auxiliary groups used constituted a stable polar shell, which could effectively resist the damage of the acidic medium to the material structure. The structure of Comparative Example 2 was partially deconstructed under acidic conditions, and the adsorption capacity decreased significantly to less than half of the original performance. As a conventional commercially available resin, Comparative Example 3 had certain acid stability, but was significantly insufficient in terms of multi-functional recognition and synergistic fixation, and its adsorption capacity also decreased significantly, making it unsuitable for the working conditions of multi-metal synchronous adsorption in a strong acid environment.

[0063] (3) Recycling performance test

[0064] Under the same adsorption-elution conditions, multiple rounds of cyclic tests were conducted on each sample, and the test cycle was 50 times. The eluents used were 0.1 mol / L HNO3, 0.5 mol / L HCl, and a 3 mol / L NH4NO3 / ethanol mixture (volume ratio 1:1) in sequence. The change in the adsorption capacity of the material was tested every 10 rounds, and the results are as follows:

[0065] Table 3 Comparative data of adsorption cycle performance

[0066]

[0067] For the material of Example 1, after 10 rounds, 20 rounds, and 50 rounds of cycles, the retention rates of the adsorption capacities of Li + 、Rb + 、Cs + were greater than 89%, much higher than those of conventional chelating materials, showing excellent structural durability and complexing site stability.

[0068] For Comparative Example 1, the capacity had decreased to about 70% after the 20th round and dropped to about 40% after the 50th round; for Comparative Example 2, the attenuation was rapid, and the retention rate of Li + was only 57.2% after the 50th round; for the commercially available resin, the ion capacities of all decreased to a very low level after 50 rounds. The chelating polymer of the present invention still has a capacity retention rate greater than 89% under multiple acid elution conditions, meeting the industrial requirements for the material life in actual continuous working conditions.

[0069] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art of this industry should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A chelating polymer for synchronously separating lithium, rubidium, and cesium from lepidolite ore, characterized in that, The chelating polymer includes: A crosslinked polymer backbone: a network structure formed by copolymerizing styrene and divinylbenzene, and the crosslinking degree of divinylbenzene is 8%-15%; A gradient coordination layer, including: An outer layer: a 12-crown-4 derivative grafted on the surface of the backbone, and its structural formula is -O-(CH2CH2O)3-CH2-CH2-NH-CO-R1, where R1 is vinyl or acryloyloxy; An intermediate layer: a benzo-16-crown-5-amine monomer distributed in the pores of the backbone; An inner layer: sulfonated calix[6]arene bonded to the deep pores, and its lower edge contains 3-5 sulfonic acid groups (-SO3H); An auxiliary coordination group: a carboxyl group (-COOH) formed by hydrolysis of acrylic acid or maleic anhydride connected in the backbone, and the content is 5wt%-12wt%.

2. The chelating polymer according to claim 1, wherein The pore size of the crosslinked polymer backbone is distributed in a gradient, and the average pore sizes of the outer layer, middle layer, and inner layer are 100-200nm, 200-300nm, and 300-500nm respectively.

3. The chelating polymer according to claim 1 or 2, characterized in that, The cavity diameter of the sulfonated calix[6]arene is and the degree of sulfonic acid group substitution is 4.

4. The chelating polymer according to claim 1, wherein The chelating polymer has adsorption capacities for Li, Rb, and Cs in the leaching solution of lepidolite at pH = 2 of 30 - 35 mg / g, 40 - 45 mg / g, and 48 - 55 mg / g, respectively. + , Rb + , Cs + ​ 5. The chelating polymer according to claim 1, wherein After the chelating polymer is eluted with 0.1mol / L HNO3, 0.5mol / L HCl, and 3mol / L NH4NO3 in a gradient, the adsorption capacity decay rate after 50 cycles of use is less than 10%.

6. A method for preparing a chelating polymer for synchronously separating lithium, rubidium, and cesium from lepidolite ore as described in claim 1, characterized in that, It includes the following steps: a) Backbone synthesis: Mix styrene, divinylbenzene, a pore-forming agent, and an initiator, and perform suspension polymerization to obtain porous microspheres; b) Outer grafting: Immerse the microspheres in a 12-crown-4-acrylate solution containing Li + template, and initiate a free radical grafting reaction with 365 nm ultraviolet light for 2 - 4 hours; c) Intermediate layer assembly: Use RAFT polymerization reaction to polymerize benzo-16-crown-5-amine monomers layer by layer in the pores of the backbone; d) Inner layer bonding: Fix sulfonated calix[6]arene in the deep pores through a thiol-ene click reaction, the reaction temperature is 50-70°C, and the initiator is AIBN; e) Carboxylation treatment: Place the obtained microspheres in a mixed solution of acrylic acid and ammonium persulfate for hydrolysis to introduce carboxyl groups.

7. The method according to claim 6, wherein In step a), the pore-forming agent is a mixture of toluene and n-heptane, and the volume ratio is 1:1-3:

1. The stirring speed of the suspension polymerization reaction is 300-500rpm, and the polymerization temperature is 75-85°C.

8. The method according to claim 6, wherein In step b), the Li + template concentration is 0.5 - 1.0 mol / L, and the ultraviolet radiation intensity is 10 - 20 mW / cm 2 .

9. The method according to claim 6, characterized in that, In step c), the concentration of the benzo-16-crown-5-amine monomer is 0.2-0.6mol / L, and the RAFT chain transfer agent is cyanopropyl isopropyl dithiobenzoate.

10. The method according to claim 6, wherein In step e), the hydrolysis reaction conditions are to react at 60°C for 6 hours, and the molar ratio of acrylic acid to ammonium persulfate is 10:1-20:1.

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