A fluorinated cyclodextrin macromolecular adsorbent, a preparation method and application thereof

Abstract

The application provides a fluorinated cyclodextrin macromolecular adsorbent and a preparation method and application thereof, and belongs to the technical field of lithium ion adsorbents, and aims to solve the technical problems of poor lithium ion adsorption effect and low selectivity of existing lithium adsorbents. The preparation steps of the application comprise the following steps: firstly, dissolving beta-cyclodextrin in an organic solvent and reacting with 2-bromoisobutyryl bromide to obtain an intermediate product bromoisobutyryl beta-cyclodextrin; and then, performing a polymerization reaction on the bromoisobutyryl beta-cyclodextrin with a fluorine-containing monomer, copper bromide, N,N,N',N",N"-pentamethyldiethylenetriamine and tin (II) isooctoate to obtain a beta-cyclodextrin adsorption material with a surface grafted fluorine-containing polymer chain. The preparation method has the advantages of simple process and mild reaction conditions. The adsorption material has a high lithium ion adsorption capacity, which can reach 43.5 mg / g, and can efficiently and selectively recover lithium ions from a complex solution containing competitive ions such as sodium, potassium, magnesium, calcium and cobalt.

Description

Technical Field

[0001] This invention relates to the field of lithium adsorbent technology, and in particular to a fluorinated cyclodextrin polymeric adsorbent, its preparation method, and its application. Background Technology

[0002] Lithium, the lightest metallic element in nature, possesses unique physicochemical properties and is a core material for new energy batteries and energy storage systems. Driven by the continued growth in demand for electric vehicles and renewable energy, the demand for lithium-ion batteries is projected to surge 8 to 10 times by 2050, consuming 74% to 248% of global lithium reserves, posing a severe challenge to the sustainable supply of lithium resources. However, traditional methods of extracting lithium from ores, brines, and clay are constrained by mining costs and complex operating conditions, resulting in low extraction efficiency and a significant imbalance between lithium reserves and demand. Therefore, developing efficient lithium extraction technologies is crucial for ensuring a secure supply of lithium resources and promoting the sustainable development of the new energy industry.

[0003] Adsorption is a selective separation technique based on the specific interaction between functional materials and target ions. This technique, through a cycle of adsorption-desorption, can efficiently capture and enrich lithium ions from complex solutions. Currently, lithium adsorbents can be divided into two categories: inorganic and organic. Inorganic adsorbents, represented by ion-sieve materials, selectively capture lithium ions through ion exchange by precisely controlling the cavity size or interlayer voids in the crystal structure. These materials exhibit good selectivity for lithium, but generally suffer from severe material degradation and secondary water pollution, hindering large-scale application. Organic adsorbents are mainly crown ether adsorbents, which preferentially capture lithium based on the size matching between the crown ether macrocycle diameter and the metal cation, forming highly stable host-guest complexes. However, the application of crown ethers as lithium adsorbents faces challenges such as poor stability of crown ether monomers, low adsorption capacity, and high cost. Therefore, developing efficient, stable, and economical lithium adsorbents remains a challenge in lithium extraction research. Summary of the Invention

[0004] The purpose of this invention is to provide a fluorinated cyclodextrin polymeric adsorbent, its preparation method, and its applications. By using β-cyclodextrin as a carrier and covalently grafting fluorine-containing segments onto its surface hydroxyl groups, a functional adsorbent with a high density of fluorine adsorption sites is synthesized. Based on Lewis acid-base theory, hard base fluoride ions have a natural affinity for hard acid lithium ions. Through the coordination of fluorine sites with lithium ions, the invention addresses the technical problems of poor adsorption efficiency and low selectivity of existing lithium adsorbents mentioned in the background.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A method for preparing a fluorinated cyclodextrin polymeric adsorbent includes the following steps:

[0007] Step 1: Add β-cyclodextrin and organic solvent 1 to a flask, heat and stir to dissolve under nitrogen protection, cool in an ice-water bath, add 2-bromoisobutyryl bromide dropwise, and heat again to react and obtain the intermediate product bromoisobutyryl β-cyclodextrin.

[0008] Step 2: The bromoisobutyryl β-cyclodextrin is mixed with fluorinated monomers, copper bromide, and N,N,N',N",N"-pentamethyldivinyltriamine in organic solvent 1. Under nitrogen protection, the mixture is stirred to remove oxygen. The reducing agent tin isooctanoate (II) is added to carry out the polymerization reaction. The reaction solution is added dropwise to a poor solvent for precipitation to obtain the fluorinated cyclodextrin polymer adsorbent.

[0009] Furthermore, in step one, the β-cyclodextrin is dried in a forced-air drying oven before use, and the organic solvent 1 is N,N-dimethylformamide or dimethyl sulfoxide.

[0010] Furthermore, in step one, the mass ratio of β-cyclodextrin, organic solvent 1, and 2-bromoisobutyryl bromide is 1:6 ~ 10:8 ~ 13.

[0011] Furthermore, in step one, the reaction heating temperature is 25-60°C, the stirring and dissolving time is 2-10 h, the ice-water bath temperature is 0-5°C, and the reheating time is 12-36 h.

[0012] Furthermore, in step two, the fluorinated monomer is a fluorinated methacrylate such as trifluoroethyl methacrylate or hexafluorobutyl methacrylate.

[0013] Further, in step two, the mass ratio of bromoisobutyryl β-cyclodextrin, fluorinated monomer, copper bromide, N,N,N',N",N"-pentamethyldivinyltriamine, organic solvent 1, and tin(II) is 1:8~20:0.02~0.05:0.2~0.4:60~150:0.6~1.

[0014] Furthermore, in step two, the stirring and deoxygenation time is 1 to 3 hours, the reaction temperature is 50 to 80 degrees Celsius, and the polymerization reaction time is 12 to 36 hours.

[0015] Furthermore, in step two, the undesirable solvent is a polar aprotic solvent such as petroleum ether or methanol.

[0016] This invention provides a fluorinated cyclodextrin polymer adsorbent prepared by the above method.

[0017] This invention provides the application of the above-mentioned fluorinated cyclodextrin polymer adsorbent as a lithium ion adsorbent.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the fluorinated cyclodextrin polymeric adsorbent, its preparation method, and its application:

[0019] A polymer material was prepared by grafting β-cyclodextrin with fluorinated methacrylate. The rigid cavity structure of β-cyclodextrin served as a carrier, and the numerous hydroxyl groups on the fluorinated methacrylate were covalently bonded to the β-cyclodextrin, resulting in a cyclodextrin polymer adsorbent with a high density of fluorine adsorption sites. Fluorine possesses the highest electronegativity and a small atomic radius, along with a strong electron-gaining tendency and strong oxidizing properties. Lithium, on the other hand, is a highly reactive alkali metal with a strong electron-loss tendency and strong reducing ability. Based on the Lewis acid-base theory, fluoride ions, as hard bases, have a natural strong affinity for hard acid lithium ions. Through the coordination of lithium ions with the fluorine sites on the fluorinated cyclodextrin, lithium ions in water are effectively extracted, achieving highly efficient and selective recovery of lithium ions.

[0020] The method for preparing the fluorinated cyclodextrin polymeric adsorbent of this invention is simple and the reaction process is mild. It is suitable for the efficient recovery of lithium ions from complex lithium-containing water bodies, and the adsorption capacity for lithium ions can reach up to 43.5 mg / g. It can selectively separate lithium ions from mixed solutions containing competing ions such as sodium, potassium, calcium, nickel, cobalt, manganese, magnesium, and copper, meeting the practical application scenarios of lithium adsorbents. Attached Figure Description

[0021] Figure 1 The infrared spectrum of the fluorinated cyclodextrin polymeric adsorbent prepared in this invention;

[0022] Figure 2 The scanning electron microscope image of the fluorinated cyclodextrin polymeric adsorbent prepared in this invention;

[0023] Figure 3 X-ray diffraction pattern of the fluorinated cyclodextrin polymeric adsorbent prepared in this invention;

[0024] Figure 4 The isothermal adsorption curve of the fluorinated cyclodextrin polymer adsorbent of this invention is shown below.

[0025] Figure 5 The adsorption kinetics curve of the fluorinated cyclodextrin polymer adsorbent of this invention is shown below.

[0026] Figure 6 The adsorption capacity of the fluorinated cyclodextrin polymer adsorbent for lithium ions at different pH values ​​of this invention;

[0027] Figure 7 This invention demonstrates the selective adsorption capacity of the fluorinated cyclodextrin polymer adsorbent for lithium ions. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This invention provides a method for preparing a fluorinated cyclodextrin polymeric adsorbent, comprising the following steps:

[0031] (1) After drying 3.0 g of β-cyclodextrin in a forced-air drying oven for 24 h, it was placed in a 250 mL three-necked flask, and 30 mL of organic solvent N,N-dimethylformamide was added. Nitrogen gas was introduced for protection, and the mixture was placed in an oil bath at 25 °C and continuously stirred magnetically for 2 h until the β-cyclodextrin was completely dissolved. Then, the mixture was cooled to 0 °C in an ice-water bath, and 15 mL of 2-bromoisobutyryl bromide was added dropwise to the solution using a separatory funnel. The mixture was heated again for 24 h to obtain the intermediate product bromoisobutyryl β-cyclodextrin.

[0032] (2) 50 mg of bromoisobutyryl β-cyclodextrin, 1 g of hexafluorobutyl methacrylate, 10 mg of copper bromide and 1 mL of N,N,N',N",N"-pentamethyldivinyltriamine were added to 30 mL of N,N-dimethylformamide. After stirring at 60 °C for 1 h under a nitrogen atmosphere, 160 μL of tin(II) isooctanoate was added and the reaction was continued for 24 h. After the reaction was complete, it was added dropwise to the undesirable solvent petroleum ether for precipitation to obtain fluorinated cyclodextrin polymer adsorbent.

[0033] The fluorinated cyclodextrin polymer adsorbent prepared in Example 1 was characterized by infrared spectroscopy.

[0034] in Figure 1 The infrared spectrum of the fluorinated cyclodextrin polymer adsorbent shows that the adsorbent not only exhibits the inherent characteristic peaks of β-cyclodextrin, but also the characteristic peaks of -C=O and -CF, indicating that the prepared β-cyclodextrin adsorbent was successfully grafted with fluorine chains, and the fluorinated cyclodextrin polymer adsorbent was successfully synthesized.

[0035] Scanning electron microscopy characterization of the fluorinated cyclodextrin polymeric adsorbent prepared in Example 1:

[0036] Figure 2The image shows a scanning electron microscope (SEM) image of a fluorinated cyclodextrin polymer adsorbent. As can be seen from the image, the adsorbent material has enhanced surface wrinkling and a multi-plate-like stacked structure. This structure facilitates the adsorption of lithium ions on the fluorinated cyclodextrin polymer adsorbent.

[0037] X-ray diffraction characterization of the fluorinated cyclodextrin polymeric adsorbent prepared in Example 1:

[0038] Figure 3 The image shows the X-ray diffraction pattern of the fluorinated cyclodextrin polymeric adsorbent. The X-ray diffraction pattern of β-cyclodextrin shows sharp, high-intensity characteristic diffraction peaks in the 2θ range of 10°–40°, which is typical of the crystalline structure of β-cyclodextrin. The X-ray diffraction pattern of the fluorinated cyclodextrin polymeric adsorbent exhibits amorphous peaks, indicating a loose molecular arrangement within the material, making active sites more easily exposed and allowing them to bind with lithium ions, thereby increasing the adsorption capacity.

[0039] Example 2:

[0040] The fluorinated cyclodextrin polymeric adsorbent prepared in Example 1 was subjected to isothermal adsorption on lithium ion aqueous solutions of different concentrations to illustrate the adsorption capacity of the fluorinated cyclodextrin polymeric adsorbent.

[0041] Test method:

[0042] (1) Prepare lithium chloride aqueous solutions with lithium ion concentrations of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 80 mg / L, 100 mg / L, 120 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, 400 mg / L and 500 mg / L respectively, and add the above solutions into conical flasks respectively;

[0043] (2) Take the prepared fluorinated cyclodextrin polymer adsorbent and add it to the above conical flask to maintain the adsorbent concentration at 1 g / L. Place the suspension in a constant temperature shaker for adsorption experiment. Set the temperature to 25 ℃ and the rotation speed to 180 rpm, and shake continuously for 24 h.

[0044] (3) Take the ion solution before and after adsorption in the conical flask, filter it, and then use an inductively coupled plasma spectrometer to determine the lithium ion concentration in the solution.

[0045] Figure 4 The above-prepared fluorinated cyclodextrin polymeric adsorbent is shown as an isothermal adsorption curve. The results indicate that the maximum adsorption capacity Q of the fluorinated cyclodextrin polymeric adsorbent for lithium ions is [value missing]. max The concentration was 43.5 mg / g, and Langmuir model fitting was performed, indicating that the adsorption of lithium ions by the adsorbent is monolayer adsorption.

[0046] Example 3:

[0047] The adsorption kinetics of the fluorinated cyclodextrin polymer adsorbent prepared in Example 1 on lithium ion solution were determined to illustrate the adsorption equilibrium time of the fluorinated cyclodextrin polymer adsorbent.

[0048] Test method:

[0049] (1) Take 400 mg of the prepared fluorinated cyclodextrin polymer adsorbent and add it to 400 mL of a solution containing an initial concentration of 300 mg L. -1 In a beaker containing an aqueous lithium-ion solution;

[0050] (2) Place the beaker in a constant temperature shaker for adsorption experiments. Set the temperature to 25 ℃ and the rotation speed to 180 rpm. Use a syringe to take 1 mL of suspension at different time intervals (0, 5, 10, 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 270, 300, 330, 360, 390, 420, 450, 480, 510, 540, 570, 600, 900, 1100, 1200, 1260, 1320, 1440 min).

[0051] (3) After filtration of the suspension, the lithium ion concentration in the solution was determined by inductively coupled plasma spectrometry.

[0052] Figure 5 The adsorption kinetics curve of the fluorinated cyclodextrin polymer adsorbent prepared above is shown. The results indicate that the adsorption equilibrium time of the fluorinated cyclodextrin polymer adsorbent is 280 min, which conforms to the pseudo-second-order kinetic model. This shows that the rate-controlling step in the adsorption process is mainly determined by the chemisorption of lithium ions by the adsorbent.

[0053] Example 4:

[0054] The fluorinated cyclodextrin polymeric adsorbent prepared in Example 1 was subjected to adsorption experiments in lithium-ion solutions under different pH conditions to illustrate the effect of pH on lithium-ion adsorption:

[0055] Test method:

[0056] (1) Prepare lithium ion solutions with pH values ​​of 0, 2, 4, 6, 8, 10, and 12, and a concentration of 300 mg / L respectively; place the lithium ion solutions with different pH values ​​into conical flasks respectively;

[0057] (2) Weigh the prepared fluorinated cyclodextrin polymer adsorbent and put it into an aqueous solution containing lithium ions at a concentration of 300 mg / L with pH values ​​of 0, 2, 4, 6, 8, 10, and 12 respectively. The adsorbent concentration is 1 g / L. The adsorbent is placed in a constant temperature shaker with parameters set to 25 °C, 180 rpm, and 24 h for adsorption experiments.

[0058] (3) Take the ion solution before and after adsorption in the conical flask, filter it, and then use an inductively coupled plasma spectrometer to determine the lithium ion concentration in the solution.

[0059] Figure 6 The graph shows the adsorption capacity of the fluorinated cyclodextrin polymer adsorbent for lithium ions under different pH conditions. The results indicate that the fluorinated cyclodextrin polymer adsorbent has the best adsorption effect on lithium ions under neutral conditions.

[0060] Example 5:

[0061] The adsorption selectivity of the fluorinated cyclodextrin polymeric adsorbent prepared in Example 1 for lithium ions was evaluated:

[0062] Test method:

[0063] (1) Prepare a 300 mg / L mixed aqueous solution of lithium ions, sodium ions, potassium ions, magnesium ions, calcium ions, nickel ions, cobalt ions, copper ions and manganese ions, and place it in an Erlenmeyer flask;

[0064] (2) Weigh 20 mg of the prepared fluorinated cyclodextrin polymer adsorbent and add it to a 300 mg / L mixed aqueous solution of lithium ions, sodium ions, potassium ions, magnesium ions, calcium ions, nickel ions, cobalt ions, copper ions and manganese ions. The adsorbent concentration is 1 g / L. Place it in a constant temperature shaker for adsorption experiment. The parameters are set as follows: temperature 25 °C, rotation speed 180 rpm, and continuous shaking for 24 h.

[0065] (3) Take the ion solution before and after adsorption in the conical flask, filter it, and then use an inductively coupled plasma spectrometer to determine the concentration of various ions in the solution.

[0066] Figure 7 The selective adsorption capacity of the aforementioned fluorinated cyclodextrin polymer adsorbent for lithium ions demonstrates that it can efficiently separate lithium ions from a mixed solution containing sodium, potassium, magnesium, calcium, nickel, cobalt, copper, and manganese ions. This indicates that the fluorinated cyclodextrin polymer adsorbent has the potential to separate and recover lithium ions from complex lithium-containing wastewater.

[0067] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0068] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluorinated cyclodextrin polymeric adsorbent, characterized in that, Includes the following steps: Step 1: Add β-cyclodextrin and organic solvent 1 to a flask, heat and stir to dissolve under nitrogen protection, cool in an ice-water bath, add 2-bromoisobutyryl bromide dropwise, and heat again to react and obtain the intermediate product bromoisobutyryl β-cyclodextrin. Step 2: The bromoisobutyryl β-cyclodextrin is mixed with fluorinated monomers, copper bromide, and N,N,N',N",N"-pentamethyldivinyltriamine in organic solvent 1. Under nitrogen protection, the mixture is stirred to remove oxygen. The reducing agent tin isooctanoate (II) is added to carry out the polymerization reaction. The reaction solution is added dropwise to a poor solvent for precipitation to obtain the fluorinated cyclodextrin polymer adsorbent.

2. The preparation method according to claim 1, characterized in that, In step one, the β-cyclodextrin is dried in a forced-air drying oven before use, and the organic solvent 1 is N,N-dimethylformamide or dimethyl sulfoxide.

3. The preparation method according to claim 1, characterized in that, In step one, the mass ratio of β-cyclodextrin, organic solvent 1, and 2-bromoisobutyryl bromide is 1:6 ~ 10:8 ~ 13.

4. The preparation method according to claim 1, characterized in that, In step one, the reaction heating temperature is 25-60℃, the stirring and dissolving time is 2-10 h, the ice-water bath temperature is 0-5℃, and the reheating time is 12-36 h.

5. The preparation method according to claim 1, characterized in that, In step two, the fluorinated monomers are fluorinated methacrylates such as trifluoroethyl methacrylate and hexafluorobutyl methacrylate.

6. The preparation method according to claim 1, characterized in that, In step two, the mass ratio of bromoisobutyryl β-cyclodextrin, fluorinated monomer, copper bromide, N,N,N',N",N"-pentamethyldivinyltriamine, organic solvent 1, and tin(II) isooctanoate 1:8~20:0.02~0.05:0.2~0.4:60~150:0.6~1.

7. The preparation method according to claim 1, characterized in that, In step two, the stirring and deoxygenation time is 1 to 3 hours, the reaction temperature is 50 to 80 ℃, and the polymerization reaction time is 12 to 36 hours.

8. The preparation method according to claim 1, characterized in that, In step two, the unsuitable solvent is a polar aprotic solvent such as petroleum ether or methanol.

9. The fluorinated cyclodextrin polymeric adsorbent prepared by the preparation method according to any one of claims 1-8.

10. The application of the fluorinated cyclodextrin polymer adsorbent according to claim 9 as a lithium-ion adsorbent.

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