Polyacrylonitrile-based chelating fibers, and preparation method therefor and use thereof

Abstract

Polyacrylonitrile-based chelating fibers, and a preparation method therefor and the use thereof. Polyacrylonitrile fibers are catalytically hydrolyzed and cleaned by means of a microwave-assisted method in an alkaline solution; after the fibers are soaked in and washed with an acid liquor, catalytic amination is performed by utilizing a solvothermal method, thereby modifying the surface of the fibers, so as to prepare a polyacrylonitrile-based chelating fiber crude product containing aminos and acylaminos; and finally, the crude product is purified to obtain polyacrylonitrile-based chelating fibers. The chelating fibers prepared by means of the method contain more coordination atoms which are distributed on the surface of the fibers, and have a large specific surface area, a high saturated adsorption capacity of gallium / indium ions, and a high adsorption speed; and no organic pollutant is generated during the adsorption separation process, such that the method is relatively friendly to the environment, thereby solving the problems of the low extraction efficiency, poor dynamic performance and being unfriendly to the environment present in the wet treatment of dissipated metals, such as gallium and indium, in the prior art.

Description

Polyacrylonitrile-based chelate fiber and its preparation method and application Technical field:

[0001] The present invention relates to the field of polymer modification, and in particular to a polyacrylonitrile-based chelate fiber and a preparation method and application thereof. Background technology:

[0002] Gallium and indium are currently rare metals in the boron group (BGA). They are supporting materials for advanced technologies and new materials, playing a vital role in aerospace, energy, and communications. However, these rare metals do not have independent deposits in the Earth's crust; they are mostly associated with aluminum or zinc minerals. Gallium and indium are present in extremely low concentrations and are widely distributed. In the context of energy conservation, consumption reduction, and pollution reduction, research on efficient, clean, and short-process extraction of rare metals such as gallium and indium is of great significance.

[0003] Currently, both gallium and indium can be extracted using solvent extraction and resin adsorption. In a sulfuric acid system, gallium and indium can be extracted using hydroxamic acid. In an alkaline system, gallium is adsorbed using amidoxime chelating resins; in a sulfuric acid system, indium is adsorbed using ion exchange resins. Because the concentration of dispersed metal ions in the solution is low, multi-stage extraction is necessary to achieve a high direct metal yield, indicating the low efficiency of existing extraction processes. Furthermore, the extraction method produces organic pollutants that pose a certain risk to water bodies. While the chelating resin method is convenient, fast, reusable, and minimally polluting to the environment, it undergoes chemical cross-linking, resulting in a slow diffusion rate within the resin microspheres and a longer time required for the metal ion concentration to reach adsorption equilibrium. Summary of the invention:

[0004] The purpose of the present invention is to provide a polyacrylonitrile-based chelate fiber and its preparation method and application, which solves the problems of low extraction efficiency, poor kinetic performance and environmental unfriendliness in the wet treatment of rare metals such as gallium and indium in the prior art.

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

[0006] A method for preparing polyacrylonitrile-based chelate fiber, the method comprising the following steps:

[0007] (1) using ultrasonic method to clean the surface of polyacrylonitrile fiber alternately with water and lower alcohol solvents to obtain clean polyacrylonitrile fiber;

[0008] (2) using a microwave-assisted method to catalytically hydrolyze clean polyacrylonitrile fibers in an alkaline solution at 90-100°C to obtain polyacrylonitrile fibers containing carboxylate; the microwave power is 200-600W, and the hydrolysis time is 0.5-1.0h;

[0009] (3) washing the polyacrylonitrile-based fiber obtained in step (2) with pure water to remove the alkali solution attached to the fiber surface, wherein the washing end point is when the pH value of the washing water is close to 7.0;

[0010] (4) soaking the polyacrylonitrile-based fiber containing carboxylate obtained in step (3) in an acid solution for 1 to 4 hours, and then washing with pure water to wash away the acid solution attached to the fiber surface, wherein the washing end point is when the pH value of the washing water is close to 7.0, thereby obtaining the polyacrylonitrile-based fiber containing carboxyl groups;

[0011] (5) catalyzing the amination of the carboxyl-containing polyacrylonitrile-based fiber obtained in step (4) in a polyamine solution at 100-130° C. by a solvent thermal method, wherein the cyano group and the carboxyl group on the carboxyl-containing polyacrylonitrile-based fiber undergo a condensation reaction with the polyamine to obtain a crude polyacrylonitrile-based chelate fiber containing amino groups and amide groups; the solvent used is water, ethylene glycol, or a mixed solvent consisting of water and ethylene glycol, wherein ethylene glycol is preferred; and the catalyst used is aluminum trichloride, tin tetrachloride, lanthanum chloride, or cerium chloride, wherein cerium chloride is preferred;

[0012] (6) The crude chelating fiber is washed alternately with water and low-grade alcohol by ultrasonic method; and then dried at 50-70°C for 0.5-2.0h to remove the water and alcohol adsorbed on the surface of the wet chelating fiber, thereby obtaining dry polyacrylonitrile-based chelating fiber containing amide and amine groups.

[0013] The lower alcohol in step (1) is methanol or ethanol, preferably ethanol. The ultrasonic frequency used in the ultrasonic method in step (1) is 20 to 40 kHz, and the average sound intensity is 1.0 to 2.0 W / cm 2 , the temperature is room temperature ~ 40℃, and the time is 5 ~ 10 minutes.

[0014] Step (1) uses ultrasonic cleaning to alternately wash away ash and oil stains on the surface of polyacrylonitrile fiber using water and lower alcohol solvents. Since polyacrylonitrile fiber has a certain adsorption effect, ash, oil stains and gases are usually adsorbed on the fiber surface. The principle of ultrasonic cleaning is that when ultrasonic waves of a certain frequency and sound intensity are irradiated on a liquid, under the action of the negative pressure phase of the sound wave, the jet generated by the liquid impacts the dirt on the fiber surface, resulting in a clean fiber surface.

[0015] Step (2) is to hydrolyze the polyacrylonitrile fiber to a certain extent under the catalytic action of alkali in a microwave field to obtain fiber containing sodium carboxylate.

[0016] The alkali used is one of sodium hydroxide, potassium hydroxide and sodium carbonate, among which sodium hydroxide is preferred.

[0017] When sodium carbonate is selected, the concentration of the alkali solution is 2.0wt% to 10wt%; when sodium hydroxide is selected, the concentration of the alkali solution is 0.5wt% to 2.0wt%; when potassium hydroxide is selected, the concentration of the alkali solution is 0.5wt% to 2.0wt%.

[0018] The solid-liquid ratio of the polyacrylonitrile fiber to the alkali solution is 1g:20-40mL.

[0019] The acid used in the acid solution of step (4) is one of hydrochloric acid and sulfuric acid, among which hydrochloric acid is preferred.

[0020] When hydrochloric acid is selected, the concentration of hydrochloric acid is 0.1 to 1.0 mol / L; when sulfuric acid is selected, the concentration of sulfuric acid is 0.05 to 0.5 mol / L.

[0021] The solid-liquid ratio of the polyacrylonitrile-based fiber to the acid solution is 1 g: 20-40 mL.

[0022] The polyamine used in step (5) is one of ethylenediamine, diethylenetriamine and triethylenetetramine, preferably diethylenetriamine.

[0023] The volume concentration of the polyamine in the polyamine solution is 20 vol% to 50 vol%, and the solid-liquid ratio of the polyacrylonitrile-based fiber to the polyamine solution is 1 g: 20 to 80 mL.

[0024] The amount of the catalyst used is 0.25wt% to 5.0wt% of the fiber amount, and the reaction time is 2 to 6 hours.

[0025] The step (6) is to use ultrasonic method to wash away the solvent and residual reactants attached to the fiber surface with water and lower alcohol alternately. The lower alcohol is methanol or ethanol, preferably ethanol. The ultrasonic frequency used is 20-40kHz, and the average sound intensity is 1.0-2.0W / cm 2 , the temperature is room temperature ~ 40℃, and the time is 5 ~ 10 minutes.

[0026] The present invention also protects the polyacrylonitrile-based chelated fiber obtained by the above-mentioned preparation method, which uses polyacrylonitrile fiber as the skeleton, and the functional groups on the skeleton that coordinate with metal ions are amino groups and amide groups. The coordinating nitrogen atoms in the functional groups are combined with carbon atoms in the form of covalent bonds, wherein the loading amount of amide groups and amine groups is 2 to 10 mmol / g of dry polyacrylonitrile fiber.

[0027] Polyacrylonitrile fiber (PAN fiber) is an industrial fiber with excellent mechanical strength, chemical stability, and thermal stability. Its skeleton has a large aspect ratio, and its specific surface area is 5-6 times greater than that of macroporous polyacrylonitrile resin. The present invention utilizes microwave-assisted catalytic hydrolysis in an alkaline solution to clean the polyacrylonitrile fiber. After acid soaking and washing, the fiber is subjected to solvent-thermal catalytic amination to modify the PAN fiber surface, yielding a crude polyacrylonitrile-based chelated fiber containing amino and amide groups. This results in a chelated fiber containing a large number of coordinating atoms distributed on the fiber surface. Because the chelated fiber has a small diameter, a large specific surface area, and functional groups distributed on the fiber surface, along with excellent selectivity and kinetic properties, it can adsorb rare metal elements such as gallium and indium at a faster rate and with a higher adsorption capacity. This fiber has promising development prospects in the field of enrichment and separation of rare metal elements such as gallium and indium.

[0028] Therefore, the present invention also protects the use of the polyacrylonitrile-based chelate fiber obtained by the above preparation method in the adsorption separation or enrichment of scattered metal ions such as gallium and indium.

[0029] The present invention has the following beneficial effects: It utilizes microwave-assisted catalytic hydrolysis in an alkaline solution to clean polyacrylonitrile fibers. After acid soaking and washing, it undergoes solvothermal catalytic amination at 100-130°C to modify the PAN fiber surface, producing a crude polyacrylonitrile-based chelate fiber containing amino and amide groups. This is then purified to yield the polyacrylonitrile-based chelate fiber. The fibers of the present invention are chelate fibers containing a large number of coordinating atoms distributed on the fiber surface, resulting in a large specific surface area, a high saturated adsorption capacity for gallium and indium ions, and a rapid adsorption rate. Furthermore, the adsorption and separation process does not produce organic pollutants, making it environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is an infrared spectrum of the polyacrylonitrile-based chelate fiber obtained in Example 1 of the present invention.

[0031] FIG2 is a microscopic morphology of the polyacrylonitrile-based chelate fiber obtained in Example 4 of the present invention. Specific implementation method:

[0032] The following is a further description of the present invention, but not a limitation of the present invention.

[0033] Example 1:

[0034] Take 0.5g polyacrylonitrile fiber and test it at a power of 25kW and a sound intensity of 1.5W / cm 2Under room temperature conditions, first ultrasonically clean in water for 5 minutes, then ultrasonically clean in ethanol for 5 minutes to obtain clean polyacrylonitrile fiber. At a microwave power of 200W and a temperature of 90°C, the clean polyacrylonitrile fiber was placed in 15mL of 0.5% sodium hydroxide solution for catalytic hydrolysis for 0.5h, and polyacrylonitrile fiber containing sodium carboxylate was separated, and then washed with water until the pH value of the washing water was 7.0. The above fiber was soaked in 15mL of 1.0mol / L hydrochloric acid solution for 2h to separate the polyacrylonitrile fiber containing carboxylate, and then washed with water until the pH value of the washing water was close to 7.0. The wet polyacrylonitrile fiber was placed in 40mL of an aqueous solution mixed with 25% ethylenediamine and 5mg of aluminum trichloride, and catalytic amination was carried out at 120°C for 3h. After separation, it was heated at a power of 25kW and a sound intensity of 1.5W / cm 2 Under the conditions of room temperature, the fibers were first ultrasonically cleaned in water for 5 minutes, and then ultrasonically cleaned in ethanol for 5 minutes to obtain clean wet polyacrylonitrile-based chelate fibers. Finally, the fibers were dried at 50°C for 2 hours to obtain dry polyacrylonitrile-based chelate fibers. Its infrared spectrum is shown in Figure 1. The 1075 cm -1 The corresponding amino group CN stretching vibration is 3199 cm -1 Broad peak, 1582cm -1 The sharp peaks at 1610 cm correspond to the stretching vibration and in-plane bending vibration peaks of the amino group; -1 The appearance of the above characteristic peaks indicates that the polyacrylonitrile-based chelate fiber has been successfully grafted with amide and amine groups.

[0035] The element content of the chelating fiber was analyzed, and the grafting amount of the amide group was calculated based on the oxygen content. The grafting amount of the amine group was then calculated by subtracting the grafting amount of the amide group from the consumption of the aminating agent. Chemical analysis showed that the loading amount of the amine and amide groups on the prepared polyacrylonitrile-based chelating fiber was 4 mmol / g dry fiber, which has a high adsorption capacity for metal ions.

[0036] The polyacrylonitrile-based chelate fiber repeating unit structure obtained in this embodiment is as follows:

[0037] Where R is a methylene group with 2 carbon atoms, and n is the degree of polymerization.

[0038] 0.01 g of polyacrylonitrile-based chelating fiber was soaked in 100 mL of 500 mg of Ga 3+ In the acidic solution, the time to reach equilibrium is only 10 minutes, which shows that the amine-containing chelating fiber has a higher adsorption rate.

[0039] Example 2

[0040] Take 1.0g of polyacrylonitrile fiber and test it at a power of 35kW and a sound intensity of 1.5W / cm 2 Under room temperature conditions, first ultrasonically clean in water for 8 minutes, then ultrasonically clean in ethanol for 10 minutes to obtain clean polyacrylonitrile fiber. At a microwave power of 400W and a temperature of 100°C, the clean polyacrylonitrile fiber was placed in 30mL of 1% sodium hydroxide solution for catalytic hydrolysis for 0.5h, and polyacrylonitrile fiber containing sodium carboxylate was separated, and then washed with water until the washing water was neutral. The above fiber was soaked in 35mL of 0.5mol / L sulfuric acid solution for 2h to separate polyacrylonitrile fiber containing carboxylate, and then washed with water until the washing water was neutral. The wet polyacrylonitrile fiber was placed in 60mL of ethylene glycol solution mixed with 35% ethylenediamine and 12mg of aluminum trichloride, and catalytic amination was carried out at 110°C for 5h. After separation, it was heated at a power of 40kW and a sound intensity of 2.0W / cm 2 The fibers were first ultrasonically cleaned in water for 8 minutes at 30°C and then in ethanol for 5 minutes to obtain clean wet polyacrylonitrile-based chelate fibers, which were then dried at 60°C for 1 hour to obtain dry polyacrylonitrile-based chelate fibers.

[0041] Chemical analysis showed that the loading amount of amino and amide groups on the prepared polyacrylonitrile chelate fiber was 6 mmol / g dry fiber. 0.01 g of the above polyacrylonitrile chelate fiber was soaked in 150 mL of 200 mg In solution. 3+ The time to reach equilibrium in the acidic solution is 8 minutes, which indicates that the chelating fiber of this embodiment has a higher adsorption rate.

[0042] Comparative Example 1: The conventional reflux hydrolysis and water bath amination method was used to prepare polyacrylonitrile-based chelate fiber.

[0043] Take 1.0g of polyacrylonitrile fiber and place it in 30mL of 1% sodium hydroxide solution. Hydrolyze it under reflux at 100°C for 0.5h to separate the polyacrylonitrile fiber containing sodium carboxylate. Then wash it with water until the wash water is neutral. Soak the above fiber in 35mL of 0.5mol / L sulfuric acid solution for 2h to separate the polyacrylonitrile fiber containing carboxylate. Then wash it with water until the wash water is neutral. Place the wet polyacrylonitrile fiber in 60mL of ethylene glycol solution containing 35% ethylenediamine and aminize it in a water bath at 90°C for 5h. After separation, wash it with water to obtain clean wet polyacrylonitrile-based chelate fiber. Dry it at 60°C for 1h to obtain dry polyacrylonitrile-based chelate fiber.

[0044] Chemical analysis showed that the loading amount of amino and amide groups on the polyacrylonitrile-based chelate fiber prepared in Comparative Example 1 was 1 mmol / g dry fiber. 0.01 g of the polyacrylonitrile-based chelate fiber was soaked in 150 mL of 200 mg of In solution. 3+In the acidic solution, the time to reach equilibrium is 30 minutes.

[0045] Comparison between Example 2 and Comparative Example 1 shows that Example 2 has better effect.

[0046] Example 3

[0047] Take 0.5g of polyacrylonitrile fiber and test it at a power of 40kW and a sound intensity of 2.0W / cm 2 and room temperature conditions, first ultrasonically clean in water for 5 minutes, then ultrasonically clean in methanol for 5 minutes to obtain clean polyacrylonitrile fiber. At a microwave power of 500W and a temperature of 95°C, the clean polyacrylonitrile fiber was placed in 15mL of 0.5% potassium hydroxide solution for catalytic hydrolysis for 1h, and polyacrylonitrile fiber containing sodium carboxylate was separated, and then washed with water until the pH of the washing water was 7.0. The above-mentioned hydrolyzed fiber was soaked in 15mL of 1.0mol / L hydrochloric acid solution for 2.5h to separate the polyacrylonitrile fiber containing carboxylate, and then washed with water until the pH of the washing water was 7.0. The wet polyacrylonitrile fiber was placed in 30mL of ethylene glycol solution mixed with 40% tetraethylenetriamine and 5mg of tin tetrachloride, and catalytic amination was carried out at 120°C for 6h. After separation, it was heated at a power of 25kW and a sound intensity of 1.5W / cm 2 Under room temperature and ultrasonic cleaning conditions, the fibers were first ultrasonically cleaned in water for 5 minutes and then in methanol for 8 minutes to obtain clean wet polyacrylonitrile-based chelate fibers. Drying at 50°C for 2 hours gave dry polyacrylonitrile-based chelate fibers.

[0048] Chemical analysis showed that the loading amount of amino groups and amide groups on the prepared polyacrylonitrile-based chelating fiber was 8 mmol / g dry fiber.

[0049] 0.01 g of polyacrylonitrile-based chelating fiber was soaked in 200 mL of 500 mg of Ga 3+ In the acidic solution, the time to reach equilibrium is only 5 minutes, which shows that the chelating fiber has a higher adsorption rate.

[0050] Example 4

[0051] Take 1.5g of polyacrylonitrile fiber and test it at a power of 30kW and a sound intensity of 1.0W / cm 2Under room temperature conditions, first ultrasonically clean in water for 5 minutes, then ultrasonically clean in ethanol for 10 minutes to obtain clean polyacrylonitrile fiber. At a microwave power of 400W and a temperature of 95°C, the clean polyacrylonitrile fiber was placed in 40mL of 1.0% sodium hydroxide solution for catalytic hydrolysis for 1 hour, and polyacrylonitrile fiber containing sodium carboxylate was separated, and then washed with water until the pH of the washing water was 7.0. The above-mentioned hydrolyzed fiber was soaked in 30mL of 0.5mol / L hydrochloric acid solution for 4 hours to separate polyacrylonitrile fiber containing carboxylate, and then washed with water until the pH value of the washing water was close to 7.0. The wet polyacrylonitrile fiber was placed in 60mL of ethylene glycol solution mixed with 35% diethylenetriamine and 5mg of cerium trichloride, and catalytic amination was carried out at 120°C for 4 hours. After separation, it was heated at a power of 35kW and a sound intensity of 1.5W / cm 2 Under room temperature and ultrasonic cleaning conditions, the fibers were first ultrasonically cleaned in water for 5 minutes and then in methanol for 10 minutes to obtain clean wet polyacrylonitrile-based chelate fibers, which were then dried at 50°C for 1.5 hours to obtain dry polyacrylonitrile-based chelate fibers.

[0052] Chemical analysis showed that the loading amount of amide and amine groups on the prepared polyacrylonitrile-based chelating fiber was 10 mmol / g dry fiber.

[0053] 0.01 g of polyacrylonitrile chelate fiber was soaked in 200 mL of 400 mg of In 3+ The time to reach equilibrium in sulfuric acid solution is only 6 minutes, which shows that the chelating fiber has a higher adsorption rate.

Claims

1. A method for preparing polyacrylonitrile-based chelate fiber, characterized in that: The method comprises the following steps: (1) using an ultrasonic method to alternately clean the surface of the polyacrylonitrile fiber with water and a lower alcohol solvent to obtain a clean polyacrylonitrile fiber; (2) using a microwave-assisted method to catalytically hydrolyze clean polyacrylonitrile fibers in an alkaline solution at 90 to 100° C. to obtain polyacrylonitrile fibers containing carboxylate; the microwave power is 200 to 600 W, and the hydrolysis time is 0.5 to 1.0 h; (3) washing the polyacrylonitrile-based fiber obtained in step (2) with pure water to remove the alkali solution attached to the fiber surface, wherein the washing end point is when the pH value of the washing water is close to 7.0; (4) soaking the polyacrylonitrile-based fiber containing carboxylate obtained in step (3) with an acid solution for 1 to 4 hours, and then washing with pure water to wash away the acid solution attached to the fiber surface, wherein the washing end point is when the pH value of the washing water is close to 7.0, thereby obtaining the polyacrylonitrile-based fiber containing carboxyl groups; (5) catalyzing the amination of the carboxyl-containing polyacrylonitrile-based fiber obtained in step (4) in a polyamine solution at 100-130° C. by a solvothermal method to obtain a crude polyacrylonitrile-based chelated fiber containing amino groups and amide groups; the solvent used is water, ethylene glycol, or a mixed solvent of water and ethylene glycol; and the catalyst used is aluminum chloride, tin tetrachloride, lanthanum chloride, or cerium chloride; (6) The crude chelated fiber is washed alternately with water and low-grade alcohol by ultrasonic method, and then dried at 50-70° C. for 0.5-2.0 h to obtain dry polyacrylonitrile-based chelated fiber containing amide and amine groups.

2. The preparation method according to claim 1, characterized in that: The lower alcohol in step (1) is methanol or ethanol.

3. The preparation method according to claim 1, characterized in that: The ultrasonic method in step (1) uses an ultrasonic frequency of 20 to 40 kHz and an average sound intensity of 1.0 to 2.0 W / cm 2 , the temperature is room temperature ~ 40℃, and the time is 5 ~ 10 minutes.

4. The preparation method according to claim 1, characterized in that: The alkali used in step (2) is one of sodium hydroxide, potassium hydroxide and sodium carbonate; when sodium carbonate is selected, the concentration of the alkali solution is 2.0wt% to 10wt%; when sodium hydroxide is selected, the concentration of the alkali solution is 0.5wt% to 2.0wt%; when potassium hydroxide is selected, the concentration of the alkali solution is 0.5wt% to 2.0wt%.

5. The preparation method according to claim 1, characterized in that: The solid-to-liquid ratio of the polyacrylonitrile fiber to the alkali solution in step (2) is 1 g: 20-40 mL.

6. The preparation method according to claim 1, characterized in that: The acid used in the acid solution of step (4) is one of hydrochloric acid and sulfuric acid; when hydrochloric acid is selected, the concentration of hydrochloric acid is 0.1-1.0 mol / L; when sulfuric acid is selected, the concentration of sulfuric acid is 0.05-0.5 mol / L; the solid-liquid ratio of the polyacrylonitrile-based fiber to the acid solution is 1 g: 20-40 mL.

7. The preparation method according to claim 1, characterized in that: The polyamine used in step (5) is one of ethylenediamine, diethylenetriamine, and triethylenetetramine; the volume concentration of the polyamine in the polyamine solution is 20vol% to 50vol%, and the solid-liquid ratio of the polyacrylonitrile-based fiber to the polyamine solution is 1g:20 to 80mL; the amount of the catalyst used in step (5) is 0.25wt% to 5.0wt% of the fiber amount, and the reaction time is 2 to 6h.

8. The preparation method according to claim 1, characterized in that: The lower alcohol in step (6) is methanol or ethanol; the ultrasonic frequency used is 20-40kHz, and the average sound intensity is 1.0-2.0W / cm 2 , the temperature is room temperature ~ 40℃, and the time is 5 ~ 10 minutes.

9. The polyacrylonitrile-based chelate fiber obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The polyacrylonitrile fiber is used as the skeleton, and the functional groups on the skeleton that coordinate with the metal ions are amine groups and amide groups. The coordinating nitrogen atoms in the functional groups are combined with carbon atoms in the form of covalent bonds, and the loading amount of amide groups and amine groups is 2 to 10 mmol / g of dry polyacrylonitrile fiber.

10. Use of the polyacrylonitrile-based chelate fiber obtained by the preparation method according to any one of claims 1 to 8 in the adsorption separation or enrichment of gallium and indium ions.

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