Preparation method and application of polyelectrolyte adsorbing fiber composite organic framework material

Abstract

The application discloses a preparation method and application of a polyelectrolyte adsorption fiber composite organic framework material, and belongs to the technical field of heavy metal enrichment recovery and removal in wastewater. The preparation method is as follows: sodium alginate and sodium carboxymethyl cellulose are melted into deionized water, and sodium alginate-sodium carboxymethyl cellulose fibers are obtained through freeze-drying; the composite fibers are put into a calcium chloride solution for solidification, vacuum filtration and freeze-drying again to obtain the solidified composite fibers; ZIF-90 crystal material is prepared; the solidified composite fibers are put into a chitosan and ZIF-90 mixed solution for soaking at room temperature, and then are put into deionized water to wash away the chitosan solution; after vacuum filtration, the polyelectrolyte adsorption fiber composite organic framework material is obtained through complete freeze-drying again. The material obtained by the application has high porosity and specific surface area, is simple in process, low in cost, green and environment-friendly, has strong adsorption selectivity for specific metal ions, and is convenient for the recovery and treatment of metals in wastewater.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a polyelectrolyte adsorption fiber composite organic framework material, belonging to the field of heavy metal enrichment, recovery and removal technology in wastewater. Background Technology

[0002] Radioactive cobalt-60 is a widely concerned pollutant in the nuclear industry. It is produced in various stages of nuclear production, including condensate from nuclear power reactors and wastewater from nuclear fuel plant operations. Due to its high radioactivity, its release into the natural world without strict treatment would have immeasurable consequences. However, metallic cobalt has a wide range of applications in nature, particularly in the electronics industry. Wastewater from the dismantling of electronic products in the electronics recycling industry and from mineral mining also contains metallic cobalt. Therefore, national policies stipulate that the cobalt content in drinking water should be below 0.05 mg / L.

[0003] Radioactive cobalt-60 is widely used in various biological, scientific research, and medical fields, including plant breeding, radiation sterilization, cancer treatment, and structural detection. Its applications are broad and its economic value is considerable. Adsorption and recovery of cobalt can effectively prevent radioactive wastewater from causing radiation damage to nature and human society, and also enable the recycling of metallic cobalt. As a scarce metal, cobalt is often a byproduct of other metal ores, and its price has long been high in the market. Therefore, the enrichment, recovery, and removal of cobalt from wastewater has enormous application potential and a broad market.

[0004] Chitosan and sodium alginate, as polysaccharide polymers extracted from nature, have numerous applications in food, medicine, and water treatment. In particular, chitosan, as a cationic polymer, and sodium alginate, as an anionic polymer, can form chitosan / sodium alginate polyelectrolyte materials, which have been extensively studied for the adsorption and capture of heavy metal ions in water, resulting in polyelectrolyte membranes, polyelectrolyte microspheres, and polyelectrolyte fibers. Studies have shown that metal-organic frameworks (MOFs), due to their structural stability and selective adsorption of specific metal ions, are often chosen for composite materials to enhance the structural strength of the substrate and increase the adsorption capacity for heavy metal ions. Existing research includes the preparation of materials that enhance the adsorption performance and structural strength of chitosan or sodium alginate materials by composite ZIF-8 materials. However, no literature reports on the modification of multiple materials through composite composition have been found. Summary of the Invention

[0005] This invention aims to provide a method for preparing a polyelectrolyte adsorption fiber composite organic framework material and its application. The composite material prepared by this method possesses a high porosity structure and high specific surface area. The preparation process is simple, low-cost, and yields high output. All components are renewable materials found in nature, making it environmentally friendly, harmless to the human body, and it will not cause secondary pollution to the environment after degradation. This material is also effective against cobalt metal ions. 2+ It has strong adsorption selectivity and can be used for the recovery and treatment of metallic cobalt in wastewater.

[0006] In this invention, sodium alginate (SA) is widely used in food, medical, and other fields due to its natural, environmentally friendly, and human-friendly properties. As a polysaccharide polymer, it is soluble in water and can be freeze-dried into a sponge-like fibrous structure. This invention uses sodium alginate fiber as a base and adds sodium carboxymethyl cellulose (CMC-Na) to the sodium alginate, which improves the structural strength and porosity of the sodium alginate material after drying. In particular, the addition of CMC-Na to the freeze-dried sodium alginate fiber structure significantly increases the adsorption performance of the polyelectrolyte material formed with chitosan for heavy metal ions. Then, the sodium alginate-sodium carboxymethyl cellulose composite fiber is placed in chitosan (CS). Chitosan, as a cationic polymer, reacts with the sodium alginate-sodium carboxymethyl cellulose composite fiber to form a polyelectrolyte material, namely CS-SA-CMC composite fiber, which exhibits excellent adsorption properties. Furthermore, this invention adds ZIF-90 crystal material to the sodium alginate / sodium carboxymethyl cellulose / chitosan composite polyelectrolyte fiber. The organic ligand of ZIF-90 is imidazole-2-carboxaldehyde (ICA), which improves its selective adsorption of metal ions. This invention combines a metal-organic framework material with a polyelectrolyte fiber material, which enhances the structural stability of the fiber and also allows it to function better in the adsorption of heavy metal ions.

[0007] This invention provides a method for preparing a polyelectrolyte adsorption fiber composite organic framework material, comprising the following steps:

[0008] S1. Sodium alginate and sodium carboxymethyl cellulose are completely dissolved in deionized water, and then completely dispersed by magnetic stirring. The mixture is poured into a mold and freeze-dried to obtain sodium alginate-sodium carboxymethyl cellulose fiber.

[0009] S2. Dissolve calcium chloride in deionized water to a concentration of 10-20 g / L. Stir magnetically to dissolve the calcium chloride completely. Pour the calcium chloride solution into a petri dish and immerse the composite fiber obtained in S1 in it. Press lightly to ensure complete immersion. After complete curing, immerse the fiber in deionized water to wash away excess calcium chloride solution. Repeat this process three times. Finally, remove some excess water by vacuum filtration and freeze dry completely to obtain the cured composite fiber.

[0010] S3. Add methanol and zinc nitrate hexahydrate to a round-necked flask. After dissolving completely by magnetic stirring at a water bath temperature of 60-80℃, add imidazole-2-carboxaldehyde and triethylamine, and reflux for 0.5h~1.5h. After reflux, wash three times each with methanol and deionized water by centrifugation. Finally, place at room temperature until completely dry to obtain ZIF-90 crystal material.

[0011] S4. Prepare an aqueous acetic acid solution and add chitosan material. After the chitosan material is completely dissolved under magnetic stirring, a chitosan solution is formed. Let it stand overnight to eliminate bubbles. Under magnetic stirring at 500-700 rpm / min, add the ZIF-90 crystal material obtained in S3 into the chitosan solution and stir until it is mixed evenly.

[0012] S5. The cured composite fiber obtained in S2 is added to the chitosan solution obtained in S4 at room temperature and gently pressed to ensure complete immersion for 2 hours. After immersion, it is slowly immersed in deionized water to wash away excess chitosan solution. After simple washing, vacuum filtration is used to remove some excess water. After complete freeze-drying again, polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework material is obtained.

[0013] Preferably, the mold in S1 is a porous plastic culture dish with a pore size of 35 mm and a single-pore capacity of 0.38 mL.

[0014] Preferably, the concentration of sodium alginate solution in S1 is 1.5~2.5 g / L, and the mass ratio of sodium carboxymethyl cellulose to sodium alginate is 1~1.5:3.

[0015] Preferably, the magnetic stirring speed in S1 is 800-1000 rpm / min, and the magnetic stirring time is 2-3 hours.

[0016] Preferably, in S2, the magnetic stirring speed is 800-1000 rpm / min, the magnetic stirring time is 0.5-1h, and the soaking time is 2-3h.

[0017] Preferably, the rotation speed of the magnetic stirrer in S3 is 500-700 rpm / min.

[0018] Preferably, the mass ratio of methanol, triethylamine, imidazole-2-carboxaldehyde and zinc nitrate hexahydrate in S3 is 25:0.25:1~1.5:1~1.5.

[0019] Preferably, in the solution described in S4, the acetic acid water content is 1% w / v, the chitosan content in the chitosan solution is 1% w / v, and the mass ratio of chitosan to ZIF-90 material is 1:0.2~0.3.

[0020] Preferably, the magnetic stirring speed for dissolving the chitosan solution in S4 is 800-1000 rpm / min, and the magnetic stirring time is 2-3 hours. After adding ZIF-90 material, the magnetic stirring speed is 500-700 rpm / min, and the magnetic stirring time is 1-2 hours.

[0021] Preferably, in S5, the mass ratio of sodium alginate to chitosan is 1~2:1.

[0022] This invention also provides the application of the prepared polyelectrolyte adsorption fiber composite organic framework material in the removal of Co(II) from wastewater. The application process is as follows: a prepared Co(II) stock solution and background ion solution are added to a centrifuge tube to simulate the relevant polluted environment. The pH value is then adjusted using NaOH and HCl. Finally, the adsorbent material ZIF-90@CS-SA-CMC is added and the mixture is shaken for a certain period to simulate the adsorption process. After the adsorption process is complete, the centrifuge tube is centrifuged, and the supernatant is collected. The concentration of remaining Co(II) ions is determined using a UV spectrophotometer.

[0023] This invention determines the adsorption capacity of ZIF-90@CS-SA-CMC fiber material under different experimental conditions by adjusting different parameters during the experiment, such as pH value, adsorption process time, Co(II) ion concentration, and background ions.

[0024] The beneficial effects of this invention are:

[0025] (1) Chitosan is extracted from crustaceans, and sodium carboxymethyl cellulose is obtained by modifying natural cellulose. The main materials are green, environmentally friendly, renewable, low cost, and high output. After degradation, they will not cause secondary pollution to the environment and are convenient for recycling metals in sewage.

[0026] (2) This invention selects metal-organic framework materials (MOFs) to improve the adsorption performance of polyelectrolyte fibers, using zinc (Zn) as an example. 2+ ZIF-90, with its metal core, can significantly improve its structural strength when combined with polyelectrolyte fiber materials, and its own adsorption selectivity is also brought into play, with high adsorption efficiency for cobalt ions. In addition, ZIF-90 can be further modified to enhance its adsorption effect on other specific pollutants. Attached Figure Description

[0027] Figure 1 This is a SEM image of the polyelectrolyte adsorption fiber composite organic framework material of Embodiment 1 of the present invention.

[0028] Figure 2 This is a SEM image of the polyelectrolyte adsorption fiber composite organic framework material after adsorption of Co(II) in Example 1 of the present invention.

[0029] Figure 3 This is the Fourier transform infrared spectrum of the polyelectrolyte adsorption fiber composite organic framework material of Example 1 of the present invention.

[0030] Figure 4 This is a diagram showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.001 mol / L in Example 4 of the present invention.

[0031] Figure 5 This is a graph showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.01 mol / L in Example 5 of the present invention.

[0032] Figure 6 This is a diagram showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.10 mol / L in Example 6 of the present invention.

[0033] Figure 7 This is a graph showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.001 mol / L Na2SO4 in Example 7 of the present invention.

[0034] Figure 8 This is a graph showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.001 mol / L NaCl in Example 8 of the present invention.

[0035] Figure 9 This is a graph showing the effect of pH on the adsorption of Co(II) on the polyelectrolyte adsorption fiber composite organic framework material when the background ion concentration is 0.001 mol / L NaHCO3 in Example 9 of the present invention.

[0036] Figure 10 This is a graph showing the effect of polyelectrolyte adsorption fiber composite organic framework material on the adsorption of Co(II) at different initial concentrations at 30°C in Example 10 of the present invention.

[0037] Figure 11 This is a graph showing the effect of polyelectrolyte adsorption fiber composite organic framework material on the adsorption of Co(II) at different initial concentrations at 45°C in Example 11 of the present invention.

[0038] Figure 12 This is a graph showing the effect of polyelectrolyte adsorption fiber composite organic framework material on the adsorption of Co(II) at different initial concentrations at 60°C in Example 12 of the present invention.

[0039] Figure 13This is a graph showing the effect of different adsorbent concentrations on the adsorption of Co(II) in Example 13 of the present invention. Detailed Implementation

[0040] The present invention will be further illustrated by the following embodiments, but is not limited to the following embodiments.

[0041] The following section, in conjunction with the accompanying figures, examines the effects of background ions NaNO3 (0.001 mol / L–0.10 mol / L) on the adsorption efficiency of the invention, the effects of different background ions Na2SO4, NaCl, and NaHCO3 at a concentration of 0.001 mol / L on the adsorption efficiency, and the study of Co(II) concentration from 3.39 × 10⁻⁶. -4 mol / L~3.39×10 -3 The invention will be further described in detail in specific embodiments regarding the adsorption effect of the material at mol / L from 30℃ to 60℃. Example 1

[0042] This embodiment provides a method for preparing a polyelectrolyte adsorption fiber composite organic framework material, the method being as follows:

[0043] S1. Sodium alginate and sodium carboxymethyl cellulose were completely dissolved in deionized water. The concentration of the sodium alginate solution was 2.0 g / L. The mass ratio of sodium carboxymethyl cellulose to sodium alginate was 1:3. After stirring magnetically at 1000 rpm / min for 3 hours, the mixture was completely dispersed and poured into a porous plastic petri dish mold with a pore size of 35 mm and a single pore capacity of 0.38 mL. After being completely freeze-dried, the composite adsorption fiber was obtained and named SA-CMC.

[0044] S2. Prepare a 5 w% v calcium chloride solution and stir it magnetically at 1000 rpm / min for 1 h to completely dissolve the calcium chloride. Pour the calcium chloride solution into a petri dish and immerse the composite fiber SA-CMC obtained in S1 in it. Press it slightly to ensure complete immersion. After complete curing for 3 h, immerse it in deionized water to wash away excess calcium chloride solution. Repeat this process three times. Finally, remove some excess water by vacuum filtration and freeze dry completely to obtain the cured composite fiber SA-CMC.

[0045] S3. Add methanol and zinc nitrate hexahydrate to a round-neck flask. After dissolving completely by magnetic stirring at 700 rpm / min in a 75°C water bath, add methanol, triethylamine, imidazole-2-carboxaldehyde and zinc nitrate hexahydrate in a mass ratio of 25:0.25:1:1.55 and reflux for 1 hour. After reflux, wash three times each with methanol and deionized water by centrifugation. Finally, place at room temperature until completely dry to obtain ZIF-90 crystal material.

[0046] S4. Prepare a 1% w / v acetic acid aqueous solution and add 1% chitosan by mass. After complete dissolution by magnetic stirring at 1000 rpm / min for 3 hours, a 1% w / v chitosan solution is obtained. Let it stand overnight to eliminate bubbles. Add ZIF-90 crystal material to the solution and stir for 1.5 hours until it is mixed evenly under magnetic stirring at 700 rpm / min. The mass ratio of chitosan to ZIF-90 crystal material is 1:0.3 to obtain a ZIF-90@CS mixed solution.

[0047] S5. The cured composite fiber SA-CMC obtained in S2 was added to the ZIF-90@CS mixed solution obtained in S4 at room temperature, and gently pressed to ensure complete immersion for 2 hours. The mass ratio of sodium alginate in the fiber in S2, chitosan in the solution in S4, and ZIF-90 crystals added in S4 was 1:1:0.3. After immersion, the fiber was slowly immersed in deionized water to wash away excess chitosan solution. After simple washing, some excess water was removed by vacuum filtration. After complete freeze-drying again, the polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework was obtained and named ZIF-90@CS-SA-CMC.

[0048] The morphology of the obtained ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework material was characterized by SEM as follows: Figure 1 As shown, the left and right images are scanning electron microscope images at 1 μm and 500 nm, respectively. (Through...) Figure 1 Irregular three-dimensional particle protrusions were observed in the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework material, which are ZIF-90 crystal structures on the composite, indicating that it is completely composited onto the fiber; the SEM morphology characterization results of the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material after Co adsorption are as follows. Figure 2 As shown, the original granular protrusions are covered by agglomeration, indicating that the material has good adsorption properties.

[0049] Figure 3 Fourier transform infrared spectra of the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material, the ZIF-90 crystalline material, and the CS-SA-CMC composite fiber material obtained in step S2 without ZIF-90 doping. Approximately 1545 cm⁻¹ -1 ~1567 cm -1 The -NH2 characteristic peak at the position is carried by the acetylamino group on chitosan. When combined with the COO- group on sodium alginate / sodium carboxymethyl cellulose, the resulting polyelectrolyte material significantly compresses this characteristic peak, thus allowing it to be observed from... Figure 3The characteristic peak is noticeably shorter, indicating that it has been successfully composited into a polyelectrolyte material. Furthermore, due to electrostatic attraction during the composite process, its 3250 cm⁻¹ peak... -1 ~3260 cm -1 The characteristic peaks of -OH and -NH2 at the site are significantly shifted and their hydrogen bonds are shortened, further demonstrating the success of the composite. Furthermore, the curing of the SA-CMC composite fiber in sodium chloride solution leads to a reduction in its 2920 cm⁻¹ length. -1 ~2930cm -1 The absorption peak at this point weakens, indicating that the Na on its COO- is... + by Ca 2+ The replacement was successful, and the material was thus cured.

[0050] The Fourier transform infrared spectrum of the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material conforms to the infrared spectrum of ZIF-90 crystals. The vibrational absorption peak of the carbonyl C=O group in the organic ligand imidazole-2-carboxaldehyde in ZIF-90 crystals is at 1660 cm⁻¹. -1 ~1670 cm -1 At 1160 cm⁻¹, and imidazole-2-carboxaldehyde at 1160 cm⁻¹ -1 ~1170 cm -1 950 cm -1 ~960 cm -1 The cyano absorption peak C=N at this point is shifted by Zn-N and becomes a carbon-nitrogen bond absorption peak CN. Furthermore, Zn-N affects its absorption peak at 530 cm⁻¹. -1 ~540cm -1 Based on the absorption peaks observed, it can be concluded that ZIF-90 crystals were successfully prepared and composited onto ZIF-90@CS-SA-CMC composite fibers.

[0051] In summary, the preparation of ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material is successful.

[0052] In this embodiment, to provide sufficient mechanical strength of the adsorbent, sodium alginate-carboxymethyl cellulose sodium cured with calcium chloride was selected as the structural substrate. ZIF-90 crystals were loaded during the polyelectrolytic composite process with chitosan solution. The resulting polyelectrolyte adsorption fiber composite organic framework material exhibits strong adsorption capacity, good affinity to humans, easy recycling, and environmental friendliness. The excellent ion selectivity and stable structure of ZIF-90 crystals further enhance the structural stability of the composite fiber material in wastewater environments and increase its selective adsorption capacity for specific ions. Furthermore, ZIF-90 material can undergo multi-functional group composite formation, further enhancing the adsorption of specific pollutants. Therefore, in summary, the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material is not only low-cost and environmentally friendly, but also green and pollution-free from a recycling perspective. The materials are all renewable resources, capable of handling complex wastewater treatment environments, and are biodegradable biological materials that will not cause secondary pollution. This fully demonstrates its excellent performance and unique advantages, indicating a broad prospect in the field of industrial wastewater treatment. Example 2

[0053] This embodiment provides a method for preparing a polyelectrolyte adsorption fiber composite organic framework material, the method being as follows:

[0054] S1. Sodium alginate and sodium carboxymethyl cellulose were completely dissolved in deionized water. The concentration of the sodium alginate solution was 1.0 g / L. The mass ratio of sodium carboxymethyl cellulose to sodium alginate was 1.5:3. After stirring magnetically at 1000 rpm / min for 3 hours, the mixture was completely dispersed and poured into a porous plastic petri dish mold with a pore size of 35 mm and a single pore capacity of 0.38 mL. After being completely freeze-dried, the composite adsorption fiber was obtained and named SA-CMC.

[0055] S2. Dissolve 4 g of calcium chloride in 200 mL of deionized water and stir magnetically at 1000 rpm / min for 1 hour. Pour the calcium chloride solution into a petri dish and immerse the composite fiber SA-CMC obtained in S1 in it. Press lightly to ensure complete immersion. After complete curing for 3 hours, immerse in deionized water to wash away excess calcium chloride solution. Repeat this process three times. Finally, remove some excess water by vacuum filtration and freeze dry completely to obtain the cured composite fiber SA-CMC.

[0056] S3. Add methanol and zinc nitrate hexahydrate to a round-neck flask. After completely dissolving the mixture by magnetic stirring at 700 rpm / min in a 75°C water bath, add methanol, triethylamine, imidazole-2-carboxaldehyde and zinc nitrate hexahydrate in a mass ratio of 25:0.25:1:1.55 and reflux for 1 hour. After reflux, wash the mixture three times each with methanol and deionized water by centrifugation. Finally, place the mixture at room temperature until completely dry to obtain ZIF-90 crystal material.

[0057] S4. Prepare a 1% w / v acetic acid aqueous solution and add 1% chitosan by mass. After complete dissolution by magnetic stirring at 1000 rpm / min for 3 hours, a 1% w / v chitosan solution is obtained. Let it stand overnight to eliminate bubbles. Add ZIF-90 crystal material to the solution and stir for 1.5 hours until it is mixed evenly under magnetic stirring at 700 rpm / min. The mass ratio of chitosan to ZIF-90 material is 1:0.3 to obtain a ZIF-90@CS mixed solution.

[0058] S5. The cured composite fiber SA-CMC obtained in S2 is added to the ZIF-90@CS mixed solution obtained in S4 at room temperature. The solution is gently pressed to ensure complete immersion for 2 hours. After immersion, it is slowly immersed in deionized water to wash away excess chitosan solution. After simple washing, vacuum filtration is used to remove some excess water. After complete freeze-drying again, the polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework material is obtained and named ZIF-90@CS-SA-CMC. The mass ratio of sodium alginate in S2 fiber, chitosan in S4 solution, and ZIF-90 crystals added in S4 is 0.5:1:0.3.

[0059] Compared to the ZIF-90@CS-SA-CMC composite fiber in Implementation Case 1, when the concentration of sodium alginate solution is 1.0 g / L, its structure after freeze-drying is relatively loose, its density is low, and the overall material lacks stability. The resulting fiber material is prone to overall structural breakage and decomposition in centrifuge tubes after the shaking adsorption process, making it impossible to conduct subsequent adsorption process-related experiments. Example 3

[0060] This embodiment provides a method for preparing a polyelectrolyte adsorption fiber composite organic framework material, the method being as follows:

[0061] S1. Sodium alginate and sodium carboxymethyl cellulose were completely dissolved in deionized water. The concentration of the sodium alginate solution was 2.0 g / L. The mass ratio of sodium carboxymethyl cellulose to sodium alginate was 1:3. After stirring magnetically at 1000 rpm / min for 3 hours, the mixture was completely dispersed and poured into a porous plastic petri dish mold with a pore size of 35 mm and a single pore capacity of 0.38 mL. After being completely freeze-dried, the composite adsorption fiber was obtained and named SA-CMC.

[0062] S2. Dissolve 4 g of calcium chloride in 200 mL of deionized water and stir magnetically at 1000 rpm / min for 1 hour. Pour the calcium chloride solution into a petri dish and immerse the composite fiber SA-CMC obtained in S1 in it. Press lightly to ensure complete immersion. After complete curing for 3 hours, immerse in deionized water to wash away excess calcium chloride solution. Repeat this process three times. Finally, remove some excess water by vacuum filtration and freeze dry completely to obtain the cured composite fiber SA-CMC.

[0063] S3. Add methanol and zinc nitrate hexahydrate to a round-neck flask. After completely dissolving the mixture by magnetic stirring at 700 rpm / min in a 75°C water bath, add methanol, triethylamine, imidazole-2-carboxaldehyde and zinc nitrate hexahydrate in a mass ratio of 25:0.25:1:1.55 and reflux for 1 hour. After reflux, wash the mixture three times each with methanol and deionized water by centrifugation. Finally, place the mixture at room temperature until completely dry to obtain ZIF-90 crystal material.

[0064] S4. Prepare a 1% w / v acetic acid aqueous solution and add 1% chitosan by mass. After complete dissolution by magnetic stirring at 1000 rpm / min for 3 hours, a 1% w / v chitosan solution is obtained. Let it stand overnight to eliminate bubbles. Add ZIF-90 crystal material to the solution and stir for 1.5 hours until it is mixed evenly under magnetic stirring at 700 rpm / min. The mass ratio of chitosan to ZIF-90 material is 1:0.2 to obtain a ZIF-90@CS mixed solution.

[0065] S5. The cured composite fiber SA-CMC obtained in S2 is added to the ZIF-90@CS mixed solution obtained in S4 at room temperature. The solution is gently pressed to ensure complete immersion for 2 hours. After immersion, it is slowly immersed in deionized water to wash away excess chitosan solution. After simple washing, vacuum filtration is used to remove some excess water. After complete freeze-drying again, the polyelectrolyte adsorption fiber composite organic framework material loaded with metal-organic framework material is obtained and named ZIF-90@CS-SA-CMC. The mass ratio of sodium alginate in S2 fiber, chitosan in S4 solution, and ZIF-90 crystals added in S4 is 1:1:0.2.

[0066] Compared to the ZIF-90@CS-SA-CMC composite fiber in Example 1, the mass ratio of ZIF-90 crystals added to the S4 solution was less than that in Example 1. This resulted in a fragile fiber material structure in the final S5, with the pores of the fiber material prone to collapse and the overall structure unstable. Therefore, subsequent adsorption experiments were abandoned. Example 4

[0067] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4 The adsorption rate of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 was studied under different pH values ​​under the conditions of NaNO3 with a background ion concentration of 0.001 mol / L and a background ion concentration of 0.001 mol / L.

[0068] Experimental results are as follows Figure 4 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is lowest at pH 2, highest at pH 3-4, and stabilizes between pH 5-9 with increasing pH, decreasing further above pH 9. This may be because the surface of ZIF-90@CS-SA-CMC is a chitosan-sodium alginate / sodium carboxymethyl cellulose polyelectrolyte. Under excessively acidic conditions, the chitosan on the surface dissolves, thus disrupting the structure of the polyelectrolyte and affecting its adsorption performance. With increasing pH, in a slightly acidic environment, the carboxyl groups on sodium alginate molecules are more easily ionized, carrying a negative charge, which allows for better adsorption and binding of Co(II). Since the amino groups on chitosan also ionize in a slightly acidic environment, the polyelectrolyte formed with sodium alginate-sodium carboxymethyl cellulose can adsorb better. Above pH 9, Co(II) forms relatively more complexes, reducing the number of ions in the solution and making them more difficult to capture by the adsorption sites on the material. Example 5

[0069] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4 The adsorption rate of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 was studied under different pH values ​​under the conditions of NaNO3 with a background ion concentration of 0.01 mol / L and a background ion concentration of 0.01 mol / L.

[0070] If the experimental results are Figure 5 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is lowest at pH 2, rises to a maximum of 54% at pH 3-4, and remains stable at about 30%-40% between pH 5-9 as pH increases, and is below 30% when pH exceeds 9. Example 6

[0071] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4The adsorption rate of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 was studied under different pH values ​​under the conditions of NaNO3 with background ions of 0.1 mol / L and mol / L mol / L mol / L.

[0072] Experimental results are as follows Figure 6 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is lowest at pH 2, rises to a maximum of 49% at pH 3-4, and tends to stabilize at pH 5-9 with increasing pH, with an adsorption rate of about 20%-30%, and is lower than 20% at pH above 9.

[0073] Analysis of adsorption efficiency under different ion backgrounds and pH changes shows that the adsorption rate is lowest below pH 3, highest between pH 3 and 4, stable between pH 4 and 9, and gradually decreases above pH 9. The influence of ion background is also significant; the ion influence is lowest at a background of 0.001 mol / L, with the highest adsorption rate of approximately 60%, while the ion influence is highest at a background of 0.10 mol / L, with a maximum adsorption rate of only 49%. Example 7

[0074] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4 The effect of Co(II) on the adsorption rate of the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 under different background ion conditions was investigated under the conditions of Na2SO4 with a background ion concentration of 0.001 mol / L.

[0075] Experimental results are as follows Figure 7 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is the lowest at pH below 3, about 12%, and rises to the highest of 44% at pH 3-4. As the pH increases, it tends to stabilize at 5-9, with an adsorption rate of 30%-40%, and the adsorption rate is less than 30% when the pH exceeds 9. Example 8

[0076] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4 The effect of Co(II) adsorption rate on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 under different background ion conditions was investigated.

[0077] Experimental results are as follows Figure 8 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is as low as about 10% when the pH is below 3, rises to a maximum of 47% when the pH is 3 to 4, and tends to stabilize at 5 to 9 as the pH increases, with an adsorption rate of 35% to 45%, and is less than 30% when the pH is above 9. Example 9

[0078] In this embodiment, the temperature was 30°C, the adsorbent concentration was 0.50 g / L, and the Co(II) concentration was 5.09 × 10⁻⁶. -4 The effect of Co(II) on the adsorption rate of the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 under different background ion conditions was investigated under the conditions of NaHCO3 with a background ion concentration of 0.001 mol / L.

[0079] Experimental results are as follows Figure 9 As shown, the adsorption rate of Co(II) by ZIF-90@CS-SA-CMC is the lowest at pH below 3, about 8%, and rises to the highest of 44% at pH 3-4. As the pH increases, it tends to stabilize at pH 5-9, with an adsorption rate of 25%-35%, and the adsorption rate is less than 25% when the pH exceeds 9.

[0080] In summary, the effects of different ion backgrounds on adsorption varied considerably, especially under NaHCO3 conditions, where the average adsorption rate was the lowest, with a stable adsorption rate of less than 35% at pH 5–9. This is likely due to the presence of bicarbonate ions (HCO3-). - It readily combines with cobalt ions in solution to form bicarbonate or carbonate products, making it difficult for materials to bind to their adsorption sites. This reduces the number of free cobalt ions in solution, making it even more difficult for adsorption sites to complex and adsorb. In a relatively alkaline environment, related bicarbonate or carbonate precipitates will appear, blocking the pores and reducing the adsorption rate. Example 10

[0081] This example investigates the effect of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1, under the conditions of 30°C, adsorbent concentration of 0.50 g / L, solution pH=4.0, and background ion concentration of 0.001 mol / L NaNO3. The study focuses on the effect of Co(II) concentration decreasing from 3.39 × 10⁻⁶ g / L. -4 mol / L to 3.39×10 -3 Effect of different initial concentrations (mol / L) on the adsorption of Co(II);

[0082] Experimental results are as follows Figure 10As shown, the adsorption process is relatively gradual, with the initial concentration varying from low to high, and the lowest initial concentration being 3.39 × 10⁻⁶. -4 The highest initial concentration was 3.39 × 10 mol / L. -3 mol / L. Wherein, C e and q e These represent the concentration of remaining metal ions at equilibrium and the adsorption capacity, respectively. The adsorption rate is low at the initial lowest concentration, with an adsorption capacity of approximately 2.42 × 10⁻⁶. -4 The adsorption capacity gradually increased with increasing concentration, reaching a maximum of approximately 2.88 × 10⁻⁶ mol / g. -3 The reason why it can maintain a good adsorption rate at a high initial concentration of Co(II) is attributed to the stronger ion driving force of high concentration of Co(II) until adsorption equilibrium is reached. Example 11

[0083] This example investigates the effect of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1, under the conditions of 45℃, adsorbent concentration of 0.50 g / L, solution pH=4.0, and background ion concentration of 0.001 mol / L NaNO3. The study focuses on the effect of Co(II) concentration decreasing from 3.39 × 10⁻⁶ g / L. -4 mol / L to 3.39×10 -3 Effect of different initial concentrations (mol / L) on the adsorption of Co(II);

[0084] Experimental results are as follows Figure 11 As shown, the adsorption process is relatively gradual, with the initial concentration varying from low to high, and the lowest initial concentration being 3.39 × 10⁻⁶. -4 The highest initial concentration was 3.39 × 10 mol / L. -3 mol / L. Wherein, C e and q e These represent the concentration of remaining metal ions at equilibrium and the adsorption capacity, respectively. The adsorption rate is low at the initial lowest concentration, with an adsorption capacity of approximately 3.66 × 10⁻⁶. -4 The adsorption capacity gradually increased with increasing concentration, reaching a maximum of approximately 3.68 × 10⁻⁶ mol / g. -3 The reason why it can maintain a good adsorption rate at a high initial concentration of Co(II) is attributed to the stronger ion driving force of high concentration of Co(II) until adsorption equilibrium is reached. Example 12

[0085] This example investigates the effect of Co(II) on the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1, under the conditions of 60℃, adsorbent concentration of 0.50 g / L, solution pH=4.0, and background ion concentration of 0.001 mol / L NaNO3. The study focuses on the effect of Co(II) concentration decreasing from 3.39 × 10⁻⁶ g / L. -4 mol / L to 3.39×10 -3 Effect of different initial concentrations (mol / L) on the adsorption of Co(II);

[0086] Experimental results are as follows Figure 12 As shown, the adsorption process is relatively gradual, with the initial concentration varying from low to high, and the lowest initial concentration being 3.39 × 10⁻⁶. -4 The highest initial concentration was 3.39 × 10 mol / L. -3 mol / L. Wherein, C e and q e These represent the concentration of remaining metal ions at equilibrium and the adsorption capacity, respectively. The adsorption rate is low at the initial lowest concentration, with an adsorption capacity of approximately 4.10 × 10⁻⁶. -4 The adsorption capacity gradually increased with increasing concentration, reaching a maximum of approximately 4.52 × 10⁻⁶ mol / g. -3 As can be seen from the mol / g, the adsorption capacity increases with increasing experimental temperature. The increase is smaller at lower initial concentrations and more significant at higher initial concentrations, from 2.88 × 10⁻⁶ mol / g at 30℃. -3 The mol / g was increased to 4.52 × 10⁻⁶ at 60 °C. -3 mol / g. Example 13

[0087] This example studies the removal rate of Co(II) in the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 under different adsorbent concentrations, at a temperature of 30°C, a solution pH of 4.0, and a background ion concentration of 0.001 mol / L NaNO3.

[0088] from Figure 13 It can be observed that as the adsorbent concentration increases, the adsorption rate of ZIF-90@CS-SA-CMC material also increases. When the content of ZIF-90@CS-SA-CMC is 0.66 g / L, the removal rate can reach 50%, indicating that the high porosity and abundant adsorption sites of ZIF-90@CS-SA-CMC material can provide a huge advantage.

[0089] In summary, the ZIF-90@CS-SA-CMC polyelectrolyte adsorption fiber composite organic framework material prepared in Example 1 has a fine microstructure, providing a large adsorption capacity and contact surface area. The substrate material is green, environmentally friendly, and inexpensive, being renewable and extracted from nature. It can efficiently recover pollutants and effectively recover metals such as cobalt. The treatment of its adsorption material is also quick and efficient, without causing secondary pollution to the environment. Furthermore, combining it with different metal-organic framework materials can enhance the selective adsorption of different pollutants, making it suitable for wastewater treatment in complex environments.

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for the preparation of a polyelectrolyte adsorbing fiber composite organic framework material, characterized in that The method comprises the following steps: S1, completely melt sodium alginate and sodium carboxymethyl cellulose into deionized water, and make them completely dispersed by magnetic stirring, pour into a mold and completely freeze dry to obtain sodium alginate-sodium carboxymethyl cellulose fibers; the concentration of the sodium alginate solution is 1.5-2.5 g / L, and the mass ratio of sodium carboxymethyl cellulose to sodium alginate is 1-1.5:3; S2, prepare a solution with a concentration of 10-20 g / L by putting calcium chloride into deionized water, and make it completely dissolved under magnetic stirring, pour the calcium chloride solution into a culture dish, and immerse the composite fibers obtained in S1 into the culture dish, and slightly press to ensure complete immersion, after complete solidification, immerse into deionized water to wash away the excess calcium chloride solution, and repeat three times, finally, remove part of the excess water by vacuum filtration and completely freeze dry to obtain the solidified composite fibers; S3, add methanol, zinc nitrate hexahydrate into a round-neck flask, completely dissolve under magnetic stirring at a water bath temperature of 60-80℃, then add imidazole-2-formaldehyde and triethylamine, and keep refluxing for 0.5-1.5 h, after the refluxing is completed, centrifugally wash with methanol and deionized water for three times, finally, put into room temperature until completely dry, to obtain ZIF-90 crystal material; the mass ratio of methanol, triethylamine, imidazole-2-formaldehyde and zinc nitrate hexahydrate is 25:0.25:1-1.5:1-1.5; S4, prepare an acetic acid aqueous solution, and add chitosan material to completely dissolve under magnetic stirring to form a chitosan solution, stand overnight to eliminate bubbles, and put the ZIF-90 crystal material obtained in S3 into the chitosan solution under magnetic stirring at 500-700 rpm / min to stir until mixed uniformly; S5, immerse the solidified composite fibers obtained in S2 into the chitosan solution obtained in S4 under room temperature, slightly press to ensure complete immersion for 2 h, after the immersion is completed, slowly immerse into deionized water to wash away the excess chitosan solution, after simple washing, remove part of the excess water by vacuum filtration, and completely freeze dry again to obtain a polyelectrolyte adsorption fiber composite organic framework material.

2. The method for preparing the polyelectrolyte adsorption fiber composite organic framework material according to claim 1, characterized in that: The mold in S1 is a porous plastic culture dish with a pore size of 35 mm and a single-hole capacity of 0.38 mL; the magnetic stirring speed is 800-1000 rpm / min, and the magnetic stirring time is 2-3 h.

3. The method for preparing the polyelectrolyte adsorption fiber composite organic framework material according to claim 1, characterized in that: The magnetic stirring speed in S2 is 800-1000 rpm / min, the magnetic stirring time is 0.5-1 h, and the immersion time is 2-3 h.

4. The method for preparing the polyelectrolyte adsorption fiber composite organic framework material according to claim 1, characterized in that: The magnetic stirring speed in S3 is 500-700 rpm / min.

5. The method for preparing the polyelectrolyte adsorption fiber composite organic framework material according to claim 1, characterized in that: In the acetic acid aqueous solution of S4, the ratio of acetic acid to water is 1% w / v, the chitosan in the chitosan solution is 1% w / v, and the mass ratio of chitosan to ZIF-90 material is 1:0.2-0.3; the magnetic stirring speed for dissolving the chitosan solution is 800-1000 rpm / min, the magnetic stirring time is 2-3 h, the magnetic stirring speed after adding the ZIF-90 material is 500-700 rpm / min, and the magnetic stirring time is 1-2 h.

6. The method for preparing the polyelectrolyte adsorption fiber composite organic framework material according to claim 1, characterized in that: In S5, the mass ratio of sodium alginate to chitosan is 1-2:

1.

7. The polyelectrolyte adsorbing fiber composite organic framework material prepared by the preparation method of any one of claims 1-6.

8. The polyelectrolyte adsorbing fiber composite organic framework material of claim 7 is applied to remove Co(II) in wastewater.

9. Use according to claim 8, characterized in that: The related pollution environment is simulated by adding the prepared Co(II) stock solution and background ion solution into a centrifuge tube, adjusting the pH value by NaOH and HCl, and finally putting the polyelectrolyte adsorbing fiber composite organic framework material into the centrifuge tube for oscillation adsorption for 3-4 h to complete the adsorption process. After the centrifugation of the centrifuge tube after the adsorption process, the supernatant is taken, and the remaining Co(II) ion concentration is determined by a UV spectrophotometer.

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