A highly selective adsorbent and a method for its preparation

Abstract

The application discloses a kind of high-efficiency selective adsorbents and preparation method thereof, belong to adsorbent separation technical field.The preparation of three-dimensional porous adsorbent of the application includes: tannic acid and metal salt are dissolved in acetic acid solution and are reacted, reaction precipitate is collected, and product A is obtained;Methyl methacrylated sodium alginate, calcium carbonate and LAP initiator are dispersed in water and mixed uniformly, and product B is obtained;Then product A and product B are mixed uniformly and injected into syringe, and are connected to 3D printer feeding outer shaft;Calcium chloride is dissolved in water and injected into syringe, and is connected to 3D printer feeding inner shaft;Three-dimensional hollow adsorbent is printed by coaxial printing nozzle and extrusion type 3D printer, and then is crosslinked by ultraviolet, soaked in acetic acid solution, and three-dimensional porous adsorbent is obtained;The adsorbent has high selectivity to metal ions, high adsorption efficiency and good recycling performance, and can be widely used in removal of heavy metal ions in contaminated wastewater.

Description

Technical Field

[0001] This invention relates to a highly efficient selective adsorbent and its preparation method, belonging to the field of adsorbent separation technology. Background Technology

[0002] Heavy metal ions in water pose a serious threat to human society, and pollution problems have attracted much attention. Developing highly efficient, selective, and long-term recyclable adsorbents is of great significance for purifying the aquatic environment. Currently, biomaterial-based hydrogels are used to adsorb heavy metal ions in water, but they still suffer from drawbacks such as limited adsorption sites and low ion diffusion rates, which affect adsorption efficiency.

[0003] Organometallic frameworks (MOFs) possess advantages such as large specific surface area, customizable functional groups, ordered and tunable pore structure, simple synthesis processes, and stable yields, making them highly promising for applications in gas adsorption and separation, seawater desalination, solid-state hydrogen storage, and fuel cells. Currently, solvothermal processes for synthesizing MOFs require toxic and flammable organic solvents. Green, energy-saving, and environmentally friendly water-based MOF synthesis methods can promote the commercialization of safe and environmentally friendly synthesis processes, which is crucial for shifting MOF applications from laboratory-scale research to industrial applications.

[0004] Tannic acid, as the second most abundant natural polyphenol after lignin, possesses biocompatibility and holds immense application potential. Considering that tannic acid has aromatic rings with multiple phenolic functional groups, it is a major source of rigid molecules and can serve as a rigid spacer between cations, contributing to the formation of a porous framework. Furthermore, tannic acid is rich in carboxylic acid functional groups, which can chelate with metal cations through coordination to generate strong five-membered rings, achieving selective adsorption of heavy metal ions. However, the adsorption materials prepared by existing technologies have simple structures, which are not conducive to the efficient removal of target analytes. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, this invention provides a method for preparing highly selective adsorbents by forming MOFs using a green water-based method and combining it with coaxial 3D printing technology. The adsorbent prepared by this method has high adsorption efficiency and selectivity for metal ions, and also has good recycling performance, making it widely applicable to water environment purification.

[0006] The first objective of this invention is to provide a method for preparing a highly efficient and selective three-dimensional porous adsorbent, the method comprising the following steps:

[0007] (1) Dissolve tannic acid and metal salt in acetic acid solution, sonicate at room temperature and normal pressure, centrifuge after the reaction, collect the precipitate, dry it, and obtain product A;

[0008] (2) methyl methacrylate sodium alginate, calcium carbonate and LAP initiator are dispersed in water to obtain product B;

[0009] (3) product A and product B are mixed to obtain mixture C, which is injected into a syringe and connected to the outer shaft of the 3D printer feeding; calcium chloride is dissolved in water to obtain solution D, which is injected into a syringe and connected to the inner shaft of the 3D printer feeding; a three-dimensional hollow adsorbent is printed by a coaxial printing nozzle and an extrusion type 3D printer;

[0010] (4) the three-dimensional hollow adsorbent printed in step (3) is ultraviolet crosslinked, then placed in an acetic acid solution and shaken to dissolve the solid calcium carbonate in the adsorbent, to obtain a three-dimensional hollow adsorbent with a microporous structure, which is washed and dried to obtain a three-dimensional porous adsorbent.

[0011] In an embodiment, the metal salt in step (1) is any one of bismuth acetate, ferric chloride or terbium chloride.

[0012] In an embodiment, the molar ratio of tannin acid to metal salt in step (1) is 2:1 to 1:2; preferably 1:2.

[0013] In an embodiment, the acetic acid solution in step (1) is an aqueous acetic acid solution with a volume fraction of 4-6%.

[0014] In an embodiment, the ultrasonic reaction conditions in step (1) are: first ultrasonic at a power of 25-40 kHz for 20-40 min, and then react at 40-70 ℃ for 18-24 h.

[0015] In an embodiment, the centrifugation conditions in step (1) are: 8000-10000 rpm for 10-15 min.

[0016] In an embodiment, the drying temperature in step (1) is 40-80 ℃.

[0017] In an embodiment, the mass concentration of methyl methacrylate sodium alginate in product B in step (2) is 4-6%, the mass concentration of calcium carbonate is 2-3%, and the mass concentration of LAP initiator is 0.5-1.0%.

[0018] In an embodiment, the mass concentration of product A in mixture C in step (3) is 10-15%.

[0019] In an embodiment, the mass concentration of solution D in step (3) is 1-3%.

[0020] In an embodiment, the ultraviolet crosslinking time in step (4) is 20-40 min.

[0021] In an embodiment, the step (4) is printing the three-dimensional hollow adsorbent by the extrusion 3D printer, specifically printing the mixture C and the solution D into a filament of hollow structure by a coaxial printing nozzle, and preparing the three-dimensional hollow adsorbent by layer-by-layer stacking.

[0022] In an embodiment, the step (4) is washing by using distilled water to remove the excess acetic acid on the surface of the adsorbent.

[0023] In an embodiment, the step (4) is drying under the condition of a vacuum degree of 0.02-0.04 Pa and a temperature of-20℃ to-40℃.

[0024] The second object of the present application provides a three-dimensional porous adsorbent obtained by the preparation method described above.

[0025] The third object of the present application provides an application of the three-dimensional porous adsorbent described above in water treatment.

[0026] The fourth object of the present application provides a method for improving the removal rate of copper ions in wastewater, which is using the three-dimensional porous adsorbent described above for the removal of copper ions in wastewater.

[0027] In an embodiment, the pH value of the contaminated wastewater is 4.0-5.0.

[0028] The beneficial effects of the present application are as follows:

[0029] (1) The present application uses tannic acid as a natural raw material, and prepares MOF by using a green, energy-saving and environmentally friendly water-based synthesis method. Compared with the traditional method with high energy consumption and using organic solvents, the present application does not pollute the environment, and has the effect of fully and reasonably utilizing environmental resources. By adjusting the ligand functional group and the metal center, the present application develops a MOF material with high selective adsorption effect on metal ions in water. At the same time, by combining coaxial 3D printing technology and a post-removal method of calcium carbonate, the present application prepares a three-dimensional adsorbent with a multi-level porous structure, which can solve the problem of low adsorption efficiency of heavy metal ions. Compared with the traditional solid block adsorbent, the excellent performance of the present application is enhanced compared with the original.

[0030] (2) The present application uses light-crosslinkable sodium alginate to prepare an adsorbent with higher chemical and mechanical stability, which can be reused without damaging the physicochemical structure of the adsorbent, further improving the performance of natural high molecular materials in wastewater treatment. The preparation process is simple and practical, and can provide good economic benefits. The raw materials are safe and harmless, and environmentally friendly. DETAILED DESCRIPTION

[0031] The following describes preferred embodiments of the present application, and it should be understood that the embodiments are for better explaining the present application and are not intended to limit the present application.

[0032] The tannic acid used in the present application has a molecular weight of 1701 Da; the sodium alginate has a molecular weight of 50-100 kDa.

[0033] Example 1

[0034] A method for preparing a high-efficiency selective three-dimensional porous adsorbent, specifically comprising the following steps:

[0035] (1) Dissolve 0.5 mmol of tannic acid and 1 mmol of bismuth acetate in 30 mL of an acetic acid solution (6 vol. % acetic acid), ultrasonic (37 kHz) at room temperature and normal pressure for 30 min, centrifuge at 8000 rpm for 10 min after reacting at 60 ℃ for 24 hours, collect the precipitate, and dry in a 60 ℃ oven to obtain product A;

[0036] (2) Disperse methylacrylated sodium alginate (4 wt%), calcium carbonate (2 wt%), and LAP initiator (0.5 wt%) in water, mix well to obtain product B;

[0037] (3) Mix product A and product B well to obtain mixture C, wherein the final concentration of product A in mixture C is 10 wt%, inject into a syringe, and connect to the outer shaft of the 3D printer feeding;

[0038] (4) Dissolve calcium chloride in water to obtain a 2 wt% solution D, and inject solution D into a syringe, and connect to the inner shaft of the 3D printer feeding;

[0039] (5) Customize a coaxial printing nozzle (17 / 22G), and use an extrusion type 3D printer to print a filament with a hollow structure using the two different materials of step (3) and step (4), and prepare a three-dimensional hollow adsorbent by layer-by-layer stacking;

[0040] (6) UV crosslink the three-dimensional hollow adsorbent obtained in step (5) for 30 min, then place it in an acetic acid solution (6 vol. %), and shake for 10 min to dissolve the solid calcium carbonate in the adsorbent, thereby introducing a microporous structure into the three-dimensional hollow adsorbent; then wash it in distilled water for 3 times to remove excess acetic acid on the surface, and vacuum freeze-dry (-40 ℃, vacuum degree 0.02 Pa) to obtain a three-dimensional porous adsorbent.

[0041] Example 2

[0042] A method for preparing a high-efficiency selective three-dimensional porous adsorbent, specifically comprising the following steps:

[0043] (1) 0.5 mmol tannic acid and 1 mmol ferric chloride were dissolved in 30 mL acetic acid solution (6 vol. % acetic acid), ultrasonic (37 kHz) for 30 min at room temperature and normal pressure, centrifuged at 8000 rpm for 10 min after reaction at 60 ℃ for 24 hours, and the precipitate was collected and dried in a 60 ℃ oven to obtain product A;

[0044] (2) Methylacrylated sodium alginate (4 wt%), calcium carbonate (2 wt%) and LAP initiator (0.5 wt%) were dispersed in water and uniformly mixed to obtain product B;

[0045] (3) Product A was uniformly mixed with product B to obtain mixture C, wherein the final concentration of product A in mixture C was 10 wt%, and mixture C was injected into a syringe and connected to the outer shaft of the 3D printer;

[0046] (4) Calcium chloride was dissolved in water to obtain a 2 wt% solution D, and solution D was injected into a syringe and connected to the inner shaft of the 3D printer;

[0047] (5) A coaxial printing nozzle (17 / 22G) was customized, and a filament with a hollow structure was printed using an extrusion type 3D printer using two different materials of step (3) and step (4), and a three-dimensional hollow adsorbent was prepared by layer-by-layer stacking;

[0048] (6) The three-dimensional hollow adsorbent obtained in step (5) was subjected to ultraviolet crosslinking for 30 min, and then placed in an acetic acid solution (6 vol. %) and shaken for 10 min to dissolve the solid calcium carbonate in the adsorbent, thereby introducing a microporous structure into the three-dimensional hollow adsorbent; then washed with distilled water for 3 times to remove excess acetic acid on the surface, and vacuum freeze-dried (-40 ℃, vacuum degree 0.02 Pa) to obtain a three-dimensional porous adsorbent.

[0049] Example 3

[0050] A method for preparing a high-efficiency selective three-dimensional porous adsorbent, specifically comprising the following steps:

[0051] (1) 0.5 mmol tannic acid and 1 mmol terbium chloride were dissolved in 30 mL acetic acid solution (6 vol. % acetic acid), ultrasonic (37 kHz) for 30 min at room temperature and normal pressure, centrifuged at 8000 rpm for 10 min after reaction at 60 ℃ for 24 hours, and the precipitate was collected and dried in a 60 ℃ oven to obtain product A;

[0052] (2) Methylacrylated sodium alginate (4 wt%), calcium carbonate (2 wt%) and LAP initiator (0.5 wt%) were dispersed in water and uniformly mixed to obtain product B;

[0053] (3) Mix product A and product B uniformly to obtain mixture C, wherein the final concentration of product A in mixture C is 10 wt%, inject into the syringe connected to the outer shaft of the 3D printer feeding;

[0054] (4) Dissolve calcium chloride in water to obtain 2 wt% solution D, and inject solution D into the syringe connected to the inner shaft of the 3D printer feeding;

[0055] (5) Custom coaxial printing nozzle (17 / 22G), use step (3) and step (4) to print a filament with hollow structure using two different materials by extrusion 3D printer, and prepare a three-dimensional hollow adsorbent by layer-by-layer stacking;

[0056] (6) UV crosslinking the three-dimensional hollow adsorbent obtained in step (5) for 30 min, then place it in acetic acid solution (6 vol.%), oscillate for 10 min to dissolve the solid calcium carbonate in the adsorbent, thereby introducing microporous structure into the three-dimensional hollow adsorbent; then wash it in distilled water for 3 times to remove the excess acetic acid on the surface, vacuum freeze-drying (-40 ℃, vacuum degree 0.02 Pa) to obtain a three-dimensional porous adsorbent.

[0057] Comparative Example 1

[0058] (1) Dissolve 0.5 mmol tannic acid and 1 mmol bismuth acetate in 30 mL acetic acid solution (6 vol.% acetic acid), ultrasonic (37 kHz) at room temperature and normal pressure for 30 min, centrifuge at 8000 rpm for 10 min after reaction at 60 ℃ for 24 hours, collect the precipitate, dry in a 60 ℃ oven to obtain product A;

[0059] (2) Disperse methacrylated sodium alginate (4 wt%), calcium carbonate (2 wt%) and LAP initiator (0.5 wt%) in water, mix uniformly to obtain product B;

[0060] (3) Mix product A and product B uniformly to obtain mixture C, wherein the final concentration of product A in mixture C is 10 wt%,

[0061] Pour into a 1 x 1 x 0.5 cm 3 mold, UV crosslinking for 30 min, then place it in 2 wt% calcium chloride solution for 30 min, then in acetic acid solution (6 vol.%), oscillate for 10 min to dissolve the solid calcium carbonate in the adsorbent, wash it in distilled water for 3 times to remove the excess acetic acid on the surface, vacuum freeze-drying (-40 ℃, vacuum degree 0.02 Pa) to obtain the adsorbent.

[0062] Comparative Example 2 (omit calcium carbonate)

[0063] (1) 0.5 mmol tannic acid and 1 mmol bismuth acetate were dissolved in 30 mL acetic acid solution (6 vol. % acetic acid), ultrasonic (37 kHz) for 30 min at room temperature and normal pressure, and after 24 hours of reaction at 60 °C, the precipitate was collected by centrifugation at 8000 rpm for 10 min and dried in an oven at 60 °C to obtain product A;

[0064] (2) Methylacrylated sodium alginate (4 wt%) and LAP initiator (0.5 wt%) were dispersed in water and mixed uniformly to obtain product B;

[0065] (3) Product A was mixed with product B uniformly to obtain mixture C, wherein the final concentration of product A in mixture C was 10 wt%, and mixture C was injected into a syringe and connected to the outer shaft of the 3D printer feeding;

[0066] (4) Calcium chloride was dissolved in water to obtain solution D (2 wt%), and solution D was injected into a syringe and connected to the inner shaft of the 3D printer feeding;

[0067] (5) A coaxial printing nozzle (17 / 22G) was customized, and a filament with a hollow structure was printed using an extrusion type 3D printer using two different materials of step (3) and step (4), and a three-dimensional hollow adsorbent was prepared by layer-by-layer stacking;

[0068] (6) The three-dimensional hollow adsorbent obtained in step (5) was subjected to ultraviolet crosslinking for 30 min and vacuum freeze-drying (-40 °C, vacuum degree 0.02 Pa) to obtain a three-dimensional porous adsorbent.

[0069] Comparative Example 3

[0070] (1) 0.5 mmol tannic acid and 1 mmol bismuth acetate were dissolved in 30 mL acetic acid solution (6 vol. % acetic acid), ultrasonic (37 kHz) for 30 min at room temperature and normal pressure, and after 24 hours of reaction at 60 °C, the precipitate was collected by centrifugation at 8000 rpm for 10 min and dried in an oven at 60 °C to obtain product A;

[0071] (2) Methylacrylated sodium alginate (4 wt%), calcium carbonate (2 wt%) and LAP initiator (0.5 wt%) were dispersed in water and mixed uniformly to obtain product B;

[0072] (3) Product A was mixed with product B uniformly to obtain mixture C, wherein the final concentration of product A in mixture C was 10 wt%, and mixture C was injected into a syringe; a three-dimensional adsorbent (without hollow structure) was prepared using an extrusion type 3D printer, and the printing structure was cured by ultraviolet light irradiation during printing;

[0073] (4) The three-dimensional adsorbent obtained in step (3) is subjected to ultraviolet crosslinking for 30 min, and then is placed in an acetic acid solution (6 vol. %) and shaken for 10 min to dissolve the solid calcium carbonate in the three-dimensional adsorbent, so as to introduce microporous structures into the three-dimensional adsorbent; then the three-dimensional adsorbent is washed in distilled water for 3 times to remove the excess acetic acid on the surface, and is vacuum freeze-dried to obtain the three-dimensional adsorbent.

[0074] Performance determination

[0075] 1. The MOFs three-dimensional porous adsorbents prepared in Examples 1-3 are subjected to surface area determination by BET, the degassing temperature is 300°C, the degassing time is 180 min, and the adsorbate is N2, and the results are shown in Table 1:

[0076] Table 1. Specific surface area of MOFs

[0077]

[0078] 2. 40 mg of the adsorbents prepared in Example 1 and Comparative Examples 1-3 are respectively taken, and are treated in 25 mL of a copper ion solution (500 ppm) with the same specification and a pH of 5.0 at 30°C for 6 hours, and the concentration of the remaining copper ions in the solution is determined, and the results are shown in Table 2:

[0079] Table 2. Concentration of copper ions in the solution

[0080]

[0081] 3. CuCl2, ZnCl2, CdCl2 and CrCl3·6H2O are respectively prepared into aqueous solutions with a metal ion concentration of 500 ppm, and the pH of the solution is adjusted to 5.0; then the three-dimensional hollow adsorbent prepared in Example 1 (dry weight 40 mg) is placed in 25 mL of the above-mentioned aqueous solution to perform metal ion adsorption, and the time is 6 hours, and the equilibrium adsorption amount of the metal ions is calculated, and the results are shown in Table 3:

[0082] Table 3. Equilibrium adsorption amount of different metal ions

[0083]

[0084] It can be seen from the results in the table that the three-dimensional hollow adsorbent prepared in Example 1 has high selectivity to copper ions.

[0085] 4. Cycle performance test

[0086] The adsorbent prepared in Example 1 (dry weight 40 mg) is taken, is placed in 25 mL of a CuCl2 solution (500 ppm) to perform adsorption, and after adsorption, is taken out, is immersed in a 0.1 mol / L HCl solution and is shaken for 1 hour until the adsorbed Cu2+ The eluate was washed with Milli-Q water several times, freeze-dried, and reused again. This was repeated 5 times and the equilibrium adsorption capacity of each adsorbent was determined and the results are shown in Table 4:

[0087] Table 4. Equilibrium adsorption capacity of adsorbents

[0088]

[0089] The above examples are not intended to limit the scope of the present application, nor are the described steps intended to limit the order in which they are performed. Modifications to the present application, which fall within the scope of the hereto appended claims, will be apparent to those skilled in the art with the benefit of this disclosure.

Claims

1. A method for preparing a three-dimensional porous adsorbent for efficient selective adsorption of copper ions, characterized by, The method comprises the following steps: (1) dissolving tannic acid and metal salt in acetic acid solution, ultrasonic reaction at room temperature and normal pressure, centrifugation after reaction, collecting precipitate, drying to obtain product A; The metal salt is bismuth acetate; (2) dispersing methacrylated sodium alginate, calcium carbonate and LAP initiator in water and mixing uniformly to obtain product B; (3) mixing product A and product B uniformly to obtain mixture C, injecting into a syringe and connecting to the outer shaft of the 3D printer feeding; dissolving calcium chloride in water to obtain solution D, and injecting solution D into a syringe and connecting to the inner shaft of the 3D printer feeding; extruding 3D printer through the coaxial printing nozzle to print three-dimensional hollow adsorbent; (4) ultraviolet crosslinking the three-dimensional hollow adsorbent printed in step (3), then placing in acetic acid solution for oscillation to dissolve the solid calcium carbonate in the adsorbent, obtaining three-dimensional hollow adsorbent with microporous structure, washing, drying, and obtaining three-dimensional porous adsorbent.

2. The method of claim 1, wherein, The molar ratio of tannic acid to metal salt in step (1) is 2:1-1:

2.

3. The method of claim 1, wherein, The ultrasonic reaction conditions in step (1) are: first ultrasonic at a power of 25-40 kHz for 20-40 min, and then reacting at 40-70 ℃ for 18-24 h.

4. The method of claim 1, wherein, The mass concentration of methacrylated sodium alginate in product B in step (2) is 4-6%, the mass concentration of calcium carbonate is 2-3%, and the mass concentration of LAP initiator is 0.5-1.0%.

5. The method of claim 1, wherein, The mass concentration of product A in mixture C in step (3) is 10-15%.

6. The method of claim 1, wherein, The mass concentration of solution D in step (3) is 1-3%.

7. The three-dimensional porous adsorbent obtained by the method of any one of claims 1-6.

8. The application of the three-dimensional porous adsorbent of claim 7 in water treatment.

9. A method for improving the removal of copper ions from wastewater, characterized by, The method is to use the three-dimensional porous adsorbent of claim 7 for removing copper ions in wastewater.

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