Preparation method and application of UiO-66 / MWCNTs-COOH / SA composite gel microspheres

Abstract

The invention discloses a preparation method and application of UiO-66 / MWCNTs-COOH / SA composite gel microspheres, and belongs to the technical field of composite material preparation. The preparation method comprises the following steps: mixing a zirconium source, terephthalic acid, carboxylated multi-walled carbon nanotubes, a solvent and glacial acetic acid, and heating for reaction to obtain a UiO-66 / MWCNTs-COOH composite material; adding sodium alginate according to a certain proportion, and cross-linking the SA-UC gel microspheres with the sodium alginate to form SA-UC composite gel microspheres. The SA-UC composite gel microspheres have high adsorption capacity on quinolone antibiotics, are easier to carry out solid-liquid separation, and have the advantages of high recycling rate and good recycling performance. In addition, when the SA-UC composite gel microspheres adsorb norfloxacin in solutions with different ionic strengths, the adsorption capacity can still reach about 90%, and the anti-ionic interference capability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material preparation, and particularly relates to a preparation method and application of UiO-66 / MWCNTs-COOH / SA composite gel microspheres. Background Art

[0002] In recent years, antibiotics have been widely used in fields such as medicine, agriculture, animal husbandry, and aquaculture to effectively reduce the mortality rate of some diseases and save countless lives. However, antibiotics enter the water environment through runoff, diffusion, percolation and other channels, causing pollution of drinking water sources. Quinolone antibiotics such as enrofloxacin and norfloxacin are a class of broad-spectrum antibiotic drugs that are extremely stable and difficult to degrade in the water environment. They can exist in the water environment for a long time, enter natural waters through various channels, and accumulate in large quantities in the aquatic environment due to their extreme stability, wide distribution, and difficulty in natural degradation, leading to the generation of drug-resistant bacteria and drug-resistant genes. At the same time, these drugs can also be absorbed by animals and plants, accumulate through the food chain, and ultimately be absorbed by the human body, posing a major risk to public health. With the continuous growth of global antibiotic consumption, the content of antibiotics in water bodies is also increasing day by day, which poses a huge threat to the health of animals, plants, and humans. The prevention and treatment of antibiotics and other drugs are one of the main problems faced in the current water environment restoration and treatment.

[0003] For the treatment of wastewater containing antibiotics, there are mainly three categories: physical methods, biological methods, and chemical methods. Among them, the adsorption method has the advantages of simple operation, high treatment efficiency, no secondary pollution, and easy recovery, and is considered to be one of the most effective wastewater treatment methods. The adsorption method requires a suitable adsorbent, and common adsorbents include activated carbon, modified minerals, biochar, metal-organic framework materials, etc. However, as powder materials, the above-mentioned adsorbents face some problems in actual use, such as difficult separation and recovery, easy loss, which limits the efficiency of reuse. Moreover, the adsorption effect of the existing adsorbents on quinolone antibiotics also needs to be improved.

[0004] Therefore, it is very necessary to develop an adsorbent material with good adsorption effect on quinolone antibiotics in water, high recovery and utilization rate, and good reusability. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of UiO-66 / MWCNTs-COOH / SA composite gel microspheres to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: A preparation method of UiO-66 / MWCNTs-COOH / SA composite gel beads, comprising the following steps:

[0008] Mix a zirconium source, terephthalic acid (H2BDC), carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), a solvent and glacial acetic acid, and heat for reaction to obtain a UiO-66 / MWCNTs-COOH composite material; mix the UiO-66 / MWCNTs-COOH composite material, sodium alginate (SA) and water to obtain a mixed solution; drop the mixed solution into an aqueous metal salt solution, cure, wash, and freeze-dry to obtain the UiO-66 / MWCNTs-COOH / SA composite gel beads.

[0009] The UiO-66 / MWCNTs-COOOH composite material has a relatively high specific surface area, rich pore structure and surface functional groups, and has good adsorption performance for quinolone antibiotics. SA has rich oxygen-containing functional groups of hydroxyl and carboxyl, and also has certain adsorption performance for quinolone antibiotics. The UiO-66 / MWCNTs-COOH / SA composite gel beads obtained by combining the UiO-66 / MWCNTs-COOOH composite material and SA have good comprehensive adsorption performance for quinolone antibiotics. Moreover, SA is a natural anionic polysaccharide extracted from algae, which has the characteristics of environmental friendliness, high biocompatibility, easy degradation, renewable and non-toxic, etc. It can be gelled by various different cations such as calcium, copper, zinc, manganese, ferrous and aluminum to form a gel. By introducing SA to crosslink with the UiO-66 / MWCNTs-COOH composite material to form stable composite gel beads, the problem of difficult solid-liquid separation of powder materials is solved, and the use performance of the UiO-66 / MWCNTs-COOH composite material is improved.

[0010] Further, the zirconium source is ZrCl4; the solvent is N,N-dimethylformamide (DMF).

[0011] Further, the mixing of the zirconium source, terephthalic acid, carboxylated multi-walled carbon nanotubes, solvent and glacial acetic acid includes: dissolving the zirconium source and terephthalic acid in half of the amount of DMF respectively to obtain a zirconium source solution and a terephthalic acid solution; mixing the zirconium source solution and the terephthalic acid solution, adding carboxylated multi-walled carbon nanotubes under vigorous stirring, and slowly adding glacial acetic acid at the same time.

[0012] Further, the adding rate of the glacial acetic acid is 1 drop / s.

[0013] Further, the dosage ratio of the zirconium source, terephthalic acid, solvent, and glacial acetic acid is 2.73 mmol: 2.46 mmol: 37.6 mL: 2.3 mL; the mass of the carboxylated multi-walled carbon nanotubes is 4.8% of the sum of the masses of the carboxylated multi-walled carbon nanotubes, zirconium source, and terephthalic acid.

[0014] Further, the temperature of the heating reaction is 120 °C, and the time is 18 - 24 h.

[0015] Further, after the heating reaction, it also includes the steps of cooling to room temperature, washing, and vacuum drying.

[0016] Further, the specific operation of the washing is: centrifugally washing 3 times with DMF and absolute ethanol respectively; the rotation speed of the centrifugal washing is ≥ 8000 rpm.

[0017] Further, the temperature of the vacuum drying is 60 - 80 °C, the pressure is 10 Pa, and the time is 10 - 12 h.

[0018] Further, the mixing of the UiO-66 / MWCNTs-COOH composite material, sodium alginate, and water to obtain a mixed solution includes: adding the UiO-66 / MWCNTs-COOH composite material into water, ultrasonicating until the composite material is completely dispersed in water, then adding sodium alginate, and stirring at room temperature for 2 h to fully mix it with the composite material to obtain a mixed solution.

[0019] Further, the dosage ratio of the UiO-66 / MWCNTs-COOH composite material, sodium alginate, and water is 1 - 3 g: 1 g: 50 mL.

[0020] Further, the metal salt aqueous solution is a calcium salt aqueous solution, a copper salt aqueous solution, a zinc salt aqueous solution, a manganese salt aqueous solution, a ferrous salt aqueous solution, or an aluminum salt aqueous solution, preferably a calcium salt aqueous solution; the concentration of the metal salt aqueous solution is 2 wt%.

[0021] Further, the calcium salt aqueous solution is a CaCl₂ aqueous solution.

[0022] Further, the dropping rate of the mixed solution into the metal salt aqueous solution is 1 drop / s.

[0023] Further, the curing time is 1 - 2 h;

[0024] And / or, the conditions of the freeze-drying include: the temperature is -50 °C, the pressure is 10 Pa, and the time is 12 - 14 h.

[0025] Further, the curing is carried out at room temperature.

[0026] The second technical solution of the present invention: UiO-66 / MWCNTs-COOH / SA composite gel beads prepared according to the above preparation method.

[0027] The third technical solution of the present invention: Application of the above UiO-66 / MWCNTs-COOH / SA composite gel beads in adsorbing antibiotics in wastewater.

[0028] Furthermore, the antibiotic is a quinolone antibiotic.

[0029] Furthermore, the quinolone antibiotic is enrofloxacin or norfloxacin (NOR).

[0030] Furthermore, the adsorption step includes: adding the UiO-66 / MWCNTs-COOH / SA composite gel beads to the wastewater containing quinolone antibiotics, adjusting the pH value of the wastewater to 2-10, and oscillating and adsorbing at room temperature.

[0031] The present invention discloses the following technical effects:

[0032] (1) The UiO-66 / MWCNTs-COOOH composite material in the UiO-66 / MWCNTs-COOH / SA composite gel beads of the present invention has a high specific surface area, rich pore structure and surface functional groups, and has good adsorption performance for quinolone antibiotics. SA has rich oxygen-containing functional groups, hydroxyl and carboxyl groups, and also has certain adsorption performance for quinolone antibiotics. The UiO-66 / MWCNTs-COOH / SA composite gel beads obtained by combining the UiO-66 / MWCNTs-COOOH composite material and SA have good comprehensive adsorption performance for quinolone antibiotics.

[0033] (2) The present invention solves the problem of difficult solid-liquid separation of powder materials by introducing SA to crosslink with the UiO-66 / MWCNTs-COOH composite material to form stable composite gel beads, and improves the use performance of the UiO-66 / MWCNTs-COOH composite material.

[0034] (3) Soaking the UiO-66 / MWCNTs-COOH / SA composite gel beads that have adsorbed norfloxacin in a methanol solution with pH = 2 for 24 h can remove the adsorbed NOR. After washing with deionized water and freeze-drying for 12 h, it can be reused for adsorbing NOR. After 6 cycles, the adsorption capacity can still reach 74.4% of the initial capacity, and the recycling performance is good. The present invention improves the reusability of the adsorbent.

[0035] (4) After the UiO-66 / MWCNTs-COOH composite material is cross-linked with SA, the composite gel microspheres have a higher specific surface area and pore volume. The crystal structure of the UiO-66 / MWCNTs-COOH composite material remains unchanged. Compared with the UiO-66 / MWCNTs-COOH composite material, the adsorption capacity of the composite gel microspheres does not change significantly, but it is easier to perform solid-liquid separation, increasing the recycling rate of the adsorbent.

[0036] (5) The present invention tested the adsorption performance of the composite gel microspheres for NOR in a CaCl2 solution. When the CaCl2 concentration was 0.90 mol / L, the adsorption capacity decreased by 10.89%. This shows that although the presence of different anions and cations has a certain interference on the interaction between the UiO-66 / MWCNTs-COOH / SA composite gel microspheres and NOR, the adsorption capacity of the composite gel microspheres can be maintained at about 90%, having a high anti-ion interference ability. It can still maintain good adsorption ability at a higher ionic strength.

[0037] (6) The present invention characterized the surface morphology of the UiO-66 / MWCNTs-COOH / SA composite gel microspheres with different contents of the UiO-66 / MWCNTs-COOH composite material. The results show that as the content of the UiO-66 / MWCNTs-COOH composite material increases, the wrinkling state and depression phenomenon on the surface of the SA microspheres weaken, and the adsorption effect between the active sites and the drug enhances. The layered structure of the UiO-66 / MWCNTs-COOH composite material is distributed inside the microspheres, improving the stability and adsorption capacity of the UiO-66 / MWCNTs-COOH / SA composite gel microspheres. Description of the Drawings

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0039] Figure 1 SEM images of the UiO-66 / MWCNTs-COOH / SA composite gel microspheres with different composite material contents prepared in Examples 1-3 and Comparative Example 1, where (a)-(d) represent the contents of the UiO-66 / MWCNTs-COOH composite material being 0%, 50%, 67%, and 75% respectively;

[0040] Figure 2Adsorption performance test results of SA-UC composite gel microspheres prepared in Examples 1-3 and SA gel microspheres prepared in Comparative Example 1 under different pH conditions;

[0041] Figure 3 Adsorption performance test results of SA-UC75 composite gel microspheres prepared in Example 3 under different interfering ion concentrations;

[0042] Figure 4 Reusability test results of SA-UC75 composite gel microspheres prepared in Example 3. Detailed implementation manners

[0043] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0044] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0045] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0046] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0047] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0048] It should be noted that the aspects not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0049] As a first aspect of the present invention, the present invention provides a method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microspheres, comprising the following steps:

[0050] Mix a zirconium source, terephthalic acid (H2BDC), carboxylated multi-walled carbon nanotubes (MWCNTs-COOH), a solvent and glacial acetic acid, and heat the mixture for reaction to obtain a UiO-66 / MWCNTs-COOH composite material; mix the UiO-66 / MWCNTs-COOH composite material, sodium alginate (SA) and water to obtain a mixed solution; drop the mixed solution into an aqueous metal salt solution, solidify, wash, and freeze-dry to obtain the UiO-66 / MWCNTs-COOH / SA composite gel microspheres.

[0051] As a preferred technical solution of the present invention, the more specific steps of the preparation method include:

[0052] (1) Prepare a UiO-66 / MWCNTs-COOH composite material:

[0053] Weigh 0.6360 g (2.73 mmol) of ZrCl4 and 0.4080 g (2.46 mmol) of H2BDC, and dissolve them separately in 18.8 mL of DMF, and stir until dissolved; after dissolution, fully mix the two solutions, and then add MWCNTs-COOH (the mass of MWCNTs-COOH is 4.8 wt% of the sum of the masses of MWCNTs-COOH, ZrCl4 and H2BDC) under vigorous stirring, and at the same time slowly add 2.3 mL of glacial acetic acid (the dropping rate is 1 drop / s) to promote crystal formation; transfer the mixed solution to a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and react at a temperature of 120 °C for 18 - 24 h; after the reaction is completed and cooled to room temperature, centrifuge and wash 3 times with DMF and absolute ethanol respectively (the rotation speed of the centrifuge ≥ 8000 rpm), and finally vacuum dry for 10 - 12 h (the temperature is 60 - 80 °C, and the pressure is 10 Pa) to obtain a UiO-66 / MWCNTs-COOH composite material powder;

[0054] (2) Synthesize UiO-66 / MWCNTs-COOH / SA composite gel microspheres:

[0055] Add 1 - 3 g of UiO-66 / MWCNTs-COOH composite material powder into a beaker, add 50 mL of deionized water, and ultrasonicate until the powder is completely dissolved in water; then add 1 g of SA powder, stir at room temperature for 2 h to fully mix it with the composite material to obtain a mixed solution; use a 5-mL pipette to slowly drip the mixed solution into an aqueous solution of a metal salt (calcium salt, copper salt, zinc salt, manganese salt, ferrous salt or aluminum salt, preferably CaCl₂) with a concentration of 2 wt% (the dripping rate is 1 drop / s) to form gel beads, and cure in the solution for 1 - 2 h; repeatedly rinse with deionized water to remove residual impurities on the surface, and freeze-dry for 12 - 14 h (temperature is -50 °C, pressure is 10 Pa) to obtain UiO-66 / MWCNTs-COOH / SA composite gel microspheres, denoted as SA-UC.

[0056] As the second aspect of the present invention, the present invention provides UiO-66 / MWCNTs-COOH / SA composite gel microspheres prepared according to the above preparation method.

[0057] As the third aspect of the present invention, the present invention provides the application of the above UiO-66 / MWCNTs-COOH / SA composite gel microspheres in adsorbing antibiotics in wastewater.

[0058] As a preferred embodiment of the present invention, the antibiotic is a quinolone antibiotic.

[0059] As a preferred embodiment of the present invention, the quinolone antibiotic is enrofloxacin or norfloxacin.

[0060] As a preferred embodiment of the present invention, the adsorption step includes: adding the UiO-66 / MWCNTs-COOH / SA composite gel microspheres into wastewater containing quinolone antibiotics, adjusting the pH value of the wastewater to 2 - 10, and oscillating and adsorbing at room temperature.

[0061] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0062] All raw materials used in the specific embodiments of the present invention are ordinary commercially available products. Among them, MWCNTs-COOH is purchased from Nanjing Xianfeng Nano Material Technology Co., Ltd., its purity > 95%, and the carboxyl content is 2.56 wt%.

[0063] The room temperature involved in the specific embodiments of the present invention specifically refers to 20 - 30 °C.

[0064] Example 1

[0065] A preparation method of UiO-66 / MWCNTs-COOH / SA composite gel microspheres is as follows:

[0066] (1) Preparation of UiO-66 / MWCNTs-COOH composite material:

[0067] Weigh 0.6360 g (2.73 mmol) of ZrCl4 and 0.4080 g (2.46 mmol) of H2BDC, and dissolve them separately in 18.8 mL of DMF, stirring until dissolved. After dissolution, mix the two solutions thoroughly, and then add 0.0523 g of MWCNTs-COOH (the mass of MWCNTs-COOH is 4.8 wt% of the sum of the masses of MWCNTs-COOH, ZrCl4, and H2BDC) under vigorous stirring (rotation speed of 280 rpm). At the same time, slowly add 2.3 mL of glacial acetic acid (dropwise addition rate of 1 drop / s) to promote crystal formation. Transfer the mixed solution to a hydrothermal reaction kettle with a polytetrafluoroethylene liner and react at a temperature of 120 °C for 24 h. After the reaction is completed and cooled to room temperature, centrifuge and wash 3 times with DMF and absolute ethanol respectively (rotation speed of the centrifuge is 8000 rpm), and finally dry in vacuum for 10 h (temperature is 60 °C, pressure is 10 Pa) to obtain the UiO-66 / MWCNTs-COOH composite material powder.

[0068] (2) Synthesis of UiO-66 / MWCNTs-COOH / SA composite gel beads:

[0069] Add 1 g of UiO-66 / MWCNTs-COOH composite material powder to a beaker, add 50 mL of deionized water, and ultrasonicate until the powder is completely dissolved in water. Then add 1 g of SA powder and stir at room temperature for 2 h to mix it thoroughly with the composite material to obtain a mixed solution. Slowly drip the mixed solution into a 2 wt% aqueous CaCl2 solution with a 5 mL pipette (dropwise addition rate of 1 drop / s) to form gel beads and solidify in the solution for 1 h. Rinse repeatedly with deionized water to remove residual impurities on the surface, and freeze-dry for 12 h (temperature is -50 °C, pressure is 10 Pa) to obtain UiO-66 / MWCNTs-COOH / SA composite gel beads with a UiO-66 / MWCNTs-COOH composite material content of 50 wt%, denoted as SA-UC50.

[0070] Example 2

[0071] A preparation method of UiO-66 / MWCNTs-COOH / SA composite gel beads is as follows:

[0072] (1) Preparation of UiO-66 / MWCNTs-COOH composite material:

[0073] Weigh 0.6360 g of ZrCl4 and 0.4080 g of H2BDC, and dissolve them separately in 18.8 mL of DMF. Stir until dissolved. After dissolution, mix the two solutions thoroughly, and then add 0.0523 g of MWCNTs-COOH (the mass of MWCNTs-COOH is 4.8 wt% of the sum of the masses of MWCNTs-COOH, ZrCl4, and H2BDC) while stirring vigorously (at a rotation speed of 280 rpm). At the same time, slowly add 2.3 mL of glacial acetic acid (the dropping rate is 1 drop / s) to promote crystal formation. Transfer the mixed solution to a hydrothermal reaction kettle with a polytetrafluoroethylene lining and react at a temperature of 120 °C for 24 h. After the reaction is completed and cooled to room temperature, centrifuge and wash three times with DMF and absolute ethanol respectively (the rotation speed of the centrifuge is 8000 rpm), and finally dry in vacuum for 10 h (the temperature is 60 °C and the pressure is 10 Pa) to obtain the UiO-66 / MWCNTs-COOH composite material powder.

[0074] (2) Synthesis of UiO-66 / MWCNTs-COOH / SA composite gel beads:

[0075] Add 2 g of the UiO-66 / MWCNTs-COOH composite material powder to a beaker, add 50 mL of deionized water, and ultrasonicate until the powder is completely dissolved in water. Then add 1 g of SA powder and stir at room temperature for 2 h to mix it thoroughly with the composite material to obtain a mixed solution. Slowly drip the mixed solution into a 2 wt% aqueous CaCl2 solution with a 5 mL pipette (the dropping rate is 1 drop / s) to form gel beads, and solidify in the solution for 1 h. Rinse repeatedly with deionized water to remove the residual impurities on the surface, and freeze-dry for 12 h (the temperature is -50 °C and the pressure is 10 Pa) to obtain UiO-66 / MWCNTs-COOH / SA composite gel beads with a UiO-66 / MWCNTs-COOH composite material content of 67 wt%, denoted as SA-UC67.

[0076] Example 3

[0077] A preparation method of UiO-66 / MWCNTs-COOH / SA composite gel beads is as follows:

[0078] (1) Preparation of UiO-66 / MWCNTs-COOH composite material:

[0079] Weigh 0.6360 g of ZrCl4 and 0.4080 g of H2BDC, and dissolve them separately in 18.8 mL of DMF. Stir until dissolved. After dissolution, mix the two solutions thoroughly, and then add 0.0523 g of MWCNTs-COOH (the mass of MWCNTs-COOH is 4.8 wt% of the sum of the masses of MWCNTs-COOH, ZrCl4, and H2BDC) under vigorous stirring (rotation speed of 280 rpm). At the same time, slowly add 2.3 mL of glacial acetic acid (dropwise addition rate of 1 drop / s) to promote crystal formation. Transfer the mixed solution to a hydrothermal reaction kettle with a polytetrafluoroethylene lining and react at a temperature of 120 °C for 24 h. After the reaction is completed and cooled to room temperature, centrifuge and wash 3 times with DMF and absolute ethanol respectively (rotation speed of the centrifuge is 8000 rpm), and finally dry in vacuum for 10 h (temperature is 60 °C, pressure is 10 Pa) to obtain UiO-66 / MWCNTs-COOH composite material powder.

[0080] (2) Synthesis of UiO-66 / MWCNTs-COOH / SA composite gel beads:

[0081] Add 3 g of UiO-66 / MWCNTs-COOH composite material powder to a beaker, add 50 mL of deionized water, and ultrasonically dissolve the powder completely in water. Then add 1 g of SA powder and stir at room temperature for 2 h to mix it thoroughly with the composite material to obtain a mixed solution. Slowly drip the mixed solution into a 2 wt% aqueous solution of CaCl2 with a 5 mL pipette (dropwise addition rate of 1 drop / s) to form gel beads and solidify in the solution for 1 h. Rinse repeatedly with deionized water to remove residual impurities on the surface, and freeze-dry for 12 h (temperature is -50 °C, pressure is 10 Pa) to obtain UiO-66 / MWCNTs-COOH / SA composite gel beads with a UiO-66 / MWCNTs-COOH composite material content of 75 wt%, denoted as SA-UC75.

[0082] Comparative Example 1

[0083] The preparation of SA gel beads is as follows:

[0084] Add 1 g of SA powder to a beaker, add 50 mL of deionized water, and stir at room temperature for 2 h to obtain an SA solution. Slowly drip the SA solution into a 2 wt% aqueous solution of CaCl2 with a 5 mL pipette (dropwise addition rate of 1 drop / s) to form gel beads and solidify in the solution for 1 h. Rinse repeatedly with deionized water to remove residual impurities on the surface, and freeze-dry for 12 h (temperature is -50 °C, pressure is 10 Pa) to obtain SA gel beads, denoted as SA.

[0085] Comparative Example 2

[0086] Preparation of UiO-66 powder is as follows:

[0087] Weigh 0.6360 g (2.73 mmol) of ZrCl4 and 0.4080 g (2.46 mmol) of H2BDC, dissolve them separately in 18.8 mL of DMF, and stir until dissolved. After dissolution, mix the two solutions thoroughly, and then slowly add 2.3 mL of glacial acetic acid (the dropping rate is 1 drop / s) to promote crystal formation. Transfer the mixed solution to a hydrothermal reaction kettle with a polytetrafluoroethylene lining, and react at a temperature of 120 °C for 24 h. After the reaction is completed and cooled to room temperature, centrifuge and wash three times with DMF and absolute ethanol respectively (the rotation speed of the centrifuge is 8000 rpm), and finally dry in vacuum for 10 h (temperature is 60 °C, pressure is 10 Pa) to obtain UiO-66 powder.

[0088] Test Example 1

[0089] Structure Characterization

[0090] Figure 1 SEM images of UiO-66 / MWCNTs-COOH / SA composite gel beads with different composite material contents prepared in Examples 1-3 and Comparative Example 1, where (a)-(d) represent the contents of UiO-66 / MWCNTs-COOH composite materials of 0% (Comparative Example 1, i.e., SA), 50% (Example 1), 67% (Example 2), and 75% (Example 3) respectively. It can be seen from Figure 1 that as the percentage content of UiO-66 / MWCNTs-COOH increases, the wrinkling state and depression phenomenon on the surface of SA beads weaken, more and more UiO-66 / MWCNTs-COOH composite materials are exposed on the outer surface of the beads, and the pore structure on the inner surface of the beads is also more abundant.

[0091] In addition, after testing, the specific surface area (S BET ) of the UiO-66 / MWCNTs-COOH composite material is 742.13 m 2 / g, and the specific surface area (S BET ) of SA-UC75 is 928.80 m 2 / g.

[0092] Test Example 2

[0093] Adsorption Performance Test

[0094] 1. Adsorption performance test of the adsorbent for NOR under different pH conditions

[0095] The adsorbents (SA-UC prepared in Examples 1-3 and SA prepared in Comparative Example 1) were used for the adsorption test of the antibiotic norfloxacin (NOR) under different pH conditions. First, 10 mg of the adsorbent was added to 25 mL of a norfloxacin solution with a concentration of 100 mg / L. The solution was adjusted to pH 2-10 using 0.1 mol / L NaOH and HNO3 respectively. After adjusting the pH of the solution, it was placed in a constant temperature shaker and shaken (25 °C, 180 rpm) for 24 h. The effect of different pH on the adsorption performance was investigated. After the reaction, a 0.45 μm aqueous PTFE membrane was used for filtration to remove the adsorbent in the solution. After appropriately diluting the solution, the initial and final concentrations of NOR were measured using a UV-visible spectrophotometer at a wavelength of 273 nm, and the adsorption capacity (Q e ) was calculated. All experiments were repeated three times, and the average value of the three times was taken to ensure the accuracy of the experimental data. The adsorption performance test results of SA-UC prepared in Examples 1-3 and SA prepared in Comparative Example 1 for NOR under different pH conditions are as shown in Figure 2 . As can be seen from Figure 2 , as the pH increases, the adsorption amount of norfloxacin by the gel beads increases. When the content of the UiO-66 / MWCNTs-COOH composite material increases, the adsorption amount of the SA-UC composite gel beads increases. Among them, at pH = 10, SA-UC75 exhibits the best adsorption performance, and the adsorption capacity (Q e ) under the above adsorption conditions is 94.5 mg / g. In addition, multiple groups of adsorption experiments were carried out by changing the concentration of the norfloxacin solution, and the Langmuir isothermal adsorption model was used to fit the isothermal adsorption curve to obtain the maximum adsorption capacity (Q max ) of SA-UC75 at 25 °C and pH = 10 as 126.37 mg / g. Combining with the SEM image of the composite gel beads (shown in Figure 1 ), it is speculated that as the percentage content of UiO-66 / MWCNTs-COOH increases, more and more UiO-66 / MWCNTs-COOH composite materials are exposed on the outer surface of the beads, and the pore structure on the inner surface of the beads is also more abundant, providing more active adsorption functional groups and active sites for adsorption, resulting in an increase in the adsorption amount. In addition, the above method was used to test the adsorption performance of the UiO-66 powder prepared in Comparative Example 2, the raw material MWCNTs-COOH powder, and the UiO-66 / MWCNTs-COOH composite material prepared in step (1) of Example 1. The results obtained show that the maximum adsorption capacities (Q max) They are 73.2 mg / g, 98.1 mg / g and 143.8 mg / g respectively. The adsorption performance of the UiO-66 / MWCNTs-COOH composite material for NOR is significantly improved compared with that of UiO-66 powder and MWCNTs-COOH powder. Moreover, the maximum adsorption capacity (Q max ) of SA-UC75 is reduced by 12.1% compared with the UiO-66 / MWCNTs-COOH composite material. It shows that the adsorption capacity of the composite gel beads decreases, but the composite gel beads are easier to separate solid from liquid, increasing the recycling rate of the adsorbent.

[0096] 2. Adsorption performance test of the adsorbent for NOR under different interfering ion concentrations

[0097] The SA-UC75 composite gel beads prepared in Example 3 were used to explore the influence of different interfering ion strengths on the adsorption performance of NOR. First, 10 mg of the SA-UC75 composite gel beads were added to 25 mL of a norfloxacin solution with a concentration of 100 mg / L and pH = 10. CaCl2 powder was added to make the solution concentrations 0.00, 0.15, 0.30, 0.45, 0.60, 0.75, 0.90 mol / L respectively. Then it was placed in a constant temperature shaking incubator (25 °C, 180 rpm) and shaken for 24 h. After the reaction ended, a 0.45 μm aqueous PTFE filter membrane was used for filtration to remove the adsorbent in the solution. The initial and final concentrations of NOR were measured by an ultraviolet-visible spectrophotometer at a wavelength of 273 nm, and the adsorption capacity (Q e ) was calculated. All experiments were repeated three times, and the average value of the three times was taken to ensure the accuracy of the experimental data. The test results are as Figure 3 shown. As Figure 3 can be seen, as the concentration of CaCl2 in the solution increases, the adsorption capacity of the SA-UC75 composite gel beads decreases. When the concentration increases to 0.90 mol / L, the adsorption capacity drops by 10.89%, but still maintains a relatively high adsorption capacity. It shows that the SA-UC75 composite gel beads have high anti-ion interference ability and can still maintain good adsorption ability even under high ion strength conditions.

[0098] 3. Recycling rate test of the adsorbent

[0099] The SA-UC50, SA-UC67, SA-UC75 composite gel beads and SA and pure UiO-66 / MWCNTs-COOH composite material powders collected after the adsorption performance test under the condition of pH = 10 were respectively soaked in a methanol solution with pH = 2 (concentration of 99 wt%) for 24 h to remove the adsorbed NOR, and then repeatedly washed with deionized water. Then, the washed gel beads were freeze-dried for 12 h (temperature of -50 °C, pressure of 10 Pa). Finally, the mass of the gel beads after desorption was weighed with an analytical balance, and the recovery rate of the gel beads was calculated. Each operation was repeated three times, and the average value of the three times was taken to ensure the accuracy of the experimental data. It was obtained by testing that the recovery rates of SA, SA-UC50, SA-UC67, and SA-UC75 gel beads were 97.5%, 97.2%, 98.0%, and 98.7% respectively, and the recovery rate of the UiO-66 / MWCNTs-COOH composite material powder was 81%. The recovery rates of the composite gel beads with different contents of UiO-66 / MWCNTs-COOH composite materials in the adsorption of NOR were all above 97%. With the increase of the content of UiO-66 / MWCNTs-COOH composite materials, the recovery rate increased, and the SA-UC75 composite gel beads had the highest recovery rate, which was 98.7%. It shows that the composite gel beads have a very high recovery rate.

[0100] 4. Reusability test

[0101] The SA-UC75 composite gel beads collected after the adsorption performance test under the condition of pH = 10 were soaked in a methanol solution with pH = 2 (concentration of 99 wt%) for 24 h to remove the adsorbed norfloxacin NOR, and then repeatedly washed with deionized water. Then, the washed composite gel beads were freeze-dried for 12 h (temperature of -50 °C, pressure of 10 Pa). The desorbed SA-UC75 composite gel beads were used for the experiment of repeatedly adsorbing norfloxacin NOR, and the adsorption conditions were the same as those in the adsorption performance test under the condition of pH = 10 above. The adsorption and desorption processes were repeated many times. The test results are as Figure 4 shown (where 0 represents the first adsorption of the new adsorbent, and 1 represents the first adsorption of the recovered adsorbent, that is, the second adsorption of the original adsorbent). From Figure 4It can be seen that with the increase of the number of cycles, the adsorption capacity of the composite gel microspheres decreases. After 3 cycles (i.e., the adsorption capacity corresponding to 2 on the abscissa in the figure), the adsorption capacity drops to 80.3 mg / g, which is about 85% of the initial adsorption capacity (i.e., the adsorption capacity corresponding to 0 on the abscissa in the figure); and when it goes through 6 cycles (i.e., the adsorption capacity corresponding to 5 on the abscissa in the figure), the adsorption capacity drops to 70.31 mg / g, still reaching 74.4% of the initial adsorption capacity. This shows that the composite gel microspheres have good reusability and can be well applied to the removal of norfloxacin in wastewater.

[0102] The embodiments described above are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microbeads, characterized in that: The following steps are involved: A zirconium source, terephthalic acid, carboxylated multi-walled carbon nanotubes, a solvent and glacial acetic acid are mixed and heated for reaction to obtain a UiO-66 / MWCNTs-COOH composite material; the UiO-66 / MWCNTs-COOH composite material, sodium alginate and water are mixed to obtain a mixed solution; the mixed solution is dropped into a metal salt aqueous solution, solidified, washed and freeze-dried to obtain the UiO-66 / MWCNTs-COOH / SA composite gel microbeads.

2. The method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The usage ratio of the zirconium source, terephthalic acid, solvent and glacial acetic acid is 2.73mmol:2.46mmol:37.6mL:2.3mL; the mass of the carboxylated multi-walled carbon nanotubes is 4.8% of the sum of the mass of the carboxylated multi-walled carbon nanotubes, the zirconium source and terephthalic acid.

3. The method for preparing the UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The heating reaction is carried out at a temperature of 120° C. and for a period of 18-24 hours.

4. The method for preparing the UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The usage ratio of the UiO-66 / MWCNTs-COOH composite material, sodium alginate and water is 1-3g:1g:50mL.

5. The method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The metal salt aqueous solution is a calcium salt aqueous solution, a copper salt aqueous solution, a zinc salt aqueous solution, a manganese salt aqueous solution, a ferrous salt aqueous solution or an aluminum salt aqueous solution; and the concentration of the metal salt aqueous solution is 2 wt %.

6. The method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The dripping speed of the mixed solution dripping into the metal salt aqueous solution is 1 drop / s.

7. The method for preparing UiO-66 / MWCNTs-COOH / SA composite gel microbeads according to claim 1, characterized in that: The curing time is 1-2h; And / or, the freeze-drying conditions include: temperature of -50°C, pressure of 10Pa, and time of 12-14h.

8. UiO-66 / MWCNTs-COOH / SA composite gel microbeads prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the UiO-66 / MWCNTs-COOH / SA composite gel microbeads as claimed in claim 8 in adsorbing antibiotics in wastewater.

10. The use according to claim 9, characterized in that The antibiotic is a quinolone antibiotic.

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