A magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent, its preparation method and application

Abstract

This invention discloses a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure, its preparation method, and its application. The magnetic material H-Fe3O4@SiO2@ZIFs is synthesized using a solvothermal and room-temperature aqueous phase method. The method first uses a solvothermal reaction to ultrasonically mix trivalent iron, sodium salt, and an alcohol solvent to prepare magnetic Fe3O4 nanospheres. Then, the surface of the Fe3O4 nanospheres is functionalized to obtain core-shell Fe3O4@SiO2 nanoparticles. Finally, Fe3O4@SiO2 is added to a mixture of zinc acetate dihydrate, dimethylimidazolium, and polydiallyldimethylammonium chloride to react and obtain the hierarchical porous magnetic composite adsorbent. This invention features a simple operation process, high operability, and ease of large-scale production. It possesses advantages such as Lewis acidic sites, large specific surface area, hierarchical porous structure, and easy recovery. It can efficiently adsorb drugs such as tetracycline hydrochloride and diclofenac sodium, exhibiting high adsorption capacity and excellent adsorption performance, and has broad application prospects in pharmaceutical wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, and relates to ZIFs composite adsorbents, specifically to a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent, its preparation method, and its application. Background Technology

[0002] Since their discovery in 1948, tetracycline antibiotics have been widely used in disease treatment due to their strong antibacterial properties, few side effects, low cost, and broad spectrum of activity. As one of the most widely produced and used antibiotics, tetracyclines are primarily used as growth promoters and for disease treatment. Tetracyclines have high water solubility and a stable chemical structure; organisms can only metabolize approximately 30% of tetracycline antibiotics. Therefore, most incompletely metabolized tetracyclines enter water bodies as parent compounds or intermediate products. Currently, tetracycline antibiotics have been detected in aquatic environments, sediments, and soils. Long-term antibiotic residues in the environment not only lead to the proliferation and spread of drug-resistant bacteria and genes but also pose a serious threat to the structure and function of ecosystems and human health. Therefore, the removal of tetracycline antibiotics is a necessary condition for ensuring water resource security.

[0003] Extensive research has been conducted on the removal of tetracycline antibiotics that threaten ecosystems and human health. Common methods for removing tetracyclines include biological methods, adsorption, advanced oxidation methods, membrane methods, and electrochemical methods. Adsorption has been widely adopted for tetracycline removal due to its high efficiency, ease of operation, and low cost. Adsorption utilizes an adsorbent to transfer total chlorides (TCs) from the liquid phase to the adsorbent surface, offering advantages such as convenient operation, high efficiency, and low cost. The diffusion rate of tetracyclines from the bulk liquid phase to the adsorbent surface is directly proportional to the tetracycline concentration and the specific surface area of ​​the adsorbent; the diffusion rate within the pores is mainly related to the adsorbent particle size. The adsorbent is crucial in adsorption. Currently, carbon-based materials, zeolites, clay minerals, and metal oxides are widely used for adsorbing tetracycline antibiotics. The discovery and design of new adsorbent materials has become a research hotspot for the effective removal of antibiotics from the aquatic environment.

[0004] Zeolite-like imidazole ester framework materials (ZIFs), as a typical class of MOFs, possess characteristics such as high specific surface area, large porosity, high chemical and hydrothermal stability, tunable structure, and open metal sites, making them widely used in wastewater treatment. However, because ZIFs are mainly microporous with a simple pore structure, their adsorption performance for organic pollutants is relatively poor. Furthermore, synthesized ZIFs are in powder form, resulting in poor separation performance in aqueous solutions and difficulties in recovery when used in wastewater treatment, further limiting their application in the adsorption field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent, its preparation method, and its application. A magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure, high specific surface area, and abundant active sites is prepared using a solvothermal and room-temperature aqueous phase synthesis method. This adsorbent exhibits excellent rapid separation, reusability, chemical stability, and adsorption performance.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent includes the following steps:

[0008] Step 1: Disperse 5-8g of ferric chloride hexahydrate and 1-3g of trisodium citrate in 100-150mL of ethylene glycol, stir until dissolved, then add 6-10g of sodium acetate and stir vigorously until completely dissolved. Pour the mixture into a polytetrafluoroethylene liner of a stainless steel high-pressure reactor and place it in an oven at 180-200℃ for 10-12h. After cooling to room temperature, wash and dry the resulting black product to obtain magnetic Fe3O4 nanospheres.

[0009] Step 2: Add 0.5–3 g of the magnetic Fe3O4 nanospheres prepared in Step 1 to 100–150 mL of 0.1 mol / L hydrochloric acid solution, sonicate for 10–20 min, and then rinse with ultrapure water until neutral.

[0010] The treated magnetic Fe3O4 nanospheres were added to a mixed solution of 400-420 mL ethanol, ultrapure water and NH3-H2O, and ultrasonically vibrated for 10-20 min until homogeneous. Then, 1-4 mL of tetraethyl orthosilicate was added to the mixed solution, and the mixture was stirred for 12 h. The magnetic precipitate was collected, washed and dried to obtain magnetic Fe3O4@SiO2.

[0011] Step 3: Dissolve 2.5-5g of zinc acetate dihydrate or 2.7-6g of cobalt acetate tetrahydrate in 10-30mL of ultrapure water, then add 2-5g of Fe3O4@SiO2 particles prepared in Step 2, and stir to form a homogeneous solution;

[0012] Step 4: Add 9-12g of polydiallyldimethylammonium chloride to 90-120mL of ultrapure water and stir until dissolved. Then add 12.5-15g of dimethylimidazole and stir until well mixed.

[0013] Step 5: At room temperature, add the solution prepared in Step 3 dropwise to the solution prepared in Step 4 and stir for 24-36 hours. Then centrifuge, wash, and dry to obtain magnetic H-Fe3O4@SiO2@ZIFs.

[0014] The present invention also has the following technical features:

[0015] Preferably, the vigorous stirring speed in step one is 1000 rpm, and the stirring time is 30 to 60 minutes.

[0016] Preferably, the volume ratio of ethanol, ultrapure water and NH3-H2O in the mixed solution of ethanol, ultrapure water and NH3-H2O in step two is 64:16:1.

[0017] Preferably, the washing described in steps one, two and five involves washing with ethanol and ultrapure water 3 to 5 times respectively.

[0018] Preferably, the drying process described in steps one, two, and five is vacuum drying at 60°C for 10–12 hours.

[0019] Preferably, the molecular weight of the polydiallyl dimethyl ammonium chloride is 200,000 to 350,000.

[0020] Preferably, the stirring speed in steps one, two, three, four and five is 450 to 650 rpm;

[0021] The stirring time for steps one, three and four is 30 to 60 minutes.

[0022] This invention also protects a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared by the method described above, and its application method, which includes the following steps:

[0023] S1, the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent is added to an aqueous solution of a drug with a concentration of 20-80 mg / L at a mass ratio of 1-20:1 to adsorb the drug. The pH of the aqueous solution of the drug is 2-12.

[0024] S2. After the drug is completely adsorbed, the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent is separated using an external magnetic field.

[0025] Preferably, the mass ratio of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent to the drug is 3 to 10:1;

[0026] The pH of the aqueous solution of the drug is 4 to 8.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] The preparation method of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent of this invention can be completed by solvothermal and room temperature aqueous phase synthesis. The preparation process is very simple, highly operable, and easy to mass-produce. The material has a high specific surface area, excellent hierarchical pore structure and high structural tunability, as well as a large number of active sites. It has a high adsorption capacity and adsorption capacity for tetracycline antibiotics and has broad application prospects in pharmaceutical wastewater treatment.

[0029] The magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent of this invention possesses excellent magnetic properties. Under an applied magnetic field, the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent can be rapidly separated and recovered from the solution, exhibiting excellent rapid separation, reusability, and chemical stability. It overcomes the difficulty in recovery of traditional powder adsorbents and avoids the decrease in pore structure and specific surface area of ​​magnetic MOF composite adsorbents. It can efficiently adsorb drugs such as tetracycline hydrochloride and diclofenac sodium, and can be widely applied in various wastewater treatment fields, possessing excellent economic and environmental benefits. Attached Figure Description

[0030] Figure 1 Scanning electron microscope images of Fe3O4@SiO2 nanoparticles, ZIFs nanoparticles, and magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 1;

[0031] Figure 2 The hysteresis curve of the H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 2;

[0032] Figure 3 The graph shows the change in the adsorption performance of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 2 for tetracycline hydrochloride over time.

[0033] Figure 4 The nitrogen adsorption-desorption isotherm of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 3;

[0034] Figure 5 The pore size distribution diagram of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 3;

[0035] Figure 6 The graph shows the adsorption performance of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in Example 3 on tetracycline hydrochloride at different pH values. Detailed Implementation

[0036] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0037] The molecular weight range of polydiallyl dimethyl ammonium chloride used in the following examples is 200,000 to 350,000.

[0038] Example 1

[0039] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0040] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 5g of ferric chloride hexahydrate and 1g of trisodium citrate using an electronic balance, add them to 100mL of ethylene glycol solution and stir until dissolved. Then add 6g of sodium acetate and stir vigorously at 1000rpm for 30min until completely dissolved. Place the above solution in a 150mL stainless steel autoclave lined with polytetrafluoroethylene and react at 200℃ in an oven for 10h. After cooling to room temperature, the resulting black product is washed three times with ethanol and ultrapure water respectively, and then vacuum dried at 60℃ for 12h to obtain magnetic Fe3O4 nanospheres.

[0041] Step 2: Preparation of magnetic Fe3O4@SiO2: 1.0 g of magnetic Fe3O4 microspheres prepared in Step 1 were ultrasonically vibrated for 10 min with 100 mL of 0.1 mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0042] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 316 mL ethanol, 79 mL ultrapure water and 5.0 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 10 min. Then, 2 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred at 450 rpm for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed 4 times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 12 h to obtain magnetic Fe3O4@SiO2.

[0043] Step 3: Prepare metal salt solution: Weigh 2.5g of zinc acetate dihydrate and 2g of Fe3O4@SiO2 separately using an electronic balance and place them in 10mL of ultrapure water. Stir at 450rpm for 30min until dissolved to form a homogeneous solution.

[0044] Step 4: Prepare the organic ligand solution: Weigh 9g of polydiallyldimethylammonium chloride using an electronic balance and place it in 90mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 12.5g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 450rpm for 30min until the mixture is homogeneous.

[0045] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 450 rpm, the metal salt solution prepared in Step 3 is slowly added to the organic ligand solution prepared in Step 4 using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 24 h, centrifugation and washing are performed, and then vacuum drying is carried out at 60 °C for 12 h to obtain magnetic H-Fe3O4@SiO2@ZIFs.

[0046] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride and sodium dichlorophenate, specifically including the following steps:

[0047] 10 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 100 mL of tetracycline hydrochloride and sodium diclofenac solution, respectively. The concentrations of both tetracycline hydrochloride and sodium diclofenac solution were 20 mg / L, and the pH of the solution was 4.5. The adsorption reaction was carried out at 25 °C for 24 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentrations of tetracycline hydrochloride and sodium diclofenac were determined by ultraviolet spectrophotometer. The remaining contents of tetracycline hydrochloride and sodium diclofenac were calculated based on the standard curves of tetracycline hydrochloride and sodium diclofenac, respectively. The adsorption efficiencies of tetracycline hydrochloride and sodium diclofenac were calculated to be 50% and 88%, respectively.

[0048] Scanning electron microscope (SEM) images of the Fe3O4@SiO2 nanoparticles, ZIFs nanoparticles, and magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment are shown below. Figure 1 As shown, Figure 1 (a) Shows an irregular ellipsoidal shape in the magnetic Fe3O4@SiO2 path. Figure 1 (b) shows that the ZIF nanoparticles are irregularly spherical. Figure 1 (c) The microscale of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent is significantly larger than that of Fe3O4@SiO2 and ZIFs nanoparticles.

[0049] Example 2

[0050] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0051] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 7.5g of ferric chloride hexahydrate and 1.3g of trisodium citrate using an electronic balance, add them to 150mL of ethylene glycol solution and stir until dissolved. Then add 8.5g of sodium acetate. Stir vigorously for 30min until completely dissolved. Place the above solution in a 200mL polytetrafluoroethylene-lined stainless steel autoclave and react at 200℃ for 12h. After cooling to room temperature, the resulting black product is washed four times with ethanol and ultrapure water, respectively, and then vacuum dried at 60℃ for 10h to obtain magnetic Fe3O4 nanospheres.

[0052] Step 2: Preparation of magnetic Fe3O4@SiO2: The above 2.0g magnetic Fe3O4 microspheres were ultrasonically vibrated for 20min with 120mL of 0.1mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0053] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 331 mL ethanol, 83 mL ultrapure water and 5 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 20 min. Then, 2.5 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred at 650 rpm for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed three times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 10 h to obtain magnetic Fe3O4@SiO2.

[0054] Step 3: Prepare the metal salt solution: Weigh 3g of zinc acetate dihydrate and 3.5g of Fe3O4@SiO2 separately using an electronic balance and place them in 15mL of ultrapure water. Stir at 650rpm for 30min until dissolved to form a homogeneous solution.

[0055] Step 4: Prepare the organic ligand solution: Weigh 9g of polydiallyldimethylammonium chloride using an electronic balance and place it in 100mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 14g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 650rpm for 30min until the mixture is homogeneous.

[0056] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 500 rpm, the metal salt solution is slowly added to the organic ligand solution using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 30 h, centrifugation and washing are performed, and then vacuum drying is carried out at 60℃ for 10 h to obtain magnetic H-Fe3O4@SiO2@ZIFs.

[0057] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride, specifically including the following steps:

[0058] 15 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 150 mL of tetracycline hydrochloride solution. The concentration of tetracycline hydrochloride solution was 60 mg / L and the pH value was 6. The adsorption reaction was carried out at 30 °C for 24 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentration of tetracycline hydrochloride was determined by ultraviolet spectrophotometer. The remaining tetracycline hydrochloride content was calculated based on the drawn tetracycline hydrochloride standard curve, and the adsorption efficiency of tetracycline hydrochloride was calculated. The adsorption efficiency of tetracycline hydrochloride was 90%.

[0059] The hysteresis curve of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment is as follows: Figure 2 As shown, from Figure 2 It can be seen that the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent has a certain response to external magnetic fields and has a certain degree of magnetism, indicating that the design and synthesis of MOF-based magnetic microsphere adsorbents has certain advantages in recycling.

[0060] The adsorption performance of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment for tetracycline hydrochloride changes over time as follows: Figure 3 As shown, from Figure 3 As can be seen, within the range of 0-24h, the adsorption efficiency of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent for tetracycline hydrochloride shows a trend of first increasing and then leveling off over time.

[0061] Example 3

[0062] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0063] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 6g of ferric chloride hexahydrate and 1g of trisodium citrate using an electronic balance, add them to 60mL of ethylene glycol solution and stir until dissolved. Then add 3.5g of sodium acetate and stir vigorously at 1000rpm for 60min until completely dissolved. Place the above solution in a 100mL polytetrafluoroethylene-lined stainless steel autoclave and react at 290℃ for 12h. After cooling to room temperature, the resulting black product is washed 5 times with ethanol and ultrapure water respectively, and then vacuum dried at 60℃ for 11h to obtain magnetic Fe3O4 nanospheres.

[0064] Step 2: Preparation of magnetic Fe3O4@SiO2: 1.5 g of magnetic Fe3O4 microspheres prepared in Step 1 were ultrasonically vibrated for 10 min with 110 mL of 0.1 mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0065] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 323 mL ethanol, 81 mL ultrapure water and 5 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 20 min. Then, 2 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred at 550 rpm for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed 5 times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 11 h to obtain magnetic Fe3O4@SiO2.

[0066] Step 3: Prepare metal salt solution: Weigh 5g of zinc acetate dihydrate and 2.5g of Fe3O4@SiO2 into 12mL of ultrapure water using an electronic balance, stir at 550rpm for 40min until dissolved to form a homogeneous solution;

[0067] Step 4: Prepare the organic ligand solution: Weigh 10g of polydiallyldimethylammonium chloride using an electronic balance and place it in 95mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 13g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 550rpm for 40min until the mixture is homogeneous.

[0068] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 600 rpm, the metal salt solution is slowly added to the organic ligand solution using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 24 hours, the solution is centrifuged and washed, and then vacuum dried at 60℃ for 11 hours to obtain magnetic H-Fe3O4@SiO2@ZIFs.

[0069] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride and sodium dichlorophenate, specifically including the following steps:

[0070] 20 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 150 mL of tetracycline hydrochloride solution. The concentration of tetracycline hydrochloride solution was 40 mg / L and the pH value of the solution was 4. The adsorption reaction was carried out at 25℃ for 24 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentration of tetracycline hydrochloride was measured by ultraviolet spectrophotometer. The remaining tetracycline hydrochloride content was calculated based on the standard curve of tetracycline hydrochloride, and the adsorption efficiency of tetracycline hydrochloride was calculated. The adsorption efficiency of tetracycline hydrochloride was 92%.

[0071] The nitrogen adsorption-desorption isotherm of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment is as follows: Figure 4 As shown, from Figure 4It can be seen that the nitrogen adsorption-desorption isotherm of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent exhibits type-IV characteristics.

[0072] The pore size distribution diagram of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment is shown in the figure below. Figure 5 As shown, from Figure 5 It can be seen that the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent has a hierarchical porous structure, which is beneficial to the adsorption of pollutants.

[0073] The adsorption performance of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment for tetracycline hydrochloride at different pH values ​​is shown in the figure below. Figure 6 As shown, from Figure 6 As can be seen from the data, within the range of 3-12 h, the adsorption efficiency of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent for tetracycline hydrochloride shows a trend of first increasing and then decreasing with increasing pH.

[0074] Example 4

[0075] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0076] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 8g of ferric chloride hexahydrate and 3g of trisodium citrate using an electronic balance, add them to 140mL of ethylene glycol solution and stir until dissolved. Then add 10g of sodium acetate and stir vigorously at 1000rpm for 40min until completely dissolved. Place the above solution in a 200mL polytetrafluoroethylene-lined stainless steel autoclave and react at 180℃ for 11h. After cooling to room temperature, the resulting black product is washed three times with ethanol and ultrapure water respectively, and then vacuum dried at 60℃ for 12h to obtain magnetic Fe3O4 nanospheres.

[0077] Step 2: Preparation of magnetic Fe3O4@SiO2: The above 3.0g magnetic Fe3O4 microspheres were ultrasonically vibrated for 15min with 150mL of 0.1mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0078] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 323 mL ethanol, 81 mL ultrapure water and 5 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 15 min. Then, 4 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed three times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 11 h to obtain magnetic Fe3O4@SiO2.

[0079] Step 3: Prepare metal salt solution: Weigh 3g of cobalt acetate tetrahydrate and 3g of Fe3O4@SiO2 into 15mL of ultrapure water using an electronic balance, and stir at 550rpm for 40min until the mixture is homogeneous.

[0080] Step 4: Prepare the organic ligand solution: Weigh 12g of polydiallyldimethylammonium chloride using an electronic balance and place it in 120mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 15g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 450rpm for 60min until the mixture is homogeneous.

[0081] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 650 rpm, the metal salt solution is slowly added to the organic ligand solution using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 36 h, centrifugation and washing are performed, and then vacuum drying is carried out at 60 °C for 12 h to obtain the magnetic H-Fe3O4@SiO2@ZIFs.

[0082] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride and sodium dichlorophenate, specifically including the following steps:

[0083] 30 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 150 mL of tetracycline hydrochloride solution. The concentration of tetracycline hydrochloride solution was 80 mg / L and the pH value was 8. The adsorption reaction was carried out at 35℃ for 20 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentration of tetracycline hydrochloride was measured by ultraviolet spectrophotometer. The remaining tetracycline hydrochloride content was calculated based on the standard curve of tetracycline hydrochloride, and the adsorption efficiency of tetracycline hydrochloride was calculated. The adsorption efficiency of tetracycline hydrochloride was 93%.

[0084] The adsorption performance of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared in this embodiment for tetracycline hydrochloride is shown in Table 1. As can be seen from Table 1, within the temperature range of 25-35℃, the adsorption efficiency of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent for tetracycline hydrochloride increases with increasing temperature.

[0085] Table 1 Adsorption capacity of tetracycline hydrochloride at different temperatures

[0086]

[0087] Example 5

[0088] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0089] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 8g of ferric chloride hexahydrate and 3g of trisodium citrate using an electronic balance, add them to 140mL of ethylene glycol solution and stir until dissolved. Then add 10g of sodium acetate and stir vigorously at 1000rpm for 40min until completely dissolved. Place the above solution in a 200mL polytetrafluoroethylene-lined stainless steel autoclave and react at 180℃ for 11h. After cooling to room temperature, the resulting black product is washed three times with ethanol and ultrapure water respectively, and then vacuum dried at 60℃ for 12h to obtain magnetic Fe3O4 nanospheres.

[0090] Step 2: Preparation of magnetic Fe3O4@SiO2: The above 0.5g magnetic Fe3O4 microspheres were ultrasonically vibrated for 15min with 150mL of 0.1mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0091] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 323 mL ethanol, 81 mL ultrapure water and 5 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 15 min. Then, 1 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed three times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 11 h to obtain magnetic Fe3O4@SiO2.

[0092] Step 3: Prepare metal salt solution: Weigh 2.7g of cobalt acetate tetrahydrate and 4g of Fe3O4@SiO2 separately using an electronic balance and place them in 30mL of ultrapure water. Stir at 550rpm for 60min until the mixture is homogeneous.

[0093] Step 4: Prepare the organic ligand solution: Weigh 12g of polydiallyldimethylammonium chloride using an electronic balance and place it in 120mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 15g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 450rpm for 60min until the mixture is homogeneous.

[0094] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 650 rpm, the metal salt solution is slowly added to the organic ligand solution using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 36 h, centrifugation and washing are performed, and then vacuum drying is carried out at 60 °C for 12 h to obtain the magnetic H-Fe3O4@SiO2@ZIFs.

[0095] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride and sodium dichlorophenate, specifically including the following steps:

[0096] 20 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 100 mL of tetracycline hydrochloride solution. The concentration of tetracycline hydrochloride solution was 20 mg / L and the pH value was 12. The adsorption reaction was carried out at 35℃ for 20 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentration of tetracycline hydrochloride was measured by ultraviolet spectrophotometer. The remaining tetracycline hydrochloride content was calculated based on the drawn tetracycline hydrochloride standard curve, and the adsorption efficiency of tetracycline hydrochloride was calculated. The adsorption efficiency of tetracycline hydrochloride was 88%.

[0097] Example 6

[0098] A method for preparing a magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent with a hierarchical porous structure includes the following steps:

[0099] Step 1: Preparation of magnetic Fe3O4 nanospheres: Weigh 8g of ferric chloride hexahydrate and 3g of trisodium citrate using an electronic balance, add them to 140mL of ethylene glycol solution and stir until dissolved. Then add 10g of sodium acetate and stir vigorously at 1000rpm for 40min until completely dissolved. Place the above solution in a 200mL polytetrafluoroethylene-lined stainless steel autoclave and react at 180℃ for 11h. After cooling to room temperature, the resulting black product is washed three times with ethanol and ultrapure water respectively, and then vacuum dried at 60℃ for 12h to obtain magnetic Fe3O4 nanospheres.

[0100] Step 2: Preparation of magnetic Fe3O4@SiO2: The above 3.0g magnetic Fe3O4 microspheres were ultrasonically vibrated for 15min with 150mL of 0.1mol / L HCl solution, and then rinsed with ultrapure water until neutral.

[0101] The magnetic Fe3O4 microspheres were then placed in a mixed solution of 323 mL ethanol, 81 mL ultrapure water and 5 mL NH3-H2O solution (25-28 w / w%) and ultrasonically vibrated for 15 min. Then, 4 mL of tetraethyl orthosilicate (TEOS) solution was added to the above mixed solution and stirred for 12 h. The magnetic particles obtained from the reaction were collected with a magnet, washed three times with ethanol and ultrapure water respectively, and vacuum dried at 60 °C for 11 h to obtain magnetic Fe3O4@SiO2.

[0102] Step 3: Prepare metal salt solution: Weigh 6g of cobalt acetate tetrahydrate and 5g of Fe3O4@SiO2 separately using an electronic balance and place them in 25mL of ultrapure water. Stir at 550rpm for 40min until the mixture is homogeneous.

[0103] Step 4: Prepare the organic ligand solution: Weigh 12g of polydiallyldimethylammonium chloride using an electronic balance and place it in 120mL of ultrapure water. Stir until dissolved to form a homogeneous solution. Then, weigh 15g of dimethylimidazole using an electronic balance and add it to the above solution. Stir at 450rpm for 50min until the mixture is homogeneous.

[0104] Step 5: Magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent: Under a stirring speed of 650 rpm, the metal salt solution is slowly added to the organic ligand solution using a dropper. After the droplet addition process is completed, a light pink milky solution is formed. After stirring for 36 h, centrifugation and washing are performed, and then vacuum drying is carried out at 60 °C for 12 h to obtain the magnetic H-Fe3O4@SiO2@ZIFs.

[0105] The magnetic H-Fe3O4@SiO2@ZIFs prepared above are used to adsorb tetracycline hydrochloride and sodium dichlorophenate, specifically including the following steps:

[0106] 16 mg of magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent was weighed and added to 200 mL of tetracycline hydrochloride solution. The concentration of tetracycline hydrochloride solution was 80 mg / L and the pH value was 2. The adsorption reaction was carried out at 35℃ for 20 h. After adsorption saturation, separation was performed using an external magnetic field. The supernatant was filtered through a membrane and the concentration of tetracycline hydrochloride was measured by ultraviolet spectrophotometer. The remaining tetracycline hydrochloride content was calculated based on the standard curve of tetracycline hydrochloride, and the adsorption efficiency of tetracycline hydrochloride was calculated. The adsorption efficiency of tetracycline hydrochloride was 90%.

[0107] The hierarchical porous magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent provided by this invention features simple operation, low cost, easy recovery, and low toxicity of raw materials used in its preparation. It can be mass-produced and possesses good environmental safety. More importantly, these hierarchical porous magnetic H-Fe3O4@SiO2@ZIFs composite adsorbents all possess a hierarchical porous structure, high specific surface area, and abundant active sites. The magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent prepared by this invention for the adsorption of tetracycline hydrochloride is simple to operate, easy to use, has high adsorption efficiency, large adsorption capacity, and is easy to recover, demonstrating strong advantages in treating antibiotic wastewater.

Claims

1. Use of a magnetic H-Fe304@Si02@ZIFs composite adsorbent, characterized in that, The application relates to a method for efficiently adsorbing and removing drugs in wastewater, and the drugs are tetracycline hydrochloride and diclofenac sodium. The preparation method of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent comprises the following steps: Step one: 5-8 g of iron chloride hexahydrate and 1-3 g of trisodium citrate are dispersed in 100-150 mL of ethylene glycol, stirring is conducted until the two are dissolved, then 6-10 g of sodium acetate is added, and the mixture is stirred vigorously until the sodium acetate is completely dissolved; the mixture is poured into a polytetrafluoroethylene lining in a stainless steel high-pressure reaction kettle, and the kettle is placed in an oven and reacted at 180-200 DEG C for 10-12 h; after the mixture is cooled to room temperature, the obtained black product is washed and dried to obtain magnetic Fe3O4 nanospheres; Step two: 0.5-3 g of the magnetic Fe3O4 nanospheres prepared in step one are added into 100-150 mL of a hydrochloric acid solution with a concentration of 0.1 mol / L, and ultrasonic oscillation is conducted for 10-20 min; then the magnetic Fe3O4 nanospheres are washed with ultrapure water until the magnetic Fe3O4 nanospheres are neutralized; The treated magnetic Fe3O4 nanospheres are added into a mixed solution of 400-420 mL of ethanol, ultrapure water and NH3-H2O, and ultrasonic oscillation is conducted for 10-20 min until the magnetic Fe3O4 nanospheres are uniformly distributed in the mixed solution; then 1-4 mL of tetraethyl orthosilicate is added into the mixed solution, and stirring reaction is conducted for 12 h; the magnetic precipitate is collected, washed and dried to obtain magnetic Fe3O4@SiO2; Step three: 2.5-5 g of zinc acetate dihydrate or 2.7-6 g of cobalt acetate tetrahydrate is dissolved in 10-30 mL of ultrapure water, and then 2-5 g of the Fe3O4@SiO2 particles prepared in step two are added into the solution; the mixture is stirred to form a uniform solution; Step four: 9-12 g of polydiallyldimethylammonium chloride is added into 90-120 mL of ultrapure water and stirred until the polydiallyldimethylammonium chloride is dissolved; then 12.5-15 g of 2-methylimidazole is added into the solution and stirred until the 2-methylimidazole is uniformly mixed with the solution; Step five: under the condition of room temperature, the solution prepared in step three is added dropwise into the solution prepared in step four, and stirring reaction is conducted for 24-36 h; then the solution is centrifuged, washed and dried to obtain the magnetic H-Fe3O4@SiO2@ZIFs.

2. The use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, In step one, the stirring speed is 1000 rpm, and the stirring time is 30-60 min.

3. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, In step two, the volume ratio of ethanol, ultrapure water and NH3-H2O in the mixed solution is 64:16:

1.

4. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, In steps one, two and five, the washing is performed by using ethanol and ultrapure water for 3-5 times respectively.

5. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, In steps one, two and five, the drying is performed at 60 DEG C under vacuum for 10-12 h.

6. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, The molecular weight of the polydiallyldimethylammonium chloride is 200000-350000.

7. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, In steps one, two, three, four and five, the stirring speed is 450-650 rpm; in steps one, three and four, the stirring time is 30-60 min.

8. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 1, characterized in that, The method comprises the following steps: S1, according to the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent and drug mass ratio 1~20:1, it is added to the drug concentration is 20~80 mg / L in the aqueous solution of drug and carries out adsorption to the drug, wherein the pH of the aqueous solution of drug is 2~12; S2, after the drug adsorption is complete, the external magnetic field is separated magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent.

9. Use of the magnetic H-Fe304@Si02@ZIFs composite adsorbent according to claim 8, characterized in that, The mass ratio of the magnetic H-Fe3O4@SiO2@ZIFs composite adsorbent and the drug is 3~10:1; The pH of the aqueous solution of the drug is 4~8.

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