A method for preparing UiO-66-SO3H for adsorbing tetracycline and its application

Abstract

The application discloses a preparation method and application of a tetracycline adsorbing UiO-66-SO3H, and belongs to the technical field of water pollution control. The application synthesizes a novel adsorbent UiO-66-SO3H through sulfonation of UiO-66, and the adsorbent exhibits excellent tetracycline adsorption efficiency in wastewater treatment. Through scanning electron microscopy, thermogravimetric analysis, XPS and other characterization technologies, it is confirmed that sulfonic acid groups are successfully grafted onto the UiO-66 framework, and the framework structure and thermal stability remain unchanged. The adsorption capacity of the UiO-66-SO3H can reach more than 200 mg / g, which is much higher than that of the original UiO-66. The material performs excellently in a complex water system containing coexisting ions (Na + , K + , Ca² + , Mg² + ) and humic acid, and the applicable pH range is 8-11. The preparation method is simple to operate, low in production cost, and has remarkable environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to a method for preparing UiO-66-SO3H for adsorbing tetracycline and its application. Background Technology

[0002] Antibiotics are widely used in medicine, agriculture, animal husbandry, and aquaculture due to their low cost and strong antibacterial activity, with an annual consumption of 100,000 to 200,000 tons. Although antibiotics play a crucial role in protecting human and animal health, their overuse has led to increasingly prominent environmental pollution problems. Among them, tetracycline (TC), a polar, ionizable, broad-spectrum antibiotic, accounts for about 20% of the total antibiotic consumption, and its residues in water bodies have become a global pollution problem. Therefore, developing efficient and environmentally friendly tetracycline removal technologies is of great significance for water resource protection and ecological security.

[0003] Currently, commonly used technologies in wastewater treatment mainly include biodegradation, membrane separation, catalytic oxidation, and adsorption. Among these, adsorption has received widespread attention in the field of wastewater treatment due to its advantages such as high cost-effectiveness, simple operation, and ability to remove multiple pollutants simultaneously. Studies have reported various adsorbents for tetracycline adsorption, such as carbon materials, molecular sieves, and metal-organic frameworks (MOFs). MOFs exhibit excellent performance in adsorbing organic pollutants due to their precise structure, high specific surface area, tunable pore configuration, and ease of preparation. However, the application of these materials in aquatic environments is limited by their structural stability. Strong coordination bonds can effectively improve the thermodynamic and kinetic stability of the materials, thereby resisting bond destruction caused by hydrolysis.

[0004] Among the many reported MOFs, zirconium-based materials, represented by UiO-66, possess excellent chemical, hydrothermal, thermal, and mechanical stability. However, they still suffer from limitations such as limited active sites, low adsorption capacity, and poor selectivity, which restrict their application in wastewater treatment. To improve their adsorption performance, functional group modification to enhance the surface properties of UiO-66 has become a research focus. Therefore, researching a UiO-66 adsorbent with functional group modification can greatly improve its adsorption performance, with a simple and convenient adsorption process, unaffected by water pH or tetracycline concentration, and possessing anti-interference adsorption properties. This is of significant scientific value and practical importance for solving the current problem of antibiotic pollution control, breaking through the practical application bottlenecks of existing MOF-based adsorbents, and promoting the transformation of efficient water treatment technologies from laboratory research to engineering applications. Summary of the Invention

[0005] To address the problems existing in related technologies, the primary objective of this invention is to provide a method for preparing UiO-66-SO3H for tetracycline adsorption. This method involves synthesizing UiO-66 via a hydrothermal process, introducing sulfonic acid groups (-SO3H) onto the molecule to enhance electrostatic attraction and hydrogen bonding with tetracycline molecules. Simultaneously, ligand-metal node coordination increases the number of adsorption sites, thereby optimizing its adsorption performance for tetracycline. The specific preparation method is as follows: (1) The zirconium source and organic ligand were dissolved in a mixture of 24 mL DMF (N,N-dimethylformamide) and 1.34 mL hydrochloric acid. The solution was then transferred to a 100 mL hydrothermal reactor and heated at 140 °C for synthesis.

[0006] (2) After the hydrothermal reactor is cooled, solid UiO-66-SO3H is collected by vacuum filtration and washed three times with DMF and methanol respectively. After drying in a vacuum drying oven at 75°C, UiO-66-SO3H is obtained.

[0007] Preferably, the zirconium source in this method is zirconium oxychloride octahydrate; the organic ligand is one of terephthalic acid and sodium 2-sulfonic acid terephthalate monosodium.

[0008] Preferably, the molar ratio of the zirconium source to the organic ligand in this method is 10:(1-5).

[0009] Another object of the present invention is to provide the application of the UiO-66-SO3H in the adsorption of tetracycline in water, specifically including the following steps: The UiO-66-SO3H was dispersed in water containing water pollutants, and after stirring, an adsorption test was conducted, which showed that the water pollutants could be removed.

[0010] Preferably, the water pollutant described in this invention is a tetracycline antibiotic, and the initial concentration of the water pollutant is 20-60 mg / L.

[0011] Preferably, the water used in the application of the present invention is tap water, deionized water, or ultrapure water.

[0012] The beneficial effects of this invention are: (1) By grafting sulfonic acid groups onto UiO-66, the present invention can effectively enhance the hydrophilicity and stability of metal-organic frameworks, improve their dispersibility, ion selectivity, adsorption capacity and ion conductivity modification in aqueous solution, enhance electrostatic attraction and hydrogen bonding with tetracycline molecules, and increase adsorption sites through ligand-metal node coordination, thereby optimizing its adsorption performance for tetracycline, and the adsorption capacity exceeds 200 mg / g.

[0013] (2) The UiO-66-SO3H prepared by the present invention has high site utilization and excellent adsorption capacity per unit mass, and can achieve efficient pollutant removal under low dosage conditions, which reflects its significant advantages as a high-performance adsorption material.

[0014] (3) When Na + and K + When ions coexist with UiO-66-SO3H, the adsorption of tetracycline by UiO-66-SO3H can be promoted by π-π stacking, providing a new approach for the efficient removal of antibiotics in complex water bodies.

[0015] (4) The UiO-66-SO3H prepared by this invention maintains stable and efficient adsorption performance over a wide pH range, has excellent anti-interference adsorption performance, and has good water quality adaptability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the adsorption capacity of tetracycline for different sulfonic acid group contents in Example 1 of the present invention.

[0017] Figure 2 This is a characterization of UiO-66 and UiO-66-SO3H in Embodiment 1 of the present invention; Figure 2 (a) Figure 2 (b) is a scanning electron microscope image of UiO-66-SO3H; Figure 2 (c) Figure 2 (d) is a scanning electron microscope image of UiO-66; Figure 2 (e) is the energy spectrum analysis diagram of UiO-66-SO3H.

[0018] Figure 3 XPS images of the UiO-66 and UiO-66-SO3H samples in Example 1 of this invention: Figure 3 (a) is the full spectrum. Figure 3 (b) is the Zr 3d spectrum of UiO-66. Figure 3 (c) is the C 1s spectrum of UiO-66. Figure 3 (d) is the O 1s spectrum of UiO-66. Figure 3 (e) is the Zr 3d spectrum of UiO-66-SO3H. Figure 3 (f) is the C 1s spectrum of UiO-66-SO3H. Figure 3 (g) is the N 1s spectrum of UiO-66-SO3H. Figure 3 (h) is the O 1s spectrum of UiO-66-SO3H. Figure 3 (i) is the S 2p spectrum of UiO-66-SO3H.

[0019] Figure 4 This is the thermogravimetric curve of the adsorbent in Example 1 of the present invention, wherein... Figure 4 (a) is the thermogravimetric curve of UiO-66. Figure 4 (b) is the thermogravimetric curve of UiO-66-SO3H.

[0020] Figure 5 This describes the effect of the initial pH value of tetracycline on the adsorption performance of UiO-66-SO3H in Example 2 of this invention.

[0021] Figure 6 This describes the effect of the initial tetracycline concentration on the adsorption performance of UiO-66-SO3H in Example 3 of this invention. Figure 6 (a) represents the adsorption capacity; Figure 6 (b) represents the removal rate.

[0022] Figure 7 This describes the effect of the amount of UiO-66-SO3H on the adsorption performance in Example 4 of this invention. Figure 7 (a) represents the adsorption capacity; Figure 7 (b) represents the removal rate.

[0023] Figure 8 This describes the effect of coexisting ions on the adsorption capacity of UiO-66-SO3H in Example 5 of the present invention.

[0024] Figure 9 This describes the effect of humic acid on the adsorption of tetracycline by UiO-66-SO3H in Example 6 of the present invention.

[0025] Figure 10 This describes the adsorption performance of UiO-66-SO3H on tetracycline in different water bodies in Example 7 of this invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, but the scope of protection of the present invention is not limited thereto.

[0027] Example 1 The preparation method of UiO-66-SO3H of the present invention is as follows: (1) 1.0 g of ZrOCl2·8H2O (3 mmol) was dissolved in a mixture of 24 mL DMF and 1.34 mL hydrochloric acid, respectively, with 0.1, 0.2, 0.3, 0.4 and 0.5 g of 2-sulfonic acid monosodium terephthalate (BDC-SO3Na) added. A control was set up by adding only ZrOCl2·8H2O. The solution was transferred to a 100 mL hydrothermal reactor and heated at 140 °C for synthesis.

[0028] (2) After the hydrothermal reactor is cooled, UiO-66-SO3H is collected by vacuum filtration and washed three times with DMF and methanol respectively. After drying in a vacuum drying oven at 75°C, UiO-66-SO3H is obtained.

[0029] 100 mL of tetracycline solution was added to each of the prepared UiO-66-SO3H adsorbents in an Erlenmeyer flask. After stirring at 25 °C, adsorption experiments were conducted. After adsorption, the solution was filtered through a 0.45 μm water-permeable microporous membrane. The concentration of residual tetracycline in the solution was determined using a UV spectrophotometer (wavelength 357 nm). The results are as follows: Figure 1 As shown, when the mass ratio of zirconium source to organic ligand is 10:3, the resulting UiO-66-SO3H exhibits the best adsorption effect on tetracycline. Furthermore, after grafting sulfonic acid groups onto UiO-66, the adsorption performance for tetracycline is significantly higher than that of UiO-66.

[0030] To analyze the effect of incorporating -SO3H into UiO-66 on the adsorbent in this invention, UiO-66 was prepared in this embodiment, and its synthesis steps are as follows: (1) Dissolve 1.0g of ZrOCl2·8H2O (3mmol) and 0.3g of terephthalic acid in a mixture containing 24mL of DMF and 1.34mL of hydrochloric acid. Transfer the solution to a 100mL hydrothermal reactor and heat at 140℃ for synthesis.

[0031] (2) After the hydrothermal reactor is cooled, solid UiO-66 is collected by vacuum filtration and washed three times with DMF and methanol respectively. After drying in a vacuum drying oven at 75°C, UiO-66 is obtained.

[0032] The obtained UiO-66-SO3H and UiO-66 adsorbents were analyzed: (1) Material morphology: Figure 2 (a) and Figure 2 (b) shows the surface morphology of UiO-66-SO3H. Figure 2 (c) and Figure 2 (d) shows the surface morphology of UiO-66. No significant morphological difference was observed between UiO-66-SO3H and UiO-66, indicating that sulfonic acid modification did not alter the morphology of UiO-66; energy dispersive spectroscopy (EDS) analysis is as follows: Figure 2 As shown in (e), sulfur (S) is confirmed to be present in UiO-66-SO3H, while zirconium (Zr), carbon (C), nitrogen (N) and oxygen (O) are also uniformly distributed in UiO-66-SO3H.

[0033] (2) Chemical state: such as Figure 3 As shown in (a), UiO-66 contains only C, N, O and Zr elements, while UiO-66-SO3H additionally exhibits an S peak; Figure 3 (b, c, and d) represent the binding energy positions of the Zr 3d, C 1s, and O 1s peaks in UiO-66, respectively. Figure 3 (e, f, g, h, and i) represent the binding energy positions of the Zr 3d, C 1s, N 1s, O 1s, and S 2p peaks of UiO-66-SO3H, respectively; (Compare) Figure 3 (b) and Figure 3 (e) It can be observed that the Zr 3d peak position shifted after the introduction of the -SO3H group compared to the original peak position, indicating a change in the chemical environment of Zr; compared to Figure 3 (d) and Figure 3 (h), the change in the 1s peak position of O indicates a change in the chemical environment of oxygen, suggesting that the functionalization of the sulfonic acid group alters the coordination environment between Zr and O; in Figure 3 In (i), the S 2p spectrum shows characteristic peaks of 167.7 / 168.7 eV (S 2p1 / 2, S 2p3 / 2), indicating that the -SO3H group was successfully introduced.

[0034] (3) Thermal stability: The thermal stability of UiO-66 is as follows Figure 4 As shown in (a), the thermal stability of UiO-66-SO3H is as follows: Figure 4 As shown in (b), both materials exhibit four stages of mass loss. The first and second stages occur in the 25℃-400℃ range, which are attributed to the desorption of adsorbed water molecules, methanol and DMF. The total mass loss of UiO-66 and UiO-66-SO3H is 32.45% and 30.59%, respectively. The third and fourth stages occur in the 400℃-600℃ range. The high temperature leads to the decomposition of UiO-66 and UiO-66-SO3H, which is attributed to the cracking of the BDC linking group and the collapse of the metal-organic framework structure at temperatures above 400℃.

[0035] Example 2 The effect of initial pH value of water on tetracycline removal efficiency of UiO-66-SO3H: 100 mL of tetracycline (50 mg / L) solution and 0.2 g of UiO-66-SO3H obtained in Example 1 were added to an Erlenmeyer flask. The pH of the solution was adjusted by adding 0.5, 0.2, 0.1, and 0.001 mol / L sodium hydroxide and hydrochloric acid, respectively, to achieve pH values ​​of 2, 4, 6, 8, and 12. After stirring at 25 °C, the solution was subjected to adsorption experiments. After the adsorption process, the solution was filtered through a 0.45 μm water-permeable microporous membrane, and the concentration of residual tetracycline in the solution was determined using a UV spectrophotometer (wavelength 357 nm). The results are as follows. Figure 5 As shown, the adsorption effect of tetracycline is best when the solution pH is 8-11, and the adsorption capacity of UiO-66-SO3H for tetracycline is not significantly different within this pH range.

[0036] Example 3 Effect of initial tetracycline concentration on the adsorption performance of UiO-66-SO3H: 100 mL of tetracycline solutions with concentrations of 20, 30, 40, 45, 50, and 60 mg / L were respectively placed in conical flasks, and 20 mg of UiO-66-SO3H was added to each. Adsorption experiments were conducted by stirring at 200 rpm at 25 °C. Samples were taken at 60, 120, 240, 300, 600, and 1200 min, filtered through a 0.45 μm aqueous microporous membrane, and then measured for the remaining tetracycline concentration in the solution using a UV spectrophotometer (wavelength 357 nm). The adsorption capacity and removal rate were calculated, and the results are shown below. Figure 6 As shown, within the concentration range of 20-60 mg / L, the adsorption capacity of UiO-66-SO3H is positively correlated with the initial tetracycline concentration. When the initial tetracycline concentration is 60 mg / L, the adsorption capacity of UiO-66-SO3H exceeds 200 mg / g. This increase can be attributed to the enhanced solute gradient formed by the TC concentration gradient in the solution. This gradient ultimately enhances the driving force and leads to the improvement of adsorption capacity. The removal rate is negatively correlated with the initial tetracycline concentration. With a fixed number of active sites on the adsorbent, at low initial concentrations, there are sufficient active sites, and TC molecules can be quickly adsorbed, resulting in a high removal rate. As the initial concentration increases, the active sites quickly become saturated, the proportion of unadsorbed TC increases, and the removal rate decreases.

[0037] Example 4 Effect of adsorbent dosage on the adsorption performance of UiO-66-SO3H: Seven 100 mL aliquots of tetracycline solution with a concentration of 50 mg / L were added to conical flasks. 10 mg (0.1 g / L), 15 mg (0.15 g / L), 20 mg (0.2 g / L), 25 mg (0.25 g / L), 30 mg (0.3 g / L), 35 mg (0.35 g / L), and 40 mg (0.4 g / L) of UiO-66-SO3H adsorbent were added to each flask. Adsorption experiments were conducted at 25 °C with stirring (200 rpm). Samples were taken at 60, 120, 240, 300, 600, 1200, and 1400 min, filtered through a 0.45 μm aqueous microporous membrane, and then analyzed using a UV spectrophotometer (wavelength 357 nm) to determine the remaining tetracycline concentration in the solution. The adsorption capacity and removal rate were calculated, and the results are shown below. Figure 7As shown, the adsorption capacity for tetracycline was highest when the concentration of UiO-66-SO3H in the water was 0.1 g / L; the removal rate of tetracycline was best when the concentration of UiO-66-SO3H in the water was 0.4 g / L, indicating that the higher the dosage of UiO-66-SO3H, the more adsorption sites it can provide, thereby improving the TC removal efficiency. However, due to the limited TC concentration in the system, the upper limit of the total number of adsorption sites, and the tendency of the adsorbent to aggregate at high dosages, the adsorption capacity of UiO-66-SO3H was eventually reduced. Therefore, the adsorbent concentration used in the subsequent tests was 0.25 g / L.

[0038] Example 5 Effect of coexisting ions on the adsorption capacity of UiO-66-SO3H: 100 mL of a 50 mg / L tetracycline solution was placed in an Erlenmeyer flask. Different masses of NaCl, KCl, MaCl2, and CaCl2 were added to the tetracycline solution to achieve concentrations of 0, 0.025, 0.05, 0.075, and 0.1 mol / L, respectively. The mixed solution was adjusted to an initial pH of 10. 25 mg of UiO-66-SO3H was added to each flask, and the mixture was stirred at 200 rpm at 25°C until adsorption equilibrium was reached. After adsorption, the solution was filtered successively using filter paper and a 0.45 μm aqueous microporous membrane. The concentration of the remaining tetracycline in the filtrate was measured using a spectrophotometer at a wavelength of 357 nm. The results are as follows: Figure 8 As shown: Clearly defined coexisting ion Na + K + Ca 2+ Mg 2 + The effect of UiO-66-SO3H adsorption on the removal of tetracycline from water was investigated by adding 0.025-0.075 mol / L Na. + and K + The adsorption capacity was increased to 194.59 and 190.4 mg / g, respectively. This is likely due to the π-π stacking effect promoting adsorption, while Ca... 2+ and Mg 2+ The adsorption of TC by UiO-66-SO3H was significantly reduced, indicating that Ca 2+ and Mg 2+ It forms a stable complex with TC, thus preventing TC from diffusing to the active site of UiO-66-SO3H.

[0039] Example 6 Effect of humic acid on the adsorption of tetracycline by UiO-66-SO3H: Five 100 mL aliquots of tetracycline solution with a concentration of 50 mg / L were placed in 100 mL Erlenmeyer flasks. Different masses of humic acid were added to the tetracycline solutions to achieve concentrations of 0, 5, 10, 15, and 20 mg / L, respectively. The mixtures were adjusted to an initial pH of 10. 25 mg of UiO-66-SO3H was then added to each flask, and the mixtures were stirred at 200 rpm at 25 °C until adsorption equilibrium was reached. After adsorption, the solutions were filtered successively using filter paper and a 0.45 μm aqueous microporous membrane. The concentration of residual tetracycline in the filtrate was measured using a spectrophotometer at a wavelength of 357 nm. The results are shown below. Figure 9 As shown, with the increase of humic acid concentration, the adsorption capacity gradually decreases due to the competition between surface adsorption sites under high soluble humic acid concentration. Overall, the adsorption capacity of TC is basically unaffected, which indicates that UiO-66-SO3H exhibits excellent anti-interference adsorption performance for soluble organic matter.

[0040] Example 7 Adsorption performance of UiO-66-SO3H for tetracycline in different water bodies: 100 mL of 50 mg / L tetracycline solution was prepared using tap water, deionized water, and ultrapure water, respectively, and placed in conical flasks. 25 mg of UiO-66-SO3H adsorbent was weighed and added to each flask. Adsorption was carried out at 25°C and stirred at 200 rpm. After adsorption, the solution was filtered through a 0.45 μm aqueous microporous membrane. The remaining tetracycline concentration in the solution was measured using a UV spectrophotometer, and the adsorption capacity and removal rate were calculated. The results are shown below. Figure 10 As shown, the adsorption performance of UiO-66-SO3H adsorbent for tetracycline is not significantly different in tap water, deionized water, and ultrapure water, indicating that the water matrix has little effect on the adsorption capacity of UiO-66-SO3H for TC.

[0041] Comparative Example 1 The difference between this embodiment and Example 1 is that the stirring temperature of the adsorption experiment is 20℃, while the other steps are the same as in Example 1. The adsorption performance of the obtained UiO-66-SO3H on tetracycline is not much different from that in Example 1.

[0042] Comparative Example 2 The difference between this embodiment and Example 1 is that the stirring temperature of the adsorption experiment is 32℃, while the other steps are the same as in Example 1. The adsorption performance of the obtained UiO-66-SO3H on tetracycline is not much different from that in Example 1.

[0043] Comparative Example 3 The difference between this embodiment and Example 1 is that the stirring temperature of the adsorption experiment is 60℃, while the other steps are the same as in Example 1. The adsorption performance of the obtained UiO-66-SO3H on tetracycline is not much different from that in Example 1.

[0044] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing UiO-66-SO3H that adsorbs tetracycline, characterized in that, Includes the following steps: The zirconium source and organic ligand were dissolved in a mixture of DMF and hydrochloric acid and subjected to a hydrothermal reaction. After vacuum filtration and washing, the UiO-66-SO3H was obtained.

2. The method for preparing UiO-66-SO3H for adsorbing tetracycline according to claim 1, characterized in that: The zirconium source is zirconium oxychloride octahydrate; the organic ligand is sodium 2-sulfonic acid terephthalate monosodium.

3. The method for preparing UiO-66-SO3H for adsorbing tetracycline according to claim 1, characterized in that: The molar ratio of zirconium source to organic ligand is 10:(1-5).

4. The method for preparing UiO-66-SO3H for adsorbing tetracycline according to claim 1, characterized in that: The washing process involved washing three times with DMF and methanol, respectively.

5. The application of UiO-66-SO3H as described in claim 1 in the adsorption of tetracycline in water, characterized in that, Includes the following steps: The UiO-66-SO3H is dispersed in water containing water pollutants, and the pollutants can be removed after stirring.

6. The application of UiO-66-SO3H according to claim 5 in the adsorption of tetracycline in water, characterized in that, The stirring is carried out at 20-60°C.

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