Preparation method and application of zirconium-based metal organic framework composite sodium alginate material

Abstract

The invention relates to the technical field of adsorption materials, in particular to a preparation method and application of a zirconium-based metal organic framework composite sodium alginate material, zirconium ions serve as a metal core, two ligands including pyromellitic acid and 2, 5-dihydroxy terephthalic acid are added, double-ligand MOFsUiO-66-(OH) 2 / (COOH) 2 is synthesized, then the double-ligand MOFsUiO-66-(OH) 2 / (COOH) 2 is compounded with sodium alginate (SA), and the zirconium-based metal organic framework composite sodium alginate material is obtained. The porous composite material SA (at) UiO-66-(OH) 2 / (COOH) 2 is obtained. The UiO-66-(OH) 2 / (COOH) 2 and SA are rich in-OH and-COOH, so that the chelating ability of the UiO-66-(OH) 2 / (COOH) 2 and SA on heavy metals is further enhanced, and the adsorption effect of the composite material on Pb < 2 + > is enhanced. The low-price composite material provides reference and thought for adsorption of metal ions in an actual water sample on site.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials technology, and in particular to a method for preparing and applying a zirconium-based metal-organic framework composite sodium alginate material. Background Technology

[0002] With rapid industrialization, wastewater from industries such as lead-acid battery production, mining, phosphate fertilizer production, and electronics manufacturing often contains high concentrations of heavy metal ions. These heavy metals can accumulate in organisms through the food chain, causing serious damage to the nervous and immune systems. Among them, lead ions (Pb) are particularly harmful. 2+ Lead ions, due to their high toxicity and ease of binding with biomolecules, pose significant hazards to the central nervous system and digestive system, and have become a major target for water pollution control. Therefore, developing efficient, economical, and easy-to-use adsorption materials for the removal of lead ions from water is of significant practical importance.

[0003] Metal-organic frameworks (MOFs), as novel porous materials, have shown broad application prospects in adsorption and separation due to their high specific surface area, tunable pore structure, and abundant active sites. However, most MOF materials suffer from high synthesis costs, difficult molding, and difficulty in recycling due to their powdered form, limiting their large-scale application in practical water treatment. In particular, zirconium-based metal MOFs, although exhibiting excellent stability, still have shortcomings in adsorption capacity and selectivity due to their single-ligand structure. Therefore, how to improve material performance through rational structural design (such as introducing a dual-ligand strategy) and solve the recycling problem in practical applications has become a key research focus.

[0004] Sodium alginate (SA) is a natural high-molecular-weight polysaccharide containing numerous carboxyl and hydroxyl functional groups. It exhibits excellent chelating ability for heavy metal ions and possesses advantages such as biodegradability, safety, and low cost. However, its poor mechanical properties and tendency to swell limit its application as a standalone adsorbent. Combining MOFs with SA can leverage the high adsorption performance of MOFs while utilizing the film-forming and bead-forming properties of SA to improve the material's operability and recyclability, making it particularly suitable for constructing adsorbents applicable to actual water bodies. Addressing the aforementioned problems in existing technologies, this invention provides a new material and method for resolving lead pollution in actual water samples. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a zirconium-based metal-organic framework composite sodium alginate material, which solves the technical problems of insufficient adsorption capacity for lead ions in water, difficulty in material recycling, and high cost in practical application of existing technologies.

[0006] To achieve the above objectives, the present invention provides a method for preparing a zirconium-based metal-organic framework composite sodium alginate material, comprising the following steps:

[0007] 2,5-Dihydroxyterephthalic acid, pyromellitic acid and zirconium tetrachloride were dispersed in deionized water in a beaker, and acetic acid was added to obtain a mixed solution.

[0008] The mixed solution was transferred to a round-bottom flask for hydrothermal reaction. After a period of time, deionized water was added to continue the hydrothermal reaction. The reaction product was centrifuged and washed to obtain UiO-66-(OH)2 / (COOH)2.

[0009] The suspension of UiO-66-(OH)2 / (COOH)2 was mixed with SA solution and stirred to form a homogeneous sol;

[0010] The sol was dropped into a calcium chloride solution for cross-linking. After standing, washing and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel was obtained.

[0011] In this process, 2,5-dihydroxyterephthalic acid, pyromellitic acid, and zirconium tetrachloride are dispersed in deionized water in a beaker, and acetic acid is added to obtain a mixed solution.

[0012] The amounts of each substance in the mixed solution are as follows: 198.13 mg of 2,5-dihydroxyterephthalic acid, 1016.6 mg of pyromellitic acid, 1165.2 mg of zirconium tetrachloride, 5 mL of acetic acid, and 50 mL of deionized water.

[0013] The mixed solution was transferred to a round-bottom flask for hydrothermal reaction. After a period of time, deionized water was added to continue the hydrothermal reaction. The reaction product was centrifuged and washed to obtain UiO-66-(OH)2 / (COOH)2.

[0014] The hydrothermal reaction in the round-bottom flask was carried out at a temperature of 100°C for 24 hours. Then, 100 mL of deionized water was added, and the subsequent hydrothermal reaction was carried out at a temperature of 100°C for 12 hours.

[0015] The mixed solution was transferred to a round-bottom flask for hydrothermal reaction. After a period of time, deionized water was added to continue the hydrothermal reaction. The reaction product was centrifuged and washed to obtain UiO-66-(OH)2 / (COOH)2.

[0016] During the washing process, wash twice each with water, DMF, and ethanol, until the filtrate is clear and neutral.

[0017] In this process, the suspension of UiO-66-(OH)2 / (COOH)2 is mixed with SA solution and stirred to form a homogeneous sol.

[0018] First, dissolve 600 mg SA in 15 mL of ultrapure water, then dissolve 60 mg UiO-66-(OH)2 / (COOH)2 in 5 mL of ultrapure water, and finally mix the two together.

[0019] In this process, the suspension of UiO-66-(OH)2 / (COOH)2 is mixed with SA solution and stirred to form a homogeneous sol.

[0020] The stirring time is 2 hours.

[0021] In this process, the sol is dropped into a calcium chloride solution for cross-linking. After standing, washing, and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel is obtained.

[0022] The calcium chloride solution has a mass concentration of 5 wt%.

[0023] In this process, the sol is dropped into a calcium chloride solution for cross-linking. After standing, washing, and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel is obtained.

[0024] The cross-linking time is 24 hours.

[0025] During the washing process, rinse with ultrapure water 3 to 4 times until the filtrate is clear and neutral.

[0026] In this process, the sol is dropped into a calcium chloride solution for cross-linking. After standing, washing, and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel is obtained.

[0027] The freeze-drying conditions are: drying at -80℃ for 24 hours.

[0028] A zirconium-based metal-organic framework composite sodium alginate material prepared by the method described above is used for the adsorption and removal of Pb from water. 2+ Applications.

[0029] This invention discloses a method for preparing and applying a zirconium-based metal-organic framework composite sodium alginate material. Using zirconium ions as the metal core, a dual-ligand MOF, UiO-66-(OH)2 / (COOH)2, is synthesized by adding two ligands, pyromellitic acid and 2,5-dihydroxyterephthalic acid. This MOF is then combined with sodium alginate (SA) to obtain a porous composite material, SA@UiO-66-(OH)2 / (COOH)2. Since both UiO-66-(OH)2 / (COOH)2 and SA contain abundant -OH and -COOH groups, their chelating ability for heavy metals is further enhanced, thereby improving the composite material's ability to bind Pb. 2+ The adsorption effect is good. This inexpensive composite material provides a reference and approach for the on-site adsorption of metal ions in actual water samples. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0031] Figure 1 The images are scanning electron microscope (SEM) images of SA (Figures A and B), UiO-66-(OH)2 / (COOH)2 (Figures C and D), and SA@UiO-66-(OH)2 / (COOH)2 (Figures E and F) of the present invention.

[0032] Figure 2 The infrared spectra of SA@UiO-66-(OH)2 / (COOH)2, UiO-66-(OH)2 / (COOH)2 and SA are those of the present invention.

[0033] Figure 3 The XRD patterns of SA, SA@UiO-66-(OH)2 / (COOH)2 and UiO-66-(OH)2 / (COOH)2 of the present invention are shown below.

[0034] Figure 4 The X-ray photoelectron spectrum of SA@UiO-66-(OH)2 / (COOH)2 of the present invention is shown.

[0035] Figure 5 The (A, B) are high-resolution XPS spectra of C1s and O1s of SA@UiO-66-(OH)2 / (COOH)2 in this invention.

[0036] Figure 6 This diagram shows the adsorption selectivity of SA@UiO-66-(OH)2 / (COOH)2 for a single metal according to the present invention.

[0037] Figure 7The SA@UiO-66-(OH)2 / (COOH)2 of the present invention provides the effect of the mixture on Pb in the system. 2+ The adsorption situation diagram.

[0038] Figure 8 The graph shows the adsorption performance of the present invention under different dosages of SA@UiO-66-(OH)2 / (COOH)2.

[0039] Figure 9 For different Pb of the present invention 2+ Adsorption performance of SA@UiO-66-(OH)2 / (COOH)2 by concentration.

[0040] Figure 10 The SA@UiO-66-(OH)2 / (COOH)2 of the present invention is for Pb 2+ The adsorption kinetics diagram.

[0041] Figure 11 The SA@UiO-66-(OH)2 / (COOH)2 of this invention is effective against different concentrations of Pb. 2+ The long-term equilibrium adsorption performance diagram.

[0042] Figure 12 This is a flowchart illustrating the steps of preparing the zirconium-based metal-organic framework composite sodium alginate material according to the present invention. Detailed Implementation

[0043] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0044] Please see Figures 1 to 12 This invention provides a method for preparing a zirconium-based metal-organic framework composite sodium alginate material, comprising the following steps:

[0045] S101: Disperse 2,5-dihydroxyterephthalic acid, pyromellitic acid and zirconium tetrachloride in deionized water in a beaker, and add acetic acid to obtain a mixed solution.

[0046] Specifically, the mixed solution contains 198.13 mg of 2,5-dihydroxyterephthalic acid, 1016.6 mg of pyromellitic acid, 1165.2 mg of zirconium tetrachloride, 5 mL of acetic acid, and 50 mL of deionized water.

[0047] Metal-organic frameworks (MOFs) are a class of porous hybrid materials that have been widely used in drug loading, gas adsorption, catalysis, and other fields, and have attracted much attention in recent years. Utilizing zirconium ions as the metal core and introducing two ligands, pyromellitic acid and 2,5-dihydroxyterephthalic acid (2,5-dihydroxyterephthalic acid), significantly enhances the structural diversity and functional tunability of MOF materials. Furthermore, SA composites can improve the processability and stability of the materials. This invention uses zirconium ions as the metal center and introduces pyromellitic acid and 2,5-dihydroxyterephthalic acid as mixed ligands to construct a dual-ligand MOF material UiO-66-(OH)2 / (COOH)2. Then, by composite with SA, a porous composite material SA@UiO-66-(OH)2 / (COOH)2 is obtained, which possesses abundant pore structures and active sites, diverse functional groups, and readily interacts with Pb. 2+ Combined, it can efficiently treat Pb in water. 2+ .

[0048] S102: The mixed solution is transferred to a round-bottom flask for hydrothermal reaction. After a period of time, deionized water is added to continue the hydrothermal reaction. The reaction product is centrifuged and washed to obtain UiO-66-(OH)2 / (COOH)2.

[0049] Specifically, the hydrothermal reaction in the round-bottom flask is carried out at a temperature of 100°C for 24 hours, followed by the addition of 100 mL of deionized water. The subsequent hydrothermal reaction is carried out at a temperature of 100°C for 12 hours. During the washing process, the filtrate is washed twice each with water, DMF, and ethanol until it is clear and neutral.

[0050] S103: The suspension of UiO-66-(OH)2 / (COOH)2 is mixed with the SA solution and stirred to form a homogeneous sol. First, 600 mg of SA is dissolved in 15 mL of ultrapure water, then 60 mg of UiO-66-(OH)2 / (COOH)2 is dissolved in 5 mL of ultrapure water, and finally the two are mixed. The stirring time is 2 hours. The concentration of calcium chloride solution is 5 wt%.

[0051] S104: The sol is dropped into a calcium chloride solution for cross-linking. After standing, washing and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel is obtained.

[0052] Specifically, the static cross-linking time is 24 hours. During the washing process, the sample is washed 3-4 times with ultrapure water until the filtrate is clear and neutral. The freeze-drying temperature is -80°C, and the time is 24 hours.

[0053] SA is a natural polysaccharide with abundant carboxyl (-COOH) and hydroxyl (-OH) groups on its surface. However, SA is readily soluble in water and has poor mechanical properties, limiting its application in water treatment. This invention prepares a UiO-66-(OH)2 / (COOH)2 composite SA adsorbent by loading a small amount of UiO-66-(OH)2 / (COOH)2 onto the surface of SA through cross-linking, and investigates its adsorption on Pb. 2+ Adsorption performance.

[0054] This invention offers the following advantages: Using zirconium ions as the metal core, a dual-ligand MOF, UiO-66-(OH)2 / (COOH)2, is synthesized by adding two ligands, pyromellitic acid and 2,5-dihydroxyterephthalic acid. This MOF is then combined with SA to obtain the porous composite material SA@UiO-66-(OH)2 / (COOH)2. Since both UiO-66-(OH)2 / (COOH)2 and SA contain abundant −OH and −COOH, their chelating ability for heavy metals is further enhanced, thereby strengthening the composite material's ability to bind Pb. 2+ The adsorption effect is good. This inexpensive composite material provides a reference and approach for the on-site adsorption of metal ions in actual water samples.

[0055] Example 1

[0056] Dissolve 600 mg SA in 15 mL of deionized water and stir in a water bath at 60 °C to obtain an SA aqueous solution.

[0057] Example 2

[0058] UiO-66-(OH)2 / (COOH)2 was synthesized via a hydrothermal method. First, 2,5-dihydroxyterephthalic acid (DHTA) (198.13 mg, 1 mmol), pyromellitic acid (PMA) (1016.6 mg, 4 mmol), and zirconium tetrachloride (ZrCl4) (1165.2 mg, 5 mmol) were dispersed in 50 mL of deionized water, followed by the addition of 5 mL of acetic acid. The reaction was carried out at 100 °C for 24 h. Next, the resulting suspension was transferred to a 250 mL round-bottom flask containing 100 mL of deionized water, and the reaction was continued for 12 h. After cooling to room temperature, the mixture was centrifuged, and the solid was collected and washed twice each with water, DMF, and ethanol. UiO-66-(OH)2 / (COOH)2 powder was obtained and labeled as UiO-66-(OH)2 / (COOH)2.

[0059] Example 3

[0060] 60 mg of UiO-66-(OH)2 / (COOH)2 prepared in Example 2 was uniformly dispersed in 5 mL of aqueous solution by ultrasound to obtain a homogeneous suspension of UiO-66-(OH)2 / (COOH)2. Next, the suspension was slowly added to the SA aqueous solution prepared in Example 1 using a dropper, and the mixture was magnetically stirred for 2 h to ensure uniform dispersion of UiO-66-(OH)2 / (COOH)2 in the SA aqueous solution, resulting in a homogeneous sol. Then, the sol formed by UiO-66-(OH)2 / (COOH)2 and SA was uniformly injected into a 5 wt% calcium chloride aqueous solution using a syringe pump (or dropper), and allowed to stand for 24 h to allow complete cross-linking of the hydrogel, resulting in uniformly sized beads. After washing the beads multiple times with deionized water to remove impurities from the surface, the beads were placed in a freeze dryer and dried for 24 hours to obtain SA@UiO-66-(OH)2 / (COOH)2 aerogel, which was labeled as SA@UiO-66-(OH)2 / (COOH)2.

[0061] 1. Structural testing of SA, UiO-66-(OH)2 / (COOH)2, and SA@UiO-66-(OH)2 / (COOH)2;

[0062] SA, UiO-66-(OH)2 / (COOH)2 and SA@UiO-66-(OH)2 / (COOH)2 prepared using the methods of Examples 1, 2 and 3 were analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), powder XRD and XPS. The results are shown below.

[0063] (1) Scanning electron microscopy analysis:

[0064] The morphological characteristics of SA, UiO-66-(OH)2 / (COOH)2, and SA@UiO-66-(OH)2 / (COOH)2 were analyzed using scanning electron microscopy. The results are as follows: Figure 1 As shown in (A, B, C, D, E, F), the surface of the calcium-crosslinked SA microspheres is very smooth. Figure 1 A), in comparison, the surface of the SA@UiO-66-(OH)2 / (COOH)2 microspheres is much rougher. Figure 1 B) shows numerous small, protruding particles on its surface, indicating that UiO-66-(OH)2 / (COOH)2 has been successfully doped. As can be seen from Figures (1C and 1D), UiO-66-(OH)2 / (COOH)2 consists of dispersed nanocrystalline particles.

[0065] Furthermore, the calcium-crosslinked SA microspheres have larger internal pores and are stacked in layers. Figure 1 E), while the interior of the SA@UiO-66-(OH)2 / (COOH)2 microspheres is a honeycomb-like pore structure. Figure 1F), and the pores are relatively small, which may be because the UiO-66-(OH)2 / (COOH)2 crystals can act as a framework to support the pores.

[0066] (2) Infrared spectroscopy analysis:

[0067] SA, UiO-66-(OH)2 / (COOH)2, and SA@UiO-66-(OH)2 / (COOH)2 were characterized using a Fourier transform infrared spectrometer and the KBr solid pellet method for sample preparation. The scanning wavenumbers were 4000–400 cm⁻¹. -1 Wavenumber analysis is used to perform qualitative analysis on samples by plotting FT-IR spectra, analyzing the functional groups present, and determining whether the target substance has been introduced.

[0068] FT-IR spectral results as follows Figure 2 As shown. The FTIR spectrum of SA indicates that in the 3600-3300 cm⁻¹ range... −1 The band at 1428 cm⁻¹ can be attributed to the OH stretching vibration peak. −1 and 1630cm −1 The peak at that location can be attributed to the SA / -COO- group. Furthermore, the FTIR spectrum of UiO-66-(OH)2 / (COOH)2 was investigated, with results showing values ​​in the 3600-3280 cm⁻¹ range. -1 The broad peak within the range can be attributed to the OH stretching vibration peak of the polyphenol group. At approximately 804 cm⁻¹... −1 and 660cm -1 The Zr-O stretching peaks at 1260-1075 cm⁻¹ originate from Zr metal clusters, and these two peaks indicate the presence of Zr-O bonds / Zr(μ₃)O in the UiO-66-(OH)₂ / (COOH)₂MOF structure. Notably, the peaks at 1260-1075 cm⁻¹... -1 The absorption band at this point corresponds to the CO stretching of the -OH group of the aromatic ligand DHTA in UiO-66-(OH)2 / (COOH)2. Furthermore, the absorption band at 1470-1330 cm⁻¹ corresponds to this CO stretching. -1 The nearby peaks represent the symmetric and asymmetric stretching peaks of the -C=OO groups formed by the coordination of the Zr metal center with the organic ligands PMA and DHTA of UiO-66-(OH)2 / (COOH)2, respectively. Similarly, to understand the mechanism of crosslinking and composite processes, the FTIR spectrum of SA@UiO-66-(OH)2 / (COOH)2 was also investigated. Notably, after loading the MOF, the intensities of the characteristic peaks of the -OH, Zr-O, and -COO groups formed by the coordination of the Zr metal center with the organic ligands PMA and DHTA also decreased, while the Zr-O peak decreased from 804 cm⁻¹. −1 It moved to 830cm −1This may be because the crosslinking and compounding processes establish connections through hydrogen bonds and van der Waals forces.

[0069] (3) Powder XRD pattern:

[0070] XRD pattern results are as follows Figure 3 As shown, the characteristic peaks of UiO-66-(OH)2 / (COOH)2 were observed near 2θ = 7.4°, 8.5°, and 25.8°, corresponding to the (111), (200), and (224) crystal planes, respectively. These characteristic peaks of UiO-66-(OH)2 / (COOH)2 confirm its excellent crystallinity and mechanical stability. Furthermore, the positions of these characteristic peaks match those previously reported.

[0071] (4) XPS analysis:

[0072] XPS analysis results are as follows: Figure 4 and Figure 5 As shown. Figure 4 As shown, the main signal peaks near 284.8, 532.36, 347.95, 191.48, and 1072.12 eV are consistent with elements such as C1s, O1s, Ca2p, Zr3d, and Na1s. Furthermore, to verify the key functional groups of the material, high-resolution XPS spectra of O1s, C1s, and Zr3d in SA@UiO-66-(OH)2 / (COOH)2 were explored. Figure 5 As shown, for SA@UiO-66-(OH)2 / (COOH)2, the peaks near 533.11, 532.18, and 531.49 eV correspond to Zr-OC, Zr-OH, and O-Ca, respectively. Figure 5 A). The peaks near 284.78, 286.54, and 288.57 eV correspond to CO, Zr-OC, and C-OH / CO, respectively. Figure 5 B). The presence of the Zr peak indicates that the material composite was successfully completed.

[0073] 2. Performance testing of SA@UiO-66-(OH)2 / (COOH)2;

[0074] (1) Adsorption selectivity of SA@UiO-66-(OH)2 / (COOH)2 for single metals:

[0075] To investigate the effect of SA@UiO-66-(OH)2 / (COOH)2 on different metal ions (Fe) 3+ Al 3+ Cr 3+ Cu 2+ Mn 2+ Mg2+ Cd 2+ Ca 2+ Zn 2+ Pb 2+ Co 2+ Ni 2+ Na + K + To assess the selectivity of Fe, 14 different metal ion solutions (Fe2+, Fe2+, Fe3+, Fe2+, Fe3+) were prepared at room temperature, each with a concentration of 100 mg / L. 3+ Al 3+ Cr 3+ Cu 2+ Mn 2+ Mg 2+ Cd 2+ Ca 2+ Zn 2+ Pb 2+ Co 2+ Ni 2+ Na + , K+). 5 mg of SA@UiO-66-(OH)2 / (COOH)2 prepared in Example 3 was placed in different metal ion solutions mentioned above, and placed in a constant temperature shaker at 30°C and 200 r / min for 24 h. After the reaction was completed, the supernatant was filtered and the concentration of different metal ions was measured to determine the adsorption selectivity.

[0076] Adsorption selectivity results as follows Figure 6 As shown, SA@UiO-66-(OH)2 / (COOH)2 affects Pb 2+ The adsorption effect is the best, and its equilibrium adsorption capacity can reach 168 mg / g.

[0077] (2) SA@UiO-66-(OH)2 / (COOH)2 in a mixed system for the effect of Pb 2+ Adsorption capacity study:

[0078] To explore the effect of SA@UiO-66-(OH)2 / (COOH)2 on Pb in a mixed system 2+ The adsorption capacity of different metal ions (Fe) 3+ Al 3+ Cr 3+ Cu 2+ Mn 2+ Mg 2+ Cd 2+ Ca 2+ Zn 2+ Pb 2+ Co 2+ Ni 2+ Na + K+ ) and Pb 2+ The two mixtures were combined to prepare binary systems with a volume of 15 mL and a concentration of 100 mg / L. Then, 10 mg of SA@UiO-66-(OH)2 / (COOH)2 prepared in Example 3 was placed into each of the two binary systems and placed in a constant-temperature shaker at 30 °C and 200 rpm for 24 h. After the reaction, the supernatant was filtered, and the concentrations of different metal ions were determined to assess the effect of different metal ions on Pb in the mixed system. 2+ The adsorption capacity was determined.

[0079] Adsorption performance results are as follows Figure 7 As shown, when lead ions are mixed with chromium ions, aluminum ions, or iron ions respectively, SA@UiO-66-(OH)2 / (COOH)2 affects Pb 2+ The adsorption efficiency of Pb decreased significantly, which may be due to the adsorption of Pb by chromium ions, aluminum ions, and iron ions. 2+ There is an adsorption competition relationship.

[0080] (3) Adsorption performance study under different SA@UiO-66-(OH)2 / (COOH)2 dosage:

[0081] To compare the effect of SA@UiO-66-(OH)2 / (COOH)2 prepared in this invention on Pb under different dosages 2+ To assess the adsorption performance, 5, 10, 15, 20, 25, and 30 mg of SA@UiO-66-(OH)2 / (COOH)2 prepared in Example 3 were weighed and placed in a 15 mL Lb solution with a concentration of 100 ppm. 2+ The solution was placed in a constant temperature shaker and shaken at 30℃ and 200r / min for 24h. After the reaction was completed, the sample was filtered and taken for adsorption performance determination.

[0082] Adsorption performance results are as follows Figure 8 As shown, at the same concentration (100 ppm), the adsorption rate increases with increasing composite material dosage. This is because a larger amount of adsorbent provides more pores and active sites for adsorption, thus increasing the adsorption rate. Conversely, with increasing adsorbent dosage, the amount of Pb that can be adsorbed per unit mass of adsorbent decreases. 2+ The dosage will decrease accordingly, until the adsorption rate reaches its maximum when the dosage reaches 25mg.

[0083] (4) Different Pb 2+ Study on the effect of concentration on the adsorption performance of SA@UiO-66-(OH)2 / (COOH)2:

[0084] To compare the SA@UiO-66-(OH)2 / (COOH)2 prepared in this invention with different Pb 2+To assess the adsorption performance at different concentrations, seven 25mg portions of SA@UiO-66-(OH)2 / (COOH)2 prepared in Example 3 were weighed and placed in 15ml solutions of Pb at concentrations of 100mg / L, 200mg / L, 300mg / L, 400mg / L, 500mg / L, 600mg / L, and 700mg / L, respectively. 2+ The solution was placed in a constant temperature shaker and shaken at 30℃ and 200r / min for 24h. After the reaction was completed, the sample was filtered and taken for adsorption performance determination.

[0085] Adsorption performance results are as follows Figure 9 As shown, with Pb 2+ With increasing concentration, SA@UiO-66-(OH)2 / (COOH)2 affects Pb 2+ The adsorption capacity increases accordingly, but the pores and active sites provided by the adsorbent gradually become insufficient, once Pb... 2+ When the concentration reaches 500 ppm, the adsorption rate decreases rapidly, and the rate of change in adsorption amount also decreases.

[0086] (5) SA@UiO-66-(OH)2 / (COOH)2 on Pb 2+ Adsorption kinetics study:

[0087] To determine a reasonable adsorption time in the adsorption isotherm experiment, this invention conducted adsorption kinetics experiments to study the variation of adsorption capacity with time at a given concentration. The results are presented by... Figure 10 As shown, qt increases rapidly in the initial stage because, during this period, the abundant pore structure and active sites of SA@UiO-66-(OH)2 / (COOH)2 have not yet been absorbed by Pb. 2+ Occupied. Over time, pores and active sites are gradually occupied by Pb. 2+ As the adsorption capacity is filled, the growth rate of qt gradually decreases, and adsorption reaches equilibrium at approximately 300 min. The adsorption process can be intuitively represented using pseudo-first-order and pseudo-second-order kinetic models, the parameters of which are shown in Table 1. The Ri values ​​for both models are... 2 The small difference indicates that the adsorption process involves both physical and chemical adsorption.

[0088]

[0089] Table 1

[0090] (6) SA@UiO-66-(OH)2 / (COOH)2 for different concentrations of Pb 2+ Long-term equilibrium adsorption characteristics study:

[0091] This paper selects two typical nonlinear models, namely Langmuir and Froderich, to fit the adsorption isotherm, and the results are as follows: Figure 11 As shown in Table 2, the parameter results indicate that the Langmuir model is better suited to interpreting the isothermal experimental data. This suggests that SA@UiO-66-(OH)2 / (COOH)2 has a positive effect on Pb. 2+ The adsorption process is mainly monolayer homogeneous chemisorption. Furthermore, according to the Langmuir model, at 298 K, SA@UiO-66-(OH)2 / (COOH)2 has a high adsorption capacity for Pb. 2+ The theoretical maximum adsorption capacity (q) max The concentration was 335.8 mg / g at 308 K, 316.3 mg / g at 318 K, and 295.4 mg / g at 318 K.

[0092]

[0093] Table 2

[0094] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for preparing a zirconium-based metal-organic framework composite sodium alginate material, characterized in that, The method comprises the following steps: dispersing 2,5-dihydroxyterephthalic acid, pyromellitic acid and zirconium tetrachloride in deionized water in a beaker, and adding acetic acid to obtain a mixed solution; transferring the mixed solution into a round-bottom flask for hydrothermal reaction, adding deionized water after a period of time to continue the hydrothermal reaction, and obtaining UiO-66-(OH)2 / (COOH)2 through centrifugation and washing of the reaction product; mixing the suspension of the UiO-66-(OH)2 / (COOH)2 with a SA solution to form a uniform sol through stirring; dropping the sol into a calcium chloride solution for crosslinking, and obtaining SA@UiO-66-(OH)2 / (COOH)2 aerogel through standing, washing and freeze-drying.

2. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 1, characterized in that, dispersing 2,5-dihydroxyterephthalic acid, pyromellitic acid and zirconium tetrachloride in deionized water in a beaker, and adding acetic acid to obtain a mixed solution, wherein: the amounts of the substances in the mixed solution are as follows: 2,5-dihydroxyterephthalic acid 198.13 mg, pyromellitic acid 1016.6 mg, zirconium tetrachloride 1165.2 mg, acetic acid 5 mL and deionized water 50 mL.

3. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 2, characterized in that, transferring the mixed solution into a round-bottom flask for hydrothermal reaction, adding deionized water after a period of time to continue the hydrothermal reaction, and obtaining UiO-66-(OH)2 / (COOH)2 through centrifugation and washing of the reaction product, wherein: the temperature of the hydrothermal reaction in the round-bottom flask is 100 ℃, 100 mL of deionized water is added after 24 h of hydrothermal reaction, the temperature of the subsequent hydrothermal reaction is 100 ℃, and the reaction time is 12 h.

4. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 3, characterized in that, transferring the mixed solution into a round-bottom flask for hydrothermal reaction, adding deionized water after a period of time to continue the hydrothermal reaction, and obtaining UiO-66-(OH)2 / (COOH)2 through centrifugation and washing of the reaction product, wherein: during the washing treatment, the solution is sequentially washed with water, DMF and ethanol for 2 times respectively until the filtrate is clear and neutral.

5. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 4, characterized in that, mixing the suspension of the UiO-66-(OH)2 / (COOH)2 with a SA solution to form a uniform sol through stirring, wherein: first, 600 mg of SA is dissolved in 15 mL of ultrapure water, then 60 mg of UiO-66-(OH)2 / (COOH)2 is dissolved in 5 mL of ultrapure water, and finally the two solutions are mixed.

6. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 5, characterized in that, mixing the suspension of the UiO-66-(OH)2 / (COOH)2 with a SA solution to form a uniform sol through stirring, wherein: the stirring time is 2 h.

7. The method of claim 6, wherein the zirconium-based metal-organic framework composite sodium alginate material is prepared by the steps of: (a) mixing a zirconium-based metal-organic framework with sodium alginate to form a mixture; (b) adding a solvent to the mixture; (c) stirring the mixture; and (d) drying the mixture. dropping the sol into a calcium chloride solution for crosslinking, and obtaining SA@UiO-66-(OH)2 / (COOH)2 aerogel through standing, washing and freeze-drying, wherein: the mass concentration of the calcium chloride solution is 5 wt%.

8. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 7, characterized in that, dropping the sol into a calcium chloride solution for crosslinking, and obtaining SA@UiO-66-(OH)2 / (COOH)2 aerogel through standing, washing and freeze-drying, wherein: the crosslinking time for standing is 24 h; during the washing treatment, the solution is washed with ultrapure water for 3-4 times until the filtrate is clear and neutral.

9. The preparation method of the zirconium-based metal-organic framework composite sodium alginate material as described in claim 8, characterized in that, The sol was dropped into a calcium chloride solution for cross-linking, and after standing, washing and freeze-drying, SA@UiO-66-(OH)2 / (COOH)2 aerogel was obtained, wherein: The freeze-drying condition was: drying at -80℃ for 24h.

10. Use of a zirconium-based metal-organic framework composite sodium alginate material prepared according to the method of any one of claims 1 to 9 for adsorptive removal of Pb 2+ from water.

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