UiO-66-EDTA composite material, and preparation method and application thereof

Abstract

The application discloses a kind of UiO-66-EDTA composite material and its preparation method and application, it is related to wastewater treatment technical field.The application first uses solvothermal method to prepare UiO-66 nanoparticle, then by solution immersion-surface coordination method, EDTA-2Na is loaded on the surface of UiO-66, and UiO-66-EDTA composite material is synthesized.The application studies the adsorption performance of the composite material to Cu 2+ , and the results show that the adsorption of UiO-66-EDTA to Cu 2+ is best at pH=5.0, and the adsorption process accords with quasi second kinetics model and Langmuir isothermal adsorption model, and the maximum theoretical adsorption capacity reaches 186.3 mg.g ‑1 at 298 K, which is much higher than that of unmodified UiO-66.Thermodynamic parameters show that the adsorption process is spontaneous and endothermic.UiO-66-EDTA, as a kind of composite material with simple preparation process and excellent adsorption performance, has good application prospect in the field of copper-containing wastewater advanced treatment.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a UiO-66-EDTA composite material, its preparation method, and its application. Background Technology

[0002] Copper ions (Cu2+) are a widely distributed heavy metal and an essential trace element for the growth of most organisms. They play crucial roles in many biological processes, serving as an important cofactor for many enzymes and proteins, and are closely related to metabolism, antioxidation, and neural regulation. For example, they participate in the composition and activation of enzymes such as ceruloplasmin, cytochrome C oxidase, and monoamine oxidase (MAO). They also participate as a cofactor in metabolic processes such as oxidative phosphorylation, free radical detoxification, melanin synthesis, blood clotting, and hair formation. While copper ions play a vital role in biological growth, studies have shown that excessive copper can also be toxic to cells, inducing copper poisoning. Clinically, acute copper poisoning can cause symptoms such as nausea, vomiting, hemolytic anemia, and liver and kidney failure, while chronic copper poisoning not only causes rare diseases such as Wilson's disease and cirrhosis in Indian children, but also increases oxidative stress, free radical formation, and mitochondrial dysfunction. Therefore, maintaining copper homeostasis is of great importance to the body's health.

[0003] With rapid industrial development, factories discharge large amounts of wastewater daily, containing various heavy metal ions such as copper. Untreated wastewater discharge pollutes water bodies, soil, and organisms. These heavy metal ions, passed through the food chain, can harm human health. Therefore, utilizing appropriate materials and methods to detect and remove heavy metal ions from environmental water has become a research hotspot.

[0004] UiO-66 material inherently possesses physicochemical properties such as good stability, large specific surface area, and ease of modification without losing its framework structure, as well as adsorption capacity for metal ions. These characteristics make it a potential material for heavy metal removal. However, its adsorption capacity for Cu2+ is not as good as its adsorption capacity for other metal ions, and it is also difficult to separate Cu2+. Therefore, how to modify UiO-66 material to improve its Cu2+ removal and separation efficiency is a key research focus for those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a UiO-66-EDTA composite material, its preparation method, and its application, so as to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a UiO-66-EDTA composite material, comprising the following steps: UiO-66 was mixed with EDTA-2Na and water, and the mixture was heated to react and obtain UiO-66-EDTA.

[0007] EDTA-2Na can chelate with copper ions, exhibiting strong complexing properties. This prevents copper ions from leaking into the environment and also enhances the recyclability of UiO-66 materials.

[0008] Furthermore, the ratio of UiO-66 to EDTA-2Na and water is 100 mg: 1.6870 g: 50 mL.

[0009] Furthermore, mixing the UiO-66 with EDTA-2Na and water includes: first dispersing UiO-66 in water by ultrasound, and then adding EDTA-2Na.

[0010] Furthermore, the heating reaction is carried out at a temperature of 50-70 °C for a duration of 20-28 h.

[0011] Further, the preparation steps of the UiO-66 include: mixing zirconium source, terephthalic acid, N,N-dimethylformamide (DMF) and acetic acid, and reacting at 110-130 °C for 20-28 h to obtain the UiO-66.

[0012] Furthermore, the zirconium source includes zirconium oxychloride octahydrate.

[0013] Furthermore, the ratio of zirconium source, terephthalic acid, N,N-dimethylformamide, and acetic acid is 0.3220 g: 0.1660 g: 40 mL: 1.0 mL.

[0014] Furthermore, after reacting at 110-130 °C for 20-28 h, the process also includes steps of cooling, centrifugation, collecting the solid product and washing it alternately with N,N-dimethylformamide and methanol, followed by drying.

[0015] The second technical solution of the present invention: a UiO-66-EDTA composite material prepared according to the above preparation method.

[0016] The third technical solution of the present invention: the application of the above-mentioned UiO-66-EDTA composite material in the adsorption and removal of copper ions in water.

[0017] The present invention discloses the following technical effects: This invention first prepared UiO-66 nanoparticles using a solvothermal method, and then synthesized a UiO-66-EDTA composite material by loading EDTA-2Na onto the surface of UiO-66 via a solution impregnation-surface coordination method. XRD and SEM characterization confirmed that EDTA modification did not destroy the crystal structure and octahedral morphology of UiO-66. FT-IR analysis confirmed that the carboxyl and amino functional groups of EDTA were successfully introduced into the material surface. BET analysis showed that the specific surface area increased from 478.376 m² after loading with EDTA-2Na. 2 ·g -1 Decreased to 210.203 m 2 ·g -1 UiO-66-EDTA for Cu 2+ The adsorption was optimal at pH 5.0, and the adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum theoretical adsorption capacity at 298 K reached 186.3 mg·g⁻¹. -1 The adsorption rate is significantly higher than that of unmodified UiO-66. Thermodynamic parameters indicate that the adsorption is a spontaneous endothermic process. The adsorption mechanism mainly involves the reaction of EDTA-2Na carboxyl oxygen and amino nitrogen with Cu. 2+ The chelation and coordination between the components, supplemented by electrostatic attraction and pore mass transfer, make UiO-66-EDTA a composite material with simple preparation process and excellent adsorption performance, showing clear application prospects in the field of advanced treatment of copper-containing wastewater. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 SEM images of UiO-66 (a and b) and UiO-66-EDTA (c and d) at different magnifications.

[0020] Figure 2 The FT-IR spectra of UiO-66 (A) and UiO-66-EDTA (B) are shown.

[0021] Figure 3 XRD patterns of UiO-66 and UiO-66-EDTA.

[0022] Figure 4Figures and pore size diagrams are shown for nitrogen isothermal adsorption-desorption of UiO-66 and UiO-66-EDTA. In the figure, a is the nitrogen adsorption-desorption curve of UiO-66, b is the nitrogen adsorption-desorption curve of UiO-66-EDTA, c is the pore size diagram of UiO-66, and d is the pore size diagram of UiO-66-EDTA.

[0023] Figure 5 The effects of UiO-66 and UiO-66-EDTA on Cu in the pH range of 2.0–6.0 2+ Changes in adsorption capacity.

[0024] Figure 6 Time for Cu adsorption on UiO-66-EDTA 2+ The effects (a), the fitted pseudo-first-order kinetic rate equation (b), and the fitted pseudo-second-order kinetic rate equation (c).

[0025] Figure 7 The figures are Langmuir fitting plot (a) and Freundlich fitting plot (b) for isothermal adsorption.

[0026] Figure 8 The adsorption thermodynamic fitting diagram for UiO-66-EDTA is shown.

[0027] Figure 9 The figure shows the results of five adsorption-desorption cycles of UiO-66-EDTA. Detailed Implementation

[0028] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0029] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0030] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0031] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0032] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0033] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0034] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20~30℃.

[0035] All raw materials used in the following embodiments, comparative examples and test examples of this invention are commercially available products, and all raw materials and reagents are of analytical grade.

[0036] Example 1 A UiO-66-EDTA composite material is prepared by the following steps: (1) Synthesis of UiO-66 0.1660 g of terephthalic acid (HOCO(C6H4)COOH) and 0.3220 g of zirconium oxychloride octahydrate (ZrOCl2·8H2O) were weighed and added to 40 mL of DMF, and ultrasonically dispersed for 15 min until the solid was basically dissolved. Then, 1.0 mL of acetic acid was added as a crystal growth regulator, and the mixture was magnetically stirred for 30 min to mix thoroughly. The mixture was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealed, and placed in an oven at 120 ℃ for 24 h. After naturally cooling to room temperature, the mixture was centrifuged at 8000 rpm for 5 min, and the white solid product was collected. It was washed three times alternately with 20 mL of DMF and 20 mL of methanol (one DMF + one methanol wash constitutes one alternating wash, repeated three times in total) to remove residual reactants and replace the DMF. Finally, it was dried in a vacuum drying oven at 70 ℃ for 12 h to obtain UiO-66.

[0037] (2) Synthesis of UiO-66-EDTA 100 mg of UiO-66 obtained in step (1) was dispersed in 50 mL of deionized water by ultrasound, and then 1.6870 g of EDTA-2Na was added to obtain a mixed solution. The mixed solution was reacted at a constant temperature of 60 °C for 24 h. After the reaction was completed, the reaction product was washed alternately with deionized water and acetone, and then dried under vacuum to obtain UiO-66-EDTA.

[0038] Test Example 1 Morphological and structural characterization was performed on the UiO-66 and UiO-66-EDTA prepared in Example 1. (1) SEM characterization Figure 1 In the images, a and b are SEM images of UiO-66 magnified by 2000 and 10000 times, respectively. It can be clearly seen from the images that the UiO-66 material exhibits a regular octahedral structure with a relatively smooth surface and relatively uniform crystal particle size. Figure 1 c and d in the figure are SEM images of UiO-66-EDTA magnified by 20,000 and 5,000 times, respectively. It can be seen from the figure that the shape still presents a regular octahedron, but the surface is rougher than that of UiO-66, which can prove the modification of UiO-66 by EDTA-2Na.

[0039] (2) Infrared spectroscopy (FT-IR) characterization Figure 2 In the diagram, A is the FT-IR spectrum of UiO-66, and B is the FT-IR spectrum of UiO-66-EDTA. From A, it can be seen that at 3392 cm⁻¹... -1 The absorption peak at 1627 cm⁻¹ is caused by the -OH group in H₂O. -1 and 1367 cm -1 The two absorption peaks nearby, associated with COO-stretching vibrations, are at 1511 cm⁻¹. -1 The absorption peak at 545 cm⁻¹ is due to the C=C bond of the benzene ring. -1 The absorption peak at [value] is due to the asymmetric stretching vibration of Zr-(OC). In addition to the main absorption peak at UiO-66, there is an additional peak at 2393 cm⁻¹ in B. -1 The absorption peak at that point should be caused by the CN(C)-C group, confirming the modification of UiO-66 by EDTA-2Na.

[0040] (3) XRD characterization Figure 3The XRD patterns of UiO-66 and UiO-66-EDTA show that UiO-66 exhibits distinct characteristic diffraction peaks at 2θ = 7.4°, 8.5°, and 25.7°, corresponding to the (111), (200), and (224) crystal planes of the face-centered cubic crystal, respectively. The peaks are sharp and have flat baselines, showing good agreement with the standard spectra reported in the literature, indicating the successful synthesis of a highly crystalline pure-phase UiO-66 material. The diffraction peak positions of UiO-66-EDTA are basically consistent with those of UiO-66, and the characteristic peaks of the (111) and (200) crystal planes remain clearly distinguishable, indicating that the loading process of EDTA-2Na did not damage the main framework structure of UiO-66. The diffraction peak intensity is slightly lower than that of the original UiO-66. This is because the EDTA-2Na molecules adhere to the surface of the UiO-66 crystal and some pore locations, causing a certain degree of decrease in crystallinity and a weakening of the X-ray scattering effect.

[0041] Test Example 2 Nitrogen adsorption-desorption performance test The nitrogen adsorption-desorption curves and pore size distribution of UiO-66 and UiO-66-EDTA prepared in Example 1 were tested using an SSA-4300 pore size and specific surface area analyzer. The results are as follows: Figure 4 As shown.

[0042] Figure 4 In the diagram, 'a' represents the nitrogen adsorption-desorption curve of UiO-66, 'b' represents the nitrogen adsorption-desorption curve of UiO-66-EDTA, 'c' represents the pore size diagram of UiO-66, and 'd' represents the pore size diagram of UiO-66-EDTA (in each diagram, A represents the adsorption curve and B represents the desorption curve). From 'a', it can be seen that the adsorption of UiO-66 belongs to Type I curves with an H4 hysteresis loop, and the BET specific surface area is 478.376 m². 2 ·g -1 The correlation coefficient is 0.9979. From b, it can be seen that the adsorption of UiO-66-EDTA exhibits an H4-type hysteresis loop, and the BET specific surface area is 210.203 m². 2 / g, with a correlation coefficient of 0.9985. From c, we know that the pore volume of UiO-66 is 0.28 cc·g. -1 (i.e. cm) 3 / g), from d, we can know that the micropore volume of UiO-66-EDTA is 0.1035 cc·g. -1 The most probable pore size is 1.11–1.13 nm, with an average pore size of 3.15 nm. The material is predominantly micropores and narrow mesopores, with pore morphologies mainly consisting of slit pores and interstitial pores, indicating a microporous-mesoporous composite structure. This hierarchical pore structure not only provides a large number of adsorption active sites but also accelerates Cu adsorption. 2+ Mass transfer and diffusion of ions enable UiO-66-EDTA to affect Cu2+ It exhibits good adsorption performance.

[0043] Test Example 3 Copper ion adsorption performance test 1. Testing Method Cu 2+ Standard curve preparation: Accurately weigh 0.3928 g of copper sulfate pentahydrate (CuSO4·5H2O), dissolve it in deionized water, and dilute to 1 L to prepare a concentration of 100 mg·L⁻¹. -1 (with Cu) 2+ Cu (calculated) 2+ The standard stock solution was used as the mother solution. A certain amount of this mother solution was taken, and 1 mL of copper reagent and 2 mL of buffer solution were added. The solution was then serially diluted with deionized water and brought to volume in 25 mL colorimetric tubes to obtain concentrations of 0.5, 1.0, 1.4, 1.8, 2.4, 2.8, 3.6, and 4.0 mg·L⁻¹. -1 Cu 2+ Standard solution. During the 5–30 min stabilization period, the absorbance (Abs) was measured at 452 nm using a UV-Vis spectrophotometer.

[0044] Adsorption kinetics experiment: Accurately weigh 50.0 mg UiO-66-EDTA into 50 mL of an initial concentration of 100 mg·L⁻¹. -1 Cu 2+ In the solution, use 0.1 mol·L -1 Adjust the pH to 5.0 with HCl. Place the mixture in a constant temperature air bath shaker and shake at 298 K and 150 r / min. Take samples at 10, 20, 30, 45, 60, 90, and 120 min. Centrifuge at 8000 r / min for 5 min to separate the supernatant, determine the corresponding Abs, and calculate the unadsorbed Cu. 2+ concentration (C) t ), thus calculating Cu 2+ Adsorption amount (q) t ).

[0045] Isothermal adsorption experiment (298 K): 50.0 mg UiO-66-EDTA was accurately weighed into 50 mL of different initial concentrations (20, 40, 60, 80, 100, 150, 200 mg·L⁻¹). -1 Cu 2+ In the solution, use 0.1 mol·L -1 Adjust the pH to 5.0 with HCl. Place the mixture in a constant temperature air bath shaker and shake for 120 min at 298 K and 150 r / min. Transfer the supernatant to a centrifuge tube and centrifuge at 8000 r / min for 5 min. Measure the absorbance and determine the residual Cu.2+ Concentration (i.e., equilibrium concentration Ce), calculate adsorption capacity q e .

[0046] pH effect experiment: Accurately weigh 50.0 mg UiO-66-EDTA into 50 mL of an initial concentration of 100 mg·L⁻¹. -1 Cu 2+ In the solution, use 0.1 mol·L -1 The initial pH of the solution was adjusted to 2.0, 3.0, 4.0, 5.0, and 6.0 using HCl or NaOH. The mixture was placed in a constant-temperature air bath shaker and shaken for 2 h at 298 K and 150 r / min. The supernatant was transferred to a centrifuge tube and centrifuged at 8000 r / min for 5 min. The absorbance of the supernatant was measured, and the residual Cu was determined. 2+ Concentration (i.e., equilibrium concentration Ce), calculate adsorption capacity q e .

[0047] Thermodynamic experiments: Adsorption experiments were conducted at five temperatures: 298 K, 303 K, 308 K, 313 K, and 318 K, using the same initial concentration series (100 mg·L⁻¹) at each temperature. -1 The remaining conditions were the same as those in the isothermal adsorption experiment (pH=5.0, adsorbent dosage 50 mg, solution volume 50 mL, adsorption time 120 min, shaker speed 150 r / min).

[0048] Cyclic regeneration experiment: using 0.1 mol·L⁻¹ -1 HCl was used as the desorbent. The adsorbed UiO-66-EDTA was added to the desorbent and shaken for 2 hours to desorb. After washing with deionized water until neutral, the mixture was dried and the next round of adsorption experiments was performed. This process was repeated five times. The conditions for each adsorption experiment were: initial Cu... 2+ Concentration 100 mg·L -1 The conditions were: pH=5.0, temperature 298 K, adsorption time 120 min, and shaker speed 150 r / min. The adsorption capacity was recorded for each test, and the retention rate was calculated.

[0049] The calculation formulas involved in the above test process are as follows: Adsorption capacity: q e =(C0-C e V / m; q t =(C0-C t V / m; In dynamic experimental studies, pseudo-first-order dynamic equations and pseudo-second-order dynamic equations are used: The pseudo-first-order rate equation is: ln(q) e -q t )=lnqe –k1t; Quasi-second-order rate equation: t / q t =1 / k2q e 2 +t / q e ; In the isothermal adsorption experimental study, two models, Langmuir isothermal adsorption and Freundlich isothermal adsorption, were used: Langmuir isothermal adsorption: C t / q t =1 / q m ·K L +C t / q m ; Freundlich isothermal adsorption: lnq t =lnK F +(1 / n)lnC t ; Adsorption thermodynamics: lnb = ΔS / R - ΔH / RT; lnb=2.303log(q e / C e ); Among them, C0, C t C e Cu 2+ Initial concentration, concentration at any time t, equilibrium concentration, mg / L; V is Cu 2 + The volume of the solution, L; m is the mass of the adsorbent, mg; q t The adsorption amount at a certain moment, in mg·g -1 ;q e The adsorption amount at equilibrium is expressed in mg·g. -1 ;q m The saturation adsorption capacity is expressed in mg·g. -1 .

[0050] 2. Test Results (1) Effect of pH value on adsorption performance Figure 5 The effects of UiO-66 and UiO-66-EDTA on Cu in the pH range of 2.0–6.0 were demonstrated. 2+ The adsorption capacity variation was investigated. Results showed that the adsorption capacity increased rapidly with increasing pH regardless of whether the modification was performed or not. Furthermore, the adsorption capacity after EDTA-2Na modification was significantly higher than that before modification. At pH 5.0, q... e It reaches its maximum at pH, after which q decreases with increasing pH. e It gradually decreases. The lower adsorption capacity under low pH conditions is attributed to the large amount of H₂ in the solution.+ With Cu 2+ Competing for active sites on the adsorbent surface, the amino group undergoes protonation and becomes positively charged, reacting with Cu. 2+ Electrostatic repulsion occurs. As pH increases, the degree of deprotonation of functional groups increases, carboxyl groups exist in the -COO- form, and the surface negative charge density increases, thus increasing the repulsion of Cu. 2+ The electrostatic attraction and coordination chelation abilities are significantly enhanced. The adsorption capacity decreases slightly at pH 6.0, possibly due to Cu. 2+ This is related to the initial formation of trace amounts of hydroxide precipitate.

[0051] (2) Adsorption kinetics test results Figure 6 In the table, 'a' represents the effect of time on the adsorption amount, 'b' represents the fitted pseudo-first-order kinetic rate equation, and 'c' represents the fitted pseudo-second-order kinetic rate equation. Detailed data are shown in Table 1. Figure 6 As shown in Table 1, the adsorption capacity increases rapidly in the initial stage of adsorption, then slows down after 60 min, and reaches equilibrium at 120 min. The equilibrium adsorption capacity q e 93.00 mg·g -1 The experimental data were nonlinearly fitted using quasi-first-order and quasi-second-order kinetic models, respectively. The correlation coefficient R of the quasi-second-order kinetic model was... 2 =0.9998, and the equilibrium adsorption capacity calculated by the model is 92.80 mg·g⁻¹. -1 The results are in high agreement with experimental values, indicating that UiO-66-EDTA has a high effect on Cu 2+ The adsorption process is dominated by chemisorption as the rate-controlling step.

[0052] Table 1 (3) Isothermal (298 K) adsorption test results UiO-66-EDTA at 298 K for Cu 2+ The isothermal adsorption data are shown in Table 2. e As C0 increases, the concentration initially rises rapidly and then levels off. As C0 increases from 20 to 200 mg / L, q... e The concentration increased from 19.35 mg / g to 175.64 mg / g. The Langmuir and Freundlich models were used for fitting, as shown below. Figure 7 As shown in a and b. Langmuir equation: C e / q e = 1 / (q m ·K L ) + C e / q m With C e / q e For Ce Plot the graph, regression equation: C e / q e = 0.00537C e + 0.0300, R 2 = 0.998. q m = 186.3 mg / g, K L = 0.179L / mg. Freundlich equation: ln qe = lnK F + (1 / n)lnC e Using lnq e For lnC e Plot the graph; regression equation: lnq e = 0.412lnC e +3.16, R 2 = 0.904. n = 2.43, K F = 23.6. Langmuir model R 2 (0.998) is better than Freundlich (0.904), indicating that Cu 2+ It exhibits uniform monolayer adsorption on UiO-66-EDTA. L = 1 / (1+K L • CO) in the range of 0.027–0.218 indicates favorable adsorption. q m = 186.3 mg / g, EDTA grafting significantly improved the adsorption capacity. The isothermal adsorption results are consistent with the kinetic pseudo-second-order model, both pointing to the dominant role of chelation coordination.

[0053] Table 2 (4) Adsorption thermodynamic test results Table 3 lists the effects of UiO-66-EDTA on Cu at five different temperatures. 2+ The adsorption thermodynamic data are as follows: As the temperature increases from 298 K to 318 K, the equilibrium adsorption capacity gradually increases from 93.0 mg / g to 95.7 mg / g. Increasing the temperature favors adsorption. The increase in adsorption capacity with increasing temperature indicates that this adsorption process is endothermic. At high temperatures, Cu... 2+ The diffusion rate is accelerated, and the active sites interact with Cu. 2+ The interaction between them is also more complete.

[0054] Table 3 Distribution coefficient b=q e / C elnb = -2476.3 / T + 10.90. Plotting lnb against 1 / T yields the van der Hoff curve (i.e., the adsorption thermodynamic fitting plot, as shown in the image). Figure 8 (As shown). The curves exhibit a good linear relationship. Thermodynamic parameters are calculated from the slope and intercept of the straight line. Enthalpy change ΔH and entropy change ΔS are obtained using the formula lnb = ΔS / R − ΔH / RT. Gibbs free energy change ΔG is calculated using the formula ΔG = −RTlnb. Thermodynamic parameters are listed in Table 4.

[0055] Table 4 Table 4 shows that ΔG is negative at all five temperatures. The absolute value of ΔG increases with increasing temperature. At 298 K, ΔG = -6.41 kJ / mol, increasing to -8.20 kJ / mol at 318 K. This result indicates that Cu 2+ The adsorption on UiO-66-EDTA is a spontaneous process, and the spontaneity increases with higher temperatures. ΔH is positive at 20.59 kJ / mol, confirming that the adsorption process is endothermic. The ΔH value falls within the typical energy range of chemisorption (20 to 40 kJ / mol), further confirming that chemisorption plays a dominant role. ΔS is positive at 90.62 J / (mol·K). Cu 2+ When adsorbed onto the surface of UiO-66-EDTA, the Cu originally surrounding it 2+ The surrounding hydrated water molecules are released. This release increases the system's disorder. The molecular arrangement at the solid-liquid interface also becomes more disordered. These factors collectively lead to an increase in entropy. Thermodynamic analysis results, along with kinetic and isothermal findings, mutually support each other, pointing to a chemisorption mechanism primarily based on chelation coordination.

[0056] (5) Cyclic performance test results Figure 9 The graph shows the results of five adsorption-desorption cycles of UiO-66-EDTA. Figure 9 It can be seen that after five cycles, UiO-66-EDTA has a significant effect on Cu. 2+ The adsorption capacity gradually decreased, but it still maintained an adsorption capacity of over 50 mg / g by the fifth cycle. The adsorption capacity after five cycles (q) e The concentrations were 93.0, 85.0, 77.0, 68.0, and 56.0 mg / g, respectively. This demonstrates that UiO-66-EDTA is a relatively efficient adsorbent for removing Cu from polluted water. 2+ This adsorbent exhibits relatively good stability.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a UiO-66-EDTA composite material, characterized in that, Includes the following steps: UiO-66 was mixed with EDTA-2Na and water, and the mixture was heated to react and obtain UiO-66-EDTA.

2. The preparation method of the UiO-66-EDTA composite material as described in claim 1, characterized in that, The ratio of UiO-66 to EDTA-2Na and water is 100 mg: 1.6870 g: 50 mL.

3. The preparation method of the UiO-66-EDTA composite material as described in claim 1, characterized in that, The heating reaction is carried out at a temperature of 50-70 °C for 20-28 h.

4. The method for preparing the UiO-66-EDTA composite material as described in claim 1, characterized in that, The preparation steps of UiO-66 include: mixing zirconium source, terephthalic acid, N,N-dimethylformamide and acetic acid, and reacting at 110-130 °C for 20-28 h to obtain UiO-66.

5. The method for preparing the UiO-66-EDTA composite material as described in claim 4, characterized in that, The zirconium source includes zirconium oxychloride octahydrate.

6. The method for preparing the UiO-66-EDTA composite material as described in claim 4, characterized in that, The ratio of zirconium source, terephthalic acid, N,N-dimethylformamide, and acetic acid is 0.3220 g:0.1660 g:40 mL:1.0 mL.

7. The method for preparing the UiO-66-EDTA composite material as described in claim 4, characterized in that, The reaction process at 110-130 °C for 20-28 h also includes steps of cooling, centrifugation, collecting the solid product and washing it alternately with N,N-dimethylformamide and methanol, followed by drying.

8. A UiO-66-EDTA composite material prepared by the preparation method according to any one of claims 1-7.

9. The application of the UiO-66-EDTA composite material as described in claim 8 in the adsorption and removal of copper ions in water.

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