A composite material for efficient adsorption of heavy metal ions Pb 2+ and a preparation method and application thereof

Abstract

The application discloses a composite material for efficiently adsorbing heavy metal ions Pb 2+ and a preparation method and application thereof, and belongs to the technical field of water treatment. The application prepares two metal organic frameworks (UiO-67) with different morphologies under two different solvent conditions, modifies the UiO-67 by using rhodanine-3-acetic acid (Rd) through a post-modification method, and prepares a UiO-67-Rd composite material, so that the activity of a functional group is improved and the functional group can selectively adsorb Pb 2+ . The composite material has excellent adsorption performance on heavy metal ions Pb 2+ , the maximum adsorption capacity of the composite material on Pb 2+ reaches 309.8 mg g ‑1 , and the composite material has good reusability. The composite material prepared by the application adsorbs heavy metal ions Pb 2+ through chelation and electrostatic interaction, and the composite material is used for treating Pb 2+ in manure biogas slurry, so that the treatment is simple and effective, the high-value utilization degree of the manure biogas slurry is improved, and the pollution caused by heavy metals to the environment is reduced.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for efficiently adsorbing heavy metal ions Pb. 2+ Composite materials, their preparation methods, and applications. Background Technology

[0002] Biogas slurry, a byproduct of biogas projects, is the residue produced by the anaerobic fermentation of organic matter such as manure, crop straw, and agricultural byproducts. It contains various nutrients and physiologically active substances essential for crop growth and can be used as a high-quality organic fertilizer in agriculture. However, in modern animal husbandry, mineral elements are widely added to feed to promote livestock growth and prevent disease. Most of these mineral elements originate from ores and contain toxic heavy metal pollutants such as Cd, As, Pb, Cr, and Cu. Therefore, the residual concentration of these toxic heavy metal pollutants in biogas slurry is relatively high. Since heavy metals cannot be decomposed by microorganisms, they easily accumulate in organisms through the food chain and transform into more toxic metal-organic compounds. If directly discharged into the environment without proper treatment and utilization, it will cause secondary pollution. To achieve the safe and resource-based utilization of biogas slurry, biological treatment technology is the most widely used process. This technology degrades heavy metals in biogas slurry under aerobic or anaerobic conditions. However, residual toxic heavy metal pollutants in biogas slurry cannot be completely removed in the same way as organic carbon. Furthermore, in chemical methods for removing heavy metals, most adsorbents suffer from small adsorption capacity and low adsorption efficiency. These problems have become a bottleneck restricting the safe utilization of biogas slurry. Therefore, inventing a composite material that can efficiently adsorb heavy metal ions is of paramount importance in the fields of environmental protection and water treatment technologies. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention provides a highly efficient adsorption method for heavy metal ions Pb. 2+ The composite material, its preparation method, and its application are described. This composite material exhibits excellent adsorption performance for heavy metal ions, particularly Pb. 2+ The maximum adsorption capacity reached 309.8 mg g. -1 The composite material of this invention is used to adsorb heavy metal ions Pb from biogas slurry. 2+ The method is simple and effective, which can improve the utilization rate of biogas slurry and reduce the pollution of heavy metals to the environment.

[0004] The present invention adopts the following technical solution:

[0005] A highly efficient adsorption method for heavy metal ions Pb 2+ The method for preparing the composite material includes the following steps:

[0006] (1) After mixing ZrCl4 with N,N-dimethylformamide, acetic acid or formic acid is added and ultrasonicated to form zirconium acetate or zirconium formate;

[0007] (2) Add 4,4'-biphenyldicarboxylic acid to the solution containing zirconium acetate or zirconium formate obtained in step (1), heat and then sonicate to obtain a homogeneous solution;

[0008] (3) After heating the homogeneous solution obtained in step (2), cool it to room temperature and purify it. Soak the obtained product in ethanol, centrifuge and dry it to obtain UiO-67-AC or UiO-67-FA.

[0009] (4) Mix ratannin-3-acetic acid, dichloromethane and ethyl acetate and sonicate for 8-15 min to obtain a mixed solution. Add UiO-67-AC or UiO-67-FA obtained in step (3) to the mixed solution, stir and reflux, cool to room temperature, purify the product and dry it to obtain UiO-67-AC-Rd or UiO-67-FA-Rd.

[0010] Further, in step (1) above, the mass-to-volume ratio of ZrCl4 to N,N-dimethylformamide is 7-8 g / L, preferably 7.67 g / L; the volume ratio of N,N-dimethylformamide to acetic acid or formic acid is 4.5-5.5:0.8-1.2; preferably 5:1.

[0011] Further, in step (1) above, the mixing temperature is 40-50°C and the time is 15-25 min, preferably 45°C and 20 min; the ultrasonic temperature is 40-50°C and the time is 100-150 min, preferably 45°C and 120 min.

[0012] Furthermore, in step (2) above, the mass ratio of 4,4'-biphenyldicarboxylic acid to ZrCl4 is 16-18:22-24, preferably 17:23.

[0013] Furthermore, in step (2) above, the heating temperature is 80-100℃ and the time is 15-25 min, preferably 100℃ and 20 min; the ultrasonic treatment time is 10-20 min, preferably 15 min.

[0014] Further, in step (3) above, the heating temperature is 100-150°C and the time is 20-28h; preferably 130°C for 24h; the above purification refers to washing with N,N-dimethylformamide, deionized water, acetone and ethanol 2-3 times after centrifugation, preferably washing with N,N-dimethylformamide, deionized water, acetone and ethanol 2 times; the soaking time in ethanol is 10-14h, and the above drying temperature is 65-75°C, preferably 70°C.

[0015] Further, in step (4) above, the mass-to-volume ratio of the mixture of rotannin-3-acetic acid, dichloromethane, and ethyl acetate is 37-39 g / L, preferably 38.2 g / L; the volume ratio of dichloromethane to ethyl acetate is 0.8-1.2:0.8:1.2, preferably 1:1; and the mass ratio of rotannin-3-acetic acid to the above UiO-67-AC or UiO-67-FA is 4:1.

[0016] Further, in step (4) above, the temperature of stirring and reflux is 35-45°C, preferably 40°C, and the time is 20-28h, preferably 24h; the above purification refers to washing with methanol 4-5 times, preferably 4 times, after centrifugation, and then washing with ethanol 2-3 times, preferably 2 times; the above drying temperature is 65-75°C, preferably 70°C.

[0017] The above-mentioned high-efficiency adsorption of heavy metal ions Pb 2+ Preparation method of composite material, and preparation of highly efficient adsorption material for heavy metal ions Pb 2+ Composite materials.

[0018] The above-mentioned highly efficient adsorption of heavy metal ions Pb 2+ Composite materials adsorb heavy metal ions Pb in manure biogas slurry 2+ Applications in [the field].

[0019] By adopting the above technical solution, the beneficial effects of the present invention are as follows:

[0020] The principle of the composite material of this invention: Metal-organic frameworks (MOFs) are a novel type of organic-inorganic hybrid material, composed of metal ions (clusters or secondary structural units SBUs) and organic ligands (or linkers) through coordination bonds. They possess excellent physicochemical properties such as high porosity, large surface area, uniformity, and thermochemical stability. UiO-MOFs (UiO-66, UiO-67, UiO-68, and UiO-69, etc.) are a type of MOF, composed of Zr 4+ It is composed of carboxylic acids. Because UiO-67-Rd contains specific functional ligands and Rd contains abundant O, N, and S atoms, according to the hard and soft acid-base theory, Pb (Lewis acid) has a strong affinity for S (Lewis base) and O (Lewis base), respectively, thus increasing the affinity for Pb. 2+ Adsorption capacity.

[0021] This invention prepares two different morphologies of UiO-67-FA (FA, formic acid as solvent) and UiO-67-AC (AC, acetic acid as solvent) under two different solvent conditions (UiO-67-FA and UiO-67-AC are collectively referred to as UiO-67). Through a post-synthetic modification method, UiO-67 is modified with tannin-3-acetic acid (Rd) to obtain UiO-67-Rd composite materials (UiO-67-FA-Rd and UiO-67-AC-Rd, respectively) to improve the activity of functional groups and selectively adsorb Pb. 2+ The adsorption mechanism of UiO-67-Rd with metal ions is mainly chelation and electrostatic interaction.

[0022] The composite material of this invention is used to treat heavy metal ions Pb 2+ Adsorption occurs by dispersing the adsorbent into the sample solution using a rotary shaker. Based on the strength of the interaction between the adsorbent and the target analyte, the analyte is effectively transferred to the adsorbent material, thereby increasing the analyte-adsorbent contact area to remove pollutants. This method is effective for Pb. 2+ The maximum adsorption capacity reached 309.8 mg g. -1 The treatment method is simple and effective. It can be used to treat biogas slurry, improve the utilization rate of biogas slurry, and reduce the pollution of the environment caused by heavy metals. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the synthesis process of UiO-67-Rd.

[0024] Figure 2 X-ray diffraction patterns of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd.

[0025] Figure 3 Infrared spectra of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd.

[0026] Figure 4 The mapping diagrams for UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd are shown, where e represents UiO-67-AC, f represents UiO-67-FA, g represents UiO-67-AC-Rd, and h represents UiO-67-FA-Rd.

[0027] Figure 5 Thermogravimetric curves of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd are shown.

[0028] Figure 6 The N2 adsorption / desorption curves of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd at 77K are shown.

[0029] Figure 7 This is a pore size distribution diagram for UiO-67-AC.

[0030] Figure 8 This is a pore size distribution diagram for UiO-67-FA.

[0031] Figure 9 The pore size distribution diagram is for UiO-67-FA-Rd.

[0032] Figure 10 The pore size distribution diagram is for UiO-67-AC-Rd.

[0033] Figure 11 Adsorption of Pb by UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd under different pH conditions 2+ Comparison chart of capabilities.

[0034] Figure 12 The graph shows a comparison of the adsorption capacities of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd at different temperatures.

[0035] Figure 13 The graph shows a comparison of the adsorption capacities of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd at different times.

[0036] Figure 14 A comparison chart of the adsorption capacities of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd.

[0037] Figure 15 The adsorption cycle diagrams are for UiO-67-FA-Rd and UiO-67-AC-Rd.

[0038] Figure 16 For coexisting ion pairs Pb 2+ Effect of adsorption on UiO-67-FA-Rd and UiO-67-AC-Rd.

[0039] Figure 17The image shows the XPS spectrum of UiO-67-AC-Rd after adsorption, where a represents the full peak, and b, c, d, e, f and g represent the peaks of Pb4f, S2p, Zr3d, N1s, C1s and O1s, respectively. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments.

[0041] Example 1

[0042] This embodiment provides a method for efficiently adsorbing heavy metal ions Pb. 2+ The composite material specifically includes the following steps:

[0043] (1) Prepare reagents and materials:

[0044] Zirconium chloride (ZrCl4, 98.0%) was purchased from Shanghai Energy Chemical Co., Ltd.; 4,4'-biphenyl dicarboxylic acid (BPDC, 99.0%) and razotannin-3-acetic acid (Rd) were both purchased from Aladdin Company; dichloromethane (CH2Cl2) was an analytical grade reagent purchased from Sinopharm Chemical Reagent Co., Ltd.; N,N-dimethylformamide (DMF), acetic acid, methanol, ethanol, ethyl acetate, and other reagents were all analytical reagents purchased from Tianjin Jiangtian Chemical Co., Ltd.; Pb 2+ (Concentration is 1000 μg / mL) -1 The standard stock solution was provided by National Standard (Beijing) Testing and Certification Co., Ltd., and the actual sample came from the biogas slurry of the manure and straw large and medium-sized biogas project of Leshan Qinli Agricultural Development Co., Ltd., and was filtered with a 0.45μm aqueous membrane before use.

[0045] (2) Synthesis of UiO-67-AC:

[0046] 0.4602 g ZrCl4 was mixed with 60 mL DMF and heated at 45 °C for 20 min. Then, 12 mL acetic acid (AC) was added and the mixture was sonicated at 45 °C for 120 min to completely form zirconium acetate. 0.3390 g BPDC was added to the zirconium acetate formation solution and heated at 100 °C for 20 min. The mixture was then sonicated for 15 min. Finally, the homogeneous solution was transferred to a high-pressure reactor and heated at 130 °C for 24 h. After cooling to room temperature, the resulting white product was centrifuged and washed twice with DMF, deionized water, acetone, and ethanol, respectively. The prepared product was soaked in ethanol for 12 h, centrifuged, and then dried at 70 °C to obtain UiO-67-AC.

[0047] (3) Synthesis of UiO-67-AC-Rd:

[0048] Weigh 1.9122 g of Rd and place it in a 100 mL round-bottom flask. Add 25 mL of dichloromethane and 25 mL of ethyl acetate respectively. Sonicate the mixture for 10 min to completely dissolve Rd and obtain a mixed solution. Add 0.5 g of UiO-67-AC synthesized in step (2) to the mixed solution and stir under reflux at 40 °C for 24 h. After cooling to room temperature, centrifuge the pale yellow product and wash it 4 times with methanol and 2 times with ethanol. After centrifugation, dry the product in a 70 °C oven to obtain UiO-67-AC-Rd. The synthesis process is as follows: Figure 1 As shown.

[0049] Example 2

[0050] This embodiment provides a method for efficiently adsorbing heavy metal ions Pb. 2+ The composite material specifically includes the following steps:

[0051] (1) Prepare reagents and materials:

[0052] Zirconium chloride (ZrCl4, 98.0%) was purchased from Shanghai Energy Chemical Co., Ltd.; 4,4'-biphenyl dicarboxylic acid (BPDC, 99.0%) and razotannin-3-acetic acid (Rd) were both purchased from Aladdin Company; dichloromethane (CH2Cl2) was an analytical grade reagent purchased from Sinopharm Chemical Reagent Co., Ltd.; N,N-dimethylformamide (DMF), formic acid, methanol, ethanol, ethyl acetate, and other reagents were all analytical reagents purchased from Tianjin Jiangtian Chemical Co., Ltd.; Pb 2+ (Concentration is 1000 μg / mL) -1 The standard stock solution was provided by National Standard (Beijing) Testing and Certification Co., Ltd., and the actual sample came from the biogas slurry of the manure and straw large and medium-sized biogas project of Leshan Qinli Agricultural Development Co., Ltd., and was filtered with a 0.45μm aqueous membrane before use.

[0053] (2) Synthesis of UiO-67-FA:

[0054] 0.4602 g ZrCl4 was mixed with 60 mL DMF and heated at 45 °C for 20 min. Then, 12 mL formic acid (FA) was added and the mixture was sonicated at 45 °C for 120 min to completely form zirconium formate. 0.3390 g BPDC was added to the zirconium formate solution and heated at 100 °C for 20 min. The mixture was then sonicated for 15 min to obtain a homogeneous solution. Finally, the homogeneous solution was transferred to a high-pressure reactor and heated at 130 °C for 24 h. After cooling to room temperature, the resulting white product was centrifuged and washed twice with DMF, deionized water, acetone, and ethanol, respectively. The prepared product was soaked in ethanol for 12 h, centrifuged, and then dried at 70 °C to obtain UiO-67-FA.

[0055] (3) Synthesis of UiO-67-FA-Rd:

[0056] Weigh 1.9122 g of Rd and place it in a 100 mL round-bottom flask. Add 25 mL of dichloromethane and 25 mL of ethyl acetate to the flask. Sonicate the mixture for 10 min to completely dissolve Rd and obtain a mixed solution. Add 0.5 g of UiO-67-FA synthesized in step (2) to the mixed solution and stir under reflux at 40 °C for 24 h. After cooling to room temperature, centrifuge the pale yellow product and wash it 4 times with methanol and 2 times with ethanol. After centrifugation, dry the product in a 70 °C oven to obtain UiO-67-FA-Rd. The synthesis process is as follows: Figure 1 As shown.

[0057] Experimental Example 1

[0058] 1. X-ray diffraction was used to observe the UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd prepared in Examples 1 and 2. The observation results are as follows: Figure 2 As shown.

[0059] Depend on Figure 2 It can be seen that the two main diffraction peaks 2θ of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd are between 5 and 7°, and their intensities are the diffraction peaks of the (111) and (200) crystal planes, respectively, which have good crystallinity and the same topological structure.

[0060] 2. The UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd prepared in Examples 1 and 2 were observed using an infrared spectrometer. The observation results are as follows: Figure 3 As shown.

[0061] Depend on Figure 3It can be seen that the C-OH and COC stretching vibrations of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd are respectively at wavenumber 1182 cm⁻¹. -1 and 1010~1046cm -1 At 1609cm -1 ~1410cm -1 The absorption peak within the range is due to the C-C skeletal stretching vibration originating from the benzene ring in the ligand 4,4'-biphenyl-dicarboxylic acid, at 848 cm⁻¹. -1 and 760cm -1 The peak at 1135 cm⁻¹ is caused by Zr-O-Zr stretching vibration. After introducing Rd into UiO-67-FA and UiO-67-AC, a peak at 1135 cm⁻¹ can be observed. -1 1240cm -1 and 1718cm -1 The absorption peaks at wavenumbers represent the stretching vibrations of C=N, CN, and NH, respectively.

[0062] 3. Observe the morphology and physical microstructure of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd under a microscope to obtain mapping diagrams. The results are as follows: Figure 4 As shown.

[0063] Depend on Figure 4 As can be seen from the elemental composition diagrams of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd and UiO-67-AC-Rd, the elemental compositions of UiO-67-AC and UiO-67-FA are C, O and Zr respectively, and the elemental compositions of UiO-67-FA and UiO-67-AC-Rd are C, O, Zr, N and S respectively.

[0064] 4. The thermal stability of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd, and UiO-67-FA-Rd was investigated by thermogravimetric analysis (TGA), and thermogravimetric curves of the four samples were plotted. Figure 5 As shown.

[0065] Depend on Figure 5It can be seen that the TGA curves of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd, and UiO-67-FA-Rd consist of three weight loss stages: the first stage is solvent and water vapor removal (25–150 °C); the second stage is DMF removal and dehydroxylation of monocarboxylic acid ligands from the zirconium oxide clusters (150–500 °C); and the third stage (above 500 °C) is... The combustion of the mechanical binder molecules decomposes UiO-67, causing the skeleton to decompose. Therefore, the weight loss rates of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd are 35.12%, 54.33%, 33.94% and 39.9%, respectively. The weight loss rate of the composite material UiO-67-Rd is less than that of UiO-67 and UiO-67, indicating that the composite material was successfully synthesized.

[0066] 5. The specific surface area and pore size distribution of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd were calculated by nitrogen isothermal adsorption-desorption. The results are as follows: Figures 6-10 As shown.

[0067] Depend on Figures 6-10 It can be seen that the Brunauer Emmett-Teller (BET) specific surface areas of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd, and UiO-67-FA-Rd are 1779.08 m². 2 g -1 390.12m 2 g -1 100.61m 2 g -1 and 35.34m 2 g -1 The pore volumes of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd, and UiO-67-FA-Rd are 0.83 cm³. 3 g -1 0.28cm 3 g -1 0.15cm 3 g -1 and 0.03cm 3 g -1The isotherms of all samples were typical type I isotherms, with a sharp increase at low P / P0 ratios, indicating microporous properties. Compared to UiO-67, UiO-67-Rd showed a more significant reduction in specific surface area and pore volume. This is because Rd was synthesized and modified onto the UiO-67 crystals, reducing the number of UiO-67 molecules. The resulting composite material, UiO-67-Rd, provides more active sites, which can increase the concentration of heavy metal ions such as Pb. 2+ Adsorption efficiency.

[0068] Experimental Example 2

[0069] The UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd prepared in Examples 1 and 2 were used to treat Pb 2+ Adsorption experiments were conducted.

[0070] Methods for representing adsorption effect:

[0071]

[0072]

[0073]

[0074]

[0075] Among them, the adsorption material for Pb 2+ equilibrium adsorption capacity (q) e mg g -1 ) from the initial concentration (c0, mg mL) -1 ) and equilibrium concentration (c e mg mL -1 ) Perform the calculation; V represents the solution volume (L); M represents the adsorbent mass (g); q max Indicates the maximum adsorption capacity; K L K represents the Langmuir constant; F 1 and 1 / n represent the adsorption equilibrium constants, respectively; R represents the removal rate of Pb2+ by the adsorbent (R, %).

[0076] 1. The adsorption capacity of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd was determined under different pH conditions.

[0077] 2 mg of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd were weighed separately, along with 10 mL of biogas slurry from the large-scale biogas project using manure and straw from Leshan Qinli Agricultural Development Co., Ltd. The biogas slurry was filtered through a 0.45 μm aqueous membrane before use. The Pb content in the biogas slurry was... 2+ The initial concentration was 30 μg / mL. -1 The filtered biogas slurry and 2 mg of adsorbent were placed in a 25 mL sample bottle. The pH of the solution was adjusted using 0.1 M dilute hydrochloric acid and 0.1 M NaOH, with the pH values ​​adjusted to 2, 3, 4, 5, 6, 7, and 8, respectively. The sample bottle was then placed in a rotary shaker and shaken at 25 °C and 200 rpm for 6 hours. The supernatant was then filtered through a 0.45 μm inorganic membrane, and the adsorption experiment was performed. The experimental results are as follows: Figure 11 As shown.

[0078] Depend on Figure 11 It can be seen that under different pH conditions, Pb 2+ Mainly Pb 2+ Pb(OH) + It exists in the forms of Pb(OH)2, Pb(OH)3, etc., from Figure 11 It can be seen that within the pH range of 2 to 6, Pb 2+ The adsorption capacity of Pb increases rapidly in the pH range of 7–8. 2+ The adsorption capacity increases slowly or even shows a decreasing trend; due to the lower pH, the surface functional groups involved in metal coordination are protonated, and the protonated surface interacts with Pb. 2+ The Coulombic repulsion between them reduces adsorption; at pH > 5, Pb 2+ The precipitation further reduced the adsorption capacity, therefore the optimal pH condition for the adsorption of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd is 6.

[0079] 2. The adsorption capacity of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd was determined at different temperatures.

[0080] 2 mg of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd were weighed separately, along with 10 mL of biogas slurry from the large-scale biogas project using manure and straw from Leshan Qinli Agricultural Development Co., Ltd. The biogas slurry was filtered through a 0.45 μm aqueous membrane before use. The Pb content in the biogas slurry was... 2+ The initial concentration was 30 μg / mL. -1The filtered biogas slurry and 2 mg of adsorbent were placed in a 25 mL sample bottle. The pH was adjusted to 6, and the sample bottle was placed in a rotary shaker. The shaker was operated at 200 rpm for 6 hours at temperatures of 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, and 42℃. The supernatant was then filtered through a 0.45 μm inorganic membrane, and the adsorption results were measured. The experimental results are as follows: Figure 12 As shown.

[0081] Depend on Figure 12 It can be seen that the adsorption amounts of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd, and UiO-67-FA-Rd are the highest when the adsorption temperature is 30℃. When T>30℃, the adsorption amount gradually decreases with increasing temperature. Therefore, higher temperatures can accelerate the adsorption of Pb. 2+ The activity of Pb promotes 2+ Diffusion to the adsorbent surface increases Pb 2+ The probability of collision with adsorption sites on the adsorbent surface is considered, therefore the optimal adsorption temperature is 30℃.

[0082] 3. Determine the optimal adsorption time for UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd.

[0083] 2 mg of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd were weighed separately, along with 10 mL of biogas slurry from the large-scale biogas project using manure and straw from Leshan Qinli Agricultural Development Co., Ltd. The biogas slurry was filtered through a 0.45 μm aqueous membrane before use. The Pb content in the biogas slurry was... 2+ The initial concentration was 30 μg / mL. -1 The filtered biogas slurry and 2 mg of adsorbent were placed in a 25 mL sample bottle. The pH was adjusted to 6, and the sample bottle was placed in a rotary shaker. The shaker was operated at 200 rpm for 25 min, 50 min, 75 min, 100 min, 125 min, 150 min, 175 min, 200 min, 225 min, and 250 min at 30℃. The supernatant was then filtered through a 0.45 μm inorganic membrane, and the adsorption results were measured. The experimental results are shown below. Figure 13 As shown.

[0084] Depend on Figure 13 It can be seen that, with the increase of time, the adsorption material for Pb... 2+ The adsorption capacity gradually increases, then gradually stops increasing or even decreases, due to the interaction between the adsorbent material surface and free Pb.2+ As the concentration of metal ions decreases, the amount of adsorption increases, resulting in a reduction in available adsorption sites. Therefore, the optimal adsorption time is 60 min.

[0085] 4. Determine the adsorption capacity of UiO-67-AC, UiO-67-FA, UiO-67-AC-Rd and UiO-67-FA-Rd under optimal experimental conditions.

[0086] 2 mg of UiO-67-AC, UiO-67-FA, UiO-67-FA-Rd, and UiO-67-AC-Rd were weighed separately, along with 10 mL of biogas slurry from the large-scale biogas project using manure and straw from Leshan Qinli Agricultural Development Co., Ltd. The biogas slurry was filtered through a 0.45 μm aqueous membrane before use. The Pb content in the biogas slurry was... 2+ The initial concentration was 30 μg / mL. -1 The filtered biogas slurry and 2 mg of adsorbent were placed in 25 mL sample bottles. The pH was adjusted to 6, and the sample bottles were placed in a rotary shaker. After shaking at 200 rpm for 60 min at 30℃, the supernatant was filtered through a 0.45 μm inorganic membrane, and the adsorption experiment was performed. The experimental results are as follows: Figure 14 As shown.

[0087] Depend on Figure 14 It can be seen that the adsorption capacity of UiO-67-Rd is higher than that of UiO-67. UiO-67-Rd contains abundant adsorption active sites such as S, N, and O. According to the hard-soft acid-base (HSAB) theory, metal ions are more likely to combine with specific functional ligands (such as amino, hydroxyl, thiol, and phosphorus groups) to form coordination bonds through ion exchange, electrostatic interaction, or chelation, which is beneficial to Pb. 2+ Adsorption and enrichment around the active site.

[0088] Experimental Example 3

[0089] 1. Examine the repeatability of UiO-67-Rd

[0090] The repeatability of UiO-67-Rd was tested through multiple cyclic adsorption experiments to evaluate the practicality of the adsorbent. This is because H in HCl... + Since the adsorbed metal ions are more easily replaced, after adsorption using an adsorbent material, 0.1M HCl is used as the eluent for elution. The eluted adsorbent material is then used again to elute Pb. + Adsorption was performed repeatedly, and the repeatability was measured. The results are as follows: Figure 15 As shown.

[0091] Depend on Figure 15 It can be seen that UiO-67-Rd affects Pb in four consecutive cycles. 2+It still maintains good stability; with increasing cycle time, UiO-67-Rd improves its resistance to Pb. 2+ The adsorption capacity gradually decreased because of the unreleased Pb. 2+ The adsorption capacity gradually decreased due to the binding of adsorption sites, possibly caused by mechanical deformation. The adsorption capacity of UiO-67-AC-Rd and UiO-67-FA-Rd remained at 80.3% and 74.6%, respectively. However, after multiple repeat experiments, the morphology of UiO-67-AC-Rd and UiO-67-FA-Rd materials remained almost unchanged. UiO-67-Rd is a type of reusable adsorbent with good performance.

[0092] 2. Investigate the adsorption of Pb by other substances on UiO-67-Rd. 2+ Interference in the adsorption process

[0093] Using the optimal experimental conditions determined in Example 2, NaCl, KCl, NaNO3, KNO3, MgCl2, Na2CO, and MgSO4 were selected as interfering substances. The concentrations of the interfering substances and Pb... 2+ The initial concentration was consistent, 30 μg / mL. -1 UiO-67-AC-Rd and UiO-67-FA-Rd were used to target substances containing interfering substances and Pb. 2+ The solution was adsorbed, and the results were as follows: Figure 16 As shown.

[0094] Depend on Figure 16 It can be seen that the interfering substances NaCl, KCl, NaNO3, KNO3, and MgCl2 affect Pb 2+ The adsorption performance is less affected; however, the anionic SO42- is affected. 2- and CO3 2- For Pb 2+ The adsorption performance is affected, inhibiting the adsorption of Pb by the adsorption material. 2+ The adsorption capacity of UiO-67-Rd for Pb is considered to be that of polyvalent ions, which are considered interfering ions due to their similar structure and hydration energy in aqueous solution. 2+ The adsorption capacity is reduced.

[0095] Three types of biogas slurry samples were collected and analyzed using the standard addition method (quantitative analysis volume: 10 mL). The same mass of UiO-67-AC-Rd was added to each of the different samples, and the Pb content in the solution after adsorption was measured using an electrochemical method. 2+ The concentration of Pb adsorbed by UiO-67-AC-Rd was calculated to determine its concentration. 2+ The spiked recoveries for the samples were 80.8–84.7%, 82.7–91.3%, and 88.6–94.8%, respectively. The relatively low spiked recoveries were due to interference from the complex matrix of the actual samples.

[0096] Test Example 4

[0097] 1. For adsorbed Pb 2+ The UiO-67-AC-Rd was then characterized.

[0098] X-ray photoelectron spectroscopy and other methods were used to analyze the adsorbed Pb 2+ The physicochemical properties of the UiO-67-AC-Rd were characterized, and the results are as follows: Figure 17 As shown.

[0099] Depend on Figure 17 From a, we can see that Pb is adsorbed. 2+ The UiO-67-AC-Rd precipitate is mainly composed of Zr, C, O, N, S, and Pb elements; Figure 17 b shows that the adsorbed Pb 4f spectrum exhibits two characteristic peaks at 140.09 eV (Pb 4f7 / 2) and 144.87 eV (Pb 4f5 / 2); Figure 17 As can be seen from c, the spectrum of S2p has changed significantly, indicating the adsorption of Pb. 2+ The spectral peaks of the C=S and CS bonds shift significantly towards higher binding energies, indicating that the S atom participates in the binding of Pb. 2+ Coordination reaction; by Figure 17 From d, f, and other data, it can be seen that UiO-67-AC-Rd adsorbs Pb. 2 + The XPS spectra of Zr3d, C1s, and O1s before and after are almost identical, but from Figure 17 f shows the addition of a new CS absorption peak in the C1s spectrum; Figure 17 As can be seen from e, adsorption of Pb 2+ The NH absorption peak at 407.64 eV of the N1s atom is significantly enhanced, indicating that the N atom participates in the Pb atom absorption. 2 + The coordination reaction of Pb; the above results indicate that Pb 2+ Effectively adsorbed in the UiO-67-AC-Rd composite material, UiO-67-AC-Rd interacts with Pb through chelation and electrostatic interactions. 2+ Adsorption, for Pb 2+ It has a strong adsorption capacity.

Claims

1. Use of a composite material with high efficiency in adsorbing heavy metal ions Pb 2+ in adsorbing heavy metal ions Pb 2+ in adsorbing heavy metal ions Pb from biogas slurry, characterized in that, The high-efficiency adsorption heavy metal ion Pb 2+ The preparation method of the composite material comprises the following steps: (1) mixing ZrCl4 and N, N-dimethylformamide, then adding acetic acid or formic acid to the mixture and ultrasonicating to form zirconium acetate or zirconium formate; (2) adding 4, 4'-diphenyldicarboxylic acid to the solution containing zirconium acetate or zirconium formate obtained in step (1), heating and then ultrasonicating to obtain a uniform solution; (3) heating the uniform solution obtained in step (2), cooling to room temperature, purifying, immersing the obtained product in ethanol, centrifuging and drying to obtain UiO-67-AC or UiO-67-FA; (4) mixing rhodanine-3-acetic acid, dichloromethane and ethyl acetate and ultrasonicating for 8-15 min to obtain a mixed solution, adding UiO-67-AC or UiO-67-FA obtained in step (3) to the mixed solution, stirring and refluxing, cooling to room temperature, purifying the product and drying to obtain UiO-67-AC-Rd or UiO-67-FA-Rd; In step (4), the mass-volume ratio of rhodanine-3-acetic acid to the mixture of dichloromethane and ethyl acetate is 37-39 g / L; the volume ratio of dichloromethane to ethyl acetate is 0.8-1.2:0.8:1.2; the mass ratio of rhodanine-3-acetic acid to the UiO-67-AC or UiO-67-FA is 3.5-4.5:0.8-1.2; the temperature for stirring and refluxing in step (4) is 35-45 ℃, and the time is 20-28 h; the purification refers to washing 4-5 times with methanol and then 2-3 times with ethanol after centrifugation; and the drying temperature is 65-75 ℃.

2. Use according to claim 1, characterized in that, In step (1), the mass-volume ratio of ZrCl4 to N, N-dimethylformamide is 7-8 g / L, and the volume ratio of N, N-dimethylformamide to acetic acid or formic acid is 4.5-5.5:0.8-1.

2.

3. Use according to claim 1, characterized in that, In step (1), the mixing temperature is 40-50 ℃, and the time is 15-35 min; and the ultrasonicating temperature is 40-50 ℃, and the time is 100-150 min.

4. Use according to claim 1, characterized in that, In step (2), the mass ratio of 4, 4'-diphenyldicarboxylic acid to ZrCl4 is 16-18:22-24.

5. The use according to claim 1, characterized in that, In step (2), the heating temperature is 80-100 ℃, and the time is 15-25 min; and the ultrasonicating time is 10-20 min.

6. Use according to claim 1, characterized in that, In step (3), the heating temperature is 100-150 ℃, and the time is 20-28 h; the purification refers to washing 2-3 times with N, N-dimethylformamide, deionized water, acetone and ethanol, respectively, after centrifugation; the immersing time in ethanol is 10-14 h; and the drying temperature is 65-75 ℃.

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