Lead ion detection and adsorption composite film based on EuW10 / ZIF-8 composite material and preparation method

Abstract

The invention relates to an EuW10 / ZIF-8 composite material, a lead ion (Pb < 2 + >) detection and adsorption composite membrane based on the EuW10 / ZIF-8 composite material and a preparation method of the composite membrane, the composite membrane material can rapidly and sensitively detect Pb < 2 + > in a water body and efficiently remove Pb < 2 + > in wastewater, and meanwhile, the composite membrane material has good recycling performance. The EuW10 / ZIF-8 / PVA / PIL composite membrane disclosed by the invention has high-sensitivity detection capability on Pb, effective detection can be realized in a range of 1-106 mu M, and the detection limit is as low as 1 mu M. Other common heavy metal ions have extremely small interference on detection, the selectivity is strong, the concentration of Pb < 2 + > in water can be accurately detected, and a reliable basis is provided for water quality monitoring.

Description

Technical Field

[0001] The present invention belongs to the field of environmental monitoring and wastewater treatment technology, and specifically relates to a EuW 10 / ZIF-8 composites, and EuW-based 10 Pb / ZIF-8 composites 2+ ) detection and adsorption composite membrane and its preparation method, suitable for rapid, sensitive detection and efficient removal of Pb in water 2+ . Background Art

[0002] Lead ions (Pb 2+ ) is a highly toxic heavy metal pollutant that is widely present in industrial wastewater and other substances. 2+ It is widely used in many common materials, such as gasoline, batteries, pigments, cosmetics, food additives, toys, etc. It can seep into groundwater from reservoirs with high heavy metal (HM) content. Even extremely low concentrations of lead ions (Pb 2+ ) may also cause a variety of health problems. In addition, due to the lead ion (Pb 2+ ) is widely used and enriched, and Pb 2+ Detection of Pb in environmental water, food and plant samples 2+ Levels are crucial to reducing environmental pollution and public health risks.

[0003] Currently, the detection of Pb 2+ Current methods include atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and reversed-phase high-performance liquid chromatography (RP-HPLC). Each of these methods has its own unique characteristics: AAS and ICP-AES offer high sensitivity and precision, making them suitable for analyzing a wide range of sample types; RP-HPLC excels in separating complex mixtures; however, all methods suffer from disadvantages such as expensive equipment, complex and time-consuming procedures, and impracticality for field application. Choosing an appropriate detection method requires consideration of factors such as the target, sample characteristics, and available resources. Therefore, the development of a fluorescent detection material that is rapid, sensitive, convenient, low-cost, and specific is crucial.

[0004] Na9[EuW 10 O 36 ]·32H2O (abbreviated as EuW 10) as a typical representative of lanthanide polyoxometalates (Ln-POM), exhibits significant and strong red light emission characteristics, and its fluorescence system has advantageous spectral parameters such as narrow-band emission characteristics, wide-range Stokes shift and microsecond-long afterglow. However, the practical application of this material is limited: on the one hand, the inorganic crystalline / amorphous solid phase has the defect of limited material processing performance, and it is difficult to recycle in practical applications; on the other hand, it is easy to produce fluorescence self-quenching effect in an aqueous environment, and at the same time, it has the inherent defect of insufficient solubility and dispersibility in hydrophobic organic media. In order to break through such technical bottlenecks, researchers are carrying out systematic improvements on the above defects in order to optimize EuW 10 functional application potential. 10 The field of fluorescence enhancement research has formed a multi-dimensional optimization strategy, including loading into porous materials, cationic surfactant coating, polymer / biomolecule composite assembly and ionic liquid mediated modification. Therefore, it is necessary to find other easily available environmentally friendly materials to combine with EuW 10 Modification through self-assembly to improve fluorescence properties and construct new supramolecular nanostructures are extremely attractive hotspots.

[0005] This application selects EuW with excellent luminescence performance 10 As a polyacid raw material, it is loaded onto the ZIF-8 surface with a large surface area to design and synthesize EuW 10 -ZIF luminescent composites, thereby enhancing and improving EuW 10 The fluorescence intensity and compensation of EuW 10 The fluorescence self-quenching effect is easy to occur in aqueous solution; then, the prepared EuW 10 -ZIF-8 was loaded onto the surface of the positively charged PVA / PIL membrane to prepare a new stable cyclic Pb 2+ Composite membrane with sensitive detection and adsorption of metal ions. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a EuW 10 / ZIF-8 composites, and EuW-based 10 / ZIF-8 composite material lead ion detection and adsorption composite membrane, the composite membrane can quickly and sensitively detect Pb in water 2+ , and efficiently remove Pb from wastewater 2+ , and has good recycling performance.

[0007] The present invention also provides the above-mentioned EuW-based 10 Preparation method of lead ion detection and adsorption composite membrane based on ZIF-8 composite material.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A EuW 10 A method for preparing a ZIF-8 composite material comprises the following steps: Step 1: Synthesize EuW 10 ; Step 2: Preparation of EuW 10 / ZIF-8 composite materials; EuW 10 Disperse in deionized water to obtain solution 1; dissolve 2-methylimidazole in methanol to obtain solution 2; mix solution 1 and solution 2, add methanol solution containing zinc nitrate, mix well, place at 40-60 ° C for crystallization for 5-7 hours, and obtain EuW through solid-liquid separation, washing, and drying. 10 / ZIF-8 composite materials.

[0009] Specifically, in step 2, the EuW 10 The mass ratio of the 2-methylimidazole to zinc nitrate can be 0.03-0.3:1, and the mass ratio of the 2-methylimidazole to zinc nitrate can be 1.05-1.1:1.

[0010] Furthermore, the synthesis of EuW in step 1 10 Specifically, sodium tungstate is dissolved in deionized water (stirred at 85±10℃ for 0.5-2h to promote complete dissolution), pH is adjusted to 7.0-7.4 with glacial acetic acid, europium nitrate aqueous solution is added, and the reaction is maintained at 80-90℃ for 0.5-2h. After cooling to room temperature, colorless crystals are precipitated, which are washed and dried to obtain EuW. 10 ; The molar ratio of sodium tungstate to europium nitrate is preferably 10:1.

[0011] The present invention provides EuW prepared by the above preparation method 10 / ZIF-8 composite materials.

[0012] The present invention provides a method based on the EuW 10 A method for preparing a Pb²⁺ detection and adsorption composite membrane of a ZIF-8 composite material comprises the following steps: Dissolve polyvinyl alcohol in deionized water (heat and stir at 90±5℃ for 0.5-2 h to promote complete dissolution, and then cool to room temperature), add polyionic liquid solution, and heat and stir at 70±10℃ for 0.5-2 h to mix evenly; add EuW 10 / ZIF-8 composite material solution, stirred evenly, and vacuum dried to obtain EuW 10 / ZIF-8 / PVA / PIL composite film.

[0013] Specifically, the mass ratio of the polyvinyl alcohol to the polyionic liquid can be 1:0.2-0.5. 10 The mass ratio of the ZIF-8 composite material can be 1:0.05-0.15.

[0014] The present invention provides Pb prepared by the above method. 2+ Detection and adsorption of EuW 10 / ZIF-8 / PVA / PIL composite film.

[0015] The present invention also provides the EuW 10 / ZIF-8 / PVA / PIL composite membrane for detecting Pb in water 2+ , and adsorption of Pb in water 2+ The application specifically includes the following steps: placing the composite membrane in a Pb 2+ In water samples, Pb is removed by adsorption 2+ ; At the same time, the fluorescence characteristics of the composite membrane are used to detect Pb in water 2+ concentration.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) Excellent detection performance: EuW of the present invention 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ With highly sensitive detection capability, the detection range is 1-10 6 It can effectively detect Pb in the μM range, with a detection limit as low as 1 μM; and other common heavy metal ions have minimal interference with its detection, with strong selectivity, and can accurately detect Pb in water. 2+ The concentration provides a reliable basis for water quality monitoring.

[0017] 2) Strong adsorption capacity: EuW of the present invention 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ It has good adsorption capacity, with a maximum adsorption capacity of 58.6 mg / g. It can maintain high adsorption efficiency in a wide pH range (5-6) and can effectively remove Pb from water. 2+ , reducing the degree of water pollution.

[0018] 3) Good stability and cyclability: EuW of the present invention 10 The ZIF-8 / PVA / PIL composite membrane exhibits excellent stability, with stable fluorescence intensity under neutral and weakly alkaline conditions, ensuring accurate test results. Furthermore, it exhibits excellent cyclability: after three cycles, the fluorescence intensity retained 57.31% of its initial value, and the adsorption capacity remained at 62.54% of its baseline value, significantly reducing operational costs and meeting the requirements of sustainable development.

[0019] 4) Simple preparation process: EuW of the present invention 10 The preparation process of the / ZIF-8 / PVA / PIL composite membrane is simple to operate, the required raw materials are common and easy to obtain, the cost is low, and it is suitable for large-scale industrial production and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is EuW 10 Synthesis of / ZIF-8 / PVA / PIL composite membrane and its effect on Pb 2+ Schematic diagram of fluorescence detection and adsorption; Figure 2 Different samples of ZIF-8, EuW 10 and EuW 10 FT-IR infrared spectrum (left) and Raman spectrum (right) of ZIF-8 are used to prove the 10 The successful synthesis of ZIF-8 and their composite; Figure 3 Different samples of ZIF-8, EuW 10 and EuW 10 / ZIF-8 XRD spectrum to further verify the structure and composition of the composite film; Figure 4 EuW with different contents 10 The fluorescence intensity of the composite film material at 254 nm reflects the composite film in different EuW 10 The fluorescence changes of the content are used to study the fluorescence properties of the composite film; Figure 5 It is EuW 10 / ZIF-8 / PVA / PIL (a) and EuW 10 The relative fluorescence intensity of the / PVA / PIL (b) composite film immersed in water for different time periods reflects the relative fluorescence intensity of the composite film under different Pb 2+ The fluorescence changes of the composite membrane were further studied based on the concentration of Pb 2+ detection capabilities; Figure 6 Different time (a), different Pb 2+ EuW at the initial solution concentration (b), different dosages (c) and different pH (d) 10 / ZIF-8 / PVA / PIL composite membrane adsorption efficiency; Figure 7 It is EuW 10 Pb adsorption on / ZIF-8 / PVA / PIL composite membrane 2+Pseudo-first-order kinetics (a), pseudo-second-order kinetics (b), Langmuir (c), and Freundlich (d) isothermal models; Figure 8 It is EuW 10 Fluorescence spectra and relative intensity diagram (c) of ZIF-8 / PVA / PIL composite membrane in different metal ion (a) and different anion (b) solutions; Figure 9 It is EuW 10 / ZIF-8 / PVA / PIL composite films at different Pb 2+ Concentration (10 -2 , 10 -3 , 10 -4 , 10 -5 , 10 -6 mol / L) (a), as well as the relative intensity diagram and the optical photograph of the fluorescence changes under 254 nm UV light irradiation (b); Figure 10 :Pb content of composite membranes at different pH values (3, 5, 7, 9, 11) 2+ Fluorescence spectrum (a) and relative intensity (b) in solution; Figure 11 It is EuW 10 Adsorption and detection of Pb by / ZIF-8 / PVA / PIL composite 2 Mechanism diagram; Figure 12 It is EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ Figure 4. Cyclic capability test of fluorescence detection and adsorption. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described in detail below in conjunction with the embodiments, but the protection scope of the present invention is not limited thereto.

[0022] In the following examples, unless otherwise specified, the raw materials used are all common commercial products that can be purchased directly or can be prepared using conventional techniques in the art.

[0023] Room temperature refers to 25±5°C.

[0024] Example 1: Preparation of composite membrane This embodiment gives EuW 10 Preparation, synthesis process and Pb / ZIF-8 / PVA / PIL composite membrane 2+ Fluorescence detection and adsorption indication Figure 1 , details are as follows.

[0025] Step 1: EuW10 Synthesis of: The operation was carried out according to the Peacock-Weakley method. Accurately weigh 6.6 g of sodium tungstate (Na2WO4·2H2O, 20 mmol), completely dissolve it in 16 mL of deionized water, and continue stirring at a constant temperature of 85 °C for 1 h. Slowly add glacial acetic acid to adjust the pH of the solution to 7.2. Then, add 1.6 mL of Eu(NO3)3·6H2O solution (containing Eu(NO3)3·6H2O 0.882 g, 2 mmol) at a uniform rate, and maintain the reaction at 85 °C for 1 h. After the reaction is completed, cool to room temperature, at which time a large amount of colorless crystals precipitate. Wash the crystals three times with deionized water to remove impurities, and then dry them in a vacuum drying oven for 24 h to obtain pure EuW 10 .

[0026] Step 2: Preparation of EuW 10 / ZIF-8 composite materials Different quality EuW 10 (10 mg, 25 mg, 50 mg, 75 mg, 100 mg) were evenly dispersed in 4 mL of deionized water to form solution 1; 0.3284 g of 2-methylimidazole was accurately weighed and dissolved in 6.5 mL of methanol to obtain solution 2. At room temperature, solution 2 was added dropwise to solution 1 while magnetically stirring at room temperature for 5 minutes, and then 6.5 mL of methanol solution containing 0.2975 g of zinc nitrate was quickly injected. Ultrasonic dispersion was performed for 5 minutes to ensure that all components were thoroughly mixed. The mixed solution was transferred to a polytetrafluoroethylene reactor and crystallized at 50 ° C for 6 h. After the reaction was completed, the precipitate was collected by centrifugation, washed three times with deionized water and methanol respectively to remove unreacted substances, and finally dried in vacuum at 60 ° C for 12 h to obtain EuW. 10 / ZIF-8 composite materials.

[0027] Step 3: Preparation of polyionic liquid PVBIMBr PVBIMBr was synthesized via a free radical copolymerization method. Specifically, 2 g of 1-vinyl-3-butylimidazolium bromide ionic liquid monomer (VBIMBr) and 20 mg of azobisisobutyronitrile (AIBN) were dispersed in 10 mL of N,N-dimethylformamide (DMF). The solution was stirred continuously at 70°C under an argon atmosphere for 16 hours. The product was then precipitated in ethyl acetate and dried in a vacuum oven at 50°C for 12 hours to obtain purified PVBIMBr.

[0028] Step 4: Preparation of EuW 10 / ZIF-8 / PVA / PIL composite film Dissolve 1 g of polyvinyl alcohol (PVA) in 10 mL of deionized water and heat at 90 °C with stirring for 2 h until completely dissolved. After cooling to room temperature, add 2 mL of polyionic liquid (P(VBIMBr)) solution (100 mg / mL) and heat at 70 °C with stirring for 2 h to mix thoroughly. Then add 10 mL of EuW 10 / ZIF-8 solution (10 mg / mL), stirred evenly, and the mixed solution was transferred to a glass Petri dish and dried under vacuum at 60 °C for 12 h to form EuW 10 / ZIF-8 / PVA / PIL composite film.

[0029] Comparison: EuW 10 Construction of / PVA / PIL composite film: Dissolve 1 g of polyvinyl alcohol (PVA) in 10 mL of deionized water and heat at 90 °C with stirring for 2 h until completely dissolved. After cooling to room temperature, add 2 mL of polyionic liquid (P(VBIMBr)) solution (100 mg / mL) and heat at 70 °C with stirring for 2 h to mix thoroughly. Then add 10 mL of EuW 10 The mixed solution was transferred to a glass culture dish and dried under vacuum at 60 °C for 12 h to form EuW 10 / PVA / PIL composite film.

[0030] Example 2: Characterization of materials FT-IR spectroscopy analysis: Fourier transform infrared spectrometer was used to analyze ZIF-8 and EuW 10 and EuW 10 / ZIF-8 was tested, and the results are shown in Figure 2 .like Figure 2 As shown in EuW 10 In the infrared spectrum, 933 cm -1 The characteristic peak at is attributed to Eu-O a bond vibration; 839 cm -1 and 793 cm -1 The characteristic peaks at correspond to EuW 10 ν(WO d ) and ν(WO b -W) bond, proving EuW 10 The infrared spectrum of ZIF-8 is at 430 cm -1 and 1587 cm -1 The absorption peaks appearing at correspond to the stretching vibration of the Zn-N bond and the characteristic vibration peaks of the C=N bond in the imidazole ligand, indicating that ZIF-8 was successfully prepared. 10 In the infrared spectrum of / ZIF-8, EuW10 The characteristic peak of EuW is slightly shifted, and the characteristic absorption peak of ZIF-8 exists at the same time, which confirms that 10 / ZIF-8 was successfully prepared.

[0031] Raman spectroscopy analysis (see Figure 2 ): Raman spectroscopy was used to characterize the relevant samples. The characteristic vibration peaks of ZIF-8 are distributed in the range of 647-1516 cm -1 interval, including 692, 1155 and 1467cm -1 The positions correspond to the imidazole ring folding vibration, CN stretching vibration and methyl bending vibration respectively. 10 The characteristic scattering peaks are concentrated at 955, 430, and 368 cm -1 , which is highly consistent with the literature reports. 10 The spectrum of the ZIF-8 composite material retains two sets of characteristic peaks, but there is a slight shift in the peak positions, indicating that the structural integrity of the two components is maintained during the composite process and there is lattice distortion.

[0032] XRD pattern analysis: X-ray diffractometer was used to analyze the EuW 10 , ZIF-8 and its composite EuW 10 The crystal structure of ZIF-8 was characterized. The diffraction pattern of pure ZIF-8 was consistent with the literature at characteristic peak positions (such as 7.3°, 10.4°, and 12.7°), and highly consistent, confirming its typical zeolite framework structure. 10 The diffraction peak position of the ZIF-8 composite material is almost the same as that of ZIF-8, indicating that the main skeleton maintains structural integrity during the composite process, and the characteristic peak intensity is relatively reduced, which is attributed to the EuW 10 The lattice distortion effect caused by the packaging process. In addition, further analysis found that EuW 10 EuW appeared at 5.8° and 9.1° in the ZIF-8 composite. 10 The characteristic diffraction signal of WO in FT-IR spectrum is d (960 cm -1 ) and Eu-O (578cm -1 ) and Raman spectra (368 cm -1 ,430 cm -1 and 955 cm -1 ), which together confirm that the polyacid is complexed with ZIF-8.

[0033] Example 3: EuW 10 Fluorescence properties of / ZIF-8 / PVA / PIL composite films In addition, we have different EuW10 The fluorescence intensity of the composite material with the content of EuW was tested to explore the 10 EuW / ZIF-8 10 Best ratio. Figure 4 For EuW 10 Fluorescence spectra of composite films containing 10, 25, 50, 75, and 100 mg of ZIF-8 at 254 nm. As shown in the figure, the fluorescence emission spectrum of the composite film shows a series of characteristic sharp peaks in the range of 550-720 nm. 0 →7F 1 )、617 nm(5D 0 →7F 2 )、651 nm(5D 0 →7F 3 ) and 702 nm (5D 0 →7F 4 ) have four typical emission bands, and these discrete radiative transition processes have been confirmed to originate from the ligand-metal charge transfer (LMCT) mechanism. In addition, the fluorescence intensity of the material at 617 nm increases with the increase of EuW 10 The content of EuW increases, which may be attributed to the 10 The synergistic effect between EuW and ZIF-8. 10 When the content is 50mg, the fluorescence intensity reaches the maximum, so we choose EuW 10 EuW in ZIF-8 10 The material with a content of 50 mg was loaded on the PVA / PIL membrane and the Pb 2+ Adsorption and fluorescence detection performance tests.

[0034] In addition, we also compared the EuW 10 / ZIF-8 / PVA / PIL composite film and EuW 10 The stability of the composite material was studied by measuring the fluorescence intensity of the / PVA / PIL composite film immersed in water for different time periods. Figure 5 .from Figure 5 It can be seen from a: EuW 10 The fluorescence intensity of the / ZIF-8 / PVA / PIL composite film hardly changed within 30 min of immersion in aqueous solution. 10 The fluorescence intensity of the / PVA / PIL composite film decreased with the extension of the immersion time in water. At 20 min, the composite film was almost completely fluorescence quenched, and the fluorescence intensity decreased by 95.37%. 10 / ZIF-8 / PVA / PIL composite membrane has excellent stability in water and overcomes the EuW 10 The disadvantage is that it is easy to produce fluorescence self-quenching effect in aqueous solution.

[0035] Example 4: EuW 10 Pb / ZIF-8 / PVA / PIL composite membrane 2+ Adsorption performance EuW 10 / ZIF-8 / PVA / PIL composite membrane was used as the research object, and the effects of adsorption time, initial concentration, adsorbent dosage and solution pH on the Pb 2+ The influence of adsorption performance.

[0036] Contact time effect Figure 6 a shows EuW 10 / ZIF-8 / PVA / PIL composite film for Pb 2+ Curve of adsorption amount changing with time (initial concentration Pb 2+ :20 mg / L;Solution volume: 50 mL;Adsorbent mass: 20 mg) The figure shows that: EuW 10 / ZIF-8 / PVA / PIL composite film on Pb 2+ (II) During the contact process, from 0 to 25 min, the composite film has a strong 2+ The adsorption amount of Pb continued to increase rapidly with the extension of contact time. This is because the abundant functional sites in the film can quickly 2+ Through the combination of coordination and electrostatic interaction, the adsorption amount and adsorption rate approached saturation in 30-60 min, and finally reached adsorption equilibrium (adsorption rate was 82.27%; adsorption amount was 41.13 mg / g).

[0037] Initial concentration dependence like Figure 6 As shown in b, when Pb 2+ When the initial concentration of the solution increased from 10 mg / L to 50 mg / L (solution volume: 50 mL; adsorbent mass: 20 mg), EuW 10 The maximum adsorption capacity of the / ZIF-8 / PVA / PIL composite membrane showed a trend of increasing first and then reaching equilibrium, while the adsorption efficiency showed a trend of increasing first and then decreasing. This is attributed to the rich active sites provided by the multi-level pore structure of the material. With the increase of the metal ions in the solution, the adsorption efficiency of EuW 10The active sites of the / ZIF-8 / PVA / PIL composite membrane are in contact with more metal ions. However, when the concentration exceeds the critical value, the adsorption sites of the adsorption membrane are gradually completely occupied, and the metal ions on the surface of the composite membrane repel each other with the metal ions in the solution, competing with the site saturation effect, resulting in a decrease in adsorption efficiency, indicating that too high an initial concentration will destroy the adsorption equilibrium state. 10 / ZIF-8 / PVA / PIL composite membrane in the adsorption of 40 mg / L Pb 2+ The peak adsorption capacity (Q max Pb 2+ =58.6 mg / g).

[0038] Dosage effect Figure 6 c, EuW 10 / ZIF-8 / PVA / PIL composite membrane in 20 mg / L Pb 2+ The solution has the best adsorption effect, so we added 20 mg / L Pb in 50 mL of the solution. 2+ In the solution, the effect of adsorbent quality on the adsorption effect of the material was explored, and the results are shown in Figure 6 With EuW 10 The dosage of Pb / ZIF-8 / PVA / PIL composite membrane increased from 5, 10, 20, 30 mg to 40 mg. 2+ The removal rate shows a gradual upward trend, and the adsorption amount shows a downward trend of first increasing and then decreasing. This phenomenon is consistent with the adsorption site saturation theory, which shows that when the active sites on the surface of the material are completely occupied, the interaction between the metal ions and the adsorbent reaches a dynamic equilibrium. This phenomenon occurs because the specific adsorption capacity per unit adsorbent gradually decreases with the increase in the amount of adsorbent. Although increasing the amount of adsorbent may increase the number of active adsorption sites, the utilization efficiency of these sites will decrease due to the limited concentration of metal ions. Therefore, the adsorption capacity per unit mass of adsorbent will decrease. Adsorption of Pb 2+ The optimal dosage is 20 mg (equilibrium removal rate reaches 80.2%, maximum adsorption capacity is 40.1 mg / g).

[0039] pH response characteristics like Figure 6 d, in (20 mg EuW 10 / ZIF-8 / PVA / PIL composite membrane, 50 mL 20 mg / L Pb 2+ solution, adsorption for 30 min), the effect of different solution pH on the adsorption process was investigated. 2+ In alkaline solution, precipitation will be formed, thus affecting the adsorption results. 2+The solutions were adjusted to pH = 2, 3, 4, 5, and 6. As shown in the figure, EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ The adsorption rates of EuW were 30.8%, 45.9%, 62.1%, 80.3% and 88.59% respectively. The best adsorption rate was obtained at pH 6. The reason for this result may be that under acidic conditions, EuW 10 EuW on the surface of / ZIF-8 / PVA / PIL composite film 10 / ZIF-8 decomposes slightly under acidic conditions, and the composite membrane contains Pb 2+ In addition, as the pH value increases, the H + The concentration also decreases, EuW 10 The / ZIF-8 / PVA / PIL composite membrane can also provide sufficient active sites to adsorb Pb 2+ .

[0040] Example 5: EuW 10 Pb adsorption on / ZIF-8 / PVA / PIL composite membrane 2+ Kinetic and isothermal models.

[0041] To further study EuW 10 / ZIF-8 / PVA / PIL composite membrane materials for Pb 2+ For the adsorption, we selected an initial concentration of 20 mg / L Pb 2+ The adsorption data of the solution were fitted with first- and second-order kinetics, such as Figure 7 As shown in a and b, during the adsorption process, EuW 10 The PFO and PSO kinetic models of the / ZIF-8 / PVA / PIL composite membrane material have high coefficients (PFO: 0.9853; PSO: 0.9832), indicating that both physical adsorption and chemical adsorption play an important role in the adsorption process of the material. In addition, the Langmuir and Freundlich isotherm models were used to analyze the adsorption of EuW 10 Pb adsorption on / ZIF-8 / PVA / PIL composite membrane 2+ The equilibrium data were linearly fitted, such as Figure 7 As shown in c and d, compared with the Freundlich isotherm model (R 2 =0.8998), the Langmuir isotherm model has a higher correlation coefficient (R 2 =0.9699). The results show that EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ The adsorption is monolayer adsorption, and the adsorption sites are evenly distributed on the surface. Therefore, it can be inferred that EuW10 / ZIF-8 / PVA / PIL composite film for Pb 2+ Adsorption may involve a combination of ion exchange, coordination, strong hydrogen bonding, and electrostatic interactions.

[0042] Example 6: EuW 10 Pb / ZIF-8 / PVA / PIL composite membrane 2+ Detection performance Selectivity and sensitivity: Lead ion (Pb 2+ ) is a toxic heavy metal pollutant with bioaccumulative properties, which can cause irreversible damage to animal and plant organisms and seriously endanger public health and safety. The development of sensitive and reliable technology for the detection of trace lead ions in water and food is of great practical significance. In this study, different heavy metal ion solutions (Cr 3+ 、Cd 2+ 、Cu 2+ , Pb 2+ , 10 -3 M) to conduct selectivity experiments on fluorescent composite membranes, and distilled water was used as a blank control. The results are shown in Figure 8 As shown in a and b, after immersion for 3 min, each metal ion produced different degrees of fluorescence quenching effect on the composite membrane. 2+ 、Cd 2+ Cr 3+ The fluorescence intensity attenuation was 50.65%, 21.52% and 24.16% respectively, which may be related to the color development characteristics of the metal solution and the physical shielding effect caused by surface adsorption. 2+ 、Cd 2+ Cr 3+ 、Hg 2 + ) compared to Pb 2+ EuW 10 The luminescence quenching effect of the / ZIF-8 / PVA / PIL composite film was significant. -3 At M concentration, Pb 2+ Make EuW 10 / ZIF-8 / PVA / PIL composite film fluorescence quenching 94.98%, while other ions have little effect, indicating that the EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ The detection is highly selective and sensitive, with a detection limit of 1 μM. To verify the effect of anions in metal salts on the fluorescence detection of composite membranes, this study further set NaCl and KNO3 solutions as anion controls ( Figure 8 b). The experimental results show that the concentration of Cl ⁻ and NO3 ⁻There is no significant effect on the fluorescence intensity of the composite film, which proves that the material has no significant effect on the fluorescence intensity of the composite film. 2+ It has highly selective detection capabilities. In summary, the fluorescent composite membrane exhibits excellent detection sensitivity and anti-interference properties for lead ions in complex matrices.

[0043] In addition, in order to further explore the composite membrane's effect on Pb 2+ To improve the detection capability, we immersed the film in different concentrations of Pb 2+ Solution (10 -2 , 10 -3 , 10 -4 , 10 -5 and 10 -6 mol / L Pb 2+ solution), measuring the film's Pb 2+ The limit of fluorescence detection. Figure 9 As shown in c, the composite film has different concentrations of Pb 2+ After solution treatment, the film was observed under UV light. The red fluorescence of the film 2+ As the concentration increases, it gradually weakens and disappears. Figure 9 b are films immersed in different concentrations of Pb 2+ The fluorescence spectra and relative intensity diagrams below show that the composite film has a 6 It has fluorescence detection capability at μM.

[0044] Environmental adaptability: Research EuW 10 Pb / ZIF-8 / PVA / PIL composite membranes in different water environments 2+ The fluorescence quenching effect has more important practical significance. We explored the effect of immersion in different pH aqueous solutions on the fluorescence detection of the composite membrane, such as Figure 10 We measured the fluorescence intensity changes of the composite membrane after immersing it in solutions with pH values of 3, 5, 7, 9, and 11 for 10 min. 10 The fluorescence intensity of the / ZIF-8 / PVA / PIL composite film did not change much between pH 7 and 11, which was mainly attributed to the fact that ZIF-8 and PVA / PIL had certain alkaline stability, which stabilized the EuW 10 The fluorescence intensity of the outer ZIF-8 framework has a certain alkaline stability, which can protect the EuW 10 However, when the pH value is below 5, the fluorescence intensity of the composite film decreases significantly, which is mainly because a few ZIF-8 frameworks are destroyed under acidic conditions, resulting in the partial destruction of EuW 10 Dissolved in the solution. In summary, the composite membrane is a strong 2+ It has good fluorescence detection capability.

[0045] Example 7: EuW 10 Fluorescence detection mechanism of / ZIF-8 / PVA / PIL composite membrane EW 10 / ZIF-8 / PVA / PIL composite membrane for detection of Pb 2+ It is divided into two steps. First, ZIF-8 adsorbs Pb through coordination, strong hydrogen bonding and electrostatic interaction. 2+ to the surface of the composite membrane; then Eu in the composite membrane 3+ With Pb 2+ interaction, partially blocking the energy transfer path and weakening the ligands in POM to Eu 3+ The "antenna effect" of Pb 2+ The fluorescence detection of Figure 11 .

[0046] Example 8: EuW 10 Recycling performance of / ZIF-8 / PVA / PIL composite membrane Figure 12 Given EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ Results of the fluorescence detection and adsorption cycle test. As can be seen from the figure: after three cycles, EuW 10 / ZIF-8 / PVA / PIL composite membrane for Pb 2+ The fluorescence intensity decayed to 57.31% of the initial value, and the adsorption capacity remained at 62.54% of the original baseline value. Despite the attenuation, the skeleton structure can still effectively capture the target ions, meeting the requirements of adsorption retention rate in industrial applications, reducing unit processing costs, and having good recycling performance.

Claims

1. A EuW 10 A method for preparing a ZIF-8 composite material, characterized in that: The following steps are involved: Step 1: Synthesize EuW 10 ; Step 2: Preparation of EuW 10 / ZIF-8 composite materials; EuW 10 Disperse in deionized water to obtain solution 1; dissolve 2-methylimidazole in methanol to obtain solution 2; mix solution 1 and solution 2, add methanol solution containing zinc nitrate, mix well, place at 40-60℃ for 5-7 hours, separate solid and liquid, wash, and dry to obtain EuW 10 / ZIF-8 composite materials.

2. EuW as claimed in claim 1 10 / ZIF-8 composite membrane preparation method, characterized in that, In step 2, the EuW 10 The mass ratio of the 2-methylimidazole to zinc nitrate is 0.03-0.3:1, and the mass ratio of the 2-methylimidazole to zinc nitrate is 1.05-1.1:

1.

3. EuW as claimed in claim 1 10 / ZIF-8 composite membrane preparation method, characterized in that, Synthesize EuW as described in step 1 10 Specifically, sodium tungstate was dissolved in deionized water, the pH was adjusted to 7.0-7.4 with glacial acetic acid, and an aqueous europium nitrate solution was added. The reaction was maintained at 80-90 °C for 0.5-2 h, and the mixture was cooled to room temperature to precipitate colorless crystals. After washing and drying, EuW was obtained. 10 ; The molar ratio of sodium tungstate to europium nitrate is 10:

1.

4. EuW prepared by the preparation method according to any one of claims 1 to 3 10 / ZIF-8 composite materials.

5. A EuW according to claim 4 10 Pb / ZIF-8 composites 2+ The preparation method of the detection and adsorption composite membrane is characterized in that: The steps include: Dissolve polyvinyl alcohol in deionized water, add polyionic liquid solution, mix well, add EuW 10 The / ZIF-8 composite material solution is stirred evenly and then vacuum dried to obtain.

6. Pb as claimed in claim 5 2+ The preparation method of the detection and adsorption composite membrane is characterized in that: The mass ratio of the polyvinyl alcohol to the polyionic liquid is 1:0.2-0.

5.

7. The method for preparing a Pb²⁺ detection and adsorption composite membrane according to claim 5, wherein: The polyvinyl alcohol and EuW 10 The mass ratio of ZIF-8 composite material is 1:0.05-0.

15.

8. Pb prepared by the method according to any one of claims 5 to 7 2+ Detection and adsorption composite membrane.

9. The composite membrane according to claim 8 is used to detect Pb in water 2+ application.

10. The composite membrane according to claim 8 absorbs Pb in water 2+ application.

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