Magnetic core-shell type cadmium ion imprinted polymer and preparation method and application thereof

Abstract

The application provides a novel magnetic core-shell type cadmium ion imprinted polymer and a preparation method and application thereof, and belongs to the technical field of polymer materials. The novel magnetic core-shell type cadmium ion imprinted polymer is prepared by using SiO2 coated nano Fe3O4 as a carrier, PBTCA as a ligand, and MBA as a crosslinking agent, and by using surface imprinting technology and chemical grafting, and the maximum adsorption capacity of the imprinted polymer to Cd 2+ can reach 29.82 mg / g, the adsorption process can reach a basic balance within 20 min, and the whole adsorption process conforms to a pseudo-second-order kinetics model and a Langmuir isothermal adsorption model. The adsorption of the imprinted polymer to Cd 2+ is a spontaneous, endothermic and entropy-increasing process, and in a mixed solution containing Cd 2+ , Ni 2+ , Co 2+ , Zn 2+ , the distribution coefficient of the imprinted polymer to Cd 2+ reaches 643.3 mL / g, which proves that the imprinted polymer has the ability of selectively adsorbing Cd 2+ ions.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a novel magnetic core-shell type cadmium ion imprinted polymer, its preparation method, and its application. Background Technology

[0002] Among various heavy metal ions, cadmium (Cd) is one of the most dangerous and carcinogenic metals because it is widely used in metal alloys, electroplating, colorants, fertilizers, and charging. Cd is a highly toxic and non-essential element; long-term accumulation in the human body can cause serious damage to the brain, bones, and kidneys. Various human diseases such as renal insufficiency, bone degeneration, pulmonary insufficiency, liver damage, and hypertension are caused by the presence of cadmium in the environment. Therefore, research on Cd in water bodies is crucial. 2+ The removal technology is of great significance.

[0003] Currently, it is used to remove Cd from the aquatic environment 2+ The main methods include chemical precipitation, ion exchange, membrane filtration, and electrochemistry. However, these methods still have certain drawbacks, such as complex operation, high operating and maintenance costs, and complex subsequent treatment processes. In contrast, adsorption is considered more promising due to its simple design, easy and reliable operation, and cost-effectiveness. The key to adsorption lies in the adsorption material; traditional adsorption materials may be limited by poor adsorption performance and the problem of secondary pollution. Therefore, a recyclable adsorption material for Cd has been developed. 2+ Highly effective adsorption materials are essential. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a novel magnetic core-shell cadmium ion-imprinted polymer, its preparation method, and its applications. The novel magnetic core-shell cadmium ion-imprinted polymer provided by this invention has a high degree of magnetic permeability to Cd. 2+ It has a strong adsorption capacity and can selectively enrich Cd in water. 2+ It is also recyclable and reusable.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A novel magnetic core-shell type cadmium ion imprinted polymer, comprising Fe3O4 nanoparticles, tetraethyl orthosilicate (TEOS), vinyltrimethoxysilane (VTMOS), and template ions Cd. 2+ 2-phosphonobutane-1,2,4-tricarboxylic acid PBTCA, bisacrylamide MBA; wherein, the surface of the Fe3O4 nanoparticles is modified with TEOS and VTMOS, and Cd 2+ The polymer formed by PBTCA and MBA is loaded on the modified Fe3O4 surface.

[0007] Preferably, the Cd 2+ The molar ratio of PBTCA and MBA is (2-4):(0.5-1.5):(7-9).

[0008] This invention also provides a method for preparing the novel magnetic core-shell type cadmium ion imprinted polymer described in the above technical solution, comprising the following steps:

[0009] S1. Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS;

[0010] S2. Weigh out cadmium nitrate tetrahydrate and PBTCA according to the proportion, dissolve them in water and stir, add Fe3O4@SiO2@VTMOS obtained in S1, and continue stirring to obtain the first mixture;

[0011] S3. Under nitrogen protection, add MBA and initiator to the first mixture, heat and stir, and obtain a black jelly-like substance by magnetic separation;

[0012] S4. The black jelly-like substance obtained in S3 is washed sequentially with the first detergent, the second detergent, and the third detergent. After washing, it is dried under vacuum to obtain the novel magnetic core-shell type cadmium ion imprinted polymer Fe3O4@SiO2@IIP.

[0013] Preferably, the preparation method of Fe3O4@SiO2@VTMOS in S1 is as follows:

[0014] SS1. Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3 to 5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles.

[0015] SS2. Take 0.6g of Fe3O4 nanoparticles obtained in SS1, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia and 2mL LTEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2.

[0016] SS3. Take 0.2g of Fe3O4@SiO2 obtained from SS2 and disperse it in 150mL of anhydrous ethanol. Stir mechanically to disperse it evenly. During this process, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water. React at 30℃ for 8h. Wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain Fe3O4@SiO2@VTMOS.

[0017] Preferably, the amount of Fe3O4@SiO2@VTMOS added in S2 is 0.15g of Fe3O4@SiO2@VTMOS per 1mmol PBTCA.

[0018] Preferably, the water addition and dissolution in S2 is carried out at a ratio of 50 mL of deionized water per 1 mmol PBTCA, and the stirring is carried out at room temperature for 30 min, followed by stirring at room temperature for 12 h.

[0019] Preferably, the initiator in S3 is ammonium thiosulfate and sodium bisulfite in a mass ratio of 1:1, and the amount added is 0.1g of initiator per 1mmol PBTCA; the stirring after heating in S3 is to heat to 50°C and then stir for 5h.

[0020] Preferably, the washing process in S4, which involves sequentially washing with the first detergent, the second detergent, and the third detergent, consists of first washing with the first detergent 3 to 4 times, then washing with the second detergent until cadmium ions are undetectable, and finally washing with the third detergent until the solution is neutral.

[0021] Preferably, the first detergent is a mixture of methanol and water in a volume ratio of 1:1, the second detergent is a hydrochloric acid solution with a concentration of 2 mol / L, and the third detergent is deionized water.

[0022] The present invention also provides an application of the novel magnetic core-shell cadmium ion imprinted polymer described in the above technical solution in the selective adsorption and detection of cadmium ions in water.

[0023] Beneficial Technical Effects: This invention provides a novel magnetic core-shell cadmium ion-imprinted polymer. Using SiO2-coated nano-Fe3O4 as a carrier, PBTCA as a ligand, and MBA as a crosslinking agent, this novel magnetic core-shell cadmium ion-imprinted polymer was prepared using surface imprinting technology and chemical grafting. This polymer exhibits superior performance against Cd. 2+ The maximum adsorption capacity reaches 29.82 mg / g, and the adsorption process reaches basic equilibrium within 20 minutes. The entire adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model. This imprinted polymer exhibits good adsorption capacity for Cd. 2+ The adsorption of Cd is a spontaneous, endothermic, entropy-increasing process, and it occurs in the presence of Cd. 2+ Ni 2+ Co 2 + Zn 2+ In a mixed solution, for Cd 2+ The partition coefficient reached 643.3 mL / g, proving that it has selective adsorption of Cd. 2+ Ionic capacity. Attached Figure Description

[0024] Figure 1 A preparation route diagram for a novel magnetic core-shell cadmium ion-imprinted polymer;

[0025] Figure 2 Transmission electron microscopy (TEM) images of Fe3O4@SiO2@IIP and Fe3O4@SiO2; among them Figure 2 a is a transmission electron microscope (TEM) image of Fe3O4@SiO2. Figure 2 a1 is Figure 2 Transmission magnification image of a; Figure 2 b is a transmission electron microscope (TEM) image of Fe3O4@SiO2@IIP. Figure 2 b1 is Figure 2 Transmission magnification image of b;

[0026] Figure 3 The graphs show the magnetic response analysis of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@IIP. Curve (a) is the hysteresis regression curve of Fe3O4, curve (b) is the hysteresis regression curve of Fe3O4@SiO2, and the inset in the lower right corner shows the performance of Fe3O4@SiO2@IIP when a magnetic field is introduced.

[0027] Figure 4 The pH value of the system affects the adsorption of Cd by Fe3O4@SiO2@IIP. 2+ The effect of ions;

[0028] Figure 5 For Cd 2+ Effect of initial concentration on the adsorption capacity of Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP;

[0029] Figure 6 The effect of temperature on the adsorption properties of Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP;

[0030] Figure 7 The figure shows the effect of adsorption time on the adsorption of Cd2+ by Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP.

[0031] Figure 8 The selective adsorption diagrams are for Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP. Detailed Implementation

[0032] A novel magnetic core-shell type cadmium ion imprinted polymer, comprising Fe3O4 nanoparticles, tetraethyl orthosilicate (TEOS), vinyltrimethoxysilane (VTMOS), and template ions Cd. 2+2-phosphonobutane-1,2,4-tricarboxylic acid PBTCA, bisacrylamide MBA; wherein, the surface of the Fe3O4 nanoparticles is modified with TEOS and VTMOS, and Cd 2+ The polymer formed by PBTCA and MBA is loaded on the modified Fe3O4 surface.

[0033] In this invention, the Cd 2+ The preferred molar ratio of PBTCA and MBA is (2-4):(0.5-1.5):(7-9), more preferably 3:1:8. This invention uses SiO2-coated nano-Fe3O4 as a carrier and PBTCA as a functional monomer to prepare a novel magnetic core-shell cadmium ion-imprinted polymer using surface imprinting technology and chemical grafting. 2+ The maximum adsorption capacity reaches 29.82 mg / g, and the adsorption process reaches basic equilibrium within 20 minutes. The entire adsorption process conforms to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model. This imprinted polymer exhibits good adsorption capacity for Cd. 2+ The adsorption of Cd is a spontaneous, endothermic, entropy-increasing process, and it occurs in the presence of Cd. 2+ Ni 2+ Co 2+ Zn 2+ In a mixed solution, for Cd 2+ The partition coefficient reached 643.3 mL / g, proving that the imprinted polymer has selective adsorption capacity for Cd. 2+ Ionic capacity.

[0034] This invention also provides a method for preparing the novel magnetic core-shell type cadmium ion imprinted polymer described in the above technical solution, comprising the following steps:

[0035] S1. Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS;

[0036] S2. Weigh out cadmium nitrate tetrahydrate and PBTCA according to the proportion, dissolve them in water and stir, add Fe3O4@SiO2@VTMOS obtained in S1, and continue stirring to obtain the first mixture;

[0037] S3. Under nitrogen protection, add MBA and initiator to the first mixture, heat and stir, and obtain a black jelly-like substance by magnetic separation;

[0038] S4. The black jelly-like substance obtained in S3 is washed sequentially with the first detergent, the second detergent, and the third detergent. After washing, it is dried under vacuum to obtain the novel magnetic core-shell type cadmium ion imprinted polymer Fe3O4@SiO2@IIP.

[0039] In this invention, the preparation route of the novel magnetic core-shell cadmium ion-imprinted polymer is as follows: Figure 1 As shown.

[0040] This invention prepares a vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS.

[0041] In this invention, the preparation method of Fe3O4@SiO2@VTMOS is as follows:

[0042] SS1. Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3 to 5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles.

[0043] SS2. Take 0.6g of Fe3O4 nanoparticles obtained in SS1, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia and 2mL LTEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2.

[0044] SS3. Take 0.2g of Fe3O4@SiO2 obtained from SS2 and disperse it in 150mL of anhydrous ethanol. Stir mechanically to disperse it evenly. During this process, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water. React at 30℃ for 8h. Wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain Fe3O4@SiO2@VTMOS.

[0045] In this invention, cadmium nitrate tetrahydrate and PBTCA are weighed in proportion, dissolved in water and stirred, and Fe3O4@SiO2@VTMOS obtained in S1 is added. Stirring is continued to obtain the first mixture.

[0046] In this invention, the amount of Fe3O4@SiO2@VTMOS added is 0.15g of Fe3O4@SiO2@VTMOS per 1mmol PBTCA; the water dissolution is carried out by adding 50mL of deionized water per 1mmol PBTCA, the stirring is carried out at room temperature for 30min, and the stirring is continued at room temperature for 12h.

[0047] In this invention, under nitrogen protection, MBA and an initiator are added to a first mixture, the mixture is heated and stirred, and magnetic separation is performed to obtain a black jelly-like substance.

[0048] In this invention, the initiator is ammonium thiosulfate and sodium bisulfite in a mass ratio of 1:1, and the amount added is 0.1g of initiator per 1mmol PBTCA; the stirring after heating in S3 is to heat to 50°C and then stir for 5h.

[0049] The present invention washes the black jelly-like substance obtained in the above technical solution with a first detergent, a second detergent, and a third detergent in sequence. After washing, it is vacuum dried to obtain a novel magnetic core-shell type cadmium ion imprinted polymer Fe3O4@SiO2@IIP.

[0050] In this invention, the sequential washing with a first detergent, a second detergent, and a third detergent involves washing 3 to 4 times with the first detergent, then washing with the second detergent until cadmium ions are undetectable, and finally washing with the third detergent until neutral. The first detergent is a 1:1 volume ratio of methanol and water, the second detergent is a 2 mol / L hydrochloric acid solution, and the third detergent is deionized water. This invention uses the first detergent to remove residual self-polymers from Fe3O4@SiO2@IIP, the second detergent to remove cadmium ions from Fe3O4@SiO2@IIP, and the third detergent to adjust the pH of Fe3O4@SiO2@IIP to neutral. Through these three washing processes, relatively pure Fe3O4@SiO2@IIP can be obtained.

[0051] The present invention also provides an application of the novel magnetic core-shell cadmium ion imprinted polymer described in the above technical solution in the selective adsorption and detection of cadmium ions in water.

[0052] In this invention, there is no particular limitation on the type of application; any application of the novel magnetic core-shell cadmium ion imprinted polymer that is acceptable in this field is acceptable. The composition, properties, and beneficial effects of the novel magnetic core-shell cadmium ion imprinted polymer are the same as described above and will not be repeated here.

[0053] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments. Unless otherwise specified, the materials, reagents, etc., used in the embodiments and experimental examples of the present invention can be obtained commercially; unless otherwise specified, the methods used in the embodiments and experimental examples of the present invention are conventional methods.

[0054] Reagents and Instruments

[0055] FeCl3·6H2O, ethylene glycol, sodium acetate, polyethylene glycol, ethanol, ammonia, tetraethyl silicate (TEOS), vinyltrimethoxysilane (VTMOS), Cd(NO3)2·4H2O, 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA), and methanol, analytical grade, were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0056] N,N'-methylenebisacrylamide (MBA), analytical grade, purchased from Sigma-Aldrich (Milwaukee, USA); ammonium persulfate (APS) and sodium bisulfite, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0057] The following products are listed: SK series benchtop ultrasonic cleaners (Shanghai Kedao Ultrasonic Instrument Co., Ltd.); water bath constant temperature incubator shakers (Shanghai Zhicheng Analytical Instrument Co., Ltd.); Cary 6400 Fourier Transmission Infrared Spectrometer (FTIR) (Agilent Technologies, USA); Icap-6300 ICP-OES Spectrometer (Thermo Scientific, USA); JEOLJEM-2100 Transmission Electron Microscope (TEM) (Hitachi, Japan); TG / DTA6300 Thermogravimetric-Differential Thermal Analyzer (Seiko Kagaku, Japan); MPMSXL Vibrating Sample Magnetometer (VSM) (Quantum Design, USA); Escalab 250Xi X-ray Photoelectron Spectrometer (XPS) (Thermo Scientific, USA).

[0058] Example 1

[0059] (1) Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS:

[0060] ① Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3-5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles.

[0061] ② Take 0.6g of Fe3O4 nanoparticles obtained in step ①, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia and 2mL LTEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2;

[0062] ③ Take 0.2g of Fe3O4@SiO2 obtained in step ②, disperse it in 150mL of anhydrous ethanol, and stir mechanically to disperse it evenly. During this period, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water in sequence. React at 30℃ for 8h, then wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain vinyltrimethoxysilane VTMOS, which is Fe3O4@SiO2@VTMOS;

[0063] (2) Add 3 mmol Cd(NO3)2·4H2O and 1 mmol functional monomer PBTCA to a three-necked round-bottom flask containing 50 mL deionized water, stir at room temperature for 30 min, then add 0.15 g of Fe3O4@SiO2@VTMOS obtained in (1), and stir for 12 h;

[0064] (3) Under nitrogen protection, add 8 mmol of crosslinking agent MBA and 0.1 g of initiator ((NH4)2S2O8:NaHSO3=1:1) to the above mixture, then heat to 50℃ and continue stirring for 5 h, and obtain a black jelly-like substance by magnetic separation;

[0065] (4) For the black jelly-like substance, first wash it three times with a mixed solution of methanol and water (volume ratio of 1:1), then wash it with 2 mol / L HCl solution until Cd is undetectable. 2+ Finally, the sample was washed with deionized water until nearly neutral, and then dried under vacuum to obtain magnetic core-shell Cd. 2+ Imprinted polymer Fe3O4@SiO2@IIP.

[0066] Example 2

[0067] (1) Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS:

[0068] ① Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3-5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles.

[0069] ② Take 0.6g of Fe3O4 nanoparticles obtained in step ①, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia and 2mL LTEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2;

[0070] ③ Take 0.2g of Fe3O4@SiO2 obtained in step ②, disperse it in 150mL of anhydrous ethanol, and stir mechanically to disperse it evenly. During this period, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water in sequence. React at 30℃ for 8h, then wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain vinyltrimethoxysilane VTMOS, which is Fe3O4@SiO2@VTMOS;

[0071] (2) Add 2 mmol Cd(NO3)2·4H2O and 0.5 mmol functional monomer PBTCA to a three-necked round-bottom flask containing 50 mL deionized water, stir at room temperature for 30 min, then add 0.15 g of Fe3O4@SiO2@VTMOS obtained in (1), and stir for 12 h;

[0072] (3) Under nitrogen protection, 7 mmol of crosslinking agent MBA and 0.05 g of initiator ((NH4)2S2O8:NaHSO3=1:1) were added to the above mixture, and the temperature was raised to 50℃ and stirred for 5 h. A black jelly-like substance was obtained by magnetic separation.

[0073] (4) For the black jelly-like substance, first wash it three times with a mixed solution of methanol and water (volume ratio of 1:1), then wash it with 2 mol / L HCl solution until Cd is undetectable. 2+ Finally, the sample was washed with deionized water until nearly neutral, and then dried under vacuum to obtain magnetic core-shell Cd. 2+ Imprinted polymer Fe3O4@SiO2@IIP.

[0074] Example 3

[0075] (1) Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS:

[0076] ① Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3-5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles.

[0077] ② Take 0.6g of Fe3O4 nanoparticles obtained in step ①, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia and 2mL LTEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2;

[0078] ③ Take 0.2g of Fe3O4@SiO2 obtained in step ②, disperse it in 150mL of anhydrous ethanol, and stir mechanically to disperse it evenly. During this period, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water in sequence. React at 30℃ for 8h, then wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain vinyltrimethoxysilane VTMOS, which is Fe3O4@SiO2@VTMOS;

[0079] (2) Add 4 mmol Cd(NO3)2·4H2O and 1.5 mmol functional monomer PBTCA to a three-necked round-bottom flask containing 50 mL deionized water, stir at room temperature for 30 min, then add 0.15 g of Fe3O4@SiO2@VTMOS obtained in (1), and stir for 12 h;

[0080] (3) Under nitrogen protection, add 9 mmol of crosslinking agent MBA and 0.15 g of initiator ((NH4)2S2O8:NaHSO3=1:1) to the above mixture, then heat to 50℃ and continue stirring for 5 h, and obtain a black jelly-like substance by magnetic separation;

[0081] (4) For the black jelly-like substance, first wash it three times with a mixed solution of methanol and water (volume ratio of 1:1), then wash it with 2 mol / L HCl solution until Cd is undetectable. 2+ Finally, the sample was washed with deionized water until nearly neutral, and then dried under vacuum to obtain magnetic core-shell Cd. 2+ Imprinted polymer Fe3O4@SiO2@IIP.

[0082] Comparative Example 1

[0083] The difference between this comparative example and Example 1 is that cadmium nitrate tetrahydrate is not added during the preparation process. The other raw materials and operations are the same as in Example 1. The resulting product is denoted as Fe3O4@SiO2@NIP.

[0084] Sample Characterization in Experiment Example 1

[0085] (1) Transmission electron microscopy analysis

[0086] Transmission electron microscopy (TEM) analysis was performed on the Fe3O4@SiO2@IIP and Fe3O4@SiO2 obtained in Examples 1-3. The TEM analysis results are as follows: Figure 2 As shown. By Figure 2 It can be seen that after sequentially coating with SiO2 and PBTCA imprinted layers, the spherical structure is still maintained, the dispersion is good, and no clustering phenomenon is observed. In addition, the core in the dark area represents Fe3O4 nanoparticles, the inner layer with medium contrast is a silica shell, and the outer layer with light contrast is the PBTCA imprinted layer. Figure 2 (a1) confirms that Fe3O4 nanoparticles were successfully modified through a silica layer, with a particle size of approximately 519.1 nm. Figure 2 (b1) The thickness of the magnetic carrier coating layer is significantly increased, with a particle size of approximately 783.7 nm. In summary, the preparation of Fe3O4@SiO2@IIP was successful.

[0087] (2) Magnetic response analysis

[0088] Magnetic response analysis was performed on Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@IIP. The results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the hysteresis regression curves of the three materials have similar shapes and all pass through the origin, indicating that all four possess superparamagnetism and strong magnetic response under magnetic field, facilitating particle aggregation. The saturation magnetization of Fe3O4 at room temperature is 66.79 emu / g, while that of Fe3O4@SiO2 decreases to 63.89 emu / g. This decrease in saturation magnetization may be due to the SiO2 coating on the surface of the Fe3O4 nanoparticles, which partially shields the magnetism, but the effect is minor, and the overall magnetism remains strong. The saturation magnetization of Fe3O4@SiO2@IIP is much lower than that of Fe3O4, at 15.02 emu / g. This may be due to the shielding effect of the polymer shell on the Fe3O4 surface, leading to a decrease in the saturation magnetization of Fe3O4@SiO2@IIP. However, when a magnetic field is introduced, Fe3O4@SiO2@IIP can be easily and rapidly separated from the aqueous solution within approximately 25 seconds. Figure 3 (Illustration in the image) These observations confirm that the obtained Fe3O4@SiO2@IIP has excellent magnetic properties and can be used for rapid magnetic separation.

[0089] Experiment Example 2 Adsorption Experiment

[0090] The products obtained in Examples 1-3 and Comparative Example 1 were subjected to Cd treatment under different conditions using a water bath shaking method. 2+ The adsorption capacity was studied, and the Cd concentration in the solution after adsorption was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ The concentration of Cd was determined, and the results were analyzed to explore the influencing factors of the adsorption experiment. During the experiment, HCl and NaOH were used to adjust the pH of the system. The initial concentration (25 mg / L to 180 mg / L) of Cd was determined in 20 mL of the solution. 2+ Static adsorption experiments were conducted by adding 10 mg of adsorbents Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP to the solution. The mixture was shaken for a certain period of time (4 min to 34 min) at a certain temperature (25℃~45℃) until adsorption reached equilibrium. The adsorption was then collected, and the remaining Cd in the solution was detected by ICP-OES. 2+ concentration.

[0091] Data analysis and adsorption theory: The static adsorption capacity is calculated using the following formula:

[0092]

[0093] In the formula: q (mg / g) is the adsorption capacity; C i(mg / L) is the initial concentration of the solution; C f (mg / L) is the final concentration of the solution; V (mL) is the volume of the solution; W (g) is the mass of the adsorbent.

[0094] Results and Analysis

[0095] (1) pH effect

[0096] The effect of pH value on the adsorption of cadmium ions by Fe3O4@SiO2@IIP is as follows: Figure 7 As shown. Figure 4 As shown, the adsorption capacity of the adsorbent for Cd(II) gradually increases with increasing pH, reaching 13.88 mg / g at pH 6.0. This may be because at lower pH conditions, the adsorbent surface groups are highly protonated, exhibiting the form of -COOH, which severely repels Cd(II) in the solution. With increasing pH, the protonation degree on the adsorbent surface gradually decreases, thereby enhancing its chelation ability with Cd(II). Furthermore, the Cd in the system... 2+ Some of it has also hydrolyzed into Cd(OH)₂. + This reduces the repulsive force between them, making Cd(OH)₂ more reactive. + It is easier to bind with carboxyl and phosphate groups on the surface of the adsorbent.

[0097] (2) Effect of initial concentration

[0098] To investigate the effect of initial concentration on the adsorption capacity of Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP, Cd3O4@SiO2@NIP solutions with concentrations ranging from 25 mg / L to 205 mg / L were prepared. 2+ The solution was used for the experiment. The study was conducted at 25°C and pH 6.0.

[0099] The effect of initial concentration on the adsorption capacity of Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP is as follows: Figure 5 As shown. By Figure 5 It can be seen that in Cd 2+ At low ion concentrations, the adsorption capacity of the adsorbent is low; however, as the initial concentration increases, the mass transfer driving force increases, leading to a greater adsorption capacity. The maximum adsorption capacities of Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP are 29.82 mg / g and 26.09 mg / g, respectively. The adsorption capacity of Fe3O4@SiO2@IIP is greater than that of Fe3O4@SiO2@NIP, indicating that imprinting technology enhances the adsorption capacity of the adsorbent. This may be because the introduction of template ions generates more imprinted sites, resulting in a greater adsorption capacity for Fe3O4@SiO2@IIP than Fe3O4@SiO2@NIP.

[0100] (3) Temperature effect

[0101] The discussion focused on the conditions when the solution pH was 6.0 and the initial Cd was... 2+ The effect of temperature on the adsorption performance of the material at a concentration of 50 mg / L and a temperature range of 25℃ to 45℃.

[0102] Figure 6 The effect of temperature on the adsorption capacity is shown in the curve. The results indicate that the adsorption capacity increases slightly with increasing temperature, suggesting that higher temperatures are beneficial to the adsorption process. This may be because higher temperatures alter the pore size of the adsorbent, allowing more Cd to be adsorbed. 2+ Ions diffuse into the adsorbent. On the other hand, higher temperatures are more conducive to the diffusion of Cd. 2+ Rapid diffusion within the system also facilitates rapid binding with functional groups on the surface of the adsorbent.

[0103] (4) Time impact

[0104] The effect of adsorption time on the adsorption of Cd by the adsorbent was investigated. 2+ The effect of Cd. The experiment was conducted at a system temperature of 25℃, a solution pH of 6, and a concentration of Cd. 2+ The experiment was conducted at an initial concentration of 50 mg / L. Figure 7 As shown, with the extension of contact time, the adsorption capacity exhibits a relationship of first increasing and then tending towards equilibrium, reaching a basic equilibrium within 20 minutes. This may be because a large number of imprinted sites exist on the adsorbent surface in the early stage of the adsorption process; as the adsorption process proceeds, these imprinted sites are gradually replaced by Cd. 2+ The presence of Cd occupies these sites, causing the adsorption process to become increasingly slower. When all imprinted sites are occupied by Cd... 2+ When fully occupied, adsorption reaches equilibrium, and the adsorption capacity does not change significantly. Furthermore, the adsorption capacity of Fe3O4@SiO2@IIP is higher than that of Fe3O4@SiO2@NIP, at 18.21 mg / g and 11.94 mg / g respectively. This is because, due to the introduction of template ions, Fe3O4@SiO2@IIP has a size similar to that of the template Cd compared to Fe3O4@SiO2@NIP. 2+ Matching imprinted cavities. This demonstrates that imprinting technology can enhance the adsorption capacity of polymers.

[0105] (5) Selective adsorption

[0106] Prepare 20 mL of 5 mg·L⁻¹ solution at pH = 6 and temperature = 25℃. -1 Cd 2+ Zn 2+ Ni 2+ and Co2+ Add 10 mg of adsorbent to the mixed solution and shake in a water bath. For example... Figure 8 As shown, in the mixed solution, Fe3O4@SiO2@IIP and Fe3O4@SiO2@NIP affect the Cd content in the mixed solution. 2+ The adsorption capacities were 3.02 mg / g and 0.98 mg / g, respectively. Compared with the corresponding non-imprinted polymer, the imprinted polymer exhibited higher cadmium ion selectivity in the mixed solution. This is because the Fe3O4@SiO2@IIP contains cadmium ions that interact with Cd. 2+ Imprint cavities that correspond to the three-dimensional structure also exist with Cd 2+ Functional groups capable of chelation, but none formed with Cd in Fe3O4@SiO2@NIP. 2+ The complementary binding sites result in relatively low adsorption capacity for the substrates.

[0107] In summary, this invention uses Cd 2+ Using Fe3O4 as a template, PBTCA as a functional monomer, a novel magnetic core-shell type cadmium ion surface-imprinted polymer was prepared by surface imprinting technology and chemical grafting, and applied to Cd in aqueous solution. 2+ The removal of Cd was observed. The main conclusions are as follows: carboxyl and phosphonic acid groups can be introduced into the Fe3O4@SiO2 surface via chemical grafting; the pH value in the system has a significant impact on Cd. 2+ The adsorption of Fe3O4@SiO2@IIP plays an important role; as the pH value increases, the adsorption of Fe3O4@SiO2@IIP on Cd... 2+ The adsorption capacity also increased accordingly, reaching a maximum adsorption capacity (13.88 mg / g) at pH = 6.0; Fe3O4@SiO2@IIP for Cd 2+ The kinetic adsorption process can be described by pseudo-second-order kinetics, which is a chemisorption process. The adsorption isotherm data conform to the Langmuir model, and the adsorption process can be considered as monolayer adsorption. Adsorption thermodynamic studies show that the imprinted polymer adsorbs Cd... 2+ The adsorption of Cd is a spontaneous, endothermic, entropy-increasing process. Imprinted polymers exhibit better selectivity than non-imprinted polymers in Cd. 2+ Ni 2+ Co 2+ Zn 2+ In a mixed solution, for Cd 2+ The partition coefficient reached 643.3 mL / g, proving that the imprinted polymer has selective adsorption capacity for Cd. 2+ Ionic capacity.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A magnetic core-shell type cadmium ion-imprinted polymer, characterized by, The imprinted polymer comprises Fe3O4 nanoparticles, tetraethyl orthosilicate (TEOS), vinyltrimethoxysilane (VTMOS), and template ions (Cd). 2+ 2-phosphonobutane-1,2,4-tricarboxylic acid PBTCA, bisacrylamide MBA; wherein, the surface of the Fe3O4 nanoparticles is modified with TEOS and VTMOS, and Cd 2+ The polymer formed by PBTCA and MBA is loaded on the modified Fe3O4 surface.

2. The magnetic core-shell type cadmium ion-imprinted polymer according to claim 1, characterized by, The Cd 2+ The molar ratio of PBTCA, MBA is (2~4):(0.5~1.5):(7~9).

3. A method for preparing the magnetic core-shell type cadmium ion-imprinted polymer according to claim 1 or 2, characterized by, Includes the following steps: S1. Preparation of vinyl-modified magnetic matrix material Fe3O4@SiO2@VTMOS; S2. Weigh out cadmium nitrate tetrahydrate and PBTCA according to the proportion, dissolve them in water and stir, add Fe3O4@SiO2@VTMOS obtained in S1, and continue stirring to obtain the first mixture; S3. Under nitrogen protection, add MBA and initiator to the first mixture, heat and stir, and obtain a black jelly-like substance by magnetic separation; S4. Wash the black jelly-like substance obtained in S3 with the first detergent, the second detergent, and the third detergent in sequence. After washing, vacuum dry to obtain the magnetic core-shell type cadmium ion imprinted polymer Fe3O4@SiO2@IIP.

4. The production method according to claim 3, characterized by, The preparation method of Fe3O4@SiO2@VTMOS in S1 is as follows: SS1. Mix 60 mL of ethylene glycol, 0.75 g of polyethylene glycol-2000, 0.01 mol of ferric chloride hexahydrate and 0.03 mol of sodium acetate evenly, react at 200 °C for 6 h, wash with methanol 3 to 5 times, collect with a magnet, and vacuum dry at 60 °C for 6 h to obtain Fe3O4 nanoparticles. SS2. Take 0.6g of Fe3O4 nanoparticles obtained in SS1, disperse them in a mixture of 120mL isopropanol and 90mL deionized water, add 11mL of 28wt% ammonia water and 2mL TEOS, stir mechanically for 12h, wash with deionized water and ethanol successively until neutral, and vacuum dry at 40℃ for 24h to obtain SiO2-coated Fe3O4 nanoparticles Fe3O4@SiO2; SS3. Take 0.2g of Fe3O4@SiO2 obtained from SS2 and disperse it in 150mL of anhydrous ethanol. Stir mechanically to disperse it evenly. During this process, slowly add 1mL of VTMOS and 10mL of 28wt% ammonia water. React at 30℃ for 8h. Wash with methanol 3 times, incubate with 1mol / L HCl for 12h, and vacuum dry at 40℃ for 24h to obtain Fe3O4@SiO2@VTMOS.

5. The preparation method according to claim 3, characterized in that, The amount of Fe3O4@SiO2@VTMOS added in S2 is 0.15g of Fe3O4@SiO2@VTMOS per 1mmol PBTCA.

6. The preparation method according to claim 3, characterized in that, The dissolution in S2 is carried out by adding 50 mL of deionized water to every 1 mmol PBTCA, and stirring is carried out at room temperature for 30 min, followed by stirring at room temperature for 12 h.

7. The preparation method according to claim 3, characterized in that, The initiator in S3 is ammonium thiosulfate and sodium bisulfite in a mass ratio of 1:1, and the amount added is 0.1g of initiator per 1mmol PBTCA; the stirring after heating in S3 is to heat to 50°C and then stir for 5h.

8. The preparation method according to claim 3, characterized in that, The washing process in S4, which involves sequentially washing with the first detergent, the second detergent, and the third detergent, consists of first washing with the first detergent 3 to 4 times, then washing with the second detergent until cadmium ions are undetectable, and finally washing with the third detergent until the solution is neutral.

9. The production method according to claim 3 or 8, characterized by, The first detergent is a mixture of methanol and water in a volume ratio of 1:1, the second detergent is a hydrochloric acid solution with a concentration of 2 mol / L, and the third detergent is deionized water.

10. The use of the magnetic core-shell type cadmium ion imprinted polymer of claim 1 or 2 in the selective adsorption and detection of cadmium ions in water bodies.

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