Preparation Method and Application of Gold Ion-Imprinted Yolk-Shell Magnetic Nanorobots

Abstract

The present invention belongs to the technical field of the preparation of adsorption separation functional materials, and discloses a preparation method and application of gold ion-imprinted Yolk-Shell magnetic nanorobots, which solves the problems of slow mass transfer rate and poor selectivity of existing magnetic functional materials. The method includes: under an alkaline environment, assembling magnetite nanoparticles into a rod-like structure by means of magnetic field-assisted sol-gel method, and modifying double bonds on its surface by using a silane coupling agent; using Au<supgt;3+< / supgt; as a template ion, vinylimidazole as a functional monomer, and ethylene glycol dimethacrylate as a crosslinking agent, constructing an imprinted layer by means of surface ion imprinting technology; after eluting Au<supgt;3+< / supgt> with an acidic thiourea solution, etching the silicon layer with a hydrofluoric acid solution to obtain imprinted Yolk-Shell magnetic nanorobots. The imprinted Yolk-Shell magnetic nanorobots prepared by the present invention have extremely fast adsorption kinetics and specific recognition ability, and have good adsorption and regeneration performance and are easy to recycle. In addition, the catalytic and dye degradation performance of the adsorbed material is excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of adsorption separation functional materials, and provides a preparation method and application of gold ion-imprinted Yolk-Shell magnetic nanorobots. Background Art

[0002] With the progress of technology and the improvement of people's living standards, the replacement speed of electronic products such as mobile phones and computers is accelerating continuously, resulting in a sharp increase in the number of waste electronic products. Statistics show that: in 2030, the amount of electronic waste in China will reach 27.22 million tons, and the total value of recyclable metals will reach 160 billion yuan. If the recovery rate reaches 85%, it will save about 30 billion kWh of energy compared with mining primary ores and reduce nearly 22 million tons of carbon emissions. In addition, research shows that: 1 ton of waste mobile phones contains 347 grams of gold, and the gold content in 40 mobile phones is equivalent to that of mining 1 ton of ore. Thus, it can be seen that electronic waste is a "gold mine" yet to be exploited. Therefore, the recovery of gold from electronic waste not only has significant economic benefits but also has a profound and far-reaching significance for sustainable development.

[0003] At present, hydrometallurgical technologies for gradually separating and recovering precious metals from leaching solutions include precipitation, solvent extraction, electrolysis, and adsorption. Adsorption is considered a promising adsorption method due to its advantages such as simple operation, high cost-effectiveness, environmental friendliness, and strong recovery ability. However, electronic waste has complex components and many element types, with more than 20 kinds of metals, and the gold content is less than 0.1%. There are huge challenges in the selective extraction of gold. Ion-imprinted polymers (IIPs) use ions as templates and self-assemble with functional monomers through electrostatic interactions, metal coordination bonds, and chelation to prepare adsorbents with specific imprinted cavities, which are three-dimensional cavity structures of "ionic keys" with both specific recognition and selective adsorption, and have advantages such as good selectivity, large adsorption capacity, high stability, and long repeated service life, and have attracted much attention in the recovery and separation of metals.

[0004] Artificial micro-nanorobots (micro-nanomotors) are intelligent power devices at the micro-nano scale, which can convert external environmental energy into the kinetic energy of their own movement, and have broad application prospects in the fields of targeted drug delivery, precision medicine, biosensing, and environmental remediation by virtue of their advantages such as controllability and modifiability. At present, various types of powered micro-nanorobots have been proposed, such as chemically fuel-driven, enzyme-driven, light-driven, electric field-driven, ultrasonic-driven, and magnetic-driven, etc. Among them, magnetically driven nanorobots have the characteristics of easy recovery, fast response speed, high precision, long-lasting movement, remote control, non-toxic and harmless, and high economic benefits, and are good adsorbent substrate materials.

[0005] Fast mixing is crucial for achieving effective chemical reactions. Since passive diffusion is slow and unreliable, physical stirring or shaking is usually required to ensure complete reaction. For example, mechanical stirrers or magnetic stirrers are used. Inspired by magnetotactic bacteria, magnetic rod-shaped structure materials have been widely used in aspects such as optics, catalysis, and biosensing, but their self-mixing function is often overlooked. Therefore, we designed and prepared magnetic rod-shaped structure robots to accelerate the mixing process and improve the mass transfer efficiency during the adsorption process by self-stirring in an external magnetic field. At the same time, their excellent magnetism can avoid time-consuming and laborious separation processes such as centrifugation and precipitation, effectively solving the problem that adsorbents are difficult to recycle.

[0006] When recovering gold from electronic waste leachate, there are a large number of other interfering ions such as Ni(II), Co(II), Na(I), Zn(II), Pb(II), Cu(II), and Fe(III). Therefore, adopting appropriate technologies and selecting functional monomers with excellent selectivity are the keys to solving the current problem of low purity of recovered gold. Summary of the Invention

[0007] To solve the problems in the prior art such as the difficulty in collecting gold ion adsorbents, slow adsorption rate, and poor selectivity, the present invention proposes a preparation method of gold ion-imprinted Yolk-Shell structured magnetic nanorobots (MNR-IIP-YS) and uses it for highly selective enrichment of gold from electronic waste leachate.

[0008] The present invention first synthesizes magnetite nanoparticles with a particle size of about 150 nm by a hydrothermal method. Subsequently, magnetic nanorobots are constructed by a magnetic field-assisted sol-gel method. After grafting double bonds with a silane coupling agent, an imprinted layer is constructed on the surface of the nanorobots using ion imprinting technology. After washing away the template, the middle silicon layer is etched with an HF solution to obtain a gold ion-imprinted Yolk-Shell magnetic nanorobot adsorbent, and its gold adsorption performance is explored. At the same time, a series of studies are carried out on the catalytic performance and dye degradation of the material after adsorbing gold.

[0009] To achieve the above technical purposes, the technical solution adopted by the present invention is:

[0010] A preparation method of gold ion-imprinted Yolk-Shell magnetic nanorobots, comprising the following steps:

[0011] (1) Preparation of magnetite nanoparticles (Fe 3 O 4 NPs)

[0012] A certain amount of ferric chloride hexahydrate (FeCl 3 ·6H 2(O) Disperse in an appropriate amount of ethylene glycol. Subsequently, add a certain amount of sodium citrate dihydrate (Na 3 Cit·2H 2 O) and anhydrous sodium acetate (NaAc). After mixing evenly, perform ultrasonic treatment until there is no obvious precipitate in the mixed solution. Transfer the mixture to a hydrothermal reaction kettle and react at a certain temperature T 1 for a certain time t 1 . After cooling to room temperature, collect by centrifugation, wash several times with deionized water and ethanol, and dry in vacuum for later use.

[0013] (2) Preparation of vinyl-functionalized magnetic nanorobots (MNR-MPS)

[0014] 2.1) Add a certain amount of the Fe 3 O 4 NPs prepared in step (1) into an appropriate amount of anhydrous ethanol and disperse by ultrasonic treatment. Subsequently, place it in a water bath at a certain temperature T 2 , add an appropriate amount of ammonia water, and mechanically stir at a certain rotation speed for a certain time t 2 . Then reduce the rotation speed, add a certain amount of tetraethyl orthosilicate (TEOS) and react for a period of time t 3 . Place it directly above a bar magnet with a certain magnetic field strength for a period of time t 4 and then slowly place it on a stable place and let it stand for a period of time t 5 . Separate the product by magnet, wash several times with deionized water and ethanol to obtain magnetic nanorobots (MNR), dry in vacuum for later use.

[0015] 2.2) Ultrasonically disperse an appropriate amount of the MNR prepared in step 1) in a certain amount of anhydrous ethanol and deionized water, and sequentially add an appropriate amount of ammonia water and 3-(methacryloyloxy)propyltrimethoxysilane (MPS) under stirring at a certain temperature (T 3 ). React for a period of time t 6 . Separate the product by magnet, wash several times with deionized water and ethanol to obtain vinyl-functionalized magnetic nanorobots (MNR-MPS), dry in vacuum for later use.

[0016] (3) Preparation of gold ion-imprinted yolk-shell magnetic nanorobots (MNR-IIP-YS)

[0017] 3.1) Mix a certain amount of HAuCl 4 , vinylimidazole, deionized water, and methanol, and then place it in a magnetic stirrer at a certain temperature (T 4 ) and pre-polymerize for a certain period of time (t 7 ). Then add a certain amount of MNR-MPS, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and at a certain temperature (T 5) Polymerize and crosslink for a period of time (t 8 ), collect the product with a magnet, wash it several times with deionized water and ethanol to remove residual reagents, then soak it in an acidic thiourea solution for a period of time (t 9 ) to remove the template on the imprinted polymer, and finally rinse it repeatedly with deionized water and ethanol. The obtained imprinted magnetic nanorobot (MNR-IIP) is dried in vacuo for later use.

[0018] The preparation process of the non-imprinted material (MNR-NIP) is the same, except that the template HAuCl 4 is not added.

[0019] 3.2) Add the two solids obtained in step 1) to a hydrofluoric acid solution of a certain concentration respectively, shake for a period of time (t 10 ), collect the product with a magnet, and wash it several times with deionized water and ethanol to remove residual reagents. The obtained gold ion-imprinted crosslinked Yolk-Shell magnetic nanorobot (MNR-IIP-YS) and non-imprinted Yolk-Shell magnetic nanorobot (MNR-NIP-YS) are dried in vacuo for later use.

[0020] Preferably, in step (1), the dosage ratio of FeCl 3 ·6H 2 O, ethylene glycol, Na 3 Cit·2H 2 O and NaAc is 1.6 - 3.2 g : 50 - 100 mL : 0.6 - 1.2 g : 2.8 - 6.0 g, the reaction temperature T 1 is 180 - 220 °C, and the reaction time t 1 is 9 - 12 h.

[0021] Preferably, in 2.1) of step (2), the amount of the certain amount of magnetite nanoparticles is 25 - 75 mg, the amount of appropriate anhydrous ethanol is 30 - 60 mL, the reaction temperature T 2 is 25 - 35 °C, the dosage of ammonia water is 1.7 - 3.3 mL, the initial mechanical stirring speed is 600 - 800 rpm, the reaction time t 2 is 15 - 25 min, the adjusted speed is 200 - 400 rpm, the dosage of TEOS is 0.15 - 0.3 mL, the reaction time t 3 is 10 - 20 min, the central magnetic field strength of the bar magnet is about 7.8 mT, the placement time t 4 is 80 - 120 s, and the reaction time t 5 is 10 - 15 h.

[0022] Preferably, in 2.2) of step (2), the dosage ratio of MNR, MPS, ammonia water, absolute ethanol and deionized water is 100 mg: 0.2 - 0.3 mL: 1.5 mL: 40 mL: 10 mL, the reaction temperature is 60 - 80 °C, the stirring speed is 600 - 800 rpm, and the reaction time t 6 is 20 - 26 h.

[0023] Preferably, in 3.1) of step (3), the dosage ratio of MNR-MPS, HAuCl 4 , vinyl imidazole, ethylene glycol dimethacrylate, azobisisobutyronitrile, deionized water and methanol is 50 mg: 0.2 - 0.8 mmol: 0.8 mmol: 0.74 mL: 10 mg: 5 mL: 15 mL.

[0024] The pre-polymerization temperature T 4 is 25 - 30 °C, and the pre-polymerization time t 7 is 30 - 60 min;

[0025] The polymerization cross-linking temperature T 5 is 70 - 80 °C, and the polymerization time t 8 is 12 - 15 h.

[0026] The concentration of the acidic thiourea solution is 1 mol / L, the pH is 1, and the elution time t 9 is 4 - 6 h.

[0027] Preferably, in 3.2) of step (3), the concentration of the hydrofluoric acid solution is 20 mmol / L, and the etching reaction time t 10 is 5 - 45 min.

[0028] Use of the gold ion-imprinted Yolk-Shell magnetic nanorobot prepared by the present invention for adsorbing gold in the leaching solution of electronic waste.

[0029] A magnetic nanorobot MNR-IIP-YS-Au after capturing gold is prepared by capturing gold with a gold ion-imprinted cross-linked Yolk-Shell structured magnetic nanorobot MNR-IIP-YS.

[0030] Use of the magnetic nanorobot MNR-IIP-YS-Au after capturing gold for catalytic degradation of dyes.

[0031] Compared with the prior art, the beneficial effects of the present invention are embodied in the following aspects:

[0032] Based on magnetic induction assembly, ion imprinting and chemical etching, the present invention prepares a gold ion-imprinted adsorbent with high selectivity and fast adsorption kinetics.

[0033] (1) The ion imprinting technology overcomes the problem of poor selectivity of traditional adsorbents;

[0034] (2) The Yolk-Shell structure realizes the synergistic improvement of the mass transfer rate and the site density, and the adsorption capacity is increased by 51.16% compared with that before etching;

[0035] (3) MNR-IIP-YS can be rapidly separated from the solution only by a magnetic field. In addition, the rod-like structure has magnetic anisotropy and can self-stir in a rotating magnetic field to achieve rapid enrichment of gold ions. 90.70% of the maximum adsorption capacity can be reached within 5 min, and the adsorption equilibrium can be reached within 30 min.

[0036] (4) The adsorption performance of MNR-IIP-YS does not show obvious decline after five cycles.

[0037] (5) The material after adsorbing gold exhibits excellent catalytic and dye degradation performance, and the reaction rate constants for 4-nitrophenol, methylene blue, and methyl orange are 0.20 min -1 , 0.42 min -1 , 0.25 min -1 . Description of the Drawings

[0038] Figure 1 In a-d are SEM and TEM images of the materials prepared in each stage in Example 1, where a is the TEM image of Fe 3 O 4 NPs in (1), b is the TEM image of the magnetic nanorobot (MNR-IIP) without HF treatment in (3), and c and d are the TEM and SEM images of the final product MNR-II-YS in (3).

[0039] Figure 2 is the BET data and pore size analysis diagram of the imprinted Yolk-Shell magnetic nanorobot (MNR-IIP-YS) in (3) of Example 1.

[0040] Figure 3 is the infrared spectrum diagram of the product MNR in (2) 1) in Example 1, the product MNR-MPS in (2) 2), and the product MNR-IIP-YS in (3) 2).

[0041] Figure 4 is the hysteresis loop test data diagram of the product Fe 3 O 4 NPs in (1) of Example 1, the product MNR-IIP in (3) 1), and the product MNR-IIP-YS in (3) 2).

[0042] Figure 5It is the adsorption capacity of MNR-IIP-YS in different pH environments in Example 4.

[0043] Figure 6 It shows the results of the adsorption kinetics experiment in Example 5.

[0044] Figure 7 It shows the results of the equilibrium adsorption experiment in Example 6.

[0045] Figure 8 It shows the competitive adsorption performance in the presence of multiple ions in Example 7.

[0046] Figure 9 It shows the results of the regeneration performance experiment of the material in Example 8.

[0047] Figure 10 It shows the results of the catalytic performance experiment of the adsorbed material (MNR-IIP-YS-Au) in Example 9. Detailed implementation method

[0048] Example 1:

[0049] (1) Preparation of iron oxide nanoparticles (Fe 3 O 4 NPs)

[0050] Disperse 3.2 g of FeCl 3 ·6H 2 O in 100 mL of ethylene glycol. Subsequently, add 1.2 g of Na 3 Cit·2H 2 O and 6.0 g of NaAc, mix well and then perform ultrasonic treatment until there is no obvious precipitate in the mixed solution. Transfer the mixture to a hydrothermal reaction kettle, react at a certain temperature of 200 °C for 10 h, cool to room temperature, then centrifuge and collect, wash several times with deionized water and ethanol, and dry in vacuum for later use.

[0051] (2) Preparation of vinyl-functionalized magnetic nanorobot (MNR-MPS)

[0052] 1) Add 25 mg of the Fe 3 O 4 NPs prepared in step (1) to 30 mL of absolute ethanol and disperse by ultrasonic treatment. Subsequently, place it in a water bath at 30 °C, add 1.7 mL of ammonia water, mechanically stir at 700 rpm for 20 min, then reduce the rotation speed to 300 rpm, add 0.15 mL of TEOS, and react for 15 min. Place it directly above a bar magnet with a magnetic field intensity of 7.8 mT for 100 s and then slowly place it on a flat place to stand for 12 h. Separate the product by magnet, wash several times with deionized water and ethanol to obtain magnetic nanorobot (MNR), and dry in vacuum for later use.

[0053] 2) Ultrasonically disperse 100 mg of the MNR prepared in step 1) in 40 mL of absolute ethanol and 10 mL of deionized water. Sequentially add 1.5 mL of ammonia water and 0.2 mL of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) at 70 °C and 800 rpm, and react for 24 h. Separate the product by a magnet, wash it several times with deionized water and ethanol to obtain vinyl-functionalized magnetic nanorobots (MNR-MPS), and dry it in vacuum for later use.

[0054] (3) Preparation of imprinted Yolk-Shell magnetic nanorobots (MNR-IIP-YS)

[0055] 1) Mix 0.4 mmol of HAuCl 4 , 0.8 mmol of vinylimidazole, 5 mL of deionized water, and 15 mL of methanol, then place them in a magnetic stirrer at 30 °C for pre-polymerization for 30 min. Then add 50 mg of MNR-MPS, 0.74 mL of ethylene glycol dimethacrylate, and 10 mg of azobisisobutyronitrile, and react at 70 °C for 12 h. Collect the product with a magnet, wash it several times with deionized water and ethanol to remove residual reagents, then soak it in 1 M acidic thiourea solution (pH = 1) for 6 h to remove the template on the imprinted polymer, and finally rinse it repeatedly with deionized water and ethanol to obtain the imprinted magnetic nanorobots (MNR-IIP), and dry it in vacuum for later use. The preparation process of the non-imprinted material (MNR-NIP) is the same, except that the template HAuCl 4 is not added.

[0056] 2) Add the solid obtained in step 1) to 20 mM hydrofluoric acid solution, shake for 20 min, collect the product with a magnet, wash it several times with deionized water and ethanol to remove residual reagents, to obtain the imprinted crosslinked Yolk-Shell magnetic nanorobots (MNR-IIP-YS) and non-imprinted Yolk-Shell magnetic nanorobots (MNR-NIP-YS), and dry them in vacuum for later use.

[0057] Figure 1 In a-d are the SEM and TEM images of the materials prepared in each stage in Example 1, where a is the TEM image of Fe 3 O 4 NPs in (1). It can be seen the particle size and uniformity of the magnetite nanoparticles. b is the TEM image of the magnetic nanorobots (MNR-IIP) without HF treatment in (3). It can be seen the clear rod-like structure and the thickness of the imprinted layer; c and d are the TEM and SEM images of the final product MNR-II-YS in (3). It can clearly see the mesoporous structure on its surface.

[0058] Figure 2 It is the BET data and pore size analysis chart of the imprinted Yolk-Shell magnetic nanorobot (MNR-IIP-YS) in (3) of Example 1. It can be seen that there is an obvious mesoporous structure, and the pore size is about 4.4 nm.

[0059] Figure 3 It is the infrared spectrum chart of the product MNR in (2) 1) of Example 1, the product MNR-MPS in (2) 2), and the product MNR-IIP-YS in (3) 2). It can be seen from the change of functional groups that the monomer vinylimidazole is successfully grafted.

[0060] Figure 4 It is the product Fe in (1) of Example 1 3 O 4 NPs, the hysteresis loop test data chart of the product MNR-IIP in (3) 1) and the product MNR-IIP-YS in (3) 2). It can be seen that the materials before and after etching both have strong paramagnetism (the maximum magnetization intensity before etching: 18.85 emu g -1 , after etching: 22.22 emu g -1 ), which confirms the construction of its mesoporous structure and the characteristics of being drivable by an external magnetic field and magnetic separation. Example 2:

[0061] (1) Preparation of iron oxide nanoparticles (Fe 3 O 4 NPs)

[0062] Disperse 1.6 g of FeCl 3 ·6H 2 O in 50 mL of ethylene glycol. Subsequently, add 0.6 g of Na 3 Cit·2H 2 O and 3.0 g of NaAc in sequence, mix evenly and then perform ultrasonic treatment until there is no obvious precipitate in the mixed solution. Transfer the mixture to a hydrothermal reaction kettle, react at a certain temperature of 200 °C for 12 h, centrifuge and collect after cooling to room temperature, wash several times with deionized water and ethanol, and dry in vacuum for later use.

[0063] (2) Preparation of vinyl-functionalized magnetic nanorobot (MNR-MPS)

[0064] 1) Add 50 mg of the Fe 3 O 4NPs were added to 60 mL of absolute ethanol and ultrasonically dispersed. Subsequently, it was placed in a water bath at 25 °C, 3.0 mL of ammonia water was added, and it was mechanically stirred at 600 rpm for 25 min. Then the rotation speed was reduced to 200 rpm, 0.3 mL of TEOS was added, and the reaction was carried out for 20 min. It was placed directly above a bar magnet with a magnetic field strength of 7.8 mT for 90 s and then slowly placed on a stable place and left to stand for 10 h. The product was separated by a magnet, washed several times with deionized water and ethanol, and magnetic nanorobots (MNR) were obtained. After vacuum drying, it was reserved for use.

[0065] 2) 100 mg of the MNR prepared in step 1) was ultrasonically dispersed in 40 mL of absolute ethanol and 10 mL of deionized water. At 60 °C and 600 rpm, 1.5 mL of ammonia water and 0.2 mL of 3-(isobutenyloxy)propyltrimethoxysilane (MPS) were successively added, and the reaction was carried out for 20 h. The product was separated by a magnet, washed several times with deionized water and ethanol, and vinyl-functionalized magnetic nanorobots (MNR-MPS) were obtained. After vacuum drying, it was reserved for use.

[0066] (3) Preparation of imprinted Yolk-Shell magnetic nanorobots (MNR-IIP-YS)

[0067] 1) 0.2 mmol of HAuCl 4 , 0.8 mmol of vinylimidazole, 5 mL of deionized water, and 15 mL of methanol were mixed, and then placed in a magnetic stirrer at 25 °C for pre-polymerization for 45 min. Then 50 mg of MNR-MPS, 0.74 mL of ethylene glycol dimethacrylate, and 10 mg of azobisisobutyronitrile were added, and the reaction was carried out at 70 °C for 14 h. The product was collected by a magnet and washed several times with deionized water and ethanol to remove residual reagents. Then it was soaked in 1 M acidic thiourea solution (pH = 1) for 4 h to remove the template on the imprinted polymer. Finally, it was repeatedly rinsed with deionized water and ethanol, and the obtained imprinted magnetic nanorobots (MNR-IIP) were vacuum dried and reserved for use. The preparation process of non-imprinted materials (MNR-NIP) was the same, except that the template HAuCl 4 .

[0068] 2) The solid obtained in step 1) was added to 20 mM hydrofluoric acid solution, shaken for 10 min, the product was collected by a magnet, and washed several times with deionized water and ethanol to remove residual reagents, and the obtained imprinted cross-linked Yolk-Shell magnetic nanorobots (MNR-IIP-YS) and non-imprinted Yolk-Shell magnetic nanorobots (MNR-NIP-YS) were vacuum dried and reserved for use.

[0069] Example 3:

[0070] (1) Iron oxide nanoparticles (Fe 3 O4 Preparation of NPs

[0071] Disperse 1.6 g of FeCl 3 ·6H 2 O in 50 mL of ethylene glycol. Subsequently, add 0.6 g of Na 3 Cit·2H 2 O and 3.0 g of NaAc in sequence. After mixing evenly, perform ultrasonic treatment until there is no obvious precipitate in the mixed solution. Transfer the mixture to a hydrothermal reaction kettle, react at a certain temperature of 220 °C for 9 h, cool to room temperature, then collect by centrifugation, wash several times with deionized water and ethanol, and dry in vacuum for later use.

[0072] (2) Preparation of vinyl-functionalized magnetic nanorobots (MNR-MPS)

[0073] 1) Add 50 mg of the Fe 3 O 4 NPs prepared in step (1) into 60 mL of absolute ethanol and disperse by ultrasonic treatment. Subsequently, place it in a water bath at 35 °C, add 3.3 mL of ammonia water, mechanically stir at 700 rpm for 15 min, then reduce the rotation speed to 400 rpm, add 0.3 mL of TEOS, and react for 20 min. Place it directly above a bar magnet with a magnetic field intensity of 7.8 mT for 120 s, then slowly place it on a stable place and let it stand for 15 h. Separate the product with a magnet, wash several times with deionized water and ethanol to obtain magnetic nanorobots (MNR), and dry in vacuum for later use.

[0074] 2) Ultrasonically disperse 100 mg of the MNR prepared in step 1) in 40 mL of absolute ethanol and 10 mL of deionized water. At 70 °C and 700 rpm, add 1.5 mL of ammonia water and 0.3 mL of 3-(methacryloyloxy)propyltrimethoxysilane (MPS) in sequence, react for 26 h, separate the product with a magnet, wash several times with deionized water and ethanol to obtain vinyl-functionalized magnetic nanorobots (MNR-MPS), and dry in vacuum for later use.

[0075] (3) Preparation of imprinted yolk-shell magnetic nanorobots (MNR-IIP-YS)

[0076] 1) Add 0.8 mmol of HAuCl 4, 0.8 mmol of vinylimidazole, 5 mL of deionized water, and 15 mL of methanol were mixed, and then placed in a magnetic stirrer at 30 °C for pre-polymerization for 60 min. Then, 50 mg of MNR-MPS, 0.74 mL of ethylene glycol dimethacrylate, and 10 mg of azobisisobutyronitrile were added, and the reaction was carried out at 70 °C for 15 h. The product was collected by a magnet and washed several times with deionized water and ethanol to remove the residual reagents. Then, it was soaked in a 1 M acidic thiourea solution (pH = 1) for 5 h to remove the template on the imprinted polymer. Finally, it was repeatedly rinsed with deionized water and ethanol to obtain the imprinted magnetic nanorobot (MNR-IIP). After vacuum drying, it was reserved for use. The preparation process of the non-imprinted material (MNR-NIP) was the same, except that the template HAuCl was not added. 4 .

[0077] 2) The solid obtained in step 1) was added to a 20 mM hydrofluoric acid solution and shaken for 30 min. The product was collected by a magnet and washed several times with deionized water and ethanol to remove the residual reagents, obtaining the imprinted cross-linked Yolk-Shell magnetic nanorobot (MNR-IIP-YS) and the non-imprinted Yolk-Shell magnetic nanorobot (MNR-NIP-YS). After vacuum drying, they were reserved for use.

[0078] Example 4:

[0079] Accurately weigh 3 mg of MNR-IIP-YS and MNR-NIP-YS prepared under the conditions described in Example 1 respectively, and add them to 3 mL of gold ion solutions with pH values of 1, 2, 3, 4, 5, 6 and a concentration of 150 mg / L respectively. Place them on a magnetic stirrer at 1000 rpm at 25 °C for 1 h. After separation by a magnet, an inductively coupled plasma optical emission spectrometer (ICP) was used to detect the concentration of gold ions in the solution, and three parallel experiments were carried out.

[0080] Figure 5 It is the result display of Example 4. It can be seen that the adsorption capacity of MNR-IIP-YS is the largest in an environment with a pH of 3, reaching 65.01 mg g -1 , which is 2.9 times that of MNR-NIP-YS.

[0081] Example 5:

[0082] Accurately weigh 3 mg of MNR-IIP-YS and MNR-NIP-YS respectively, and add them to 3 mL of gold ion solutions with a concentration of 150 mg / L and a pH value of 3 respectively. Place them on a magnetic stirrer at 1000 rpm at 25 °C. After 1, 5, 10, 20, 30, 45, 60 min respectively, the adsorbent was separated by a magnet, the adsorption solution was collected, and three parallel experiments were carried out. An inductively coupled plasma optical emission spectrometer (ICP) was used to detect the remaining gold ion concentration.

[0083] Figure 6 It is the display of the adsorption kinetics experiment results of Example 5. It can be seen that MNR-IIP-YS can achieve rapid enrichment of gold ions under the action of an external magnetic field, reaching 89.16% of the maximum adsorption capacity within 5 minutes and reaching the adsorption equilibrium within 20 minutes.

[0084] Example 6:

[0085] Accurately weigh 3 mg of MNR-IIP-YS and MNR-NIP-YS respectively, and add them to 3 mL of gold ion solutions (pH = 3) with concentrations of 10, 25, 50, 75, 100, 150, and 200 mg / L in sequence. Place them on a magnetic stirrer at 1000 rpm at 25 °C for 30 minutes, and collect the adsorption solution. The operations at 35 °C and 45 °C are the same as above. Conduct three parallel experiments, and use an inductively coupled plasma emission spectrometer (ICP) to detect the remaining gold ion concentration.

[0086] Figure 7 It is the display of the equilibrium adsorption experiment results of Example 6. It can be seen that as the initial concentration of gold ions increases, the adsorption capacity of MNR-IIP-YS gradually increases, reaching a maximum of 82.23 mg / g, which is 2.1 times that of MNR-NIP-YS, and the fitting results of the adsorption data are more in line with the Langmuir model.

[0087] Example 7:

[0088] Accurately weigh 3 mg of MNR-IIP-YS and MNR-NIP-YS respectively, and add them to 3 mL of simulated electronic waste leaching solution containing K + , Na + , Cr 3+ , Fe 3+ , Mn 2+ , Cu 2+ , Zn 2+ , Ni 2+ , Co 2+ , Pb 2+ , Au 3+ . Place them on a magnetic stirrer at 1000 rpm at 25 °C for 30 minutes, collect the adsorption solution. Conduct three parallel experiments, and use an inductively coupled plasma emission spectrometer (ICP) to detect the remaining gold ion concentration.

[0089] Figure 8 It is the display of the competitive adsorption performance in the presence of multiple ions in Example 7. The results show that MNR-IIP-YS has better selectivity for gold ions, significantly higher than that of MNR-NIP-YS, indicating that the ion imprinting technology can improve the selectivity of the material.

[0090] Example 8:

[0091] Accurately weigh 3 mg of MNR-IIP-YS and MNR-NIP-YS respectively, and add them to 3 mL of gold ion solution with a concentration of 150 mg / L and a pH value of 3. Place them on a magnetic stirrer at 25 °C and maintain for 30 min at a rotation speed of 1000 rpm. Then separate the adsorbent MNR-IIP-YS-Au by a magnet. After washing with deionized water, add an eluent prepared from 1 mol / L thiourea and 0.1 mol / L hydrochloric acid. Oscillate in a water bath for 2 h, then separate the adsorbent by a magnet, and wash with deionized water and ethanol. This is one cycle, and a total of five cycles are performed. Collect the adsorption solution, conduct three groups of parallel experiments, and use an inductively coupled plasma emission spectrometer (ICP) to detect the remaining gold ion concentration.

[0092] Figure 9 It is the experimental result display of the regeneration performance of the materials in Example 8. It can be seen that after 5 cycles, the adsorption performance of MNR-IIP-YS has not decreased significantly (9%), while the adsorption performance of MNR-NIP-YS has decreased more (21%), indicating that the ion imprinting technology can improve the stability and durability of the materials.

[0093] Example 9:

[0094] Mix 0.2 mL of 4-NP (4 mM) solution with 2 mL of freshly prepared NaBH 4 solution (0.2 M), and then add 2 mg of the adsorbed material (MNR-IIP-YS-Au) to initiate the reaction. For the degradation of organic dyes, mix 2 mL of MO (0.2 mM) solution with 0.2 mL of freshly prepared NaBH 4 solution (0.2 M), and then add 1 mg of MNR-IIP-YS-Au to initiate the reaction. The reaction conditions for MB are the same as those for MO. Measure the concentration at different time intervals using an ultraviolet-visible spectrophotometer.

[0095] Figure 10 It is the experimental result display of the catalytic performance of the adsorbed material (MNR-IIP-YS-Au) in Example 9. It can be seen that MNR-IIP-YS-Au has excellent activity in reducing 4-nitrophenol (4-NP) and degrading dyes such as methylene blue (MB) and methyl orange (MO). The reaction rate constants for 4-nitrophenol, methylene blue, and methyl orange are 0.20 min -1 、0.42 min -1 、0.25 min -1 .

Claims

1. Preparation method of gold ion-imprinted Yolk-Shell magnetic nanorobot, Characterized in that, Comprising the following steps: (1) Prepare iron oxide nanoparticles Fe 3 O 4 NPs for later use; (2) Prepare vinyl-functionalized magnetic nanorobot MNR-MPS for later use; (3) Preparation of gold ion-imprinted Yolk-Shell magnetic nanorobot MNR-IIP-YS; 3.1) Mix HAuCl 4 , vinylimidazole, deionized water, and methanol, then place it in a magnetic stirrer at a certain temperature for pre-polymerization for a period of time. Then add MNR-MPS, ethylene glycol dimethacrylate, and azobisisobutyronitrile, and carry out the polymerization cross-linking reaction at a certain temperature for a period of time. Collect the product with a magnet, wash it several times with deionized water and ethanol to remove the residual reagents, then soak it in an acidic thiourea solution for a period of time to remove the template on the imprinted polymer, and finally rinse it repeatedly with deionized water and ethanol to obtain the imprinted magnetic nanorobot MNR-IIP, which is dried in vacuum for later use; Among them, the dosage ratio of MNR-MPS, HAuCl 4 , vinyl imidazole, ethylene glycol dimethacrylate, azobisisobutyronitrile, deionized water and methanol is 50 mg: 0.4 mmol: 0.8 mmol: 0.74 mL: 10 mg: 5 mL: 15 mL; 3.2) Add the solid obtained in step 3.1) into a hydrofluoric acid solution with a certain concentration, shake for a period of time, collect the product with a magnet, and wash it several times with deionized water and ethanol to remove the residual reagents, obtaining the gold ion-imprinted Yolk-Shell magnetic nanorobot MNR-IIP-YS. After vacuum drying, it is reserved for later use.

2. The preparation method according to claim 1, Characterized in that, In step 3.1) of step (3), the pre-polymerization temperature is 25-30 °C and the time is 30-60 min.

3. The preparation method according to claim 1, Characterized in that, In step 3.1) of step (3), the polymerization cross-linking reaction time is 12-15 h and the reaction temperature is 70-80 °C.

4. The preparation method according to claim 1, Characterized in that, In step 3.1) of step (3), the concentration of the acidic thiourea solution is 1 mol / L, the pH is 1, and the elution time is 4-6 h.

5. The preparation method according to claim 1, Characterized in that, In step 3.2) of step (3), the concentration of the hydrofluoric acid solution is 20 mmol / L.

6. The preparation method according to claim 1, Characterized in that, In step 3.2) of step (3), the shaking time is 5-45 min.

7. Use of the gold ion-imprinted Yolk-Shell magnetic nanorobot prepared by the preparation method according to any one of claims 1 to 6 for adsorbing gold in the leaching solution of electronic waste.

8. A magnetic nanorobot MNR-IIP-YS-Au after capturing gold, Characterized in that, It is obtained by capturing gold with the gold ion-imprinted Yolk-Shell magnetic nanorobot MNR-IIP-YS prepared by the preparation method according to any one of claims 1 to 6.

9. Use of the magnetic nanorobot MNR-IIP-YS-Au after capturing gold according to claim 8 for catalytic degradation of dyes.

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