A preparation method and application of superparamagnetic adsorbent

Abstract

The invention discloses a method for preparing a superparamagnetic adsorbent, first preparing carbon-coated MnFe2O4 nanoparticles, then surface hydroxylation of the carbon-coated MnFe2O4 nanoparticles to introduce hydroxyl groups, and then cross-linking the surface hydroxyl groups with quercetin using glutaraldehyde as a cross-linking agent to obtain a superparamagnetic adsorbent. The adsorbent prepared by the invention is a core-shell structure, in which the carbon shell tightly wraps the MnFe2O4 core. The material has superparamagnetism and has a good adsorption effect on nanoplastic pollutants in water bodies. Compared with traditional methods such as filtration, flocculation and biological treatment, the superparamagnetic adsorbent of the invention has obvious advantages in removing micro-nanoplastics, with high adsorption capacity, high removal efficiency, low cost, and can be reused, which is green and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering, and specifically relates to a preparation method and application of a superparamagnetic adsorbent. Background Art

[0002] At present, microplastics have become a major environmental issue of global concern. Studies have found that micro-nano plastics can cause harm at the cellular and molecular levels, and have a great negative impact on the growth, development and reproduction of organisms. Micro-nano plastics can also continue to accumulate in the environment, adsorb and release harmful substances, which not only endangers the safety of the ecological environment, but also can enter the human body through the food chain and drinking water. Nanoplastics can even break through the gastrointestinal cell barriers of the human body and enter the human body circulation, which has great potential harm to human health. Microplastics have been listed as new pollutants. They are not only widely distributed in water environments such as lakes and rivers, but also difficult to decompose. They can survive in the environment for hundreds of years, and with the accumulation of time, the pollution continues to worsen. Studies have found that 81% of tap water and 93% of bottled water also contain micro-nano plastics, which can directly enter the human body. Therefore, the removal of micro-nano plastics in water has become an urgent problem to be solved.

[0003] As an emerging pollutant, there is currently a lack of targeted removal methods for micro-nano plastics in environmental water bodies and tap water. At present, typical microplastic treatment processes in water include traditional methods such as filtration, coagulation and biological treatment, but all have certain shortcomings. For example, it is difficult to effectively remove smaller micron or even nano-scale plastics through conventional filtration and coagulation methods in water plants, while biological treatment processes have harsh conditions and high costs. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a superparamagnetic adsorbent in view of the deficiencies in the prior art. The adsorbent prepared by the method has a superparamagnetic core-shell nanostructure and good adsorption performance, can be used for removing micro-nano plastics in water, and has a high removal rate, low cost, is green and environmentally friendly, and can be reused.

[0005] The present invention first prepares carbon-coated MnFe2O4 nanoparticles, then performs surface hydroxylation on the carbon-coated MnFe2O4 nanoparticles to introduce hydroxyl groups, and then uses glutaraldehyde as a cross-linking agent to cross-link the surface hydroxyl groups with quercetin to form a superparamagnetic adsorbent. The specific scheme is as follows:

[0006] A method for preparing a superparamagnetic adsorbent comprises the following steps:

[0007] (1) dissolving ferric chloride hexahydrate and manganese chloride tetrahydrate in ethylene glycol, then adding sodium acetate and polyethylene glycol, stirring evenly, then adding a glucose aqueous solution, stirring vigorously, to obtain a mixture;

[0008] (2) sealing the mixture in a stainless steel autoclave lined with polytetrafluoroethylene, heating to 210° C. for reaction for 3-5 hours, and then cooling to room temperature to obtain a reaction product, washing the reaction product and drying it to obtain carbon-coated MnFe2O4 nanoparticles;

[0009] (3) dispersing carbon-coated MnFe2O4 nanoparticles in deionized water to obtain a suspension, adding Fenton's reagent and stirring evenly, and then placing it under ultraviolet light for oxidation. After the oxidation, solid-liquid separation is performed, and the solid product is washed and dried, and then placed in a low-temperature plasma instrument, air is introduced, and plasma activation treatment is performed to obtain activated carbon-coated MnFe2O4 nanoparticles;

[0010] (4) The activated carbon-coated MnFe2O4 nanoparticles are dispersed in deionized water, and then quercetin is added and mixed evenly, and then glutaraldehyde is added and mixed evenly and heated to 80°C for reaction. After the reaction is completed, the precipitate is collected by centrifugation, washed and dried to obtain a superparamagnetic adsorbent.

[0011] Furthermore, in step (1), the mass ratio of ferric chloride hexahydrate, manganese chloride tetrahydrate, sodium acetate and polyethylene glycol is (2-4):1(8-9):(2-3).

[0012] Furthermore, in step (1), the concentration of the glucose aqueous solution is 1 mol / L, and the volume ratio of the sum of the masses of the ferric chloride hexahydrate and the manganese chloride tetrahydrate to the glucose aqueous solution is (1.5 g-3 g): 20 mL.

[0013] Furthermore, in step (2), the washing is performed by successively washing with deionized water and ethanol, each washing being performed 2-3 times.

[0014] Furthermore, in step (3), the volume ratio of the mass of the carbon-coated MnFe2O4 nanoparticles to the Fenton reagent is 1 g: (8 mL-12 mL).

[0015] Further, in step (3), the pH value of the Fenton reagent is 3, and the Fe 2+ The molar ratio of H2O2 is 1:5.

[0016] Furthermore, in step (3), the intensity of the ultraviolet light is 300-400 W / m 2, , the oxidation time is 2-3h.

[0017] Furthermore, in step (4), the mass ratio of the activated carbon-coated MnFe2O4 nanoparticles to quercetin is 1:(3-5).

[0018] Furthermore, in step (4), the volume ratio of the mass of the activated carbon-coated MnFe2O4 nanoparticles to glutaraldehyde is 0.5g:(20mL-25mL).

[0019] The superparamagnetic adsorbent prepared by the above method is used for adsorbing and removing micro-nano plastics in water bodies.

[0020] Beneficial effects of the present invention:

[0021] The present invention discloses a method for preparing a superparamagnetic adsorbent, which comprises first preparing carbon-coated MnFe2O4 nanoparticles, then subjecting the carbon-coated MnFe2O4 nanoparticles to surface hydroxylation to introduce hydroxyl groups, and then using glutaraldehyde as a crosslinking agent to crosslink the surface hydroxyl groups with quercetin to obtain a superparamagnetic adsorbent. Compared with the prior art, the method has the following advantages:

[0022] 1) The raw material of the carbon-coated MnFe2O4 nanoparticles prepared by the present invention is a core-shell structure, wherein the core is MnFe2O4 and the outer layer is a carbon shell. The particle size is about 100 nm and the thickness of the carbon shell is about 10 nm. The carbon shell provides good protection for the magnetic core MnFe2O4. The material has superparamagnetism and can be aggregated under the action of a magnet. After adsorption, it can be reused.

[0023] 2) Quercetin is introduced onto the surface of the superparamagnetic adsorbent of the present invention, which can adsorb micro-nano plastics through a large number of hydroxyl groups and benzene rings and has a high adsorption capacity. Therefore, it can be used for the rapid removal of micro-nano plastics in water with a high removal rate and low cost.

[0024] 3) Compared with traditional filtration, flocculation and biological treatment, the superparamagnetic adsorbent of the present invention has obvious advantages in removing micro-nano plastics, and has high removal efficiency. It can also be recovered by magnetic attraction and reused, which is green and environmentally friendly.

[0025] 4) The superparamagnetic adsorbent prepared by the present invention has a good adsorption effect on polystyrene plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 TEM image of the superparamagnetic adsorbent prepared in Example 1;

[0027] Figure 2 The results of the dispersibility and magnetic adsorption experiments of the superparamagnetic adsorbent prepared in Example 1 in water;

[0028] Figure 3 is the standard curve of absorbance and concentration of polystyrene nanoplastic solution;

[0029] Figure 4 The absorbance diagram of the polystyrene nanoplastic solution before and after adsorption by the superparamagnetic adsorbent prepared in Example 1 is shown. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] A method for preparing a superparamagnetic adsorbent comprises the following steps:

[0033] (1) 1.5 g of ferric chloride hexahydrate and 0.5 g of manganese chloride tetrahydrate were mixed and dissolved in 40 mL of ethylene glycol, and then 4 g of sodium acetate and 1.0 g of polyethylene glycol were added. After stirring evenly, 20 mL of a 1 mol / L glucose aqueous solution was added and stirred vigorously to obtain a mixture;

[0034] (2) the mixture was sealed in a 100 mL polytetrafluoroethylene-lined stainless steel autoclave, heated to 210° C. for 3 h, and then cooled to room temperature to obtain a reaction product, which was washed with deionized water and ethanol three times each, and then dried at 60° C. for 6 h to obtain carbon-coated MnFe2O4 nanoparticles;

[0035] (3) Disperse 1 g of carbon-coated MnFe2O4 nanoparticles in 100 mL of deionized water and ultrasonically disperse for 30 min to obtain a suspension. Add 10 mL of Fenton reagent (Fe2O4) with a pH value of 3. 2+ The molar ratio of H2O2 is 1:5) and stirred evenly, and then placed in a 300W / m 2, The product was oxidized under ultraviolet light for 2 h, and then solid-liquid separation was performed by an external magnet. The solid product was washed and dried, and then placed in a low-temperature plasma instrument. Air was introduced at a flow rate of 10 sccm and plasma activated for 15 min to obtain activated carbon-coated MnFe2O4 nanoparticles.

[0036] (4) 1 g of activated carbon-coated MnFe2O4 nanoparticles was dispersed in 100 mL of deionized water, and then 4 g of quercetin was added. After ultrasonication and stirring, 20 mL of glutaraldehyde was added. After mixing, the mixture was heated to 80 °C for 12 h. After the reaction was completed, the precipitate was collected by centrifugation, washed with deionized water, and dried to obtain a carbon-coated MnFe2O4 material with surface cross-linked quercetin, which was a superparamagnetic adsorbent.

[0037] Figure 1 TEM image of the superparamagnetic adsorbent prepared in Example 1, wherein Figure 1 The scale bar of A is 50nm, Figure 1 The scale bar of B is 200nm. Figure 1It can be seen that the structure of the superparamagnetic adsorbent is a core-shell structure. The internal black core is MnFe2O4, and the surface is covered with a carbon layer and cross-linked quercetin. The outer shell tightly protects the magnetic core, and there are no gaps on the surface, which can provide protection for the core.

[0038] 1. Dispersion of adsorbent in water and magnetic adsorption experiment:

[0039] 100 mg of the superparamagnetic adsorbent prepared in Example 1 was added to 10 mL of water. The adsorbent was quickly dispersed in the water by shaking. After standing for 5 minutes, a magnet was placed outside the bottle to observe the changes in the solution.

[0040] Figure 2 The results of the dispersibility and magnetic adsorption experiments of the superparamagnetic adsorbent prepared in Example 1 in water show that the adsorbent can be quickly dispersed in water, and the solution turns black after standing. A magnet is placed outside the bottle, and the solution can be quickly clarified, with the adsorbent gathering on one side of the magnet.

[0041] 2. Experiment on adsorption and removal of nanoplastics in water:

[0042] The polystyrene nanoplastic stock solution (Aladdin) was mixed with pure water to prepare a polystyrene nanoplastic solution with a concentration of 25 mg / L. 10 mL of the polystyrene nanoplastic solution was taken into a transparent reagent bottle, and 10 mg of the superparamagnetic adsorbent prepared in Example 1 was added. After shaking for 5 minutes, the mixture was allowed to stand. After solid-liquid separation was achieved using a magnet, the concentration of the polystyrene nanoplastic in the solution after adsorption was tested, and the removal rate of the polystyrene nanoplastic was calculated.

[0043] The test method of the concentration of polystyrene nanoplastics in the solution: The absorbance and concentration (C ps ) standard curve, such as Figure 3 As shown; then, by testing the absorbance of the polystyrene nanoplastic solution to be tested and combining it with the standard curve, the concentration of the polystyrene nanoplastic solution to be tested is obtained.

[0044] Figure 4 This is the absorbance diagram of the polystyrene nanoplastic solution before and after adsorption by the superparamagnetic adsorbent prepared in Example 1. It can be concluded that the removal rate of polystyrene nanoplastic reaches 98%.

Claims

1. A method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water, characterized in that: The steps include: (1) dissolving ferric chloride hexahydrate and manganese chloride tetrahydrate in ethylene glycol, then adding sodium acetate and polyethylene glycol, stirring evenly, then adding a glucose aqueous solution, stirring vigorously, to obtain a mixture; (2) sealing the mixture in a stainless steel autoclave lined with polytetrafluoroethylene, heating to 210° C. for reaction for 3-5 hours, and then cooling to room temperature to obtain a reaction product, washing the reaction product and drying it to obtain carbon-coated MnFe2O4 nanoparticles; (3) dispersing carbon-coated MnFe2O4 nanoparticles in deionized water to obtain a suspension, adding Fenton's reagent and stirring evenly, and then placing it under ultraviolet light for oxidation. After the oxidation, solid-liquid separation is performed, and the solid product is washed and dried, and then placed in a low-temperature plasma instrument, air is introduced, and plasma activation treatment is performed to obtain activated carbon-coated MnFe2O4 nanoparticles; (4) The activated carbon-coated MnFe2O4 nanoparticles are dispersed in deionized water, and then quercetin is added and mixed evenly, and then glutaraldehyde is added and mixed evenly and heated to 80°C for reaction. After the reaction is completed, the precipitate is collected by centrifugation, washed and dried to obtain a superparamagnetic adsorbent.

2. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (1), the mass ratio of ferric chloride hexahydrate, manganese chloride tetrahydrate, sodium acetate and polyethylene glycol is (2-4):1:(8-9):(2-3).

3. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (1), the concentration of the glucose aqueous solution is 1 mol / L, and the volume ratio of the sum of the masses of the ferric chloride hexahydrate and the manganese chloride tetrahydrate to the glucose aqueous solution is (1.5 g-3 g): 20 mL.

4. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (2), the washing is performed by successively washing with deionized water and ethanol, each washing is performed 2-3 times.

5. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (3), the volume ratio of the mass of the carbon-coated MnFe2O4 nanoparticles to the Fenton reagent is 1g:(8mL-12mL).

6. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (3), the pH value of the Fenton reagent is 3, and the Fe 2+ The molar ratio of H2O2 is 1:

5.

7. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (3), the intensity of the ultraviolet light is 300-400W / m 2 , the oxidation time is 2-3h.

8. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water as claimed in claim 1, characterized in that: In step (4), the mass ratio of the activated carbon-coated MnFe2O4 nanoparticles to quercetin is 1:(3-5).

9. The method for preparing a superparamagnetic adsorbent for adsorbing and removing micro-nano plastics in water according to any one of claims 1 to 8, characterized in that: In step (4), the volume ratio of the mass of the activated carbon-coated MnFe2O4 nanoparticles to glutaraldehyde is 0.5g:(20mL-25mL).

10. Use of the superparamagnetic adsorbent prepared by the method according to any one of claims 1 to 9 for adsorbing and removing micro-nano plastics in water.

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