Preparation and application of a functional magnetic material for enhanced adsorption of microplastics in water

Abstract

The present invention provides the preparation and application of a functionalized magnetic material that enhances the adsorption of microplastics in water. The magnetic material uses polyethylene glycol to modify the surface of magnetic ferroferric oxide to form a hydroxylated magnetic iron oxide nanomaterial. This material has the characteristics of a large specific surface area and a large number of adsorption active sites. It also possesses magnetic properties, making it easy to recycle. The present invention uses surface hydroxylated ferroferric oxide as an adsorbent for the removal of polyethylene microplastics from water. Results show that the hydroxylated adsorbent can efficiently remove polyethylene microplastics from water in a short period of time. Compared with nano-iron oxide without surface modification, the adsorption rate for polyethylene is increased by 54%. This invention verifies that surface functionalization can increase the adsorption rate of ferroferric oxide for polyethylene, and has broad application prospects in the treatment of microplastic pollution in water.

Description

Technical Field

[0001] The present invention belongs to the field of microplastic pollution control in the environment, and in particular relates to a hydroxylated magnetic ferrosoferric oxide material capable of enhancing the adsorption and removal of microplastics in water bodies. Background Art

[0002] Microplastics are small, inert plastic particles less than 5 mm in diameter. With the widespread use of plastic products worldwide, large quantities of microplastics are entering water bodies and are subsequently ingested by animals and humans through the food chain, posing a serious threat to human and environmental health. Microplastics are a major pollutant of concern in the 21st century, and effective removal methods are urgently needed. Currently, the main methods for removing microplastics from water bodies include physical methods such as adsorption and filtration precipitation; chemical methods such as ozone degradation, electrocoagulation, and ultraviolet oxidation; and biological methods such as bioreactors and biodegradation. Adsorption, with its advantages of low cost and ease of operation, holds great promise for application. However, it currently suffers from unstable removal efficiency and significant variations in adsorption of microplastics of different particle sizes. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method of a hydroxylated magnetic ferrosoferric oxide material and its application in adsorbing microplastics in water bodies, so as to provide an efficient and green microplastic water body adsorption material and treatment method.

[0004] The present invention selects magnetic nano-ferrosoferric oxide material with good adsorption properties, and performs surface functionalization modification on it to improve its dispersibility, increase its active adsorption sites, and enhance its physical and chemical binding ability with microplastics, thereby enhancing its removal of microplastics in water bodies. At the same time, the adsorbent is magnetic and easy to recycle and reuse, and has good application prospects.

[0005] In order to solve the above technical problems, the present invention provides a surface hydroxylated magnetic ferrosoferric oxide material that can enhance the adsorption of microplastics in water.

[0006] The first object of the present invention is to provide a method for preparing the hydroxylated magnetic ferrosoferric oxide material, comprising the following steps:

[0007] (1) Under the conditions of nitrogen flow and oil bath, ferric salt, ferrous salt and ammonia water are dispersed in oxygen-free water, reacted at 60°C for 1 hour, and then subjected to magnetic separation and washing to obtain nano-ferroferric oxide; nano-ferroferric oxide is magnetic ferroferric oxide;

[0008] (2) Under nitrogen gas and oil bath conditions, the nano-ferroferric oxide described in step (1) is dispersed in oxygen-free water with polyethylene glycol added, reacted at 60° C.-80° C. for 1 h-2 h, and subjected to magnetic separation, washing, and drying to obtain a hydroxylated magnetic ferroferric oxide material.

[0009] In one embodiment of the present invention, in step (1), the molar ratio of ferric iron to ferrous iron is 2:1-3:1.

[0010] In one embodiment of the present invention, in step (1), the concentration of the mixed solution of ferric iron and divalent iron can be appropriately increased. Increasing the concentration of the raw materials during preparation can improve the yield of the product. The amount of ammonia water added can be appropriately increased. In step (1), the pH is adjusted to 10.5-11.5 by adding ammonia water; the mass volume ratio of the ferric iron salt to the oxygen-free water is (1-3) g:10 mL.

[0011] In one embodiment of the present invention, in step (1) and step (2), magnetic separation uses a strong magnet, and the magnetic separation time is 5-10 minutes. The strong magnet is a neodymium iron boron strong magnet, and can also be other strong magnets.

[0012] In one embodiment of the present invention, in step (1) and step (2), the washing liquids are deionized water and ethanol, and the washing is performed multiple times respectively.

[0013] In one embodiment of the present invention, in step (2), a vacuum freeze dryer is used for drying at a temperature of -40°C to -50°C for 8-12 hours. This drying method can improve the plastic adsorption performance of the material and make the material less susceptible to oxidation.

[0014] In one embodiment of the present invention, the hydroxylated material in step (2) is polyethylene glycol. In step (2), the mass volume ratio of polyethylene glycol to oxygen-free water is 0.04 g: (400-600) mL.

[0015] The second object of the present invention is to provide a surface hydroxylated magnetic ferrosoferric oxide material.

[0016] The third object of the present invention is to provide an application of the surface hydroxylated magnetic ferroferric oxide material in the field of microplastic adsorption. The specific steps are: adding the surface hydroxylated magnetic ferroferric oxide material to water containing microplastics, and the amount of the surface hydroxylated magnetic ferroferric oxide material added is 1.0-4.0g·L -1 More preferably, the amount of the surface hydroxylated magnetic ferrosoferric oxide material applied is 2.0-3.0 g·L -1 During adsorption, the pH is preferably 6.5-7.5. The temperature during adsorption can be 5°C-60°C, with higher temperatures resulting in higher adsorption efficiency. The adsorption time is preferably 10-120 minutes. The particle size of the microplastic is preferably greater than 150 mesh, more preferably 200-1500 mesh. In one embodiment, the particle size of the microplastic can be 200-1000 mesh.

[0017] The preferred concentration of PE (polyethylene) in the microplastic water to be treated is 1.0-4.0 g·L -1 .

[0018] The fourth object of the present invention is to provide the use of surface hydroxylated magnetic ferrosoferric oxide material as a functional magnetic material for enhancing the adsorption of microplastics in water bodies.

[0019] The technical solution of the present invention has the following advantages over the prior art:

[0020] This invention provides a material method for enhancing the adsorption of microplastics in water by hydroxylating the surface of Fe₃O₄, thereby enhancing its adsorption capacity for microplastics. The synthesis process of this functionalized material is simple, with a short preparation cycle, low cost, and easy recycling. This material has promising applications in the treatment and recycling of microplastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the SEM image of the hydroxylated magnetic ferroferric oxide material;

[0022] Figure 2 It is the Fourier infrared chromatogram of magnetic ferroferric oxide and hydroxylated magnetic ferroferric oxide materials;

[0023] Figure 3 This is a physical picture of the hydroxylated magnetic ferroferric oxide material;

[0024] Figure 4 Schematic diagram of the dispersion and magnetic adsorption of hydroxylated magnetic ferroferric oxide materials;

[0025] Figure 5 A bar graph comparing the adsorption rates of the present invention and other surface-modified magnetic ferrosoferric oxide materials;

[0026] Figure 6 The bar graph of the adsorption rate of polyethylene with different particle sizes according to the present invention;

[0027] Figure 7 The bar graph is a graph showing the adsorption rate of 1000 mesh polyethylene at different concentrations according to the present invention;

[0028] Figure 8 The figure is a bar graph showing the effect of different dosages on the adsorption rate of 1000 mesh polyethylene according to the present invention;

[0029] Figure 9 The bar graph of the adsorption rate of 1000 mesh polyethylene at different pH values of the present invention;

[0030] Figure 10 is a line graph showing the adsorption rate of 1000 mesh polyethylene at different times according to the present invention;

[0031] Figure 11 The figure is a bar graph showing the adsorption rate of 1000 mesh polyethylene at different temperatures according to the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and specific examples so that those skilled in the art can better understand the present invention and implement it, but the examples given are not intended to limit the present invention.

[0033] In this specification, hydroxylated magnetic ferrosoferric oxide and surface hydroxylated magnetic ferrosoferric oxide have the same meaning.

[0034] In the accompanying drawings, Parallel 1, Parallel 2, and Parallel 3 refer to three parallel samples.

[0035] Example 1

[0036] A hydroxylated magnetic ferroferric oxide material and a preparation method thereof, specifically comprising the following steps:

[0037] (1) Weigh 57.2783 g of ferric chloride hexahydrate and 28.6274 g of ferrous sulfate heptahydrate and disperse them in 500 ml of oxygen-free water (under nitrogen protection). After stirring for 10 min, transfer them to a 1000 mL three-necked flask, add ammonia water to adjust the pH to 11, react in an 80 °C oil bath for 2 h, cool to room temperature, take out the sample, and use magnetic separation method (magnetic separation for 10 min) to wash three times with deionized water and ethanol respectively (first wash with deionized water 3 times, then wash with ethanol 3 times, the same below) to obtain magnetic ferrosoferric oxide material.

[0038] (2) Under nitrogen protection, the prepared magnetic ferroferric oxide material was dispersed in 500 ml of oxygen-free water, 0.04 g of polyethylene glycol 4000 was added, and the mixture was reacted in an 80 °C oil bath for 1 h. After cooling to room temperature, the sample was taken out and magnetic separation was used (magnetic separation for 10 min). The sample was washed three times with deionized water and ethanol respectively, and dried in a vacuum freeze drying oven (drying temperature was -45 °C and drying time was 10 h) to obtain a hydroxylated magnetic ferroferric oxide material.

[0039] In step (1) and step (2), all stirring processes require nitrogen flow.

[0040] Figure 1 The figure shows the SEM image of the hydroxylated magnetic ferroferric oxide material. It can be seen that the ferroferric oxide material is well spherical, and most of the particle sizes are within 20nm. Figure 2 The figure shows the Fourier infrared spectrum of the hydroxylated magnetic ferroferric oxide material, indicating that the ferroferric oxide has been loaded with hydroxyl groups.

[0041] Figure 3 The picture shows the physical object of hydroxylated magnetic ferroferric oxide material. Figure 4 It can be seen that it has good dispersibility in water, and the effect diagram of its magnetic separation in water for 1 minute shows that it can be quickly separated by magnetic separation.

[0042] Example 2

[0043] Comparative analysis of the adsorption performance of the hydroxylated magnetic ferroferric oxide material prepared in Example 1 and other surface-modified magnetic ferroferric oxide materials on the same type of microplastics:

[0044] Weigh 0.2g of hydroxylated magnetic ferroferric oxide ( Figure 5 PEG), non-surface-modified magnetic ferroferric oxide (Fe3O4), amino-modified magnetic ferroferric oxide (PEI) and carboxylated magnetic ferroferric oxide (CA) were dispersed in a 250mL conical flask filled with 100mL deionized water, and the conical flask was placed in an ultrasonic cleaner for 5-10 minutes to uniformly disperse the hydroxylated magnetic ferroferric oxide and other materials. 0.3g of 1000-mesh polyethylene was added to the conical flask, and the mixture was shaken in a constant temperature oscillator at 25°C and 180rpm for 2h. The mixture was taken out for magnetic separation for 5-10min, and the solution was filtered using a suction filter. The filter paper was taken out and placed in a 50mL conical flask for drying and weighing. The adsorption rate is as follows: Figure 5 As shown in the examples, hydroxylated magnetic ferrosoferric oxide has a better adsorption effect on microplastics under neutral conditions.

[0045] Example 3

[0046] Analysis of the application of the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1 to the adsorption of microplastics of different particle sizes:

[0047] Weigh 0.2g of hydroxylated magnetic ferroferric oxide (PEG / Fe3O4) and disperse it in a 250mL conical flask filled with 100mL deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10min to evenly disperse the hydroxylated magnetic ferroferric oxide. Add 0.3g of 100 mesh, 200 mesh, and 1000 mesh polyethylene to the conical flask respectively. Oscillate for 2h in a constant temperature oscillator at 25℃ and 180rpm. Remove the solution and magnetically separate it for 5-10min. Use a suction filter to filter the solution. Take out the filter paper and place it in a 50mL conical flask to dry and weigh it. The adsorption rate is as follows: Figure 6 As shown in the examples, hydroxylated ferrosoferric oxide has an adsorption effect on polyethylene of different particle sizes, and hydroxylated ferrosoferric oxide has a better adsorption effect on small particles of microplastics.

[0048] in, Figure 6The Fe3O4 in the mixture is magnetic ferroferric oxide without surface modification. For 200 mesh and 1000 mesh polyethylene, the adsorption performance of hydroxylated magnetic ferroferric oxide is significantly better than that of magnetic ferroferric oxide without surface modification.

[0049] Example 4

[0050] The maximum adsorption capacity of microplastics was analyzed using the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1:

[0051] Weigh 0.2g of hydroxylated magnetic ferroferric oxide and disperse it in a 250mL conical flask filled with 100mL deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10min to evenly disperse the hydroxylated magnetic ferroferric oxide. Add 0.1g, 0.2g, and 0.3g of 1000-mesh polyethylene to the conical flask respectively. Oscillate in a constant temperature oscillator at 25°C and 180rpm for 2h. Remove the solution and magnetically separate it for 5-10min. Filter the solution with a suction filter. Take out the filter paper and place it in a 50mL conical flask to dry and weigh it. The adsorption rate is as follows: Figure 7 As shown in the examples, the adsorption rate of hydroxylated ferrosoferric oxide on polyethylene increases with the increase of polyethylene concentration, and the maximum adsorption amount can reach 82.81%.

[0052] Example 5

[0053] Dosage analysis of microplastic adsorption using the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1:

[0054] Weigh 0.1, 0.2, and 0.4 g of hydroxylated magnetic ferroferric oxide respectively and disperse them in a 250 mL conical flask filled with 100 mL of deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10 minutes to evenly disperse the hydroxylated magnetic ferroferric oxide. Add 0.3 g of 1000 mesh polyethylene to the conical flask respectively and oscillate in a constant temperature oscillator at 25 ° C and 180 rpm for 2 hours. Remove the solution and magnetically separate it for 5-10 minutes. Use a suction filter to filter the solution, remove the filter paper and place it in a 50 mL conical flask to dry, and weigh it. The adsorption rate is as follows: Figure 8 As shown in the examples, the higher the concentration of hydroxylated ferrosoferric oxide, the higher the adsorption rate of polyethylene. For environmental protection, 2 g / L of hydroxylated ferrosoferric oxide is selected as the optimal addition amount.

[0055] Example 6

[0056] The environmental pH range for microplastic adsorption using the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1 was analyzed:

[0057] Weigh 0.2g of hydroxylated magnetic ferroferric oxide and disperse it in a 250mL conical flask filled with 100mL deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10min to evenly disperse the hydroxylated magnetic ferroferric oxide. Adjust the pH value to 3, 5, 7, 9, and 11. Add 0.3g of 1000 mesh polyethylene to the conical flask respectively. Oscillate in a constant temperature oscillator at 25℃ and 180rpm for 2h. Remove the solution and magnetically separate it for 5-10min. Use a suction filter to filter the solution. Take out the filter paper and place it in a 50mL conical flask to dry and weigh it. The adsorption rate is as follows: Figure 9 As shown in the examples, the adsorption rate of hydroxylated ferrosoferric oxide on polyethylene is the highest under neutral conditions, and the adsorption performance of hydroxylated ferrosoferric oxide will be affected under extremely acidic and alkaline conditions.

[0058] Example 7

[0059] Kinetic analysis of microplastic adsorption using the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1:

[0060] Weigh 0.2g of hydroxylated magnetic ferroferric oxide and disperse it in a 250mL conical flask filled with 100mL of deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10min to evenly disperse the hydroxylated magnetic ferroferric oxide. Add 0.3g of 1000 mesh polyethylene to the conical flask and oscillate in a constant temperature oscillator at 25°C and 180rpm. Take samples at 5min, 10min, 20min, 30min, 60min, 90min, 120min, and 150min and perform magnetic separation for 5-10min. Use a suction filter to filter the solution, take out the filter paper and place it in a 50mL conical flask to dry, and weigh it. The adsorption rate is as follows: Figure 10 As shown in the example, the hydroxylated ferrosoferric oxide was rapidly adsorbed in 10 min, and then the adsorption slowed down and reached adsorption saturation in 120 min.

[0061] Example 8

[0062] Analysis of the ambient temperature range for microplastic adsorption using the hydroxylated magnetic ferrosoferric oxide material prepared in Example 1:

[0063] Weigh 0.2g of hydroxylated magnetic ferroferric oxide and disperse it in a 250mL conical flask filled with 100mL deionized water. Place the conical flask in an ultrasonic cleaner and ultrasonicate for 5-10min to evenly disperse the hydroxylated magnetic ferroferric oxide. Add 0.3g of 1000 mesh polyethylene to the conical flask respectively. Oscillate at 5℃, 25℃, and 40℃ in an oscillator at 180rpm for 2h. Remove the solution and magnetically separate it for 5-10min. Use a suction filter to filter the solution. Take out the filter paper and place it in a 50mL conical flask to dry and weigh it. The adsorption rate is as follows: Figure 11As shown in the examples, the adsorption performance is good at different temperatures. The higher the temperature, the better the adsorption performance of hydroxylated ferrosoferric oxide on polyethylene.

[0064] The magnetic material of the present invention uses polyethylene glycol to modify the surface of magnetic ferroferric oxide to form a hydroxylated magnetic iron oxide nanomaterial, which has the characteristics of large specific surface area, multiple adsorption active sites, and magnetic properties, making it easy to recycle. The present invention uses surface hydroxylated ferroferric oxide as an adsorbent for removing polyethylene microplastics from water bodies. The results show that the hydroxylated adsorbent can efficiently remove polyethylene microplastics from water bodies in a short period of time. Compared with nano-iron oxide without surface modification, the adsorption rate of polyethylene is increased by 54%. This invention verifies that surface functionalization can increase the adsorption rate of ferroferric oxide on polyethylene, and has broad application prospects in the treatment of microplastic pollution in water bodies.

[0065] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. Application of surface hydroxylated magnetic ferroferric oxide material in the treatment of microplastics in water, characterized by: Add surface hydroxylated magnetic ferroferric oxide material to water containing microplastics. The amount of surface hydroxylated magnetic ferroferric oxide material added is 1.0-4.0 g·L -1 ; During adsorption, the pH is 6.5-7.5; The specific steps for preparing surface hydroxylated magnetic ferroferric oxide material are as follows: (1) Under nitrogen gas and oil bath conditions, ferric iron salt, ferrous iron salt and ammonia water are dispersed in oxygen-free water, the pH is adjusted to 10.5-11.5 by adding ammonia water, and the reaction is carried out at 60℃-80℃ for 1h-2h. Nano-ferrosoferric oxide is obtained by magnetic separation and washing; (2) Under nitrogen gas and oil bath conditions, the nano-ferroferric oxide described in step (1) is dispersed in oxygen-free water with polyethylene glycol added, and the mixture is reacted at 60°C-80°C for 1h-2h. The hydroxylated magnetic ferroferric oxide material is obtained by magnetic separation, washing, and drying.

2. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water bodies, characterized in that: When preparing the surface hydroxylated magnetic ferroferric oxide material, the molar ratio of trivalent iron to divalent iron is 2:1 to 3:

1.

3. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water bodies, characterized in that: In step (1), the mass volume ratio of the ferric salt to the oxygen-free water is (1-3) g:10 mL.

4. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water bodies, characterized in that: In steps (1) and (2), magnetic separation uses a strong magnet and the magnetic separation time is 5-10 minutes.

5. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water bodies, characterized in that: In steps (1) and (2), the washing liquids are deionized water and ethanol, and the washing is performed multiple times respectively.

6. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water, characterized in that: In step (2), drying is performed using a vacuum freeze dryer at a drying temperature of -40°C to -50°C and a drying time of 8-12 hours.

7. The use of the surface hydroxylated magnetic ferrosoferric oxide material according to claim 1 in the treatment of microplastics in water, characterized in that: In step (2), the mass volume ratio of polyethylene glycol to oxygen-free water is 0.04 g: (400-600) mL.

Images