A microplastic-based ferroferric oxide / manganese dioxide / biochar core-shell composite material and a preparation method thereof

Abstract

This invention relates to a microplastic-based core-shell composite material of iron(III) oxide (Fe3O4) / manganese(II) oxide (Mn2O4) / biochar and its preparation method, belonging to the technical field of waste resource utilization and environmental functional materials. The method uses waste microplastic powder as the core carrier, and coats its surface with an in-situ layer of iron(III) oxide through a co-precipitation reaction. Subsequently, through two stepwise hydrothermal reactions, the growth of the manganese(II) oxide shell and the outer biochar coating is controlled to obtain a continuous and dense core-shell structure. This invention utilizes the low-density characteristics of waste microplastics to reduce the overall density of the composite material, enabling it to suspend or float in the upper and middle layers of water, increasing the probability of contact with water pollutants. Simultaneously, the material also possesses the magnetic response characteristics of iron(III) oxide, allowing for solid-liquid separation and rapid recovery through an external magnetic field. This invention achieves the resource utilization of solid waste, and the prepared composite material can be applied to environmental remediation fields such as wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental governance and waste resource utilization technology, specifically relating to a method for preparing microplastic@ferric oxide / manganese dioxide / biochar composite materials using microplastics as the core through co-precipitation and a two-step hydrothermal method. Background Technology

[0002] Microplastic pollution has become a global environmental problem. Microplastics are widely found in water bodies, soil, and other environments, originating from sources such as the decomposition of plastic products and industrial waste. Not only are microplastics difficult to degrade naturally, but they also cause serious harm to ecosystems. For example, if ingested by organisms, they can affect their growth and reproduction, and they may carry harmful substances into the food chain, threatening human health.

[0003] Iron oxide (Fe3O4) possesses magnetic properties and certain catalytic performance, showing potential applications in magnetic separation and pollutant degradation. Manganese dioxide (MOC) is an excellent catalyst and electrode material, suitable for catalytic oxidation reactions and battery applications. Biochar, produced from the pyrolysis of biomass, has a rich porous structure and excellent adsorption properties, improving soil quality and adsorbing pollutants, while also enabling the resource utilization of waste biomass.

[0004] However, existing microplastic treatment methods have limited effectiveness, and the process of preparing composite materials from waste has many drawbacks. In practical applications of traditional powder catalysts or high-density magnetic composite materials for water treatment, their high density makes them prone to self-sinking in water. This sinking phenomenon causes the material to quickly fall to the bottom, significantly reducing the effective contact area with pollutants in the surface and middle layers of the water, thus lowering the probability of adsorption and catalytic reactions. Furthermore, in the preparation of multi-component composite materials using traditional methods, the lack of precise control over the multiphase interface growth process leads to the easy self-aggregation of nanoparticles, resulting in the burial of active sites and low solid-liquid separation efficiency during subsequent magnetron sputtering recovery.

[0005] In summary, how to utilize low-density waste as a core carrier to address the technical shortcomings of traditional composite materials, such as high density leading to easy settling and aggregation, low contact efficiency with pollutants, and difficulty in efficient magnetic recycling in the later stages, is a pressing technical problem to be solved in the field of waste resource recycling and environmental governance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a core-shell composite material based on microplastics, namely, iron(III) oxide / manganese(II) oxide / biochar, and its preparation method. This method employs a co-precipitation process combined with a stepwise, two-stage hydrothermal process design, using low-density waste microplastic powder as a lightweight core carrier. While maintaining the material's buoyancy and magnetron recyclability, it increases the contact area between the material and pollutants in the upper layer of water, thus solving the technical problems of traditional composite materials being dense, prone to settling, easily agglomerating, and difficult to recycle.

[0007] Specifically, to achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect of the present invention, a core-shell composite material of iron(III) oxide / manganese(II) oxide / biochar made from microplastic waste is provided, and a method for preparing the same is also provided, characterized by comprising the following steps: 1. Preparation of iron salt solution: Dissolve iron salt in deionized water to prepare an iron salt solution with a concentration of 0.1-1 mol / L; 2. Preparation of manganese dioxide precursor solution: Dissolve potassium permanganate in deionized water to prepare a manganese dioxide precursor solution with a concentration of 0.1-1 mol / L; 3. Biochar preparation: Organic waste is pyrolyzed under anaerobic conditions, ground into powder, washed and dried; 4. Co-precipitation in situ coating: Add microplastic powder to iron salt solution, stir for 1 hour, add ammonia dropwise to adjust pH=9, react in an oven at 80℃ for 12 hours, separate solid and liquid, wash the solid 1-3 times with deionized water and anhydrous ethanol, and dry at 60℃ for 6-12 hours to obtain microplastic@iron tetroxide core-shell material. 5. First hydrothermal reaction: Then add manganese dioxide precursor solution, and add 37% hydrochloric acid solution dropwise while stirring to obtain a mixed solution. Transfer the mixed solution to a reaction vessel and react at 110℃ for 6-15 hours. After the reaction is completed, separate the solid and liquid. Wash the solid 1-3 times with deionized water and anhydrous ethanol, and dry at 60℃ for 6-12 hours to obtain microplastic@iron(II) tetroxide / manganese dioxide core-shell material. 6. Second hydrothermal reaction: The materials obtained above and biochar are mixed and dispersed in deionized water at a mass ratio of 1:2-1:5. The mixture is ultrasonicated and stirred until homogeneous to form a suspension. The suspension is transferred to a reaction vessel and reacted at 100-150℃ for 6-15 hours. After the reaction, the solid and liquid are separated. The solid is washed 1-3 times with deionized water and anhydrous ethanol and dried at 60℃ for 6-12 hours to obtain a microplastic@iron(II) oxide / manganese(II) oxide / biochar magnetic core-shell composite material.

[0008] Furthermore, the microplastic particles have a particle size ranging from 0.4 μm to 4 mm and are made of polyethylene (PE).

[0009] Furthermore, the molar ratio of ferric chloride to ferrous chloride in the iron salt is 1.5:1 to 2.5:1.

[0010] Furthermore, the iron salt is ferric chloride and ferrous chloride, and the organic waste is straw, fruit shells, sawdust, branches or fallen leaves.

[0011] Furthermore, the concentration of ammonia in step (4) is 10-25%.

[0012] Furthermore, the solid-liquid separation is performed using vacuum filtration or centrifugation.

[0013] Another object of the present invention is to provide a microplastic@iron tetroxide / manganese dioxide / biochar magnetic core-shell composite material.

[0014] Another objective of this invention is to provide an application of the aforementioned microplastic@iron tetroxide / manganese dioxide / biochar magnetic core-shell composite material in environmental remediation fields such as wastewater treatment.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The overall density of the composite material is reduced, enabling it to suspend and float in the upper and middle layers of water. This invention utilizes the low density and buoyancy properties of waste microplastics as a core carrier, allowing the resulting core-shell composite material to remain in the upper and middle layers of water for extended periods. This avoids the reduced contact area caused by the self-sinking of high-density magnetic materials and increases the likelihood of the material reacting with pollutants in the upper and middle layers of water.

[0016] This invention improves the affinity of the hydrophobic interface and inhibits the disordered aggregation of nanoparticles. Traditional one-step hydrothermal methods are prone to causing impurity phase precipitation and disordered aggregation when multiple ions react simultaneously. This invention adopts a co-precipitation combined with a stepwise two-stage hydrothermal process. First, a magnetite magnetic transition layer is constructed in situ on the surface of hydrophobic microplastics to improve the interface affinity. Then, the growth of the manganese dioxide shell and the outer biochar coating is controlled stepwise to avoid chaotic aggregation between components, forming a continuous and dense core-shell structure from the inside out, consisting of a microplastic core, a magnetite inner shell, a manganese dioxide outer shell, and a biochar outer coating.

[0017] This invention combines buoyancy and magnetic responsiveness, improving solid-liquid recovery efficiency. The composite material constructed in this invention uses microplastics as the buoyancy core, while simultaneously encapsulating a magnetic layer of iron oxide. This structure allows the material to maintain a floating state in the upper-middle layer of water and exhibits sensitive response characteristics to external magnetic fields. After water treatment, it can be attracted and recovered by an external magnetic field, avoiding the recovery difficulties caused by material sinking.

[0018] This invention achieves the resource-based recycling of solid waste. It synergistically transforms waste microplastics and organic waste biochar into environmentally functional materials under mild process conditions, providing a feasible approach for solid waste management and waste-to-waste treatment. Attached Figure Description

[0019] Figure 1 Scanning electron microscope (SEM) images of microplastics, microplastics@Fe3O4, microplastics@Fe3O4 / Mn2O4, and microplastics@Fe3O4 / Mn2O4 / Biochar are shown, where a is microplastic (PE), b is microplastics@Fe3O4, c is microplastics@Fe3O4 / Mn2O4, and d is microplastics@Fe3O4 / Mn2O4 / Biochar. Detailed Implementation

[0020] The present invention will be described in detail below with reference to the embodiments. However, the scope of protection of the present invention is not limited to the following embodiments. Any simple changes made in accordance with the scope of the patent application and the contents of the specification of the present invention shall fall within the scope of protection of the present invention. Example

[0021] The preparation method of the microplastic@iron(II)O3 / manganese(II)O3 / biochar composite material provided by the present invention includes the following steps: (1) Weigh 0.72g of ferrous chloride and 1.62g of ferric chloride and dissolve them in 100ml of deionized water; (2) Prepare 50 ml of 0.1 M potassium permanganate solution; (3) The fruit shells are dried and crushed, and then pyrolyzed under anaerobic conditions to obtain biochar. The biochar is then ground into powder, washed, and dried to remove impurities; (4) Add 1g of microplastic to the iron salt solution, stir for 1 hour, add ammonia dropwise at a uniform rate, adjust pH=9, react in an oven at 80℃ for 12 hours, separate the solid and liquid, wash the solid three times with deionized water and anhydrous ethanol, and dry at 60℃ for 12 hours to obtain microplastic@iron tetroxide core-shell material. (5) Take 0.5g of microplastic@Fe3O4, add manganese dioxide precursor solution, and add 0.9ml of 37% hydrochloric acid solution dropwise while stirring. Transfer the mixed solution to the reaction vessel and react at 110℃ for 9 hours. After the reaction is completed, separate the solid and liquid, wash the solid three times with deionized water and anhydrous ethanol, and dry at 60℃ for 12 hours to obtain microplastic@Fe3O4 / manganese dioxide core-shell material. (6) Weigh 0.3g of microplastic@iron(II)O3 / manganese(II)O3 and 1g of biochar powder and disperse them in 40ml of deionized water. Sonicate and stir until the dispersion is uniform. Transfer the suspension to a reaction vessel and react at 110℃ for 12 hours. After the reaction is completed, the solid and liquid are separated. Wash the solid three times with deionized water and anhydrous ethanol. Dry at 60℃ for 12 hours to obtain microplastic@iron(II)O3 / manganese(II)O3 / biochar magnetic core-shell composite material.

[0022] After preparation, the above materials were characterized in terms of morphology and properties, and the test and analysis results are as follows: Figure 1 As shown.

[0023] Figure 1 a is a SEM image of microplastics (PE); Figure 1 b is the SEM image of the microplastic@Fe3O4; Figure 1 c is the SEM image of the microplastic@iron(II) oxide / manganese(II) oxide; Figure 1 Figure d shows the SEM image of microplastics@Fe3O4 / manganese dioxide / biochar. As can be seen from the figure, the initial polyethylene (PE) core is smooth and spherical (Figure a); after loading Fe3O4, the surface of the microplastic is covered with particles, and the surface roughness increases (Figure b); the composite material surface in Figure c has a flower-like porous morphology; and the material surface in Figure d is coated with biochar particles.

[0024] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A core-shell composite material based on microplastics (iron tetroxide / manganese dioxide / biochar) and its preparation method, characterized in that, Includes the following steps: (1) Preparation of iron salt solution: Dissolve iron salt in deionized water to prepare an iron salt solution with a concentration of 0.1-1 mol / L; (2) Preparation of manganese dioxide precursor solution: Dissolve potassium permanganate in deionized water to prepare a manganese dioxide precursor solution with a concentration of 0.1-1 mol / L; (3) Biochar preparation: organic waste is pyrolyzed under anaerobic conditions, ground into powder, washed and dried; (4) Co-precipitation in situ coating: Add microplastic powder to iron salt solution, stir for 1 hour, add ammonia dropwise to adjust pH=9, react in an oven at 80℃ for 12 hours, separate solid and liquid, wash solid with deionized water and anhydrous ethanol 1-3 times, dry at 60℃ for 6-12 hours to obtain microplastic@iron tetroxide core-shell material; (5) First hydrothermal reaction: Then add manganese dioxide precursor solution, and add 37% hydrochloric acid solution dropwise while stirring to obtain a mixed solution. Transfer the mixed solution to the reaction vessel and react at 110°C for 6-15 hours. After the reaction is completed, the solid and liquid are separated. Wash the solid 1-3 times with deionized water and anhydrous ethanol, and dry at 60°C for 6-12 hours to obtain microplastic@iron tetroxide / manganese dioxide core-shell material. (6) Second hydrothermal reaction: The above-obtained materials and biochar are mixed and dispersed in deionized water at a mass ratio of 1:2-1:5, ultrasonicated and stirred until uniformly mixed to form a suspension. The suspension is transferred to a reaction vessel and reacted at 100-150℃ for 6-15 hours. After the reaction, the solid and liquid are separated, and the solid is washed 1-3 times with deionized water and anhydrous ethanol. It is then dried at 60℃ for 6-12 hours to obtain microplastic@iron(II) oxide / manganese(II) oxide / biochar magnetic core-shell composite material.

2. The preparation method according to claim 1, characterized in that: The microplastic particles have a particle size ranging from 0.4 μm to 4 mm and are made of polyethylene (PE).

3. The preparation method according to claim 1, characterized in that: The molar ratio of ferric chloride to ferrous chloride in the iron salt is 1.5:1 to 2.5:

1.

4. The preparation method according to claim 1, characterized in that: The iron salts are ferric chloride and ferrous chloride, and the organic waste is straw, fruit shells, sawdust, branches or fallen leaves.

5. The preparation method according to claim 1, characterized in that: The concentration of ammonia in step (4) is 10-25%.

6. The preparation method according to claim 1, characterized in that: The solid-liquid separation is performed by vacuum filtration or centrifugation.

7. The microplastic@iron tetroxide / manganese dioxide / biochar magnetic core-shell composite material prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the microplastic@iron tetroxide / manganese dioxide / biochar magnetic core-shell composite material according to claim 7 in environmental remediation fields such as wastewater treatment.

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