Microplastic degrading agents in water, their preparation methods and applications

Abstract

This invention discloses a microplastic degrading agent for use in water, its preparation method, and its application. The general formula of this microplastic degrading agent is Fe. a Gd b Mn c O x Where a, b, and c represent the atomic ratios of Fe, Gd, and Mn, respectively, with a:b:c = 1:(0.15–0.75):(0.33–0.96), preferably a:b:c = 1:(0.42–0.57):(0.53–0.75), and x is the total number of oxygen atoms required to satisfy the valence of other elements. The degrading agent of this invention can dynamically oxidize and degrade microplastics in water, achieving a good degradation rate.

Description

Technical Field

[0001] This invention belongs to the field of microplastic degradation technology, specifically relating to a microplastic degrading agent in water, its preparation method, and its application. Background Technology

[0002] Plastics, as a type of malleable material made primarily of resin, and its products, are widely used in daily life. When plastics decompose in terrestrial and aquatic environments, they ultimately become countless tiny plastic particles. Particles smaller than 5 mm are defined as microplastics. Microplastics are characterized by their small particle size, large specific surface area, strong hydrophobicity, and ease of adhering to pollutants, thus possessing a strong ability to accumulate heavy metals and organic pollutants. Furthermore, plastics themselves may contain toxic substances, such as polymer monomers, plasticizers, flame retardants, and antioxidants, which are gradually released into water bodies, causing persistent pollution. In addition, the small particle size of microplastics allows them to migrate long distances in the aquatic environment, and the heavy metals and organic pollutants adsorbed by microplastics also migrate long distances, further aggravating the pollution of complex pollutants and significantly increasing the area of ​​pollution.

[0003] Given the persistent polluting nature of microplastics, an increasing number of researchers are focusing on developing technologies and methods for removing microplastics from water bodies. Fenton oxidation degradation, aligned with current green chemistry principles, can mineralize organic pollutants into environmentally friendly carbon dioxide and water in the presence of hydrogen peroxide, representing a novel and environmentally friendly green degradation process.

[0004] CN106673169A discloses a method for inorganic ion-promoted degradation of organic pollutants by iron oxide. The method involves adding 0.5g–2g sodium bisulfite and 0.3g–1g ferric oxide to 1L of organic wastewater to be treated, stirring for 40–55 minutes, and allowing precipitation and separation to remove organic matter from the wastewater. While this method is characterized by rapid removal of organic matter from water, it still suffers from limitations in oxidation capacity and is limited to static degradation of organic pollutants.

[0005] CN111825241A discloses a method for treating microplastic pollutants based on micro-nano motor materials. The method includes: adding micro-nano motor materials to wastewater to be treated, then adding hydrogen peroxide to the wastewater to start the treatment process. The micro-nano motor materials undergo a catalytic reaction in the water to be treated, continuously generating micro-nano bubbles, which drive pollutants in the water to float to the surface and accumulate in the bubble foam phase. Then, the foam phase is separated from the wastewater to achieve the purpose of treating microplastic pollutants. The outer diameter of the micro-nano bubbles is 20 nm to 5000 μm. This method utilizes the self-driven motion and self-stirring ability of micro-nano motors to generate microbubbles at high speed, achieving the adsorption-bubble separation process of suspended pollutants in water. However, this method separates microplastics from wastewater through bubble adsorption and then treats the microplastics. It cannot directly degrade plastics in water. Furthermore, it uses iron oxide powder as the base material and grows manganese dioxide through hydrothermal methods. The bonding force between the two is weak, meaning the loading of manganese dioxide as a catalyst component is limited, and it is prone to detachment after long-term use. At the same time, there is also a significant loss of iron oxide base material, meaning the lifespan of the degradation agent is limited. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a microplastic degrading agent for water, its preparation method, and its application. The degrading agent provided by this invention possesses a large specific surface area, high asymmetry, and catalytic activity. In the presence of hydrogen peroxide, it can dynamically oxidize and degrade microplastics in water, achieving a good degradation rate.

[0007] The first aspect of this invention provides a microplastic degrading agent for water bodies, having the general formula Fe. a Gd b Mn c O x Where a, b, and c represent the atomic ratios of Fe, Gd, and Mn, respectively, and a:b:c = 1:(0.15~0.75):(0.33~0.96), preferably a:b:c = 1:(0.42~0.57):(0.53~0.75), and x is the total number of oxygen atoms required to satisfy the valence of other elements.

[0008] Furthermore, most of the metal components exist in the γ-crystalline form.

[0009] Furthermore, the specific surface area of ​​the degradation agent is 80 m². 2 / g~95m 2 / g, pore volume is 0.63cm³ 3 / g~0.79cm 3 / g.

[0010] Furthermore, the degrading agent exhibits asymmetry. Asymmetry specifically refers to the geometric morphology / shape of the degrading agent, such as an asymmetric structure resembling a blocky or polygonal shape. Degrading agents with asymmetric structures resembling blocks or polygons exhibit higher mobility when driven by bubbles.

[0011] A second aspect of the present invention provides a method for preparing the above-mentioned microplastic degrading agent in water, comprising the following steps:

[0012] (1) Prepare a mixed metal salt solution containing iron precursor and gadolinium precursor, and then carry out a precipitation reaction with sodium hydroxide solution;

[0013] (2) The mixture after the precipitation reaction in step (1) is subjected to solid-liquid separation and calcined to obtain the degradation agent carrier;

[0014] (3) Dissolve potassium permanganate in water, add acid solution dropwise, stir to react, then add the degradation agent carrier obtained in step (2) and mix evenly, then perform the first heat treatment and the second heat treatment to obtain the degradation agent.

[0015] Further, the iron precursor in step (1) is selected from one or more of ferrous sulfate, ferrous chloride and ferrous nitrate, preferably ferrous sulfate; the gadolinium precursor is selected from one or more of gadolinium chloride, gadolinium sulfate and gadolinium nitrate, preferably gadolinium nitrate.

[0016] Further, the concentration of the mixed metal salt solution in step (1) is 0.2 mol / L to 1 mol / L, preferably 0.4 mol / L to 0.7 mol / L.

[0017] Further, the molar ratio of the iron precursor and the gadolinium precursor in step (1) is 1:(0.05~0.5) based on the metal elements, preferably 1:(0.1~0.3).

[0018] Further, the mass ratio of the mixed metal salt solution to the sodium hydroxide solution in step (1) is 1:(0.5-3.5), preferably 1:(1.5-2.5).

[0019] Further, the concentration of the sodium hydroxide solution in step (1) is 0.5 mol / L to 2.5 mol / L, preferably 0.8 mol / L to 1.2 mol / L.

[0020] Furthermore, the solvent water in the mixed metal salt solution and sodium hydroxide solution in step (1) is selected from one or more of deionized water, distilled water, and purified water, with deionized water being preferred.

[0021] Further, the precipitation reaction temperature in step (1) is 30℃~90℃, preferably 50℃~70℃, and the precipitation reaction time is 1h~8h, preferably 3h~6h.

[0022] Furthermore, after solid-liquid separation in step (2), the mixture is first washed, dried, and then calcined. The solid-liquid separation and washing can be carried out using conventional methods in the art, such as using vacuum filtration for solid-liquid separation and repeatedly rinsing with deionized water for washing.

[0023] Further, the drying temperature in step (2) is 80℃~150℃, preferably 105℃~130℃, and the drying time is 12h~48h, preferably 18h~36h.

[0024] Further, the roasting temperature in step (2) is 300℃~600℃, preferably 400℃~500℃, and the roasting time is 1h~8h, preferably 3h~6h.

[0025] Further, in step (3), potassium permanganate is preferably dissolved in water at room temperature. The room temperature is 20°C to 30°C. The water is preferably deionized water.

[0026] Further, the acid solution in step (3) is selected from one or more of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution, preferably hydrochloric acid solution. The mass concentration of the acid solution is 30% to 40%.

[0027] Furthermore, the stirring speed during the acid solution addition process in step (3) is 300 rpm to 500 rpm, and the stirring time is 10 min to 25 min.

[0028] Furthermore, the mixing in step (3) is carried out by stirring.

[0029] Further, the mass ratio of potassium permanganate, water, degradation agent carrier and acid solution in step (3) is 1:(45-90):(0.36-0.97):(0.85-3.42), preferably 1:(57-76):(0.45-0.69):(1.05-2.31).

[0030] Further, in step (3), the first heat treatment and the second heat treatment are carried out in a reactor. The reactor is a stainless steel reactor with a polytetrafluoroethylene liner.

[0031] Further, the conditions for the first heat treatment in step (3) include: a first reaction temperature of 90℃~150℃, preferably 110℃~130℃, and a first reaction time of 0.5h~15h, preferably 4h~8h. The conditions for the second heat treatment include: a second reaction temperature of 450℃~700℃, preferably 530℃~600℃, and a second reaction time of 1h~8h, preferably 3h~6h.

[0032] Further, in step (3), after the first heat treatment, the reactants are first cooled to room temperature, then washed, dried, and then subjected to a second heat treatment. The room temperature is 20℃~30℃. The washing can be done by repeatedly rinsing with deionized water several times. The drying temperature is 25℃~100℃, preferably 50℃~70℃, and the drying time is 8h~24h, preferably 12h~16h.

[0033] Further, the product obtained after the second heat treatment in step (3) is cooled to room temperature to obtain the degradation agent. The room temperature is 20℃~30℃.

[0034] The third aspect of this invention provides the application of the above-mentioned microplastic degrading agent in water bodies in the dynamic oxidative degradation of microplastics in water bodies.

[0035] Furthermore, the application of dynamic oxidative degradation of microplastics in water includes: microplastic particles in water undergoing oxidative degradation reactions under the action of surfactants, the degradation agent, and hydrogen peroxide solution.

[0036] Furthermore, the microplastic particles are selected from at least one of low-density polyethylene plastic, polystyrene plastic, polypropylene plastic, and ultra-high molecular weight polyethylene plastic.

[0037] Furthermore, the average particle size of the microplastic particles is 0.5 mm to 2 mm.

[0038] Furthermore, the surfactant is selected from nonionic surfactants. The nonionic surfactant can be at least one of alkylphenol polyoxyethylene ethers, preferably nonylphenol polyoxyethylene ether-20.

[0039] Furthermore, the mass concentration of the hydrogen peroxide solution is 3% to 6%.

[0040] Further, the mass ratio of the microplastic particles, surfactant, degrading agent and hydrogen peroxide is 1:(0.01-0.15):(0.1-1.3):(0.05-0.5), preferably 1:(0.05-0.1):(0.4-0.8):(0.1-0.35).

[0041] Furthermore, the oxidative degradation reaction is carried out at room temperature, which is 20°C to 30°C.

[0042] Furthermore, the oxidative degradation reaction takes 25 to 55 minutes.

[0043] Furthermore, the concentration of the aqueous solution of the microplastic is 0.5 g / L to 10 g / L.

[0044] Furthermore, the degrading agent will move in water as the reaction occurs, with a movement rate of 275 μm / s to 287 μm / s.

[0045] Furthermore, the present invention conducts a simulation experiment on the dynamic oxidative degradation of microplastics in water by a microplastic degrading agent. Specifically, microplastic particles, surfactants, degrading agents, hydrogen peroxide solution and deionized water are mixed and a degradation reaction is carried out.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] (1) The two active metal components, iron and gadolinium, in the degradation agent of the present invention firmly form a carrier, and the gadolinium component is uniformly dispersed under the synergistic effect of the iron component. Moreover, most of the iron and gadolinium components in the degradation agent of the present invention exist in the γ-crystalline form, which can obtain a large specific surface area, creating opportunities for hydrogen peroxide to be adsorbed and decomposed on its surface; it can also inhibit the conversion of ferrous ions to ferric ions, improve the catalytic reaction activity of the degradation agent, and rapidly drive the degradation agent to treat microplastics in water; in addition, manganese dioxide is deposited on the carrier, and most of the manganese dioxide exists in the γ-crystalline form, which is beneficial to improving the catalytic reaction activity of the degradation agent and promoting the decomposition of hydrogen peroxide.

[0048] (2) The method of this invention uses a chemical precipitation reaction to prepare the degradation agent carrier, which can firmly fix the two active metal components, iron and gadolinium, in the carrier, reducing loss. Moreover, under the synergistic effect of the iron component, it is beneficial to uniformly disperse the gadolinium component. Potassium permanganate decomposes upon heating and is deposited on the degradation agent carrier in the form of manganese dioxide. In addition, after two stages of heating treatment, most of the iron, gadolinium, and manganese dioxide components in the degradation agent carrier exist in the γ-crystal form in the degradation agent carrier, which is beneficial to improving the catalytic activity of the degradation agent and promoting the decomposition of hydrogen peroxide. This invention decomposes hydrogen peroxide through the catalytic reaction of the degradation agent, generating a large number of hydroxyl radicals on the one hand, which degrade microplastics in water. On the other hand, the generated oxygen acts as a driving source, causing the degradation agent to move freely in the water. That is, the degradation process can be completed automatically without external stirring or shaking.

[0049] (3) When treating microplastics in water, the method of the present invention adds a small amount of nonionic surfactant, which helps to suppress the amount of foam generated during the hydrogen peroxide decomposition stage and at the same time plays a role in enriching microplastics, thereby increasing the removal rate of microplastics.

[0050] (4) The operation method of the present invention is simple and highly controllable, and the reaction process is safe and environmentally friendly, making it suitable for industrial-scale batch treatment of microplastics in water. Attached Figure Description

[0051] Figure 1 Scanning electron microscope and energy dispersive spectroscopy (SEM-EDX) images of the degradation agent prepared in Example 1;

[0052] Figure 2 This is a comparison chart of the removal rates of different microplastics in Example 1;

[0053] Figure 3 X-ray diffraction (XRD) pattern of the degradation agent prepared in Example 1;

[0054] Figure 4 X-ray diffraction (XRD) pattern of the degradation agent prepared in Comparative Example 3;

[0055] Figure 5 Scanning electron microscopy of the degradation agent prepared in Comparative Example 3. Detailed Implementation

[0056] The present invention will be further described in detail below through embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0057] Unless otherwise specified, the experimental methods used in the following examples are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0058] In this invention, the morphology, particle size, and surface elemental composition of the prepared degradation agent were observed using a Japanese Hitachi S-4700 field emission scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX).

[0059] In this invention, the characteristic diffraction peaks of the degrading agent were determined using a Rigaku D / max-IIIC fully automated X-ray diffractometer (XRD) from Japan. Test conditions: CuKa radiation, tube voltage 40 kV, scan rate 2 degrees / minute.

[0060] In this invention, the content of each metal in the degradation agent is quantitatively analyzed using an XDL 230 X-ray fluorescence spectrometer (XRF) manufactured by Fischer GmbH, Germany.

[0061] In this invention, the specific surface area and pore volume of the degradation agent were determined using a 3H-2000PM2 specific surface area analyzer manufactured by Beijing Bestech Co., Ltd. Before testing, the samples underwent vacuum degassing at 373K, and nitrogen adsorption-desorption isotherms were tested at 77K. The specific surface area and pore volume of the samples were analyzed using the BET method.

[0062] The removal rate of microplastics in water is calculated as follows: (Weight of degrading agent + Weight of microplastics) - Weight of dried product after degradation] / (Weight of degrading agent + Weight of microplastics) × 100%.

[0063] Example 1

[0064] 69.46 g of ferrous sulfate and 37.43 g of gadolinium nitrate hexahydrate were dissolved in 1 L of deionized water. 48 g of sodium hydroxide was then dissolved in another 1 L of deionized water. After complete dissolution, 500 g of the sodium hydroxide solution was added to 250 g of a mixed metal salt solution at 60 °C, and the precipitation reaction was allowed to proceed for 4 hours. The resulting mixture was filtered, repeatedly washed with deionized water, and the filter cake was transferred to an oven for drying at 120 °C for 24 hours. The cake was then calcined at 450 °C for 4 hours to obtain the degradation agent carrier. At 25 °C, 10 g of potassium permanganate was dissolved in 686.2 g of deionized water, and 13.7 g of a 35% hydrochloric acid solution was added dropwise. The mixture was stirred at 400 rpm for 15 minutes, and then 5.8 g of the degradation agent carrier was added and stirred until homogeneous. The mixture was then placed in a reaction vessel and heated at 120 °C for 6 hours. After heat treatment, the mixture in the reactor was cooled to 25°C, repeatedly rinsed with deionized water, transferred to a drying oven, and dried at 60°C for 14 hours. The dried product was then further heat-treated at 550°C for 4 hours. The resulting product was cooled to 25°C to obtain the degradation agent. The morphology, particle size, and surface elemental composition of the degradation agent were observed using a Hitachi S-4700 field emission scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX) system. Figure 1 As shown; the characteristic diffraction peaks of the degrading agent were determined using a Rigaku D / max-IIIC fully automated X-ray diffractometer (XRD) from Japan. The test conditions were: CuKa radiation, tube voltage 40 kV, and scanning speed 2 degrees / minute. Figure 3 As shown.

[0065] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.52:0.65.

[0066] Weigh 5g of polypropylene plastic with an average particle size of 1mm, 0.4g of nonylphenol polyoxyethylene ether-20, 3g of degradation agent, 1000g of deionized water and 1g of hydrogen peroxide with a mass concentration of 5%, place them in a beaker, and carry out an oxidative degradation reaction at 25℃ for 40min.

[0067] Example 2

[0068] 67.95g of ferrous sulfate and 20.29g of gadolinium nitrate hexahydrate were dissolved in 1L of deionized water. Then, 32g of sodium hydroxide was dissolved in another 1L of deionized water. After complete dissolution, 500g of the sodium hydroxide solution was added to 333.33g of a mixed metal salt solution at 50℃, and the precipitation reaction was allowed to proceed for 3 hours. The resulting mixture was filtered and repeatedly washed with deionized water. The filter cake was transferred to an oven for drying at 105℃ for 18 hours, followed by calcination at 400℃ for 3 hours to obtain the degradation agent carrier. At 20℃, 10g of potassium permanganate was dissolved in 570g of deionized water, and 10.5g of a 35% hydrochloric acid solution was added dropwise. The mixture was stirred at 300rpm for 10 minutes, then 4.5g of the degradation agent carrier was added and stirred until homogeneous. The mixture was placed in a reaction vessel and heated at 110℃ for 4 hours. After heat treatment, the mixture in the reactor was cooled to 20°C, repeatedly rinsed with deionized water, transferred to a drying oven, and dried at 50°C for 12 hours. The dried product was then further heat-treated at 530°C for 3 hours, and the resulting product was cooled to 20°C to obtain the degradation agent.

[0069] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.46:0.59.

[0070] Weigh 5g of polypropylene plastic with an average particle size of 1mm, 0.25g of nonylphenol polyoxyethylene ether-20, 2g of degradation agent, 875g of deionized water and 0.5g of hydrogen peroxide with a mass concentration of 5%, place them in a beaker, and carry out an oxidative degradation reaction at 20℃ for 40min.

[0071] Example 3

[0072] 57.38 g of ferrous sulfate and 51.86 g of gadolinium nitrate hexahydrate were dissolved in 1 L of deionized water. 40 g of sodium hydroxide was then dissolved in another 1 L of deionized water. After complete dissolution, 500 g of the sodium hydroxide solution was added to 200 g of a mixed metal salt solution at 70 °C, and the precipitation reaction was allowed to proceed for 4 hours. The resulting mixture was filtered and repeatedly washed with deionized water. The filter cake was transferred to an oven for drying at 130 °C for 36 hours, followed by high-temperature calcination at 500 °C for 6 hours to obtain the degradation agent carrier. At 30 °C, 10 g of potassium permanganate was dissolved in 760 g of deionized water. 23.1 g of a 35% hydrochloric acid solution was added dropwise, and the mixture was stirred at 500 rpm for 25 minutes. Then, 6.9 g of the degradation agent carrier was added, and the mixture was stirred until homogeneous at the same speed. The mixture was placed in a reaction vessel and heated at 130 °C for 8 hours. After heat treatment, the mixture in the reactor was cooled to 30°C, repeatedly rinsed with deionized water, transferred to a drying oven, and dried at 70°C for 16 hours. The dried product was then further heat-treated at 600°C for 6 hours, and the resulting product was cooled to 30°C to obtain the degradation agent.

[0073] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.57:0.7.

[0074] Weigh 5g of polypropylene plastic with an average particle size of 1mm, 0.5g of nonylphenol polyoxyethylene ether-20, 4g of degradation agent, 1275g of deionized water and 1.75g ​​of hydrogen peroxide with a mass concentration of 5%, place them in a beaker, and carry out an oxidative degradation reaction at 30℃ for 40min.

[0075] Example 4

[0076] Same as Example 1, except that gadolinium chloride hexahydrate is used instead of gadolinium nitrate hexahydrate in the preparation of the degradation agent.

[0077] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.48:0.59.

[0078] Example 5

[0079] Same as Example 1, except that sulfuric acid solution of the same concentration is used instead of hydrochloric acid solution in the preparation of the degradation agent.

[0080] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.5:0.6.

[0081] Example 6

[0082] Same as Example 1, except that during the preparation of the degradation agent, the first heating reaction temperature is increased to 150°C in the mixing stage of potassium permanganate and degradation agent carrier.

[0083] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.5:0.68.

[0084] Example 7

[0085] Same as Example 1, except that during the preparation of the degradation agent, after the first heat treatment, the drying temperature is reduced to 30°C and the time is extended to 24 hours during the mixing stage of potassium permanganate and degradation agent carrier.

[0086] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.49:0.67.

[0087] Example 8

[0088] Same as Example 1, except that the second reaction temperature is increased to 700°C during the preparation of the degradation agent.

[0089] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.53:0.7.

[0090] Example 9

[0091] Same as Example 1, except that the mass of gadolinium nitrate hexahydrate and potassium permanganate was increased to 93.35g and 15g respectively during the preparation of the degradation agent.

[0092] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.34:0.83.

[0093] Example 10

[0094] Same as Example 1, except that octylphenol polyoxyethylene ether-10 is used instead of nonylphenol polyoxyethylene ether-20 in the degradation process.

[0095] Comparative Example 1

[0096] Same as Example 1, except that gadolinium nitrate hexahydrate is omitted in the preparation stage of the degradation agent carrier.

[0097] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron to manganese in the degradation agent was 1:0.32.

[0098] Comparative Example 2

[0099] Same as Example 1, except that potassium permanganate is omitted when preparing the degradation agent.

[0100] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron to gadolinium in the degradation agent was 1:0.52.

[0101] Comparative Example 3

[0102] Same as Example 1, except that in the mixing stage of potassium permanganate and the degradation agent carrier, after the drying treatment, the second heat treatment step was omitted to obtain the degradation agent. The characteristic diffraction peaks of the degradation agent were measured using a Rigaku D / max-IIIC fully automatic X-ray diffractometer (XRD) from Japan, such as... Figure 4 As shown, the test conditions were: CuKa radiation, tube voltage 40 kV, and scanning speed 2 degrees / minute. The morphology and particle size of the prepared degradation agent were observed using a Hitachi S-4700 field emission scanning electron microscope (SEM) and energy dispersive spectroscopy (EDX) instrument. Figure 5 As shown.

[0103] Quantitative analysis using X-ray fluorescence spectrometry revealed that the molar ratio of iron, gadolinium, and manganese in the degradation agent was 1:0.38:0.31.

[0104] Comparative Example 4

[0105] Same as Example 1, except that an anionic surfactant sodium dodecyl sulfate is used instead of nonylphenol polyoxyethylene ether-20 to complete the microplastic degradation process in water.

[0106] Test Example 1

[0107] The physicochemical properties of the degrading agents in Examples 1-10 and Comparative Examples 1-4 and the removal rate of microplastics in water were determined. The specific results are shown in Table 1.

[0108] Table 1. Physicochemical properties and microplastic removal rates of the degradation agents prepared in the examples and comparative examples.

[0109]

[0110] As shown in Table 1, the degradation agent prepared by the method of this invention has a high BET specific surface area and pore volume. Figure 1 As can be seen, the degradation agent prepared by the method of this invention has a block structure. Energy dispersive spectroscopy analysis revealed that the main active metal components, iron, gadolinium, and manganese, are all present, indicating that the degradation agent has a complete catalytic oxidation reaction component. Meanwhile, from Figure 3It can be seen that the XRD pattern of the sample from Example 1 shows obvious characteristic diffraction peaks near 30°, 35°, and 40°, which are the main diffraction peak positions of the metallic γ-crystalline structure. However, the XRD pattern of Comparative Example 3 does not show clear γ-crystalline peaks, indicating that an effective heat treatment method is one of the necessary means to obtain the specified crystalline structure. The BET specific surface area and pore volume of the sample from Example 1 reach 95 m². 2 / g and 0.79cm 3 The mobile rate and microplastic removal rate of the sample in water were 287 μm / s and 95%, respectively, while the mobile rate and microplastic removal rate of the comparative sample in water were significantly lower than these values. This is because the method of the present invention decomposes hydrogen peroxide through the catalytic reaction of the degrading agent, generating a large number of hydroxyl radicals that degrade microplastics in water. On the other hand, the generated oxygen acts as a driving source, promoting the rapid movement of the degrading agent in water.

[0111] Test Example 2

[0112] Using the degradation agent prepared in Example 1, under the operating conditions of Example 1, tests were conducted by sequentially replacing the polypropylene plastic in Example 1 with low-density polyethylene plastic, polystyrene plastic, and ultra-high molecular weight polyethylene plastic.

[0113] Based on the above calculation formula, the degradation rates of low-density polyethylene plastic, polystyrene plastic, and ultra-high molecular weight polyethylene plastic after degradation by the degradation agent prepared in Example 1 were calculated respectively. Figure 2 As shown.

[0114] Depend on Figure 2 As can be seen, the method of the present invention has a good degradation effect on various types of microplastics, with a degradation rate maintained between 83% and 95%. Since several types of microplastics usually coexist in actual industrial wastewater, this indicates that the method of the present invention is suitable for industrial-scale batch treatment processes.

Claims

1. A microplastic degrading agent for water bodies, characterized in that, The general formula of the microplastic degrading agent is Fe. a Gd b Mn c O x , where a:b:c=1:(0.15~0.75):(0.33~0.96); most of the metal components exist in the γ crystal form.

2. The microplastic degrading agent according to claim 1, characterized in that a:b:c = 1:(0.42~0.57):(0.53~0.75).

3. The microplastic degrading agent according to claim 1, characterized in that, The specific surface area of ​​the degradation agent is 80 m². 2 / g~95m 2 / g, pore volume is 0.63cm³ 3 / g~0.79cm 3 / g.

4. A method for preparing the microplastic degrading agent according to any one of claims 1 to 3, comprising the following steps: (1) Prepare a mixed metal salt solution containing iron precursor and gadolinium precursor, and then carry out a precipitation reaction with sodium hydroxide solution; (2) The mixture after precipitation reaction in step (1) is subjected to solid-liquid separation and calcination to obtain the degradation agent carrier; (3) Dissolve potassium permanganate in water, add acid solution drop by drop, stir to react, then add the degradation agent carrier obtained in step (2) and mix evenly, then perform the first heat treatment and the second heat treatment to obtain the degradation agent.

5. The preparation method according to claim 4, characterized in that, The iron precursor in step (1) is selected from one or more of ferrous sulfate, ferrous chloride and ferrous nitrate; the gadolinium precursor is selected from one or more of gadolinium chloride, gadolinium sulfate and gadolinium nitrate.

6. The preparation method according to claim 5, characterized in that, The iron precursor in step (1) is ferrous sulfate; the gadolinium precursor is gadolinium nitrate.

7. The preparation method according to claim 4, characterized in that, The concentration of the mixed metal salt solution in step (1) is 0.2 mol / L to 1 mol / L.

8. The preparation method according to claim 7, characterized in that, The concentration of the mixed metal salt solution in step (1) is 0.4 mol / L to 0.7 mol / L.

9. The preparation method according to claim 4, characterized in that, The molar ratio of the iron precursor and the gadolinium precursor in step (1), based on the metal element, is 1:(0.05~0.5).

10. The preparation method according to claim 9, characterized in that, The molar ratio of the iron precursor and the gadolinium precursor in step (1) is 1:(0.1~0.3) based on the metal elements.

11. The preparation method according to claim 4, characterized in that, The mass ratio of the mixed metal salt solution to the sodium hydroxide solution in step (1) is 1:(0.5~3.5).

12. The preparation method according to claim 10, characterized in that, The mass ratio of the mixed metal salt solution to the sodium hydroxide solution in step (1) is 1:(1.5~2.5).

13. The preparation method according to claim 4, characterized in that, The concentration of the sodium hydroxide solution in step (1) is 0.5 mol / L to 2.5 mol / L.

14. The preparation method according to claim 13, characterized in that, The concentration of the sodium hydroxide solution in step (1) is 0.8 mol / L to 1.2 mol / L.

15. The preparation method according to claim 4, characterized in that, The precipitation reaction temperature in step (1) is 30℃~90℃, and the precipitation reaction time is 1h~8h.

16. The preparation method according to claim 4, characterized in that, The roasting temperature in step (2) is 300℃~600℃, and the roasting time is 1h~8h.

17. The preparation method according to claim 16, characterized in that, The roasting temperature in step (2) is 400℃~500℃, and the roasting time is 3h~6h.

18. The preparation method according to claim 4, characterized in that, The acid solution in step (3) is selected from one or more of hydrochloric acid solution, nitric acid solution and sulfuric acid solution; and / or the mass concentration of the acid solution is 30%~40%.

19. The preparation method according to claim 4, characterized in that, The mass ratio of potassium permanganate, water, degradation agent carrier and acid solution in step (3) is 1: (45~90): (0.36~0.97): (0.85~3.42).

20. The preparation method according to claim 19, characterized in that, The mass ratio of potassium permanganate, water, degradation agent carrier and acid solution in step (3) is 1: (57~76): (0.45~0.69): (1.05~2.31).

21. The preparation method according to claim 4, characterized in that, The conditions for the first heat treatment in step (3) include: a first reaction temperature of 90℃~150℃ and a first reaction time of 0.5h~15h; and / or, the conditions for the second heat treatment include: a second reaction temperature of 450℃~700℃ and a second reaction time of 1h~8h.

22. The preparation method according to claim 21, characterized in that, The conditions for the first heat treatment in step (3) include: a first reaction temperature of 110℃~130℃ and a first reaction time of 4h~8h; and / or, the conditions for the second heat treatment include: a second reaction temperature of 530℃~600℃ and a second reaction time of 3h~6h.

23. The preparation method according to claim 4, characterized in that, Step (3) After the first heat treatment, the reactants are cooled to room temperature, then washed, dried, and then subjected to the second heat treatment.

24. The preparation method according to claim 23, characterized in that, The drying temperature is 25℃~100℃, and the drying time is 8h~24h.

25. The preparation method according to claim 24, characterized in that, The drying temperature is 50℃~70℃, and the drying time is 12h~16h.

26. The application of the microplastic degrading agent according to any one of claims 1 to 3 in the dynamic oxidative degradation of microplastics in water.

27. The application according to claim 26, characterized in that, The application of dynamic oxidative degradation of microplastics in water includes: microplastic particles in water undergo oxidative degradation reaction under the action of surfactants, the degradation agent and hydrogen peroxide solution.

28. The application according to claim 27, characterized in that, The microplastic particles are selected from at least one of low-density polyethylene plastic, polystyrene plastic, polypropylene plastic and ultra-high molecular weight polyethylene plastic; and / or, the average particle size of the microplastic particles is 0.5 mm to 2 mm; and / or, the mass concentration of the hydrogen peroxide solution is 3% to 6%.

29. The application according to claim 27, characterized in that, The surfactant is selected from nonionic surfactants.

30. The application according to claim 29, characterized in that, The nonionic surfactant is at least one of alkylphenol polyoxyethylene ethers.

31. The application according to claim 30, characterized in that, The nonionic surfactant is nonylphenol polyoxyethylene ether-20.

32. The application according to claim 27, characterized in that, The mass ratio of the microplastic particles, surfactant, degrading agent and hydrogen peroxide is 1:(0.01~0.15):(0.1~1.3):(0.05~0.5).

33. The application according to claim 32, characterized in that, The mass ratio of the microplastic particles, surfactant, degrading agent and hydrogen peroxide is 1:(0.05~0.1):(0.4~0.8):(0.1~0.35).

34. The application according to claim 27, characterized in that, The concentration of the aqueous solution of the microplastic is 0.5 g / L to 10 g / L.

35. The application according to claim 27, characterized in that, The oxidative degradation reaction is carried out at room temperature, wherein the room temperature is 20℃~30℃, and / or the oxidative degradation reaction time is 25min~55min.

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