Preparation method of manganese-iron bimetallic oxide composite polyurethane sponge material and application thereof

Abstract

The present application relates to the technical field of environmental functional material preparation, and specifically discloses a preparation method of manganese-iron bimetallic oxide composite polyurethane sponge material and application thereof.The composite material is prepared by a three-step method of "modification-impregnation-thermal fixation", uses hydrophilic polyurethane sponge as a substrate, is modified by polyvinyl alcohol, then is loaded with manganese-iron bimetallic oxide nanoparticles, and finally is obtained by annealing thermal fixation to obtain a three-dimensional porous monolithic composite material.The present application has the advantages of simple preparation process, cheap and easily available raw materials, and suitability for large-scale production, and the obtained material has stable structure, three-dimensional through pores, good mass transfer performance and interface reaction conditions, can efficiently activate high iodate to produce active species, and can rapidly degrade various aromatic organic pollutants through the synergistic effect of adsorption enrichment and interface catalysis.The catalyst has good cycle stability, low metal leaching amount, is easy to separate and recover, is suitable for treatment of actual refractory organic wastewater, and has good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials preparation technology, specifically to a method for preparing a manganese-iron bimetallic oxide composite polyurethane sponge material; furthermore, this invention also relates to the application of this composite material in the removal of organic pollutants in advanced oxidation technologies for water treatment. Background Technology

[0002] With the continuous advancement of industrialization, aromatic organic compounds are widely used in industries such as pharmaceuticals, pesticides, dyes, and chemicals, and continuously enter the aquatic environment during production, use, and discharge, leading to a continuous increase in the types and concentrations of emerging organic pollutants. These pollutants are typically characterized by high toxicity, structural stability, and recalcitrant biodegradability, making efficient and thorough removal difficult using traditional treatment methods. Therefore, developing efficient, green, and sustainable water treatment technologies is of great significance. Advanced oxidation processes (AOPs) have attracted widespread attention in recent years due to their ability to generate highly reactive oxidizing species in situ, enabling rapid oxidative transformation and deep removal of recalcitrant organic pollutants. Among these, periodate-based AOPs have shown promising application prospects in organic pollutant removal due to their strong oxidizing power, fast reaction rate, and relatively mild operating conditions. Existing patents, such as Chinese patents CN107265606A, CN109603878A, and CN114516679A, have disclosed methods for removing organic pollutants using periodate activation, indicating that this technical route has a certain research foundation. However, existing systems still suffer from problems such as complex activation methods, reliance on external energy input in some systems, and insufficient engineering applications.

[0003] Existing research indicates that transition metal oxides such as iron, manganese, and cobalt can effectively activate periodate to generate reactive oxygen species, thereby promoting the degradation of organic pollutants. Among them, manganese-iron bimetallic oxides, due to their combination of the multivalent redox properties of manganese and iron, exhibit good synergistic catalytic effects, while also possessing advantages such as abundant resources, environmental friendliness, and low cost, making them an important research target in the field of periodate activation. Previous studies have also shown that non-radical oxidation pathways exist during periodate activation, with electron transfer and singlet oxygen processes playing crucial roles in pollutant removal. However, existing manganese-iron bimetallic oxide catalysts are mostly prepared via co-precipitation, hydrothermal methods, sol-gel methods, impregnation-calcination methods, and in-situ growth methods. The resulting products are mostly nanoparticles, which generally suffer from problems such as easy particle agglomeration, uneven dispersion of active components, difficulty in subsequent separation, and poor reusability. Although existing technologies typically employ porous supports to immobilize active components, they still lack synergistic regulation of the interfacial layer structure and electron transport channels.

[0004] Polyurethane foam is a typical three-dimensional porous material with advantages such as interconnected pores, good mechanical properties, wide availability, low cost, and ease of separation, recycling, and reuse. Its hierarchical pore structure facilitates rapid transport of reaction liquids and enhances the adsorption and enrichment of pollutants on the material surface, thus providing a favorable interfacial environment for advanced oxidation reactions. Therefore, using polyurethane foam as the integral framework to construct composite catalytic materials theoretically holds promise for achieving highly dispersed loading of active components, enhanced reaction interfaces, and integral recyclable applications.

[0005] Chinese patent CN108384049B discloses a titanium dioxide-graphene composite sponge and its preparation method, employing a route of "active component dispersion—sponge impregnation—post-treatment fixation" to construct an integral composite material; Chinese patent CN114453026B discloses MOFs sponge wastewater purification materials, their preparation method, and applications; Chinese patent CN112156789A discloses sponge iron-supported metal oxide catalysts and their preparation method. These technologies demonstrate that existing technologies recognize the necessity of using porous bulk frameworks to support active components to improve the problems of difficult separation and easy loss of powdered catalysts. However, these technologies, respectively targeting photocatalysis, potassium peroxymonosulfonate, or ozone oxidation systems, do not involve the construction of a periodate-activated integral composite material with manganese-iron bimetallic oxide as the core active center, polyvinyl alcohol as the interface layer, and polyurethane sponge as a flexible three-dimensional framework.

[0006] Furthermore, from the perspective of reaction mechanism, if the effective synergy of manganese and iron multivalent active centers can be achieved through reasonable material construction, and a stable interfacial transport channel can be constructed with the help of three-dimensional framework materials, it is expected to enhance the periodate activation process, promote the generation of non-radical active species such as singlet oxygen, and form a catalytic degradation mechanism coupled with adsorption enrichment and interfacial electron transfer, thereby further improving the system's removal efficiency, selectivity and adaptability to complex water bodies for target organic pollutants.

[0007] In summary, existing advanced oxidation technologies based on periodate still face challenges such as the easy aggregation and loss of nanocatalysts, complex material preparation, and insufficient engineering adaptability. Therefore, there is an urgent need to develop a composite material using polyurethane sponge as a carrier, employing a controllable preparation process to achieve uniform loading and firm fixation of manganese-iron bimetallic oxide nanoparticles. This composite material should possess advantages such as structural stability, uniform dispersion of active sites, simple preparation, and easy recycling, and should be able to efficiently activate periodate to remove organic pollutants, thereby meeting the needs of practical water treatment applications. Summary of the Invention

[0008] To address the problems of existing Fenton-like catalysts in periodate activation systems, such as easy agglomeration and deactivation of powders, difficulty in recycling, and potential generation of iron sludge, as well as the defects of some heterogeneous catalysts such as low activation efficiency and significant metal loss, this invention proposes a manganese-iron bimetallic oxide composite polyurethane sponge material and its preparation method, and applies it to the treatment of organic wastewater by activating periodate.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a manganese-iron bimetallic oxide composite polyurethane sponge material is characterized by employing a three-step method of "modification-impregnation-heat fixation" to load manganese-iron bimetallic oxide nanoparticles onto a polyvinyl alcohol-modified polyurethane sponge, thereby obtaining a blocky integral composite material with structural stability, three-dimensional porosity, and self-supporting characteristics. The composite material mainly consists of the manganese-iron bimetallic oxide active component, a polyvinyl alcohol interface layer, and a polyurethane sponge substrate.

[0010] The preparation method specifically includes the following steps: (1) Pretreatment of polyurethane sponge: The commercial polyurethane sponge block was washed three times with ultrapure water and anhydrous ethanol to remove surface impurities, and then dried in an oven at 60-80℃ for 6-12 hours for later use. (2) Polyvinyl alcohol modified sponge: The polyurethane sponge treated in step (1) is immersed in a polyvinyl alcohol aqueous solution with a mass fraction of 2-2.5wt% and immersed at 90-95℃ for 20-40 min. After being taken out, it is dried at 60-80℃ for 6-12 h to obtain polyvinyl alcohol modified polyurethane sponge. (3) Preparation of manganese-iron bimetallic oxide nanoparticle suspension: Manganese chloride tetrahydrate and polyvinylpyrrolidone were dissolved in ultrapure water, and potassium ferricyanide was dissolved in ultrapure water and rapidly injected into the above solution. The reaction was carried out under vigorous stirring for 20-40 min. After the reaction, the mixture was allowed to stand for 20-24 h, the precipitate was collected by centrifugation, washed alternately with ultrapure water and anhydrous ethanol, dried at 60-80℃ for 6-12 h, and then calcined in a muffle furnace at 300-500℃ for 3-3.2 h in air atmosphere at a heating rate of 5℃ / min to obtain manganese-iron bimetallic oxide nanoparticles. The manganese-iron bimetallic oxide nanoparticles were ultrasonically dispersed in ultrapure water to prepare a suspension with a concentration of 10-20 mg / mL. (4) Preparation of manganese-iron bimetallic oxide composite polyurethane sponge material: The polyvinyl alcohol modified polyurethane sponge obtained in step (2) is immersed in the suspension obtained in step (3) for 30-60 min to allow it to fully adsorb nanoparticles; after taking it out, it is dried at 60-80℃ for 6-12 h, and then annealed at 100-120℃ in air atmosphere for 2-2.5 h to obtain manganese-iron bimetallic oxide composite polyurethane sponge material.

[0011] Preferably, in step (3), the amount of raw materials used to prepare manganese-iron bimetallic oxide nanoparticles is: 2.8-3.2 mmol of manganese chloride tetrahydrate corresponds to 10-12 g of polyvinylpyrrolidone and 5.8-6.2 mmol of potassium ferricyanide, and the resulting manganese-iron bimetallic oxide nanoparticles are MnFeO nanoparticles.

[0012] The present invention also provides a manganese-iron bimetallic oxide composite polyurethane sponge material prepared by the above method.

[0013] This invention further provides the application of the aforementioned manganese-iron bimetallic oxide composite polyurethane sponge material in advanced oxidation reaction systems. The material can be used as a catalyst to activate periodate and construct an organic pollutant degradation system.

[0014] The application method includes the following steps: adding periodate and the manganese-iron bimetallic oxide composite polyurethane sponge material to the solution of organic pollutants to be treated, and stirring the mixture at room temperature to achieve the degradation of organic pollutants. The manganese-iron bimetallic oxide composite polyurethane sponge material can be directly removed and reused after the reaction.

[0015] The manganese-iron bimetallic oxide composite polyurethane sponge material of the present invention is suitable for the catalytic degradation of a variety of organic pollutants, including but not limited to at least one of 2,4,6-trichlorophenol, bisphenol A and 2,4-dichlorophenol.

[0016] Preferably, the concentration of the organic pollutant is 1–100 mg / L, and the ratio of the organic pollutant to periodate is 1–100 mg: 1 mmol.

[0017] Compared with the prior art, the beneficial effects of the present invention are reflected in: 1. This invention is innovative in the preparation of active components. Using manganese chloride tetrahydrate and potassium ferricyanide as precursors, manganese-iron bimetallic oxide nanoparticles are prepared with the assistance of polyvinylpyrrolidone through steps including rapid injection, vigorous stirring, static aging, washing and drying, and calcination in air. This method facilitates the uniform composite of manganese and iron components at the nanoscale, reduces component separation and particle agglomeration, and improves the dispersibility, structural stability, and exposure of active sites of the active components, providing a stable foundation for the subsequent construction of highly efficient composite catalytic materials.

[0018] 2. This invention employs a "modification-impregnation-heat-fixation" method to construct an integral composite material. Using polyurethane sponge as a three-dimensional porous framework and polyvinyl alcohol as an interfacial adhesive layer, manganese-iron bimetallic oxide nanoparticles are firmly loaded onto the surface of the polyurethane sponge framework. Heat-fixation further enhances the bonding strength, ultimately resulting in a blocky integral material with three-dimensional interconnected channels and self-supporting capabilities. This structure facilitates sufficient contact and rapid mass transfer between pollutants, periodate, and active sites, while effectively overcoming the problems of easy agglomeration, difficulty in separation, and difficulty in recovery associated with traditional powder catalysts.

[0019] 3. This invention is innovative in its catalytic mechanism. The multivalent active centers of manganese and iron can form a highly efficient redox cycle system and interfacial electron transfer network, promoting the continuous activation of periodate and the stable generation of active species. Compared with traditional oxidation systems that mainly rely on short-lived free radicals, the system of this invention is mainly characterized by a non-radical reaction pathway dominated by singlet oxygen, exhibiting higher reaction selectivity and stronger background interference resistance. Simultaneously, the polyurethane sponge framework also has certain adsorption and enrichment effects, forming a synergistic mechanism of "adsorption-enrichment-electron transfer-degradation," thereby improving the overall removal efficiency.

[0020] 4. The system of this invention exhibits good selective removal capability for target pollutants and has a wide range of applications. Because the singlet oxygen-dominated non-radical pathway and the interfacial electron transfer process work synergistically, it is more conducive to the targeted and efficient removal of target organic pollutants and reduces interference from background substances such as coexisting inorganic anions and natural organic matter. Results show that the material of this invention can efficiently remove various aromatic organic pollutants such as dichlorophenol, bisphenol, and trichlorophenol, demonstrating good selective removal capability and a wide range of applicable pollutants.

[0021] 5. The preparation process of this invention is green, economical, and practical, and the material exhibits good stability and promising prospects for industrial application. The raw materials used, such as polyurethane foam, manganese salts, iron salts, polyvinyl alcohol, and polyvinylpyrrolidone, are widely available and moderately priced. The preparation process mainly includes conventional operations such as cleaning, impregnation, drying, heat treatment, aging, and calcination, requiring no complex equipment and facilitating large-scale production. Results show that the material maintains high degradation efficiency after repeated use, with low leaching of iron and manganese ions, effectively reducing the risk of secondary pollution. Furthermore, it can operate stably in a continuous flow fixed-bed reactor, demonstrating good engineering scale-up potential. Attached Figure Description

[0022] Figure 1 The image shows a scanning electron microscope image of the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1. Figure 1 (a) and Figure 1 (b) Morphological images at different magnifications, Figure 1 The illustration in (b) is a partial topographic view at a higher magnification.

[0023] Figure 2 This is an energy dispersive spectroscopy (EDS) elemental surface scan of the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1.

[0024] Figure 3 The images shown are scanning transmission electron microscope (STEM) images and elemental mapping diagrams of the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1. Figure 3 (a) is a scanning transmission electron microscope image. Figure 3 (b) ~ Figure 3 (f) are the elemental mapping diagrams for O, C, Mn, Fe and N, respectively.

[0025] Figure 4 The figure shows the results of a cyclic repeat experiment on the degradation of 2,4,6-trichlorophenol by the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1.

[0026] Figure 5 The graph shows a comparison of the catalytic degradation performance of 2,4,6-trichlorophenol by different metal oxide composite polyurethane sponge catalytic systems prepared in Examples 1-5.

[0027] Figure 6 The graph shows the chemical oxygen demand removal rate of the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1 during the degradation of 2,4,6-trichlorophenol.

[0028] Figure 7 The image shows the inductively coupled plasma mass spectrometry (ICP-MS) results of the leaching of metal ions in the solution after the reaction of the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1.

[0029] Figure 8 This is a comparison diagram of the specific surface area of ​​the manganese-iron bimetallic oxide composite polyurethane sponge material prepared in Example 1 and the comparative material. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or modifications made by those skilled in the art without departing from the concept of the present invention should fall within the scope of protection of the present invention.

[0031] Example 1 (I) Preparation of manganese-iron bimetallic oxide composite polyurethane sponge material (1) Pretreatment of polyurethane foam A commercially available polyurethane sponge measuring 2 cm × 2 cm × 2 cm was alternately immersed in sufficient amounts of ultrapure water and anhydrous ethanol for cleaning. Dust and organic impurities from the surface and internal pores were removed by repeated, gentle squeezing. This alternating cleaning process with ultrapure water and anhydrous ethanol was repeated three times. After cleaning, most of the liquid was squeezed out of the sponge, and it was placed in a forced-air drying oven and dried at 60°C for 8 hours until the sponge was completely dry and regained its lightness. It was then ready for use.

[0032] (2) Polyvinyl alcohol modified sponge A 2 wt% polyvinyl alcohol aqueous solution was prepared and stirred at 95°C until the polyvinyl alcohol was completely dissolved. Then, the dried sponge block obtained in step (1) was completely immersed in the polyvinyl alcohol solution preheated to 95°C and soaked at 95°C for 30 min. After soaking, the sponge was removed, excess solution was drained, and it was placed in a forced-air drying oven and dried at 60°C for 6 h to obtain a polyvinyl alcohol-modified polyurethane sponge, denoted as PPUS.

[0033] (3) Preparation of manganese-iron bimetallic oxide nanoparticle suspension 3 mmol of manganese chloride tetrahydrate and 12.0 g of polyvinylpyrrolidone were weighed and dissolved together in 400 mL of ultrapure water to obtain solution A. Separately, 6 mmol of potassium ferricyanide was weighed and dissolved in 5 mL of ultrapure water to obtain solution B. Under continuous vigorous stirring, solution B was rapidly injected into solution A, and vigorous stirring was continued for 30 min, after which stirring was stopped, and the resulting mixture was allowed to stand for aging for 24 h. After aging, the precipitate was collected by centrifugation and washed three times each with ultrapure water and anhydrous ethanol, alternately, to remove impurity ions. The washed precipitate was dried at 60 °C for 6 h to obtain precursor powder. Finally, the precursor powder was placed in a muffle furnace and heated to 400 °C at a heating rate of 5 °C / min under air atmosphere, and calcined at 400 °C for 3 h. After furnace cooling, manganese-iron bimetallic oxide nanoparticles were obtained, denoted as MnFeO.

[0034] Weigh 80 mg of the obtained manganese-iron bimetallic oxide nanoparticles, disperse them in 5 mL of ultrapure water, and sonicate for 10 min to form a uniform suspension.

[0035] (4) Preparation of manganese-iron bimetallic oxide composite polyurethane sponge material The PPUS obtained in step (2) was completely immersed in the suspension obtained in step (3). The suspension was repeatedly and gently squeezed to circulate within the three-dimensional network of the sponge, so as to promote full contact and effective capture of the manganese-iron bimetallic oxide nanoparticles and the polyvinyl alcohol coating. After the nanoparticles were saturated with adsorption, the sponge was removed and excess liquid was drained. It was pre-dried at 60°C for 2 h and then annealed at 110°C in air atmosphere for 2 h to obtain the manganese-iron bimetallic oxide composite polyurethane sponge material, denoted as MnFeO@PPUS.

[0036] (II) Degradation Experiment of Organic Pollutants A 200 mL solution of 10 mg / L 2,4,6-trichlorophenol was placed in a 500 mL beaker, along with 20 mg of periodate and a piece of MnFeO@PPUS. The reaction was carried out at 25 °C using a magnetically stirred water bath. Every 5 minutes during the reaction, 2 mL of the reaction solution was taken and the concentration of 2,4,6-trichlorophenol was determined by high-performance liquid chromatography (HPLC). The results showed that the removal rate of 2,4,6-trichlorophenol reached 99.99%.

[0037] After completing one degradation experiment, the MnFeO@PPUS was removed, rinsed with ultrapure water and dried, and the experiment was repeated in the same way to evaluate its recycling performance.

[0038] (III) Characterization and Performance Results Figure 1 This is a scanning electron microscope image of MnFeO@PPUS obtained in this embodiment. From... Figure 1 It is evident that the original three-dimensional porous structure of the polyurethane sponge was not destroyed after polyvinyl alcohol coating and MnFeO loading; the surface of the composite material pore walls showed relatively dense raised wrinkles, indicating that the MnFeO nanoparticles were uniformly loaded on the surface of the sponge skeleton.

[0039] Figure 2 This is the energy dispersive spectroscopy (EDS) elemental surface scan of MnFeO@PPUS obtained in this embodiment. From... Figure 2 It can be seen that Mn and Fe elements are relatively evenly distributed in the sponge substrate.

[0040] Figure 3 This image shows a scanning transmission electron microscope (STEM) image of MnFeO@PPUS obtained in this embodiment, along with corresponding elemental distribution maps of Mn, Fe, C, N, and O. From... Figure 3 It is evident that Mn and Fe elements are uniformly distributed with the elements in the sponge bulk, further demonstrating the uniform loading of the active components.

[0041] Figure 4 This is a graph showing the cyclic experimental results of the MnFeO@PPUS catalytic degradation of 2,4,6-trichlorophenol in this embodiment. From... Figure 4It is evident that the prepared composite material maintains a high degradation efficiency even after being reused 5 times, indicating that the material has good catalytic stability, strong adhesion of active components, and recyclability.

[0042] Example 2 The specific steps for preparing a single-metal manganese oxide composite polyurethane sponge material in this embodiment are as follows: (1) Pretreatment of polyurethane foam: Same as in Example 1.

[0043] (2) Polyvinyl alcohol modified sponge: Same as in Example 1.

[0044] (3) Preparation of manganese dioxide nanoparticle suspension 1.264 g of potassium permanganate was dissolved in 80 mL of deionized water, followed by the addition of 0.507 g of manganese sulfate monohydrate. After stirring for 30 min, the mixture was transferred to a polytetrafluoroethylene-lined stainless steel autoclave and reacted at 160 °C for 12 h. After the reaction was complete, the resulting solid was washed repeatedly with ultrapure water and dried in air at 60 °C to obtain manganese dioxide nanoparticles.

[0045] Weigh 80 mg of the obtained manganese dioxide nanoparticles, disperse them in 5 mL of ultrapure water, and sonicate for 10 min to form a uniform suspension.

[0046] (4) Preparation of single metal manganese oxide composite polyurethane sponge material: The method is the same as in Example 1, and the obtained sample is denoted as MnO2@PPUS.

[0047] Example 3 The specific steps for preparing a single-metal manganese oxide composite polyurethane sponge material in this embodiment are as follows: (1) Pretreatment of polyurethane foam: Same as in Example 1.

[0048] (2) Polyvinyl alcohol modified sponge: Same as in Example 1.

[0049] (3) Preparation of manganese tetroxide nanoparticle suspension: 1.0 g of polyvinyl alcohol and 2 mmol of manganese acetate tetrahydrate were dissolved in 100 mL of deionized water and magnetically stirred at 90 °C for 30 min. The reaction mixture was then transferred to a polytetrafluoroethylene-lined autoclave and reacted at 120 °C for 12 h. After cooling to room temperature, the precipitate was collected by filtration and washed repeatedly with water and ethanol. The resulting precipitate was dried at 80 °C for 12 h and then annealed at 600 °C for 3 h to obtain manganese tetroxide nanoparticles.

[0050] Weigh 80 mg of the obtained manganese tetroxide nanoparticles, disperse them in 5 mL of ultrapure water, and sonicate for 10 min to form a uniform suspension.

[0051] (4) Preparation of single metal manganese oxide composite polyurethane sponge material: The method is the same as in Example 1, and the obtained sample is denoted as Mn3O4@PPUS.

[0052] Example 4 The specific steps for preparing the single-metal iron oxide composite polyurethane sponge material in this embodiment are as follows: (1) Pretreatment of polyurethane foam: Same as in Example 1.

[0053] (2) Polyvinyl alcohol modified sponge: Same as in Example 1.

[0054] (3) Preparation of ferric oxide nanoparticle suspension: 6.0 g of FeCl3·6H2O was dissolved in 90 mL of deionized water, followed by the sequential addition of anhydrous sodium acetate and hexadecyltrimethylammonium bromide, with a molar ratio of FeCl3·6H2O, anhydrous sodium acetate, and hexadecyltrimethylammonium bromide of 2.7:8.9:1. Then, 21.0 mL of ethylenediamine solution was added under vigorous stirring to form a homogeneous solution. This solution was then transferred to a polytetrafluoroethylene-lined stainless steel autoclave and heated at 200 °C for 10 h. After cooling to room temperature, the resulting reddish-brown solid was washed repeatedly with deionized water and dried overnight in air at 100 °C to obtain ferric oxide nanoparticles.

[0055] Weigh 80 mg of the obtained ferric oxide nanoparticles, disperse them in 5 mL of ultrapure water, and sonicate for 10 min to form a uniform suspension.

[0056] (4) Preparation of single metal iron oxide composite polyurethane sponge material: The method is the same as in Example 1, and the obtained sample is denoted as Fe2O3@PPUS.

[0057] Example 5 The specific steps for preparing the single-metal iron oxide composite polyurethane sponge material in this embodiment are as follows: (1) Pretreatment of polyurethane foam: Same as in Example 1.

[0058] (2) Polyvinyl alcohol modified sponge: Same as in Example 1.

[0059] (3) Preparation of iron oxide nanoparticle suspension: 2.6 g FeCl3 and 0.8 g Na3Cit·2H2O were dissolved in 80 mL ethylene glycol to obtain a homogeneous solution. Then, 4.8 g sodium acetate was added under continuous stirring, and stirring was continued for 60 min. The resulting solution was transferred to a 200 mL polytetrafluoroethylene-lined stainless steel autoclave and kept at 200 °C for 12 h. After cooling, black magnetic particles were recovered by magnetic separation, washed repeatedly with methanol, and dried at 60 °C for 12 h to obtain iron(III) oxide nanoparticles.

[0060] Weigh 80 mg of the obtained iron oxide nanoparticles, disperse them in 5 mL of ultrapure water, and sonicate for 10 min to form a uniform suspension.

[0061] (4) Preparation of single metal iron oxide composite polyurethane sponge material: The method is the same as in Example 1, and the obtained sample is recorded as Fe3O4@PPUS.

[0062] Figure 5 This is a comparison chart showing the performance of different composite polyurethane sponge catalytic materials prepared in Examples 1-5 in degrading 2,4,6-trichlorophenol. From... Figure 5 It is evident that the manganese-iron bimetallic oxide composite polyurethane sponge material MnFeO@PPUS exhibits the best catalytic activity, and can almost completely degrade organic pollutants within 30 minutes.

[0063] To further evaluate the mineralization effect of the system, the chemical oxygen demand (COD) during the degradation of 2,4,6-trichlorophenol was determined. COD characterizes the content of oxidizable substances in water; a higher value indicates a higher organic matter content in the system. In this embodiment, COD was determined spectrophotometrically: 2 mL of the sample was added to a COD reagent tube with a range of 20–1500 ppm, shaken well, and placed in a COD digester. Digestion was performed at 150°C for 120 min, and after cooling to room temperature, the COD was measured using a portable COD analyzer. Figure 6 The graph shows the chemical oxygen demand (COD) removal rate during the catalytic degradation of 2,4,6-trichlorophenol using MnFeO@PPUS. Figure 6 It can be seen that the chemical oxygen demand removal rate in the system reaches 66.3% when the degradation of 2,4,6-trichlorophenol is complete.

[0064] To evaluate the metallic stability of the material, the leaching amount of metal ions in the post-reaction solution was measured. Specifically, 1 mL of the post-degradation solution was added to 9 mL of concentrated nitric acid (65%–68% by mass) and mixed well. 2 mL of the supernatant was then diluted to 10 mL, and the Mn and Fe ion contents were determined using inductively coupled plasma mass spectrometry. Figure 7 This is a graph showing the metal leaching results of the MnFeO@PPUS catalyst obtained in this embodiment. From... Figure 7 As can be seen, the leaching amount of Fe ions after the reaction was 1.234 mg / L and the leaching amount of Mn ions was 0.145 mg / L, indicating that the active components in the material are relatively stable and the degree of metal loss is low, which is beneficial to reducing the risk of secondary pollution.

[0065] Under the same conditions, the degradation performance of MnFeO@PPUS on different pollutants was further investigated. The results showed that the material could remove bisphenol A, 2,4-dichlorophenol, and 2,4,6-trichlorophenol at rates of 95%–99%, indicating that it has a good range of applicable pollutants.

[0066] In addition, the MnFeO@PPUS prepared in Example 1 and the polyvinyl alcohol-modified polyurethane sponge were subjected to BET specific surface area and pore size analysis, and the results are shown in [Figure 1]. Figure 8 The results showed that the specific surface area of ​​MnFeO@PPUS was 5.760 m² / g, lower than that of polyvinyl alcohol-modified polyurethane sponge (20.706 m² / g); its average pore size was 3.816 nm, similar to but slightly larger than that of the precursor sample (3.416 nm). These results indicate that the loading of MnFeO nanoparticles partially covered the pore surface, but the material still retained a porous structure conducive to mass transfer and interfacial reactions.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and improvements can be made to the present invention without departing from the concept of the present invention, and all such modifications and improvements should fall within the protection scope of the present invention. The protection scope of the present invention is defined by the appended claims.

Claims

1. A method for preparing a manganese-iron bimetallic oxide composite polyurethane sponge material, characterized in that, Includes the following steps: (1) Clean and dry the commercial polyurethane sponge; (2) The polyurethane sponge treated in step (1) is immersed in a polyvinyl alcohol aqueous solution and soaked at 90-95°C for 20-40 min. After being taken out and dried, polyvinyl alcohol modified polyurethane sponge is obtained. (3) Disperse manganese-iron bimetallic oxide nanoparticles in water by ultrasonication to prepare a suspension with a concentration of 10-20 mg / mL; (4) Immerse the polyvinyl alcohol modified polyurethane sponge in the suspension for 30-60 min, take it out and dry it, and then anneal it in air at 100-120°C for 2-2.5 h to obtain manganese-iron bimetallic oxide composite polyurethane sponge material.

2. The preparation method according to claim 1, characterized in that, The mass fraction of the polyvinyl alcohol aqueous solution is 2 to 2.5 wt%.

3. The preparation method according to claim 1, characterized in that, The manganese-iron bimetallic oxide nanoparticles described in step (3) are prepared by the following method: manganese chloride tetrahydrate and polyvinylpyrrolidone are dissolved in water, and potassium ferricyanide solution is rapidly injected. The reaction is carried out under vigorous stirring for 20-40 min. After the reaction is completed, the mixture is allowed to stand for aging for 20-24 h, the precipitate is collected by centrifugation, washed, dried, and then calcined at 300-500℃ for 3-3.2 h in air atmosphere to obtain manganese-iron bimetallic oxide nanoparticles.

4. The preparation method according to claim 3, characterized in that, The raw material amounts used to prepare manganese-iron bimetallic oxide nanoparticles are as follows: for every 2.8–3.2 mmol of manganese chloride tetrahydrate, there are 10–12 g of polyvinylpyrrolidone and 5.8–6.2 mmol of potassium ferricyanide. The resulting manganese-iron bimetallic oxide nanoparticles are MnFeO nanoparticles.

5. A manganese-iron bimetallic oxide composite polyurethane sponge material prepared by the preparation method described in any one of claims 1 to 4.

6. The application of the manganese-iron bimetallic oxide composite polyurethane sponge material according to claim 5 in a periodate activation system, characterized in that, The manganese-iron bimetallic oxide composite polyurethane sponge material is used as a catalyst to degrade organic pollutants.

7. The application according to claim 6, characterized in that, The periodate is potassium periodate.

8. The application according to claim 6, characterized in that, The application method includes: adding periodate and the manganese-iron bimetallic oxide composite polyurethane sponge material to the solution of organic pollutants to be treated, and stirring and reacting at room temperature to achieve the degradation of organic pollutants.

9. The application according to any one of claims 6, characterized in that, The organic pollutant is selected from at least one of 2,4,6-trichlorophenol, bisphenol A, and 2,4-dichlorophenol.

10. The application according to any one of claims 6 to 9, characterized in that, The manganese-iron bimetallic oxide composite polyurethane sponge material can be directly removed and reused after the reaction.

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