Preparation and application of melamine foam capable of adsorbing various organophosphorus flame retardants

Abstract

The invention discloses preparation and application of melamine foam capable of adsorbing various organophosphorus flame retardants. The melamine foam can adsorb and remove various organophosphorus flame retardants in environmental water at the same time. A post-modification method is adopted to obtain the polydopamine and metal organic framework double-modified melamine foam, and the foam can be directly immersed in environmental water for use. And various organophosphorus flame retardants such as aryl organophosphorus flame retardants, alkyl organophosphorus flame retardants and halogenated alkyl organophosphorus flame retardants in tap water, surface water, underground water, domestic sewage, agricultural sewage, medical wastewater or industrial sewage can be efficiently and simultaneously adsorbed and removed. And after adsorption removal is completed, taking out the wastewater from the environmental water to complete solid-liquid separation. Compared with an existing adsorbent, the adsorbent has the advantages that more types of organophosphorus flame retardants can be adsorbed and removed at the same time, the adsorption and removal efficiency on the strong-polarity organophosphorus flame retardants is higher, and the applicable environment water matrix is wider.

Description

Technical Field

[0001] The invention provides a preparation method of melamine foam capable of simultaneously absorbing and removing various types of organophosphorus flame retardants in environmental water, belonging to the technical field of environmental water treatment. Background Art

[0002] Due to their environmental persistence, bioaccumulation, and multiple hazards to ecology and health, the prevention and control of emerging pollutants is a highly valued issue worldwide. Typical persistent pollutants are those with the closest relevance to ecological and environmental safety and public health. Among these, organophosphorus flame retardants are among the emerging pollutants with the closest and most widespread impact on human production and daily life. They are widely used in products such as electronics, plastics, textiles, building materials, and furniture. Because organophosphorus flame retardants are primarily added to these products in physical forms—direct addition, solution addition, coating addition, and composite addition—and do not chemically bond with the materials, they are easily released into the environment through processes such as wear, volatilization, and dissolution during the production, transportation, and use of these materials. This leads to their widespread presence in various media, including wastewater, surface water, dust, air, and sediment, ultimately accumulating in environmental water bodies. Ambient water is a key medium for the transport of organophosphorus flame retardants in the environment. Aromatic, alkyl, and halogenated alkyl organophosphorus flame retardants, primarily tris(2-chloropropyl) phosphate, tris(1,3-dichloroisopropyl) phosphate, tris(2-chloroethyl) phosphate, tris(butoxyethyl) phosphate, triphenyl phosphate, and tributyl phosphate, are detected at concentrations ranging from a few ng / L to several thousand ng / L. Organophosphorus flame retardants are extremely stable and can enter the human body through the food chain, directly impacting human health. Therefore, the adsorption and removal of organophosphorus flame retardants in ambient water is a key issue in the field of environmental water treatment technology.

[0003] There are many types of organophosphorus flame retardants with very different physical and chemical properties. They can be divided into strong polarity, medium polarity and weak polarity organophosphorus flame retardants according to the n-octanol / water partition coefficient, which makes it extremely challenging to simultaneously adsorb organophosphorus flame retardants with very different properties. Conventional adsorption materials such as powdered activated carbon are suitable for treating weakly polar organophosphorus flame retardants, but the adsorption efficiency of strongly polar organophosphorus flame retardants is very low (<30%). This is because strongly polar organophosphorus flame retardants tend to dissolve in water and cannot be effectively removed by hydrophobic effects. In addition, the conditions required to prepare these carbon materials are relatively harsh, and toxic / harmful solvents are used. The used powdered carbon materials are not easy to separate, causing secondary pollution to the environment.

[0004] Existing research and development of new adsorbents for the adsorption and removal of organophosphorus flame retardants in environmental water include covalent organic frameworks, metal-organic frameworks, zeolites, and other prepared adsorbent materials. These adsorbents are often targeted at the adsorption and removal of a single type of triphenyl phosphate, tris(2-chloropropyl) phosphate, or tris(2-chloroethyl) phosphate in environmental water. There is limited research on the efficient and simultaneous adsorption and removal of multiple types of organophosphorus flame retardants in environmental water. Furthermore, when simultaneously adsorbing and removing organophosphorus flame retardants of different polarities, the efficient adsorption and removal of highly polar organophosphorus flame retardants is a difficult and critical point. Furthermore, after adsorption of the target substance, the adsorbents developed in existing research often require secondary separation processes such as centrifugation, magnetic separation, and membrane filtration, which reduces the operational simplicity of the removal method. Therefore, considering the current status of co-contamination of multiple organophosphorus flame retardants in environmental water, the development of efficient adsorbents to simultaneously remove multiple types of organophosphorus flame retardants in environmental water is of great practical significance. Summary of the Invention

[0005] Technical problem: The purpose of the present invention is to prepare and apply a melamine foam that can adsorb multiple types of organophosphorus flame retardants, so that it can simultaneously adsorb and remove pollution from multiple types of organophosphorus flame retardants.

[0006] Technical solution: The preparation method of the melamine foam capable of adsorbing various types of organophosphorus flame retardants of the present invention is prepared by the following steps:

[0007] S1: Preparation of polydopamine-modified melamine foam by oxidative self-polymerization.

[0008] S2: Polydopamine-modified melamine foam was prepared by in situ growth method to obtain polydopamine and metal-organic framework dual-modified melamine foam.

[0009] The step of preparing polydopamine-modified melamine foam from melamine foam by oxidative autopolymerization comprises:

[0010] S1.1: Ultrasonic clean the melamine foam using methanol and then ultrapure water, then dry it in an oven.

[0011] S1.2: Completely immerse the melamine foam treated in step S1.1 in a Tris buffer solution having a concentration of 5 to 20 mmol / L and a pH of 7.0 to 10.0, then dissolve dopamine hydrochloride in the Tris buffer solution to a concentration of 0.5 to 20 mg / mL, and then shake the solution at 50 to 80°C for 8 to 12 hours.

[0012] S1.3: The melamine foam after the reaction is taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0013] The step of preparing polydopamine-modified melamine foam into polydopamine and metal organic framework dual-modified melamine foam by the in situ growth method comprises:

[0014] S2.1: Dissolving a metal salt or metal oxide in methanol to obtain a metal salt / metal oxide-methanol solution, wherein the concentration of the metal salt or metal oxide is 0.05 to 5 mg / mL;

[0015] S2.2: Immerse the polydopamine-modified melamine foam in a metal salt / metal oxide-methanol solution and shake react at 25-60°C for 2-8 hours. Remove the polydopamine-modified melamine foam after the reaction, wash it with methanol, and dry it in an oven to obtain the polydopamine-modified melamine foam loaded with metal ions.

[0016] S2.3: Dissolving a metal salt or metal oxide and an organic ligand in methanol in sequence to obtain a metal salt / metal oxide-organic ligand-methanol solution, wherein the concentrations of the metal salt / metal oxide and the organic ligand are 0.5-20 mg / mL and 5-30 mg / mL, respectively;

[0017] S2.4: Immerse the polydopamine-modified melamine foam loaded with metal ions in the metal salt / metal oxide-organic ligand-methanol solution and shake the reaction at 60-80°C for 2-8 hours; take out the reaction product, wash it with anhydrous ethanol and ultrapure water in sequence, and then place it in an oven to dry to obtain a melamine foam dual-modified with polydopamine and a metal organic framework.

[0018] The metal salts are nitrates or sulfates of copper, iron, zinc, chromium, thorium, aluminum and titanium metal elements, and the metal oxides are oxides of copper, iron, zinc, chromium, thorium, aluminum and titanium metal elements.

[0019] The organic ligands are fumaric acid, citric acid, terephthalic acid, trimesic acid and 2-methylimidazole.

[0020] The melamine foam capable of adsorbing various types of organophosphorus flame retardants prepared by the method described in the present invention is used to adsorb and remove organophosphorus flame retardants in environmental water. 100 to 400 mg of the polydopamine and metal organic framework dual-modified melamine foam is placed in each liter of environmental water sample and fully immersed in the environmental water sample. After the adsorption is completed, the foam is directly removed from the environmental water sample.

[0021] The environmental water includes tap water, surface water, groundwater, domestic sewage, agricultural sewage, medical wastewater or industrial sewage.

[0022] The organophosphorus flame retardant includes an aromatic organophosphorus flame retardant, an alkyl organophosphorus flame retardant or a halogenated alkyl organophosphorus flame retardant.

[0023] Beneficial effects: The present invention discloses a preparation method and application of melamine foam that can simultaneously adsorb and remove multiple types of organophosphorus flame retardants in environmental water. Compared with existing adsorption materials, the present invention has the following advantages and effects:

[0024] (1) A novel in situ growth method was used to prepare polydopamine and metal-organic framework (MOF)-modified melamine foam. Under the "adhesion" effect of polydopamine, metal ions were first anchored to the melamine foam surface. Subsequently, the anchored metal ions served as crystal nuclei and grew into MOFs in cooperation with organic ligands. The synthesized MOFs were evenly distributed on the melamine foam surface, improving the problems of MOFs prepared by one-step or chemical deposition methods, such as easy detachment and uneven growth.

[0025] Through the strong coordination between the abundant amino and hydroxyl functional groups on the surface of polydopamine and metal ions, the metal ions are induced in situ to grow uniformly as crystal nuclei and anchored to the melamine foam substrate, forming a stable chemically bonded interface. Subsequently, the crystal nuclei react with organic ligands to form a metal-organic framework, which is tightly and evenly covered on the surface of the melamine foam, solving the problem of easy detachment and uneven growth of metal-organic frameworks prepared by existing one-step methods or chemical deposition methods. In addition, the metal-organic framework prepared by the in situ growth method is tightly covered in a monodisperse form on the surface of the three-dimensional network of polydopamine-modified melamine foam, forming a micro-nanoscale pore structure, effectively increasing the specific surface area of the melamine foam and facilitating the binding of the organophosphorus flame retardant to the adsorption sites on the adsorbent surface.

[0026] (2) Melamine foams dually modified with polydopamine and metal-organic frameworks provide multiple adsorption mechanisms, which can adsorb a wide variety of organophosphorus flame retardants and are applicable to a wide range of sample matrices.

[0027] The prepared polydopamine and metal organic framework dual-modified melamine foam can simultaneously adsorb organophosphorus flame retardants including aromatic organophosphorus flame retardants, alkyl organophosphorus flame retardants and halogenated alkyl organophosphorus flame retardants. Compared with the existing adsorption materials whose adsorption target types are concentrated on weakly polar organophosphorus flame retardants, the prepared polydopamine and metal organic framework dual-modified melamine foam can adsorb a wide variety of organophosphorus flame retardants.

[0028] Melamine foams dually modified with polydopamine and a metal-organic framework (MOF) form a quaternary adsorption mechanism with organophosphorus flame retardants through electrostatic, hydrophobic, hydrogen-bonding, and π-π interactions. Furthermore, the three-dimensional network structure of the melamine foam skeleton facilitates rapid mass transfer of the OPFFR within the polydopamine / MOF-modified melamine foam and provides ample contact with adsorption sites on the adsorbent surface and internally. This results in an adsorption efficiency of over 50% for various OPFFRs, particularly highly polar OPFFRs. This nearly doubles the adsorption efficiency of existing adsorbent materials, such as powdered activated carbon and nonionic resins, which typically have an adsorption efficiency of less than 30%. The electrostatic, hydrogen-bonding, and π-π interactions provided by polydopamine, along with the hydrophobic, hydrogen-bonding, and π-π interactions provided by the MOF, form the adsorption mechanism for OPFFRs in the polydopamine / MOF-modified melamine foam, enabling efficient co-adsorption of a wide range of OPFFRs. It is suitable for various environmental waters such as tap water, surface water, groundwater, domestic sewage, agricultural sewage, medical wastewater or industrial sewage. It only needs to be immersed in the environmental water sample, and the minimum removal rate of various types of organophosphorus flame retardants in it can reach more than 53.8% within 1 hour.

[0029] (3) The application performance of melamine foam dual-modified with polydopamine and metal-organic framework is excellent: the adsorption application method is flexible and the operation is simple.

[0030] Melamine foam dual-modified with polydopamine and metal-organic framework is a "whole material" that can be directly immersed in ambient water to adsorb and remove organophosphorus flame retardants. After adsorption and removal, no secondary operations such as centrifugal filtration are required. The melamine foam only needs to be removed from the ambient water, and solid-liquid separation can be easily completed. Compared with existing adsorption materials such as powdered activated carbon, covalent organic frameworks / metal-organic frameworks, magnetic materials, etc., which need to be loaded into columns or require high-speed centrifugation or strong magnetic field separation before use, it is not only convenient to operate, but also fundamentally avoids secondary pollution to the environment caused by difficult separation. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] The preparation method of the melamine foam capable of adsorbing various types of organophosphorus flame retardants of the present invention is as follows:

[0033] S1: Preparation of polydopamine-modified melamine foam by oxidative self-polymerization.

[0034] S2: Polydopamine-modified melamine foam was prepared by in situ growth method to obtain polydopamine and metal-organic framework dual-modified melamine foam.

[0035] Example 1: This example is applied to the adsorption and removal of various types of organophosphorus flame retardants in tap water samples;

[0036] The material prepared by the present invention is applied to the adsorption and removal of organophosphorus flame retardants such as triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, triisobutyl phosphate, tributyl phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphate, tri(2-chloroethyl) phosphate, tri(2-chloropropyl) phosphate, tri(1,3-dichloroisopropyl) phosphate and triphenyl phosphate in tap water samples.

[0037] The specific steps are:

[0038] S1: Preparation of polydopamine-modified melamine foam from melamine foam via oxidative self-polymerization

[0039] The melamine foam was ultrasonically cleaned with methanol and ultrapure water in sequence, and then dried in an oven; the melamine foam was completely immersed in a Tris buffer with a concentration of 20 mmol / L and a pH of 7.0, and then dopamine hydrochloride was dissolved in the Tris buffer to make the concentration of dopamine hydrochloride 20 mg / mL, followed by shaking reaction at 50°C for 8 hours; the melamine foam after the reaction was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0040] S2: Preparation of polydopamine-modified melamine foam by in situ growth method to polydopamine- and metal-organic framework-co-modified melamine foam

[0041] Zirconium chloride is dissolved in methanol to obtain a zirconium chloride-methanol solution, wherein the concentration of zirconium chloride is 0.05 mg / mL; polydopamine-modified melamine foam is immersed in the zirconium chloride-methanol solution and shaken at 60°C for 2 hours. The polydopamine-modified melamine foam after the reaction is taken out, washed with methanol, and then dried in an oven to obtain polydopamine-modified melamine foam loaded with zirconium ions; zirconium chloride and terephthalic acid are successively dissolved in methanol to obtain a zirconium chloride-terephthalic acid-methanol solution, wherein the concentrations of zirconium chloride and terephthalic acid are 0.5 mg / mL and 5 mg / mL, respectively; the polydopamine-modified melamine foam loaded with zirconium ions is immersed in the zirconium chloride-terephthalic acid-methanol solution and shaken at 60°C for 8 hours; the reaction product is taken out, washed with anhydrous ethanol and ultrapure water, and then dried in an oven to obtain melamine foam dual-modified with polydopamine and a metal-organic framework.

[0042] S3: Adsorption and removal of organophosphorus flame retardants from tap water using polydopamine and metal-organic framework dual-modified melamine foam as an adsorbent

[0043] 100 mg of polydopamine and metal-organic framework-modified melamine foam was added to each liter of tap water sample and allowed to fully immerse in the water sample. After adsorption was complete, the foam was removed directly from the water sample. The removal efficiency reached over 70%.

[0044] Example 2: This example is applied to the adsorption and removal of various types of organophosphorus flame retardants in river water samples

[0045] The material prepared by the present invention is applied to the adsorption and removal of organophosphorus flame retardants such as triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, triisobutyl phosphate, tributyl phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphate, tri(2-chloroethyl) phosphate, tri(2-chloropropyl) phosphate, tri(1,3-dichloroisopropyl) phosphate and triphenyl phosphate in river water samples. The specific steps are as follows:

[0046] S1: Preparation of polydopamine-modified melamine foam from melamine foam via oxidative self-polymerization

[0047] The melamine foam was ultrasonically cleaned with methanol and ultrapure water in sequence, and then dried in an oven; the melamine foam was completely immersed in a Tris buffer with a concentration of 5 mmol / L and a pH of 10.0, and then dopamine hydrochloride was dissolved in the Tris buffer to make the concentration of dopamine hydrochloride 0.5 mg / mL, followed by shaking reaction at 80°C for 12 hours; the melamine foam after the reaction was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0048] S2: Preparation of polydopamine-modified melamine foam by in situ growth method to polydopamine- and metal-organic framework-co-modified melamine foam

[0049] Dissolve zinc acetate dihydrate in methanol to obtain a zinc acetate dihydrate-methanol solution, wherein the concentration of zinc acetate dihydrate is 5 mg / mL; immerse polydopamine-modified melamine foam in the zinc acetate dihydrate-methanol solution and shake at 25°C for 8 hours. Take out the polydopamine-modified melamine foam after the reaction, wash it with methanol, and dry it in an oven to obtain a polydopamine-modified melamine foam loaded with zinc ions; dissolve zinc acetate dihydrate and 2-methylimidazole in methanol in turn. , obtaining a zinc acetate dihydrate-2-methylimidazole-methanol solution, wherein the concentrations of zinc acetate dihydrate and 2-methylimidazole are 20 mg / mL and 30 mg / mL, respectively; immersing the zinc ion-loaded polydopamine-modified melamine foam in the zinc acetate dihydrate-2-methylimidazole-methanol solution and shaking the reaction at 80°C for 2 hours; taking out the reaction product, washing it with anhydrous ethanol and ultrapure water in sequence, and drying it in an oven to obtain a polydopamine and metal-organic framework dual-modified melamine foam.

[0050] S3: Adsorption and removal of organophosphorus flame retardants from river water using polydopamine and metal-organic framework dual-modified melamine foam as an adsorbent

[0051] 400 mg of polydopamine and metal-organic framework-modified melamine foam was added to each liter of river water sample and allowed to fully penetrate the sample. After adsorption was complete, the foam was removed directly from the sample, achieving a removal efficiency of over 65%.

[0052] Example 3: This example is applied to the adsorption and removal of various types of organophosphorus flame retardants in lake water samples

[0053] The material prepared by the present invention is applied to the adsorption and removal of organophosphorus flame retardants such as triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, triisobutyl phosphate, tributyl phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphate, tri(2-chloroethyl) phosphate, tri(2-chloropropyl) phosphate, tri(1,3-dichloroisopropyl) phosphate and triphenyl phosphate in lake water samples. The specific steps are as follows:

[0054] S1: Preparation of polydopamine-modified melamine foam from melamine foam via oxidative self-polymerization

[0055] The melamine foam was ultrasonically cleaned with methanol and ultrapure water in sequence, and then dried in an oven; the melamine foam was completely immersed in a Tris buffer with a concentration of 15 mmol / L and a pH of 8.5, and then dopamine hydrochloride was dissolved in the Tris buffer to make the concentration of dopamine hydrochloride 15 mg / mL, followed by shaking reaction at 60°C for 10 hours; the melamine foam after the reaction was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0056] S2: Preparation of polydopamine-modified melamine foam by in situ growth method to polydopamine- and metal-organic framework-co-modified melamine foam

[0057] Dissolve zinc acetate dihydrate in methanol to obtain a zinc acetate dihydrate-methanol solution, wherein the concentration of zinc acetate dihydrate is 2 mg / mL; immerse polydopamine-modified melamine foam in the zinc acetate dihydrate-methanol solution, and shake and react at 35°C for 6 hours. Take out the polydopamine-modified melamine foam after the reaction, wash it with methanol, and dry it in an oven to obtain a polydopamine-modified melamine foam loaded with zinc ions; dissolve zinc acetate dihydrate and 2-methylimidazole in methanol in turn. , obtaining a zinc acetate dihydrate-2-methylimidazole-methanol solution, wherein the concentrations of zinc acetate dihydrate and 2-methylimidazole are 10 mg / mL and 25 mg / mL, respectively; immersing the polydopamine-modified melamine foam loaded with zinc ions in the zinc acetate dihydrate-2-methylimidazole-methanol solution, and shaking the reaction at 70°C for 6 hours; taking out the reaction product, washing it with anhydrous ethanol and ultrapure water in sequence, and drying it in an oven to obtain a polydopamine and metal-organic framework dual-modified melamine foam.

[0058] S3: Adsorption and removal of organophosphorus flame retardants from lake water using polydopamine and metal-organic framework dual-modified melamine foam as an adsorbent

[0059] 200 mg of polydopamine and metal-organic framework-modified melamine foam was added to each liter of lake water sample and allowed to fully penetrate the sample. After adsorption was complete, the foam was removed directly from the sample, achieving a removal efficiency exceeding 65%.

[0060] Example 4: This example is applied to the adsorption and removal of various types of organophosphorus flame retardants in industrial wastewater samples

[0061] The material prepared by the present invention is applied to the adsorption and removal of organophosphorus flame retardants such as triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, triisobutyl phosphate, tributyl phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphate, tri(2-chloroethyl) phosphate, tri(2-chloropropyl) phosphate, tri(1,3-dichloroisopropyl) phosphate and triphenyl phosphate in industrial wastewater samples. The specific steps are as follows:

[0062] S1: Preparation of polydopamine-modified melamine foam from melamine foam via oxidative self-polymerization

[0063] The melamine foam was ultrasonically cleaned with methanol and ultrapure water in sequence, and then dried in an oven; the melamine foam was completely immersed in a Tris buffer with a concentration of 10 mmol / L and a pH of 9, and then dopamine hydrochloride was dissolved in the Tris buffer to make the concentration of dopamine hydrochloride 10 mg / mL, followed by shaking reaction at 70°C for 8 hours; the melamine foam after the reaction was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0064] S2: Preparation of polydopamine-modified melamine foam by in situ growth method to polydopamine- and metal-organic framework-co-modified melamine foam

[0065] Zirconium chloride was dissolved in methanol to obtain a zirconium chloride-methanol solution, wherein the concentration of zirconium chloride was 4 mg / mL; polydopamine-modified melamine foam was immersed in the zirconium chloride-methanol solution and shaken at 45°C for 3 hours. The polydopamine-modified melamine foam after the reaction was taken out, washed with methanol, and then dried in an oven to obtain polydopamine-modified melamine foam loaded with zirconium ions; zirconium chloride and fumaric acid were dissolved in methanol in sequence to obtain a zirconium chloride-fumaric acid-methanol solution, wherein the concentrations of zirconium chloride and fumaric acid were 10 mg / mL and 20 mg / mL, respectively; the polydopamine-modified melamine foam loaded with zirconium ions was immersed in the zirconium chloride-fumaric acid-methanol solution and shaken at 65°C for 5 hours; the reaction product was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain melamine foam dual-modified with polydopamine and a metal-organic framework.

[0066] S3: Adsorption and removal of organophosphorus flame retardants from industrial wastewater using polydopamine and metal-organic framework-modified melamine foam as an adsorbent

[0067] 300 mg of polydopamine and metal-organic framework-modified melamine foam was added to each liter of industrial wastewater sample and allowed to fully penetrate the environmental water sample. After adsorption was complete, the foam was directly removed from the environmental water sample. The removal efficiency reached over 53.8%.

[0068] Example 5: This example is applied to the adsorption and removal of various types of organophosphorus flame retardants in domestic sewage samples

[0069] The material prepared by the present invention is applied to the adsorption and removal of organophosphorus flame retardants such as triethyl phosphate, tripropyl phosphate, triisopropyl phosphate, triisobutyl phosphate, tributyl phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphate, tri(2-chloroethyl) phosphate, tri(2-chloropropyl) phosphate, tri(1,3-dichloroisopropyl) phosphate and triphenyl phosphate in domestic sewage samples. The specific steps are as follows:

[0070] S1: Preparation of polydopamine-modified melamine foam from melamine foam via oxidative self-polymerization

[0071] The melamine foam was ultrasonically cleaned with methanol and ultrapure water in sequence, and then dried in an oven; the melamine foam was completely immersed in a Tris buffer with a concentration of 10 mmol / L and a pH of 7.5, and then dopamine hydrochloride was dissolved in the Tris buffer to make the concentration of dopamine hydrochloride 12.5 mg / mL, followed by shaking reaction at 65°C for 12 hours; the melamine foam after the reaction was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

[0072] S2: Preparation of polydopamine-modified melamine foam by in situ growth method to polydopamine- and metal-organic framework-co-modified melamine foam

[0073] Zinc acetate dihydrate was dissolved in methanol to obtain a zinc acetate dihydrate-methanol solution, wherein the concentration of zinc acetate dihydrate was 3.5 mg / mL; polydopamine-modified melamine foam was immersed in the zinc acetate dihydrate-methanol solution and shaken at 55°C for 3 hours. The polydopamine-modified melamine foam after the reaction was taken out, washed with methanol, and dried in an oven to obtain polydopamine-modified melamine foam loaded with zinc ions; zinc acetate dihydrate and 2-methylimidazole were dissolved in methanol in sequence. A zinc acetate dihydrate-2-methylimidazole-methanol solution was obtained, wherein the concentrations of zinc acetate dihydrate and 2-methylimidazole were 15 mg / mL and 30 mg / mL, respectively; the polydopamine-modified melamine foam loaded with zinc ions was immersed in the zinc acetate dihydrate-2-methylimidazole-methanol solution and shaken to react at 60°C for 2 hours; the reaction product was taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain a polydopamine and metal organic framework dual-modified melamine foam.

[0074] S3: Adsorption and removal of organophosphorus flame retardants from domestic sewage using polydopamine and metal-organic framework dual-modified melamine foam as an adsorbent

[0075] 300 mg of polydopamine and metal-organic framework-modified melamine foam was added to each liter of domestic sewage sample and allowed to fully penetrate the environmental water sample. After adsorption was complete, the foam was directly removed from the environmental water sample. The removal efficiency reached over 60%.

[0076] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0077] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing melamine foam capable of adsorbing multiple types of organophosphorus flame retardants, characterized in that: Prepared by the following steps: S1: Preparation of polydopamine-modified melamine foam by oxidative self-polymerization. S2: Polydopamine-modified melamine foam was prepared by in situ growth method to obtain polydopamine and metal-organic framework dual-modified melamine foam.

2. The method for preparing melamine foam capable of adsorbing multiple types of organophosphorus flame retardants according to claim 1, characterized in that: The step of preparing polydopamine-modified melamine foam from melamine foam by oxidative autopolymerization comprises: S1.1: Ultrasonic clean the melamine foam using methanol and then ultrapure water, then dry it in an oven. S1.2: Completely immerse the melamine foam treated in step S1.1 in a Tris buffer solution having a concentration of 5 to 20 mmol / L and a pH of 7.0 to 10.0, then dissolve dopamine hydrochloride in the Tris buffer solution to a concentration of 0.5 to 20 mg / mL, and then shake the solution at 50 to 80°C for 8 to 12 hours. S1.3: The melamine foam after the reaction is taken out, washed with anhydrous ethanol and ultrapure water in sequence, and then dried in an oven to obtain polydopamine-modified melamine foam.

3. The method for preparing melamine foam capable of adsorbing multiple types of organophosphorus flame retardants according to claim 1, characterized in that: The step of preparing polydopamine-modified melamine foam into polydopamine and metal organic framework dual-modified melamine foam by the in situ growth method comprises: S2.1: Dissolving a metal salt or metal oxide in methanol to obtain a metal salt / metal oxide-methanol solution, wherein the concentration of the metal salt or metal oxide is 0.05 to 5 mg / mL; S2.2: Immerse the polydopamine-modified melamine foam in a metal salt / metal oxide-methanol solution and shake react at 25-60°C for 2-8 hours. Remove the polydopamine-modified melamine foam after the reaction, wash it with methanol, and dry it in an oven to obtain the polydopamine-modified melamine foam loaded with metal ions. S2.3: Dissolving a metal salt or metal oxide and an organic ligand in methanol in sequence to obtain a metal salt / metal oxide-organic ligand-methanol solution, wherein the concentrations of the metal salt / metal oxide and the organic ligand are 0.5-20 mg / mL and 5-30 mg / mL, respectively; S2.4: Immerse the polydopamine-modified melamine foam loaded with metal ions in the metal salt / metal oxide-organic ligand-methanol solution and shake the reaction at 60-80°C for 2-8 hours; take out the reaction product, wash it with anhydrous ethanol and ultrapure water in sequence, and then place it in an oven to dry to obtain a melamine foam dual-modified with polydopamine and a metal organic framework.

4. The method for preparing melamine foam capable of adsorbing multiple types of organophosphorus flame retardants according to claim 3, characterized in that: The metal salts are nitrates or sulfates of copper, iron, zinc, chromium, thorium, aluminum and titanium metal elements, and the metal oxides are oxides of copper, iron, zinc, chromium, thorium, aluminum and titanium metal elements.

5. The method for preparing melamine foam capable of adsorbing multiple types of organophosphorus flame retardants according to claim 3, characterized in that: The organic ligands are fumaric acid, citric acid, terephthalic acid, trimesic acid and 2-methylimidazole.

6. An application of melamine foam capable of absorbing multiple types of organophosphorus flame retardants prepared by the method according to claim 3, characterized in that: The organophosphorus flame retardant in the environmental water is adsorbed and removed. 100 to 400 mg of the polydopamine and metal organic framework double-modified melamine foam is placed in each liter of the environmental water sample and fully immersed in the environmental water sample. After the adsorption is completed, the foam is directly taken out from the environmental water sample.

7. The use of the melamine foam capable of adsorbing multiple types of organophosphorus flame retardants as claimed in claim 6, characterized in that: The environmental water includes tap water, surface water, groundwater, domestic sewage, agricultural sewage, medical wastewater or industrial sewage.

8. The use of the melamine foam capable of adsorbing multiple types of organophosphorus flame retardants as claimed in claim 6, characterized in that: The organophosphorus flame retardant includes an aromatic organophosphorus flame retardant, an alkyl organophosphorus flame retardant or a halogenated alkyl organophosphorus flame retardant.