MXene-based composite material as well as preparation method and application thereof
By preparing MXene-based composite materials and utilizing the porous structure and electron-rich properties of polydopamine, combined with photo-Fenton reaction, the problem of unsatisfactory catalytic performance of Fe/MXene composite materials was solved, achieving efficient degradation of dye wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LANZHOU UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2023-11-15
- Publication Date
- 2026-04-14
AI Technical Summary
The existing Fe/MXene composite materials have unsatisfactory catalytic performance and are difficult to effectively treat dye wastewater discharged from the textile printing and dyeing industry.
By preparing MXene-based composite materials, a polymerization reaction was carried out using a template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution, and initiator solution to form an intermediate product. Then, the intermediate product was mixed with a ferrous salt solution and a reducing agent was added to prepare Fe/mPDA/MXene and Fe/C/MXene composite materials. The porous structure and electron-rich properties of polydopamine were used to improve the catalytic performance, and organic pollutants were degraded through photo-Fenton reaction.
The catalytic performance was significantly improved, and the degradation rate of methylene blue in the photo-Fenton reaction reached 99.89% and 99.94%, achieving the effect of efficient treatment of dye wastewater.
Smart Images
Figure CN121847178A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of Fenton catalyst technology, and in particular to an MXene-based composite material, its preparation method, and its application. Background Technology
[0002] Due to rapid urbanization, changing consumption patterns, population expansion, and accelerated socio-economic development, large amounts of pollutants threatening microorganisms, animals, and plants are released into the aquatic environment. Currently, the most common pollutant is dyes emitted from the textile dyeing and printing industry. The textile dyeing and printing industry is a major economic sector, bringing huge economic benefits but also serious environmental pollution problems. According to reports, approximately 740 cubic meters of dye are emitted for every ton of dye produced. 3 Of the wastewater generated, 5% contains dyes that are released into the aquatic environment, resulting in approximately 700 kt of dye wastewater being discharged into the environment annually without proper treatment. Due to its extremely high concentration, stable physicochemical properties, poor biodegradability, and strong pathogenicity, dye industry wastewater poses a significant potential threat as an organic pollutant, harming not only the environment but also human health. Therefore, developing an efficient, energy-saving, and simple-to-operate method for treating organic dyes has become an urgent priority.
[0003] Current research on methods for treating dye wastewater includes physical, chemical, and biological approaches. Biological treatment of dyes in aquatic environments is challenging because it may generate more toxic intermediates, requiring further removal. Physical methods essentially involve the transfer of pollutants and also require subsequent treatment. Chemical methods, due to their high efficiency and speed, have become the preferred technology for treating dye wastewater. In recent years, an environmentally friendly new technology for degrading harmful pollutants in water—Advanced Oxidation Technologies (AOPs)—has received widespread attention from the scientific community. This method generates highly reactive free radicals, such as hydroxyl radicals (·OH), which then combine with organic compounds through addition, substitution, electron transfer, and bond breaking, transforming many complex organic pollutants into non-toxic and harmless small molecules, such as carbon dioxide and water, thereby achieving environmental purification. Among these, Fenton-based oxidation technologies are widely used due to the green and non-toxic nature of the reagents used, as well as their high efficiency, low cost, and low energy consumption.
[0004] Traditional Fenton technology uses ferrous ions (Fe) 2+The Fenton reaction utilizes the attack of hydrogen peroxide (H₂O₂) molecules to generate highly oxidizing hydroxyl radicals (·OH) for the oxidative decomposition of organic pollutants. However, problems such as the separation of homogeneous catalysts from raw materials and products, narrow pH range, and the easy generation of iron sludge severely limit their industrial applications. To improve the shortcomings of the traditional homogeneous Fenton reaction, heterogeneous catalysts using solid catalysts have become a research hotspot. In addition, the introduction of light energy helps to enhance the Fe... 2+ The reaction rate with H2O2 increases, thereby increasing the formation rate of ·OH, because of photosynergistic Fe... 2+ Oxidation of H2O2 promotes Fe 3+ / Fe 2+ The cycle continues. Therefore, the reaction efficiency can be improved by constructing a photo-Fenton reaction system.
[0005] The type and structure of a catalyst directly determine its catalytic performance. Two-dimensional layered materials such as MXene, with their large specific surface area, are commonly used as catalyst supports to improve the dispersion of metal ions, accelerate electron transport, and thus enhance the catalyst's performance. However, the catalytic performance of Fe / MXene composites is not ideal and requires further improvement. Therefore, how to further improve the catalytic performance of MXene-based composites has become a challenge in current technology. Summary of the Invention
[0006] The purpose of this invention is to provide an MXene-based composite material, its preparation method, and its applications. The MXene-based composite material prepared by this invention exhibits better catalytic performance.
[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0008] This invention provides a method for preparing MXene-based composite materials, comprising the following steps:
[0009] (1) The template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution and initiator solution were mixed and then subjected to polymerization to obtain intermediate product;
[0010] (2) After mixing the intermediate product obtained in step (1) with the ferrous salt solution, a reducing agent is added to carry out a reduction reaction to obtain the MXene-based composite material.
[0011] Preferably, the mass ratio of the template agent to the MXene in the monolayer MXene suspension in step (1) is (30-50):1.
[0012] Preferably, the mass ratio of dopamine hydrochloride to MXene in the monolayer MXene suspension in step (1) is (100-110):1.
[0013] Preferably, the mass ratio of dopamine hydrochloride to the initiator in the initiator solution in step (1) is 1:(2-3).
[0014] Preferably, the polymerization temperature in step (1) is 30-40°C and the polymerization time is 20-30 hours.
[0015] Preferably, after the polymerization reaction is completed in step (1), calcination is also performed.
[0016] Preferably, in step (2), the mass ratio of the intermediate product to the ferrous ions in the ferrous salt solution is 1:(2-8).
[0017] The present invention provides an MXene-based composite material prepared by the preparation method described in the above technical solution.
[0018] The present invention also provides the application of the MXene-based composite material described in the above technical solution in the photo-Fenton degradation of organic pollutants.
[0019] This invention provides a method for preparing an MXene-based composite material, comprising the following steps: (1) mixing a template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution, and initiator solution and then performing a polymerization reaction to obtain an intermediate product; (2) mixing the intermediate product obtained in step (1) with a ferrous salt solution and then adding a reducing agent to perform a reduction reaction to obtain the MXene-based composite material. In this invention, the two-dimensional layered mPDA / MXene structure has a large specific surface area, which, when used as a carrier material, improves the dispersion of iron, accelerates electron transport efficiency, and enhances the catalytic performance of the composite material. In the photo-Fenton reaction, polydopamine, as an electron-rich material, under visible light irradiation, also allows its π-electron free radicals to transfer their own electrons to Fe. 3+ Simultaneously, the quinone-phenol conversion process on its surface also plays a role in electron transfer, transferring Fe(OH)₂. 2+ Converted to Fe 2+ Further promote Fe 3+ / Fe 2+ The process involves cycling to improve Fenton oxidation efficiency; adding a template agent to polydopamine to form a porous structure provides a pathway for the diffusion of organic pollutant molecules and hydrogen peroxide, while also increasing the specific surface area of the support, improving the dispersibility and reactivity of subsequent Fe, and enhancing catalytic efficiency; finally, ferrous salt is added for in-situ reduction to form Fe, preparing a Fe / mPDA / MXene composite material, which improves its dispersibility and makes the material magnetic, enabling effective recovery through simple magnetic separation; after preparing mPDA / MXene, calcination is performed to prepare a C / MXene intermediate, which maintains the porous structure, facilitating the catalytic reaction, while the carbon material also promotes Fe... 3+ / Fe2+ The process involves cycling to improve the Fenton oxidation effect, followed by in-situ reduction of ferrous salt to form Fe, thus preparing the Fe / C / MXene composite material, which exhibits excellent catalytic performance. The results of the examples show that the Fe / mPDA / MXene composite material prepared in this invention achieves a methylene blue degradation rate of 99.89% during the photo-Fenton reaction, while the Fe / C / MXene composite material achieves a methylene blue degradation rate of 99.94% during the photo-Fenton reaction. Attached Figure Description
[0020] Figure 1 This is a schematic flowchart of the preparation method of the MXene-based composite material of the present invention;
[0021] Figure 2 The images show the XRD patterns of the Fe / mPDA / MXene composite material, monolayer MXene (DL-MXene), and Fe prepared in Example 1 of this invention.
[0022] Figure 3 This is a TEM image of the mPDA prepared in Comparative Example 4 of this invention;
[0023] Figure 4 This is a TEM image of the mPDA / MXene composite material obtained in step (2) of Example 1 of the present invention;
[0024] Figure 5 This is a TEM image of the Fe / mPDA / MXene composite material prepared in Example 1 of the present invention. Detailed Implementation
[0025] This invention provides a method for preparing MXene-based composite materials, comprising the following steps:
[0026] (1) The template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution and initiator solution were mixed and then subjected to polymerization to obtain intermediate product;
[0027] (2) After mixing the intermediate product obtained in step (1) with the ferrous salt solution, a reducing agent is added to carry out a reduction reaction to obtain the MXene-based composite material.
[0028] Unless otherwise specified, the present invention does not impose any special restrictions on the source of the raw materials, and commercially available products well known to those skilled in the art can be used.
[0029] This invention involves mixing a template agent, a solvent, a monolayer MXene suspension, dopamine hydrochloride, a buffer solution, and an initiator solution, and then performing a polymerization reaction to obtain an intermediate product.
[0030] In this invention, the template agent preferably includes PS. x -b-PEOy F127 or P123, more preferably PS x -b-PEO y The PS x -b-PEO y In the case of x, x is preferably an integer from 50 to 150, more preferably an integer from 70 to 120, and even more preferably 100; the PS x -b-PEO y The value of y is preferably an integer from 100 to 120, more preferably an integer from 110 to 115, and even more preferably 114. In this invention, the template agent is used to form a porous structure in polydopamine, providing a pathway for the diffusion of organic pollutants and hydrogen peroxide, and increasing the specific surface area of the support, which is beneficial to the subsequent dispersion and reaction activity of Fe, thereby improving catalytic performance. This invention limits the type of template agent to the above range, which can adjust the pore size and obtain uniform pore size, further improving its catalytic performance.
[0031] In this invention, the solvent preferably includes tetrahydrofuran, ethanol and water; the volume ratio of tetrahydrofuran, ethanol and water is preferably 1:(0.8-1.2):(1.8-2.2), more preferably 1:1:2.
[0032] In this invention, the mass ratio of the template agent to the volume ratio of the solvent is preferably 120 mg: (150-170) mL, more preferably 120 mg: 160 mL.
[0033] In this invention, each block of the template agent is readily soluble in tetrahydrofuran. When water is added, since water is a poor solvent for hydrophobic segments, the template agent will form spherical micelles through solution self-assembly, serving as a porous template. The porous structure will be formed after the template agent is removed in the subsequent process.
[0034] This invention limits the type and amount of solvent within the above-mentioned range, enabling the template agent to self-assemble into spherical micelles with appropriate size, thereby adjusting the pore size in the composite material and improving its catalytic performance.
[0035] In this invention, the MXene in the monolayer MXene suspension preferably includes Ti3C2, Ti2C, V2C, Nb2C, Ti3CN, and (Ti 0.5 Nb 0.5 )2C, Nb4C3 or Ta4C3, more preferably Ti3C2.
[0036] In this invention, the preferred method for preparing the monolayer MXene suspension is as follows: 10 mL of 12 mol / L HCl is poured into a polytetrafluoroethylene beaker, followed by the addition of 0.78 g of LiF, and the mixture is stirred continuously at room temperature for 15 min. Then, 0.5 g of Ti3AlC2 is very slowly added to the above mixed solution, and the mixture is stirred continuously at 38°C for 48 h. After the reaction is complete, the mixture is washed at least three times by centrifugation with 1 mol / L HCl and 1 mol / L LiCl solutions, and finally washed by centrifugation with deionized water until the pH of the supernatant is approximately 6. The lower layer is then collected and vacuum dried to obtain the sample, which is ML-MXene. An appropriate amount of deionized water is added to ML-MXene for dispersion, and the mixture is sonicated in an ice bath under an argon atmosphere for 45 min, followed by centrifugation at 8000 rpm for 5 min. The dark green supernatant is collected, and the supernatant is freeze-dried to obtain monolayer MXene (DL-MXene). The monolayer MXene is then dispersed in water to obtain a monolayer MXene suspension.
[0037] In this invention, the concentration of the monolayer MXene suspension is preferably 1 to 3 mg / mL, more preferably 1.5 to 2 mg / mL.
[0038] In this invention, the preferred mass ratio of the template agent to MXene in the monolayer MXene suspension is (30-50):1, more preferably 40:1.
[0039] In this invention, the mass ratio of dopamine hydrochloride to MXene in the monolayer MXene suspension is preferably (100-110):1, more preferably (105-110):1; the mass ratio of the template agent to dopamine hydrochloride is 1:(2-3), more preferably 1:(2.5-3).
[0040] In this invention, the subsequent polymerization of dopamine hydrochloride forms polydopamine that encapsulates MXene, preventing MXene aggregation; simultaneously, the quinone-phenol conversion in the polydopamine during the photo-Fenton reaction promotes Fe... 3+ / Fe 2+ The cycle; at the same time, polydopamine is an electron-rich material, and the π-electron free radicals in it will also transfer their own electrons to Fe. 3+ Furthermore, its surface contains a large number of oxygen-containing functional groups, which also play a role in electron transfer, transferring Fe(OH)₂. 2+ Converted to Fe 2+ Further promote Fe 3+ / Fe 2+ The cycle improves the Fenton oxidation effect.
[0041] This invention limits the mass ratio of dopamine hydrochloride and MXene in a monolayer MXene suspension, as well as the mass ratio of the template agent and dopamine hydrochloride, to the above-mentioned ranges. This allows for the adjustment of the polydopamine content and pore content in the composite material, thereby further improving its catalytic performance.
[0042] In this invention, the buffer solution is preferably an aqueous solution of trihydroxyaminomethane (Tris); the concentration of the buffer solution is preferably 15-20 mg / mL, more preferably 18-20 mg / mL. In this invention, the volume ratio of the buffer solution to the monolayer MXene suspension is preferably (4-6):1, more preferably 5:1. In this invention, after adding the buffer solution, the pH value of the system is preferably 8-9, more preferably 8.5. In this invention, the buffer solution is used to adjust the pH value of the system, which is beneficial to the polymerization of dopamine hydrochloride.
[0043] In this invention, the initiator solution is preferably an aqueous solution of ammonium persulfate; the concentration of the initiator solution is preferably 30-40 mg / mL, more preferably 35-40 mg / mL.
[0044] In this invention, the mass ratio of dopamine hydrochloride to the initiator in the initiator solution is preferably 1:(2-3), more preferably 1:(2-2.5). In this invention, the initiator solution is used to initiate the polymerization reaction of dopamine hydrochloride. By limiting the mass ratio of dopamine hydrochloride to the initiator in the initiator solution to the above range, this invention enables dopamine hydrochloride to polymerize sufficiently and achieve a suitable polymerization rate.
[0045] In this invention, the preferred mixing method for the template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution, and initiator solution is as follows: the template agent is dissolved in tetrahydrofuran, then a mixed solution of ethanol and water is added, and the mixture is stirred for 20–40 min. The monolayer MXene suspension and dopamine hydrochloride are then added, and the mixture is stirred for 0.5–2 h. The buffer solution is then added, and the mixture is stirred for 1 h in a water bath at 30–40°C. Finally, the initiator solution is slowly added dropwise. Using this mixing method, the template agent forms micelles of suitable size, and the components are dissolved and mixed more thoroughly and uniformly.
[0046] In this invention, the polymerization temperature is preferably 30–40°C, more preferably 32–38°C, and even more preferably 35°C; the polymerization time is preferably 20–30 h, more preferably 22–28 h, and even more preferably 24–26 h. By limiting the polymerization temperature and time to the above ranges, this invention enables dopamine hydrochloride to fully polymerize and achieve a suitable polymerization rate.
[0047] After the polymerization reaction is completed, the present invention preferably washes the product after the polymerization reaction with water, ethanol, tetrahydrofuran and freeze-drying in sequence to obtain an intermediate product.
[0048] In this invention, the water washing, ethanol washing and tetrahydrofuran washing can remove the template agent, form a porous structure, and remove unreacted raw materials.
[0049] The present invention does not impose any special limitations on the freeze-drying operation; any freeze-drying technical solution known to those skilled in the art can be used.
[0050] In this invention, the intermediate product is an mPDA / MXene composite material.
[0051] In this invention, after the freeze-drying is completed, the freeze-dried product is preferably calcined to obtain an intermediate product.
[0052] In this invention, the calcination temperature is preferably 800–1000°C, more preferably 900°C; the calcination time is preferably 1–3 h, more preferably 2 h; the heating rate to the calcination temperature is preferably 4–6°C / min, more preferably 5°C / min; and the calcination is preferably carried out in an argon atmosphere. In this invention, during the calcination process, polydopamine decomposes to form carbon material. In this invention, the carbon material maintains the porous structure of polydopamine, providing a pathway for the diffusion of organic pollutant molecules and hydrogen peroxide; simultaneously, it increases the specific surface area of the support, improves the dispersibility and reactivity of subsequent Fe, and enhances catalytic efficiency; furthermore, carbon has good conductivity, playing a role in electron transfer and promoting Fe… 3+ / Fe 2+ The cycle enhances the Fenton oxidation effect. This invention limits the calcination temperature, time, and other parameters within the aforementioned range, enabling polydopamine to fully decompose into carbon materials while maintaining its porous structure from collapsing.
[0053] In this invention, the intermediate product after calcination is a C / MXene composite material.
[0054] After calcination, the present invention preferably cools the calcined product and stores it under argon-sealed conditions.
[0055] After obtaining the intermediate product, the present invention mixes the intermediate product with a ferrous salt solution, adds a reducing agent to carry out a reduction reaction, and obtains an MXene-based composite material.
[0056] In this invention, the ferrous salt in the ferrous salt solution is preferably FeSO4·7H2O; the concentration of the ferrous salt solution is preferably 0.035-0.14 mol / L, more preferably 0.12-0.14 mol / L.
[0057] In this invention, the mass ratio of the intermediate product to the ferrous ions in the ferrous salt solution is preferably 1:(2-8), more preferably 1:(6-8).
[0058] In this invention, the ferrous salt subsequently forms Fe, which serves as the active component in Fenton oxidation and is also magnetic, allowing the composite material to be recovered through simple magnetic separation. This invention limits the mass ratio of the intermediate product to the ferrous salt in the ferrous salt solution to the aforementioned range, thereby adjusting the Fe content in the composite material and ensuring its uniform dispersion in the support, further improving its catalytic performance.
[0059] In this invention, the reducing agent is preferably sodium borohydride; the reducing agent is preferably added in the form of an aqueous reducing agent solution; the concentration of the aqueous reducing agent solution is preferably 0.5-0.8 mol / L, more preferably 0.6 mol / L.
[0060] In this invention, the molar ratio of the ferrous salt to the reducing agent is preferably (0.1–0.5):1, more preferably (0.2–0.4):1. By limiting the molar ratio of the ferrous salt to the reducing agent within the above range, this invention enables the ferrous salt to be fully reduced to form Fe.
[0061] In this invention, the mixing of the intermediate product and the ferrous salt solution is preferably carried out by adding the intermediate product to the ferrous salt solution and sonicating under an argon atmosphere for 20–40 minutes. Using the mixing method of this invention results in a more uniform mixture of the two components.
[0062] In this invention, the temperature of the reduction reaction is preferably 20–30°C; the time of the reduction reaction is preferably 1–3 hours, more preferably 2 hours; and the reduction reaction is preferably carried out in an argon atmosphere. By limiting the temperature and time of the reduction reaction within the above ranges, this invention enables the ferrous salt to be fully reduced.
[0063] After the reduction reaction is completed, the product of the reduction reaction is preferably subjected to magnetic separation, water washing, ethanol washing and drying in sequence to obtain MXene-based composite material.
[0064] The present invention does not impose any special limitations on the operation of magnetic separation, water washing, ethanol washing and drying; any technical solution known to those skilled in the art for magnetic separation, water washing, ethanol washing and drying can be used.
[0065] In this invention, when the intermediate product is an mPDA / MXene composite material, the MXene-based composite material is an Fe / mPDA / MXene composite material; when the intermediate product is a C / MXene composite material, the MXene-based composite material is an Fe / C / MXene composite material.
[0066] In this invention, the two-dimensional layered structure of mPDA / MXene possesses a large specific surface area, making it suitable as a support material to improve iron dispersion, accelerate electron transport efficiency, and enhance the catalytic performance of the composite material. In the photo-Fenton reaction, the quinone-phenol conversion in polydopamine promotes Fe... 3+ / Fe 2+ The cycle; at the same time, polydopamine is an electron-rich material, and under visible light irradiation, its π-electron free radicals will also transfer their own electrons to Fe. 3+ Accelerate Fe(OH) 2+ Converted to Fe 2+ Further promote Fe 3+ / Fe 2+ The process involves cycling to improve Fenton oxidation efficiency; adding a template agent to polydopamine to form a porous structure provides a pathway for the diffusion of organic pollutant molecules and hydrogen peroxide, while also increasing the specific surface area of the support, thereby improving catalytic efficiency; finally, ferrous salt is added for in-situ reduction to form Fe, preparing an Fe / mPDA / MXene composite material, improving its dispersibility and making the material magnetic, enabling effective recovery through simple magnetic separation; after preparing mPDA / MXene, calcination is performed to prepare a C / MXene intermediate, which maintains the porous structure, facilitating the catalytic reaction, while the carbon material also promotes Fe... 3+ / Fe 2+ The Fenton oxidation effect is improved by cycling the ferrous salt and then reducing it in situ to form Fe, thus preparing the Fe / C / MXene composite material, which has excellent catalytic performance. By controlling the amount of each raw material, reaction temperature and other process parameters, the catalytic performance of the composite material can be further improved.
[0067] In this invention, the preferred flowchart for the preparation method of the MXene-based composite material is as follows: Figure 1 As shown.
[0068] The present invention provides an MXene-based composite material prepared by the preparation method described in the above technical solution.
[0069] The MXene-based composite material prepared by this invention has better catalytic performance.
[0070] The present invention also provides the application of the MXene-based composite material described in the above technical solution in the photo-Fenton degradation of organic pollutants.
[0071] In this invention, the MXene-based composite material is preferably added to an aqueous solution containing organic pollutants, hydrogen peroxide is added, and a photo-Fenton degradation reaction is carried out under light irradiation.
[0072] In this invention, the organic pollutant in the photo-Fenton degradation of organic pollutants is preferably a dye, more preferably methylene blue MB; the concentration of the organic pollutant is preferably 1-10 g / L; the amount of the MXene-based composite material is preferably 0.1-0.5 g / L; the pH value of the photo-Fenton degradation reaction is preferably 2-5; the concentration of hydrogen peroxide is preferably 30-90 mmol / L, more preferably 70-90 mmol / L; and the temperature of the photo-Fenton degradation reaction is preferably 40-50°C.
[0073] By controlling the parameters during photo-Fenton degradation of organic pollutants within the above-mentioned range, this invention can improve the degradation effect of organic pollutants.
[0074] In this invention, during the photo-Fenton degradation of MB by Fe / mPDA / MXene: the abundant functional groups on the surface of mPDA / MXene, its two-dimensional structure, and the adsorption properties of zero-valent iron allow MB to be adsorbed onto the catalyst surface first. The lower pH and H2O2 then oxidize Fe to Fe2+. 2+ H2O2 is reacted with Fe 2+ Catalytic generation of ·OH and Fe 3+ Fe 3+ It can also catalyze the formation of ·O from H2O2. 2- It is reduced to Fe 2+ However, this reaction is extremely slow. Fe donates three electrons when participating in the reaction, thus reducing Fe2's electron count. 3+ Reduced to Fe 2+ Promote Fe 3+ / Fe 2+ The two-dimensional structure of Fe / mPDA / MXene fully exposes the active sites of the material, and the porous structure facilitates the rapid transport of H2O2 and MB, enhancing the accessibility of the active sites. When light irradiates the surface of the catalyst, the quinone-phenol conversion in PDA promotes the cycling of Fe. 3+ / Fe 2+ In the cycle, the π-electron free radicals in the PDA also transfer their own electrons to Fe. 3+ The numerous oxygen-containing functional groups on the surface of mPDA / MXene play a role in electron transfer and also transfer Fe(OH)2. 2+ Converted to Fe 2 + Further promote Fe 3+ / Fe 2+ The cycle continues; in addition, visible light can directly decompose H2O2 to generate ·OH, which attacks MB and destroys the MB structure, thereby achieving the purpose of degradation and decolorization.
[0075] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0076] Example 1
[0077] (1) Pour 10 mL of 12 mol / L HCl into a polytetrafluoroethylene beaker, then add 0.78 g of LiF and stir continuously at room temperature for 15 min. Then add 0.5 g of Ti3AlC2 to the above mixed solution and stir continuously at 38 °C for 48 h. After the reaction is complete, centrifuge and wash three times with 1 mol / L HCl and 1 mol / L LiCl solutions respectively, and finally centrifuge and wash with deionized water until the pH of the supernatant is 6. Take the lower layer deposition and vacuum dry the sample to obtain ML-MXene. Add an appropriate amount of deionized water to redisperse ML-MXene, and sonicate in an ice bath for 45 min under an argon atmosphere. Centrifuge at 8000 rpm for 5 min and collect the dark green supernatant. Freeze-dry the supernatant to obtain monolayer MXene (DL-MXene). Disperse the monolayer MXene in water to obtain a monolayer MXene suspension with a concentration of 1.5 mg / mL.
[0078] (2) Take 120mg PS 100 -b-PEO 114 Dissolve in 40 mL of tetrahydrofuran, then pour in a mixture of 40 mL of ethanol and 80 mL of deionized water (the volume ratio of tetrahydrofuran, ethanol, and water is 1:1:2). 100 -b-PEO 114 The volume ratio of MXene to solvent was 120 mg: 160 mL. After stirring for 30 min, 2 mL of a 1.5 mg / mL monolayer MXene suspension and 320 mg of dopamine hydrochloride (PS) were added. 100 -b-PEO 114 The mass ratio of MXene in the monolayer MXene suspension was 40:1, and the mass ratio of dopamine hydrochloride to MXene in the monolayer MXene suspension was 107:1. PS 100 -b-PEO 114The mixture was stirred for 1 hour, and then 10 mL of an aqueous solution containing 192 mg of trihydroxyaminomethane (Tris) was slowly added (the concentration of the Tris aqueous solution was 19.2 mg / mL, and the volume ratio of the Tris aqueous solution to the monolayer MXene suspension was 5:1). The pH of the solution was adjusted to 8.5, and the water bath temperature was set to 35 °C. The mixture was stirred for 1 hour, and then 20 mL of an aqueous solution containing 768 mg of ammonium persulfate was slowly added dropwise (the concentration of the ammonium persulfate aqueous solution was 38.4 mg / mL, and the mass ratio of dopamine hydrochloride to ammonium persulfate was 1:2.4). The mixture was reacted for 24 hours, and then washed and centrifuged with deionized water, ethanol, and tetrahydrofuran in sequence. The brown-black precipitate was collected, and after freeze-drying, a two-dimensional mesoporous mPDA / MXene composite material was obtained.
[0079] (3) Add 0.1g of mPDA / MXene composite material obtained in step (2) to 100mL of 0.12mol / L FeSO4·7H2O solution (the mass ratio of ferrous ions in mPDA / MXene composite material and FeSO4·7H2O solution is 1:7), sonicate under argon atmosphere for 30min, add 50mL of 0.6mol / L sodium borohydride solution (the molar ratio of Fe2SO4·7H2O and sodium borohydride is 0.4:1) under continuous argon flow, react for 2h, magnetically separate, wash with deionized water and ethanol, vacuum dry at 65℃, seal and store under argon to obtain MXene-based composite material, i.e. Fe / mPDA / MXene composite material.
[0080] Example 2
[0081] The template agent PS in step (2) of Example 1 100 -b-PEO 114 Replace with PS 50 -b-PEO 114 All other parameters were the same as in Example 1. The product was named Fe / mPDA / MXene-50.
[0082] Example 3
[0083] The template agent PS in step (2) of Example 1 100 -b-PEO 114 Replace with PS 150 -b-PEO 114 All other parameters were the same as in Example 1. The product was named Fe / mPDA / MXene-150.
[0084] Example 4
[0085] In step (4) of Example 1, the mass ratio of mPDA / MXene composite material to ferrous ions was replaced with 1:2, and the molar ratio of Fe2SO4·7H2O to sodium borohydride was 0.4:1. All other parameters were the same as in Example 1. The product was named mPDA / MXene-1.
[0086] Example 5
[0087] In step (4) of Example 1, the mass ratio of mPDA / MXene composite material to ferrous ions was replaced with 1:4, and the molar ratio of Fe2SO4·7H2O to sodium borohydride was 0.4:1. All other parameters were the same as in Example 1. The product was named mPDA / MXene-2.
[0088] Example 6
[0089] In step (4) of Example 1, the mass ratio of mPDA / MXene composite material to ferrous ions was replaced with 1:8, and the molar ratio of Fe2SO4·7H2O to sodium borohydride was 0.4:1. All other parameters were the same as in Example 1. The product was named mPDA / MXene-3.
[0090] Example 7
[0091] Steps (1) to (2) are the same as in Example 1, resulting in a two-dimensional mesoporous mPDA / MXene composite material;
[0092] (3) The two-dimensional mesoporous mPDA / MXene composite material obtained in step (2) is passed into a tube furnace and heated to 900°C at a heating rate of 5°C / min under an argon atmosphere. It is then calcined for 2 hours and cooled to obtain the C / MXene composite material.
[0093] (4) Add 0.1g of C / MXene composite material obtained in step (3) to 100mL of 0.12mol / L FeSO4·7H2O solution, and sonicate under argon atmosphere for 30min (the mass ratio of ferrous ions in C / MXene composite material and FeSO4·7H2O solution is 1:7). Under continuous argon flow, add 50mL of 0.6mol / L sodium borohydride solution, react for another 2h, separate magnetically, wash with deionized water and ethanol, dry under vacuum at 65℃, and seal and store under argon to obtain MXene-based composite material, i.e., Fe / C / MXene composite material.
[0094] Comparative Example 1
[0095] The template agent in Example 1 was omitted, and all other parameters were the same as in Example 1, resulting in a Fe / mPDA / MXene composite material without a porous structure. The product was named Fe / mPDA / MXene-0.
[0096] Comparative Example 2
[0097] The mPDA / MXene composite material in Example 1 is omitted, i.e., pure Fe.
[0098] Comparative Example 3
[0099] The mPDA / MXene composite material in step (3) of Example 1 is replaced with MXene, and all other parameters are the same as in Example 1, thus obtaining the Fe / MXene material.
[0100] Comparative Example 4
[0101] 10 mL of an aqueous solution containing 192 mg of trihydroxyaminomethane (19.2 mg / mL) was slowly added to 320 mg of dopamine hydrochloride. The pH of the solution was adjusted to 8.5, and the water bath temperature was set to 35 °C. The mixture was stirred for 1 h, and then 20 mL of an aqueous solution containing 768 mg of ammonium persulfate (38.4 mg / mL, with a mass ratio of dopamine hydrochloride to ammonium persulfate of 1:2.4) was slowly added dropwise. The mixture was reacted for 24 h, washed with deionized water, and centrifuged to obtain polydopamine PDA.
[0102] The XRD patterns of the Fe / mPDA / MXene composite material, monolayer MXene (DL-MXene), and Fe prepared in Example 1 are shown below. Figure 1 As shown. From Figure 1 As can be seen from the XRD pattern, DL-MXene exhibits a distinct diffraction peak at 2θ = 6.12°, which corresponds to the (002) crystal plane of MXene. The interlayer spacing of MXene can be calculated using the Bragg equation. This indicates that MXene nanosheets have a typical layered structure. After combining PDA and Fe, the peak at the (002) crystal plane of the Fe / mPDA / MXene composite material disappears, which may be due to the inhibition of self-stacking of DL-MXene. The broad peak of mPDA / MXene at 2θ = 15° to 30° is due to the amorphous structure in the sample. At the same time, compared with DL-MXene, there is no obvious characteristic peak in the XRD pattern of Fe / mPDA / MXene at 2θ = 60.4°, which may be due to the lower MXene content in the composite material. The diffraction peaks of Fe and Fe / mPDA / MXene at 2θ = 44.7°, 64.8° and 82.3° correspond to the characteristic diffraction peaks of the (110), (200) and (211) crystal planes, respectively (JCPDS No. 87-0721), indicating that the Fe-loaded composite material was successfully synthesized.
[0103] Transmission electron microscopy (TEM) was used to observe the mPDA prepared in Comparative Example 4, the mPDA / MXene composite material obtained in step (2) of Example 1, and the Fe / mPDA / MXene composite material prepared in Example 1. The TEM images obtained are shown below. Figures 2-4 As shown. From Figures 2-4 As can be seen, tightly packed mesopores are formed on the surface of the two-dimensional MXene nanosheets. Furthermore, the folds in the images show that the mPDA layer covers both sides of the two-dimensional nanosheets, indicating a sandwich-like structure for mPDA / MXene and a transparent sheet-like structure for DL-MXene. Some areas exhibit a rolled-up, stacked appearance, which is a self-stacking phenomenon of MXene. Additionally, black particles are observed dispersed on the surface. Figure 4 The XRD test results confirmed that the particles were Fe, indicating that MXene can improve the dispersibility of Fe.
[0104] Application Examples 1-4
[0105] The composite material prepared in Example 1 was tested to determine the adsorption and degradation rates of methylene blue (MB) in 100 mL of solution under light irradiation. The concentration of methylene blue was 4 g / L, the amount of catalyst was 0.1 g / L, the pH was 3, the hydrogen peroxide concentrations were 30, 50, 70 and 90 mmol / L, and the reaction temperature was 47 °C. First, dark adsorption was performed for 30 min, with an adsorption rate of 4.24%. Then, degradation was carried out under light irradiation. The degradation rates of methylene blue under different hydrogen peroxide concentrations are shown in Table 1.
[0106] Table 1. Degradation rate of methylene blue at different hydrogen peroxide concentrations
[0107] hydrogen peroxide concentration mmol / L 5-minute degradation rate % 30min degradation rate % 30 80.21 81.68 50 93.87 95.52 70 99.77 99.89 90 99.88 100
[0108] As shown in Table 1, when different amounts of H2O2 (30, 50, 70, and 90 mmol / L) were added to 100 mL of MB solution, the degradation of MB approximately reached a dynamic equilibrium after 5 min of reaction, with degradation rates of 80.21%, 93.87%, 99.77%, and 99.88%, respectively. Insufficient H2O2 was insufficient to catalyze the photo-Fenton reaction to generate enough ·OH to completely oxidize and degrade MB. As the amount of H2O2 added increased, the degradation rate gradually increased. After 30 min of photo-Fenton degradation of MB by Fe / mPDA / MXene, the degradation rates of 70 mmol / L and 90 mmol / L H2O2 were 99.89% and 100%, respectively, with roughly the same degradation effect. From an economic perspective, the concentration of H2O2 required for the photo-Fenton oxidation process catalyzed by Fe / mPDA / MXene only needs to be 70 mmol / L.
[0109] Application Examples 5-8, Comparative Application Examples 1-3
[0110] The degradation rate of methylene blue (MB) in 100 mL of solution prepared in Example 1 was tested under light irradiation. The concentration of methylene blue was 4 g / L, the amount of catalyst was 0.1 g / L, the pH values were 2, 3, 4, 5, 7, 9, and 11, the hydrogen peroxide concentration was 70 mmol / L, and the reaction temperature was 47 °C. Dark adsorption was first performed for 30 min, followed by degradation under light irradiation. The degradation rates of methylene blue under different pH conditions are shown in Table 2.
[0111] Table 2 Degradation rate of methylene blue under different pH conditions
[0112] pH Degradation rate (%) after 30 min of reaction 2 85.9 3 99.89 4 93.94 5 67.9 7 18.57 9 8.73 11 4.11
[0113] Table 2 shows that the degradation rates of MB were 85.9%, 99.89%, 93.94%, 67.9%, 18.57%, 8.73%, and 4.11% respectively when the pH increased from 2 to 11. The degradation rate initially increased and then decreased. At lower pH values, the oxidizing power of free radicals was enhanced, significantly improving the efficiency of the Fenton reaction. However, when the pH was too low, Fe... 2+ The reduction reaction causes dissolution, leading to the leaching of Fe and reducing its degradation rate. As pH increases, the decomposition reaction of H₂O₂ becomes easier, as the oxygen and water in H₂O₂ can dissolve Fe. 2+ Oxidized to Fe 3+ But Fe 3+ The catalytic effect is very weak. Therefore, while generating O2, it also leads to a decrease in H2O2 in the solution, and a decrease in Fe. 2+ Its important role in the Fenton reaction also diminishes with increasing pH. Fe mainly reacts as Fe(OH)₂. 2+ It exists in the form of Fe, therefore Fe 2+ The content of [unspecified substance] will decrease accordingly. Due to the influence of these factors, an increase in the pH value of the Fenton reaction solution will lead to a significant decrease in the degradation efficiency and degradation rate of organic matter in the solution. Therefore, the photo-Fenton oxidation and photo-Fenton degradation of MB by Fe / mPDA / MXene is more suitable under acidic conditions, with an optimal pH of 3.
[0114] Application Examples 9-12, Comparative Examples 4-6
[0115] The adsorption and degradation rates of methylene blue (MB) in 100 mL of solution prepared in Examples 1, 2, 3, 9, Comparative Examples 1, 2, and 3 were tested under light irradiation. The concentration of methylene blue was 4 g / L, the amount of catalyst was 0.1 g / L, the pH was 3, the hydrogen peroxide concentration was 70 mmol / L, and the reaction temperature was 47 °C. Dark adsorption was performed for 30 min first, followed by degradation under light irradiation. The dark adsorption and degradation rates of different materials for methylene blue are shown in Table 3.
[0116] Table 3 Dark adsorption rate and degradation rate of methylene blue by different Fenton catalysts
[0117]
[0118] As shown in Table 3, Fe, Fe / MXene, Fe / mPDA / MXene, Fe / mPDA / MXene-0, Fe / mPDA / MXene-50, Fe / mPDA / MXene-150, and Fe / C / MXene can adsorb 0.55%, 2.68%, 4.58%, 4.24%, 0.67%, 2.25%, and 2.43% of MB, respectively, within 30 min. Compared to Fe, the composite material showed a slightly higher adsorption capacity, possibly due to the improved Fe dispersion resulting from the combination of Fe with supports such as MXene. This increased the number of active sites on the catalyst, leading to a higher adsorption capacity, but the adsorption rates remained low, indicating that the adsorption effect of each catalyst on MB at the experimental concentration was not significant. After the addition of light and H₂O₂, the photo-Fenton reaction degraded 21.26%, 81.20%, 99.89%, 99.94%, 80.80%, 84.91%, and 88.12% of MB in 30 min, respectively. This demonstrates that loading MXene and mPDA / MXene onto the Fe surface significantly improved the MB degradation rate. Fe / mPDA / MXene and Fe / C / MXene showed the highest degradation efficiencies. Furthermore, the composite material prepared with a porous structure formed by adding a template agent exhibited a higher degradation rate compared to the one without a template agent, suggesting that appropriate pore size facilitates the transport of H₂O₂ and MB. The template agent was PS. 100 -b-PEO 114 The composite material exhibits the best degradation performance, indicating that a suitable structure can further improve the degradation rate of MB.
[0119] Application Examples 13-16
[0120] The adsorption and degradation rates of methylene blue (MB) in 100 mL of solution prepared in Examples 1, 4, 5, and 6 were tested under light irradiation. The concentration of methylene blue was 4 g / L, the amount of catalyst was 0.1 g / L, the pH was 3, the hydrogen peroxide concentration was 70 mmol / L, and the reaction temperature was 47 °C. Dark adsorption was performed for 30 min first, followed by degradation under light irradiation. The dark adsorption and degradation rates of different materials for methylene blue are shown in Table 4.
[0121] Table 4. Dark adsorption rate and degradation rate of methylene blue by Fenton catalysts with different Fe contents.
[0122]
[0123] Table 4 shows that iron content has little effect on the adsorption rate of MB, but a significant effect on its photo-Fenton degradation rate. The degradation rate gradually increases with increasing iron content, especially when the mPDA / MXene composite material contains Fe... 2+ When the mass ratio is 1:7, the efficiency of photo-Fenton degradation of MB reaches its highest level (99.84%). Further increases in iron content and Fe... 2+ When the mass ratio is 1:8, the efficiency of photo-Fenton degradation of MB decreases. This may be because insufficient mPDA / MXene composite material is not enough to uniformly disperse Fe and cannot provide sufficient pathways for the transport of H2O2 and MB.
[0124] To investigate free radicals in the photo-Fenton process, a free radical capture experiment was conducted. The specific method was as follows: 10 mg of the MXene-based composite material prepared in Example 1 was added to 100 mL of 4 g / L MB solution. The pH was adjusted to 3, and 70 mmol / L H2O2 and a stable light source were added. After reacting for a certain time, the mixture was filtered. The filtrate was then thoroughly mixed with tert-butanol, ammonium oxalate, and p-benzoquinone stock solutions at a 1:1 ratio to capture ·OH and h2O2 in the solution. + and O2 - The results showed that the introduction of tert-butanol significantly reduced the MB degradation rate, from 99.89% to 75.16%, indicating that ·OH has a significant impact on the photo-Fenton catalytic degradation of MB by Fe / mPDA / MXene; the addition of ammonium oxalate to capture h + It has a slight impact on the degradation rate of MB; the addition of p-benzoquinone captures O2. - The subsequent process had almost no effect on the degradation rate of MB, indicating that h + It plays a minor role in the degradation process. ·O2 -The Fe / mPDA / MXene catalyst played almost no role in the photo-Fenton oxidation degradation of MB. Further verification using EPR testing revealed the presence of free radicals in the photo-Fenton reaction. When free radicals were generated in the solution, DMPO instantaneously captured them, and the resulting signal was detected by EPR. When only the catalyst and H2O2 were present in the solution, and MB was absent, a strong ·OH signal was generated under illumination. This indicates that Fe / mPDA / MXene catalyzed H2O2, producing a large amount of ·OH, further demonstrating that ·OH is the active species in the Fe / mPDA / MXene photo-Fenton catalytic oxidation degradation of MB.
[0125] In summary, the composite material prepared by this invention has better catalytic performance and a higher degradation rate of methylene blue.
[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing an MXene-based composite material, comprising the following steps: (1) The template agent, solvent, monolayer MXene suspension, dopamine hydrochloride, buffer solution and initiator solution were mixed and then subjected to polymerization to obtain intermediate product; (2) After mixing the intermediate product obtained in step (1) with the ferrous salt solution, a reducing agent is added to carry out a reduction reaction to obtain the MXene-based composite material.
2. The preparation method according to claim 1, characterized in that, The mass ratio of the template agent and the MXene in the monolayer MXene suspension in step (1) is (30-50):
1.
3. The preparation method according to claim 1, characterized in that, The mass ratio of dopamine hydrochloride to MXene in the monolayer MXene suspension in step (1) is (100-110):
1.
4. The preparation method according to claim 1, characterized in that, The mass ratio of dopamine hydrochloride to the initiator in the initiator solution in step (1) is 1:(2-3).
5. The preparation method according to claim 1, characterized in that, The polymerization temperature in step (1) is 30-40°C and the polymerization time is 20-30 hours.
6. The preparation method according to claim 1, characterized in that, After the polymerization reaction in step (1) is completed, calcination is also performed.
7. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of the intermediate product to the ferrous ions in the ferrous salt solution is 1:(2-8).
8. The MXene-based composite material prepared by the preparation method according to any one of claims 1 to 7.
9. The application of the MXene-based composite material according to claim 8 in the photo-Fenton degradation of organic pollutants.