Catalytic ozonation water treatment method for regulating and controlling structural characteristics of MXene by carbon nitride

Abstract

The invention discloses a catalytic ozonation water treatment method for regulating and controlling the structural characteristics of MXene by carbon nitride, MXene is used as a matrix, carbon nitride is introduced by a one-step pyrolysis method, the prepared catalyst can increase the interlayer spacing of MXene to 1.41 nm and improve the layer structure ozone molecule transmission capability and contact area, the Raman ID / IG value is increased from 0.87 to 1.23, the carbon defect is increased, and the water treatment effect is improved. And more reaction active sites are provided. When the catalyst is used for catalyzing an ozone oxidation system to deeply treat pharmaceutical tail water, under the conditions that the ozone concentration is 5-20 mg / L, the catalyst dosage is 50-200 mg / L, the pH is 4.0-10.6 and the like, the ibuprofen removal rate can be increased to 90.1% from 28.0%, and efficient degradation of trace organic matter is achieved. The catalyst is simple and environment-friendly in preparation process, is a solid and is easy to recover, environmental pollution is reduced, and the catalyst has a good application prospect.

Description

Technical Field

[0001] The present invention relates to a catalytic ozone oxidation water treatment method in which carbon nitride regulates the structural properties of MXene, and belongs to the field of water pollution control engineering. Background Art

[0002] Difficult-to-treat pharmaceutical wastewater contains pharmaceutical substances, which are often highly biotoxic and difficult to degrade. Even at trace levels, they can cause lethal toxicity, enhanced pathogen resistance, genotoxicity, and endocrine disruption toxicity. Despite biological treatment, drug residues cannot be completely metabolized, and some non-biodegradable toxic substances still exist in the biologically treated wastewater. These pharmaceutical tail waters are directly discharged into the environment, which will not only pollute the ecology but also have adverse effects on the life of organisms. Therefore, intensive treatment must be carried out to achieve harmlessness and reduce environmental risks.

[0003] Catalytic ozone oxidation is widely used in water treatment and is divided into homogeneous and heterogeneous catalytic ozone oxidation. Homogeneous ozone oxidation typically uses dissolved metal ions as catalysts. Although it can efficiently promote the decomposition of ozone to produce hydroxyl radicals through electron transfer, the metal ions are difficult to recover during the reaction and are easily discharged with the treated water, causing secondary pollution. Heterogeneous catalytic ozone oxidation can avoid these shortcomings, offering advantages such as easy separation and recovery of the catalyst, reusability, no risk of secondary metal contamination, high activity, and a high organic matter mineralization rate. Patent CN 105289629 A uses a soft template method to prepare a lanthanum-based perovskite oxide catalyst with a high specific surface area. This catalyst is used in a catalytic ozone oxidation technology system to treat water containing the UV stabilizer PBSA. The catalyst improves the ability of ozone decomposition to produce active free radicals, achieving efficient removal of the organic pollutant PBSA. Patent CN 100835155 B prepares a magnesium titanate catalyst, which is used in a catalytic ozone oxidation system to treat organic wastewater containing at least one of acetic acid, N,N-dimethylformamide, acetophenone, oxalic acid, and toluene. The catalyst has a strong ability to induce ozone decomposition, which can improve ozone utilization and achieve efficient removal of organic pollutants. The catalyst is solid, easy to recycle and transport, and can be reused, saving costs.

[0004] MXene is a new type of two-dimensional material with a graphene-like structure. It has high electrical conductivity, good mechanical strength, and excellent hydrophilicity. Its application in physics, materials science, chemistry, and other fields has also attracted the attention of many scholars. The catalytic activity of MXene materials themselves is low, but due to its flexibility, MXene can easily react with other materials to form composite materials. The unique layered structure of MXene can provide more space or location for nanomaterials, improving their distribution and catalytic performance. Patent CN120026354A prepares a new catalyst by modifying MXene with nitrogen-containing molecules to load Pt single atoms. This catalyst is used in the electrolysis of water and hydrogen evolution system. The nitrogen-containing molecule-modified MXene serves as a carrier and the loaded Pt single atoms serve as active sites, which significantly improves the activity and stability of the catalyst, optimizes the utilization of Pt atoms, and enhances the stability of the catalyst at high current density, resulting in excellent electrochemical performance. Patent CN 120037959 A prepares a copper-nickel single-atom catalyst based on a MXene support through self-assembly and in-situ calcination. The catalyst is used in a diol dehydrogenation cyclization reaction system. The MXene support provides abundant surface active sites. The loaded copper-nickel single atoms serve as active centers. The nitrogen-doped carbon layer serves as a protective layer, significantly improving the catalyst's antioxidant properties and stability. It can achieve high conversion and high selectivity of lactone synthesis, enhance catalyst performance, and extend catalyst life. Carbon nitride is a two-dimensional layered material with electron-rich nitrogen vacancies on its surface and a moderate energy band gap. It has abundant active sites and can be used in the field of catalytic ozone oxidation. Patent CN 106582770 B prepares g-C3N4 by calcining melamine at high temperature, and then reacts it with nano-Zn 0 The powders are mixed, ultrasonically stirred, evaporated, dried, ground and calcined at high temperature to obtain a Zn / g-C3N4 ozone catalyst, which is used to catalyze the ozone oxidation system to treat organic pollutants (such as ATZ). It can completely degrade ATZ in a short time, and the degradation rate constant is 15 times that of ozone oxidation alone. The catalyst has good stability and low metal ion dissolution. At present, researchers have combined carbon nitride with MXene and applied it to multiple fields, showing the broad potential of this composite material. Patent CN 114335458 B prepared Ti3C2T by self-assembly and in-situ calcination. x @g-C3N4 composite material, which is used in lithium metal battery negative electrode system, three-dimensional Ti3C2T xThe skeleton serves as a substrate for lithium metal deposition, and the g-C3N4 layer on the surface serves as a uniform artificial solid electrolyte interface, which can improve the interfacial stability of the lithium metal negative electrode, enhance electrochemical performance, and have excellent cycling stability. Patent CN 118925776A uses urea as a precursor for g-C3N4, which is compounded with MXene during a thermal polymerization process to prepare a g-C3N4 / MXene composite photocatalytic material. This catalyst is applied to a photocatalytic system to treat wastewater containing organic pollutants such as phenol and microorganisms such as Escherichia coli and Staphylococcus aureus, improving the catalytic degradation efficiency and enhancing the antibacterial effect. Currently, most carbon nitride / MXene materials are used in the fields of lithium batteries and photocatalysis, and there are few reports on the use of carbon nitride / MXene materials in catalytic ozone oxidation systems.

[0005] This patent uses carbon nitride to regulate the structural characteristics of MXene and use it in a catalytic ozone oxidation system. The catalyst preparation process is simple, increases the active sites on the MXene surface, increases the interlayer spacing, enhances ozone oxidation, and improves the degradation rate. Summary of the Invention

[0006] The present invention proposes a catalytic ozone oxidation water treatment method in which carbon nitride regulates the structural characteristics of MXene. Taking MXene as the matrix, carbon nitride is introduced through a one-step pyrolysis method to increase the MXene interlayer spacing, increase the carbon defect sites, improve the layer structure ozone molecule transmission capacity, increase the contact area, provide more reaction active sites, accelerate the adsorption and activation of ozone molecules, enhance the ozone oxidation water purification capacity, and achieve efficient oxidation of trace organic matter in pharmaceutical tail water.

[0007] The present invention provides a catalytic ozone oxidation water treatment method for regulating the structural characteristics of MXene by carbon nitride, characterized in that (1) the carbon nitride-regulated MXene catalyst material can be obtained by the following steps: (1) adding 1.6 g of lithium fluoride (LiF) in small amounts and multiple times to a plastic beaker containing 20 mL of 9.0 mol / L hydrochloric acid, and continuously stirring to dissolve it to form an etchant; (2) adding 1.0 g of carbon titanium aluminum (Ti3AlC2) powder in small amounts and multiple times to the above-mentioned etchant, placing it on a heated magnetic stirrer, and reacting it continuously at 50°C and 300 rpm for 5 days; (3) after the reaction is completed, adding ultrapure water to the obtained product, placing it in a centrifuge and repeatedly washing it under centrifugal conditions at 3500 rpm until the pH value of the supernatant is between 4 and 5, removing the supernatant, and obtaining a black solid precipitate. Place in a vacuum drying oven at 60℃ and dry; (4) Place the dried sample in an agate bowl and grind it into fine powder to obtain MXene powder; (5) Weigh 0.5-3g melamine, place it in 20mL ultrapure water, stir it with a magnetic stirrer at 400rpm for 10min, add 0.2-1.0g MXene powder after the melamine is dissolved, and continue stirring for 10min to mix the two evenly; (6) Place the mixed solution obtained in step (5) in an ice water bath and ultrasonicate for 2.0h, then place it in a vacuum freeze dryer and freeze-dry for 36h; (7) Place the dried sample in step (6) in a tubular furnace, heat it to 250-750℃ at a heating rate of 5℃ / min in a nitrogen atmosphere, calcine for 4.0h, and then naturally cool it to room temperature to obtain carbon nitride-controlled MXene;

[0008] The invention is characterized in that (2) a method for treating water by catalyzing ozone oxidation using MXene regulated by carbon nitride is provided, and the steps for completing the application of pharmaceutical tail water treatment are as follows: (1) the concentration of ozone added is 5 to 20 mg / L; (2) the amount of catalyst added is 50 to 200 mg / L; (3) the concentration of trace organic pollutants is 0.025 to 0.2 mmol / L; and (4) the pH value of the reaction system is 4.0 to 10.6.

[0009] The present invention offers the following advantages: It proposes a catalytic ozone oxidation water treatment method that utilizes carbon nitride to modulate the structural properties of MXene. This method modulates the structural properties of MXene using carbon nitride, increasing the active sites and interlayer spacing on the MXene surface, improving the transmission efficiency and contact area of ​​ozone molecules, accelerating ozone adsorption and activation, and promoting ozone decomposition to produce active species, thereby achieving efficient degradation of trace organic matter in pharmaceutical tail water. Furthermore, the catalyst preparation process is simple and environmentally friendly, and as a solid catalyst, it is easily recyclable, reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1This is a scanning electron microscope image of the CN / MXene-1:2(550) material prepared in the present invention;

[0011] Figure 2 XRD patterns of CN / MXene materials prepared in the present invention at different melamine and MXene addition ratios and at different calcination temperatures;

[0012] Figure 3 Raman spectra of CN / MXene materials prepared by the present invention at different melamine and MXene addition ratios and at different calcination temperatures;

[0013] Figure 4 ESR spectra of MXene, g-C3N4, and CN / MXene-1:2(550) materials prepared in this invention

[0014] Figure 5 This is a graph showing the degradation effect of ibuprofen (IBP) on the CN / MXene materials prepared in the present invention at different melamine and MXene addition ratios and at different calcination temperatures in a catalytic ozone oxidation system;

[0015] Figure 6 The CN / MXene-1:2(550) material prepared in the present invention is applied to the catalytic ozone oxidation system, and the degradation effect diagram of ibuprofen (IBP) under different ozone concentration conditions is shown. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0017] Example 1 Preparation method of MXene material regulated by carbon nitride

[0018] The material can be obtained by the following steps: (1) adding 1.6 g of lithium fluoride (LiF) in small amounts and multiple times to a plastic beaker containing 20 mL of 9.0 mol / L hydrochloric acid, and continuously stirring to dissolve it to form an etchant; (2) adding 1.0 g of carbon titanium aluminum (Ti3AlC2) powder in small amounts and multiple times to the above-mentioned etchant, placing it on a heated magnetic stirrer, and reacting it continuously at 50°C and 300 rpm for 5 days; (3) after the reaction is completed, adding ultrapure water to the obtained product, placing it in a centrifuge and repeatedly washing it at 3500 rpm until the pH value of the supernatant is between 4 and 5, removing the supernatant, obtaining a black solid precipitate, and then drying it in a vacuum drying oven at 60°C; (4) placing the dried sample in an agate bowl The MXene powder is obtained by grinding the melamine into a fine powder in the body; (5) weighing 0.5-3 g of melamine, placing it in 20 mL of ultrapure water, stirring it at 400 rpm with a magnetic stirrer for 10 min, adding 0.2-1.0 g of MXene powder thereto after the melamine is dissolved, and continuing to stir for 10 min to mix the two evenly; (6) placing the mixed solution obtained in step (5) in an ice water bath for 2.0 h, and then placing it in a vacuum freeze dryer for freeze drying for 36 h; (7) placing the powdered sample after drying in step (6) in a tube furnace, heating it to 250-750 ° C at a heating rate of 5 ° C / min in a nitrogen atmosphere, calcining it for 4.0 h, and then naturally cooling it to room temperature after the end to obtain carbon nitride-controlled MXene;

[0019] Depend on Figure 1 It can be seen that the material (CN / MXene-1:2(550)) successfully prepared by this method and calcined at 550 °C with melamine and MXene in a 1:2 ratio exhibits an accordion-like two-dimensional layered structure. Figure 2 It can be seen that the (002) characteristic peak of MXene material shows that MXene is successfully prepared, and the (002) characteristic peak of MXene shifts to the left after carbon nitride regulation. According to the Bragg formula, the interlayer spacing of MXene increases from 1.20nm to 1.41nm, which is beneficial to the transmission of ozone molecules and increases the contact area between ozone and catalyst. Figure 3 It can be seen that the Raman spectroscopy of carbon nitride-controlled MXene is higher than that of uncontrolled MXene. D / I G The value increases from 0.87 to 1.23, indicating that the carbon defects increase and the surface of the material provides more active sites. Figure 4 It can be seen that after carbon nitride regulation, the ESR signal is significantly enhanced. The surface vacancies of the MXene material after regulation increase by 47.07 times compared with the unregulated MXene and by 2.58 times compared with the single g-C3N4, indicating that more defect sites are generated, which is conducive to the adsorption and activation of ozone. Figure 5 It can be seen that the material (CN / MXene-1:2(550)) prepared with the added melamine and MXene ratio of 1:2 and the calcination temperature of 550 °C has the best catalytic performance, and the removal rate of ibuprofen increased from 60.0% to 90.1%.

[0020] Example 2 Carbon nitride-regulated MXene materials for catalytic ozone oxidation deep treatment of pharmaceutical tail water

[0021] The process flow for the advanced treatment of residual drugs in pharmaceutical tail water is as follows: pharmaceutical wastewater - screen - grit chamber primary sedimentation tank - biochemical tank - secondary sedimentation tank - catalytic ozone oxidation advanced treatment - ceramic membrane separation - disinfection - effluent. Pharmaceutical wastewater flows by gravity into the screen well, intercepts coarse suspended solids, and enters the grit chamber for further removal of fine particles. After treatment in the primary sedimentation tank, biochemical tank, and secondary sedimentation tank, the wastewater enters the ozone contact tank. The carbon nitride-controlled MXene powder ozone catalyst of the present invention is used as a catalyst for efficient catalytic ozone decomposition. Under the conditions of an ozone concentration of 5-20 mg / L, a catalyst dosage of 50-200 mg / L, a trace organic pollutant concentration of 0.025-0.2 mmol / L, a reaction system pH of 4.0-10.6, and a reaction contact time of 30 minutes, the pharmaceutical tail water is subjected to advanced treatment. The active oxygen species generated in the system degrade organic pollutants, improving the biodegradability of the wastewater. The ceramic membrane process is then used for mud and water separation, and the separated water is disinfected and discharged in compliance with the standards.

[0022] Depend on Figure 6 It can be seen that when the concentration of the introduced oxygen is 10 mg / L, the removal effect of ibuprofen is the best, and its removal rate increases from 28.0% to 90.1%. The increase of ozone will increase the generation of reactive oxygen species in the reaction solution, but excessive ozone may quench the formed reactive oxygen, thereby inhibiting the reaction.

[0023] The specific embodiments described above are only preferred implementations of the present invention, but other aspects and implementations will be obvious to those skilled in the art. Without departing from the principles of the present invention, several variations and improvements may be made, all of which fall within the scope of protection of this application.

Claims

1. A catalytic ozone oxidation water treatment method using carbon nitride to regulate the structural properties of MXene, characterized in that: Using MXene as the matrix, carbon nitride is introduced through a one-step pyrolysis method to increase the MXene interlayer spacing, improve defect sites, enhance the ozone molecule transmission capacity of the layer structure, increase the contact area, provide more reactive sites, accelerate the adsorption and activation of ozone molecules, and enhance the ozone oxidation water purification capacity. The specific process steps are as follows: (1) Add 1.6 g of lithium fluoride (LiF) to 20 mL of 9.0 mol / L hydrochloric acid and continue stirring to dissolve it to form an etchant; (2) 1.0 g of titanium aluminum carbide (Ti3AlC2) powder was added to the above-mentioned etchant and reacted at 50°C and 300 rpm for 5 days; (3) After the reaction, the product was repeatedly washed with ultrapure water until the pH value of the supernatant was between 4 and 5. The supernatant was removed to obtain a black solid precipitate, which was then dried in a vacuum drying oven at 60°C. (4) The dried sample is placed in an agate bowl and ground into fine powder to obtain MXene powder; (5) Weigh 0.5-3 g of melamine, place it in 20 mL of ultrapure water, and stir at 400 rpm for 10 min. After the melamine is dissolved, add 0.2-1.0 g of MXene powder and continue stirring for 10 min to mix the two evenly. (6) The mixed solution obtained in step (5) was placed in an ice-water bath and ultrasonicated for 2.0 h, and then placed in a vacuum freeze dryer and freeze-dried for 36 h; (7) The dried sample in step (6) was placed in a tube furnace, heated to 250-750°C at a heating rate of 5°C / min under a nitrogen atmosphere, and calcined for 4.0 h. After the calcination, it was naturally cooled to room temperature to obtain carbon nitride-regulated MXene; (8) The obtained carbon nitride-regulated MXene exhibits an accordion-like two-dimensional layered structure, and the interlayer spacing increases from about 1.20 nm to about 1.41 nm. Raman I D / I G The value increased from 0.87 to 1.23, pH pzc =10.47, when pH is between 2.5 and 9.8, the Zeta potential is 7.97 to -35.43 mV, and the surface vacancies increase by 2.58 to 47.07 times; (9) The carbon nitride-controlled MXene prepared in step (7) is applied to the catalytic ozone oxidation deep treatment of pharmaceutical tail water. The process flow is pharmaceutical wastewater-grit-sand tank primary sedimentation tank-biochemical tank-secondary sedimentation tank-catalytic ozone oxidation deep treatment-ceramic membrane separation-disinfection-effluent. During the catalytic ozone oxidation deep treatment process, the ozone addition concentration is 5-20 mg / L, the catalyst dosage is 50-200 mg / L, the trace organic pollutants are 0.025-0.2 mmol / L, and the pH value of the reaction system is 4.0-10.6, which can achieve a removal rate of 28-100% of the trace organic pollutants in the pharmaceutical tail water.

Images