A kind of carbon nanotube material of nitrogenization of biochar limited enhancement of ozone catalytic oxidation cooperates with photocatalysis and preparation method

Abstract

The application discloses a kind of carbon catalytic oxidation of ozone cooperates with photocatalysis and restricts enhancement carbon nitride nanotube material of biochar, mainly by alkali modification green algae base biochar and functional group doped carbon nitride nanotube is made, wherein functional group doped carbon nitride nanotube is melamine, cyanuric acid as raw material, by urea, N-acetyl ethanolamine, potassium thiocyanate, ammonium chloride, N, N-dimethylformamide, N, N-dimethylacetamide one and multiple functional group doping is prepared.The above-mentioned material has adsorption, ozone catalytic oxidation, visible light photocatalysis and ozone catalytic oxidation cooperates with visible light photocatalytic activity, can be applied to water pollution control field.The material provided in the application is made of non-metal material, without secondary pollution, simple process, without high temperature and high pressure and other special environment, raw material quantity is easy to obtain, low in cost, its application ozone catalytic oxidation cooperates with photocatalysis system can be used as a kind of new technology to promote water pollution treatment process.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to a biochar-confined enhanced carbon nitride nanotube material for ozone catalytic oxidation and synergistic photocatalysis, and its preparation method. Background Technology

[0002] With the increasing complexity of wastewater quality and growing societal emphasis on the treatment of new pollutants, traditional water pollution control technologies are increasingly unable to meet emission requirements. Ozone catalytic oxidation technology is widely used in water pollution control due to its low cost, small footprint, and high efficiency. However, its limitations—low mineralization rate upon direct application and rapid reaction only in alkaline water bodies—make it difficult to meet increasingly stringent effluent quality requirements. Therefore, upgrading ozone catalytic oxidation technology through high-energy, low-consumption methods has become a key focus and challenge in improving water pollution control effectiveness under the background of carbon emission reduction.

[0003] Utilizing visible light, which accounts for 43% of sunlight, is a crucial step towards clean energy in water pollution control technologies. Visible light photocatalysis technology boasts advantages such as low energy consumption and no secondary pollution, but its application still faces limitations including low reaction rates and low light utilization. Synergistically combining ozone catalytic oxidation technology with visible light photocatalysis technology using catalytic materials can rapidly and thoroughly degrade pollutants while reducing costs without generating secondary pollution.

[0004] Carbon nitride nanotubes possess potential for ozone catalytic oxidation and visible light photocatalysis, but they still suffer from drawbacks such as high recombination rates of photogenerated carriers, limited specific surface area, and poor adsorption effects. Therefore, modification is needed to improve the practicality of carbon nitride nanotube materials. While methods for modifying carbon nitride nanotubes solely through elemental doping or composite modification have been reported, there are no reports of methods that utilize only non-metallic materials for modification. Specifically, this approach first modulates the surface properties of carbon nitride nanotubes through functional group doping, and then enhances their three-phase mass transfer and catalytic effects by confining them with biochar. Summary of the Invention

[0005] To address the shortcomings of existing water pollution treatment technologies and the scarcity of catalytic materials for ozone catalytic oxidation synergistic photocatalysis, this paper provides a biochar-confined enhanced carbon nitride nanotube material for ozone catalytic oxidation synergistic photocatalysis and its preparation method. By using only non-metallic materials for amide modification and biochar confinement enhancement, the catalytic activity and three-phase mass transfer of the carbon nitride nanotube material are improved, thereby upgrading the traditional ozone catalytic oxidation process, improving the water pollution treatment effect while promoting energy conservation and emission reduction.

[0006] This invention employs the following technical solution: a biochar-confined enhanced carbon nitride nanotube material for ozone catalytic oxidation and synergistic photocatalysis, and its preparation method. The preparation steps of this method are as follows:

[0007] S1. Preparation of alkali-modified green algae-based biochar:

[0008] After grinding and sieving the green algae biomass, it is mixed evenly with alkali in an aqueous solution at a certain mass ratio and soaked. After drying, it is heated under a nitrogen atmosphere to obtain the alkali-modified product. After post-treatment, it is dried to obtain alkali-modified green algae-based biochar.

[0009] S2. Preparation of functional group-doped carbon nitride nanotubes:

[0010] Melamine and cyanuric acid were dissolved and mixed in a certain molar ratio, and an acyl dopant was added in a certain molar ratio. The precursor of functional group-doped carbon nitride nanotubes was obtained by hydrothermal reaction. After drying the precursor, the precursor was calcined under a nitrogen atmosphere to obtain functional group-doped carbon nitride nanotubes.

[0011] S3. Preparation of biochar-confined reinforced carbon nitride nanotube materials:

[0012] A certain mass ratio of alkali-modified green algae-based biochar and functional group-doped carbon nitride nanotubes were dispersed in an aqueous solution and mixed. The mixture was dried to obtain a confined reinforcement precursor. The precursor was then calcined under a nitrogen atmosphere to obtain biochar-confined reinforced carbon nitride nanotubes.

[0013] Furthermore, in step S1, the specific steps for grinding and sieving the green algae biomass are as follows: after washing and drying the green algae-based biomass, grind it into powder, and then pass the obtained powder through a 100-mesh sieve for later use.

[0014] Furthermore, in step S1, the specific post-processing steps are as follows: the alkali-modified product is added to 1 mol / L hydrochloric acid for acid soaking for 1-3 hours, then acid boiled for 1-3 hours, naturally cooled, washed with ethanol 3-5 times, and finally washed with deionized water until the solution is neutral.

[0015] Optionally, the green algae biomass in step S1 is one or more of seaweed, laver, and various mixed green algae, and the alkali is one or more of potassium hydroxide, sodium carbonate, sodium bicarbonate, and potassium thiocyanate. The mass ratio of green algae-based biomass to alkali is 1:1 to 1:6, and the soaking time is 4-12 hours.

[0016] Optionally, in steps S1, S2, and S3, the nitrogen flow rate is 2-5 mL / min, and the heating rate is 2-15 °C / min.

[0017] Optionally, in step S1, the heating reaction temperature is 450-750℃ and the heating reaction time is 1-5h; in step S2, the calcination reaction temperature is 400-600℃ and the calcination reaction time is 2-6h; in step S3, the calcination reaction temperature is 200-500℃ and the calcination reaction time is 1-3h.

[0018] Optionally, in step S2, the molar ratio of melamine to cyanuric acid is 0.5:1.5-1.5:0.5, and 0.0-0.05 mol of dopant is added to every 1 mol of melamine and cyanuric acid. The dopant includes one or more of urea, N-acetylethanolamine, potassium thiocyanate, ammonium chloride, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0019] Optionally, in step S2, the hydrothermal reaction temperature is 140-220℃ and the hydrothermal reaction time is 12-18h.

[0020] Optionally, in step S3, the volume ratio of alkali-modified green algae-based biochar to amide-modified carbon nitride nanotube material is 6:1 to 1:1.

[0021] Beneficial effects: This invention provides a biochar-confined enhanced carbon nitride nanotube material with ozone catalytic oxidation and synergistic photocatalytic activity, and its preparation method for water pollution treatment. This method has the following advantages:

[0022] S1. Biochar confined enhanced carbon nitride nanotube material is made only from non-metallic materials and will not produce secondary pollution. Green algae is a raw material that is readily available in large quantities and at low cost. It can also effectively deal with environmental pollution caused by the decay of green algae. The material synthesis process does not require special conditions such as high pressure and the synthesis conditions are mild.

[0023] S2. Biochar-confined enhanced carbon nitride nanotubes have ozone catalytic oxidation, visible light photocatalysis and adsorption activities, and can simultaneously meet the application requirements of ozone catalytic oxidation, visible light photocatalysis, adsorption and ozone catalytic oxidation synergistic photocatalytic systems.

[0024] S3. Biochar-confined enhanced carbon nitride nanotube materials are used in ozone catalytic oxidation synergistic photocatalytic systems for water pollution control. They can effectively combine the advantages of ozone catalytic oxidation system's fast reaction speed and the clean and pollution-free photocatalytic active system. At the same time, the active components of the two systems are synergistic, reducing reaction selectivity, improving the mineralization effect on difficult-to-treat pollutants, especially new pollutants, and showing good adaptability to complex water quality.

[0025] S4. Based on the wide application of ozone catalytic oxidation system and the low cost and ease of operation of visible light photocatalytic system, ozone catalytic oxidation synergistic photocatalytic system has a good foundation for implementation and is conducive to practical promotion and application. Attached Figure Description

[0026] Figure 1 This is a flowchart of the preparation method provided in the embodiments of the present invention;

[0027] Figure 2Scanning electron microscope image of biochar-confined enhanced carbon nitride nanotube material provided in an embodiment of the present invention;

[0028] Figure 3 The removal efficiency of different biochar-confined enhanced carbon nitride nanotube materials provided in Examples 1-4 of this invention for the new pollutant PNP in an ozone catalytic oxidation synergistic photocatalytic system;

[0029] Figure 4 The biochar confined enhanced carbon nitride nanotube material provided in Example 4 of this invention is shown to remove the new pollutant PNP in ozone catalytic oxidation system, visible light photocatalytic system and ozone catalytic oxidation synergistic photocatalytic system. Detailed Implementation

[0030] The advantages and effects of the present invention will be further illustrated below through specific implementation methods.

[0031] Unless otherwise specified, the terms used in this invention should be understood in the usual sense in the art.

[0032] Unless otherwise specified, all raw materials, reagents, equipment, instruments and other materials used in this invention can be obtained by purchasing them from the market or by existing methods.

[0033] The technical solution of the embodiments of this invention is to solve the above problems, and the overall idea is as follows:

[0034] Alkali-modified chlorophyll-based biochar possesses a large specific surface area and excellent pollutant adsorption capacity. By altering the surface electrostatic potential of carbon nitride nanotubes through functional group doping, and further enhancing the functional group-doped carbon nitride nanotubes through confined reinforcement with alkali-modified chlorophyll-based biochar, a biochar-confined reinforced carbon nitride nanotube material for ozone catalytic oxidation is obtained, exhibiting enhanced three-phase mass transfer, ozone catalytic oxidation, photocatalysis, and synergistic photocatalytic activity. This material is then used in ozone catalytic oxidation, photocatalysis, and synergistic photocatalytic ozone catalytic oxidation systems for water pollution treatment.

[0035] Example 1: Preparation method of biochar-confined reinforced carbon nitride nanotube materials

[0036] The mixed biomass of seaweed and seaweed was washed with deionized water, dried, and ground through a 100-mesh sieve to obtain green algae biomass powder. The powder was washed with water, centrifuged and dried, and then heated under a nitrogen atmosphere (2 mL / min) to obtain the heated product. The heating temperature was 650℃ and the heating time was 2 h (5℃ / min). The heated product was washed with ethanol three times and finally washed with deionized water until the solution was neutral to obtain green algae-based biochar.

[0037] Melamine and cyanuric acid (molar ratio 1:1) were dissolved in aqueous solutions respectively. The two solutions were slowly mixed evenly. The mixture was then added to a hydrothermal reactor and hydrothermally reacted at 180°C for 16 hours to obtain carbon nitride nanotube precursor. After drying the precursor, it was calcined at 520°C for 4 hours (2°C / min) under a nitrogen atmosphere (2 mL / min) to obtain carbon nitride nanotubes.

[0038] The prepared green algae-based biochar and carbon nitride nanotubes were mixed evenly in an aqueous solution at a mass ratio of 4:1 and then dried to obtain a confined reinforcement precursor. The precursor was calcined at 300℃ for 1 h (5℃ / min) under a nitrogen atmosphere (2 mL / min) to obtain biochar confined reinforcement carbon nitride nanotube material.

[0039] Example 2: Preparation method of biochar-confined reinforced carbon nitride nanotube materials

[0040] The difference between this embodiment and Example 2 is that the preparation method of biochar is different. The mixed biomass of seaweed and algae was washed with deionized water, dried, and ground through a 100-mesh sieve to obtain green algae biomass powder. It was mixed with potassium hydroxide in an aqueous solution at a mass ratio of 1:2 and soaked for 10 hours. The powder was centrifuged and dried, and then heated under a nitrogen atmosphere (2 mL / min) to obtain an alkali-modified product. The heating temperature was 650℃ and the heating time was 2 hours (5℃ / min). The alkali-modified product was added to 1 mol / L hydrochloric acid for acid soaking for 1 hour and then acid boiled for 1 hour. After natural cooling, it was washed three times with ethanol and finally washed with deionized water until the solution was neutral to obtain alkali-modified green algae-based biochar.

[0041] The prepared alkali-modified green algae-based biochar and the carbon nitride nanotubes described in Example 1 were used to prepare biochar-confined reinforced carbon nitride nanotube materials according to the method described in Example 1.

[0042] Example 3: Preparation method of biochar-confined reinforced carbon nitride nanotube materials

[0043] The difference between this embodiment and Example 2 lies in the preparation method of carbon nitride nanotubes and the composite method of algae-based alkali-modified biochar and carbon nitride nanotubes. Melamine and cyanuric acid (molar ratio 1:1) were dissolved separately in aqueous solutions. After the two solutions were slowly mixed evenly, 0.03 and 0.05 mol of potassium thiocyanate and ammonium chloride were added to each 1 mol of melamine and cyanuric acid and mixed evenly. The mixture was added to a hydrothermal reactor and hydrothermally reacted at 180°C for 16 h to obtain a functional group-doped carbon nitride nanotube precursor. After drying the precursor, it was calcined at 520°C for 4 h (2°C / min) under a nitrogen atmosphere (2 mL / min) to obtain functional group-doped carbon nitride nanotubes.

[0044] The alkali-modified green algae-based biochar described in Example 2 and the functional group-doped carbon nitride nanotubes described in this example were mixed evenly in an aqueous solution at a mass ratio of 4:1 and then dried to obtain a confined reinforcement precursor. The precursor was calcined at 450°C for 1 h (5°C / min) under a nitrogen atmosphere (2 mL / min) to obtain biochar-confined reinforced carbon nitride nanotube material.

[0045] Example 4: Preparation method of biochar-confined reinforced carbon nitride nanotube materials

[0046] The difference between this embodiment and Example 2 is that the preparation method of carbon nitride nanotubes is different. Melamine and cyanuric acid (molar ratio 1:1) are dissolved in aqueous solutions respectively. After the two solutions are slowly mixed evenly, 0.002 mol of N,N-dimethylacetamide is added to each 1 mol of melamine and cyanuric acid and mixed evenly. The above mixture is added to a hydrothermal reactor and hydrothermally reacted at 180°C for 16 h to obtain a functional group-doped carbon nitride nanotube precursor. After drying the precursor, it is calcined at 520°C for 4 h (2°C / min) under a nitrogen atmosphere (2 mL / min) to obtain functional group-doped carbon nitride nanotubes.

[0047] Biochar-confined reinforced carbon nitride nanotube material was prepared by combining the alkali-modified green algae-based biochar described in Example 2 with the functional group-doped carbon nitride nanotubes described in this example, as described in Example 1.

[0048] Experimental Example 1

[0049] The materials prepared in Examples 1-4 were tested, with persistent organic pollutant (PNP) among the new pollutants as the target pollutant. The activity of the above materials in the COP system after slow adsorption was tested, and the results are as follows. Figure 3 As shown.

[0050] Depend on Figure 3 It can be seen that the materials prepared in Examples 1-4 have different reactivity. Among them, the material prepared in Example 1 has weaker PNP removal activity than the materials prepared in Examples 2-4, with an adsorption removal rate of 32.2% for PNP after 3 min and only 42.1% after 30 min. The material prepared in Example 2 has a significantly improved PNP removal rate, with a PNP removal rate of 80.3% after 30 min. The materials prepared in Examples 3 and 4 both have good PNP removal effects, with Example 4 having the best PNP removal effect, with a PNP removal rate of 94.1% after 30 min.

[0051] Experiment Example 2

[0052] The material obtained in Example 4 was tested. The experiment used persistent organic pollutant PNP as the target pollutant, and its activity in ozone catalytic oxidation, visible light photocatalysis, and ozone catalytic oxidation synergistic photocatalysis systems was tested after slow adsorption. The results are as follows: Figure 4 As shown.

[0053] Depend on Figure 4 It can be seen that the material prepared in Experimental Example 4 has rapid adsorption performance, and the adsorption rate of PNP can reach 82.5% in 3 minutes. At the same time, it has ozone catalytic oxidation, visible light photocatalysis and ozone catalytic oxidation synergistic visible light photocatalytic activity. In the above three systems, the degradation rate of PNP can reach 90.5%, 90.2% and 94.1% respectively in 30 minutes.

[0054] The results of Experiments 1-2 show that the alkali-modified biochar confined enhanced functional group-doped carbon nitride nanotube material prepared in Example 4 has the best adsorption and catalytic activity.

[0055] The applicant declares that the above embodiments are used to illustrate the detailed operation and process flow of the present invention, but are not limited to the above detailed operation and process flow. Those skilled in the art should understand that equivalent substitutions of raw materials and processes, additions of auxiliary components, and selection of specific methods for the products of the present invention all fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing biochar-confined enhanced carbon nitride nanotube materials for ozone catalytic oxidation and synergistic photocatalysis, characterized in that, The ozone catalytic oxidation synergistic photocatalysis includes using biochar-confined enhanced carbon nitride nanotube materials for ozone catalytic oxidation in water pollution control, or for visible light photocatalysis in water pollution control, or for ozone catalytic oxidation synergistic photocatalysis in water pollution control; the preparation method of the biochar-confined enhanced carbon nitride nanotube materials for ozone catalytic oxidation synergistic photocatalysis includes the following steps: S1. Preparation of alkali-modified green algae-based biochar: After grinding and sieving the green algae biomass, it is mixed evenly with alkali in an aqueous solution at a certain mass ratio and soaked. After drying, it is heated under a nitrogen atmosphere to obtain the alkali-modified product. After post-treatment, it is dried to obtain alkali-modified green algae-based biochar. In step S1, the green algae-based biomass is seaweed and algae, and the alkali includes one or more of potassium hydroxide, sodium carbonate, and sodium bicarbonate. The mass ratio of green algae biomass to alkali is 1:1 to 1:6, and the soaking time is 4-12 h. S2. Preparation of functional group-doped carbon nitride nanotubes: Melamine and cyanuric acid were dissolved and mixed in a certain molar ratio, and a certain volume of dopant was added. After hydrothermal reaction, a functional group-doped carbon nitride nanotube precursor was obtained. After drying the precursor, it was calcined under a nitrogen atmosphere to obtain functional group-doped carbon nitride nanotubes. In step S2, the molar ratio of melamine to cyanuric acid is 0.5:1.5-1.5:0.5, the dopant is N,N-dimethylacetamide, and 0.002 mol of dopant is added to every 1 mol of melamine and cyanuric acid. In step S2, the hydrothermal reaction temperature is 140-220℃, the hydrothermal reaction time is 12-18 h, the nitrogen flow rate is 2-5 mL / min, the calcination reaction temperature is 400-600℃, the heating rate is 2-15℃ / min, and the calcination reaction time is 2-6 h. S3. Preparation of biochar-confined reinforced carbon nitride nanotube materials: A certain mass ratio of alkali-modified green algae-based biochar and functional group-doped carbon nitride nanotubes were dispersed in an aqueous solution and mixed. The mixture was dried to obtain a confined reinforcement precursor. The precursor was calcined under a nitrogen atmosphere to obtain biochar-confined reinforced carbon nitride nanotubes. In step S3, the volume ratio of alkali-modified green algae-based biochar to functional group-doped carbon nitride nanotube material is 6:1 to 1:

1.

2. The preparation method according to claim 1, characterized in that: In step S1, the nitrogen flow rate is 2-5 mL / min, the heating reaction temperature is 450-750℃, the heating rate is 2-15℃ / min, and the heating reaction time is 1-5 h.

3. The preparation method according to claim 1, characterized in that: In step S1, the post-treatment includes acid soaking in 1-5 mol / L hydrochloric acid for 1-3 h, acid boiling for 1-3 h, alcohol washing 3-5 times, and water washing until the solution is neutral.

4. The preparation method according to claim 1, characterized in that: In step S3, the nitrogen flow rate is 2-5 mL / min, the calcination reaction temperature is 200-500℃, the heating rate is 2-15℃ / min, and the calcination reaction time is 1-3 h.

5. The biochar-confined enhanced carbon nitride nanotube material for ozone catalytic oxidation and synergistic photocatalysis prepared by the method according to any one of claims 1-4, characterized in that: The biochar-confined enhanced carbon nitride nanotube material used for ozone catalytic oxidation and photocatalysis is used for ozone catalytic oxidation in water pollution control, or for visible light photocatalysis in water pollution control, or for ozone catalytic oxidation and photocatalysis in water pollution control.

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