A method for preparing a highly efficient and reusable fibrous mesh carbon-nitrogen composite adsorbent (Cg-C3N4)

Abstract

This invention discloses a method for preparing a highly efficient and reusable fibrous network carbon-nitrogen composite adsorbent (C-g-C3N4). The material is prepared by the following method: First, cellulose is extracted from natural poplar leaves using delignification. Then, the cellulose network obtained from a copper ammonia and sulfuric acid solution is carbonized in a tube furnace, and oxygen is introduced to increase the oxygen-containing functional groups on the surface of the cellulose carbon network. After oxidation treatment, appropriate amounts of acids, amines, aldehydes, ketones, etc., are added to a hydrothermal reactor to functionalize the surface of the cellulose carbon network. Finally, the surface-modified cellulose carbon network is applied to adsorption experiments. The sample with the best activity is heated and self-assembled with different precursors of g-C3N4 (urea, dicyandiamide, melamine), and the composite precursors are then polymerized by thermochemical methods to obtain the final composite carbon-nitrogen material. This invention also provides the application of the product obtained by the above preparation method in the field of phenol and hydroquinone adsorption. Experimental results show that the product prepared by this invention, as an adsorbent, has the advantages of high adsorption capacity, simple desorption and reusability.

Description

Technical Field

[0001] This invention relates to a method for preparing a highly efficient and reusable fibrous mesh carbon-nitrogen composite adsorbent (Cg-C3N4), which utilizes raw materials such as poplar leaves, sodium chlorite, urea, dicyandiamide, and melamine, and belongs to the technical field of preparation of highly efficient and reusable adsorbents. Background Technology

[0002] Biomass, with its abundant reserves and low price, is considered the most promising alternative energy source to fossil fuels. Increasing the use of biomass can extend the lifespan of crude oil, contributing to sustainable development. It can also ensure the production of products that must use petroleum as a raw material while reducing the increase in atmospheric CO2 concentration. Furthermore, utilizing biomass to produce carbon materials is an effective way to utilize biomass energy. Carbon materials derived from biomass have abundant functional groups on their surface, which offers significant advantages in wastewater treatment and pollutant remediation reactions.

[0003] However, due to the complex composition of natural biomass, the stability of the prepared adsorbents may decrease. In such cases, extracting components from biomass is an effective method. Therefore, the cellulose raw material used in this invention is obtained from natural poplar leaves through repeated heating and washing with solutions such as sodium chlorite to remove lignin and hemicellulose. Furthermore, while the adsorption activity of activated carbon prepared in recent years has significantly improved, it is difficult to recycle this activated carbon after adsorbing pollutants. Solvent desorption requires substantial investment and has a relatively low removal rate. Therefore, current adsorbents are generally used only once and not recycled. This results in significant waste and increases the cost of using adsorbents for wastewater treatment. Therefore, developing composite adsorbents that can be efficiently recycled is key to solving this problem.

[0004] Utilizing a composite adsorbent of biomass carbon and g-C3N4 can efficiently adsorb pollutants while leveraging the photocatalytic activity of g-C3N4 itself to degrade them, achieving effective desorption of adsorbed pollutants. Furthermore, the use of urea, dicyandiamide, and melamine as raw materials offers low cost and high economic benefits. Therefore, designing and developing a method for preparing a highly efficient and reusable fibrous mesh carbon-nitrogen composite adsorbent (Cg-C3N4) is of great value. Summary of the Invention

[0005] This invention provides a method for preparing a highly efficient and reusable fibrous network carbon-nitrogen composite adsorbent (Cg-C3N4) using cellulose raw material extracted from poplar leaves. First, lignin and hemicellulose are removed by repeated heating and washing with a solution such as sodium chlorite to obtain the cellulose raw material. Then, a colorless cellulose network is carbonized in a cuprammonium solution, and oxygen is introduced during the carbonization process to increase the oxygen-containing functional groups on the surface of the carbonized cellulose network. Next, the obtained cellulose carbon network undergoes hydrothermal surface modification to further improve its surface properties and thus enhance its adsorption activity. Finally, the cellulose carbon network and the g-C3N4 precursor are composited and thermally polymerized via self-assembly to obtain the highly efficient and reusable fibrous network carbon-nitrogen composite adsorbent (Cg-C3N4).

[0006] This invention proposes a method for preparing a highly efficient and reusable fibrous mesh carbon-nitrogen composite adsorbent (Cg-C3N4), comprising the following steps:

[0007] (1) The obtained cellulose was washed three times with deionized water, and then dried and placed in a prepared copper ammonia solution. The solution was stirred for 4 to 16 hours under water bath heating at 50°C to completely dissolve the cellulose in the solution.

[0008] (2) The viscous liquid containing dissolved cellulose is injected into the sulfuric acid solution through a syringe. As the pH decreases, the cellulose copper ammonia complex will form solidified fibers again. After a period of time, the solution will wash away the blue copper salt in the artificial fiber, and finally a colorless cellulose web is obtained.

[0009] (3) The obtained cellulose web is spread out in a long strip crucible and placed in a tube furnace for carbonization. The atmosphere is a mixture of oxygen and nitrogen gas, with an oxygen ratio of 0.1% to 21%. The introduction of oxygen is to increase the oxygen-containing functional groups on the surface of the carbonized cellulose web. The carbonization temperature is 150℃ to 550℃, and the heating rate is 1℃ / min to 20℃ / min. The carbonization process is carried out with a relatively long holding time to improve the degree of carbonization of the cellulose web. The holding time is 0.5h to 15h.

[0010] (4) The obtained cellulose mesh was placed in a hydrothermal reactor for surface functionalization treatment. Appropriate amounts of acetic acid, ammonium acetate, ammonium formate, furfural, acetone, etc. were added to the hydrothermal reactor to modify the cellulose mesh, introducing functional groups such as carboxyl, amino, aldehyde, and ketone groups on the carbon surface of the cellulose mesh. The ratio of the modifying reagent to cellulose carbon was 0.1~5:1, the hydrothermal treatment temperature was 50℃~200℃, and the hydrothermal treatment time was 0.5h~72h. After hydrothermal treatment, the sample was washed multiple times with deionized water and ethanol, then redispersed in deionized water, ultrasonically dispersed evenly, and then transferred to a pear-shaped flask.

[0011] (5) After the surface-modified cellulose carbon network is evenly dispersed with urea, dicyandiamide and melamine (precursor of g-C3N4), it is added into a pear-shaped flask for self-assembly. The solvent is a mixture of water and ethanol in a ratio of 1:0.1~5. The heating temperature is 60~200 degrees. After reacting for 1~24 hours, the mixture is dried by rotary evaporation until the water is evaporated. The powder is then removed with a scraper for later use.

[0012] (6) The composite precursor is further polymerized into a composite carbonitride material (Cg-C3N4) by thermochemical method, and calcined in air and nitrogen atmosphere at 500~600℃ for 1~5h respectively. The calcined sample is then ground for later use.

[0013] (7) Adsorption experiments selected phenol and hydroquinone, common drug molecules in wastewater. The results showed that the composite Cg-C3N4 adsorbent could effectively adsorb phenol and hydroquinone using its network structure. After adsorption for a period of time, the adsorbed pollutants could be decomposed by irradiation with a xenon lamp for a few hours, thus achieving reuse.

[0014] To test the reactivity of the adsorbents in this invention, a constant-temperature shaker and a UV spectrophotometer were used. The fibrous network carbon-nitrogen composite material (Cg-C3N4) was used as the adsorbent, water as the dispersant, the reaction temperature was 25°C, and the concentration of the aqueous solutions of phenol, p-chlorophenol, and hydroquinone was 10-200 mg / L. The adsorption capacity was measured using a UV spectrophotometer; the lower the residual rate of the adsorbed substances, the better the adsorption performance of the composite material. Testing showed that the fibrous network biochar prepared in this patent maintained a good filamentous morphology even when carbonized at 7% oxygen content. In hydrothermal modification, the biochar exhibited the best phenol adsorption performance after treatment with acetic acid at 80°C for 24 hours, with an adsorption capacity reaching 92 mg / g. Subsequently, the fibrous network carbon-nitrogen composite material (Cg-C3N4) obtained after compounding with urea and calcining at 550°C for 2 hours showed the best phenol adsorption performance and photodegradation effect, with an adsorption capacity reaching 117.6 mg / g. Furthermore, the fiber-reinforced carbon-nitrogen composite material (Cg-C3N4) prepared in this invention still exhibits a phenol adsorption capacity of 104 mg / g after being reused four times, making it an excellent reusable and highly efficient phenol adsorbent.

[0015] The material of this invention uses a (hydrothermal) surface-functionalized fibrous network biomass carbon material as the base adsorbent. Then, the surface-modified functional groups react with a carbon nitride precursor to form a composite adsorbent. Finally, the composite precursor is calcined using a thermochemical method to obtain the final composite adsorbent. The composite carbon-nitrogen material can effectively degrade adsorbed phenol pollutants under light irradiation, achieving efficient recycling. This invention features a simple preparation process, low production cost, and uses environmentally friendly raw materials and solvents, overcoming the shortcomings of traditional adsorbents such as high production cost, complex processes, and low reusability. Attached Figure Description

[0016] Figure 1 The scanning electron microscope image of the fibrous reticulated biochar prepared in Example 1 of this invention; Figure 2 The transmission electron microscope (TEM) image of g-C3N4 prepared in Example 1 of this invention; Figure 3 The scanning electron microscope image of the fibrous network carbon-nitrogen composite adsorbent (Cg-C3N4) prepared in Example 1 of the present invention; Figure 4 The XRD patterns of the modified cellulose network carbon and composite adsorbent in Example 1 of this invention are shown below. Figure 5 The FTIR spectra of cellulose network carbon and modified cellulose network carbon in Example 1 of this invention are shown below. Figure 6 The preparation process of the fiber network carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 1 of the present invention is as follows: Figure 7 UV absorption spectra of phenol and hydroquinone; Figure 8 This is a schematic diagram of the preparation process of the fiber-reinforced carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 1 of the present invention; Figure 9 This is a diagram showing the adsorption activity of the modified cellulose network carbon for phenol and hydroquinone in Example 1 of the present invention. Figure 10 This is an adsorption activity diagram of the fiber-reinforced carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 1 of the present invention; Figure 11 The adsorption cycle stability diagram of the fiber network carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 1 of the invention; Figure 12 The transmission electron microscope (TEM) image of g-C3N4 prepared in Example 2 of this invention; Figure 13 This is a flowchart illustrating the preparation method of the fiber-reinforced carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 2 of the present invention. Figure 14 This is a schematic diagram of the preparation process of the fiber-reinforced carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 2 of the present invention; Figure 15 Electron microscopy image of g-C3N4 prepared in Example 3 of this invention; Figure 16 The preparation process of the fiber network carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 3 of the present invention is as follows: Figure 17This is a schematic diagram of the preparation process of the fiber-reinforced carbon-nitrogen composite adsorbent (Cg-C3N4) in Example 3 of the present invention. Detailed Implementation

[0017] Example 1

[0018] The cellulose used in this example was obtained from natural poplar leaves by repeatedly heating and washing with solutions such as sodium chlorite to remove lignin and hemicellulose, and no further purification was performed after extraction.

[0019] (1) The obtained cellulose was washed three times with deionized water, and then dried and placed in a prepared copper ammonia solution. The solution was stirred for 4 to 16 hours under water bath heating at 50°C to completely dissolve the cellulose in the solution.

[0020] (2) The viscous liquid containing dissolved cellulose is injected into the sulfuric acid solution through a syringe. As the pH decreases, the cellulose copper ammonia complex will form solidified fibers again. After a period of time, the solution will wash away the blue copper salt in the artificial fiber, and finally a colorless cellulose web is obtained.

[0021] (3) The obtained cellulose web is spread out in a long strip crucible and placed in a tube furnace for carbonization. The atmosphere is a mixture of oxygen and nitrogen gas, with an oxygen ratio of 0.1% to 21%. The introduction of oxygen is to increase the oxygen-containing functional groups on the surface of the carbonized cellulose web. The carbonization temperature is 150℃ to 550℃, and the heating rate is 1℃ / min to 20℃ / min. The carbonization process is carried out with a relatively long holding time to improve the degree of carbonization of the cellulose web. The holding time is 0.5h to 15h.

[0022] (4) The obtained cellulose mesh was placed in a hydrothermal reactor for surface functionalization treatment. Appropriate amounts of acetic acid, ammonium acetate, ammonium formate, furfural, acetone and other substances were added to the hydrothermal reactor to modify the cellulose mesh, introducing functional groups such as carboxyl, amino, aldehyde and ketone groups on the carbon surface of the cellulose mesh. The ratio of the modifying reagent to cellulose carbon was 0.1~5:1, the hydrothermal treatment temperature was 50℃~200℃, and the hydrothermal treatment time was 0.5h~72h. After hydrothermal treatment, the sample was washed multiple times with deionized water and ethanol, then redispersed in deionized water, ultrasonically dispersed evenly, and then transferred to a pear-shaped flask.

[0023] (5) After the surface-modified cellulose carbon network and urea (g-C3N4 precursor) are evenly dispersed, they are added to a pear-shaped flask for reaction. The solvent is a mixture of water and ethanol in a ratio of 1:0.1~5. The heating temperature is 60~200 degrees. After reacting for 1~24 hours, the mixture is dried by rotary evaporation until the water is evaporated. The powder is then removed with a scraper for later use.

[0024] (6) The composite precursor is further polymerized into a composite carbonitride material (Cg-C3N4) by thermochemical method, and calcined in air and nitrogen atmosphere at 500~600℃ for 1~5h respectively. The calcined sample is then ground for later use.

[0025] (7) Adsorption experiments selected phenol and hydroquinone, common drug molecules in wastewater. The results showed that the composite Cg-C3N4 adsorbent could effectively adsorb phenol and hydroquinone using its network structure. After adsorption for a period of time, the adsorbed pollutants could be decomposed by irradiation with a xenon lamp for a few hours, thus achieving reuse.

[0026] Example 2

[0027] The cellulose used in this example was obtained from natural poplar leaves by repeatedly heating and washing with solutions such as sodium chlorite to remove lignin and hemicellulose, and no further purification was performed after extraction.

[0028] (1) The obtained cellulose was washed three times with deionized water, and then dried and placed in a prepared copper ammonia solution. The solution was stirred for 4 to 16 hours under water bath heating at 50°C to completely dissolve the cellulose in the solution.

[0029] (2) The viscous liquid containing dissolved cellulose is injected into the sulfuric acid solution through a syringe. As the pH decreases, the cellulose copper ammonia complex will form solidified fibers again. After a period of time, the solution will wash away the blue copper salt in the artificial fiber, and finally a colorless cellulose web is obtained.

[0030] (3) The obtained cellulose web is spread out in a long strip crucible and placed in a tube furnace for carbonization. The atmosphere is a mixture of oxygen and nitrogen gas, with an oxygen ratio of 0.1% to 21%. The introduction of oxygen is to increase the oxygen-containing functional groups on the surface of the carbonized cellulose web. The carbonization temperature is 150℃ to 550℃, and the heating rate is 1℃ / min to 20℃ / min. The carbonization process is carried out with a relatively long holding time to improve the degree of carbonization of the cellulose web. The holding time is 0.5h to 15h.

[0031] (4) The obtained cellulose mesh was placed in a hydrothermal reactor for surface functionalization treatment. Appropriate amounts of acetic acid, ammonium acetate, ammonium formate, furfural, acetone, etc. were added to the hydrothermal reactor to modify the cellulose mesh, introducing functional groups such as carboxyl, amino, aldehyde, and ketone groups on the carbon surface of the cellulose mesh. The ratio of the modifying reagent to cellulose carbon was 0.1~5:1, the hydrothermal treatment temperature was 50℃~200℃, and the hydrothermal treatment time was 0.5h~72h. After hydrothermal treatment, the sample was washed multiple times with deionized water and ethanol, then redispersed in deionized water, ultrasonically dispersed evenly, and then transferred to a pear-shaped flask.

[0032] (5) After the surface-modified cellulose carbon network and dicyandiamide (g-C3N4 precursor) are evenly dispersed, they are added to a pear-shaped flask for reaction. The solvent is a mixture of water and ethanol in a ratio of 1:0.1~5. The heating temperature is 60~200 degrees. After reacting for 1~24 hours, the mixture is dried by rotary evaporation until the water is evaporated. The powder is then removed with a scraper for later use.

[0033] (6) The composite precursor is further polymerized into a composite carbonitride material (Cg-C3N4) by thermochemical method, and calcined in air and nitrogen atmosphere at 500~600℃ for 1~5h respectively. The calcined sample is then ground for later use.

[0034] (7) Adsorption experiments selected phenol and hydroquinone, common drug molecules in wastewater. The results showed that the composite Cg-C3N4 adsorbent could effectively adsorb phenol and hydroquinone using its network structure. After adsorption for a period of time, the adsorbed pollutants could be decomposed by irradiation with a xenon lamp for a few hours, thus achieving reuse.

[0035] Example 3

[0036] The cellulose used in this example was obtained from natural poplar leaves by repeatedly heating and washing with solutions such as sodium chlorite to remove lignin and hemicellulose, and no further purification was performed after extraction.

[0037] (1) The obtained cellulose was washed three times with deionized water, and then dried and placed in a prepared copper ammonia solution. The solution was stirred for 4 to 16 hours under water bath heating at 50°C to completely dissolve the cellulose in the solution.

[0038] (2) The viscous liquid containing dissolved cellulose is injected into the sulfuric acid solution through a syringe. As the pH decreases, the cellulose copper ammonia complex will form solidified fibers again. After a period of time, the solution will wash away the blue copper salt in the artificial fiber, and finally a colorless cellulose web is obtained.

[0039] (3) The obtained cellulose web is spread out in a long strip crucible and placed in a tube furnace for carbonization. The atmosphere is a mixture of oxygen and nitrogen gas, with an oxygen ratio of 0.1% to 21%. The introduction of oxygen is to increase the oxygen-containing functional groups on the surface of the carbonized cellulose web. The carbonization temperature is 150℃ to 550℃, and the heating rate is 1℃ / min to 20℃ / min. The carbonization process is carried out with a relatively long holding time to improve the degree of carbonization of the cellulose web. The holding time is 0.5h to 15h.

[0040] (4) The obtained cellulose mesh was placed in a hydrothermal reactor for surface functionalization treatment. Appropriate amounts of acetic acid, ammonium acetate, ammonium formate, furfural, acetone, etc. were added to the hydrothermal reactor to modify the cellulose mesh, introducing functional groups such as carboxyl, amino, aldehyde, and ketone groups on the carbon surface of the cellulose mesh. The ratio of the modifying reagent to cellulose carbon was 0.1~5:1, the hydrothermal treatment temperature was 50℃~200℃, and the hydrothermal treatment time was 0.5h~72h. After hydrothermal treatment, the sample was washed multiple times with deionized water and ethanol, then redispersed in deionized water, ultrasonically dispersed evenly, and then transferred to a pear-shaped flask.

[0041] (5) After the surface-modified cellulose carbon network and melamine (g-C3N4 precursor) are evenly dispersed, they are added to a pear-shaped flask for reaction. The solvent is a mixture of water and ethanol in a ratio of 1:0.1~5. The heating temperature is 60~200 degrees. After reacting for 1~24 hours, the mixture is dried by rotary evaporation until the water is evaporated. The powder is then removed with a scraper for later use.

[0042] (6) The composite precursor is further polymerized into a composite carbonitride material (Cg-C3N4) by thermochemical method, and calcined in air and nitrogen atmosphere at 500~600℃ for 1~5h respectively. The calcined sample is then ground for later use.

[0043] (7) Adsorption experiments selected phenol and hydroquinone, common drug molecules in wastewater. The results showed that the composite Cg-C3N4 adsorbent could effectively adsorb phenol and hydroquinone using its network structure. After adsorption for a period of time, the adsorbed pollutants could be decomposed by irradiation with a xenon lamp for a few hours, thus achieving reuse.

Claims

1. A method for preparing a highly efficient and reusable fibrous mesh carbon-nitrogen composite adsorbent Cg-C3N4, characterized in that, Includes the following steps: (1) The cellulose obtained from natural poplar leaves was washed three times with deionized water, and then dried and placed in a prepared copper ammonia solution. The solution was stirred for 4 to 16 hours under water bath heating at 50°C to completely dissolve the cellulose in the solution. (2) The viscous liquid containing dissolved cellulose is injected into the sulfuric acid solution through a syringe. As the pH decreases, the cellulose copper ammonia complex will form solidified fibers again. After a period of time, the solution will wash away the blue copper salt in the artificial fiber, and finally a colorless cellulose web is obtained. (3) Spread the obtained cellulose web evenly in a long strip crucible and place it in a tube furnace for carbonization. The atmosphere is a mixture of oxygen and nitrogen, with an oxygen ratio of 0.1% to 21%. The carbonization temperature is 150℃ to 550℃, the heating rate is 1℃ / min to 20℃ / min, and the holding time is 0.5h to 15h. (4) The obtained cellulose network was placed in a hydrothermal reactor for surface functionalization treatment. Appropriate amounts of acetic acid, ammonium acetate, ammonium formate, furfural or acetone were added to the hydrothermal reactor to modify the cellulose network. The ratio of the modifying agent to cellulose carbon was 0.1~5:1, the hydrothermal treatment temperature was 50℃~200℃, and the hydrothermal treatment time was 0.5h~72h. After hydrothermal treatment, the sample was washed multiple times with deionized water and ethanol, then redispersed in deionized water, ultrasonically dispersed evenly, and then transferred to a pear-shaped flask. (5) After the surface-modified cellulose carbon network is evenly dispersed with urea, dicyandiamide or melamine, it is added to a pear-shaped flask for self-assembly. The solvent is a mixture of water and ethanol in a ratio of 1:0.1~5. The heating temperature is 60~200 degrees. After reacting for 1~24 hours, the mixture is dried by rotary evaporation until the water is evaporated. The powder is then removed with a scraper for later use. (6) The composite precursor is further polymerized into a composite carbon-nitrogen material Cg-C3N4 by thermochemical method, and calcined in air and nitrogen atmosphere at 500~600℃ for 1~5h respectively. The calcined sample is then ground for later use. (7) The adsorption experiment selected phenol and hydroquinone, common drug molecules in wastewater. After adsorption for a period of time, the adsorbed pollutants can be decomposed by irradiation with a xenon lamp for a few hours, thus achieving reuse.

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