An iron-nitrogen co-doped carbon composite material and its preparation method and application

Abstract

The present invention relates to the field of water treatment technology, specifically a kind of iron-nitrogen co-doped carbon composite material and its preparation method and application, the preparation method comprises the steps of: adding N, N, methylene bisacrylamide and ammonium persulfate to a uniformly dispersed mixed solution of acrylic acid and nanocellulose crystals, stirring evenly and placing in an oven for heat treatment to prepare CP hydrogel; cutting the CP hydrogel into small pieces and adding them to a melamine ethanol solution, then adding ferric acetylacetonate, stirring evenly and placing in a vacuum oven for drying treatment to prepare FeN@CP hydrogel; annealing the FeN@CP hydrogel in a nitrogen flow at 700-900 ° C to prepare the final product, iron-nitrogen co-doped carbon composite material, recorded as FeN@CP. The iron-nitrogen co-doped carbon composite material prepared by the present invention can significantly improve the adsorption capacity of bisphenol A.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and in particular to an iron-nitrogen co-doped carbon composite material and a preparation method and application thereof. Background Art

[0002] Bisphenol A (BPA) is an endocrine disruptor that poses a serious threat to human health and aquatic ecosystems due to its carcinogenicity, persistence, and bioaccumulation. Its low solubility and high stability in aquatic environments make it difficult to degrade using common water treatment technologies. Therefore, developing an efficient and rapid adsorbent to remove BPA from wastewater is an important research direction.

[0003] Most effective adsorbents for BPA removal have been carbon-based materials, such as porous carbon, activated carbon, and biochar, due to their low cost and high specific surface area. However, due to the lack of surface functional groups on pristine carbon-based materials, they generally have a low affinity for organic pollutants, and their microporous structure restricts the diffusion and accessibility of organic pollutants, limiting their adsorption capacity. To address these issues, doping carbon-based materials has significantly improved the adsorption performance of BPA. Iron / nitrogen co-doping is a strategy used to enhance the reactivity of carbon-based materials. Due to the formation of more stable complexes with pollutants and the exposure of adsorption active sites containing functional groups such as N, O, and S, Fe / N co-doped carbons tend to form a wide range of accessible binding sites, altering electron distribution and modifying pore structure. However, the structure-performance relationship of Fe / N co-doped carbons remains unclear. The stability and conformation / coordination of Fe and N within the carbon support are crucial in the design of adsorbents with enhanced adsorption capacity. Therefore, the development of advanced carbon-based materials with optimized pore structures for efficient BPA adsorption is crucial. Existing technologies require further improvement and development. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an iron-nitrogen co-doped carbon composite material and its preparation method and application, aiming to solve the technical problem that existing adsorption materials are difficult to efficiently adsorb and remove bisphenol A in wastewater.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing an iron-nitrogen co-doped carbon composite material, comprising the steps of:

[0007] N,N'-methylenebisacrylamide and ammonium persulfate were added to a uniformly dispersed mixed solution of acrylic acid and nanocellulose crystals, stirred evenly, and then placed in an oven for heating treatment to prepare a polyacrylic acid / nanocellulose crystal hydrogel, which was recorded as CP hydrogel.

[0008] The CP hydrogel was cut into small pieces and added to a melamine ethanol solution, followed by addition of ferric acetylacetonate. The mixture was stirred evenly and then placed in a vacuum oven for drying to obtain FeN@CP hydrogel.

[0009] The FeN@CP hydrogel was annealed in a nitrogen flow at 700-900° C. to obtain a final product, an iron-nitrogen co-doped carbon composite material, which was designated as FeN@CP.

[0010] The method for preparing the iron-nitrogen co-doped carbon composite material, wherein the mass ratio of nanocellulose crystals to acrylic acid in the mixed solution is 1-3:100.

[0011] The method for preparing the iron-nitrogen co-doped carbon composite material comprises the following steps: adding N,N'-methylenebisacrylamide and ammonium persulfate to a mixed solution of uniformly dispersed acrylic acid and nanocellulose crystals, stirring evenly, and then placing the mixture in an oven for heating treatment, wherein the stirring time is 10-60 minutes, the heating temperature is 80-100°C, and the heating time is 30-90 minutes.

[0012] The preparation method of the iron-nitrogen co-doped carbon composite material comprises the following steps: cutting the CP hydrogel into small pieces and adding them to a melamine ethanol solution; then adding ferric acetylacetonate; stirring evenly; and then placing the pieces in a vacuum oven for drying; wherein the stirring time is 6-24 hours, the drying temperature is 40-60° C., and the drying time is 12-48 hours.

[0013] The preparation method of the iron-nitrogen co-doped carbon composite material, wherein the FeN@CP hydrogel is annealed in a nitrogen flow at 700-900°C, the annealing time is 1-3 hours, and the heating rate is 2-10°C·min -1 .

[0014] An iron-nitrogen co-doped carbon composite material is prepared by the preparation method of the iron-nitrogen co-doped carbon composite material of the present invention.

[0015] An application of an iron-nitrogen co-doped carbon composite material, wherein the iron-nitrogen co-doped carbon composite material is used to adsorb and remove bisphenol A in water.

[0016] Beneficial effects: The iron-nitrogen co-doped carbon composite material (FeN@CP) derived from polyacrylic acid / cellulose nanocrystal hydrogel (CNC / PAA) of the present invention is synthesized by loading metals and direct carbide hydrogel matrix; this well-organized chemical network can not only be easily processed into three-dimensional porous carbon aerogel, but also provides a large number of sites for anchoring transition metals to the carbon framework during pyrolysis. The CP hydrogel not only has high mechanical strength and a rich multi-channel network structure, but also has abundant oxygen-containing functional groups (hydroxyl, carboxyl and sulfate half-ester groups), which provides a useful loading precursor for preparing highly active Fe / N coordination sites; the Fe sites anchored on the carbon-derived hydrogel can effectively inhibit active aggregation, sintering and leaching. Due to the interaction between FeN@CP and BPA, porous channels and more abundant adsorption sites, it has a favorable adsorption effect on bisphenol A. The iron-nitrogen co-doped carbon composite material prepared by the present invention can significantly improve the adsorption capacity of bisphenol A. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a flow chart of a method for preparing an iron-nitrogen co-doped carbon composite material provided by the present invention.

[0018] Figure 2 This is the X-ray diffraction pattern of the iron-nitrogen co-doped carbon composite material prepared in Examples 1-3 of the present invention.

[0019] Figure 3 This is a fitting curve diagram of the adsorption isotherm of bisphenol A removed by the iron-nitrogen co-doped carbon composite material prepared in Examples 1-3 of the present invention.

[0020] Figure 4 This is a comparison chart of the adsorption results of bisphenol A by the composite materials prepared in Example 1 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0021] The present invention provides an iron-nitrogen co-doped carbon composite material and its preparation method and application. To make the purpose, technical solution and effects of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only for the purpose of explaining the present invention and are not intended to limit the present invention.

[0022] See also Figure 1 , Figure 1 The present invention provides a flow chart of a method for preparing an iron-nitrogen co-doped carbon composite material, as shown in the figure, which includes the following steps:

[0023] S10, adding N,N'-methylenebisacrylamide and ammonium persulfate to the uniformly dispersed mixed solution of acrylic acid and nanocellulose crystals, stirring evenly, and then heating in an oven to prepare a polyacrylic acid / nanocellulose crystal hydrogel, which is recorded as CP hydrogel;

[0024] S20, cutting the CP hydrogel into small pieces and adding them to a melamine ethanol solution, then adding ferric acetylacetonate, stirring evenly, and then placing in a vacuum oven for drying to obtain FeN@CP hydrogel;

[0025] S30, annealing the FeN@CP hydrogel in a nitrogen flow at 700-900° C. to obtain a final product, an iron-nitrogen co-doped carbon composite material, which is denoted as FeN@CP.

[0026] Specifically, the iron-nitrogen co-doped carbon composite (FeN@CP) derived from polyacrylic acid / nanocellulose crystal hydrogel (CNC / PAA, CP hydrogel) is obtained by introducing iron and nitrogen elements into the hydrogel and then directly carbonizing it. The well-developed chemical network of CP hydrogel not only allows for easy processing into three-dimensional porous carbon aerogels, but also provides a large number of sites for anchoring transition metals into the carbon framework during pyrolysis. The CP hydrogel substrate not only has high mechanical strength and a rich multi-channel network structure, but also has abundant oxygen-containing functional groups (hydroxyl, carboxyl and sulfate half-ester groups), which provides a useful loading precursor for the preparation of highly active Fe / N coordination sites; the Fe sites anchored on the carbon-derived hydrogel can effectively inhibit the agglomeration, sintering and precipitation of the active ingredients. Due to the interaction between FeN@CP and BPA, the porous channels and the richer adsorption sites, it has a favorable adsorption effect on BPA.

[0027] In some embodiments, the mass ratio of nanocellulose crystals to acrylic acid in the mixed solution is 1-3:100. In this embodiment, the introduction of nanocellulose crystals primarily provides hydroxyl, sulfonic acid, and carboxyl functional groups, while also enhancing overall rigidity. Excessive introduction of nanocellulose crystals can negatively impact the gelling properties, while insufficient introduction can compromise the rigidity of the resulting iron-nitrogen co-doped carbon composite.

[0028] In some embodiments, N,N′-methylenebisacrylamide and ammonium persulfate are added to a uniformly dispersed mixed solution of acrylic acid and nanocellulose crystals, stirred until uniform, and then placed in an oven for heating. The stirring time is 10-60 minutes, the heating temperature is 80-100°C, and the heating time is 30-90 minutes. Under these conditions, the acrylic acid undergoes polymerization to form polyacrylic acid, and the nanocellulose crystals are uniformly doped in the polyacrylic acid, thereby forming a polyacrylic acid / nanocellulose crystal hydrogel.

[0029] In some embodiments, the CP hydrogel is cut into small pieces and added to a melamine ethanol solution, followed by the addition of ferric acetylacetonate, followed by stirring and drying in a vacuum oven for 6-24 hours, at a drying temperature of 40-60° C., and for 12-48 hours. In this embodiment, the melamine ethanol solution is primarily adsorbed within the CP hydrogel as a nitrogen source.

[0030] In some embodiments, the FeN@CP hydrogel is annealed in a nitrogen stream at 700-900°C for 1-3 hours at a heating rate of 2-10°C·min -1 .

[0031] In some embodiments, an iron-nitrogen co-doped carbon composite material is further provided, wherein the composite material is prepared using the method for preparing the iron-nitrogen co-doped carbon composite material of the present invention.

[0032] In some embodiments, an application of an iron-nitrogen co-doped carbon composite material is also provided, wherein the iron-nitrogen co-doped carbon composite material of the present invention is used to adsorb and remove bisphenol A in water.

[0033] The present invention will be further explained below by means of specific embodiments:

[0034] Example 1

[0035] This embodiment provides a method for preparing an iron-nitrogen co-doped carbon composite material, comprising the following steps:

[0036] S1: 12 mL of 15 g / L MBA and 6 mL of 50 g / L APS were added to a uniformly dispersed 60 mL mixed solution of AA (acrylic acid) and CNC (nanocellulose crystals) (wherein the CNC content was 3 wt.% of AA) and stirred for 30 min. The mixture was then oven-dried at 90 °C for 60 min to form a CP (CNC / PAA) hydrogel.

[0037] S2: The CP hydrogel was cut into 0.5 g pieces and placed in 80 ml of melamine (0.15 M) ethanol solution. 0.05 M ferric acetylacetonate was then added to the solution and stirred for 6 h. The solution was then washed three times with ethanol and deionized water, respectively, and dried in a vacuum oven at 50 °C for 8 h to form the intermediate product, FeN@CP hydrogel.

[0038] S3: The prepared intermediate product FeN@CP hydrogel was heated at 800℃ and 5℃·min -1 The final product FeN@CP was obtained by annealing in nitrogen flow for 2 h. 800 .

[0039] Example 2

[0040] The 800°C in Example 1 was replaced by 700°C, and the other parameters were the same as in Example 1. The iron-nitrogen co-doped carbon composite material (FeN@CP 700 ).

[0041] Example 3

[0042] The 800°C in Example 1 was replaced by 900°C, and the other parameters were the same as in Example 1. The iron-nitrogen co-doped carbon composite material (FeN@CP 900 ).

[0043] Example 4

[0044] This embodiment provides a method for preparing an iron-nitrogen co-doped carbon composite material, comprising the following steps:

[0045] S1: 12 mL of 15 g / L MBA and 6 mL of 50 g / L APS were added to a uniformly dispersed 60 mL mixed solution of AA (acrylic acid) and CNC (nanocellulose crystals) (wherein the CNC content was 1 wt.% of AA) and stirred for 10 min. The mixture was then oven-dried at 90 °C for 30 min to form a CP (CNC / PAA) hydrogel.

[0046] S2: The CP hydrogel was cut into 0.5 g pieces and placed in 80 ml of melamine (0.15 M) ethanol solution. 0.05 M ferric acetylacetonate was then added to the solution and stirred for 4 h. The solution was then washed three times with ethanol and deionized water, respectively, and dried in a vacuum oven at 50 °C for 6 h to form the intermediate product, FeN@CP hydrogel.

[0047] S3: The prepared intermediate product FeN@CP hydrogel was heated at 800℃ and 2℃·min -1 The final product FeN@CP was obtained by annealing in nitrogen flow for 2 h. 800 .

[0048] Example 5

[0049] This embodiment provides a method for preparing an iron-nitrogen co-doped carbon composite material, comprising the following steps:

[0050] S1: 12 mL of 15 g / L MBA and 6 mL of 50 g / L APS were added to a uniformly dispersed 60 mL mixed solution of AA (acrylic acid) and CNC (nanocellulose crystals) (wherein the CNC content was 3 wt.% of AA) and stirred for 60 min. The mixture was then oven-dried at 90 °C for 90 min to form a CP (CNC / PAA) hydrogel.

[0051] S2: The CP hydrogel was cut into 0.5 g pieces and placed in 80 ml of melamine (0.15 M) ethanol solution. 0.05 M ferric acetylacetonate was then added to the solution and stirred for 24 h. The solution was then washed three times with ethanol and deionized water, respectively, and dried in a vacuum oven at 50 °C for 48 h to form the intermediate product, FeN@CP hydrogel.

[0052] S3: The prepared intermediate product FeN@CP hydrogel was heated at 800℃ and 10℃·min -1 The final product FeN@CP was obtained by annealing in nitrogen flow for 2 h. 800 .

[0053] Comparative Example 1

[0054] Without adding ferric acetylacetonate and melamine in Example 1, other parameters were the same as in Example 1 to prepare a nitrogen-doped carbon composite material (CP).

[0055] Comparative Example 2

[0056] Without adding ferric acetylacetonate in Example 1, the other parameters were the same as in Example 1, and the nitrogen-doped carbon composite material (N@CP 800 ).

[0057] Comparative Example 3

[0058] Without adding melamine in Example 1, the other parameters were the same as in Example 1, and the prepared nitrogen-doped carbon composite material (Fe@CP 800 ).

[0059] Test Example 1

[0060] like Figure 2 As shown, Figure 2 The X-ray diffraction patterns of the iron-nitrogen co-doped carbon composite materials prepared in Examples 1-3 are shown. Figure 2 It can be seen that there are strong and sharp diffraction peaks of graphitic carbon (PDF: 50-0927) at 21.00° and 26.52°, indicating that the induction of Fe-N species helps to improve the degree of graphitization of pure CP carbon. The introduced iron exists mainly in the form of nitrides, supplemented by the formation of carbides and oxides. The peaks at 43.69°, 44.50°, 60.12° and 68.20° correspond to Fe3N (PDF: 49-1663), while the peak at 50.08° corresponds to FeC (PDF: 03-0400), and the peaks at 35.89° and 39.49° correspond to FeOOH (PDF: 18-0639). It is worth noting that the peaks at 41.17° and 47.91° that belong only to FeN@CP are observed. 800The obvious diffraction peaks correspond to Fe4N (PDF: 06-0627), indicating that both Fe3N and Fe4N are FeN@CP 800 The results indicate that the presence of Fe4N can not only compensate for the defects of metallic Fe by inhibiting the aggregation and over-oxidation of metallic Fe, but also provide active sites with efficient adsorption performance.

[0061] Test Example 2

[0062] 5 mg of the iron-nitrogen co-doped carbon composite material prepared in Example 1-3 was added to 20 mL of 50 mg / L bisphenol A solution and the mixture was stirred at 25°C at a speed of 200 r / min and different initial concentrations (10, 30, 50, 100, 200, 300 and 400 mg·L -1 After the reaction is complete, 3 ml of the solution is pipetted and the adsorbed bisphenol A concentration is measured using a UV spectrophotometer at a wavelength of 276 nm until adsorption equilibrium is reached.

[0063] The adsorption isotherm fitting curve of the iron-nitrogen co-doped carbon composite material prepared in Example 1-3 for removing bisphenol A is as follows: Figure 3 As shown, it can be seen that FeN@CP 800 The adsorption capacity is 253.6 mg / g, FeN@CP 700 The adsorption capacity is 131.5 mg / g, FeN@CP 900 The adsorption capacity is 182.2 mg / g. It can be seen that calcination at 800℃ can significantly increase the adsorption capacity of the composite material for bisphenol A.

[0064] According to the same test method, it was found that the FeN@CP prepared in Example 4 and Example 5 800 The adsorption capacity of the composite materials for bisphenol A is 250.5 mg / g and 259.2 mg / g respectively, which also has a large adsorption capacity and can be used for the adsorption and removal of bisphenol A.

[0065] Test Example 3

[0066] 5 mg of the composite materials prepared in Example 1 and Comparative Examples 1-3 were added to 20 mL of 50 mg / L bisphenol A solution and the mixture was stirred at 25°C at a speed of 200 r / min and different initial concentrations (10, 30, 50, 100, 200, 300 and 400 mg·L -1 ) and shake thoroughly. After the reaction is complete, use a dropper to draw 3 ml of the solution and use an ultraviolet spectrophotometer to measure the concentration of bisphenol A after adsorption at a wavelength of 276 nm. The results are as follows Figure 4 As shown. Figure 4 It can be seen that the bisphenol A adsorption capacity of the composite material CP is 52.62 mg / g, and the composite material N@CP800 The adsorption capacity of bisphenol A is 96.18 mg / g, and the composite material Fe@CP 800 The adsorption capacity of bisphenol A is 138.93 mg / g, while the composite material FeN@CP in Example 1 800 The adsorption capacity is 253.6 mg / g. By comparison, it can be found that the co-doping of iron and nitrogen can significantly improve the adsorption capacity of the composite material for bisphenol A.

[0067] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An application of an iron-nitrogen co-doped carbon composite material, characterized in that: The iron-nitrogen co-doped carbon composite material is used to adsorb and remove bisphenol A in water; The iron-nitrogen co-doped carbon composite material is prepared by the following method: N,N'-methylenebisacrylamide and ammonium persulfate were added to a uniformly dispersed mixed solution of acrylic acid and nanocellulose crystals, stirred evenly, and then placed in an oven for heating treatment to prepare a polyacrylic acid / nanocellulose crystal hydrogel, which was recorded as CP hydrogel. The CP hydrogel was cut into small pieces and added to a melamine ethanol solution, followed by addition of ferric acetylacetonate. The mixture was stirred evenly and then placed in a vacuum oven for drying to obtain FeN@CP hydrogel. The FeN@CP hydrogel was annealed in a nitrogen flow at 700-900° C. to obtain a final product, an iron-nitrogen co-doped carbon composite material, which was designated as FeN@CP.

2. The use according to claim 1, characterized in that In the mixed solution, the mass ratio of nanocellulose crystals to acrylic acid is 1-3:

100.

3. The use according to claim 1, characterized in that N,N'-methylenebisacrylamide and ammonium persulfate are added to a mixed solution of uniformly dispersed acrylic acid and nanocellulose crystals, stirred evenly, and then placed in an oven for heating treatment. The stirring time is 10-60 minutes, the heating temperature is 80-100°C, and the heating time is 30-90 minutes.

4. The use according to claim 1, characterized in that The CP hydrogel is cut into small pieces and added to a melamine ethanol solution, and then ferric acetylacetonate is added. After stirring evenly, the mixture is placed in a vacuum oven for drying. The stirring time is 6-24 hours, the drying temperature is 40-60° C., and the drying time is 12-48 hours.

5. The use according to claim 1, characterized in that In the step of annealing the FeN@CP hydrogel in a nitrogen flow at 700-900°C, the annealing time is 1-3 hours and the heating rate is 2-10°C·min -1 .

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