A porous carbon-based composite ferric chloride adsorbent material, its preparation method and application

Abstract

This invention relates to the field of adsorption materials, and discloses a porous carbon-based composite ferric chloride adsorption material, its preparation method, and its application. The adsorption material is prepared by introducing aniline groups onto the surface of modified supported graphene oxide via a diazotization reaction of p-phenylenediamine, followed by in-situ polymerization of m-phenylenediamine utilizing the polymerizability of the aniline groups. The modified supported graphene oxide is prepared by using ferric chloride as a catalyst and metal source, and methyl acetal as a crosslinking agent, through a Friedel-Crafts alkylation reaction of carbazole and benzylamine monomers to obtain a nitrogen-doped porous polymer-supported iron ion material. This material is then loaded onto graphene oxide using a solvothermal method to obtain supported graphene oxide. Finally, the supported graphene oxide is carbonized in a tube furnace. The material exhibits good dispersibility, strong antioxidant capacity, a wide pH and temperature range, and excellent Cr(VI) removal efficiency, while also enabling rapid separation via magnetic properties.

Description

Technical Field

[0001] This invention belongs to the field of adsorption material technology, specifically relating to a porous carbon-based composite ferric chloride adsorption material, its preparation method, and its application. Background Technology

[0002] Heavy metal ions have become one of the major environmental pollutants due to their difficulty in biodegradation and high toxicity. Hexavalent chromium [Cr(VI)] is a major pollutant in industrial wastewater, and its discharge concentration is strictly limited. Cr(VI) has strong carcinogenic and mutagenic capabilities, and its toxicity is 500 times that of Cr(III). At the same time, Cr(VI) has strong oxidizing and migration capabilities. Large amounts of chromium-containing wastewater discharged into natural water bodies pose a serious threat to the ecological environment and human health.

[0003] The main methods for treating chromium-containing wastewater include chemical reduction-precipitation, ion exchange, membrane separation, electrolytic reduction, and adsorption. Among these, adsorption is the most commonly used. Adsorbents generally have a large specific surface area and pore volume, which can effectively treat heavy metals and organic matter. In addition, the adsorption performance of adsorbents can be further improved through functional modification. As a low-energy-consumption and high-safety treatment process, adsorption has a promising application prospect and is attracting increasing attention.

[0004] Iron, with its advantages of being inexpensive, readily available, and non-toxic, is widely used in environmental fields, such as wastewater treatment to remove chlorinated organics, organic dyes, and heavy metal ions from water. Zero-valent iron (ZVFe) nanoparticles, with their low standard electromotive force and small nanoscale size, significantly increase the number of active sites, resulting in higher reduction efficiency and faster adsorption rates in the removal of pollutants from water. However, ZVFe nanoparticles are prone to aggregation and oxidation. Graphene oxide, as a novel two-dimensional layered carbon material, is used in adsorption due to its large specific surface area and porous structure. However, the large number of negative charges on the surface of graphene oxide leads to poor adsorption of metal complex anions. Furthermore, the good dispersibility of graphene oxide in water hinders its recovery and regeneration. Summary of the Invention

[0005] To address the shortcomings mentioned in the background art, the present invention aims to provide a porous carbon-based composite ferric chloride adsorbent material, its preparation method, and its application. The prepared porous carbon-based composite ferric chloride adsorbent material exhibits good dispersibility, strong antioxidant capacity, a wide pH and temperature range, and excellent Cr(VI) removal effect. Furthermore, this porous carbon-based composite ferric chloride adsorbent material can be rapidly separated by magnetic means.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A porous carbon-based composite ferric chloride adsorbent material is prepared by introducing aniline groups onto the surface of modified supported graphene oxide via a diazotization reaction of p-phenylenediamine, followed by in-situ polymerization of m-phenylenediamine utilizing the polymerizability of the aniline groups. The modified supported graphene oxide is prepared by using ferric chloride as a catalyst and metal source, and methyl acetal as a crosslinking agent, through a Friedel-Crafts alkylation reaction between carbazole and benzylamine monomers to obtain a nitrogen-doped porous polymer-supported iron ion material. This nitrogen-doped porous polymer-supported iron ion material is then loaded onto graphene oxide using a solvothermal method to obtain supported graphene oxide, which is subsequently carbonized in a tube furnace.

[0008] Preferably, the preparation method of the modified supported graphene oxide includes the following steps:

[0009] (1) Carbazole, benzylamine, 1,2-dichloroethane, methyl acetal and anhydrous ferric chloride were placed in a reactor and pre-crosslinked at 40-50℃ for 4-5 h. Then the temperature was raised to 75-85℃ for crosslinking for 18-24 h. After the reaction was completed, the obtained solid product was added to a mixed solvent of methanol and deionized water and stirred for 0.5-1 h. Then the mixture was filtered and dried to prepare nitrogen-doped porous polymer-supported iron ion material.

[0010] (2) Graphene oxide was ultrasonically dispersed in N,N-dimethylformamide to obtain a graphene oxide suspension. The nitrogen-doped porous polymer-supported iron ion material and N,N-dimethylformamide were stirred and mixed, and then added to the graphene oxide dispersion. After stirring for 0.5 to 1 h, the mixture was transferred to a polytetrafluoroethylene reactor and reacted at 110 to 125 °C for 20 to 24 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to prepare supported graphene oxide.

[0011] (3) The supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 420-500℃ for calcination for 2-4 hours. After cooling to room temperature, it was treated with hydrogen peroxide for 4-6 hours to prepare the modified supported graphene oxide.

[0012] Preferably, the molar ratio of carbazole and benzylamine in step (1) is 1:1.

[0013] Preferably, in step (2), the mass ratio of graphene oxide to nitrogen-doped porous polymer-supported iron ion material is 10:1 to 3.

[0014] Preferably, the heating rate in step (3) is 2 to 2.5 °C / min.

[0015] A method for preparing a porous carbon-based composite ferric chloride adsorbent material includes the following steps:

[0016] A. Modified supported graphene oxide was ultrasonically dispersed in deionized water, p-phenylenediamine was added and stirred, sodium nitrite and concentrated hydrochloric acid were added under ice bath conditions, and the reaction was stirred for 10-12 hours. After the reaction was completed, the graphene oxide was prepared by filtration, washing and drying.

[0017] B. Diazotized modified supported graphene oxide was ultrasonically dispersed in hydrochloric acid solution, and a mixed solution of m-phenylenediamine and deionized water was added. The mixture was stirred and mixed under ice bath conditions, and then ammonium persulfate aqueous solution was added dropwise. The mixture was stirred and reacted for 4-6 hours. Subsequently, sodium carbonate aqueous solution was added, and the mixture was stirred and reacted for another 1.5-2 hours. After the reaction was completed, the porous carbon-based composite ferric chloride adsorbent was prepared by filtration, washing, and drying.

[0018] Preferably, in step A, the mass ratio of modified supported graphene oxide to p-phenylenediamine is 1:0.1 to 0.5.

[0019] Preferably, in step B, the mass ratio of diazotized modified supported graphene oxide to m-phenylenediamine is 1:0.1 to 0.5.

[0020] An application of a porous carbon-based composite ferric chloride adsorbent material, wherein the porous carbon-based composite ferric chloride adsorbent material is used to adsorb Cr(VI) from wastewater.

[0021] The beneficial effects of this invention are:

[0022] This invention utilizes carbazole and benzylamine as monomers, 1,2-dichloroethane as solvent, methyl acetal as crosslinking agent, and ferric chloride as catalyst and metal source. A nitrogen-doped porous polymer-supported iron ion material is obtained through a Friedel-Crafts alkylation reaction between carbazole and benzylamine monomers. Then, the nitrogen-doped porous polymer-supported iron ion material is loaded onto graphene oxide using a solvothermal method to obtain supported graphene oxide. Subsequently, the supported graphene oxide is carbonized in a tube furnace to prepare modified supported graphene oxide. Then, aniline groups are introduced onto the surface of the modified supported graphene oxide through a diazotization reaction using p-phenylenediamine. Taking advantage of the polymerizability of the aniline groups, m-phenylenediamine is introduced for in-situ polymerization, extending the aniline groups grafted onto the surface of the supported graphene oxide into a polymer of m-phenylenediamine, thereby preparing a porous carbon-based composite ferric chloride adsorbent material. Zero-valent iron is loaded into the pore structure or surface of the nitrogen-doped porous carbon-based material, avoiding the defects of easy agglomeration, easy oxidation, and poor stability of nano-zero-valent iron. This increases the specific surface area of ​​the nitrogen-doped porous polymer-loaded iron ion material, disperses the reactants, and improves the adsorption capacity for Cr(VI). Furthermore, the introduced m-phenylenediamine polymer has a large number of amine groups, which can generate a strong chelating effect on metal ions, exhibiting excellent adsorption performance. The porous carbon-based composite ferric chloride adsorbent prepared by this invention has good dispersibility, strong antioxidant capacity, a wide pH and temperature range, and good Cr(VI) removal effect. Simultaneously, this porous carbon-based composite ferric chloride adsorbent can be rapidly separated by magnetic means. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: A method for preparing modified supported graphene oxide includes the following steps:

[0025] (1) Take 1g carbazole, 0.65g benzylamine, 40mL 1,2-dichloroethane, 3.4g methyl acetal and 5.3g anhydrous ferric chloride into a reactor, place it at 45℃ for pre-crosslinking for 5h, then raise the temperature to 80℃ for crosslinking for 20h. After the reaction is completed, add the obtained solid product into a mixed solvent of 100mL methanol and 25mL deionized water and stir for 1h. Then filter and dry to prepare nitrogen-doped porous polymer-supported iron ion material;

[0026] (2) Take 2g of graphene oxide and ultrasonically disperse it in 50mL of N,N-dimethylformamide to obtain graphene oxide suspension. Add 0.2g of nitrogen-doped porous polymer-supported iron ion material and 30mL of N,N-dimethylformamide to the graphene oxide dispersion after stirring and mixing. After stirring for 1h, transfer it to a polytetrafluoroethylene reactor and react at 120℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare supported graphene oxide.

[0027] (3) The obtained supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 500℃ for 2h at a heating rate of 2.5℃ / min. After cooling to room temperature, it was treated with hydrogen peroxide for 6h to prepare modified supported graphene oxide.

[0028] Example 2: A method for preparing modified supported graphene oxide includes the following steps:

[0029] (1) Take 1g carbazole, 0.65g benzylamine, 40mL 1,2-dichloroethane, 3.4g methyl acetal and 5.3g anhydrous ferric chloride into a reactor, place it at 45℃ for pre-crosslinking for 5h, then raise the temperature to 80℃ for crosslinking for 20h. After the reaction is completed, add the obtained solid product into a mixed solvent of 100mL methanol and 25mL deionized water and stir for 1h. Then filter and dry to prepare nitrogen-doped porous polymer-supported iron ion material;

[0030] (2) Take 2g of graphene oxide and ultrasonically disperse it in 50mL of N,N-dimethylformamide to obtain graphene oxide suspension. Add 0.4g of nitrogen-doped porous polymer-supported iron ion material and 30mL of N,N-dimethylformamide to the graphene oxide dispersion after stirring and mixing. After stirring for 1h, transfer it to a polytetrafluoroethylene reactor and react at 120℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare supported graphene oxide.

[0031] (3) The obtained supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 480℃ for 3h at a heating rate of 2.2℃ / min. After cooling to room temperature, it was treated with hydrogen peroxide for 6h to prepare modified supported graphene oxide.

[0032] Example 3: A method for preparing modified supported graphene oxide includes the following steps:

[0033] (1) Take 1g carbazole, 0.65g benzylamine, 40mL 1,2-dichloroethane, 3.4g methyl acetal and 5.3g anhydrous ferric chloride into a reactor, place it at 45℃ for pre-crosslinking for 5h, then raise the temperature to 80℃ for crosslinking for 20h. After the reaction is completed, add the obtained solid product into a mixed solvent of 100mL methanol and 25mL deionized water and stir for 1h. Then filter and dry to prepare nitrogen-doped porous polymer-supported iron ion material;

[0034] (2) Take 2g of graphene oxide and ultrasonically disperse it in 50mL of N,N-dimethylformamide to obtain graphene oxide suspension. Add 0.6g of nitrogen-doped porous polymer-supported iron ion material and 30mL of N,N-dimethylformamide to the graphene oxide dispersion after stirring and mixing. After stirring for 1h, transfer it to a polytetrafluoroethylene reactor and react at 120℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare supported graphene oxide.

[0035] (3) The obtained supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 450°C for 4 hours at a heating rate of 2°C / min. After cooling to room temperature, it was treated with hydrogen peroxide for 6 hours to prepare the modified supported graphene oxide.

[0036] Example 4: A method for preparing a porous carbon-based composite ferric chloride adsorbent material includes the following steps:

[0037] A. Take 2g of the modified supported graphene oxide prepared in Example 1 and ultrasonically disperse it in 200mL of deionized water. Add 1g of p-phenylenediamine and stir to mix. Under ice bath conditions, add 0.6g of sodium nitrite and 14mL of concentrated hydrochloric acid and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare diazotized modified supported graphene oxide.

[0038] B. Take 2g of diazo-modified graphene oxide and ultrasonically disperse it in 40mL of 1mol / L hydrochloric acid solution. Add a mixed solution of 1g m-phenylenediamine and 100mL deionized water. Stir and mix under ice bath conditions. Then add 10mL of 0.1g / mL ammonium persulfate aqueous solution and stir for 5h. Then add 100mL of 0.005g / mL sodium carbonate aqueous solution and continue stirring for 2h. After the reaction is completed, filter, wash and dry to prepare porous carbon-based composite ferric chloride adsorbent material.

[0039] Example 5: A method for preparing a porous carbon-based composite ferric chloride adsorbent material includes the following steps:

[0040] A. Take 2g of the modified supported graphene oxide prepared in Example 2 and ultrasonically disperse it in 200mL of deionized water. Add 1g of p-phenylenediamine and stir to mix. Under ice bath conditions, add 0.6g of sodium nitrite and 14mL of concentrated hydrochloric acid and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare diazotized modified supported graphene oxide.

[0041] B. Take 2g of diazo-modified graphene oxide and ultrasonically disperse it in 40mL of 1mol / L hydrochloric acid solution. Add a mixed solution of 1g m-phenylenediamine and 100mL deionized water. Stir and mix under ice bath conditions. Then add 10mL of 0.1g / mL ammonium persulfate aqueous solution and stir for 5h. Then add 100mL of 0.005g / mL sodium carbonate aqueous solution and continue stirring for 2h. After the reaction is completed, filter, wash and dry to prepare porous carbon-based composite ferric chloride adsorbent material.

[0042] Example 6: A method for preparing a porous carbon-based composite ferric chloride adsorbent material includes the following steps:

[0043] A. Take 2g of the modified supported graphene oxide prepared in Example 3 and ultrasonically disperse it in 200mL of deionized water. Add 1g of p-phenylenediamine and stir to mix. Under ice bath conditions, add 0.6g of sodium nitrite and 14mL of concentrated hydrochloric acid and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare diazotized modified supported graphene oxide.

[0044] B. Take 2g of diazo-modified graphene oxide and ultrasonically disperse it in 40mL of 1mol / L hydrochloric acid solution. Add a mixed solution of 1g m-phenylenediamine and 100mL deionized water. Stir and mix under ice bath conditions. Then add 10mL of 0.1g / mL ammonium persulfate aqueous solution and stir for 5h. Then add 100mL of 0.005g / mL sodium carbonate aqueous solution and continue stirring for 2h. After the reaction is completed, filter, wash and dry to prepare porous carbon-based composite ferric chloride adsorbent material.

[0045] Comparative Example 1: A method for preparing modified supported graphene oxide includes the following steps:

[0046] (1) Dissolve 4.6 g of ferric chloride hexahydrate in a mixed solvent of 30 mL of anhydrous ethanol and 70 mL of deionized water. Filter the mixture and transfer it to a reactor. Purge the reaction with nitrogen gas. Place the reactor in an ultrasonic cleaner and add 50 mL of sodium borohydride solution with a concentration of 0.04 g / mL. After the addition is complete, continue ultrasonic treatment for 30 min. After the reaction is complete, separate the solid components, wash and freeze dry to prepare nano-zero valent iron.

[0047] (2) Take 2g of graphene oxide and ultrasonically disperse it in 50mL of N,N-dimethylformamide to obtain graphene oxide suspension. Add 0.2g of nano zero-valent iron and 30mL of N,N-dimethylformamide to the graphene oxide dispersion after stirring and mixing. After stirring for 1h, transfer it to a polytetrafluoroethylene reactor and react at 120℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare supported graphene oxide.

[0048] (3) The obtained supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 500℃ for 2h at a heating rate of 2.5℃ / min. After cooling to room temperature, it was treated with hydrogen peroxide for 6h to prepare modified supported graphene oxide.

[0049] Comparative Example 2: A method for preparing a porous carbon-based composite ferric chloride adsorbent includes the following steps:

[0050] A. Take 2g of the modified supported graphene oxide prepared in Comparative Example 1 and ultrasonically disperse it in 200mL of deionized water. Add 1g of p-phenylenediamine and stir to mix. Under ice bath conditions, add 0.6g of sodium nitrite and 14mL of concentrated hydrochloric acid and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare diazotized modified supported graphene oxide.

[0051] B. Take 2g of diazo-modified graphene oxide and ultrasonically disperse it in 40mL of 1mol / L hydrochloric acid solution. Add a mixed solution of 1g m-phenylenediamine and 100mL deionized water. Stir and mix under ice bath conditions. Then add 10mL of 0.1g / mL ammonium persulfate aqueous solution and stir for 5h. Then add 100mL of 0.005g / mL sodium carbonate aqueous solution and continue stirring for 2h. After the reaction is completed, filter, wash and dry to prepare porous carbon-based composite ferric chloride adsorbent material.

[0052] Comparative Example 3: A method for preparing a porous carbon-based composite ferric chloride adsorbent includes the following steps:

[0053] A. Take 1g carbazole, 0.65g benzylamine, 40mL 1,2-dichloroethane, 3.4g methyl acetal and 5.3g anhydrous ferric chloride into a reactor, place it at 45℃ for pre-crosslinking for 5h, then raise the temperature to 80℃ for crosslinking for 20h. After the reaction is completed, add the obtained solid product into a mixed solvent of 100mL methanol and 25mL deionized water and stir for 1h. Then filter and dry to prepare nitrogen-doped porous polymer-supported iron ion material.

[0054] B. Take 2g of graphene oxide and ultrasonically disperse it in 50mL of N,N-dimethylformamide to obtain a graphene oxide suspension. Add 0.2g of nitrogen-doped porous polymer-supported iron ion material and 30mL of N,N-dimethylformamide to the graphene oxide dispersion after stirring and mixing. After stirring for 1h, transfer it to a polytetrafluoroethylene reactor and react at 120℃ for 24h. After the reaction is completed, centrifuge, wash and dry to prepare supported graphene oxide.

[0055] C. The obtained supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 500℃ for 2h at a heating rate of 2.5℃ / min. After cooling to room temperature, it was treated with hydrogen peroxide for 6h to prepare a porous carbon-based composite ferric chloride adsorbent material.

[0056] Comparative Example 4: A method for preparing a porous carbon-based composite ferric chloride adsorbent includes the following steps:

[0057] A. Take 2g of graphene oxide and ultrasonically disperse it in 200mL of deionized water. Add 1g of p-phenylenediamine and stir to mix. Under ice bath conditions, add 0.6g of sodium nitrite and 14mL of concentrated hydrochloric acid and stir to react for 12h. After the reaction is completed, filter, wash and dry to prepare diazotized modified graphene oxide.

[0058] B. Take 2g of diazo-modified graphene oxide and ultrasonically disperse it in 40mL of 1mol / L hydrochloric acid solution. Add a mixed solution of 1g m-phenylenediamine and 100mL deionized water. Stir and mix under ice bath conditions. Then add 10mL of 0.1g / mL ammonium persulfate aqueous solution and stir for 5h. Then add 100mL of 0.005g / mL sodium carbonate aqueous solution and continue stirring for 2h. After the reaction is completed, filter, wash and dry to prepare porous carbon-based composite ferric chloride adsorbent material.

[0059] Performance testing

[0060] The porous carbon-based composite ferric chloride adsorbents prepared in Examples 4-6 and Comparative Examples 2-4 were subjected to performance testing: 2 mg of the adsorbent was added to 8 mL of Cr(VI) solution for adsorption testing. The constant temperature shaker was set at 120 r / min and 25 °C. The adsorption performance of the adsorbent was tested at different pH and temperatures. After adsorption, the solution was filtered through a 0.22 μm microporous membrane. The filtrate was measured using an atomic absorption spectrophotometer at a wavelength of 283.07 nm. The removal efficiency R(%) was calculated as follows: (C0 - C...) t R = (R / C0) × 100%, where R is the removal efficiency, %; C0 and C t The initial and instantaneous metal ion concentrations, in mg / L, are shown in Tables 1 and 2.

[0061] Table 1. Results of Cr(VI) removal rate of samples at different pH values.

[0062]

[0063] As can be seen from the data in Table 1, the adsorbent materials prepared in Examples 4-6 of this invention have a wide pH range and better adsorption and removal effect on Cr(VI) under acidic conditions. Among them, the modified supported graphene oxide component added in Comparative Example 2 utilizes graphene oxide to support nano-zero valent iron, and its measured removal rate is lower than that of Examples 4-6, indicating that the loading of nitrogen-doped porous polymer-supported iron ion materials is more conducive to the adsorption of Cr(VI). In Comparative Example 3, the modified supported graphene oxide was not diazotized and in-situ polymerized, and its measured removal rate was lower than that of Examples 4-6. This is because the large number of amine groups introduced in the modified supported graphene oxide can produce a strong chelating effect on chromium ions, showing good adsorption performance. In Comparative Example 4, the modified supported graphene oxide was replaced with an equal amount of graphene oxide, and its measured removal rate was significantly lower than that of Examples 4-6, indicating that the addition of modified supported graphene oxide greatly improves the adsorption performance of the adsorbent material.

[0064] Table 2 Results of Cr(VI) removal rate of samples at different temperatures

[0065]

[0066]

[0067] As can be seen from the data in Table 2, the adsorbent materials prepared in Examples 4-6 of this invention maintain excellent removal effect on Cr(VI) over a wider temperature range compared to Comparative Examples 2-4.

[0068] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A porous carbon-based composite ferric chloride adsorbent material, characterized in that, The modified supported graphene oxide is prepared by introducing aniline groups onto the surface of p-phenylenediamine via a diazotization reaction, followed by in-situ polymerization of m-phenylenediamine utilizing the polymerizability of the aniline groups. The modified supported graphene oxide is prepared by using ferric chloride as a catalyst and metal source, methyl acetal as a crosslinking agent, and obtaining a nitrogen-doped porous polymer-supported iron ion material through a Friedel-Crafts alkylation reaction between carbazole and benzylamine monomers. The nitrogen-doped porous polymer-supported iron ion material is then loaded onto graphene oxide using a solvothermal method to obtain supported graphene oxide. Finally, the supported graphene oxide is carbonized in a tube furnace. The preparation method of the modified supported graphene oxide includes the following steps: (1) Carbazole, benzylamine, 1,2-dichloroethane, methyl acetal and anhydrous ferric chloride were placed in a reactor and pre-crosslinked at 40~50℃ for 4~5h. Then the temperature was raised to 75~85℃ for crosslinking for 18~24h. After the reaction was completed, the obtained solid product was added to a mixed solvent of methanol and deionized water and stirred for 0.5~1h. Then the mixture was filtered and dried to prepare nitrogen-doped porous polymer-supported iron ion material. (2) Graphene oxide was ultrasonically dispersed in N,N-dimethylformamide to obtain a graphene oxide suspension. The nitrogen-doped porous polymer-supported iron ion material and N,N-dimethylformamide were stirred and mixed, and then added to the graphene oxide dispersion. After stirring for 0.5~1h, the mixture was transferred to a polytetrafluoroethylene reactor and reacted at 110~125℃ for 20~24h. After the reaction was completed, the mixture was centrifuged, washed, and dried to prepare supported graphene oxide. (3) The supported graphene oxide was placed in a tube furnace, nitrogen gas was introduced, and the temperature was raised to 420~500℃ for calcination for 2~4h. After cooling to room temperature, it was treated with hydrogen peroxide for 4~6h to prepare the modified supported graphene oxide.

2. The porous carbon-based composite ferric chloride adsorbent material according to claim 1, characterized in that, In step (1), the molar ratio of carbazole and benzylamine is 1:

1.

3. The porous carbon-based composite ferric chloride adsorbent material according to claim 1, characterized in that, In step (2), the mass ratio of graphene oxide to nitrogen-doped porous polymer-supported iron ion material is 10:1~3.

4. The porous carbon-based composite ferric chloride adsorbent material according to claim 1, characterized in that, The heating rate in step (3) is 2~2.5℃ / min.

5. A method for preparing a porous carbon-based composite ferric chloride adsorbent according to claim 1, characterized in that, Includes the following steps: A. Modified supported graphene oxide was ultrasonically dispersed in deionized water, p-phenylenediamine was added and stirred, sodium nitrite and concentrated hydrochloric acid were added under ice bath conditions, and the reaction was stirred for 10-12 hours. After the reaction was completed, the graphene oxide was filtered, washed and dried to obtain diazotized modified supported graphene oxide. B. Diazotized modified supported graphene oxide was ultrasonically dispersed in hydrochloric acid solution, and a mixed solution of m-phenylenediamine and deionized water was added. The mixture was stirred and mixed under ice bath conditions, and then ammonium persulfate aqueous solution was added dropwise. The mixture was stirred and reacted for 4-6 hours. Subsequently, sodium carbonate aqueous solution was added, and the mixture was stirred and reacted for another 1.5-2 hours. After the reaction was completed, the porous carbon-based composite ferric chloride adsorbent was prepared by filtration, washing, and drying.

6. The preparation method of the porous carbon-based composite ferric chloride adsorbent material according to claim 5, characterized in that, In step A, the mass ratio of modified supported graphene oxide to p-phenylenediamine is 1:0.1~0.

5.

7. The preparation method of the porous carbon-based composite ferric chloride adsorbent material according to claim 5, characterized in that, In step B, the mass ratio of diazotized modified supported graphene oxide to m-phenylenediamine is 1:0.1~0.

5.

8. An application of the porous carbon-based composite ferric chloride adsorbent material according to claim 1, characterized in that, The porous carbon-based composite ferric chloride adsorbent material is used to adsorb Cr(VI) from wastewater.

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