Ion composite graphene-activated carbon adsorbent as well as preparation method and application thereof

Abstract

The invention discloses an ionic composite graphene-activated carbon adsorbent and a preparation method and application thereof, and belongs to the technical field of pollutant adsorption. Graphene oxide is subjected to a base catalysis reaction to form quaternized electropositive graphene oxide; activated carbon is subjected to acid catalysis treatment to increase the phenolic hydroxyl density of the activated carbon, electronegative activated carbon is formed, and finally the two kinds of carbon material turbid liquid react to generate the composite carbon adsorption material connected by N + and O-. The prepared adsorbent has larger adsorption capacity and excellent conventional pollutant adsorption performance; when the adsorbent is used for treating papermaking wastewater, the alkaline pH environment of the papermaking wastewater can enable the adsorbent to release oxygen anions and nitrogen cations, the cellulose colloid steady state of the papermaking wastewater is broken through surface charges, meanwhile, residual pollutants in sewage are captured, the adsorption effect is further enhanced, and the defects that a traditional carbon-based adsorption material is single in electrical property and poor in adsorption effect are overcome. The high-alkalinity papermaking chemi-mechanical pulp wastewater with complex components is difficult to deal with.

Description

Technical Field

[0001] This invention belongs to the field of pollutant adsorption technology, specifically relating to an ion-composite graphene-activated carbon adsorbent, its preparation method, and its application. Background Technology

[0002] Pollutant adsorption technology is a key focus in the environmental protection field and an effective means of advanced wastewater treatment. Due to its simple operation and lack of complex facilities, adsorption plays a vital role in wastewater treatment. Adsorbents remove pollutants primarily through three mechanisms: first, hydrophobic adsorption, where the complex surface of the adsorbent provides the adsorption potential energy to adsorb some hydrophobic or weakly polar substances; second, pore filling, where the complex pore structure of the adsorbent can enclose appropriately sized pollutants, which is the main mechanism of adsorption; and finally, chemisorption, where the chemical groups on the adsorbent surface react with the pollutants, thereby fixing the pollutants to the adsorbent surface and removing them from the water.

[0003] Industrial adsorbents practically used for water pollution adsorption mainly include resins, zeolites, and activated carbon. Zeolites are three-dimensional lattices composed of silicon (aluminum) oxygen tetrahedra, with a predominantly microporous structure and the most uniform pore size distribution. Adsorption resins are a class of porous polymers capable of selectively adsorbing specific substances. Activated carbon is predominantly microporous and mesoporous, with a large specific surface area and wide applicability. Among these, activated carbon is the most widely used due to its relatively low cost and availability, high specific surface area, abundant microporous and mesoporous structures, and diverse surface functional groups. However, its adsorption effect on pulp and papermaking wastewater is very limited.

[0004] Most paper mills in my country use the chemimechanical pulping process, generating wastewater known as chemimechanical pulp wastewater. Unlike chemical pulp wastewater, chemimechanical pulp wastewater is primarily composed of lignin, cellulose, and their derivatives. Lignin is a polymer composed of three aromatic propane derivative monomers. In chemimechanical pulp wastewater, it has a complex structure and large molecular weight, making it difficult to adsorb by adsorbents. Furthermore, due to the alkaline environment of the wastewater, cellulose forms negatively charged colloids, and lignin dissolves into molecules in the water. Neither hydrophobic interactions nor pore filling can effectively treat it. Therefore, the key to treating chemimechanical pulp wastewater lies in simultaneously and effectively adsorbing both cellulose colloids and large lignin molecules.

[0005] To treat negatively charged cellulose colloids, positive charges are needed for neutralization, disrupting the stable structure of the cellulose colloid. However, treating lignin requires not only positively charged functional groups on the surface of the adsorbent but also a greater number of mesoporous and macroporous structures. Patent CN119569053A discloses activated carbon for organic wastewater treatment, which has a high specific surface area, abundant pores, a large average pore size, and well-developed mesopores, allowing it to adsorb some lignin through its porous structure. However, it struggles to treat colloidal cellulose. Patent CN115193410A discloses quaternary ammonium-modified activated carbon, which, while loading positively charged functional groups onto the activated carbon surface to disrupt the colloidal structure of cellulose, is also ineffective in treating large-molecule lignin. Therefore, the deep adsorption treatment of papermaking pulp wastewater faces a dilemma. Summary of the Invention

[0006] This invention provides an ion-composite graphene-activated carbon adsorbent, its preparation method, and its application. The novel adsorbent material prepared exhibits excellent adsorption performance in papermaking chemimechanical pulp wastewater, and can adsorb macromolecular lignin and disrupt the cellulose colloidal stability of papermaking wastewater, thereby greatly improving the COD removal capacity of chemimechanical pulp wastewater.

[0007] To achieve the above objectives, this discovery employs the following technical solution: An ion-composite graphene-activated carbon adsorbent is disclosed, in which graphene oxide is composited onto the surface of activated carbon through ionic bonds formed by the electrostatic adsorption of quaternary ammonium groups and oxygen anions. The graphene oxide forms a multilayered folded structure on the activated carbon surface, and the adsorbent has microporous and mesoporous structures. The structure of the adsorbent is as follows: .

[0008] The preparation method of the above-mentioned ion-composite graphene-activated carbon adsorbent includes the following steps: S1: Adjust the graphene oxide suspension to a strongly alkaline environment, and then add glycidyltrimethylammonium chloride to catalyze ring opening to form quaternized graphene oxide; S2: Activated carbon is catalyzed by soaking it in nitric acid and hydrogen peroxide to form negatively charged activated carbon with high phenolic hydroxyl density; S3: The quaternized graphene oxide obtained from S1 and S2 is mixed with negatively charged activated carbon and ultrasonically reacted to form an ion-composite graphene oxide-activated carbon suspension. S4: Extract the graphene oxide-activated carbon suspension obtained in S3 with tert-butanol, centrifuge, and repeat the operation three times to obtain a tert-butanol suspension of graphene-activated carbon. Freeze the suspension into a solid, and after the solid is volatilized and dried at room temperature and pressure, an ion-composite graphene-activated carbon powder adsorbent is obtained.

[0009] In the steps described above, the pH in S1 is adjusted to 11-13, preferably 12, the mass ratio of graphene oxide to glycidyltrimethylammonium chloride is 1:(40-60), preferably 1:50, and the catalytic reaction conditions are: reaction at 50-60℃ for 12h.

[0010] The mass ratio of activated carbon, nitric acid, and hydrogen peroxide in S2 is (5~10):(10~20):(10~20), preferably 5:15:20. The acid-catalyzed reaction conditions are: reaction at 50~60℃ for 6 hours.

[0011] The mass ratio of quaternized graphene oxide to negatively charged activated carbon in S3 is 1:(200~500), preferably 1:400, and the reaction conditions are an ultrasonic frequency of 40kHz and a temperature of 30℃ for 2h.

[0012] In S4, the volume ratio of graphene oxide-activated carbon suspension to tert-butanol is 1:1.

[0013] The aforementioned ion-composite graphene-activated carbon adsorbent can be used for the deep treatment of pulp and papermaking wastewater.

[0014] Beneficial effects: This invention provides an ion-composite graphene-activated carbon adsorbent, its preparation method, and its application, which have the following advantages compared with the prior art: (1) Higher adsorption capacity: In this invention, graphene oxide is converted into quaternized positively charged graphene oxide through an alkaline catalytic reaction; activated carbon is treated with acid catalysis to increase the density of phenolic hydroxyl groups and form negatively charged activated carbon; finally, the suspensions of the two carbon materials are reacted to generate N + and O - The composite carbon adsorbent material is prepared by combining graphene oxide with the surface of activated carbon. The graphene oxide forms a multi-layered folded structure on the surface of activated carbon, resulting in more mesoporous structures and increasing the surface complexity of the material. This creates more adsorption potential energy and greatly improves the adsorption capacity and adsorption ability of the adsorbent.

[0015] (2) Broader adsorption spectrum: The adsorbent prepared in this invention contains a large amount of N + and O - The ionic bonds formed will gradually break under the interference of ions in the weakly alkaline papermaking pulp wastewater, forming N... + and O - The presence of two electrical groups allows the material to simultaneously possess adsorption capabilities for both types of electrical components, greatly increasing the variety of pollutants it can adsorb. This overcomes the problem that traditional carbon-based adsorbents, with their single electrical property, are unable to cope with complex, highly alkaline pulping wastewater.

[0016] (3) Effectiveness for chemical pulp wastewater: The adsorbent prepared in this invention has more mesopores due to its multi-layered folded structure, which greatly improves the adsorption capacity of the adsorbent for macromolecular lignin and provides a higher adsorption capacity; at the same time, the N of the material + It adsorbs cellulose, disrupts the colloidal stability of wastewater, and allows the adsorbent to fully exert its adsorption capacity in papermaking pulp wastewater. Attached Figure Description

[0017] Figure 1 This is a reaction mechanism diagram of the preparation method of the present invention; Figure 2 The graphs show the COD treatment effect of the adsorbent on chemical mechanical slurry wastewater in the embodiments and comparative examples of the present invention. Figure 3 This is a graph showing the adsorption capacity of the adsorbent in the embodiments and comparative examples of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: Example 1

[0019] like Figure 1 As shown, a method for preparing an ion-composite graphene oxide-activated carbon adsorbent includes the following steps: By mass, 1 part of graphene oxide was added to 50 parts of glycidyltrimethylammonium chloride, the pH was adjusted to 12 with an appropriate amount of NaOH, and the mixture was reacted at 50-60℃ for 12 hours to obtain a quaternized graphene oxide suspension. 5 parts of activated carbon, 15 parts of nitric acid, and 20 parts of hydrogen peroxide were mixed and reacted at 50-60℃ for 6 hours to obtain a negatively charged activated carbon suspension. 1 part of quaternized graphene oxide was mixed with 400 parts of negatively charged activated carbon and reacted with ultrasound at 40kHz and 30℃ for 2 hours to obtain a graphene oxide-activated carbon suspension. 1 part of the graphene oxide-activated carbon suspension was extracted with 1 part of tert-butanol, centrifuged, and the process was repeated three times to obtain a tert-butanol suspension of graphene-activated carbon. The suspension was frozen into a solid, and the solid was volatilized and dried at room temperature and pressure to obtain an ion-composite graphene-activated carbon powder adsorbent.

[0020] Example 2

[0021] like Figure 1 As shown, a method for preparing an ion-composite graphene oxide-activated carbon adsorbent includes the following steps: By mass, 1 part of graphene oxide was added to 40 parts of glycidyltrimethylammonium chloride, the pH was adjusted to 12 with an appropriate amount of NaOH, and the mixture was reacted at 50-60℃ for 12 hours to obtain a quaternized graphene oxide suspension. 10 parts of activated carbon, 20 parts of nitric acid, and 20 parts of hydrogen peroxide were mixed and reacted at 50-60℃ for 6 hours to obtain a negatively charged activated carbon suspension. 1 part of quaternized graphene oxide was mixed with 400 parts of negatively charged activated carbon and reacted with ultrasound at 40kHz and 30℃ for 2 hours to obtain a graphene oxide-activated carbon suspension. 1 part of the graphene oxide-activated carbon suspension was extracted with 1 part of tert-butanol, centrifuged, and the process was repeated three times to obtain a tert-butanol suspension of graphene-activated carbon. The suspension was frozen into a solid, and the solid was volatilized and dried at room temperature and pressure to obtain an ion-composite graphene-activated carbon powder adsorbent.

[0022] Example 3

[0023] like Figure 1 As shown, a method for preparing an ion-composite graphene oxide-activated carbon adsorbent includes the following steps: By mass, 1 part of graphene oxide was added to 60 parts of glycidyltrimethylammonium chloride, the pH was adjusted to 12 with an appropriate amount of NaOH, and the mixture was reacted at 50-60℃ for 12 hours to obtain a quaternized graphene oxide suspension. 5 parts of activated carbon, 15 parts of nitric acid, and 20 parts of hydrogen peroxide were mixed and reacted at 50-60℃ for 6 hours to obtain a negatively charged activated carbon suspension. 1 part of quaternized graphene oxide was mixed with 500 parts of negatively charged activated carbon and reacted with ultrasound at 40kHz and 30℃ for 2 hours to obtain a graphene oxide-activated carbon suspension. 1 part of the graphene oxide-activated carbon suspension was extracted with 1 part of tert-butanol, centrifuged, and the process was repeated three times to obtain a tert-butanol suspension of graphene-activated carbon. The suspension was frozen into a solid, and the solid was volatilized and dried at room temperature and pressure to obtain an ion-composite graphene-activated carbon powder adsorbent.

[0024] Comparative Example 1 Commercially available activated carbon is from the same batch as the activated carbon used in the examples.

[0025] Comparative Example 2 A method for preparing graphene oxide-activated carbon is disclosed in Chinese patent CN113000023A. The graphene oxide and activated carbon used in the synthesis are from the same batch as the activated carbon used in the examples.

[0026] Test case The adsorbents used in Examples 1-3 and Comparative Examples 1-2 were applied to the adsorption treatment of pulp and papermaking wastewater. The initial COD of the wastewater was 266 mg / L, and the adsorbent dosage was 0.5 g / L. All experiments were conducted at room temperature for 3 hours. Iodine value and methylene blue value were tested for Examples 1-3 and Comparative Example 1 to characterize the adsorption capacity. In Table 1, Examples 1-3 are represented by E1, E2, and E3, respectively, and Comparative Examples 1-2 are represented by F1 and F2.

[0027] Table 1. COD removal rate of chemimechanical slurry wastewater from the examples and comparative adsorbents Category Performance E1 E2 E3 F1 F2 initial concentration 266 266 266 266 266 Remaining concentration 81.5 88.3 94.4 161.2 128.7 Removal rate (%) 69.4 66.8 64.5 39.4 51.6 From Table 1 and Figure 2 The comparison shows that Examples 1-3 have better deep treatment effects on papermaking pulp wastewater than the comparative example. This indicates that the adsorbent material prepared by the present invention is more suitable for papermaking pulp wastewater, can adsorb substances that are difficult to adsorb by conventional adsorbents, and makes full use of its own structural characteristics and functional group characteristics to act on lignin and cellulose in papermaking wastewater, thereby achieving better treatment effect.

[0028] Depend on Figure 3 The comparison shows that the iodine adsorption value of the adsorbent prepared by the method of the present invention is slightly higher than that of conventional activated carbon, while the methylene blue value is significantly higher. Studies have shown that the iodine adsorption value of activated carbon is positively correlated with its micropore development, and the methylene blue value is positively correlated with its mesopore development. This indicates that the novel adsorbent of the present invention has greater micropore and mesopore adsorption capacities. Therefore, the adsorbent prepared by the method of the present invention has a higher adsorption capacity.

[0029] The above are merely preferred embodiments of the present invention, which will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that for those skilled in the art, any modifications and improvements made without departing from the concept of the present invention are protected by the present invention.

Claims

1. An ion-composite graphene-activated carbon adsorbent, characterized in that, Graphene oxide is composited onto the surface of activated carbon through ionic bonds formed by the electrostatic adsorption of quaternary ammonium groups and oxygen anions, resulting in a multi-layered folded structure on the activated carbon surface.

2. The ion-composite graphene-activated carbon adsorbent according to claim 1, characterized in that, The adsorbent has a microporous and mesoporous structure.

3. The ion-composite graphene-activated carbon adsorbent according to claim 1 or 2, characterized in that, The structure of the adsorbent is as follows: 。 4. A method for preparing an ion-composite graphene-activated carbon adsorbent, characterized in that, Includes the following steps: The graphene oxide suspension was adjusted to a strongly alkaline environment, and glycidyl trimethylammonium chloride was added to catalyze ring-opening to form quaternized graphene oxide; Activated carbon is catalyzed by soaking it in nitric acid and hydrogen peroxide to form negatively charged activated carbon with high phenolic hydroxyl density; The obtained quaternized graphene oxide was mixed with negatively charged activated carbon and subjected to ultrasonic reaction to form an ion-composite graphene oxide-activated carbon suspension. The obtained graphene oxide-activated carbon suspension was extracted, centrifuged, and the operation was repeated three times before being frozen into a solid. The solid was then volatilized and dried at room temperature and pressure to obtain an ion-composite graphene-activated carbon powder adsorbent.

5. The method for preparing the ion-composite graphene-activated carbon adsorbent according to claim 4, characterized in that, The pH of the graphene oxide suspension was adjusted to a strongly alkaline environment of 11-13.

6. The method for preparing the ion-composite graphene-activated carbon adsorbent according to claim 4 or 5, characterized in that, In the catalytic ring-opening reaction to form quaternized graphene oxide, the mass ratio of graphene oxide to glycidyltrimethylammonium chloride is 1:(40~60), and the catalytic reaction conditions are: reaction at 50~60℃ for 12h.

7. The method for preparing the ion-composite graphene-activated carbon adsorbent according to claim 4, characterized in that, In the reaction to form negatively charged activated carbon with high phenolic hydroxyl density, the mass ratio of activated carbon, nitric acid, and hydrogen peroxide is (5~10):(10~20):(10~20), and the reaction conditions are: reaction at 50~60℃ for 6h.

8. The method for preparing the ion-composite graphene-activated carbon adsorbent according to claim 4, characterized in that, The mass ratio of quaternized graphene oxide to negatively charged activated carbon was 1:(200~500), and the ultrasonic reaction conditions were an ultrasonic frequency of 40kHz and a reaction time of 2h at 30℃.

9. The method for preparing the ion-composite graphene-activated carbon adsorbent according to claim 4, characterized in that, The extraction process uses tert-butanol, with a volume ratio of 1:1 between the graphene oxide-activated carbon suspension and tert-butanol.

10. The application of the ion-composite graphene-activated carbon adsorbent according to any one of claims 1-3, wherein the adsorbent is used for deep treatment of papermaking pulp wastewater, and in high alkalinity wastewater, ionic bonds are broken to release positive and negatively charged groups, so that the adsorbent has adsorption capacity of both charges simultaneously, thereby increasing the types of pollutants adsorbed.

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