Functionalized graphene composite material, and preparation method and application thereof

Abstract

The application discloses a kind of functionalized graphene composite material and its preparation method and application, belong to water treatment technology and material science technical field.The composite material includes graphene oxide, and the chitosan that is chemically crosslinked with the graphene oxide, and the cerium dioxide that is loaded on the surface of graphene oxide-chitosan crosslinking compound.In the composite material of the application, the high toxicity trivalent arsenic can be oxidized to low toxicity pentavalent arsenic in situ by cerium dioxide, chitosan enhances structural stability and provides adsorption site, and graphene oxide provides high specific surface area substrate, and the three achieve the integration of "oxidation-adsorption-fixing".The material can be used statically, and can also be packed in adsorption column for dynamic continuous flow treatment, with excellent penetration performance and regeneration performance, and the total arsenic removal rate can reach more than 99%, and has wide application prospect in the field of arsenic-containing wastewater deep purification.

Description

Technical Field

[0001] This invention relates to the fields of water treatment technology and materials science and technology, and in particular to a functionalized graphene composite material, its preparation method and application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Arsenic pollution in water bodies is a major global concern for water safety. Factors such as industrial wastewater discharge and geological leaching lead to excessive arsenic levels in groundwater, industrial wastewater, and drinking water. Arsenic's high toxicity and carcinogenicity pose a serious threat to the ecological environment and human health. Current water quality standards set extremely low limits for arsenic content in water bodies and impose stringent requirements on advanced purification technologies for arsenic-containing water. Currently, adsorption is the mainstream technology for arsenic removal from water bodies, offering advantages such as ease of operation, low maintenance costs, and strong adaptability, making it suitable for large-scale treatment scenarios for various water bodies.

[0004] Among existing arsenic removal adsorption materials, graphene oxide stands out as a superior adsorption substrate due to its high specific surface area and abundant oxygen-containing functional groups. However, single graphene oxide suffers from poor dispersibility and weak structural stability, and can only remove arsenic pollutants through simple physical and electrostatic adsorption. Its purification effect on trivalent arsenic, which is difficult to remove from water, is extremely poor. Conventional graphene oxide-modified materials can only optimize the substrate dispersion performance but cannot achieve arsenic speciation transformation, making it difficult to solve the core problem of capturing electrically neutral trivalent arsenic in neutral water. Furthermore, powdered adsorption materials have poor hydraulic performance, are prone to clogging and leakage, and cannot be adapted to continuous dynamic water treatment processes. Overall, their arsenic removal efficiency and engineering practicality have significant shortcomings, making it difficult to meet the practical application requirements for deep arsenic purification in water. Summary of the Invention

[0005] In view of this, the present invention provides a functionalized graphene composite material, its preparation method and application.

[0006] In a first aspect, the present invention provides a functionalized graphene composite material comprising graphene oxide, chitosan chemically cross-linked with the graphene oxide, and cerium dioxide loaded on the surface of the graphene oxide-chitosan cross-linked composite.

[0007] Secondly, the present invention provides a method for preparing the above-mentioned functionalized graphene composite material, comprising the following steps: Graphene oxide was dispersed in water, and a condensing agent and an acetic acid solution containing chitosan were added to carry out a cross-linking reaction. After centrifugation, washing, and drying, a graphene oxide-chitosan complex was obtained. The graphene oxide-chitosan complex was dispersed in water, a cerium source precursor solution was added, the pH was adjusted to alkaline, and after reaction, it was aged, washed and dried to obtain the final product.

[0008] Preferably, in the crosslinking reaction, the mass ratio of graphene oxide to chitosan is 1:1.5~2.5, more preferably 1:2; The concentration of the acetic acid solution is 0.5-2%, preferably 1%, and the concentration of chitosan in the acetic acid solution is 0.5-2 mg / mL, preferably 2 mg / mL.

[0009] Preferably, the condensing agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

[0010] Preferably, the mass ratio of graphene oxide, chitosan, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 1:(1.5~2.5):(1.5~2.5):(1~1.5).

[0011] Preferably, the crosslinking reaction is carried out at room temperature with stirring for 22-26 h in the dark.

[0012] Preferably, the mass ratio of the graphene oxide-chitosan composite to the cerium source precursor is 1:3~5; The cerium source precursor is cerium nitrate hexahydrate, and the concentration of the cerium source precursor solution is 15~25 mg / mL.

[0013] Preferably, the pH is adjusted to 9-10, and the reaction is carried out at room temperature with stirring for 1.5-3 hours after pH adjustment. The aging process is a low-temperature static aging process, with a temperature of 3-5℃, preferably 4℃, and a time of 23-25 ​​hours.

[0014] Preferably, the drying temperature is 50~80℃ and the time is 12~24h.

[0015] Thirdly, the present invention provides the application of the above-mentioned functionalized graphene composite material or the composite material prepared by the above method in the removal of arsenic from groundwater, industrial wastewater or drinking water.

[0016] Compared with the prior art, the present invention has achieved the following beneficial effects: This invention relates to a composite material comprising graphene oxide, chitosan chemically cross-linked with graphene oxide, and cerium dioxide loaded on the surface of the graphene oxide-chitosan cross-linked composite. Through the synergistic effect of these three components, it overcomes multiple technical bottlenecks in existing graphene oxide arsenic removal materials, including weak arsenic removal capacity, poor hydraulic performance, and inability to adapt to dynamic continuous water treatment. Firstly, the cross-linking of chitosan and graphene oxide creates a stable three-dimensional structure, significantly improving the mechanical strength and packing performance of the composite material. This avoids the defects of pure powder materials, such as easy loss, clogging, and poor hydraulic stability, allowing the material to be stably packed in adsorption columns and adaptable to continuous flow dynamic water treatment processes, effectively improving the material's engineering applicability. Secondly, graphene oxide utilizes its ultra-large specific surface area to construct an adsorption framework, providing ample adsorption sites; chitosan further optimizes the material's dispersibility and introduces amino and hydroxyl active groups, enhancing the arsenic adsorption capacity. Finally, the loaded cerium dioxide possesses unique Ce³... + / Ce 4+ The redox properties enable the in-situ oxidation of electrically neutral trivalent arsenic, which is difficult to remove with traditional materials, into easily adsorbed pentavalent arsenic in a mild aquatic environment. This solves the problem of the extremely poor removal effect of trivalent arsenic by graphene oxide alone, achieving highly efficient and deep removal of total arsenic (As(III) and As(V)) from water, with a removal rate of over 99%. This invention, through the synergistic effect of these three components, combines excellent hydraulic performance, high adsorption capacity, and the ability to remove arsenic in all forms, breaking through the technical bottleneck that traditional adsorption materials are only suitable for static intermittent treatment. It is perfectly adapted to large-scale, continuous deep treatment scenarios for arsenic-containing wastewater. Attached Figure Description

[0017] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0018] Figure 1 The images are scanning electron microscope images of GO, GO@CS, and GO@CS@CeO2 prepared in Example 1, where (a) is GO, (b) is GO@CS, and (c) is GO@CS@CeO2. Figure 2 The images show the FT-IR spectra of GO, GO@CS, and GO@CS@CeO2 prepared in Example 1, where (a) is GO, (b) is GO@CS, and (c) is GO@CS@CeO2. Figure 3The XRD patterns of GO, GO@CS, and GO@CS@CeO2 prepared in Example 1 are shown, where (a) is GO, (b) is GO@CS, and (c) is GO@CS@CeO2. Figure 4 The graph shows the arsenic removal efficiency of GO in Comparative Example 1, GO@CS in Comparative Example 2, GO@CeO2 in Comparative Example 3, and GO@CS@CeO2 in Example 1. Figure 5 The graph shows the effect of different pH values ​​on the adsorption of arsenic by GO@CS@CeO2-4 prepared in Example 1, where (a) represents As(III) and (b) represents As(V). Figure 6 The graph shows the removal efficiency of arsenic adsorbed by GO@CS@CeO2-4 prepared in Example 1 for different competing ions, where (a) represents As(III) and (b) represents As(V). Figure 7 This is a cyclic regeneration diagram of GO@CS@CeO2 prepared in Example 1; Figure 8 The image shows the leaching curve of the GO@CS@CeO2 column prepared in Example 1. Detailed Implementation

[0019] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. All reagents and materials used in this application are readily available through conventional means, and unless otherwise specified, they are used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this application. The preferred embodiments and materials described herein are for illustrative purposes only.

[0021] The present invention provides a functionalized graphene composite material comprising graphene oxide, chitosan chemically cross-linked with the graphene oxide, and cerium dioxide loaded on the surface of the graphene oxide-chitosan cross-linked composite.

[0022] In the composite material of this invention, cerium dioxide nanoparticles loaded on the surface of the graphene oxide-chitosan crosslinked composite utilize their own Ce³⁺... + / Ce 4+The redox properties enable it to directly oxidize electrically neutral As(III) molecules under mild aquatic conditions, converting them in situ into negatively charged As(V). This process requires no additional oxidant or pre-oxidation unit. Subsequently, the in-situ generated As(V) can be efficiently captured by the oxygen-containing functional groups of graphene oxide and the amino groups of chitosan through electrostatic and coordination interactions. Graphene oxide, as a substrate, not only provides a high specific surface area to disperse cerium dioxide nanoparticles and prevent their aggregation, but also offers unobstructed channels for arsenic adsorption and transport due to its two-dimensional sheet structure. Chitosan, through chemical cross-linking with graphene oxide, connects the originally loose graphene oxide sheets into a stable whole. The synergistic effect of these three components enables the composite material to achieve an integrated "oxidation-adsorption-fixation" function, with a total arsenic removal rate of over 99%. It can simultaneously and efficiently remove different forms of arsenic from water without additional pretreatment processes, balancing material structural stability with deep arsenic purification capabilities, making it suitable for various arsenic-containing water purification scenarios.

[0023] Furthermore, the composite material of this invention uses graphene oxide as a framework, with chitosan bonded to graphene oxide through chemical cross-linking (i.e., amidation cross-linking) to form a GO-CS cross-linked composite. The numerous amino and hydroxyl groups on the chitosan molecular chain not only provide additional adsorption sites, but more importantly, the amidation chemical bonding between chitosan and graphene oxide significantly enhances the bonding force between graphene oxide sheets, transforming the originally easily dispersed and low-mechanical-strength graphene oxide powder into a composite particulate material with a three-dimensional network structure. This structure maintains its morphological integrity and pore stability even under water flow erosion. Therefore, this material can be directly packed into adsorption columns, exhibiting excellent water permeability and pressure resistance in continuous flow dynamic processing, avoiding the sudden pressure drop and clogging issues caused by nanoparticle filling, while ensuring sufficient mass transfer efficiency. This characteristic enables the material of this invention to truly move from laboratory-scale static adsorption to engineering-scale dynamic column adsorption applications.

[0024] In the composite material of this invention, CeO2 nanoparticles are uniformly dispersed, exhibiting excellent breakthrough curve characteristics in dynamic column adsorption processes, with a bed volume of up to 42.16 BV. The composite material can be effectively desorbed and regenerated using alkaline solutions; after 10 adsorption-desorption cycles, the adsorption capacity retention rate remains above 80%.

[0025] The composite material of this invention can be used in powder form for batch processing or packed into an adsorption column for continuous flow dynamic processing, and has good prospects for engineering applications.

[0026] This invention provides a method for preparing the above-mentioned functionalized graphene composite material, comprising the following steps: Graphene oxide was dispersed in water, and a condensing agent and an acetic acid solution containing chitosan were added to carry out a cross-linking reaction. After centrifugation, washing, and drying, a graphene oxide-chitosan complex was obtained. The graphene oxide-chitosan complex was dispersed in water, a cerium source precursor solution was added, the pH was adjusted to alkaline, and after reaction, it was aged, washed and dried to obtain the final product.

[0027] In this invention, the graphene oxide is graphene oxide prepared by the modified Hummers method. The modified Hummers method is a well-known method for preparing graphene oxide in the art. This invention does not impose any special restrictions on the specific steps and process conditions of this method. Any modified Hummers method that can obtain graphene oxide can be used in this invention.

[0028] In this invention, the mass ratio of graphene oxide to chitosan in the crosslinking reaction is 1:1.5~2.5, preferably 1:2, to ensure that the carboxyl groups on the graphene oxide react fully. When the mass ratio of GO to CS is within this range, it can ensure that CS fully encapsulates and crosslinks GO to form a stable composite structure, avoid excessive CS leading to a decrease in specific surface area and pore blockage, and provide a sufficient number of amino adsorption sites.

[0029] In this invention, the concentration of the acetic acid solution is 0.5-2%, preferably 1%, and the concentration of chitosan in the acetic acid solution is 0.5-2 mg / mL, preferably 2 mg / mL. A specific concentration of acetic acid solution ensures complete dissolution of CS and a suitable viscosity, facilitating uniform mixing and reaction with GO.

[0030] In this invention, the condensing agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Using this composite condensing agent can efficiently activate the active functional groups of graphene oxide and chitosan, promoting the formation of stable amide chemical bonds between them. This replaces the traditional physical adsorption binding method, effectively preventing chitosan detachment during water treatment and improving the overall structural strength and recyclability of the composite material.

[0031] In this invention, the mass ratio of graphene oxide, chitosan, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 1:(1.5~2.5):(1.5~2.5):(1~1.5).

[0032] In this invention, the crosslinking reaction is carried out at room temperature in the dark with stirring for 22-26 hours. The room temperature and dark environment can avoid side reactions caused by light and temperature fluctuations, and protect the activity of the raw materials; the sufficient reaction time of 22-26 hours can ensure that graphene oxide and chitosan are fully crosslinked, maximize the formation of a stable complex, and improve the adsorption activity and structural stability of the material.

[0033] In this invention, the mass ratio of the graphene oxide-chitosan composite to the cerium source precursor is 1:3~5, preferably 1:4; The cerium source precursor is cerium nitrate hexahydrate, and the concentration of the cerium source precursor solution is 15-25 mg / mL. This mass ratio range is crucial for controlling the CeO2 loading. Within this range, sufficient CeO2 loading is ensured for efficient catalytic oxidation of As(III), while preventing excessive CeO2 from agglomerating and clogging the pores of GO@CS. A specific concentration of cerium source solution facilitates the generation of fine-sized, uniformly distributed CeO2 nanoparticles on the GO@CS surface via in-situ precipitation. Under these conditions, CeO2 particles are uniformly and densely loaded on the GO@CS sheet surface.

[0034] In this invention, the pH is adjusted to 9-10, and the reaction is carried out at room temperature with stirring for 1.5-3 hours after pH adjustment. The aging process is a low-temperature static aging process, with a temperature of 3-5°C, preferably 4°C, and a time of 23-25 ​​hours. Alkaline pH is a necessary condition for the in-situ precipitation of cerium source to generate highly active cerium dioxide, and the reaction time ensures complete oxide formation. Low-temperature aging can promote the regularization and stable adhesion of cerium dioxide grains to the substrate surface, further improving the structural density and catalytic oxidation performance of the composite material.

[0035] Alkaline pH 9-10 is Ce³ + The optimal conditions for hydrolysis to generate CeO2 nanoparticles are as follows: within this pH range, the nucleation rate is moderate, which is conducive to the formation of particles with good crystal structure and uniform size. A reaction time of 1.5–3 hours ensures complete precipitation. Subsequent low-temperature static aging facilitates the transformation of the amorphous precipitate into a more stable crystalline state and allows the CeO2 nanoparticles to bond more firmly to the substrate.

[0036] In this invention, the drying temperature is 50~80°C, and the time is 12~24 hours. These mild drying conditions aim to remove internal moisture from the material while maximizing the preservation of its porous structure and the activity of its functional groups.

[0037] This invention provides the application of the above-described functionalized graphene composite material or the composite material prepared by the above method in the removal of arsenic from groundwater, industrial wastewater or drinking water.

[0038] Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be construed as limiting the scope of the invention. Specific conditions not specified in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Components whose manufacturers are not specified are all commercially available conventional products.

[0039] The graphene oxide used in the following examples and comparative examples of this invention was prepared by the modified Hummers method. The modified Hummers method can be found in the reference Marcano DC, Kosynkin DV, Berlin JM, et al. Improved synthesis of graphene oxide. [J]. Acs Nano, 2010, 4(8):4806. Example 1: GO@CS@CeO2 composite material This embodiment provides a method for preparing a functionalized graphene composite material (denoted as GO@CS@CeO2), including the following steps: (1) Preparation of GO@CS complex: 200 mg of chitosan (CS) was weighed and dissolved in 100 mL of 1% acetic acid solution. The solution was heated to 55 °C and stirred until completely dissolved. 100 mg of graphene oxide (GO) was weighed and dispersed in 100 mL of deionized water. The dispersion was ultrasonically dispersed for 5 h to obtain a GO dispersion. 192 mg of EDC and 105 mg of NHS were added as condensing agents. The CS solution was slowly added dropwise to the GO dispersion, and the reaction was carried out at room temperature in the dark with stirring for 24 h. After the reaction was completed, the mixture was centrifuged, washed three times with deionized water, and dried under vacuum at 60 °C for 12 h to obtain the GO@CS complex.

[0040] (2) Preparation of GO@CS@CeO2 composite material: Weigh 50 mg of the above GO@CS composite and disperse it in 50 mL of deionized water, then sonicate until homogeneous. Weigh 200 mg of cerium nitrate hexahydrate [Ce(NO3)3·6H2O], dissolve it in 10 mL of deionized water, and slowly add it dropwise to the above dispersion, stirring for 30 min. Adjust the pH to 9 with 0.1 M sodium hydroxide solution and stir at room temperature for 2 h. After the reaction is complete, allow it to stand at 4℃ for 24 h, centrifuge, wash three times alternately with deionized water and anhydrous ethanol, and vacuum dry at 60℃ for 24 h to obtain the GO@CS@CeO2 composite material.

[0041] Example 2: GO@CS@CeO2 composite material The difference between this embodiment and Example 1 is that in step (2), 50 mg of GO@CS complex is weighed and 150 mg of cerium nitrate hexahydrate is added, that is, the mass ratio of cerium source precursor to GO@CS substrate is 3:1. Other steps and parameters are the same as in Example 1.

[0042] Example 3: GO@CS@CeO2 composite material The difference between this embodiment and Example 1 is that in step (2), 50 mg of GO@CS complex is weighed and 250 mg of cerium nitrate hexahydrate is added, that is, the mass ratio of cerium source precursor to GO@CS substrate is 5:1. Other steps and parameters are the same as in Example 1.

[0043] Comparative Example 1: Pure Graphene Oxide (GO) This comparative example uses graphene oxide prepared by the modified Hummers method.

[0044] Comparative Example 2: GO@CS binary composite material This comparative example provides a method for preparing a GO@CS binary composite material: following step (1) of Example 1, the GO@CS composite material is prepared with a GO:CS mass ratio of 1:2, without performing the CeO2 loading in step (2). That is, only the graphene oxide-chitosan binary composite material GO@CS is obtained.

[0045] Comparative Example 3: GO@CeO2 binary composite material This comparative example provides a method for preparing a GO@CeO2 binary composite material: omitting the chitosan crosslinking step in Example 1, GO is directly compounded with a cerium source precursor via in-situ precipitation. The specific steps are as follows: 50 mg of GO is weighed and dispersed in 50 mL of deionized water, 200 mg of cerium nitrate hexahydrate is added, the pH is adjusted to 9, the mixture is stirred at room temperature for 2 h, aged, washed, and dried to obtain the GO@CeO2 composite material.

[0046] The GO, GO@CS, and GO@CS@CeO2 prepared in Example 1 were characterized by SEM, and the results are as follows: Figure 1 As shown. Figure 1 (a): GO exhibits a typical lamellar structure with obvious wrinkling at the edges. Figure 1 (b): The lamellar wrinkling of the GO@CS complex is further intensified, indicating that chitosan has been successfully cross-linked on the GO surface. Figure 1 (c): On GO@CS@CeO2, CeO2 nanoparticles are uniformly and densely loaded on the surface of the sheet, with a particle size of about 10-20 nm.

[0047] FT-IR characterization was performed on GO, GO@CS, and GO@CS@CeO2 prepared in Example 1, and the results are as follows: Figure 2 As shown. GO spectrum: 1720 cm⁻¹ - ¹(C=O stretching vibration), 1620 cm - ¹(C=C skeletal vibration), 1050 cm - ¹(COC stretching vibration). GO@CS spectrum: 1646 cm⁻¹ - ¹ and 1540 cm- The characteristic absorption peaks at ¹, belonging to the amide I band (C=O stretching vibration) and amide II band (NH bending vibration), respectively, confirm that GO and CS have formed amide bonds through chemical cross-linking. GO@CS@CeO2 spectrum: 460 cm⁻¹ - A distinct Ce-O bond vibration absorption peak appeared at position ¹, indicating that CeO2 was successfully loaded.

[0048] The GO, GO@CS, and GO@CS@CeO2 prepared in Example 1 were characterized by XRD, and the results are as follows: Figure 3 As shown, the characteristic diffraction peak at 9.5° belongs to GO; the broadened diffraction peak near 21° belongs to CS; and the characteristic peaks at 28.5°, 47°, and 56.3° belong to the CeO2 crystalline phase. The co-occurrence of these characteristic peaks confirms the successful preparation of the GO@CS@CeO2 ternary composite material.

[0049] Experimental Example 1: Comparative Test of Static Adsorption Performance Test materials: GO@CS@CeO2 composite materials prepared in Examples 1-3, and comparative materials prepared in Comparative Examples 1-4.

[0050] Test conditions: initial arsenic concentration 10 mg / L (As(III) and As(V) were tested separately), dosage 0.5 g / L, pH=7, temperature 25℃, contact time 6 h. The residual arsenic concentration in the solution was determined by atomic fluorescence spectrometry, and the removal rate was calculated. Test results are shown below. Figure 4 See Table 1.

[0051] Table 1 Test Results:

[0052] The results above show that the GO@CS@CeO2 ternary composite materials prepared in Examples 1-3 of this invention have significantly higher removal rates of As(III) and As(V) than those in the comparative examples. In particular, Example 1 achieved a removal rate of 99.87% for As(III) and 98.81% for As(V). Comparing Comparative Example 2 (GO@CS) and Comparative Example 3 (GO@CeO2), it can be seen that neither introducing CS alone nor introducing CeO2 alone can achieve efficient removal of As(III) and As(V) simultaneously, while the synergistic effect of the ternary composite materials produces a technical effect of 1+1+1>3.

[0053] Experiment Example 2: pH Adaptability Test Test material: GO@CS@CeO2 composite material prepared in Example 1.

[0054] Test conditions: initial arsenic concentration 10 mg / L, dosage 0.5 g / L, temperature 25℃, contact time 6 h, initial pH adjusted to 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 respectively. The removal rates of As(III) and As(V) were determined.

[0055] like Figure 5 As shown, the material maintains high removal rates for both As(III) and As(V) over a wide pH range of 4-10. Below pH 4, the excessive protonation of chitosan's amino groups, while beneficial for As(V) adsorption, inhibits the oxidative activity of CeO2; above pH 10, OH... - Competition for adsorption sites with arsenate ions leads to a decrease in removal rate. The results indicate that the material of this invention exhibits excellent pH adaptability and is suitable for arsenic-containing water bodies with varying pH levels.

[0056] Experiment Example 3: Test on the Influence of Coexisting Ions Test material: GO@CS@CeO2 composite material prepared in Example 1.

[0057] Test conditions: initial arsenic concentration 10 mg / L (As(III)), dosage 0.5 g / L, pH=7, temperature 25℃, Na added separately. + K + Ca² + Mg² + (Concentrations were 10 ppm and 100 ppm), and the As(III) removal rate was determined.

[0058] like Figure 6 As shown, in the presence of coexisting ions, the As(III) removal rate remains above 99%, with a decrease of less than 1% compared to the absence of interference. This indicates that the material of the present invention has good selective adsorption capacity for arsenic and is suitable for actual wastewater treatment in complex water quality backgrounds.

[0059] Experiment Example 4: Regeneration and Reuse Performance Test Test material: GO@CS@CeO2 composite material prepared in Example 1.

[0060] Adsorption conditions: initial arsenic concentration 10 mg / L (As(III)), dosage 0.5 g / L, pH=7, 25℃, contact time 6 h. Desorption conditions: after adsorption saturation, soak in 0.1 mol / L NaOH solution for 2 h, rinse with deionized water until neutral, and then proceed to the next round of adsorption experiments. Number of cycles: 10.

[0061] like Figure 7As shown, after 10 adsorption-desorption cycles, the breakthrough adsorption capacity of the material remains above 80% of its initial value. This indicates that the material of the present invention has good regeneration performance and reusability stability, which is beneficial to reducing the cost of practical applications.

[0062] Experimental Example 5: Dynamic Column Adsorption Performance Test Test material: The material from Example 1.

[0063] Test Method: 10 mg of test material was mixed evenly with 1.5 g of quartz sand (40-80 mesh) and packed into an adsorption column (inner diameter 0.4 cm, column height 10 cm), with a bed height of 10 cm. Wastewater containing As(III) with an initial concentration of 10 mg / L was prepared and passed through the adsorption column at a flow rate of 0.2 BV / min (empty bed contact time EBCT was 5 min). Effluent was collected periodically, and the arsenic concentration was measured. A dynamic breakthrough curve was obtained by plotting the effluent arsenic concentration (C / C0) against the bed volume (BV). The bed volume (BV) at which the effluent arsenic concentration reached 10 μg / L (breakthrough point) was used as the evaluation index. Test results are shown below. Figure 8 .

[0064] like Figure 8 As shown, the dynamic permeation bed volume number of Example 1 reached 42.16 BV, which fully demonstrates that the introduction of chitosan not only provides adsorption sites, but more importantly, it constructs a stable three-dimensional network structure through chemical cross-linking, enabling the material to withstand dynamic water flow erosion and realizing the leap from powder materials to dynamic column technology.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A functionalized graphene composite material, characterized in that, The composite material comprises graphene oxide, chitosan chemically cross-linked with the graphene oxide, and cerium dioxide loaded on the surface of the graphene oxide-chitosan cross-linked composite.

2. A method for preparing the composite material of claim 1, characterized in that, Includes the following steps: Graphene oxide was dispersed in water, and a condensing agent and an acetic acid solution containing chitosan were added to carry out a cross-linking reaction. After centrifugation, washing, and drying, a graphene oxide-chitosan complex was obtained. The graphene oxide-chitosan complex was dispersed in water, a cerium source precursor solution was added, the pH was adjusted to alkaline, and after reaction, it was aged, washed and dried to obtain the final product.

3. The method according to claim 2, characterized in that, In the crosslinking reaction, the mass ratio of graphene oxide to chitosan is 1:1.5~2.5, preferably 1:2; The concentration of the acetic acid solution is 0.5-2%, preferably 1%, and the concentration of chitosan in the acetic acid solution is 0.5-2 mg / mL, preferably 2 mg / mL.

4. The method according to claim 2, characterized in that, The condensing agent is 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide.

5. The method according to claim 4, characterized in that, The mass ratio of the graphene oxide, chitosan, 1-ethyl-(3-dimethylaminopropyl)carbodiimide and N-hydroxysuccinimide is 1:(1.5~2.5):(1.5~2.5):(1~1.5).

6. The method according to claim 2, characterized in that, The crosslinking reaction was carried out at room temperature with stirring for 22-26 h in the dark.

7. The method according to claim 2, characterized in that, The mass ratio of the graphene oxide-chitosan composite to the cerium source precursor is 1:3~5; The cerium source precursor is cerium nitrate hexahydrate, and the concentration of the cerium source precursor solution is 15~25 mg / mL.

8. The method according to claim 2, characterized in that, The pH was adjusted to 9-10, and the reaction was stirred at room temperature for 1.5-3 hours after pH adjustment. The aging process is a low-temperature static aging process, with a temperature of 3-5℃, preferably 4℃, and a time of 23-25 ​​hours.

9. The method according to claim 2, characterized in that, The drying temperature is 50~80℃, and the time is 12~24h.

10. The application of the composite material of claim 1 or the composite material prepared by the method of any one of claims 2-9 in the removal of arsenic from groundwater, industrial wastewater or drinking water.

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