Graphene oxide grafted mercaptosuccinic acid, and preparation method and application thereof

Abstract

This application relates to the field of adsorption technology, specifically to a graphene oxide-grafted mercaptosuccinic acid, its preparation method, and its application. The preparation method of graphene oxide-grafted mercaptosuccinic acid includes: providing a first mixture containing graphene oxide; providing a second mixture containing mercaptosuccinic acid; providing a third mixture containing an initiator; mixing the second mixture, the third mixture, and the first mixture, and then performing a mercapto-ene click reaction to obtain a fourth mixture; washing the fourth mixture alternately with an alcohol solution and pure water to obtain graphene oxide-grafted mercaptosuccinic acid. The preparation method of this application improves the adsorption effect of graphene oxide-grafted mercaptosuccinic acid and significantly improves its adsorption cycle performance, further expanding the application potential of graphene oxide in the field of water treatment.

Description

Technical Field

[0001] This application relates to the field of adsorption technology, specifically to a graphene oxide-grafted mercaptosuccinic acid, its preparation method, and its application. Background Technology

[0002] Water pollution leading to water scarcity has severely impacted human life and sustainable development, making water pollution a major challenge facing the world today. Adsorption, due to its advantages such as being environmentally friendly, simple to operate, low-cost, and recyclable, has become a cost-effective wastewater treatment technology. As the core of adsorption technology, improving the economic efficiency and adsorption performance of adsorbents is key to optimizing and upgrading adsorption technology. Summary of the Invention

[0003] This application provides a graphene oxide grafted with mercaptosuccinic acid, its preparation method, and its application. This method improves the adsorption effect of graphene oxide grafted with mercaptosuccinic acid and significantly enhances the adsorption cycle performance of graphene oxide grafted with mercaptosuccinic acid, further expanding the application potential of graphene oxide in the field of water treatment.

[0004] In a first aspect, this application provides a method for preparing graphene oxide-grafted mercaptosuccinic acid, comprising: providing a first mixture containing graphene oxide; providing a second mixture containing mercaptosuccinic acid; providing a third mixture containing an initiator; mixing the second mixture, the third mixture, and the first mixture, and then performing a mercapto-ene click reaction to obtain a fourth mixture; and washing the fourth mixture alternately with an alcohol solution and pure water to obtain graphene oxide-grafted mercaptosuccinic acid.

[0005] In some embodiments, the thiosuccinic acid includes a carboxyl group and a thiol group.

[0006] In some embodiments, the initiator includes one or more of azobisisobutyronitrile and azobiscyclohexylformitrile.

[0007] In some embodiments, the mass ratio of graphene oxide to mercaptosuccinic acid is 1:(0.5-3.5).

[0008] In some embodiments, the mass ratio of the mercaptosuccinic acid to the initiator is (2.5-5.5):1.

[0009] In some embodiments, the mercapto-alkene click reaction is carried out under an inert atmosphere and in the dark.

[0010] In some embodiments, the reaction time of the mercapto-alkene click reaction is 12h-36h.

[0011] In some embodiments, the reaction temperature of the mercapto-alkene click reaction is 50°C-70°C.

[0012] In some embodiments, the solvent of the first mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0013] In some embodiments, the solvent of the second mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0014] In some embodiments, the solvent of the third mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0015] In some embodiments, based on the total mass of the graphene oxide, the mass content of carbon in the graphene oxide is ≤46%, the mass content of oxygen is ≥52%, and the mass content of sulfur is <1.5%.

[0016] In some embodiments, the mass ratio of the graphene oxide to the solvent in the first mixture is 1:(70-80). In some embodiments, the mass ratio of the mercaptosuccinic acid to the solvent in the second mixture is 1:(15-25).

[0017] In some embodiments, the mass ratio of the initiator to the solvent in the third mixture is 1:(15-25).

[0018] In some embodiments, the alcohol solution includes one or more of methanol, ethanol, n-propanol, and isopropanol.

[0019] In some embodiments, the volume ratio of the fourth mixture to the alcohol solution is 1:(5-20).

[0020] Secondly, this application provides graphene oxide grafted with mercaptosuccinic acid, which is prepared by the preparation method described in the first aspect.

[0021] Thirdly, this application provides the application of graphene oxide grafted with mercaptosuccinic acid prepared by the preparation method described in the first aspect or the graphene oxide grafted with mercaptosuccinic acid described in the second aspect in water pollution control.

[0022] This application demonstrates a thiol-alkene reaction between the thiol group (-SH) in mercaptosuccinic acid and the unsaturated double bond (C=C) in graphene oxide under the action of an initiator. The carboxyl group is then attached to the graphene oxide structure via a thiol-alkene reaction between the thiol group in mercaptosuccinic acid and the alkenyl group in graphene oxide. This efficiently introduces carboxyl groups into graphene oxide, significantly improving the adsorption effect of thiol-succinic acid grafted onto graphene oxide, especially for malachite green and ofloxacin, and greatly enhancing the adsorption cycle performance of thiol-succinic acid grafted onto graphene oxide. It also effectively enhances the surface polarity of graphene oxide, constructing active sites that can form coordination interactions with heavy metal ions. The strong chemical bonds, such as coordination bonds, significantly improve the adsorption efficiency and selectivity of graphene oxide. Furthermore, the introduction of surface functional groups allows for precise control of the material's hydrophilicity and hydrophobicity, improving its dispersion stability in complex aquatic environments, thereby expanding the application potential of graphene oxide in the field of water treatment.

[0023] In addition, graphene oxide has the advantages of being widely available, non-toxic, green and environmentally friendly, and free from secondary pollution. Moreover, the above preparation method is simple to operate and the reaction conditions are mild, making it suitable for large-scale industrial production and industrial promotion. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0025] Figure 1 This is a schematic diagram illustrating the preparation principle of graphene oxide grafted with mercaptosuccinic acid in this application. Figure 2 Infrared spectra of graphene oxide and the graphene oxide grafted with mercaptosuccinic acid prepared in Example 1. Figure 3 The scanning electron microscope image and corresponding energy-dispersive X-ray spectra of the graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 are shown. Figure 4 The scanning electron microscope image and corresponding energy-dispersive X-ray spectra of the graphene oxide grafted with mercaptosuccinic acid prepared in Example 2 are shown. Figure 5 The scanning electron microscope image and corresponding energy-dispersive X-ray spectra of the graphene oxide grafted with mercaptosuccinic acid prepared in Example 3 are shown. Figure 6 The image shows a scanning electron microscope (SEM) image and a corresponding energy-dispersive X-ray diffraction (EDXRD) spectrum of graphene oxide from Comparative Example 1. Figure 7The results of the cyclic adsorption test of malachite green and ofloxacin on graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 are shown. Figure 8 The graph shows the adsorption effect of graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 on the single-component pollutants malachite green or ofloxacin under different pH conditions. Figure 9 The graph shows the adsorption effect of graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 on the two-component pollutants malachite green and ofloxacin under different pH conditions. Detailed Implementation

[0026] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of this application.

[0027] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification, claims and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0028] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0029] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0030] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two).

[0031] Unless otherwise stated, the test temperature for all parameters mentioned in this application is 25°C.

[0032] Graphene oxide, as an important derivative of graphene, has few surface-active adsorption sites, and its adsorption process relies solely on weak van der Waals forces. This results in poor selectivity and limited adsorption capacity for target pollutants, making it difficult to meet water treatment requirements. Introducing polar functional groups such as -OH and -COOH through surface modification has become a key strategy to improve the adsorption performance of graphene oxide.

[0033] In view of this, this application provides a method for preparing graphene oxide grafted with mercaptosuccinic acid, comprising: Provide a first mixture containing graphene oxide; Provide a second mixture containing mercaptosuccinic acid; Provide a third mixture containing an initiator; The second mixture, the third mixture, and the first mixture are mixed and then subjected to a mercapto-olefin click reaction to obtain a fourth mixture. The fourth mixture was washed alternately with an alcohol solution and pure water to obtain graphene oxide-grafted mercaptosuccinic acid.

[0034] This application demonstrates a thiol-alkene reaction between the thiol group (-SH) in mercaptosuccinic acid and the unsaturated double bond (C=C) in graphene oxide under the action of an initiator. The carboxyl group is then attached to the graphene oxide structure via a thiol-alkene reaction between the thiol group in mercaptosuccinic acid and the alkenyl group in graphene oxide. This efficiently introduces carboxyl groups into graphene oxide, significantly improving the adsorption effect of thiol-succinic acid grafted onto graphene oxide, especially for malachite green and ofloxacin, and greatly enhancing the adsorption cycle performance of thiol-succinic acid grafted onto graphene oxide. It also effectively enhances the surface polarity of graphene oxide, constructing active sites that can form coordination interactions with heavy metal ions. The strong chemical bonds, such as coordination bonds, significantly improve the adsorption efficiency and selectivity of graphene oxide. Furthermore, the introduction of surface functional groups allows for precise control of the material's hydrophilicity and hydrophobicity, improving its dispersion stability in complex aquatic environments, thereby expanding the application potential of graphene oxide in the field of water treatment.

[0035] In addition, graphene oxide has the advantages of being widely available, non-toxic, green and environmentally friendly, and free from secondary pollution. Moreover, the above preparation method is simple to operate and the reaction conditions are mild, making it suitable for large-scale industrial production and industrial promotion.

[0036] In some embodiments, the mercaptosuccinic acid includes a carboxyl group and a mercapto group.

[0037] Mercaptosuccinic acid contains two carboxyl groups, providing abundant active sites for the adsorption process; its good hydrophilicity also helps improve the dispersibility and adsorption efficiency of the modified material in the aqueous phase. Other thiols, such as the amino groups in sulfur-containing amino acids, may participate in the reaction; aromatic thiols have a strong odor and high toxicity; monofunctional alkyl thiols lack functional sites and cannot achieve subsequent functionalization modification.

[0038] Figure 1 This diagram illustrates the preparation principle of graphene oxide grafted with mercaptosuccinic acid in this application. By introducing carboxyl groups into the graphene oxide structure, the number of adsorption active sites on the surface of graphene oxide grafted with mercaptosuccinic acid is increased, significantly improving the adsorption capacity of graphene oxide grafted with mercaptosuccinic acid and enhancing its adsorption-desorption cycle capability.

[0039] In some embodiments, the initiator includes one or more of azobisisobutyronitrile and azobiscyclohexylformitrile.

[0040] By selecting the above-mentioned initiators, the intermediates can be stabilized and side reactions reduced, and the reaction rate of thiolation and carboxyl grafting can also be improved.

[0041] In some embodiments, the mass ratio of graphene oxide to mercaptosuccinic acid is 1:(0.5-3.5), for example, it can be 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.3, 1:1.5, 1:1.7, 1:2, 1:2.3, 1:2.5, 1:2.7, 1:3, 1:3.3, 1:3.5, or a range of any two of the above values, and can be selected as 1:(1.8-2.2).

[0042] Excess mercaptosuccinic acid may lead to intermolecular or intramolecular crosslinking, reducing reaction efficiency; insufficient mercaptosuccinic acid means inadequate supply of thiol reagent, resulting in incomplete thiol-alkene click reactions and a decrease in the thiol grafting rate in thiolized graphene oxide. Maintaining a mass ratio of graphene oxide to mercaptosuccinic acid within the aforementioned range allows for effective reaction between the reactants, improving the thiol grafting efficiency of graphene oxide.

[0043] In some embodiments, the mass ratio of the mercaptosuccinic acid to the initiator is (2.5-5.5):1, for example, it can be 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, or any range of two of the above values.

[0044] A mass ratio of mercaptosuccinic acid to initiator within the above range helps to improve the reaction rate and efficiency of the thiolation reaction.

[0045] In some embodiments, the mercapto-alkene click reaction is carried out under an inert atmosphere and in the dark.

[0046] The mercapto-olefin click reaction proceeds under light-shielded conditions. In the alkaline microenvironment, the mercapto groups directly attack the more abundant and widely distributed epoxy groups on the surface of graphene oxide (GO), resulting in a nucleophilic ring-opening reaction. Under light-shielded conditions, an alcohol hydroxyl group is generated at each grafting site, forming a β-hydroxy sulfide structure. This provides abundant hydrogen bond formation sites for the material. Each additional oxygen-containing polar site means a lower binding energy barrier with water molecules, endowing the adsorbent with stronger surface wettability and lower layer stacking driving force. Compared to the aggregation tendency of light-irradiated products due to localized hydrophobic sulfide segments, the effective specific surface area and site accessibility of the light-shielded product are significantly improved, macroscopically manifested as a significant leap in saturated adsorption capacity.

[0047] Furthermore, the light-protected conditions eliminate the need for photoinitiators, avoiding common side reactions in the free radical pathway, such as the self-coupling of thiol groups to form disulfides, thus preserving the original surface chemical information and reaction predictability of GO to the greatest extent. Utilizing the inherent epoxy enrichment properties of GO, more efficient, water-saving, and structurally richer grafting was achieved.

[0048] In some embodiments, the inert atmosphere may be one or more of nitrogen, argon, and helium.

[0049] In some embodiments, the reaction time of the mercapto-alkene click reaction is 12h-36h, for example, it can be 12h, 15h, 18h, 21h, 24h, 27h, 30h, 33h, 36h, or any range of two of the above values, and can be selected as 21h-27h.

[0050] Within the above-mentioned range, the reaction time of the mercapto-alkene click reaction can be controlled to regulate the degree of reaction, thereby optimizing product performance and improving reaction efficiency.

[0051] In some embodiments, the reaction temperature of the mercapto-alkene click reaction is 50°C-70°C, for example, 50°C, 53°C, 56°C, 60°C, 63°C, 66°C, 70°C, or any two of the above values, specifically 56°C-63°C. This allows the mercapto-alkene click reaction to proceed smoothly.

[0052] In some embodiments, the solvent of the first mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0053] In some embodiments, the solvent of the second mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0054] In some embodiments, the solvent of the third mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

[0055] In some embodiments, based on the total mass of the graphene oxide, the mass content of carbon in the graphene oxide is ≤46%, the mass content of oxygen is ≥52%, and the mass content of sulfur is <1.5%.

[0056] In some embodiments, based on the total mass of the graphene oxide, the carbon content in the graphene oxide is 44%-46% and the oxygen content is 52%-54%.

[0057] Normally, hydroxyl, epoxy, and carboxyl groups are free radical quenching sites. If the oxygen content in graphene oxide is too high, GO will consume the primary free radicals in the system, which may require thermal initiators for compensation. Under high temperature conditions, epoxy and hydroxyl groups on the GO surface are easily reduced, consuming surface -SH and causing thiol loss. If the oxygen content in graphene oxide is too low, the hydrogen bonds and electrostatic repulsion between the sheets are weak, making it difficult for GO to be completely peeled off. A large number of sheets stacked together may lose reaction sites.

[0058] In some embodiments, the mass ratio of the graphene oxide to the solvent in the first mixture is 1:(70-80).

[0059] In some embodiments, the mass ratio of the mercaptosuccinic acid to the solvent in the second mixture is 1:(15-25).

[0060] In some embodiments, the mass ratio of the initiator to the solvent in the third mixture is 1:(15-25).

[0061] In some embodiments, the alcohol solution includes one or more of methanol, ethanol, n-propanol, and isopropanol.

[0062] In some embodiments, the alcohol solution includes ethanol.

[0063] In some embodiments, the volume ratio of the fourth mixture to the alcohol solution is 1:(5-20), for example, it can be 1:5, 1:10, 1:15, 1:20, or optionally 1:(10-15).

[0064] In some embodiments, the volume ratio of the fourth mixed solution to the pure water is 1:(5-20), for example, it can be 1:5, 1:10, 1:15, 1:20, or optionally 1:(10-15).

[0065] In some embodiments, the preparation method further includes: washing the fourth mixture with an alcohol solution and pure water, separating the solid by centrifugation or filtration and drying it to obtain graphene oxide-grafted mercaptosuccinic acid.

[0066] The graphene oxide grafted with mercaptosuccinic acid prepared in this application can be used in water pollution control.

[0067] Malachite green and ofloxacin possess strong hydrophilicity and high hydration energy, which hinders their access to the hydrophobic surface of the adsorbent. In the graphene oxide-grafted mercaptosuccinic acid prepared in this application, carboxyl groups are introduced. The electrostatic interaction between the anionic carboxyl group and the cationic groups such as the dimethylimine and piperazine groups in malachite green and ofloxacin significantly enhances the adsorption effect of graphene oxide-grafted mercaptosuccinic acid on malachite green and ofloxacin. After multiple cycles of adsorption-desorption, graphene oxide-grafted mercaptosuccinic acid can still maintain good adsorption performance for malachite green and ofloxacin.

[0068] Example The following embodiments describe the contents of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0069] Example 1 (1) Graphene oxide and N,N-dimethylformamide solution were mixed at a mass ratio of 1:75 to obtain a first mixture containing graphene oxide. (2) Mix mercaptosuccinic acid and N,N-dimethylformamide solution at a mass ratio of 1:20 to obtain a second mixture containing mercaptosuccinic acid; (3) Azobisisobutyronitrile and N,N-dimethylformamide solution were mixed in a mass ratio of 1:20 to obtain a third mixture containing an initiator; (4) The second and third mixtures were rapidly added dropwise to the first mixture. The mass ratio of graphene oxide to mercaptosuccinic acid was 1:2, and the mass ratio of mercaptosuccinic acid to azobisisobutyronitrile was 3:1. The mixture was heated to 60°C and stirred for 24 hours under nitrogen protection to carry out mercapto-olefin click reaction, and a fourth mixture containing graphene oxide grafted with mercaptosuccinic acid was obtained. (5) The fourth mixture was washed 4 times alternately in ethanol solution and pure water. The volume ratio of ethanol solution to the fourth mixture was 10:1, and the volume ratio of pure water to the fourth mixture was 10:1. The washing product was filtered and the filtered material was dried at 60°C to obtain graphene oxide grafted mercaptosuccinic acid.

[0070] Example 2 (1) Graphene oxide and N,N-dimethylformamide solution were mixed at a mass ratio of 1:75 to obtain a first mixture containing graphene oxide. (2) Mix mercaptosuccinic acid and N,N-dimethylformamide solution at a mass ratio of 1:20 to obtain a second mixture containing mercaptosuccinic acid; (3) Azobisisobutyronitrile and N,N-dimethylformamide solution were mixed in a mass ratio of 1:20 to obtain a third mixture containing an initiator; (4) The second and third mixtures were rapidly added dropwise to the first mixture. The mass ratio of graphene oxide to mercaptosuccinic acid was 1:1, and the mass ratio of mercaptosuccinic acid to azobisisobutyronitrile was 3:1. The mixture was heated to 60°C and stirred for 24 hours under nitrogen protection to carry out mercapto-olefin click reaction, and a fourth mixture containing graphene oxide grafted with mercaptosuccinic acid was obtained. (5) The fourth mixture was washed 4 times alternately in ethanol solution and pure water. The volume ratio of ethanol solution to the fourth mixture was 10:1, and the volume ratio of pure water to the fourth mixture was 10:1. The washing product was filtered and the filtered material was dried at 60°C to obtain graphene oxide grafted mercaptosuccinic acid.

[0071] Example 3 (1) Graphene oxide and N,N-dimethylformamide solution were mixed at a mass ratio of 1:75 to obtain a first mixture containing graphene oxide. (2) Mix mercaptosuccinic acid and N,N-dimethylformamide solution at a mass ratio of 1:20 to obtain a second mixture containing mercaptosuccinic acid; (3) Azobisisobutyronitrile and N,N-dimethylformamide solution were mixed in a mass ratio of 1:20 to obtain a third mixture containing an initiator; (4) The second and third mixtures were rapidly added dropwise to the first mixture. The mass ratio of graphene oxide to mercaptosuccinic acid was 1:3, and the mass ratio of mercaptosuccinic acid to azobisisobutyronitrile was 3:1. The mixture was heated to 60°C and stirred for 24 hours under nitrogen protection to carry out mercapto-olefin click reaction, and a fourth mixture containing graphene oxide grafted with mercaptosuccinic acid was obtained. (5) The fourth mixture was washed 4 times alternately in ethanol solution and pure water. The volume ratio of ethanol solution to the fourth mixture was 10:1, and the volume ratio of pure water to the fourth mixture was 10:1. The washing product was filtered and the filtered material was dried at 60°C to obtain graphene oxide grafted mercaptosuccinic acid.

[0072] Example 4 Except for step (4), in which the stirring time is 12h under nitrogen, the preparation method of graphene oxide grafted with mercaptosuccinic acid is the same as in Example 1.

[0073] Example 5 Except for step (4), in which the mixed solution is heated to 50°C, the preparation method of graphene oxide grafted with mercaptosuccinic acid is the same as in Example 1.

[0074] Example 6 Except for step (4), in which the mixture is stirred for 24 hours under nitrogen atmosphere without light protection, the preparation method of graphene oxide grafted with mercaptosuccinic acid is the same as in Example 1.

[0075] Comparative Example 1 The difference from Example 1 is that steps (2), (3) and (4) are omitted.

[0076] Graphene oxide and N,N-dimethylformamide solution were mixed at a mass ratio of 1:75 to obtain a first mixture containing graphene oxide. The first mixture was washed four times alternately with ethanol solution and pure water, with a volume ratio of ethanol solution to the first mixture of 10:1 and a volume ratio of pure water to the first mixture of 10:1. The filtered material was then dried at 60°C to obtain graphene oxide.

[0077] Comparative Example 2 Except for replacing mercaptosuccinic acid with mercaptoacetic acid, the preparation method of graphene oxide grafted with mercaptosuccinic acid is the same as in Example 1.

[0078] Test section (1) Infrared spectroscopy test The infrared spectrometer used was a NEXUS 670, manufactured by Nicolet Corporation, USA. Sample preparation method: Approximately 1 mg of dry solid sample and approximately 100 mg of dry KBr powder were thoroughly ground in an agate mortar to ensure uniform mixing. The mixed powder was then placed into a tableting mold, and a vacuum was applied for approximately 2 minutes to remove trace amounts of moisture. The tablets were then pressed at approximately 10 MPa for approximately 1 minute to obtain transparent or uniformly translucent tablets. Testing procedure: The scanning range was set to 4000–400 cm⁻¹ in the software. - ¹, Scan 16 times - Collect background spectrum - Collect sample spectrum - Save spectrum.

[0079] (2) Scanning electron microscopy test The scanning electron microscope used was a Hitachi S-4800, manufactured by Nicolet Corporation, USA. Sample preparation method: For dry samples with relatively large particle sizes, a needle-tip-sized amount of powder was sprinkled directly onto conductive adhesive. Any loose powder was blown away with a bulb syringe. The sample was then sputtered with gold. Testing procedure: A low voltage of 5kV was set. Appropriate distance, contrast, and brightness were adjusted. Images were acquired and saved.

[0080] (3) Adsorption performance test (3-1) Adsorption performance of graphene oxide-grafted mercaptosuccinic acid for pollutants (malachite green, ofloxacin) Adsorption performance test of malachite green: Dissolve malachite green in water to obtain 50 mL of malachite green aqueous solution with an initial concentration of 100 mg / L. Add HCl solution or NaOH solution to adjust the pH to 10, and then add 10 mg of graphene oxide grafted mercaptosuccinic acid. Stir at 500 r / min at room temperature. Take the supernatant every 60 min to measure the absorbance. When the absorbance of two adjacent times is basically unchanged (change ±5%), it is determined that the graphene oxide grafted mercaptosuccinic acid has reached adsorption equilibrium. By constructing a standard curve, the absorbance test results are converted into the concentration of pollutants after adsorption equilibrium. Then, the adsorption capacity of graphene oxide grafted mercaptosuccinic acid for malachite green is calculated using formula (1).

[0081] Adsorption performance test of ofloxacin: Ofloxacin was dissolved in water to obtain 50 mL of ofloxacin aqueous solution with an initial concentration of 50 mg / L. HCl solution or NaOH solution was added to adjust the pH to 6. Then 10 mg of graphene oxide grafted mercaptosuccinic acid was added. The mixture was stirred at 500 r / min at room temperature. The absorbance of the supernatant was measured every 60 min. When the absorbance of two adjacent samples remained basically unchanged (change ±5%), it was determined that the graphene oxide grafted mercaptosuccinic acid had reached adsorption equilibrium. By constructing a standard curve, the absorbance test results were converted into the concentration of pollutants after adsorption equilibrium. Then, the adsorption capacity of graphene oxide grafted mercaptosuccinic acid for ofloxacin was calculated using formula (1).

[0082] (1) In the formula Q t V represents the adsorption capacity (mg / g); V represents the volume of the pollutant solution (L); CO and C t , respectively, represent the pollutant concentrations (mg / L) in the solution before and after adsorption; m represents the mass of the added adsorbent (mg).

[0083] (3-2) Cyclic test of the adsorption performance of graphene oxide-grafted mercaptosuccinic acid for malachite green and ofloxacin The cyclic test method for adsorption performance: Referring to (3-2), an adsorption test was first conducted, followed by separation of graphene oxide-grafted mercaptosuccinic acid by vacuum filtration and desorption treatment. Ethanol solution was used for desorption. The graphene oxide-grafted mercaptosuccinic acid with adsorbed pollutants was placed in the ethanol solution and stirred at 500 r / min for 6 hours at room temperature. Then, the adsorbent was separated and dried. The dried adsorbent underwent repeated adsorption-desorption treatment six times. The removal efficiency for each time was calculated using formula (2).

[0084] (2) In the formula, C0 and C e The values ​​represent the pollutant concentrations (mg / L) in the solution before adsorption and at adsorption equilibrium, respectively.

[0085] (3-3) pH adaptability test of graphene oxide-grafted mercaptosuccinic acid to single-component pollutants (malachite green or ofloxacin) Seven malachite green solutions were prepared with pH values ​​of 2, 3, 4, 5, 6, and 7, respectively. The adsorption capacity of graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 for malachite green under different pH conditions was tested. The test method was the same as in (3-1).

[0086] Nine ofloxacin solutions were prepared with pH values ​​of 2, 3, 4, 5, 6, 7, 8, 9, and 10, respectively. The adsorption capacity of the graphene oxide-grafted mercaptosuccinic acid prepared in Example 1 for ofloxacin under different pH conditions was tested. The test method was the same as in (3-1).

[0087] (3-4) pH adaptability test of graphene oxide-grafted mercaptosuccinic acid to two-component pollutants (malachite green and ofloxacin) Prepare solutions of the two-component pollutants malachite green and ofloxacin, with pH values ​​of 2, 3, 4, 5, 6, and 7 respectively. The initial concentration of malachite green in the two-component pollutant malachite green and ofloxacin solutions is 100 mg / L, and the initial concentration of ofloxacin is 50 mg / L. The adsorption capacity is tested using the same method as in (3-1), and the adsorption efficiency is tested using the same method as in (3-2).

[0088] Figure 2 The infrared spectra of graphene oxide and the graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 are shown in the figure. Figure 2 It can be seen that in the infrared spectrum of graphene oxide grafted with mercaptosuccinic acid, at 660 cm⁻¹... -1The characteristic peaks appearing on the left and right are characteristic peaks of carbon-sulfur-carbon (CSC), indicating that the carboxyl group in mercaptosuccinic acid was successfully linked to the graphene oxide structure through a click reaction between the mercapto group in mercaptosuccinic acid and the mercapto-alkene of the unsaturated double bond in graphene oxide.

[0089] Figure 3 , Figure 4 , Figure 5 The scanning electron microscope (SEM) images and corresponding energy-dispersive X-ray diffraction (EDXRD) spectra of the graphene oxide-grafted mercaptosuccinic acid prepared in Examples 1, 2, and 3 are shown below. Figure 3-5 It can be seen that graphene oxide grafted with mercaptosuccinic acid exhibits an aggregated state, and the corresponding energy dispersive X-ray spectra all show a uniform distribution of sulfur. The surface of graphene oxide is finely granular, and the surface morphology of graphene oxide before and after grafting with mercaptosuccinic acid is quite different. Graphene oxide grafted with mercaptosuccinic acid has a larger adsorption area, which is beneficial to improving its adsorption effect.

[0090] Figure 6 The image shows a scanning electron microscope (SEM) image and the corresponding energy-dispersive X-ray diffraction (EDXRD) spectrum of graphene oxide from Comparative Example 1; Figure 6 It is known that the surface of graphene oxide is composed of many irregular small particles, which are rough and fragmented with few effective pore structures, thus failing to provide sufficient and stable adsorption space. Therefore, this surface structure is not conducive to the adsorption and removal of pollutants.

[0091] The adsorption performance of graphene oxide grafted with mercaptosuccinic acid prepared in Examples 1-6 and Comparative Examples 1-2 on pollutants (malachite green and ofloxacin) is shown in Table 1.

[0092] Table 1

[0093] As shown in Table 1, the graphene oxide grafted with mercaptosuccinic acid prepared in the embodiments of this application has good adsorption properties for malachite green and ofloxacin.

[0094] Figure 7 The results of the cyclic adsorption tests on malachite green and ofloxacin for the graphene oxide-grafted mercaptosuccinic acid prepared in Example 1 are presented below. Figure 7 It can be seen that graphene oxide grafted with mercaptosuccinic acid exhibits good stability in the removal efficiency of malachite green and ofloxacin during the cycling process. After six cycles, the removal efficiency of malachite green can be maintained above 70%, and the removal efficiency of ofloxacin can be maintained above 60%. This indicates that the adsorption performance of graphene oxide grafted with mercaptosuccinic acid has good stability and can be reused multiple times.

[0095] Figure 8The graphs show the adsorption effects of graphene oxide grafted with mercaptosuccinic acid prepared in Example 1 on the single-component pollutants malachite green or ofloxacin under different pH conditions. Figure 8 It is known that graphene oxide grafted with mercaptosuccinic acid has a wide adaptability to the acidity and alkalinity of water, functioning in strongly acidic, weakly acidic, neutral, and weakly alkaline environments. Figure 8 It is also known that graphene oxide grafted with mercaptosuccinic acid has a wide range of adaptability to the acidity and alkalinity of water, and can be used in strong acid, weak acid, neutral and weak alkaline environments.

[0096] Figure 9 The graphs show the adsorption effects of the graphene oxide-grafted mercaptosuccinic acid prepared in Example 1 on the two-component pollutants malachite green and ofloxacin under different pH conditions. Figure 9 It is known that malachite green and ofloxacin generally compete for adsorption, which means that adsorbents that adsorb malachite green or ofloxacin alone can have a high adsorption capacity. However, when adsorbing malachite green and ofloxacin simultaneously, the adsorption capacity of each decreases. But the graphene oxide-grafted mercaptosuccinic acid prepared using the method described in this application maintains essentially unchanged adsorption capacity for both malachite green and ofloxacin in weakly acidic, neutral, weakly alkaline, and strongly alkaline environments.

[0097] The above embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing graphene oxide grafted with mercaptosuccinic acid, characterized in that, include: Provide a first mixture containing graphene oxide; Provide a second mixture containing mercaptosuccinic acid; Provide a third mixture containing an initiator; The second mixture, the third mixture, and the first mixture are mixed and then subjected to a mercapto-olefin click reaction to obtain a fourth mixture. The fourth mixture was washed alternately with an alcohol solution and pure water to obtain graphene oxide-grafted mercaptosuccinic acid.

2. The preparation method according to claim 1, characterized in that, The thiosuccinic acid includes carboxyl and thiol groups.

3. The preparation method according to claim 1, characterized in that, The initiator includes one or more of azobisisobutyronitrile and azobiscyclohexylformitrile.

4. The preparation method according to claim 1, characterized in that, The mass ratio of graphene oxide to mercaptosuccinic acid is 1:(0.5-3.5); and / or, The mass ratio of the mercaptosuccinic acid to the initiator is (2.5-5.5):

1.

5. The preparation method according to claim 1, characterized in that, The mercapto-alkene click reaction is carried out under an inert atmosphere and in the dark; and / or, The reaction time for the mercapto-olefin click reaction is 12h-36h; and / or, The reaction temperature for the mercapto-alkene click reaction is 50℃-70℃.

6. The preparation method according to claim 1, characterized in that, The solvent of the first mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide; and / or, The solvent for the second mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide; and / or, The solvent of the third mixture includes one or more of N,N-dimethylformamide and N,N-dimethylacetamide; and / or, Based on the total mass of the graphene oxide, the carbon content in the graphene oxide is ≤46%, the oxygen content is ≥52%, and the sulfur content is <1.5%.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the graphene oxide to the solvent in the first mixture is 1:(70-80); and / or, The mass ratio of the mercaptosuccinic acid to the solvent in the second mixture is 1:(15-25); and / or, The mass ratio of the initiator to the solvent in the third mixture is 1:(15-25).

8. The preparation method according to claim 1, characterized in that, The alcohol solution includes one or more of methanol, ethanol, n-propanol, and isopropanol; and / or, The volume ratio of the fourth mixture to the alcohol solution is 1:(5-20).

9. A graphene oxide-grafted mercaptosuccinic acid, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of graphene oxide grafted with mercaptosuccinic acid prepared by the preparation method according to any one of claims 1-8 or the graphene oxide grafted with mercaptosuccinic acid according to claim 9 in water pollution control.

Images