Composite material, synthesis method of composite material and method of absorbing ethidium bromide

Abstract

A composite material includes a graphene oxide and a sodium alginate. The graphene oxide is powdery. A degree of polymerization of the sodium alginate is

Description

Technical field

[0001] This disclosure is about a composite material, a synthesis method of the composite material and a method of adsorbing ethidium bromide, especially a composite material with high efficiency for adsorbing ethidium bromide and easy solid-liquid two-phase separation, a synthesis method of the composite material and a method of adsorbing ethidium bromide. Prior technology

[0002] With the development of science and technology, ethidium bromide has been widely used with its high efficiency and cheap characteristics, which has led to the gradual problem of ethidium bromide pollution in the water environment. Seriously, ethidium bromide is a toxic substance and can cause irreversible harm to the human body.

[0003] The commonly known powder material can purify wastewater containing ethidium bromide by using the principle of adsorption to remove ethidium bromide from sewage. Although the powder material can effectively adsorb ethidium bromide, the powder material has the disadvantage of suspension, when the powder material is suspended in aquatic environment or sewage water body, causing the solid-liquid two phases are not easy to separate, which is not conducive to environmental remediation.

[0004] In view of this, the development of a material with efficient adsorption of ethidium bromide and easy solid-liquid two-phase separation became the goal of the relevant industry efforts. Invention content

[0005] The purpose of the present disclosure is to provide an efficient adsorption of ethidium bromide and a composite material that is easy to separate solid-liquid two-phase, a synthesis method of the composite material and a method of adsorbing ethidium bromide.

[0006] One embodiment of the content of the present elucidation provides a composite material comprising graphene monoxide and sodium monoalginate. Graphene oxide is in powder form and the degree of primary polymerization of sodium alginate is 100 to 1000. The total weight of the composites was given as 100% and the one weight ratio of graphene oxide was 40% to 60%. The composites are granular, and the one average particle size of the composites is 0.5 mm to 2.0 mm.

[0007] According to the aforementioned composites, where the total weight of the composites is taken as 100%, the weight ratio of graphene oxide can be 50%, and the average particle size of the composites can be 1.0 mm to 1.5 mm.

[0008] Another embodiment of this disclosure provides a method for synthesizing a composite material, comprising the following steps: adding graphene oxide to an aqueous solution of sodium alginate and stirring to dissolve it, thereby forming a gel solution. The gel solution is then contacted with a coagulation bath, allowing the gel solution to react with the coagulation bath and solidify into a plurality of composite materials. The graphene oxide is in powder form, and the degree of polymerization of the sodium alginate is 100 to 1000. The total weight of the composite materials, on a 100% basis, includes 40% to 60% graphene oxide by weight. The composite materials are granular, and the average particle size of the composite materials is 0.5 mm to 2.0 mm.

[0009] According to the aforementioned method for synthesizing composite materials, the coagulation bath may contain calcium chloride, and the concentration of calcium chloride in the coagulation bath may be from 0.1% to 74.5%.

[0010] According to the aforementioned method for synthesizing composite materials, the total weight of the composite material is 100%, the weight ratio of graphene oxide can be 50%, and the average particle size of the composite material can be 1.0 mm to 1.5 mm.

[0011] According to the aforementioned method for synthesizing composite materials, the stirring time for dissolving graphene oxide in an aqueous solution of sodium alginate can be greater than or equal to 6 hours.

[0012] According to the aforementioned method for synthesizing composite materials, the reaction time of the gel solution reacting with the coagulation bath and solidifying can be greater than or equal to 6 hours.

[0013] Another embodiment of this disclosure provides a method for adsorbing ethidium bromide, comprising placing a composite material into an aqueous solution of ethidium bromide, thereby allowing the composite material to adsorb ethidium bromide from the aqueous solution. The composite material comprises graphene monoxide and sodium alginate, wherein the graphene oxide is in powder form, and the degree of polymerization of the sodium alginate is 100 to 1000. The total weight of the composite material is 100%, and the weight percentage of graphene oxide is 40% to 60%. The composite material is granular, and the average particle size of the composite material is 0.5 mm to 2.0 mm.

[0014] According to the aforementioned method for adsorbing ethidium bromide, the pH value of the ethidium bromide aqueous solution can be from 2.0 to 11.0.

[0015] According to the aforementioned method for adsorbing ethidium bromide, the total weight of the composite material is 100%, the weight ratio of graphene oxide can be 50%, and the average particle size of the composite material can be 1.0 mm to 1.5 mm.

[0016] Accordingly, the composite material, its synthesis method, and the method for adsorbing ethidium bromide disclosed herein, by selecting a specific degree of polymerization of sodium alginate, can effectively improve the stability and uniformity of the composite material and significantly enhance its mechanical strength. Furthermore, by selecting a specific proportion of graphene oxide, the composite material exhibits efficient adsorption of ethidium bromide and facilitates solid-liquid phase separation. Simple Explanation of the Diagram

[0017] Figure 1 illustrates a flowchart of the steps in the method for synthesizing the composite material according to one embodiment of this disclosure; Figure 2 illustrates the adsorption kinetics curves of Example 1 and Comparative Examples 1 to 3 as disclosed herein; Figure 3A illustrates the isothermal adsorption curves of Example 1 and Comparative Examples 1 to 3 as disclosed herein. Figure 3B illustrates the relationship between pH value and ethidium bromide concentration in Example 1 and Comparative Examples 1 to 3 of this disclosure; Figure 4 illustrates the bromide ion adsorption curves of Example 1 and Comparative Examples 1 to 4 as disclosed herein. Figure 5 illustrates the pH effect distribution of Example 1 and Comparative Examples 1 to 3 as disclosed herein. Figure 6A illustrates the X-ray diffraction data of Comparative Example 1 of the content disclosed herein; Figure 6B illustrates X-ray diffraction data of Embodiment 1 of this disclosure; Figure 7A illustrates the Fourier transform infrared spectral data of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 disclosed herein; Figure 7B shows a magnified view of the data in region 7B of Figure 7A; Figure 8 illustrates the differential thermal gravimetric data of Example 1 and Comparative Examples 1 to 4 of this disclosure. Figure 9A is a morphological diagram of one embodiment of the present disclosure; Figure 9B is another configuration diagram of Embodiment 1 of this disclosure; Figure 9C is a field emission scanning electron microscope image of Comparative Example 1 of the present disclosure; Figure 9D is another field emission scanning electron microscope image of Comparative Example 1 of this disclosure; Figure 9E is a field emission scanning electron microscope image of Embodiment 1 of this disclosure; and Figure 9F is another field emission scanning electron microscope image of Embodiment 1 of this disclosure. Implementation

[0018] The various embodiments of this disclosure will be discussed in more detail below. However, these embodiments can be applications of various inventive concepts and can be implemented in various different specific scopes. The specific embodiments are for illustrative purposes only and are not limited to the scope of the disclosure.

[0019] <Composite Materials>

[0020] One embodiment of this disclosure provides a composite material comprising graphene oxide and sodium alginate. The graphene oxide is in powder form. Due to its high specific surface area and numerous oxygen-containing functional groups, graphene oxide, as a functional material, can better form composite materials with other materials. When the total weight of the composite material is 100%, the weight proportion of graphene oxide is 40% to 60%. Furthermore, the weight proportion of graphene oxide can be 50%. Therefore, the composite material exhibits efficient adsorption of ethidium bromide and facilitates solid-liquid phase separation.

[0021] Sodium alginate has a degree of polymerization of 100 to 1000 and a viscosity of 10 to 1000 mPa·s (1% solution). Furthermore, Aladdin sodium alginate has a viscosity of 200 ± 20 mPa·s and a degree of polymerization of approximately 200. Therefore, sodium alginate possesses high viscosity, which, as a material carrier, effectively improves stability and uniformity, and significantly enhances mechanical strength, enabling the composite material to efficiently adsorb ethidium bromide and facilitate solid-liquid phase separation.

[0022] The composite material is granular, with an average particle size of 0.5 mm to 2.0 mm. Alternatively, the average particle size can be 1.0 mm to 1.5 mm. This enhances the adsorption capacity of the composite material and maintains a stable adsorption rate within the effective adsorption time.

[0023] <Synthesis Methods of Composite Materials>

[0024] Please refer to Figure 1, which illustrates a flowchart of the steps in a method 100 for synthesizing a composite material according to an embodiment of this disclosure. The method 100 includes steps 110 and 120. Step 110 involves adding graphene oxide to an aqueous solution of sodium alginate and stirring to dissolve it, forming a gel solution. The stirring time can be greater than or equal to 6 hours. Because the selected sodium alginate may have high viscosity, a container with a large bottom area can be used to ensure greater uniformity after stirring, and the stirring time can be adjusted to increase the contact area between graphene oxide and sodium alginate, making the gel solution easier to stir uniformly.

[0025] Step 120 involves contacting the gel solution with a coagulation bath, allowing the gel solution to react and solidify into multiple composite materials. The reaction time can be greater than or equal to 6 hours. The coagulation bath may contain calcium chloride, and the concentration of calcium chloride in the coagulation bath can be from 0.1% to 74.5%. Furthermore, the concentration of calcium chloride in the coagulation bath can be 0.1%. Specifically, a syringe can be used to first draw up the gel solution, and then drop the gel solution into the coagulation bath to facilitate contact between the gel solution and the coagulation bath. This results in composite materials with good mechanical properties, making them less prone to collapse.

[0026] Furthermore, after the composite material has solidified, it can be washed several times (e.g., 3 times) with deionized water, then soaked in deionized water for a period of time (e.g., more than or equal to 3 hours), and then washed several times again (e.g., 3 times) with deionized water.

[0027] Furthermore, after the composite material is cleaned, it can be placed in an oven for drying for 8 hours or more. It should be noted that the material proportions and dimensional properties of the synthesized composite material can be the same as or similar to those of the aforementioned composite material, and will not be repeated here.

[0028] <Method for adsorbing ethidium bromide>

[0029] One embodiment of this disclosure provides a method for adsorbing ethidium bromide, comprising placing a composite material into an aqueous solution of ethidium bromide, thereby allowing the composite material to adsorb ethidium bromide from the aqueous solution. It should be noted that the material proportions and dimensional properties of the composite material used above may be the same as or similar to those of the aforementioned composite material, and will not be repeated here.

[0030] The pH value of an aqueous solution of ethidium bromide can range from 2.0 to 11.0. Furthermore, the pH value of an aqueous solution of ethidium bromide can range from 6.0 to 8.0. Therefore, the composite material exhibits highly efficient adsorption of ethidium bromide, and due to its good mechanical strength, it is not easily collapsed.

[0031] <Example / Comparative Example>

[0032] Example 1: Graphene oxide was added to an aqueous solution of sodium alginate and stirred to dissolve, forming a gel solution. The gel solution was then brought into a coagulation bath, allowing it to react and solidify into multiple composite materials. The graphene oxide was in powder form, the sodium alginate had a degree of polymerization of approximately 200, the total weight of the composite materials was 100%, the weight percentage of graphene oxide was 50%, the composite materials were granular, and the average particle size of the composite materials was 0.5 mm to 2.0 mm.

[0033] Comparative Example 1: At a temperature below 20°C, graphite was continuously mixed in 98% sulfuric acid for 2 hours; at 35°C, 6 g of potassium permanganate was gradually added, and the mixture was stirred again for 1 hour; distilled water was added, followed by 5 ml of 30% hydrogen peroxide solution, and the mixture was stirred for 1 hour; 5% hydrochloric acid was added, and the mixture was stirred continuously; after 15 minutes, distilled water was added, and the pH value was adjusted to a neutral solution. The solution was then dried to obtain graphene oxide.

[0034] Comparative Example 2: Sodium alginate purchased from Aladdin (Shanghai, China).

[0035] Comparative Example 3: Graphite.

[0036] Comparative Example 4: Ethidium bromide (EtBr).

[0037] <Adsorption Kinetics Experiment>

[0038] Please refer to Figure 2, which shows the adsorption kinetics curves of Example 1 and Comparative Examples 1 to 3 of this disclosure.

[0039] Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were used as different adsorbents, with an initial EtBr concentration of 4 mmol / g. Samples were taken for analysis after 0.25, 0.5, 1, 2, 4, 8, 16, and 24 hours to determine the EtBr adsorption equilibrium time. The adsorption kinetic experimental data were fitted to a pseudo-second-order model using linear regression. The empirical equation is shown in equation (I): Formula (I); In equation (I), qe is the amount of adsorbent adsorbed at equilibrium (mg / g); k1 is the equilibrium rate constant of the pseudo-second-order model (g / mg h); qt is the amount of adsorbent adsorbed at different times (mg / g); and t is the adsorption time.

[0040] The adsorption kinetic curves obtained in this experiment are shown in Figure 2. With increasing time, the adsorption capacity of EtBr gradually increases and then stabilizes. In contrast, Example 1 showed the highest adsorption capacity of EtBr, while Comparative Example 3 showed no significant adsorption effect on EtBr. Furthermore, the pseudo-second-order adsorption kinetic model can fit the experimental data well.

[0041] The adsorption capacity of EtBr in Examples 1 and Comparative Example 2 remained stable for approximately 16 hours, while the adsorption capacity of EtBr in Comparative Example 1 remained stable for approximately 2 hours. After 16 hours, the adsorption process slowed down, mainly due to the reduction of surface adsorption active sites and the diffusion and transfer of ions within the composite micropores.

[0042] Example 1 exhibited an adsorption capacity of 1.2 mmol / g after 2 hours and reached 1.6 mmol / g after 4 hours, demonstrating superior performance in adsorbing EtBr. The excellent adsorption capacity of Example 1 is attributed to its ability to adsorb EtBr not only on the surface but also within its internal structure.

[0043] <Isothermal Adsorption Experiment>

[0044] Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were used as different adsorbents. 0.01 g of the adsorbent was added to 50 ml centrifuge tubes, with each tube containing 20 ml of liquid. Different initial EtBr concentrations were set: 50, 100, 200, 400, 800, 1000, 2000, 3000, 4000, 5000, 6000, 7000, and 8000 mg / L. Two sets of experiments were performed for each adsorbent.

[0045] The adsorption capacity (qe) of the adsorbent under equilibrium conditions can be calculated using the formula shown in equation (II): qe=(C0-Ce)v / m Equation (II); In equation (II), C0 is the initial concentration of EtBr in the solution (mmol / L); Ce is the concentration of EtBr at adsorption equilibrium (mmol / L); v is the volume of the EtBr solution (L); m is the mass of the adsorbent (g); and qe is the amount of adsorbent adsorbed at equilibrium (mmol / g).

[0046] The EtBr adsorption data were fitted to the Freundlich isotherm model and the Dubinin-Radushkevich (DR) model using linear regression. The Freundlich isotherm model is shown in equation (III): Equation (III); In equation (III), Kf is the adsorption equilibrium constant [(mmol / g) (L / mmol)1 / n], which represents the strength of the adsorption surface; 1 / n is the Freundlich constant (L / g) under the exponential factor. The DR model is shown in equation (IV): Formula (IV); In equation (IV), qs is the theoretical isotherm saturation capacity (mmol / g), kad is the isotherm constant (mol2 / (kJ2)), ε is the mean free energy, and DR model constant (kJ / mol).

[0047] Please refer to Figure 3A, which shows the isothermal adsorption curves of Example 1 and Comparative Examples 1 to 3 of this disclosure.

[0048] The Freundlich isotherm model and Langmuir model obtained in this experiment are shown in Figure 3A. The coefficient of determination (R²) calculated by the Freundlich isotherm model is 0.9696, and the R² calculated by the Langmuir model is 0.9627. The closer the R² is to 1, the better the model is at interpreting the experimental data.

[0049] Furthermore, calculations using the Freundlich isotherm model showed that the maximum adsorption capacity of EtBr in Example 1 was 2.97 mmol / g. It is worth noting that, compared to Comparative Examples 1, 2, and 3, the adsorption capacity of EtBr in Example 1 was increased by approximately 47%.

[0050] In detail, the results of the isothermal adsorption experiment in Example 1 fit the results calculated by the Freundlich isotherm model. Furthermore, the Freundlich isotherm model showed that the n-value for Example 1 was greater than 1, indicating favorable adsorption and the presence of a heterogeneous surface. This is because the surface of Example 1 has more highly electrostatic functional groups and hydroxyl adsorption sites, and multilayer adsorption can enhance the original monolayer adsorption.

[0051] Furthermore, the mean free energy of adsorption in Example 1 was calculated to be ε = 3.61 kJ / mol using the DR model, indicating that the adsorption process was spontaneous.

[0052] Please refer to Figure 3B, which shows the relationship between pH value and EtBr concentration for Example 1 and Comparative Examples 1 to 3 of this disclosure.

[0053] It is worth noting that Figure 3B mainly illustrates the pH changes of the solution after EtBr adsorption when Example 1 and Comparative Examples 1 to 3 use different adsorbents. It should be particularly noted that the surfaces of Example 1 and Comparative Example 2 contain a large number of hydroxide ions, the pKa2 value of EtBr is 2.43, and it carries a negative charge at pH 2.43.

[0054] When Example 1 and Comparative Examples 1 to 3 adsorbed EtBr solution, as the initial concentration of EtBr increased, the pH value decreased rapidly when the initial EtBr concentration was less than 1 mM, but the pH value changed only slightly when the initial concentration was greater than 1 mM.

[0055] When the initial concentration of EtBr adsorbed in Comparative Examples 2 and 3 was greater than 4 mM, the pH value of the solution decreased slightly. This may be due to the presence of a large number of free adsorption sites in the initial stage. At lower EtBr concentrations, the number of available adsorption sites is relatively high, so EtBr can easily find an available adsorption site on the surface of the adsorbent.

[0056] Therefore, it can be inferred that the concentration of EtBr molecules did not affect the entire adsorption process. This is because the electrostatic attraction between the hydroxide ions on the surface of graphene oxide and sodium alginate and the positively charged molecules within the EtBr molecules plays a dominant role in the adsorption mechanism.

[0057] <Adsorption Principle Experiment>

[0058] The experimental conditions in this experiment can be set as a flow rate of 0.6 mL / min, an electrolytic current of 50 mA, and the experimental acquisition time can be 10 minutes. The bromide ion mobile phase can be prepared from 2 liters of 0.2 mM sodium bicarbonate and 2 liters of 5 mM sodium carbonate. In addition, different bromide ion concentrations will be tested, which are respectively: 0.05, 0.1, 0.2, 0.4, 0.8, 1, 2, 3, 4, 5, 6, 7, 8 mmol / g.

[0059] The purpose of this experiment is to verify the theoretical understanding of the adsorption mechanism, and to understand the mode of chemical interaction between Example 1 and EtBr, wherein EtBr can be decomposed into bromide ions (Br-) and positively charged molecules (Et+), and the chemical reaction formula is shown in formula (V): Formula (V).

[0060] Please refer to Figure 4, which depicts the bromide ion adsorption curves of Example 1 of the present disclosure and Comparative Examples 1 to 4, wherein Comparative Example 4 is the reference value of this experiment.

[0061] After Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 adsorb EtBr respectively, the slopes of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 are all 0.999, and it is found that the Br- concentration in the solution does not affect the adsorption of EtBr by Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3. Therefore, this indicates that during the adsorption process, the Br- concentration in the solution does not affect the adsorption of EtBr, and only Et+ is removed from the solution to the solid surface, that is, cationic adsorption through electrostatic interaction plays the most important role.

[0062] <pH Effect Experiment>

[0063] Please refer to Figure 5, which depicts the pH effect scatter plots of Example 1 of the present disclosure and Comparative Examples 1 to 3.

[0064] In this experiment, the initial concentration of EtBr is set to 4 mmol / g, the adsorption time is 24 hours, the set pH value ranges from 2.0 to 11.0, and a set of experiments is carried out every 1 pH interval. The pH value is adjusted with 2 M sodium hydroxide or hydrochloric acid to simulate the adsorption interference in aqueous environments with different pH values.

[0065] As shown in Figure 5, compared with Comparative Examples 1 to 3, Example 1 has great advantages in water bodies with different pH environments. Especially when the pH is 5.0 to 11.0, the adsorption capacity of EtBr in Example 1 increases gradually with the gradual increase of the pH of the solution.

[0066] In detail, the point of zero charge (pHPZC) of graphene oxide is 4.1, indicating that when the pH is lower than 4.1, the surface of graphene oxide is mainly positively charged, and when the pH is higher than 4.1, it is mainly negatively charged. Therefore, when the pH is between 2.0 and 3.0, the positive charge on the surface of graphene oxide increases as the pH of the solution decreases. Compared with the case where the pH is 4.0, the decrease in pH weakens the electrostatic interaction between the hydroxide ions carried on the surface of graphene oxide and the positively charged Et+. Meanwhile, under low pH conditions, the increase in positive charge density, that is, the increase in surface hydrogen ion concentration, and the more complete protonation of amino groups increase electrostatic repulsion, which ultimately leads to a decrease in the adsorption capacity of EtBr. Secondly, when the pH is 5.0 to 11.0, with the gradual increase of the pH of the solution, the presence of hydroxide ions reduces the protonation of Et+ amino groups, which promotes the adsorption capacity of Et+ in Example 1 and Comparative Example 1.

[0067] <X-ray Diffraction Experiment>

[0068] In this experiment, Example 1 and Comparative Example 1 were tested, and the change in interlayer spacing when Example 1 and Comparative Example 1 adsorb different concentrations of EtBr was studied. For this purpose, different initial concentrations of EtBr were set, which were 0.05, 0.1, 0.2, 0.4, 0.8, 1, 2, 3, 4, 5, 6, 7, 8 mmol / g, respectively.

[0069] X-ray diffraction (XRD) analysis was performed with a PANalytical X'PERT PRO diffractometer (TEXAS Instrument, TEXAS, USA), equipped with Cu target radiation and an X 'Celerator detector, with a step size of 0.033° and a scanning speed of 5° / min. Measurements were performed in the 2θ range of 5° to 65° at 45 kV and 40 mA. Since physical grinding does not break chemical bonds, the sample can be carefully ground into powder for XRD analysis.

[0070] Please also refer to Figure 6A and Figure 6B. Figure 6A shows an X-ray diffraction data graph of Comparative Example 1 of the present disclosure, and Figure 6B shows an X-ray diffraction data graph of Example 1 of the present disclosure.

[0071] After EtBr was adsorbed in Examples 1 and Comparative Example 1, the 2θ of d001 gradually decreased as the initial EtBr concentration increased from 0.05 to 2.0 mM, indicating a decrease in crystallinity, while the full width at half maximum (FWHM) increased. Similarly, when the initial EtBr concentration was between 3.0 and 8.0 mM, the 2θ of d001 decreased with increasing initial EtBr concentration. The d001 in Example 1 expanded to 12.4 Å, and the d001 in Comparative Example 1 expanded to 12.6 Å, with the peak broadening representing a decrease in crystallinity.

[0072] Specifically, the d001 of Example 1 is 8.1 Å, and the d001 of Comparative Example 1 is 7.0 Å. The larger d001 spacing in Example 1 compared to Comparative Example 1 is due to the abundance of oxygen-containing functional groups in the sodium alginate of Example 1.

[0073] Furthermore, it can be observed that when the initial EtBr concentration is 0.05 to 1.0 mM, there is an ordered intercalation state and a narrow peak; when the initial EtBr concentration is 2.0 to 3.0 mM, the FWHM increases and there is a disordered intercalation state; when the initial EtBr concentration is 3.0 to 8.0 mM, the Et+ intercalation state changes in an ordered manner, and the peak gradually expands with the increase of the initial concentration until d001 in Example 1 expands to 12.4 Å. This indicates an expanded interlayer spacing, i.e., 12.4 Å minus 8.1 Å equals 4.3 Å. It is noteworthy that although the interlayer spacing is insufficient for Et+ to enter space in the vertical direction, it is possible to enter the interlayer spacing in the horizontal or inclined directions.

[0074] <Fourier Transform Infrared Spectroscopy Experiment>

[0075] Fourier transform infrared spectroscopy (FTIR) analysis was performed using a Nexus FTIR spectrometer (Thermo Nicolet, Waltham, USA) with potassium bromide particle suppression. The wavenumbers were acquired between 4000 and 400 cm⁻¹, with a resolution of 4 cm⁻¹ and an average of 256 scans. This experiment detected the stretching vibration frequencies of functional groups before and after EtBr adsorption in Examples 1, 1, 2, and 4.

[0076] Furthermore, for Example 1, the changes in the stretching vibration frequency of functional groups were studied when different initial EtBr concentrations were adsorbed, namely 0.4, 4.0 and 8.0 mM.

[0077] Please refer to Figures 7A and 7B simultaneously. Figure 7A shows the Fourier transform infrared spectral data of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 disclosed herein. Figure 7B shows a magnified view of the data in region 7B of Figure 7A.

[0078] The characteristic peaks of Comparative Example 1 are located at 3437, 1751, 1639, 1639 and 1074 cm-1, which are the stretching vibration bands of the hydroxyl (-OH) group, the stretching vibration band of the carboxyl group (C=O), the carbon-carbon double bond (C=C) stretching vibration band and the carbon-oxygen bond (CO) stretching vibration band, respectively.

[0079] In Comparative Example 2, the characteristic peak at 3700 to 3000 cm⁻¹ corresponds to the -OH stretching vibration band, the characteristic peaks at 1616 and 1433 cm⁻¹ correspond to the symmetric and asymmetric stretching vibrations of the carboxylate ion (COO⁻), and the characteristic peak at 1060 cm⁻¹ corresponds to the carbon-oxygen-carbon bridge (COC) stretching vibration band.

[0080] In Example 1, characteristic peaks located at 3386 and 1633 cm⁻¹ were observed, corresponding to the OH stretching vibration band and the C=C stretching vibration band, respectively. Furthermore, under different initial EtBr concentrations in Example 1, as the initial EtBr concentration increased, the positions of several characteristic peaks gradually became similar to those in Comparative Example 4, and the intensity of the characteristic peaks increased.

[0081] In detail, under the condition of an initial EtBr concentration of 8.0 mM, the characteristic peaks of Example 1 compared to Comparative Example 4 showed a significant change, with the characteristic peak of symmetric stretching nitrogen-hydrogen bond (NH) shifting from 3305 cm-1 to 3327 cm-1, and the characteristic peaks of asymmetric stretching NH and symmetric stretching carbon-hydrogen bond (CH) in aromatic compounds shifting significantly from 3176 cm-1 to 3190 cm-1.

[0082] The results show that CH3+, -NH2, and CH in EtBr participate in the interaction with the surface of Example 1. As can be seen in Figure 7B, after EtBr adsorption, the characteristic peak at 843 cm⁻¹ shifts to 822 cm⁻¹, and the characteristic peak at 1178 cm⁻¹ shifts to 1173 cm⁻¹. These results indicate that out-of-plane curved CH and methane (CH₂) participate in the interaction between Et⁺ and the surface of Example 1.

[0083] It is worth noting that the characteristic peak of 1578 cm⁻¹ initially appearing on Comparative Example 4 disappeared after EtBr adsorption in Example 1, indicating that Example 1 did not interact with the corresponding C=C, carbon-nitrogen double bond (C=N), and scissor vibration CH on the benzene ring. Therefore, in summary, Et⁺ cannot enter the interlayer spacing of Example 1 in a vertical or horizontal manner, but it can enter the space at an angle of at least 45°, allowing the functional groups to contact the surface of Example 1 and generate electrostatic interactions.

[0084] <Differential Thermal Gravimetric Experiment>

[0085] Thermogravimetric analysis (TGA) was performed in an N2 environment at a heating rate of 10°C / min using a TA-q500 heating device (TA Instruments, Delaware, USA). The differential thermogravimetric (DTG) curve was obtained by performing a first-order differential calculation on the TGA curve.

[0086] Please refer to Figure 8, which shows the differential thermal gravimetric data of Example 1 and Comparative Examples 1 to 4 as disclosed in this paper. The peak temperature of Comparative Example 1 is 256°C, while the peak temperature of Example 1 decreases to 223°C, indicating that the disintegration temperature of Example 1 is lower. However, when Example 1 and Comparative Example 1 adsorb EtBr from an 8 mM EtBr solution (Comparative Example 4, peak temperature 353°C), the peak temperature of Comparative Example 1 decreases to 194°C, while that of Example 1 is 238°C, indicating that the disintegration temperature of Example 1 is higher than that of Comparative Example 1. Furthermore, compared to Example 1, the peak temperature of Comparative Example 2 is 262°C, while Comparative Example 3 has no obvious peak temperature.

[0087] In detail, when the initial EtBr concentration was 8 mM, Example 1 showed two mass loss peaks at 203°C and 238°C, which correspond to the decomposition temperatures of adsorbed and inserted EtBr.

[0088] <Surface Analysis Experiment>

[0089] Please refer to Figures 9A and 9B simultaneously. Figure 9A is a diagram of one embodiment of the present disclosure, and Figure 9B is a diagram of another embodiment of the present disclosure.

[0090] Example 1 has a granular structure with a size of approximately 1.0 to 1.5 mm, and most of the graphene oxide is embedded in sodium alginate. After adsorbing EtBr, Example 1 expands to 2.0 mm.

[0091] Please refer to Figures 9C, 9D, 9E, and 9F simultaneously. Figure 9C is a field emission scanning electron microscope (FEM) image of Comparative Example 1 of this disclosure, and Figure 9D is another FEM image of Comparative Example 1 of this disclosure. Figure 9E is a FEM image of Embodiment 1 of this disclosure. Figure 9F is another FEM image of Embodiment 1 of this disclosure.

[0092] It is worth noting that in Example 1 and Comparative Example 1, the adsorption experiment was completed beforehand at an initial EtBr concentration of 8.0 mM, and then dried to prepare a field emission-scanning electron microscopy (FE-SEM) specimen. The surface structure was then measured using a JEOL JSM-7800F (OXFORD Instrument, Oxford, UK) FE-SEM.

[0093] Comparative Example 1 exhibited flocculation at 10 µm and numerous raised bands at 1 µm. In contrast, Example 1 had a very rough surface and many irregular pores. The rough surface of Example 1 could improve the hydrophobicity of the material, and the large number of pores could improve the adsorption performance of the material.

[0094] In summary, the composite materials, their synthesis methods, and EtBr adsorption methods disclosed in this paper effectively improve the stability and uniformity of the composite materials and significantly enhance their mechanical strength by selecting a specific degree of polymerization of sodium alginate. Furthermore, by selecting a specific proportion of graphene oxide, the composite materials exhibit efficient EtBr adsorption and easy solid-liquid phase separation.

[0095] Although the present disclosure has been presented above with reference to embodiments, it is not intended to limit the present disclosure. Anyone skilled in the art may make various modifications and alterations without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the claims defined in the appended patent application.

[0096] 100: Synthesis methods of composite materials 110, 120: Steps 7B: Area

Claims

1. A composite material comprising: graphene monoxide, wherein the graphene monoxide is in powder form; and sodium alginate, wherein the degree of polymerization of the sodium alginate is 200; wherein, The total weight of the composite material is 100%, and the weight proportion of graphene oxide is 50%; wherein the composite material is granular, and the average particle size of the composite material is 0.5 mm to 2.0 mm.

2. The composite material as claimed in claim 1, wherein the average particle size of the composite material is 1.0 mm to 1.5 mm.

3. A method for synthesizing a composite material, comprising: adding graphene monoxide to an aqueous solution of sodium alginate and stirring to dissolve it, thereby forming a gel solution; and contacting the gel solution with a coagulation bath, causing the gel solution to react with the coagulation bath and solidify into a plurality of composite materials; wherein, The graphene oxide is in powder form, and the sodium alginate has a degree of polymerization of 200; wherein, the total weight of the composite material is 100%, and the weight proportion of the graphene oxide is 50%; wherein, the composite material is in granular form, and the average particle size of the composite material is 0.5 mm to 2.0 mm.

4. The method for synthesizing the composite material as claimed in claim 3, wherein the coagulation bath contains calcium chloride, and the concentration of the calcium chloride in the coagulation bath is from 0.1% to 74.5%.

5. A method for synthesizing a composite material as claimed in claim 3, wherein the average particle size of the composite material is 1.0 mm to 1.5 mm.

6. The method for synthesizing the composite material as claimed in claim 3, wherein the stirring time for dissolving the graphene oxide in the sodium alginate aqueous solution is greater than or equal to 6 hours.

7. The method for synthesizing the composite material as claimed in claim 3, wherein the reaction time for the gel solution to react with and solidify in the coagulation bath is greater than or equal to 6 hours.

8. A method for adsorbing ethidium bromide, comprising: placing a composite material into an aqueous solution of ethidium bromide, thereby allowing the composite material to adsorb ethidium bromide from the aqueous solution; wherein, The composite material comprises graphene oxide and sodium alginate, wherein the graphene oxide is in powder form and the sodium alginate has a degree of polymerization of 200; wherein, the total weight of the composite material is 100%, and the weight proportion of graphene oxide is 50%; wherein, the composite material is in granular form, and the average particle size of the composite material is 0.5 mm to 2.0 mm.

9. The method for adsorbing ethidium bromide as described in claim 8, wherein the pH value of the aqueous ethidium bromide solution is from 2.0 to 11.

0.

10. The method for adsorbing ethidium bromide as described in claim 8, wherein the average particle size of the composite material is 1.0 mm to 1.5 mm.

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