Method for preparing oil tea shell extract liquid reduced graphene oxide material and application thereof

Abstract

A method for preparing an oil tea shell extract liquid reduced graphene oxide material and applications thereof, steps comprising: grinding washed oil tea shells into uniform powder by a high-speed blender, adding ultrapure water and heating in a water bath at 60-90 DEG C for 2-4 h, then filtering to obtain an oil tea shell extract liquid; ultrasonically dispersing graphene oxide in ultrapure water to obtain a uniform graphene oxide aqueous solution; mixing the prepared oil tea shell extract liquid and the graphene oxide aqueous solution uniformly at a ratio of 1:(2-8), heating in a water bath at 70-90 DEG C for 1-5 h, then filtering to obtain an oil tea shell extract liquid reduced graphene oxide, and placing in a freeze dryer to dry at -40 DEG C for 40-60 h; the scheme has the advantages of simple process, environmental friendliness, low cost, reaction at room temperature, and prevention of agglomeration of the adsorption material.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection, specifically relating to a method for preparing liquid-reduced graphene oxide material from camellia oleifera shell extract and its application. Background Technology

[0002] Of all pollutants in the aquatic environment, heavy metals, including copper, lead, cadmium, and chromium, deserve high attention because they are non-biodegradable and easily accumulate in organisms, even at trace concentrations.

[0003] Copper ions are essential nutrients for maintaining red blood cells, nerve cells, and the immune system in humans. However, according to standards set by the World Health Organization, when their concentration exceeds 2 mg / L, they become a contaminant in drinking water. Excessive exposure to copper through the human diet can lead to itching, dermatitis, vomiting, cramps, convulsions, and even death.

[0004] Currently, wastewater treatment methods mainly include chemical precipitation, membrane filtration, ion exchange, and adsorption. Adsorption is considered the most suitable and environmentally friendly method for removing heavy metal ions because it is simple to operate, low in cost, and, more importantly, the used adsorbent can be recycled, allowing for the recovery of heavy metals. Adsorbents typically possess advantages such as large specific surface area, high adsorption capacity, and high surface activity. Due to the technical and commercial feasibility and recyclability of nanomaterials, they are now widely used for pollutant adsorption. Graphene, a carbon-based nanomaterial with two-dimensional properties, has been discovered. Many studies have shown that graphene possesses a large specific surface area, stable chemical properties, and high negative charge density, exhibiting a strong affinity for heavy metal ions. Therefore, graphene is considered a promising adsorbent for removing heavy metal pollutants. However, as an absorbent, the π-π bond interactions between graphene sheets significantly reduce its surface area, making it prone to aggregation in aqueous solutions and limiting its adsorption capacity. Researchers have discovered that the oxygen-containing hydrophilic groups on graphene oxide (GO) provide greater stability by inhibiting the strong van der Waals forces between graphene sheets, thus improving their binding and uniform distribution. Therefore, by removing the oxygen-containing groups on GO, the inherent properties of graphene can be preserved while mitigating its drawbacks, and reduced graphene oxide (rGO) has been found to be a promising adsorbent. With scientific advancements, many reduction methods have emerged, such as adding reducing agents, high-temperature heat treatment, and electrochemical reduction, to obtain rGO. However, these methods all have drawbacks, including the high risk of using toxic and hazardous chemicals, the potential for secondary pollution, and the cumbersome and complex preparation processes, as well as high costs. Finding more environmentally friendly methods to reduce GO is crucial.

[0005] Currently, the green synthesis of rGO using plant extracts has proven to be eco-friendly and cost-effective. For example, Li et al. used eucalyptus leaf extract to reduce graphene oxide; Weng et al. studied the reduction of graphene oxide using green tea extract; and Mahmudzadeh et al. used nettle extract, all achieving good results. The most effective components in plant extracts fall into two categories: polyphenols and flavonoids. Based on this, some researchers have begun to focus on the efficient extraction of agricultural waste, which not only reduces the cost of reducing agents but also utilizes solid waste from agricultural activities, thus performing better in the waste-to-resource chain. For example, Gan et al. studied the application of sugarcane bagasse and its use in dye removal, demonstrating high efficiency in dye adsorption.

[0006] Camellia oleifera belongs to the Theaceae family. The seed coat accounts for nearly 60% of the total fruit weight and is rich in chemical substances such as phenols, terpenes, flavonoids, tea saponins, and polysaccharides. However, most of the seed coats are directly discarded or incinerated, causing both environmental pollution and a significant waste of resources. In recent years, various studies have been conducted on the comprehensive utilization of Camellia oleifera seed coats, revealing their excellent antioxidant properties.

[0007] Therefore, this study synthesized COS-rGO using camellia oleifera shell extract (COS) as a reducing agent and coating agent. COS-rGO can partially reduce GO to rGO, thus enabling the use of COS-rGO material to remove Cu(II) pollution from aqueous solutions. This demonstrates the application prospects of camellia oleifera shell-reduced graphene oxide, which is beneficial to environmental protection and the sustainable development of the economy and agriculture. Summary of the Invention

[0008] This application addresses the aforementioned shortcomings of existing technologies by providing a simple, environmentally friendly, low-cost method for preparing a graphene oxide adsorbent material from camellia oleifera shell extract that can react at room temperature and prevents adsorbent material aggregation. The adsorbent material obtained by this method has broad application prospects in the fields of agricultural waste resource utilization and heavy metal pollution removal in water. The aim is to solve the problems of low resource utilization rate of agricultural waste camellia oleifera shells and low adsorption capacity of graphene oxide for copper ions.

[0009] To solve the above-mentioned technical problems, the technical solution provided by this invention is: a simple and rapid method for preparing camellia oleifera shell extract to reduce graphene oxide material and the application of this material in the removal of copper ions in water, which is carried out according to the following steps:

[0010] (1) Preparation of Camellia oleifera shell extract: The washed Camellia oleifera shells are crushed into uniform powder by a high-speed mixer, ultrapure water is added and heated in a water bath at 60-90℃ for 2-4 hours, and then filtered to obtain Camellia oleifera shell extract (COS).

[0011] (2) Preparation of reduced graphene oxide from camellia oleifera shell extract: Graphene oxide was ultrasonically dispersed in ultrapure water to obtain a uniform aqueous solution of graphene oxide; the camellia oleifera shell extract and the aqueous solution of graphene oxide from step (1) were mixed evenly at a ratio of 1:(2-8), and the mixture was heated in a water bath at 70-90℃ for 1-3 hours. The mixture was filtered to obtain graphene oxide (COS-rGO) reduced from camellia oleifera shell extract. The filtered graphene oxide (COS-rGO) reduced from camellia oleifera shell extract was placed in a freeze dryer and dried at -40℃ for 40-60 hours for later use.

[0012] Furthermore, in step (1), the weight ratio of camellia seed shells to ultrapure water is 1:(10-50).

[0013] Furthermore, before filtration in step (1), the reaction solution heated in a water bath is centrifuged using a high-speed centrifuge.

[0014] Furthermore, the filtration in step (1) involves filtering the supernatant obtained after centrifugation through a 0.22 μm filter membrane.

[0015] Furthermore, the extract obtained in step (1) is refrigerated in a refrigerator for less than 48 hours.

[0016] Furthermore, in step (2), the weight ratio of graphene oxide to ultrapure water is 1:(1500-2500).

[0017] Furthermore, before filtration in step (2), the reaction solution heated in a water bath is centrifuged using a high-speed centrifuge.

[0018] Furthermore, the filtration in step (2) involves filtering the supernatant obtained after centrifugation through a 0.22 μm filter membrane.

[0019] This application also provides an application of the reduced graphene oxide material prepared by the above method using camellia oleifera shell extract in the adsorption of Cu(II).

[0020] Furthermore, the adsorption specifically involves: taking a Cu2SO4 solution with a concentration range of 1-50 mg / L, adding the prepared COS-rGO to the Cu2SO4 solution to carry out the adsorption reaction, taking out equal amounts of the reacted Cu2SO4 solution at different time points, diluting it, and placing it in an atomic absorption spectrometer to measure the concentration of Cu(II), and calculating the adsorption efficiency of COS-rGO for Cu(II).

[0021] Furthermore, the amount of COS-rGO used in the Cu2SO4 solution is 0.2-1.0 g / L.

[0022] Furthermore, the pH of the Cu2SO4 solution is 1-5.1.

[0023] Furthermore, the adsorption reaction temperature of the Cu2SO4 solution is 0℃-40℃.

[0024] Compared with the prior art, the advantages of this invention are:

[0025] 1. This invention uses water as the solvent throughout the entire process, avoiding secondary pollution and making it an environmentally friendly preparation method. Specifically, this application directly extracts graphene oxide-reducing material by crushing camellia oil shells and then using water; no special separation or purification treatment of the reducing substances is required. This method is simpler to operate, gentler in extraction, and lower in cost. It does not require the addition of any enzymes or other organic extraction reagents; only ultrapure water heated in a water bath at a certain temperature is needed. Furthermore, the water extract from crushed camellia oil shells does not require further purification or separation and can be directly used for the reduction reaction with graphene oxide. This mixed reduction method not only allows the reducing substances in the extract to react with the graphene oxide... Effective reduction of graphene allows non-reducing substances in the extract to support and coat the graphene oxide during the reduction process, thus preserving the excellent properties of graphene oxide, such as its dispersibility in water, without causing excessive agglomeration due to the removal of oxygen-containing groups, which would reduce its adsorption capacity for metal ions in water. In other words, the extraction method using water as a solvent in this application eliminates the need to separate and purify reducing and non-reducing substances, effectively simplifying the extraction process. More importantly, this method ensures effective dispersion of graphene oxide to prevent agglomeration and provides a larger contact area with metal ions during adsorption, thereby improving its adsorption capacity for metal ions.

[0026] 2. The process of this invention greatly improves the resource utilization of agricultural waste, helps reduce solid waste pollution and air pollution caused by farmers burning camellia shells, and promotes the planting of camellia, which is conducive to the sustainable development of economy and environment.

[0027] 3. The adsorbent material prepared by the method of the present invention is used for the adsorption of copper ions for the first time. It has a good effect on the removal of copper ions in water and can adsorb and remove copper ions at different temperatures and pH values.

[0028] 4. The reaction principle of this invention is as follows: Figure 1As shown, COS was first prepared using an environmentally friendly method, then mixed with GO solution. A Box-Behnken response surface design was used to optimize the preparation of COS-rGO material. Subsequently, the material was tested in Cu(II) removal experiments, and the experimental conditions were adjusted to show a trend towards better Cu(II) removal efficiency. Material property tests were also conducted to investigate the removal mechanism of Cu(II) adsorption, providing a basis for the preparation of a novel copper ion adsorption material.

[0029] 5. According to the preparation method of this application, LC-MS test results show that after reacting with graphene oxide, the reducing substances such as polyphenols and flavonoids (e.g., catechins, proanthocyanidins, puerarin glycosides, gallic acid, etc.) contained in the camellia oleifera shell extract disappear or their content decreases; XPS, XRD, EDS and other test results show that the oxygen content of the graphene oxide after reacting with the camellia oleifera shell extract decreases; in summary, it can be determined that the reducing substances in the camellia oleifera shell play a partial reducing role when reacting with graphene oxide.

[0030] 6. The preparation method of this application shows that the surface of graphene oxide after reaction with camellia seed shell extract appears rough by SEM; XPS fitting reveals changes in the content and types of oxygen-containing functional groups in the reacted graphene oxide; LC-MS test results show that some substances without reducing properties in the camellia seed shell extract disappear or decrease in content after reaction with graphene oxide. In summary, some substances in the camellia seed shell extract play a supporting and coating role in the partial reduction of graphene oxide, so that the good properties of graphene oxide, such as its dispersibility in water, are partially retained, and the material's application, such as its metal ion adsorption capacity in water, is not reduced due to excessive agglomeration caused by the removal of oxygen-containing functional groups.

[0031] 7. The adsorbent material obtained by the preparation method of this application can effectively improve the adsorption capacity of Cu(II). The maximum adsorption efficiency (removal efficiency) of the COS-rGO material of this application for Cu is 84.7%, which is much higher than the adsorption capacity of camellia shell powder (38.1%), and also higher than the maximum adsorption capacity of pure graphene oxide powder (68.2%). Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the reaction principle of the present invention.

[0033] Figure 2 The efficiency of copper(II) removal by camellia seed shell-reduced graphene oxide (COS-rGO) under different conditions.

[0034] Figure 3X-ray diffraction (XRD) patterns of graphene oxide (GO) and the camellia oleifera shell-reduced graphene oxide (COS-rGO) of this application.

[0035] Figure 4 (a) Scanning electron microscope (SEM) images of graphene oxide (GO) and (b) COS-rGO. (c, d) carbon spectra, (e) oxygen spectra, and (f) copper spectra of COS-rGO after Cu(II) adsorption.

[0036] Figure 5 (a) Transmission electron microscopy (TEM) images of graphene oxide (GO), (b) and (c) after Cu(II) adsorption on reduced graphene oxide (COS-rGO) from camellia oleifera shell.

[0037] Figure 6 Raman spectra of GO and COS-rGO.

[0038] Figure 7 (a) X-ray photoelectron spectroscopy (XPS) spectra of GO and COS-rGO before and after Cu(II) adsorption; (b) Cu 2p spectra of COS-rGO before and after Cu(II) adsorption; (c) O1s spectrum of GO; (d) C1s spectrum of GO; (e) C1s spectrum of COS-rGO; (f) C1s spectrum of COS-rGO after Cu(II) adsorption.

[0039] Figure 8 HP-LC chromatogram of components extracted from COS. Detailed Implementation

[0040] To make the technical solution of the present invention easier to understand, the following is a further detailed description of the present invention. The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0041] The reaction principle diagram of this application can be found in the attached diagram. Figure 1 This can demonstrate that substances with reducing properties in the extract can effectively reduce graphene oxide during the reduction process. It can also enable non-reducing substances in the extract to support and coat graphene oxide during the reduction process, ensuring effective dispersion of graphene oxide to prevent aggregation and providing a larger contact area with metal ions during the adsorption process, thereby improving its adsorption capacity for metal ions.

[0042] Example 1:

[0043] A simple and rapid method for preparing graphene oxide material reduced from camellia seed shell extract is carried out according to the following steps:

[0044] 1) Preparation of Camellia oleifera shell extract: The washed Camellia oleifera shells were crushed into a uniform powder using a high-speed mixer. 30g of Camellia oleifera shell powder was added to 1000mL of ultrapure water and heated in a water bath at 80℃ for 3h. Then, the mixture was filtered through a high-speed centrifuge at 5000r / min and a sand core funnel fitted with a 0.22μm filter membrane to obtain Camellia oleifera shell extract (COS). The extract was refrigerated for later use. To ensure the effective use of the Camellia oleifera shell extract, it should be prepared and used immediately, and the refrigerated storage time should not exceed 48h.

[0045] 2) Preparation of graphene oxide reduced from camellia oleifera shell extract: 1g of graphene oxide was ultrasonically dispersed (using conventional ultrasonic instruments, such as ultrasonic-microwave synergistic extractors) in 2000mL of ultrapure water to obtain a uniform GO aqueous solution; then, the camellia oleifera shell extract and the GO aqueous solution from step 1) were mixed uniformly at a mass ratio of 1:3.2 and heated in a water bath at 80℃ for 3h to react. The mixture was then filtered to obtain graphene oxide reduced from camellia oleifera shell extract (COS-rGO). The mixture was then filtered through a high-speed centrifuge at 5000r / min and a sand core funnel containing a 0.22μm filter membrane. The filtered COS-rGO was then placed in a freeze dryer and dried at -40℃ for 48h to obtain the dried adsorbent material COS-rGO.

[0046] 3) Adsorption of copper ions in water: Prepare a Cu2SO4 solution with a concentration range of 10 mg / L. Take 0.05 g of the above-prepared COS-rGO (reduced graphene oxide from camellia oleifera shell extract) and add it to the Cu2SO4 solution to react at room temperature. Take out equal amounts of the reacted Cu2SO4 solution at different time points, dilute it and put it into an atomic absorption spectrometer to measure the concentration of Cu(II) in order to detect the adsorption efficiency of COS-rGO for Cu(II).

[0047] The COS-rGO prepared in this application was compared with graphene oxide (GO) by... Figure 3 X-ray diffraction (XRD) patterns of graphene oxide (GO) and reduced graphene oxide (COS-rGO) from camellia oleifera shell; Figure 4 Scanning electron microscope (SEM) images of (a) graphene oxide (GO) and (b) COS-rGO. (c) Carbon spectrum, (e) oxygen spectrum and (f) copper spectrum of COS-rGO after Cu(II) adsorption; Figure 5 Transmission electron microscopy (TEM) images of (a) graphene oxide (GO), and (b) before and after Cu(II) adsorption on camellia seed shell reduced graphene oxide (COS-rGO); Figure 6 Raman spectra of GO and COS-rGO; Figure 7(a) X-ray photoelectron spectroscopy (XPS) spectra of GO and COS-rGO before and after Cu(II) adsorption; (b) Cu2p spectra of COS-rGO before and after Cu(II) adsorption; (c) O 1s spectrum of GO; (d) C1s spectrum of GO; (e) C1s spectrum of COS-rGO; (f) C1s spectrum of COS-rGO after Cu(II) adsorption; and Figure 8 HP-LC chromatogram of the components extracted from COS. The above detection results indicate that the adsorbent material prepared in this application is COS-rGO, which can effectively adsorb Cu(II).

[0048] Example 2

[0049] In this Example 2, the ratio of the camellia oleifera shell extract to the GO aqueous solution in step 2) is 1:2, and the other steps and parameters are the same as in Example 1.

[0050] Example 3

[0051] In this Example 3, the ratio of the camellia oleifera shell extract to the GO aqueous solution in step 2) is 1:8, and the other steps and parameters are the same as in Example 1.

[0052] Example 4

[0053] In this embodiment 4, the water bath heating temperature in step 2) is 70°C, and the other steps and parameters are the same as in embodiment 1.

[0054] Example 5

[0055] In this embodiment 5, the water bath heating temperature in step 2) is 90°C, and the other steps and parameters are the same as in embodiment 1.

[0056] Example 6

[0057] In this embodiment 6, the water bath heating time in step 2) is 1 hour, and the other steps and parameters are the same as in embodiment 1.

[0058] Example 7

[0059] In this embodiment 7, the water bath heating time in step 2) is 5 hours, and the other steps and parameters are the same as in embodiment 1.

[0060] The reduced graphene oxide material prepared by the present invention from camellia seed shell extract was applied to the adsorption of Cu(II) in aqueous solution. The specific process is as follows:

[0061] 1) To investigate the effect of COS-rGO dosage on Cu(II) removal efficiency, six Cu2SO4 solutions with a concentration of 10 mg / L, a volume of 100 mL, and a pH of 5.1 (original value without adjustment) were prepared. 0.02, 0.05, and 0.10 g of COS-rGO were added to each pair of solutions, respectively. The beakers containing the Cu2SO4 solutions were placed on a uniform constant-temperature stirring platform with a rotor speed of 200 rpm and a reaction temperature of 20℃; see Appendix for details. Figure 2 As shown in (a), the results indicate that the adsorption efficiency is relatively ideal when the dosage is 0.10 g.

[0062] 2) To investigate the effect of the initial concentration of Cu(II) solution on the removal efficiency, two groups of Cu2SO4 solutions with initial concentrations of 5, 10, 20, and 40 mg / L, each with a volume of 100 mL and a pH of 5.1 (unadjusted), were prepared. 0.05 g of COS-rGO was added to each of the two groups. The beakers containing the Cu2SO4 solutions were placed on a uniform constant-temperature stirring platform with a rotor speed of 200 rpm and a reaction temperature of 20℃. See Appendix for details. Figure 2 As shown in (b), the results indicate that the adsorption efficiency is relatively ideal when the initial concentration of Cu(II) solution is 5 mg / L.

[0063] 3) To investigate the effect of pH value of Cu(II) solution on removal efficiency, two groups of Cu2SO4 solutions with pH values ​​of 1, 3, 4, and 5.1, a concentration of 10 mg / L, and a volume of 100 mL were prepared. 0.05 g of COS-rGO was added to each group. The beakers containing the Cu2SO4 solutions were placed on a constant-temperature stirring platform of the same type, with a rotor speed of 200 rpm and a reaction temperature of 20℃; see Appendix for details. Figure 2 As shown in (c), the results indicate that the Cu(II) solution exhibits a relatively ideal adsorption efficiency when the pH value is 5.1.

[0064] 4) To investigate the effect of reaction temperature on the removal efficiency of Cu(II) solution, two groups of Cu2SO4 solutions were prepared at temperatures of 10℃, 20℃, 30℃, and 40℃, with a concentration of 10 mg / L, a volume of 100 mL, and a pH of 5.1 (unadjusted). 0.05 g of COS-rGO was added to each of the two groups. The beakers containing the Cu2SO4 solutions were placed on a constant-temperature stirring platform of the same model, with a rotor speed of 200 rpm; see Appendix for details. Figure 2 As shown in (d), the results indicate that the Cu(II) solution exhibits a relatively ideal adsorption efficiency when the reaction temperature is 40℃.

[0065] The adsorption efficiencies obtained from the above-mentioned different influencing factors can provide a reference for the ideal adjustment of the reduced graphene oxide material prepared by camellia shell extract for adsorbing copper(II) in the subsequent application, thereby providing a basis for those skilled in the art to quickly obtain an ideal adsorbent for copper(II).

[0066] The Cu₂SO₄ solution after the above reaction was collected at selected time intervals (5, 10, 30, 60, and 120 minutes) using a pipette and a syringe containing a 0.22 μm filter membrane. The Cu content was measured using atomic absorption spectrometry. The results are as follows: Figure 2 As shown: The results indicate that the maximum adsorption efficiency (removal efficiency) of the COS-rGO material of this application for Cu is 84.7%, which is much higher than the adsorption capacity of simple camellia seed shell powder (38.1%), and also higher than the maximum adsorption capacity of simple graphene oxide powder (68.2%); this fully demonstrates that the adsorbent material obtained by this method can significantly improve the adsorption efficiency for Cu.

[0067] This invention discloses a simple and rapid method for preparing graphene oxide material reduced from camellia oleifera shell extract and the application of an adsorption isotherm model of copper ion removal by this material in water. The method includes the following steps: 0.05g of the graphene oxide composite material prepared in Example 1 is added to Cu aqueous solutions (volume 100mL each) with Cu concentrations of 1mg / L, 5mg / L, 10mg / L, 20mg / L, 30mg / L, 40mg / L, and pH=5.1. The solutions are placed on a constant temperature stirring table at 200rpm and reacted at 10℃, 20℃, and 40℃ for 30min each. 1mL of each treated solution is filtered through a 0.22μm aqueous filter membrane, and the Cu content is measured by atomic absorption spectrometry. The Cu adsorption equilibrium concentration Ce (mg / L) and the material equilibrium adsorption capacity qe are calculated. The Cu adsorption isotherm results of the graphene oxide composite material reduced from camellia oleifera shell extract of this invention are shown in Table 1.

[0068] Table 1. Kinetic parameters of Cu(II) removal by COS-rGO

[0069]

[0070] It should be noted that in the table above:

[0071] The Langmuir adsorption isotherm model assumes that the adsorption process is a monolayer adsorption on the adsorbent surface, and the fitting equation is as follows:

[0072]

[0073] In Equation 1, q e (mg / g) represents the adsorption amount at adsorption equilibrium, Ce (mg / L) represents the concentration of residual pollutants in the solution at adsorption equilibrium, q m (mg / g) is the theoretical maximum adsorption capacity, while K L It is the Langmuir constant, R 2 The coefficient of determination, ranging from 0 to 1, indicates a better fit as it approaches 1.

[0074] The Freundlich adsorption isotherm model assumes the existence of energy-unbalanced adsorption sites where multilayer adsorption occurs, and the fitting equation is as follows:

[0075]

[0076] In Equation 2, q e (mg / g) represents the adsorption amount at adsorption equilibrium, C e (mg / L) represents the concentration of residual pollutants in the solution at adsorption equilibrium, K F is the Freundlich constant, and n is the binding energy constant, which reflects the adsorption capacity of the adsorbent for pollutants.

[0077] The Temkin adsorption isotherm model assumes that an increase in adsorption capacity leads to a linear decrease in the heat of adsorption, rather than a logarithmic decrease. The fitting formula is as follows:

[0078] q e =B(ln C) e )+B(ln A) (3)

[0079] In Equation 3, q e (mg / g) represents the adsorption amount at adsorption equilibrium, C e (mg / L) represents the concentration of residual pollutants in the solution at adsorption equilibrium, B is related to the heat of adsorption, and A (L / g) is the binding constant of the maximum binding energy at adsorption equilibrium.

[0080] The results show that the adsorption process of Cu by the camellia oleifera shell extract-reduced graphene oxide composite material of the present invention conforms to the Langmuir adsorption isotherm model.

[0081] This invention discloses a simple and rapid method for preparing graphene oxide material reduced from camellia oleifera shell extract and the application of an adsorption kinetic model for copper ion removal in water using this material. The method includes the following steps: preparing 100 ml of a 10 mg / L Cu solution in an Erlenmeyer flask with a pH of 5.1; weighing 0.05 g of the graphene oxide composite material prepared in Example 1 from camellia oleifera shell extract into the Cu solution; placing the flask on a 200 rpm constant temperature stirring table; reacting at 10℃, 20℃, and 40℃ respectively; taking 1 ml samples at 5 min, 10 min, 30 min, 60 min, and 120 min; filtering the samples through a 0.22 μm aqueous filter membrane; measuring the Cu content using atomic absorption spectrometry; and calculating the Cu adsorption amount. The kinetic results are shown in Table 2.

[0082] Table 2. Isothermal parameters for Cu(II) removal by COS-rGO.

[0083]

[0084] The adsorption of Cu(II) by COS-rGO was analyzed by fitting data using a kinetic model. The pseudo-first-order kinetic model assumes that the adsorption process is mainly controlled by the rate of the diffusion step, and the fitting formula is as follows:

[0085] ln(q e -q t )=lnq e -k1t (4)

[0086] The pseudo-second-order kinetic model assumes that the square of the number of unoccupied adsorption vacancies on the adsorbent surface determines the adsorption reaction rate. The fitting formula is as follows:

[0087]

[0088] In Equation 5, q t and q e , k1 and k2 are the adsorption amounts of Cu(II) by COS-rGO at time t and adsorption equilibrium, respectively, k1 is the pseudo-first-order adsorption rate constant, and k2 is the pseudo-second-order adsorption rate constant. The correlation coefficient R of the fitted curve is... 2 This serves as a standard for measuring the degree to which experimental data conforms to the kinetic model.

[0089] As shown in Table 2, by comparing R 2 The value indicates that the adsorption process of Cu on the camellia oleifera shell extract-reduced graphene oxide composite material of the present invention conforms to the second-order adsorption kinetic model.

[0090] This invention discloses a simple and rapid method for preparing graphene oxide material reduced from camellia oleifera shell extract and the application of an adsorption thermodynamic model for copper ion removal in water using this material. The method includes the following steps: preparing 100 ml of a 10 mg / L Cu solution in an Erlenmeyer flask with a pH of 5.1; weighing 0.05 g of the graphene oxide composite material reduced from camellia oleifera shell extract of Embodiment 1 into the Cu solution, placing it on a 200 rpm constant temperature stirring table, and reacting at 10℃, 20℃, and 40℃ respectively; taking 1 ml samples at 5 min, 10 min, 30 min, 60 min, and 120 min, filtering through a 0.22 μm aqueous filter membrane, measuring the Cu content using atomic absorption spectrometry, and calculating the Cu adsorption amount. The obtained thermodynamic results are shown in Table 3.

[0091] Table 3. Thermodynamic parameters of Cu(II) adsorption by COS-rGO.

[0092]

[0093] The results show that the adsorption process of Cu on the camellia oleifera shell extract-reduced graphene oxide composite material of the present invention is a spontaneous endothermic reaction.

[0094] Through the above embodiments and specific performance tests, it can be seen that the adsorbent material of this application, which uses camellia shell extract to reduce graphene oxide, can effectively adsorb copper. Some substances in the camellia shell extract play a supporting and coating role in the process of partial reduction of graphene oxide, so that the good properties of graphene oxide, such as its dispersibility in water, can be partially retained, and the material's application, such as its metal ion adsorption capacity in water, will not be reduced due to excessive compact aggregation caused by the removal of oxygen-containing groups.

[0095] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. The application of a camellia oleifera shell extract-reduced graphene oxide material in the adsorption of Cu(II), characterized in that: The steps for preparing the camellia oleifera shell extract-reduced graphene oxide material described in this application include: (1) Preparation of camellia shell extract: The washed camellia shells are crushed into uniform powder by a high-speed mixer, ultrapure water is added and heated in a water bath at 60-90℃ for 2-4 hours, and then filtered to obtain camellia shell extract; the weight ratio of camellia shells to ultrapure water in step (1) is 1:(10-50). (2) Preparation of graphene oxide reduced by camellia oleifera shell extract: Graphene oxide was ultrasonically dispersed in ultrapure water to obtain a uniform aqueous solution of graphene oxide; the camellia oleifera shell extract and the aqueous solution of graphene oxide in step (1) were mixed evenly at a mass ratio of 1:(2-8), and the mixture was heated in a water bath at 70-90℃ for 1-5h. Then, the mixture was filtered to obtain graphene oxide reduced by camellia oleifera shell extract. The filtered graphene oxide reduced by camellia oleifera shell extract was placed in a freeze dryer and dried at -40℃ for 40-60h for later use.

2. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 1 in the adsorption of Cu(II), characterized in that: Before filtration in step (1), the reaction solution heated in a water bath is centrifuged using a high-speed centrifuge.

3. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 2 in the adsorption of Cu(II), characterized in that: The filtration in step (1) involves filtering the supernatant obtained after centrifugation through a 0.22 μm filter membrane.

4. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 1 in the adsorption of Cu(II), characterized in that: The extract obtained in step (1) is placed in a refrigerator for less than 48 hours.

5. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 1 in the adsorption of Cu(II), characterized in that: In step (2), the weight ratio of graphene oxide to ultrapure water is 1:(1500-2500).

6. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 1 in the adsorption of Cu(II), characterized in that: Before filtration in step (2), the reaction solution heated in a water bath is centrifuged using a high-speed centrifuge; the filtration in step (2) involves filtering the supernatant obtained after centrifugation through a 0.22 μm filter membrane.

7. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 1 in the adsorption of Cu(II), characterized in that: The adsorption process specifically involves: taking a CuSO4 solution with a concentration range of 1-50 mg / L, adding the prepared camellia seed shell extract reduced graphene oxide material to the CuSO4 solution for adsorption reaction, taking out equal amounts of the reacted CuSO4 solution at different time points, diluting it, and placing it in an atomic absorption spectrometer to measure the concentration of Cu(II), thereby detecting the adsorption efficiency of the camellia seed shell extract reduced graphene oxide material for Cu(II).

8. The application of the camellia oleifera shell extract-reduced graphene oxide material according to claim 7 in the adsorption of Cu(II), characterized in that: The amount of the reduced graphene oxide material in the camellia oleifera shell extract in the CuSO4 solution is 0.2-1.0 g / L; the pH of the CuSO4 solution is 1-5.1; and the adsorption reaction temperature is 0℃-40℃.

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