Preparation method and application of corncob / cyclodextrin / montmorillonite composite adsorption material

Abstract

The application discloses a preparation method and application of a corncob / cyclodextrin / montmorillonite composite adsorbing material and belongs to the technical field of composite functional material preparation. The preparation method is as follows: corncob powder is washed with distilled water, boiled to remove natural pigment, soaked in deionized water, washed and dried for standby; under acidic conditions, montmorillonite is added into an ethanol / water solution containing a silane coupling agent to prepare silanized montmorillonite; the pretreated corncob powder and beta-cyclodextrin are added into deionized water, and an NaOH aqueous solution is added for alkalization; the obtained solution after alkalization is added with the silanized montmorillonite, stirred for 30 min, heated and slowly added with epichlorohydrin dropwise into the reaction solution, continuously reacted after the addition is completed, washed and dried after the reaction is completed, so as to obtain the corncob / cyclodextrin / montmorillonite composite adsorbing material. The preparation process is easy to operate and low in cost, the material has good adsorbing effect, and the industrialized production can be easily realized and the practical application range can be expanded.

Description

Technical Field

[0001] This invention belongs to the field of composite functional material preparation technology, specifically relating to a method for preparing and applying a corn cob / cyclodextrin / montmorillonite composite adsorbent material. Background Technology

[0002] With the continuous development of industries such as dyeing, textiles, printing, leather, cosmetics, and food, a large amount of organic dye wastewater is generated every year, posing a serious threat to water resources and human health. Most organic dyes contain complex aromatic ring structures, are chemically stable and difficult to degrade, and many are also biotoxic, making them considered persistent pollutants. Therefore, a large amount of research has been dedicated to the removal of organic dyes from wastewater. Currently, the main methods for dye removal include advanced oxidation processes, electrochemical treatment, adsorption, biological treatment, and membrane filtration. Among these, adsorption is favored due to its simplicity, ease of operation, rapid pollutant removal, and the ability to reuse adsorbents multiple times.

[0003] Corn is one of the main crops in my country. The corn cob is the cob of the corn after the kernels have been removed. It contains a large amount of cellulose, hemicellulose and lignin, and is tough, uniform in structure and has strong water absorption, making it a good adsorbent material. However, a large amount of corn cobs are discarded or burned every year, resulting in a great waste. Montmorillonite is a layered hydrated aluminosilicate natural mineral with abundant reserves and low price. It has adsorption capacity and is used in the field of sewage treatment. However, the affinity of natural montmorillonite for organic pollutants is not very strong, and it cannot achieve a good effect in removing dye molecules from wastewater (Wang Liyan, Yang Chao, Li Huan, et al. Research progress of organic modified montmorillonite for sewage treatment, Functional Materials, 2022, 12(53):12065-12072.). At present, the main methods of montmorillonite modification are: cation exchange method, non-covalent bond interaction of anions, and reaction with -OH on the surface of montmorillonite. Commonly used cationic surfactants include organic quaternary ammonium salts, organic quaternary phosphonium salts, and organic imidazole salts, while anionic surfactants mainly include sodium dodecyl sulfate. These surfactants introduce organic groups through metal ion exchange, ion dipole interactions, or hydrogen bonding between montmorillonite layers, thereby widening the interlayer spacing and improving the oleophilicity and hydrophobicity of montmorillonite. Furthermore, based on ion exchange or coupling agent modification, modified montmorillonite can be further melt-mixed or in-situ polymerized with polymer monomers to obtain composite materials. While these modification methods can endow montmorillonite with new adsorption properties, the processes are often difficult to control, the preparation processes are complex, and the production energy consumption is high, making industrial-scale production challenging.

[0004] Adsorbents are the "heart" of adsorption, playing a crucial role in the adsorption process of dyes. The search for economical, environmentally friendly, and effective adsorbents has always been a key research direction. Developing environmentally friendly, low-cost, and recyclable organic-modified montmorillonite composite materials is a major research focus in this field. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing a corn cob / cyclodextrin / montmorillonite ternary composite adsorbent material. The method is characterized by the use of green and environmentally friendly raw materials that are inexpensive, and the preparation process is simple, easy to operate, and has mild reaction conditions. The prepared product combines the characteristics of corn cob, cyclodextrin, and montmorillonite, and its adsorption performance is greatly improved.

[0006] This invention first reacts the hydroxyl groups on montmorillonite with the silane coupling agent KH-560 to obtain silanized montmorillonite containing terminal epoxy groups. Then, epichlorohydrin is used under alkaline conditions to carry out a ring-opening polymerization reaction with decolorized corn cob powder and the hydroxyl groups on cyclodextrin to obtain a layered corn cob / cyclodextrin / montmorillonite composite adsorbent material with a rough and porous surface.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing a corn cob / cyclodextrin / montmorillonite composite adsorbent material specifically includes the following steps:

[0009] (1) Rinse the corn cob powder with distilled water, boil it to remove its natural pigments, soak it in deionized water and wash it, and then dry it at 80°C for later use.

[0010] (2) Under acidic conditions, montmorillonite was added to an ethanol / water solution containing silane coupling agent KH-560 and refluxed for 24 hours. The resulting product was washed repeatedly with anhydrous ethanol to obtain silanized montmorillonite.

[0011] (3) Add the pretreated corn cob powder and β-cyclodextrin to deionized water and add NaOH aqueous solution for alkalization to change the -OH in the raw material to -ONa;

[0012] (4) Add silanized montmorillonite to the solution obtained in step (3), stir for 30 min, raise the temperature and slowly add epichlorohydrin (1 drop / second) to the reaction solution. After the addition is complete, continue the reaction for a period of time, cool to room temperature, wash the product repeatedly with anhydrous ethanol and deionized water, and dry it under vacuum at 70℃ to obtain corn cob / cyclodextrin / montmorillonite composite adsorbent material.

[0013] Preferably, the corn cob powder used in step (1) is 35 mesh, the boiling time is 3 hours, and the soaking time is 24 hours.

[0014] Preferably, in step (2), the volume ratio of ethanol to water is 1:1 to 12:1; the acidic condition is that the pH is adjusted to 4 with acetic acid; and the mass ratio of montmorillonite to silane coupling agent KH-560 is 10:7.

[0015] Preferably, the mass ratio of corn cob powder to β-cyclodextrin in step (3) is 1:0.3 to 1:2.

[0016] Preferably, the amount of NaOH aqueous solution used in step (3) is 25~75 mL / g corn cob powder, and the mass concentration is 5%~25%.

[0017] Preferably, the alkalization time in step (3) is 12 hours.

[0018] Preferably, the mass ratio of silanized montmorillonite to corn cob powder added in step (4) is 0.3:1 to 5:1.

[0019] Preferably, the amount of epichlorohydrin in step (4) is 3~25 mL / g corn cob powder.

[0020] Preferably, the reaction temperature in step (4) is 20~80℃.

[0021] Preferably, the reaction time in step (4) is 4 to 48 hours.

[0022] This invention provides a corn cob / cyclodextrin / montmorillonite composite adsorbent material prepared by the above method, which can be used for the adsorption of organic dye molecules.

[0023] Furthermore, the organic dye molecule used is malachite green (MG).

[0024] The specific application process is as follows: Weigh 10 mg of the corn cob / cyclodextrin / montmorillonite composite material and add it to 20 mL of malachite green dye solution. Adsorption is carried out at 20~60℃ with magnetic stirring at 800 rpm for 1~360 min. The mass concentration of the malachite green dye solution is 30~400 mg / L and the pH value is 3~13.

[0025] The corn cob / cyclodextrin / montmorillonite composite material provided by this invention exhibits an adsorption equilibrium time of 90 min for malachite green, a maximum adsorption capacity of 518.79 mg / g, and a removal rate of 99.77%. Alkalinity is more favorable for the adsorption of malachite green by this material because in an alkaline environment, -OH groups deprotonate to -O groups. -This increases the electrostatic interaction with malachite green. The adsorption capacity of malachite green reaches its maximum at 45℃. This is because the increased temperature accelerates the irregular movement of dye molecules and the collisions and interactions between them and adsorbent molecules. However, at excessively high temperatures, the interaction between dye molecules and adsorbent is weakened, thus reducing the adsorption effect.

[0026] The beneficial effects of this invention are as follows:

[0027] (1) The preparation method of corn cob / cyclodextrin / montmorillonite composite adsorbent provided by the present invention involves reacting corn cob, β-cyclodextrin and montmorillonite, which are inexpensive and readily available, with corn cob and cyclodextrin grafted onto the surface and interlayer of montmorillonite through epichlorohydrin crosslinking reaction, thereby improving the oleophilicity of the interlayer and surface of montmorillonite and increasing the oleophilicity of the montmorillonite interlayer, which can better act on organic molecules; on the other hand, the resulting composite not only contains a large number of hydroxyl groups on the surface, but also has the "hydrophobic inside and hydrophilic outside" structural unit of cyclodextrin, which can form non-covalent forces such as hydrogen bonds, electrostatics and inclusion effects with a variety of organic pollutants.

[0028] (2) The preparation method of corn cob / cyclodextrin / montmorillonite composite adsorbent material provided by the present invention effectively overcomes the defects of poor adsorption of organic pollutants by natural corn cob and montmorillonite, and has good adsorption performance when used for adsorption treatment of dye molecules.

[0029] (3) The synthesis process of the present invention is simple and easy to operate, with low cost, good adsorption effect, and simple post-processing. It is easy to realize industrial production and expand its practical application scope. Attached Figure Description

[0030] Figure 1 The infrared spectrum is shown for the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of this invention.

[0031] Figure 2 This is a SEM image of the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of the present invention.

[0032] Figure 3 The image shows the TG curve of the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of this invention.

[0033] Figure 4 This is the standard working curve for malachite green.

[0034] Figure 5 This is a comparison chart showing the adsorption of malachite green by the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of the present invention and the original corn cob powder at different times.

[0035] Figure 6The image shows a comparison of the adsorption of malachite green by the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of this invention and the original corn cob powder at different pH values.

[0036] Figure 7 The graph shows the adsorption data of 260 mg / L malachite green by the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of the present invention at different times.

[0037] Figure 8 The graph shows the adsorption data of 260 mg / L malachite green by the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of the present invention at different pH values.

[0038] Figure 9 The graph shows the adsorption data of 260 mg / L malachite green by the corn cob / cyclodextrin / montmorillonite composite material prepared in Example 6 of the present invention at different temperatures. Detailed Implementation

[0039] The present invention will be further described below with reference to the embodiments and accompanying drawings. However, the scope of protection of the present invention is not limited to these embodiments. Any invention that is similar in concept to the present invention but with only simple modifications falls within the scope of protection of the present invention. Example 1

[0040] Pretreatment of corn cobs: Take 20g of corn cob powder (35 mesh) into a 1000mL beaker, wash it repeatedly with deionized water, then put the washed corn cob powder into a 250mL three-necked flask, add 150mL of deionized water and boil for 3 hours, then continue to soak for 24 hours, filter and wash with deionized water, and dry at 80℃ for later use. Example 2

[0041] Organic modification of montmorillonite: In a round-bottom flask, 7g of silane coupling agent KH560 was added to a 100mL ethanol / distilled water (9 / 1 volume ratio) mixed solution, and an appropriate amount of acetic acid was added to adjust the pH of the solution to 4. After stirring for 4 hours, 10g of montmorillonite was added to the hydrolyzed solution, and the mixture was refluxed at 70℃ for 24 hours. Finally, the treated montmorillonite product was diluted with a large amount of anhydrous ethanol, washed, filtered, and then vacuum dried at 90℃ for 24 hours to obtain silanized montmorillonite. Example 3

[0042] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 0.3g of β-cyclodextrin into a 100mL round-bottom flask, then add 25mL of 5% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0043] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 0.3 g of silanized montmorillonite was added to the solution obtained in step (1). After stirring at room temperature for 30 min, the temperature was controlled at 20 °C, and 3 mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 20 °C for 48 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70 °C to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material. Example 4

[0044] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 0.5g of β-cyclodextrin into a 100mL round-bottom flask, then add 30mL of 10% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0045] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 0.8 g of silanized montmorillonite was added to the solution obtained in step (1). After stirring at room temperature for 30 min, the temperature was controlled at 30 °C, and 4 mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 30 °C for 40 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70 °C to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material. Example 5

[0046] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 1g of β-cyclodextrin into a 100mL round-bottom flask, then add 40mL of 15% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0047] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 1.3g of silanized montmorillonite was added to the solution obtained in step (1), and the mixture was stirred at room temperature for 30min. The temperature was then controlled at 40℃, and 5mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 40℃ for 36h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material. Example 6

[0048] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 1.2g of β-cyclodextrin into a 100mL round-bottom flask, then add 50mL of 20% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0049] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 2g of silanized montmorillonite was added to the solution obtained in step (1), and the mixture was stirred at room temperature for 30min. Then, the temperature was slowly raised to 50℃, and 6mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 50℃ for 30h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material.

[0050] Figure 1 This is the infrared spectrum of the corn cob / cyclodextrin / montmorillonite composite material from Example 6. As can be seen from the image, at 3613.95 cm⁻¹... -1 The absorption peak at 3430.74 cm⁻¹ corresponds to the -OH group of the Al-O structure in the montmorillonite lamellae. -1 The absorption peak for -OH is at 2917.77 cm⁻¹. -1 The absorption peaks at 1635.34 and 1594.84 cm⁻¹ represent the CH content in -CH₂. -1 The absorption peak at 1394.28 cm⁻¹ is the C=C absorption peak on the aromatic ring. -1 The absorption peak for COC is 1024.02 cm⁻¹. -1 It is the absorption peak of Si-O-Si, 514.90 cm⁻¹. -1 468.62cm -1 The presence of a unique vibrational absorption peak in Si-O-Al indicates the successful preparation of the corn cob / cyclodextrin / montmorillonite composite material.

[0051] Figure 2 This is a SEM image of the corn cob / cyclodextrin / montmorillonite composite material in Example 6. As can be seen from the image, the surface of the composite material is rough and uneven, and it has a layered porous structure, which is conducive to the adsorption of dye molecules.

[0052] Figure 3The image shows the TG curve of the corn cob / cyclodextrin / montmorillonite composite material in Example 6. The curve shows that: at 0-100℃, the main stage is the evaporation of water molecules; at around 100-300℃, the main stage is the decomposition of a large number of hydroxyl groups in the compound; at 300-400℃, the curve drops sharply, mainly due to the destruction and decomposition of the macromolecular structure in the composite; above 400℃, the mass loss is slow, and at 800℃, the mass of the corn cob / cyclodextrin / montmorillonite composite material is still 33.92%, indicating that the corn cob / cyclodextrin / montmorillonite composite material prepared in this invention has good thermal stability. Example 7

[0053] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 1.2g of β-cyclodextrin into a 100mL round-bottom flask, then add 50mL of 25% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0054] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 2g of silanized montmorillonite was added to the solution obtained in step (1), and the mixture was stirred at room temperature for 30min. Then, the temperature was slowly raised to 50℃, and 12mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 50℃ for 30h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material. Example 8

[0055] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 1.5g of β-cyclodextrin into a 100mL round-bottom flask, then add 60mL of 20% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0056] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 3g of silanized montmorillonite was added to the solution obtained in step (1). After stirring at room temperature for 30min, the temperature was slowly raised to 60℃, and 15mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 60℃ for 20h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material. Example 9

[0057] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 2g of β-cyclodextrin into a 100mL round-bottom flask, then add 70mL of 20% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0058] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 4g of silanized montmorillonite was added to the solution obtained in step (1). After stirring at room temperature for 30min, the temperature was slowly raised to 70℃, and 18mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 70℃ for 10h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material.

[0059] Example 10:

[0060] (1) Alkalization of corn cob powder and cyclodextrin: Weigh 1g of pretreated corn cob powder and 2g of β-cyclodextrin into a 100mL round-bottom flask, then add 75mL of 25% NaOH aqueous solution to the flask and stir at room temperature for 12h to obtain an alkalized corn cob powder and cyclodextrin mixed solution.

[0061] (2) Preparation of corn cob / cyclodextrin / montmorillonite composite material: 5g of silanized montmorillonite was added to the solution obtained in step (1). After stirring at room temperature for 30min, the temperature was slowly raised to 80℃, and 21mL of epichlorohydrin was slowly added dropwise to the reaction solution. After the addition was completed, the reaction was continued at 80℃ for 4h. After the reaction was completed, the reaction solution was cooled to room temperature, and the product was washed repeatedly with anhydrous ethanol and deionized water. The product was then dried under vacuum at 70℃ to obtain the corn cob / cyclodextrin / montmorillonite composite adsorbent material.

[0062] Example 11: Adsorption Application

[0063] This embodiment takes the corn cob / cyclodextrin / montmorillonite composite adsorbent material prepared in Example 6 as an example, and uses malachite green as the adsorbed dye to provide the adsorption application effect of the corn cob / cyclodextrin / montmorillonite composite adsorbent material on it. Based on the comparison with the adsorption effect of corn cob powder raw material, the adsorption effect of high concentration of malachite green was studied.

[0064] (1) Standard working curve of malachite green

[0065] Weigh 100 mg of malachite green dye into a 100 mL volumetric flask, add water to the 100 mL mark to prepare a 1000 mg / L solution. Prepare malachite green solutions with concentration gradients of 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, and 70 mg / L by pipetting different volumes of this solution into 10 mL volumetric flasks. Measure the absorbance of the solutions at an absorption wavelength of 619 nm. Plot a concentration-absorbance standard curve based on the absorbance A corresponding to concentration C: A = 0.0191C + 0.0024(R²). 2 =0.9990), see Figure 4 .

[0066] (2) Adsorption performance comparison: The adsorption effect of the corn cob / cyclodextrin / montmorillonite composite material was compared with that of the original corn cob powder.

[0067] Effect of adsorption time on adsorption capacity: 10 mg of raw corn cob powder and corn cob / cyclodextrin / montmorillonite composite material were weighed and added to 20 mL of malachite green dye solution (30 mg / L). Adsorption was carried out by magnetic stirring at room temperature and 800 rpm. Samples were taken at regular intervals, and the supernatant was collected after centrifugation. The absorbance A at the maximum absorption wavelength was measured by UV spectrophotometer. The dye concentration was calculated based on the standard working curve of malachite green, and then the adsorption capacity of malachite green at different times was calculated. The experimental results are shown in [Figure number missing]. Figure 5 As shown in the figure, the maximum adsorption capacity of the corn cob / cyclodextrin / montmorillonite composite material for malachite green is 58.36 mg / g, with a removal rate of 97.27%.

[0068] Effect of solution pH on adsorption capacity: 10 mg of raw corn cob powder and corn cob / cyclodextrin / montmorillonite composite material were weighed and added to 20 mL of malachite green dye solution (30 mg / L) at pH values ​​of 3, 5, 7, 9, 11, and 13, respectively. The solutions were magnetically stirred at 800 rpm for 60 min at room temperature. After adsorption, the supernatant was collected by high-speed centrifugation in centrifuge tubes, and its absorbance was measured using a UV-Vis spectrophotometer. The concentration corresponding to the absorbance value was calculated using a standard curve. Based on the calculated adsorption capacity of malachite green at different pH values, the relationship curve between adsorption capacity and pH was plotted. Figure 6 The figure shows that alkaline conditions are more conducive to the adsorption of malachite green by the corn cob / cyclodextrin / montmorillonite composite material and the original corn cob powder. This is because the adsorbent contains more -O atoms in an alkaline environment. -The increased electrostatic interaction with malachite green, combined with the hydrophobic multilayer structure of montmorillonite and the cavity inclusion effect of cyclodextrin in the corn cob / cyclodextrin / montmorillonite composite material, results in a significantly better adsorption effect of the composite material prepared by this invention compared to the original corn cob powder.

[0069] (3) Adsorption studies

[0070] The adsorption effect of corn cob / cyclodextrin / montmorillonite composite material on high concentration dyes:

[0071] Effect of adsorption time on adsorption capacity: 10 mg of the corn cob / cyclodextrin / montmorillonite composite material was weighed and added to 20 mL of malachite green dye solution with a mass concentration of 260 mg / L. Adsorption was carried out by magnetic stirring at 800 rpm. Samples were taken every 30 min, and after centrifugation, the supernatant was collected. The absorbance A at the maximum absorption wavelength was measured by UV spectrophotometer. The dye concentration was calculated based on the standard working curve of malachite green, and then the adsorption capacity of malachite green at different times was calculated. The experimental results are shown in [Figure number missing]. Figure 7 As shown in the figure, the adsorption equilibrium time of the corn cob / cyclodextrin / montmorillonite composite material for malachite green was 90 min, the maximum adsorption capacity was 518.79 mg / g, and the removal rate was 99.77%.

[0072] Effect of solution pH on adsorption capacity: 10 mg of the corn cob / cyclodextrin / montmorillonite composite material was weighed and added to 20 mL (260 mg / L) malachite green dye solutions at pH values ​​of 3, 5, 7, 9, 11, and 13, respectively. The solutions were stirred at room temperature for 90 min. After adsorption, the supernatant was collected by high-speed centrifugation, and its absorbance was measured using a UV-Vis spectrophotometer. The concentration corresponding to the absorbance value was calculated using a standard curve. Based on the calculated malachite green adsorption capacity at different pH values, a curve showing the relationship between adsorption capacity and pH was plotted. Figure 8 As shown in the figure, the adsorption capacity of malachite green by the corn cob / cyclodextrin / montmorillonite composite material increases with increasing pH value. This is because -OH is deprotonated to -O in an alkaline environment. - This increases the electrostatic interaction with malachite green.

[0073] Effect of adsorption temperature on adsorption capacity: 10 mg of the corn cob / cyclodextrin / montmorillonite composite material was weighed and added to 20 mL (260 mg / L) of malachite green dye solution at temperatures of 20℃, 30℃, 35℃, 40℃, 45℃, and 50℃, respectively. The solutions were stirred at room temperature for 60 min. After adsorption, the supernatant was collected by high-speed centrifugation in centrifuge tubes, and its absorbance was measured using a UV-Vis spectrophotometer. The concentration corresponding to the absorbance value was calculated using a standard curve. Based on the calculated adsorption capacity of malachite green at different temperatures, the relationship curve between adsorption capacity and temperature was plotted, as shown in [reference needed]. Figure 9 As shown in the figure, the corn cob / cyclodextrin / montmorillonite composite material achieves its maximum adsorption capacity for malachite green at 45℃. This is because at higher temperatures, the irregular movement of dye molecules accelerates, thereby enhancing the collisions and interactions between dye and adsorbent molecules. However, at excessively high temperatures, the interaction forces between dye molecules and the adsorbent are weakened, leading to a decrease in adsorption efficiency.

Claims

1. A method for preparing a corn cob / cyclodextrin / montmorillonite composite adsorbent, characterized in that... Includes the following steps: (1) Rinse the corn cob powder with distilled water, boil it to remove its natural pigments, soak it in deionized water and wash it, and then dry it at 80°C for later use. (2) Under acidic conditions, montmorillonite was added to an ethanol / water solution containing a silane coupling agent and refluxed for 24 hours. The resulting product was washed repeatedly with anhydrous ethanol to obtain silanized montmorillonite. (3) Add the pretreated corn cob powder and β-cyclodextrin to deionized water and add NaOH aqueous solution for alkalization to change the -OH in the raw material to -ONa; (4) Add silanized montmorillonite to the solution obtained in step (3), stir for 30 min, raise the temperature and slowly add epichlorohydrin dropwise to the reaction solution. After the addition is complete, continue the reaction. After the reaction is complete, cool to room temperature, wash the product repeatedly with anhydrous ethanol and deionized water, and dry it under vacuum at 70 °C to obtain corn cob / cyclodextrin / montmorillonite composite adsorbent material.

2. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: The corn cob powder used in step (1) is 35 mesh, boiled in water for 3 hours, and soaked for 24 hours.

3. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: In step (2), the volume ratio of ethanol to water is 1:1 to 12:1; the acidic condition is achieved by adjusting the pH to 4 with acetic acid; and the mass ratio of montmorillonite to silane coupling agent KH-560 is 10:

7.

4. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: In step (3), the mass ratio of corn cob powder to β-cyclodextrin is 1:0.3~1:

2.

5. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: The amount of NaOH aqueous solution used in step (3) is 25~75mL / g corn cob powder, and the mass concentration is 5%~25%; the alkalization time is 12h.

6. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: In step (4), the mass ratio of silanized montmorillonite to corn cob is 0.3:1 to 5:1; the amount of epichlorohydrin is 3 to 25 mL / g corn cob powder, and the dropping rate of epichlorohydrin is 1 drop / second.

7. The preparation method of the corn cob / cyclodextrin / montmorillonite composite adsorbent material according to claim 1, characterized in that: The reaction temperature in step (4) is 20~80℃; the reaction time is 4~48h.

8. A corn cob / cyclodextrin / montmorillonite composite adsorbent material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the corn cob / cyclodextrin / montmorillonite composite adsorbent material as described in claim 8 in the adsorption of organic dye molecules.

10. The application according to claim 9, characterized in that: The organic dye molecule is malachite green; 10 mg of corn cob / cyclodextrin / montmorillonite composite material is weighed and added to 20 mL of malachite green dye solution with a mass concentration of 30~400 mg / L. Adsorption is carried out at 20~60℃ with magnetic stirring at 800 rpm for 1~360 min, and the pH value is 3~13.

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