An aluminum cluster / cellulose composite adsorbent for adsorbing organic pollutants in water

Abstract

This invention relates to the field of adsorbent materials, and particularly to an aluminum cluster / cellulose composite adsorbent material for adsorbing organic pollutants in water. The preparation method of this adsorbent material includes: dissolving NaClO2 in water, adjusting the pH to 2-6, sonicating, then adding a dried balsa wood sample, and reacting at a constant temperature of 40-100°C with stirring; washing and drying to obtain a cellulose framework material; immersing the cellulose framework material in an aqueous solution containing tetramethylpiperidine and NaBr, adding NaClO aqueous solution dropwise, adjusting the pH to 8-12, and reacting at a constant temperature of 20-80°C with stirring; then adjusting the pH to neutral; washing and drying to obtain a modified cellulose framework material; dissolving aluminum isopropoxide: benzoic acid derivative: pyrazole derivative: piperazine in an organic solvent at a molar ratio of 1:1:(10-100):(0-1), sonicating, adding the modified cellulose framework material, placing in a high-pressure reactor, reacting at a constant temperature of 50-150°C, cooling, washing, and freeze-drying to obtain the aluminum cluster / cellulose composite adsorbent material.

Description

Technical Field

[0001] This invention relates to the field of adsorption materials, and in particular to an aluminum cluster / cellulose composite adsorption material for adsorbing organic pollutants in water. Background Technology

[0002] With population growth and industrialization, large amounts of organic pollutants enter ecosystems. These pollutants are not only widespread and abundant, but also complex in composition and highly toxic. When the self-purification capacity of an ecosystem exceeds its maximum limit, if water sources containing organic pollutants are used for aquaculture and crop irrigation for a long period, toxic substances containing active groups such as azo groups, sulfonic acid groups, nitro groups, carbonyl groups, hydroxyl groups, carboxyl groups, and amine groups will accumulate in the food chain and eventually enter the human body, thus endangering human health.

[0003] There are many methods for treating organic pollutants in water, generally including flocculation, adsorption, electrolysis, membrane separation, photocatalysis, and oxidation. Compared with other methods, adsorption has advantages such as high cost-effectiveness, good reusability, simple operation, high adsorption efficiency, and low possibility of secondary pollution. Commonly used adsorbents such as activated carbon, graphene oxide, carbon nanotubes, clay, and zeolite have poor adsorption effects on organic pollutants in water, and these adsorbents are usually in powder form, making them difficult to recover and reuse, resulting in poor reusability. Summary of the Invention

[0004] Technical issues:

[0005] Commonly used adsorbents have poor adsorption effects on organic pollutants in water, and they are usually in powder form, making them difficult to recycle and reuse, resulting in poor reusability.

[0006] Technical concept:

[0007] First, balsa wood undergoes delignification, followed by tetramethylpiperidine (TEMPO) oxidative modification to oxidize the hydroxyl groups on the cellulose to carboxyl groups. The central metal ion Al on the aluminum cluster... 3+ It can coordinate with the carboxyl groups on the modified cellulose backbone, and combine aluminum clusters with oxidized modified cellulose to enhance adsorption capacity. At the same time, it can load aluminum clusters on bulk cellulose materials to facilitate recycling.

[0008] Technical solution:

[0009] This invention provides a method for preparing an aluminum cluster / cellulose composite adsorbent material, comprising the following steps:

[0010] S1: Dissolve NaClO2 in water, add acetic acid buffer to adjust the pH to 2-6, mix well, then add the dried balsa wood sample, stir at a constant temperature of 40-100℃ to remove lignin; wash, dry, and obtain cellulose skeleton material; wherein, the weight ratio of NaClO2:water:balsa wood sample is (0.1-10):(50-200):1.

[0011] S2: Immerse the cellulose backbone material in an aqueous solution containing tetramethylpiperidine and NaBr, add NaClO aqueous solution dropwise to initiate the oxidation reaction, adjust the pH to 8-12, and stir the reaction at a constant temperature of 20-80℃; then, terminate the reaction by adjusting the pH to neutral; wash and dry to obtain the modified cellulose backbone material; wherein, the weight ratio of cellulose backbone material:tetramethylpiperidine:NaBr:NaClO is 1:(0.01-10):(0.1-10):(0.1-10);

[0012] S3: Dissolve aluminum isopropoxide, benzoic acid derivative, pyrazole derivative, and piperazine in an organic solvent at a molar ratio of 1:1:(10-100):(0-1), disperse by ultrasonication, add modified cellulose skeleton material, place in a high-pressure reactor, react at a constant temperature of 50-150℃, cool, wash, and freeze-dry to obtain aluminum cluster / cellulose composite adsorbent material.

[0013] In one embodiment of the present invention, in step S1, the balsa wood sample is balsa wood.

[0014] In one embodiment of the present invention, in step S3, the benzoic acid derivative is at least one of benzoic acid and 4-fluorobenzoic acid; the pyrazole derivative is at least one of pyrazole and 4-methylpyrazole; and all organic solvents are at least one of dimethylformamide and methanol.

[0015] In one embodiment of the present invention, in step S3, the temperature of the isothermal reaction is 100°C.

[0016] In one embodiment of the present invention, in step S3, the isothermal reaction time is 3 days.

[0017] In one embodiment of the present invention, in step S2, the weight ratio of cellulose skeleton material:tetramethylpiperidine:NaBr:NaClO is 1:0.1:0.75:1.3, and the reaction is carried out at a constant temperature of 20-80°C with stirring for 4-10 hours.

[0018] In one embodiment of the present invention, in step S1, the weight ratio of NaClO2:water:balsa wood sample is 1:100:1; the reaction is carried out at a constant temperature of 40-100°C for 2-20 hours.

[0019] The present invention relates to an aluminum cluster / cellulose composite adsorbent material prepared by the method described in any one of the above-mentioned methods.

[0020] The aluminum cluster / cellulose composite adsorbent material provided by this invention is used in the treatment of wastewater containing organic pollutants.

[0021] In one embodiment of the present invention, the organic pollutant includes at least one of thymol blue, cresol red, acid chrome blue K, methyl orange, Congo red, bisphenol A, p-nitrophenol, or nonylphenol.

[0022] Beneficial effects:

[0023] This invention first involves delignifying natural balsa wood, resulting in a cellulose framework material that retains the porous structure of natural wood. Through TEMPO oxidation modification, the hydroxyl groups on the cellulose framework are oxidized to carboxyl groups, increasing the microscopic voids in the resulting modified cellulose framework material. This improves both its porosity and specific surface area, facilitating subsequent functional modifications. Utilizing the porous structure and large specific surface area of ​​aluminum oxide clusters (AlOCs), a composite adsorbent material is synthesized in situ on the modified cellulose framework. The resulting adsorbent material exhibits high porosity, high specific surface area, and abundant adsorption sites, along with good regenerability, environmental friendliness, reusability, and easy recycling. It demonstrates excellent adsorption performance for various organic dyes, bisphenol A, p-nitrophenol, nonylphenol, and other organic pollutants. Attached Figure Description

[0024] Figure 1 Scanning electron microscope (SEM) images of the four AlOCs / cellulose composite adsorbent materials prepared in Examples 1-4: AlOC-15 / Wood Figure 1 a) AlOC-20 / Wood Figure 1 b) AlOC-22 / Wood Figure 1 c) and AlOC-26-NC / Wood Figure 1 d);

[0025] Figure 2 The infrared spectra of the four AlOCs / cellulose composite adsorbent materials, the modified cellulose skeleton, and the natural balsa wood prepared in Examples 1-4 are shown.

[0026] Figure 3 The image shows a scanning electron microscope (SEM) image of the aluminum cluster / cellulose composite adsorbent (AlOC15 / Wood) prepared in Comparative Example 1 without TEMPO oxidation modification. Detailed Implementation

[0027] Example 1

[0028] A method for preparing an aluminum cluster / cellulose composite adsorbent material includes the following steps:

[0029] S1: Dissolve 1g of NaClO2 in 100mL of deionized water, add acetic acid buffer to adjust the pH to 4.6, sonicate for 15min, then add 1g of dried blocky balsa wood sample, stir at 80℃ for 18h to remove lignin; wash and dry to obtain cellulose skeleton material.

[0030] S2: Immerse 1g of cellulose backbone material in 100mL of an aqueous solution containing 0.1g tetramethylpiperidine (TEMPO) and 0.75g NaBr. Add 12g of NaClO aqueous solution with an available chlorine content of 5.2% (i.e., 1.3g NaClO) dropwise to initiate the oxidation reaction. Adjust the pH to 10 with 0.1M NaOH aqueous solution and stir at 25℃ for 6h. Then, terminate the reaction by adjusting the pH to neutral by adding 0.1M HCl aqueous solution. Wash and dry to obtain the modified cellulose backbone material.

[0031] S3: Dissolve aluminum isopropoxide, benzoic acid, and pyrazole in 5 mL of dimethylformamide (DMF) at a molar ratio of 1:1:29.38, sonicate for 15 min, add 1 g of modified cellulose skeleton material, place in a polytetrafluoroethylene high-pressure reactor, react at 100 °C for 3 days, cool, wash, and freeze-dry to obtain AlOC-15 / cellulose composite adsorbent material, denoted as AlOC-15 / Wood.

[0032] Example 2

[0033] A method for preparing an aluminum cluster / cellulose composite adsorbent material, referring to Example 1, except that 4-fluorobenzoic acid is used instead of benzoic acid in step S3; the AlOC-20 / cellulose composite adsorbent material is obtained, denoted as AlOC-20 / Wood.

[0034] Example 3

[0035] A method for preparing an aluminum cluster / cellulose composite adsorbent material, referring to Example 1, differs only in that 4-methylpyrazole is used instead of pyrazole in step S3, and the molar ratio of aluminum isopropoxide:benzoic acid:4-methylpyrazole is 1:1:48.72; thus, an AlOC-22 / cellulose composite adsorbent material is obtained, denoted as AlOC-22 / Wood.

[0036] Example 4

[0037] A method for preparing an aluminum cluster / cellulose composite adsorbent material, referring to Example 3, differs only in that piperazine is added in step S3; the molar ratio of aluminum isopropoxide: benzoic acid: 4-methylpyrazole: piperazine is 1:1:48.72:1; AlOC-26-NC / cellulose composite adsorbent material is obtained, denoted as AlOC-26-NC / Wood.

[0038] Comparative Example 1 - Aluminum cluster / cellulose composite adsorbent without TEMPO oxidation modification

[0039] A method for preparing an aluminum cluster / cellulose composite adsorbent material, referring to Example 1, differs only in that step S2 is omitted, and the modified cellulose framework material in step S3 is replaced with the cellulose framework material obtained in step S1, to obtain the aluminum cluster / cellulose composite adsorbent material, denoted as AlOC15 / Wood.

[0040] Figure 1 These are scanning electron microscope (SEM) images of the four AlOCs / cellulose composite adsorbent materials prepared in Examples 1 to 4. The multi-channel structure of the wood is clearly visible in the images, indicating that the channel structure was not destroyed after a series of chemical treatments. Furthermore, the presence of the multi-channel structure increases the porosity and specific surface area of ​​the adsorbent material (the specific surface area of ​​natural balsa wood is only 1.01 m²). 2 The specific surface area of ​​AlOC-26-NC / Wood is 20.67 m² / g. 2 / g), which is beneficial for increasing the contact area between AlOC-15 and the aqueous solution when removing hexavalent chromium from water. It can also be seen that AlOC-15 / Wood ( Figure 1 a) and AlOC-20 / Wood Figure 1 b) The crystals are all regular plate-like in shape, AlOC-22 / Wood ( Figure 1 c) and AlOC-26-NC / Wood Figure 1 d) The crystals exhibit a regular polyhedral shape. Furthermore, a large number of AlOCs crystal particles are clearly visible attached to the surface of the wood channel in all four images. Figure 2 The images show infrared (IR) images of the four AlOCs / cellulose composite adsorbent materials prepared in Examples 1 to 4. The images demonstrate the successful oxidation of hydroxyl groups on the cellulose backbone to carboxyl groups. The SEM and IR images confirm the successful preparation of the AlOCs / cellulose composite adsorbent materials.

[0041] Figure 3 This is a scanning electron microscope (SEM) image of the aluminum cluster / cellulose composite adsorbent (AlOC15 / Wood) prepared in Comparative Example 1 without TEMPO oxidation modification. As can be seen from the image, compared with... Figure 1 Compared to AlOC-15 / Wood, the in-situ formation of aluminum clusters on AlOC15 / Wood composite materials is significantly reduced.

[0042] Test Example 1

[0043] The five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 were used to test the adsorption of eight dyes: crystal violet, methylene blue, rose red B, thymol blue, cresol red, acid chrome blue K, methyl orange, and Congo red. In the adsorption experiments, 10 mg of each AlOCs / cellulose composite adsorbent was weighed and added to 10 mL of each of the eight dye solutions with an initial concentration of 0.1 mmol / L and a neutral pH. The solutions were then kept at a constant temperature and shaken at 25°C for 24 h. After adsorption, the adsorption capacity of different dyes was compared by ultraviolet absorption spectroscopy. The results are shown in Table 1.

[0044] The adsorption performance tests of the five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 for different dyes showed that the four adsorbents prepared in Examples 1-4 exhibited similar adsorption performance for dyes with different structures. Considering that the four adsorbents have similar structures, differing only in the substituents on the ligands, it indicates that the substituents on the ligands have little impact on the adsorption performance of the materials. The four adsorbents prepared in Examples 1-4 showed poor removal rates for three positively charged cationic dyes (crystal violet, methylene blue, and rose red B), but good removal rates for five negatively charged anionic dyes (thymol blue, cresol red, acid chrome blue K, methyl orange, and Congo red). The adsorption performance for methyl orange and Congo red was particularly excellent, with removal efficiencies exceeding 97%. The test results of Comparative Example 1 showed that AlOC15 / Wood exhibited significantly reduced adsorption capacity for eight organic dyes, with removal efficiencies for methyl orange and Congo red at only 38% and 39%, respectively.

[0045] Test Example 2

[0046] The five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 were used to test the adsorption of bisphenol A. In the adsorption experiment, 10 mg of each AlOCs / cellulose composite adsorbent was weighed and added to 10 mL of bisphenol A solution with an initial concentration of 0.1 mmol / L and a neutral pH. The solution was then subjected to uniform shaking at room temperature (25°C) for 24 h. After adsorption, the adsorption capacity of the five AlOCs / cellulose composite adsorbents was compared by ultraviolet absorption spectroscopy, as shown in Table 1.

[0047] The adsorption performance tests of the four AlOCs / cellulose composite adsorbents prepared in Examples 1-4 for bisphenol A showed that the four adsorbents had similar adsorption performance for bisphenol A. This is because the four adsorbents prepared in Examples 1-4 have similar structures, and the removal efficiency of all four was above 84%. The test results of Comparative Example 1 showed that the adsorption capacity of AlOC15 / Wood for bisphenol A was significantly reduced, with a removal efficiency of only 29%.

[0048] Test Example 3

[0049] The five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 were used to test the adsorption of p-nitrophenol. In the adsorption experiment, 10 mg of each AlOCs / cellulose composite adsorbent was weighed and added to 10 mL of p-nitrophenol solution with an initial concentration of 0.1 mmol / L and a neutral pH. The solution was then subjected to uniform shaking at room temperature (25°C) for 24 h. After adsorption, the adsorption capacity of the five AlOCs / cellulose composite adsorbents was compared by ultraviolet absorption spectroscopy, as shown in Table 1.

[0050] The adsorption performance tests of the four AlOCs / cellulose composite adsorbents prepared in Examples 1-4 for p-nitrophenol showed that, based on the similar structures of the four adsorbents, they exhibited similar adsorption performance for p-nitrophenol, with removal efficiencies all exceeding 82%. However, the test results of Comparative Example 1 showed that AlOC15 / Wood exhibited significantly reduced adsorption capacity for p-nitrophenol, with a removal efficiency of only 28%.

[0051] Test Example 4

[0052] The five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 were used to test the adsorption of nonylphenol. In the adsorption experiment, 10 mg of each AlOCs / cellulose composite adsorbent was weighed and added to 10 mL of nonylphenol solution with an initial concentration of 0.1 mmol / L and a neutral pH. The solution was then subjected to constant temperature shaking at 25°C for 24 h. After adsorption, the adsorption capacity of the five AlOCs / cellulose composite adsorbents was compared by ultraviolet absorption spectroscopy, as shown in Table 1.

[0053] The adsorption performance tests of the four AlOCs / cellulose composite adsorbents prepared in Examples 1-4 for nonylphenol showed that the four adsorbents had similar adsorption performance for nonylphenol. This is because the four adsorbents prepared in Examples 1-4 have similar structures, and their removal efficiencies are all above 80%. The test results of Comparative Example 1 showed that AlOC15 / Wood had a significantly reduced adsorption capacity for nonylphenol, with a removal efficiency of only 28%.

[0054] Table 1 shows the removal efficiencies of five AlOCs / cellulose composite adsorbents prepared in Examples 1-4 and Comparative Example 1 for different organic pollutants.

[0055] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Crystal Violet 5％ 7％ 8％ 6％ 2％ Methylene blue 8％ 9％ 7％ 8％ 3％ Rose Red B 23％ 22％ 28％ 25％ 9％ Thymol Blue 36％ 38％ 39％ 37％ 13％ Cresol Red 37％ 46％ 48％ 49％ 14％ Acid Chrome Blue K 45％ 47％ 46％ 49％ 19％ Methyl orange 97％ 97％ 97％ 98％ 38％ Congo Red 97％ 98％ 97％ 97％ 39％ Bisphenol A 84％ 84％ 85％ 85％ 29％ p-Nitrophenol 82％ 83％ 82％ 84％ 28％ Nonylphenol 81％ 80％ 82％ 81％ 28％

[0056] Based on the test results of the adsorption performance of different organic pollutants, it can be seen that the four AlOCs / cellulose composite adsorbent materials prepared in Examples 1 to 4 all have high adsorption capacity for various organic dyes, bisphenol A, p-nitrophenol, and nonylphenol. This further illustrates that the composite adsorbent material of the present invention has a good adsorption effect on organic pollutants in water.

[0057] Test Example 5

[0058] The AlOC-15 / Wood prepared in Example 1 was subjected to a five-cycle adsorption test on methyl orange. In the adsorption experiment, 10 mg of AlOC-15 / Wood was weighed and added to 10 mL of a methyl orange solution with an initial concentration of 0.1 mmol / L and a neutral pH. The solution was kept at room temperature (25°C) and subjected to uniform shaking for 24 h. After adsorption, the adsorption efficiency was calculated using UV absorption spectroscopy. AlOC-15 / Wood was then recovered and placed in a 0.1 M NaOH aqueous solution for 4 h for desorption, followed by the next adsorption test. The adsorption efficiencies after five cycles were 97%, 95%, 93%, 92%, and 90%, respectively. The test results show that the AlOCs / cellulose composite adsorbent material prepared in Example 1 still exhibits good adsorption performance and reusability after five cycles.

[0059] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing an aluminum cluster / cellulose composite adsorbent material, characterized in that, Includes the following steps: S1: Dissolve NaClO2 in water, add acetic acid buffer to adjust the pH to 2-6, mix well, then add the dried balsa wood sample, and stir at a constant temperature of 40-100 ℃ to remove lignin. Wash and dry to obtain cellulose skeleton material; wherein the weight ratio of NaClO2 : water : balsa wood sample is (0.1~10) : (50~200) : 1; S2: Immerse the cellulose backbone material in an aqueous solution containing tetramethylpiperidine and NaBr, add NaClO aqueous solution dropwise to initiate the oxidation reaction, adjust the pH to 8-12, and stir the reaction at a constant temperature of 20-80 °C; then, terminate the reaction by adjusting the pH to neutral; wash and dry to obtain the modified cellulose backbone material; wherein, the weight ratio of cellulose backbone material: tetramethylpiperidine: NaBr: NaClO is 1: (0.01-10): (0.1-10): (0.1-10); S3: Dissolve aluminum isopropoxide, benzoic acid derivative, pyrazole derivative, and piperazine in an organic solvent at a molar ratio of 1:1:(10~100):(0~1), disperse by ultrasonication, add modified cellulose skeleton material, place in a high-pressure reactor, react at a constant temperature of 50~150 ℃, cool, wash, and freeze-dry to obtain aluminum cluster / cellulose composite adsorbent material.

2. The method according to claim 1, characterized in that, The balsa wood sample in step S1 is balsa wood.

3. The method according to claim 1, characterized in that, In step S3, the benzoic acid derivative is at least one of benzoic acid and 4-fluorobenzoic acid; the pyrazole derivative is at least one of pyrazole and 4-methylpyrazole; and the organic solvent used is at least one of dimethylformamide and methanol.

4. The method according to claim 1, characterized in that, In step S3, the reaction is carried out at a constant temperature of 50–150 °C for 1–5 days.

5. The method according to claim 4, characterized in that, In step S3, the reaction is carried out at a constant temperature of 100 °C for 3 days.

6. The method according to claim 1, characterized in that, In step S2, the weight ratio of the cellulose skeleton material: tetramethylpiperidine: NaBr: NaClO is 1: 0.1: 0.75: 1.3; the reaction is carried out at a constant temperature of 20-80 °C for 4-10 h.

7. The method according to claim 1, characterized in that, In step S1, the weight ratio of NaClO2 : water : balsa wood sample is 1 : 100 : 1; the reaction is carried out at a constant temperature of 40-100 °C for 2-20 h.

8. The aluminum cluster / cellulose composite adsorbent material prepared by the method according to any one of claims 1 to 7.

9. The application of the aluminum cluster / cellulose composite adsorbent material according to claim 8 in the treatment of wastewater containing organic pollutants.

10. The application according to claim 9, characterized in that, The organic pollutants include at least one of thymol blue, cresol red, acid chrome blue K, methyl orange, Congo red, bisphenol A, p-nitrophenol, or nonylphenol.

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