A preparation method of a gellan gum / ZIF-8 composite aerogel for dye adsorption
By preparing gellan gum/ZIF-8 composite aerogel, the problems of MOF material recycling and environmental pollution were solved, and a highly efficient dye adsorption effect was achieved, especially the efficient removal of malachite green.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2024-01-04
- Publication Date
- 2026-06-05
AI Technical Summary
Existing technologies are difficult to effectively recycle and mass-produce micron or nano-sized MOF materials, especially ZIF-8, and traditional adsorbents are prone to causing environmental pollution after adsorption.
Using gellan gum as a carrier, a gellan gum/ZIF-8 composite aerogel was prepared. Taking advantage of the three-dimensional mesoporous structure and good biocompatibility of gellan gum, ZIF-8 material was loaded to form a recyclable composite aerogel.
It achieves efficient recovery and large-scale production of ZIF-8, avoids environmental pollution from powdered adsorbents, and has excellent adsorption effect on cationic dye malachite green, with an adsorption rate of up to 98%.
Smart Images
Figure CN117619358B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the preparation and application of aerogels, and particularly to a method for preparing and applying a gellan gum / ZIF-8 composite aerogel for dye adsorption, belonging to the field of chemistry. Background Technology
[0002] In recent years, the aquatic environment has been increasingly polluted by anthropogenic pollutants, including heavy metals, dyes, surfactants, and pesticides. Wastewater treatment technologies include membrane separation, adsorption, flocculation, coagulation, advanced oxidation, and ozonation. Among these, adsorption is the conventional and preferred technology for treating dye-containing wastewater. Metal-organic frameworks (MOFs) are a new type of porous functional material with controllable structure and high thermal stability. MOFs have attracted much attention in reducing emissions of environmental pollutants such as dyes, heavy metals, and benzene-based organic compounds, showing significant advantages and application prospects. Among various MOF materials, ZIF-8 (zeolite imidazole framework-8) is one of the most studied MOFs due to its excellent stability and hydrophobicity. However, the size of MOFs is usually in the micrometer or nanometer range, making them difficult to separate using traditional methods (centrifugation or filtration), which makes recovery difficult and limits their large-scale production. An effective way to solve the above problems is to find suitable supports to prepare MOF composite materials that can be easily adsorbed and recovered. Aerogels are a suitable low-density support with an open three-dimensional mesoporous structure and high specific surface area. It is noteworthy that aerogels float on liquids, making them easy to recover. Therefore, the application of this recyclable material in adsorption or separation has attracted increasing attention from researchers. Gellan Gum (GG) is a water-soluble anionic polysaccharide derived from *Sphingomonas oligosporus*, a novel microbial polysaccharide produced by microbial fermentation under aerobic conditions. Gellan Gum is non-toxic, possesses good biocompatibility and biodegradability, and is inexpensive. Aerogels using gellan Gum as a matrix to support MOF materials have never been publicly disclosed before. Summary of the Invention
[0003] The purpose of this invention is to provide a method for preparing and applying a gellan gum / ZIF-8 composite aerogel for dye adsorption.
[0004] To achieve the objective of this invention, the following technical solution is adopted: a method for preparing a gellan gum / ZIF-8 composite aerogel for dye adsorption, comprising the following steps:
[0005] S1: Zinc nitrate hexahydrate and dimethylimidazole were added to methanol solution respectively, and stirred for 3-5 minutes at room temperature. The two solutions were then mixed at room temperature and stirred for 24 hours. ZIF-8 was then prepared by centrifugation and vacuum drying.
[0006] S2: Add ZIF-8 to deionized water, stir at room temperature for half an hour, and sonicate for 1.5 hours to obtain ZIF-8 suspension A;
[0007] S3: Add gellan gum to a 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain solution B;
[0008] S4: Add suspension A to solution B, heat and stir at 95 °C for 1.5 hours to obtain mixed solution C;
[0009] S5: Pour the mixed solution C into the corresponding mold and let it stand and cool for 1 hour to obtain gellan gum / ZIF-8 composite hydrogel;
[0010] S6: Gellan gel / ZIF-8 composite hydrogel was pre-frozen at -18 ℃ for 12 hours and then freeze-dried for 24 hours to obtain Gellan gel / ZIF-8 composite aerogel.
[0011] Furthermore, in step S1, the molar ratio of zinc nitrate hexahydrate to dimethylimidazole is 1:8.
[0012] An application of a gellan gum / ZIF-8 composite aerogel, wherein the composite aerogel is used for dye adsorption.
[0013] The positive and beneficial technical effects of this invention are as follows: Compared with the prior art, this invention has the following characteristics: The preparation method of this invention is simple and reliable, and the raw material gellan gum is a natural polymer with abundant and inexpensive resources; The gellan gum / ZIF-8 composite aerogel prepared by this invention solves the defects of current powder adsorbents that cause secondary pollution to the environment after adsorption and are not easy to recycle; The gellan gum / ZIF-8 composite aerogel of this invention has excellent adsorption effect on the cationic dye malachite green. Attached Figure Description
[0014] Figure 1 These are the infrared spectra of ZIF-8, GG, and GG / ZIF-8 prepared in Examples 1, 2, and 3.
[0015] Figure 2 These are X-ray diffraction patterns of ZIF-8, GG, and GG / ZIF-8 prepared in Examples 1, 2, and 3.
[0016] Figure 3 This is the nitrogen adsorption isotherm of ZIF-8 prepared in Example 1.
[0017] Figure 4 This is the nitrogen adsorption isotherm of GG / ZIF-8 prepared in Example 3.
[0018] Figure 5This is the nitrogen adsorption isotherm of GG prepared in Example 2.
[0019] Figure 6 These are the compressive stress-strain curves of GG and GG / ZIF-8 prepared in Examples 2 and 3.
[0020] Figure 7 The adsorption effect of ZIF-8, GG, and GG / ZIF-8 prepared in Examples 1, 2, and 3 on malachite green is shown.
[0021] Figure 8 This refers to the adsorption cycle of malachite green by GG / ZIF-8 prepared in Example 3. Detailed Implementation
[0022] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.
[0023] Example 1:
[0024] 2.304 g of zinc nitrate hexahydrate and 5.2808 g of dimethylimidazole were added to 45 g of methanol solution respectively. After stirring at room temperature for 3-5 minutes, the two solutions were mixed and stirred at room temperature for 24 hours, and then ZIF-8 was prepared by centrifugation and vacuum drying. Example 2:
[0025] 1) Add 200 mg of gellan gum to 10 mL of 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain GG solution;
[0026] 2) Pour the GG solution into the corresponding mold and let it stand and cool for 1 hour to obtain GG hydrogel;
[0027] 3) GG hydrogel was pre-frozen at -18 ℃ for 12 hours and then freeze-dried for 24 hours to obtain GG aerogel. Example 3:
[0028] 1) Add 2.304 g of zinc nitrate hexahydrate and 5.2808 g of dimethylimidazole to 45 g of methanol solution respectively. Stir for 3-5 minutes at room temperature, then mix and stir the two solutions at room temperature for 24 hours. Finally, prepare ZIF-8 by centrifugation and vacuum drying.
[0029] 2) Add 200 mg of ZIF-8 to 10 mL of deionized water, stir at room temperature for half an hour, and sonicate for 1.5 hours to obtain ZIF-8 suspension A;
[0030] 3) Add 200 mg of gellan gum to 10 mL of 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain solution B;
[0031] 4) Pour suspension A into solution B, heat and stir at 95 °C for 1.5 hours to obtain mixed solution C;
[0032] 5) Pour the mixed solution C into the corresponding mold and let it stand and cool for 1 hour to obtain gellan gum / ZIF-8 composite hydrogel;
[0033] 6) The gellan gel / ZIF-8 composite hydrogel was pre-frozen at -18 ℃ for 12 hours and then freeze-dried for 24 hours to obtain the gellan gel / ZIF-8 composite aerogel adsorbent material. Example 4:
[0034] 1) Add 2.304 g of zinc nitrate hexahydrate and 5.2808 g of dimethylimidazole to 45 g of methanol solution respectively. Stir for 3-5 minutes at room temperature, then mix and stir the two solutions at room temperature for 24 hours. Finally, prepare ZIF-8 by centrifugation and vacuum drying.
[0035] 2) Add 100 mg of ZIF-8 to 10 mL of deionized water, stir at room temperature for half an hour, and sonicate for 1.5 hours to obtain ZIF-8 suspension A;
[0036] 3) Add 200 mg of gellan gum to 10 mL of 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain solution B;
[0037] 4) Pour suspension A into solution B, heat and stir at 95 °C for 1.5 hours to obtain mixed solution C;
[0038] 5) Pour the mixed solution C into the corresponding mold and let it stand and cool for 1 hour to obtain gellan gum / ZIF-8 composite hydrogel;
[0039] 6) The gellan gel / ZIF-8 composite hydrogel was pre-frozen at -18 ℃ for 12 hours and then freeze-dried for 24 hours to obtain the gellan gel / ZIF-8 composite aerogel adsorbent material. Example 5:
[0040] 1) Add 2.304 g of zinc nitrate hexahydrate and 5.2808 g of dimethylimidazole to 45 g of methanol solution respectively. Stir for 3-5 minutes at room temperature, then mix and stir the two solutions at room temperature for 24 hours. Finally, prepare ZIF-8 by centrifugation and vacuum drying.
[0041] 2) Add 400 mg of ZIF-8 to 10 mL of deionized water, stir at room temperature for half an hour, and sonicate for 1.5 hours to obtain ZIF-8 suspension A;
[0042] 3) Add 200 mg of gellan gum to 10 mL of 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain solution B;
[0043] 4) Pour suspension A into solution B, heat and stir at 95 °C for 1.5 hours to obtain mixed solution C;
[0044] 5) Pour the mixed solution C into the corresponding mold and let it stand and cool for 1 hour to obtain gellan gum / ZIF-8 composite hydrogel;
[0045] 6) The gellan gel / ZIF-8 composite hydrogel was pre-frozen at -18 ℃ for 12 hours and then freeze-dried for 24 hours to obtain the gellan gel / ZIF-8 composite aerogel adsorbent material.
[0046] The infrared spectra of ZIF-8, GG, and GG / ZIF-8 prepared in specific Examples 1, 2, and 3 are shown below. Figure 1 As shown. For ZIF-8, 1584 cm -1 The peaks at 1425 and 1311 cm⁻¹ are attributed to C=N stretching vibrations, while those at 1425 and 1311 cm⁻¹ are attributed to C=N stretching vibrations. -1 The strong peak at 1147-995 cm⁻¹ is attributed to the stretching vibration of the entire imidazole ring; -1 The spectral bands within this range correspond to the in-plane bending vibrations of the aromatic rings, at 759 and 694 cm⁻¹. -1 The peak at 420 cm⁻¹ corresponds to the bending vibration of aromatic CH₄. -1 The characteristic peak at 3315 cm⁻¹ is related to N-Zn. For GG, the peak at 3315 cm⁻¹ is... -1 There is a relatively broad peak nearby, belonging to the stretching vibration peak of the OH group, at 1603 cm⁻¹. -1 and 1407 cm -1 The peak at that location is -COO - Asymmetric and symmetric stretching vibration peaks, 1032 cm⁻¹ -1 The peak at [value] represents the bending vibration peak of the OH group at the C6 position of the gellan gel. For the GG / ZIF-8 composite aerogel, peaks at 1311, 1147, 995, 759, 694, and 420 cm⁻¹ can be observed. -1 The presence of characteristic peaks of ZIF-8 at certain positions indicates that ZIF-8 has been successfully loaded onto GG.
[0047] The X-ray diffraction patterns of ZIF-8, GG, and GG / ZIF-8 prepared in specific embodiments 1, 2, and 3 are shown below. Figure 2As shown. Characteristic diffraction peaks of ZIF-8 can be observed between 5° and 30°, including (011) diffraction at 7.2°, (002) diffraction at 10.3°, (112) diffraction at 12.6°, (022) diffraction at 14.6°, (013) diffraction at 16.4°, and (222) diffraction at 17.9°. Two diffraction peaks were observed in the spectrum of GG aerogel at positions up to 28.1° and 40.2°. Some characteristic diffraction peaks of ZIF-8 remained unchanged after blending with GG aerogel, indicating that ZIF-8 was successfully introduced into GG aerogel.
[0048] The nitrogen adsorption isotherms of ZIF-8, GG, and GG / ZIF-8 prepared in specific Examples 1, 2, and 3 are as follows: Figure 3 , 4 As shown in Figure 5, the specific surface area of ZIF-8 is 1320 m². 2 g -1 The specific surface area of GG is 0.25 m². 2 g -1 The specific surface area of GG / ZIF-8 is 412 m². 2 g -1 Nitrogen adsorption isotherms indicate that ZIF-8 has a microporous structure, and the specific surface area increases significantly after adding ZIF-8 to GG aerogel. This suggests that ZIF-8 plays a dominant role in the adsorption of malachite green, while GG serves as the matrix supporting ZIF-8.
[0049] The compressive stress-strain curves of GG and GG / ZIF-8 prepared in specific embodiments 2 and 3 are shown below. Figure 6 As shown, when GG and GG / ZIF-8 aerogels are compressed to 90%, it can be seen that the mechanical properties of GG aerogel are improved after the addition of ZIF-8. This ensures that the appearance of GG / ZIF-8 aerogel remains basically unchanged during the adsorption process, and it can adsorb malachite green in a block form.
[0050] The adsorption effects of ZIF-8, GG, and GG / ZIF-8 on malachite green prepared in specific Examples 1, 2, and 3 are as follows: Figure 7 As shown, GG showed virtually no adsorption effect on malachite green; in some samples, the dye concentration even increased slightly after adsorption. In contrast, the GG / ZIF-8 aerogel exhibited an adsorption effect on malachite green that was almost identical to that of ZIF-8 powder, achieving a removal rate of over 98%. This indicates that the GG / ZIF-8 aerogel prepared in this invention can adsorb malachite green in a block form without affecting the adsorption effect, thus solving the problems of secondary pollution and difficulty in recycling caused by current powdered adsorbents after adsorption.
[0051] The gellan gum used in this application has CAS number 71010-52-1, is of biotechnology grade, low acyl type, and can be purchased from Shanghai Maclean Biochemical Technology Co., Ltd.
[0052] The adsorption cycle performance of malachite green by the GG / ZIF-8 aerogel prepared in Specific Example 3 is as follows: Figure 8 As shown, the removal rate of malachite green reached over 95% in the first three cycles, the removal rate dropped to 80% in the fourth cycle but still showed good adsorption effect, and the removal rate dropped to around 50% in the fifth cycle. This may be because with the increase of the number of cycles, the material is somewhat worn down and the adsorption sites tend to become saturated, making complete desorption difficult.
[0053] Repeating the above embodiments multiple times yielded similar results, indicating that the preparation method of this invention has good repeatability.
Claims
1. A method for preparing a gellan gum / ZIF-8 composite aerogel for dye adsorption, characterized in that, Includes the following steps: S1: Zinc nitrate hexahydrate and dimethylimidazole were added to methanol solution respectively, and stirred for 3-5 minutes at room temperature. The two solutions were then mixed at room temperature and stirred for 24 hours. ZIF-8 was then prepared by centrifugation and vacuum drying. S2: Add ZIF-8 to deionized water, stir at room temperature for half an hour, and sonicate for 1.5 hours to obtain ZIF-8 suspension A; S3: Add gellan gum to a 0.1 M potassium chloride solution, heat and stir at 95 °C until completely dissolved to obtain solution B; S4: Add suspension A to solution B, heat and stir at 95 °C for 1.5 hours to obtain mixed solution C; S5: Pour the mixed solution C into the corresponding mold and let it stand and cool for 1 hour to obtain gellan gum / ZIF-8 composite hydrogel; S6: Pre-freeze the gellan gum / ZIF-8 composite hydrogel at -18 ℃ for 12 hours, and then freeze-dry it for 24 hours to obtain the gellan gum / ZIF-8 composite aerogel; the molar ratio of zinc nitrate hexahydrate and dimethylimidazole in step S1 is 1:
8.
2. An application of a Gellan gel / ZIF-8 composite aerogel, characterized in that, The composite aerogel is obtained by the preparation method described in claim 1. The composite aerogel is used in dye adsorption, in which the composite aerogel adsorbs dye in a block form.