Aerogel for heavy metal ion adsorption and preparation method thereof
By preparing aerogels with Mannich base bridge structures, the limitation of existing aerogel materials that can only target one type of pollutant is overcome, and efficient adsorption and low-cost regeneration of multiple heavy metal ions are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SICHUAN UNIVERSITY OF SCIENCE AND ENGINEERING
- Filing Date
- 2024-12-27
- Publication Date
- 2026-06-16
Smart Images
Figure CN119751964B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of heavy metal ion adsorbent technology, specifically relating to an aerogel for heavy metal ion adsorption and its preparation method. Background Technology
[0002] Currently, with the rapid industrialization and economic development of human society, environmental pollution is becoming increasingly serious, with heavy metal pollution being a major source. Industrial wastewater and exhaust gases generate a large amount of waste, and heavy metal ions from these materials enter the soil or water bodies through natural sedimentation and rainwater leaching, thus entering the normal cycle of the ecosystem. After entering the human body through various pathways, heavy metals accumulate and pose serious threats to human health. Current methods for treating heavy metal wastewater mainly include chemical precipitation, neutralization, biological methods, membrane filtration, and adsorption. Among these, adsorption has received widespread attention due to its high efficiency, recyclability, and ease of treatment.
[0003] In adsorption methods, the performance of the adsorbent is the decisive factor in the removal of heavy metal ions. Aerogels possess advantages such as low density, high specific surface area, and high porosity, making them a promising class of adsorbent materials. More importantly, the composition of polluted water bodies is generally complex, and most traditional aerogels can only remove one type of pollutant, which greatly limits their practical application in pollutant adsorption. Therefore, there is an urgent need to develop a novel aerogel adsorbent material that is low-cost, renewable, and possesses multiple rapid adsorption effects. Summary of the Invention
[0004] The purpose of this invention is to provide an aerogel for the adsorption of heavy metal ions and a method for its preparation. The method involves first preparing a benzoxazine monomer, then thermally activating it to undergo ring-opening polymerization to form a Mannich base bridge. This structure can form a complex with heavy metal ions, achieving the adsorption purpose.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] One of the technical solutions of this invention is to provide a method for preparing an aerogel for the adsorption of heavy metal ions, comprising the following steps:
[0007] Phenolic compounds, primary amine compounds, and formaldehyde were mixed in a solvent, and after the reaction, a benzoxazine monomer suspension was obtained. After standing, the upper layer of solution was removed.
[0008] The remaining portion is first cured in stages to obtain a polybenzoxazine wet gel, and then dried to obtain an aerogel for heavy metal ion adsorption; or the remaining portion is first dried to obtain a polybenzoxazine aerogel precursor, and then cured in stages to obtain an aerogel for heavy metal ion adsorption.
[0009] Preferably, the molar ratio of the phenolic compound, the primary amine compound, and formaldehyde is 0.5–41:1:2–82.
[0010] Preferably, the raw materials blended in the solvent also include surfactants.
[0011] More preferably, the molar ratio of the phenolic compound, surfactant, primary amine compound and formaldehyde is 0.5-41:0-19:1:2-82, and the amount of surfactant is not 0.
[0012] More preferably, the surfactant is poloxamer F127 and / or poloxamer F68. Since the aerogel preparation process in this invention first yields a benzoxazine monomer suspension, adding a surfactant facilitates the preparation of the emulsion. Poloxamer is a high-molecular-weight nonionic surfactant that is readily soluble in ethanol and water. Such surfactants can interact with the preceding oligomers, which is more conducive to the preparation of the precursor emulsion.
[0013] Optionally, the phenolic compound includes one or more of resorcinol, bisphenolic acid, and tannic acid.
[0014] In phenolic compounds, the carboxyl groups in bisphenolic acids and the numerous phenolic hydroxyl groups on the surface of tannic acid both contribute to the chelation of heavy metal ions in the prepared aerogel.
[0015] Optionally, the primary amine compound includes one or more of ethylenediamine, hexamethylenediamine, decanediamine, triethylenetetramine, tetraethylenepentamine, and 3-amino-5-mercapto-1,2,4-triazole.
[0016] Optionally, the formaldehyde includes paraformaldehyde and / or an aqueous solution of formaldehyde.
[0017] Optionally, the solvent includes one or more of ethanol, water, dioxane, chloroform, toluene, and tetrahydrofuran.
[0018] Preferably, the curing temperature gradient of the polybenzoxazine wet gel is 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h and 90℃ / 3h respectively.
[0019] Optionally, the drying of the polybenzoxazine wet gel includes atmospheric pressure drying or vacuum drying; the temperature for atmospheric pressure drying is 50-70°C and the time is 24-48 hours; the temperature for vacuum drying is 50°C and the time is 24 hours.
[0020] Preferably, the drying temperature of the polybenzoxazine aerogel precursor is 80°C and the drying time is 72h; the temperature gradient for the segmented curing of the polybenzoxazine aerogel precursor is 140°C / 2h, 160°C / 2h, 180°C / 2h and 200°C / 3h respectively.
[0021] The preparation process of the aerogel in this invention involves first obtaining a benzoxazine monomer suspension or emulsion, followed by further curing to obtain a gel. Since a high-temperature resistant thermosetting polymer gel is prepared, a relatively high curing temperature is required. To avoid structural inhomogeneity that may be caused by curing at high temperatures, such as the formation of numerous large pores, a staged, gradual heating method is used to obtain a gel with a uniform internal structure.
[0022] The second technical solution of the present invention is to provide an aerogel for heavy metal ion adsorption prepared according to the above-mentioned preparation method of aerogel for heavy metal ion adsorption.
[0023] The third technical solution of the present invention provides an application of the above-mentioned aerogel for heavy metal ion adsorption in the adsorption of heavy metal ions.
[0024] The beneficial technical effects of the present invention are as follows:
[0025] The method for preparing aerogels for heavy metal ion adsorption provided by this invention is simple, has a short experimental cycle, and is low in cost.
[0026] The aerogel prepared by this invention for the adsorption of heavy metal ions contains abundant heteroatoms (such as N, O, S, etc.), which can chelate with heavy metal ions and improve adsorption performance.
[0027] The aerogel prepared by this invention for the adsorption of heavy metal ions has a large specific surface area, strong adsorption capacity, low environmental pollution, and good heat and acid resistance, and can be used in harsh environments such as high temperature and acid. Attached Figure Description
[0028] Figure 1 The infrared spectra of the polybenzoxazine aerogels prepared in Examples 1-5 are shown.
[0029] Figure 2 The TGA test results of the polybenzoxazine aerogels prepared in Examples 1-5 are shown in the figure.
[0030] Figure 3 The graph shows the acid resistance test results of the polybenzoxazine aerogels prepared in Examples 1-5.
[0031] Figure 4 The image shows a scanning electron microscope (SEM) image of the polybenzoxazine aerogel prepared in Example 1.
[0032] Figure 5 The image shows a scanning electron microscope (SEM) image of the polybenzoxazine aerogel prepared in Example 2.
[0033] Figure 6 The image shows a scanning electron microscope (SEM) image of the polybenzoxazine aerogel prepared in Example 3.
[0034] Figure 7 The image shows a scanning electron microscope (SEM) image of the polybenzoxazine aerogel prepared in Example 4.
[0035] Figure 8 The image shows a scanning electron microscope (SEM) image of the polybenzoxazine aerogel prepared in Example 5.
[0036] Figure 9 The graphs show the adsorption effects of the polybenzoxazine aerogels prepared in Examples 1-5 on various heavy metal ions. Detailed Implementation
[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.
[0038] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.
[0039] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.
[0040] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.
[0041] Example 1
[0042] (1) First, weigh 5.4g resorcinol, 2.5g poloxamer F127, 22.8mL anhydrous ethanol and 18mL deionized water into a 100mL three-necked flask. Set the temperature to 25℃, stir for 20min, then add 0.156g hexamethylenediamine and continue stirring for 40min. Then quickly add 8.84g 37% formaldehyde aqueous solution. After 10min, add 0.6g tannic acid dissolved in 2.5mL deionized water and continue the reaction for 3h. Bottle the resulting suspension and let it stand for 24h.
[0043] (2) Pour off the clear liquid on the upper layer of the glass bottle that has been completely settled in step (1), and then cure it according to the curing method of 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h, 90℃ / 3h to obtain polybenzoxazine wet gel.
[0044] (3) Take out the wet gel from step (2) and place it at 50°C for vacuum drying for 24 hours to obtain polybenzoxazine aerogel, denoted as RTH-1.
[0045] Example 2
[0046] (1) First, weigh 6.0g resorcinol, 2.5g poloxamer F127, 22.8mL anhydrous ethanol and 18mL deionized water into a 100mL three-necked flask. Set the temperature to 25℃, stir for 20min, then add 0.2mL triethylenetetramine (1.3mol), continue stirring for 40min, then quickly add 8.84g 37% formaldehyde aqueous solution, continue the reaction for 3h, and bottle the resulting suspension and let it stand for 24h.
[0047] (2) Pour off the clear liquid on the upper layer of the glass bottle that has been completely settled in step (1), and then cure it according to the curing method of 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h, 90℃ / 3h to obtain polybenzoxazine wet gel.
[0048] (3) Take out the wet gel from step (2) and place it at 50°C for vacuum drying for 24 hours to obtain polybenzoxazine aerogel, denoted as RTH-2.
[0049] Example 3
[0050] (1) First, weigh 3.0g resorcinol, 7.8g bisphenol acid, 2.5g poloxamer F127, 22.8mL anhydrous ethanol and 18mL deionized water into a 100mL three-necked flask. Set the temperature to 30℃, stir for 20min, then add 0.2mL triethylenetetramine (1.3mol), continue stirring for 40min, then quickly add 8.84g 37% formaldehyde aqueous solution, continue the reaction at 50℃ for 40min, and bottle the resulting suspension and let it stand for 24h.
[0051] (2) Pour off the clear liquid on the upper layer of the glass bottle that has been completely settled in step (1), and then cure it according to the curing method of 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h, 90℃ / 3h to obtain polybenzoxazine wet gel.
[0052] (3) Take out the wet gel from step (2) and place it at 50°C for vacuum drying for 24 hours to obtain polybenzoxazine aerogel, denoted as RTH-3.
[0053] Example 4
[0054] (1) First, weigh 3.0g resorcinol, 7.8g bisphenol acid, 2.5g poloxamer F127, 22.8mL anhydrous ethanol and 18mL deionized water into a 100mL three-necked flask. Set the temperature to 30℃, stir for 20min, then add 0.254mL tetraethylenepentamine (1.3mol), continue stirring for 40min, then quickly add 8.84g 37% formaldehyde aqueous solution, continue the reaction at 50℃ for 40min, and bottle the resulting suspension and let it stand for 24h.
[0055] (2) Pour off the clear liquid on the upper layer of the glass bottle that has been completely settled in step (1), and then cure it according to the curing method of 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h, 90℃ / 3h to obtain polybenzoxazine wet gel.
[0056] (3) Take out the wet gel from step (2) and place it at 50°C for vacuum drying for 24 hours to obtain polybenzoxazine aerogel, denoted as RTH-4.
[0057] Example 5
[0058] (1) First, weigh 1.1g resorcinol, 2.3g 3-amino-5-mercapto-1,2,4-triazole, 3.2g 37% formaldehyde aqueous solution and 20mL dioxane into a 100mL three-necked flask, stir and dissolve at -10℃, continue the reaction for 1h after complete dissolution, and bottle the resulting suspension and let it stand overnight.
[0059] (2) The sample from step (1) was placed in an oven at 80°C and reacted for 72 hours to obtain a polybenzoxazine aerogel precursor. Then, it was cured at 140°C / 2 hours, 160°C / 2 hours, 180°C / 2 hours, and 200°C / 3 hours to obtain polybenzoxazine aerogel, which was denoted as RTH-5.
[0060] The polybenzoxazine aerogels from Examples 1-5 were immersed in solutions of 800 mg / L FeCl3, K2CrO4, CuCl2, Pb(NO3)2, ZnCl2, and SnCl2, respectively. After adsorption at room temperature for 24 h, the concentration of residual heavy metal ions in the solution was determined by ultraviolet spectrophotometry, and then the heavy metal ion removal rate of the polybenzoxazine aerogel was determined.
[0061] Fe 3+ The determination method is as follows: First, hydroxylamine hydrochloride is used to first... 3+ Reduced to Fe 2+ Then, o-phenanthroline was used as a complexing agent to react with Fe. 2+A stable complex was formed, and its absorbance at 511 nm was measured. The complex contained 0.5% o-phenanthroline (dissolved in a small amount of ethanol before preparation) and 10% hydroxylamine hydrochloride. An 800 mg / L FeCl3 solution was diluted 40 times, and 0 mL, 0.4 mL, 0.8 mL, 1.2 mL, 1.6 mL, and 2 mL of the diluted solution were successively placed into 10 mL centrifuge tubes and labeled 1-6. Then, 0.2 mL of 10% hydroxylamine hydrochloride solution, 0.4 mL of 0.5% o-phenanthroline solution, and an acetate-sodium acetate buffer solution were added to adjust the pH to approximately 6. Finally, deionized water was added to bring the total volume to 10 mL. Samples 2-5 were then adsorbed with polybenzoxazine aerogel for 24 hours. The resulting solutions were diluted 40-fold, and 2 mL of each solution (labeled 7-11) was added to each. 0.2 mL of 10% hydroxylamine hydrochloride solution, 1 mL of HAc-NaAc buffer solution, and 0.4 mL of 0.5% o-phenanthroline solution were added, and finally, deionized water was added to a final volume of 10 mL. After mixing, the absorbance of samples 1-11 at 511 nm was measured using a UV spectrophotometer. A standard curve was plotted using the absorbance of samples 1-6 at 511 nm and their corresponding concentrations. The standard curve was fitted to obtain a linear equation. The absorbance of samples 7-11 at 511 nm was then substituted into the linear equation to calculate the concentration. The removal rate R (mg / g) was then calculated using the following formula:
[0062]
[0063] In equation (1-1): C0—the initial concentration of metal ions in the solution, mg / L;
[0064] C1 — Concentration of metal ions in the solution after 24 hours of adsorption, mg / L;
[0065] m — Mass of polybenzoxazine aerogel, in g;
[0066] v — solution volume, L.
[0067] Cr 6+The determination method is as follows: Dilute 800 mg / L K2CrO4 solution 10 times, and take 0 mL, 0.5 mL, 0.625 mL, 0.75 mL, 0.875 mL, and 1 mL of the diluted solution into 10 mL centrifuge tubes, and label them as 1-6. Add polybenzoxazine aerogel to samples 2-5 for adsorption for 24 h. Dilute the K2CrO4 solutions after adsorption with polybenzoxazine aerogel in the five examples 10 times, and take 1 mL into 10 mL centrifuge tubes, labeling them as 7-11. Add 5 mL of the solution to samples 1-11. The pH was adjusted to approximately 6 using 0.04 mol / L disodium ethylenediaminetetraacetate and acetate-sodium acetate buffer solution. Deionized water was added to bring the volume to 10 mL. The absorbance at 369 nm was measured within 15 min. A standard curve was plotted using the absorbance at 369 nm of samples 1-6 and their corresponding concentrations. The standard curve was fitted to obtain a linear equation. Then, the absorbance at 369 nm of samples 7-11 was substituted into the linear equation to calculate the concentration. The calculation formula is consistent with equation (1-1).
[0068] Cu 2+ The determination method is as follows: Dilute 800 mg / L CuCl2 solution 100 times, and take 0 mL, 2 mL, 2.5 mL, 3 mL, 3.5 mL, and 4 mL of the diluted solution into 10 mL centrifuge tubes, and label them as 1-6. Add polybenzoxazine aerogel to samples 2-5 for adsorption for 24 h. Dilute the CuCl2 solutions after adsorption with polybenzoxazine aerogel in the five examples 100 times, and take 3 mL into 10 mL centrifuge tubes, labeling them as 7-11. Add 4 mL of the solution to samples 1-11. The pH was adjusted to approximately 6 using 0.04 mol / L disodium ethylenediaminetetraacetate and acetate-sodium acetate buffer solution. Deionized water was added to bring the volume to 10 mL. The absorbance at 732 nm was measured within 15 min. A standard curve was plotted using the absorbance at 732 nm of samples 1-6 and their corresponding concentrations. The standard curve was then fitted to obtain a linear equation. The absorbance at 732 nm of samples 7-11 was then substituted into the linear equation to calculate the concentration. The calculation formula is consistent with equation (1-1).
[0069] Pb 2+The determination method is as follows: Dilute 800 mg / L Pb(NO3)2 solution 40 times, and take 0 mL, 1 mL, 1.5 mL, 2 mL, 2.5 mL, and 3 mL of the diluted solution into 10 mL centrifuge tubes, and label them as 1-6. Add polybenzoxazine aerogel to samples 2-5 for adsorption for 24 h. Dilute the Pb(NO3)2 solutions after adsorption by the five types of polybenzoxazine aerogels in the example 40 times, and take 2 mL into 10 mL centrifuge tubes, labeling them as 7-11. Add 0.28 mL of the solution to samples 1-11. The pH was adjusted to approximately 6 using 0.003 mol / L xylenol orange solution and acetic acid-sodium acetate buffer solution. Deionized water was added to bring the volume to 10 mL. The absorbance at 524 nm was measured within 15 min. A standard curve was plotted using the absorbance at 524 nm of samples 1-6 and their corresponding concentrations. The standard curve was fitted to obtain a linear equation. The absorbance at 732 nm of samples 7-11 was then substituted into the linear equation to calculate the concentration. The calculation formula is consistent with equation (1-1).
[0070] Sn 2+ The determination method is as follows: Dilute 800 mg / L SnCl2 solution 8 times, and take 0 mL, 0.375 mL, 0.5 mL, 0.625 mL, 0.75 mL, and 0.875 mL of the diluted solution into 10 mL centrifuge tubes, and label them as 1-6. Add polybenzoxazine aerogel to samples 2-5 for 24 h of adsorption. Dilute the SnCl2 solutions after adsorption with the five types of polybenzoxazine aerogels in the example 8 times, and take 0.75 mL into 10 mL centrifuge tubes, labeling them as 7-11. Add samples 1-11 to the centrifuge tubes. Add 0.28 mL of 0.003 mol / L xylenol orange solution and acetic acid-sodium acetate buffer solution to adjust the pH to about 6. Add deionized water to make up to 10 mL. Measure the absorbance at 490 nm within 15 min. Plot a standard curve using the absorbance at 490 nm of samples 1-6 and their corresponding concentrations. Fit the standard curve to obtain a linear equation. Then substitute the absorbance at 732 nm of samples 7-11 into the linear equation to calculate the concentration. The calculation formula is consistent with equation (1-1).
[0071] The infrared spectra of the polybenzoxazine aerogels prepared in Examples 1-5 are shown below. Figure 1 ,from Figure 1 As can be seen, the vibrational peak of the oxazine ring at 900-960°C disappears, while the absorption vibrational peak of the phenolic hydroxyl group appears, indicating that both curing methods provided by this invention have successfully prepared polybenzoxazine aerogels.
[0072] The TGA test results of the polybenzoxazine aerogels prepared in Examples 1-5 are shown in the figure. Figure 2 ,from Figure 2As can be seen, the weight loss of all five samples was not significant below 250℃, indicating that each sample exhibits good thermal stability in high-temperature environments below 250℃.
[0073] The acid resistance test results of the polybenzoxazine aerogels prepared in Examples 1-5 are shown in the figure. Figure 3 The samples were immersed in strongly acidic solutions with pH=1 and pH=3 for 24 hours, respectively. The effect of the strongly acidic solutions on the samples was compared using the weight loss method, and the reduction rate of sample mass before and after immersion in the strongly acidic solutions was calculated according to formula (1-2). Figure 3 As can be seen, the mass loss of the samples is all within 8%, especially the mass loss rate of the sample in Example 5, which is within 3%, and the samples show good acid resistance.
[0074]
[0075] In formula (1-2): m0 — mass of the sample before immersion in a strong acid solution, g;
[0076] m1 — Mass of the sample after soaking in a strong acid solution for 24 hours, in grams.
[0077] The scanning electron microscope image of the polybenzoxazine aerogel prepared in Example 1 is shown below. Figure 4 .
[0078] The scanning electron microscope image of the polybenzoxazine aerogel prepared in Example 2 is shown below. Figure 5 .
[0079] The scanning electron microscope image of the polybenzoxazine aerogel prepared in Example 3 is shown below. Figure 6 .
[0080] The scanning electron microscope image of the polybenzoxazine aerogel prepared in Example 4 is shown below. Figure 7 .
[0081] The scanning electron microscope image of the polybenzoxazine aerogel prepared in Example 5 is shown below. Figure 8 .
[0082] from Figures 4-8 As can be seen, the polybenzoxazine aerogel prepared by this invention exhibits a porous structure, which greatly increases the specific surface area of the aerogel.
[0083] The adsorption effects of the polybenzoxazine aerogels prepared in Examples 1-5 on various heavy metal ions are shown in the figures. Figure 9 .
[0084] from Figure 9 As can be seen from the above, the polybenzoxazine aerogels prepared in Examples 1-5 exhibit good resistance to Fe. 3+ Cr 6+ Cu 2+ Pb 2+and Sn 2+ All have certain adsorption properties, among which Sn 2+ The adsorption capacity is the largest, which may be due to Sn. 2+ This is due to the largest van der Waals radius; in addition, RTH-4 has the highest adsorption capacity for five heavy metal ions compared to other aerogels, which is due to the introduction of -COOH and more heteroatoms.
[0085] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for preparing an aerogel for the adsorption of heavy metal ions, characterized in that, Includes the following steps: Phenolic compounds, primary amine compounds, formaldehyde and surfactants are mixed in a solvent, and after the reaction, a benzoxazine monomer suspension is obtained. After standing, the upper layer of solution is removed. The remaining part is first solidified in sections to obtain polybenzoxazine wet gel, and then dried to obtain aerogel for heavy metal ion adsorption. The phenolic compounds are resorcinol and bisphenolic acid; The primary amine compound is tetraethylenepentamine; The surfactant is poloxamer F127; The molar ratio of the phenolic compound, surfactant, primary amine compound and formaldehyde is 0.5~41 : 0~19 : 1 : 2~82, and the amount of surfactant is not 0; The curing temperature gradient of the polybenzoxazine wet gel is 40℃ / 30min, 50℃ / 30min, 60℃ / 1h, 70℃ / 1h and 90℃ / 3h respectively; the drying is vacuum drying at 50℃ for 24h.
2. An aerogel for heavy metal ion adsorption prepared by the preparation method of the aerogel for heavy metal ion adsorption according to claim 1.
3. The application of the aerogel for heavy metal ion adsorption as described in claim 2 in the adsorption of heavy metal ions.