Adsorbent of nano aluminum oxide loaded hydrothermal carbon as well as preparation method and application of adsorbent
By using nano-alumina to carry hydrothermal carbon as an adsorbent, the problems of small specific surface area and imperfect pore structure of hydrothermal carbon were solved, achieving efficient adsorption of bisphenol A endocrine disruptors with good adsorption selectivity and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-03-13
AI Technical Summary
When existing hydrothermal carbon is used as an adsorbent, it suffers from limited specific surface area and imperfect pore structure, resulting in low adsorption capacity and mass transfer rate. Furthermore, polyethyleneimine is prone to deactivation during thermal regeneration.
A nano-alumina aerogel was prepared using hydrothermal carbon as an adsorbent via a sol-gel method. This aerogel served as the main carrier and was mixed with wheat straw hydrothermal carbon. Polyethyleneimine was added to form a three-dimensional network structure. The adsorption capacity and stability were enhanced by combining aqueous phase ultrasonic-assisted composite and low-temperature thermal cross-linking.
The specific surface area and pore volume of the adsorbent were increased, enhancing the adsorption selectivity and structural stability for bisphenol A endocrine disruptors, thus achieving efficient adsorption and multiple recycling.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of adsorbent preparation technology, and in particular to an adsorbent consisting of nano-alumina loaded with hydrothermal carbon, its preparation method, and its application. Background Technology
[0002] Bisphenol A (BPA) is a typical endocrine disruptor widely used in the production of polycarbonate plastics and epoxy resins. Even at extremely low concentrations (ng / L-μg / L) in the environment, it can pose potential harm to organisms and ecosystems. Adsorption is considered a promising technology due to its simplicity and relatively low cost. Activated carbon is a commonly used adsorbent, but its selectivity for trace amounts of lipophilic organic pollutants is low, and regeneration is difficult. Hydrothermal carbon, a carbon-rich material prepared from biomass through a hydrothermal process, contains abundant oxygen-containing functional groups (such as carboxyl and hydroxyl groups), exhibiting good affinity for certain organic pollutants, and its raw material sources are widely available and inexpensive. However, the specific surface area of hydrothermal carbon is usually limited, and its pore structure is not fully developed, restricting its adsorption capacity and mass transfer rate. More importantly, when used directly as a carrier for polyethyleneimine (PEI), PEI is prone to ureaization during thermal regeneration, leading to rapid deactivation of the adsorbent.
[0003] Therefore, in order to address the above problems, the present invention urgently needs to provide an adsorbent of nano-alumina loaded with hydrothermal carbon, its preparation method and application. Summary of the Invention
[0004] The purpose of this invention is to provide an adsorbent consisting of nano-alumina and hydrothermal carbon, its preparation method, and its application. The proposed method for preparing the adsorbent consisting of nano-alumina and hydrothermal carbon addresses the limitations of existing technologies where the specific surface area of single hydrothermal carbon is usually limited and the pore structure is not well developed, thus restricting its adsorption capacity and mass transfer rate.
[0005] The present invention provides a method for preparing an adsorbent of nano-alumina loaded with hydrothermal carbon, comprising the following steps:
[0006] The crushed wheat straw and deionized water are mixed and hydrothermally reacted at 180-200℃ for 4-5 hours. After cooling, washing, and drying, wheat straw hydrothermal char is obtained.
[0007] Nano-alumina aerogel and wheat straw hydrothermal char were mixed at a ratio of (1-3):1, deionized water was added, ultrasonically dispersed, and dried to obtain a composite carrier.
[0008] Polyethyleneimine was dissolved in a solvent to obtain an impregnation solution. The composite carrier was added to the impregnation solution, the solvent was evaporated, and the solution was heat-treated at 130-150℃ for 1.5-3 h to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0009] Preferably, the mass ratio of the composite carrier to polyethyleneimine is 1:(0.2-0.4).
[0010] Preferably, polyethyleneimine is dissolved in a solvent to obtain an impregnation solution with a concentration of 10-20 wt%.
[0011] Preferably, the method for preparing nano-alumina aerogel is as follows:
[0012] Using aluminum isopropoxide as the aluminum source and nitric acid as the gel solvent, after a sol-gel process, followed by aging, solvent replacement, and drying at normal pressure, nano-alumina aerogel was obtained by calcination at 400-500℃. The specific surface area of the nano-alumina aerogel was 350-450 m² / g, and the pore volume was 1.2-1.8 cm³ / g.
[0013] Preferably, the molecular weight of polyethyleneimine is 1800-10000 Da; the solvent is water, and the concentration of the impregnation solution is 10-20 wt%.
[0014] Preferably, the wheat straw is washed with deionized water and dried at 105°C before being crushed.
[0015] Preferably, the drying is performed under normal pressure at a temperature of 70-90°C.
[0016] Preferably, the ultrasonic dispersion power is 300-500W, the dispersion time is 30-60min, and the mass ratio of wheat straw to deionized water is 1:(8-12).
[0017] The present invention also provides an adsorbent based on nano-alumina loaded with hydrothermal carbon as described in any one of the above-mentioned methods.
[0018] The present invention also provides an application of an adsorbent based on nano-alumina loaded with hydrothermal carbon as described above for adsorbing ester pollutants in water.
[0019] The hydrothermal carbon-based composite material for adsorbing bisphenol A endocrine disruptors and its preparation method provided by this invention have the following advantages compared with the prior art:
[0020] 1. The method for preparing hydrothermal carbon-based composite material for adsorbing bisphenol A endocrine disruptors provided by the present invention uses nano-alumina aerogel prepared by sol-gel method as the main carrier. Its three-dimensional network structure provides ideal attachment space and mass transfer channels for hydrothermal carbon and polyethyleneimine. The obtained adsorbent can effectively adsorb ester pollutants.
[0021] 2. The preparation method of the hydrothermal carbon-based composite material for adsorbing bisphenol A endocrine disruptors provided by the present invention uses wheat straw as raw material and performs hydrothermal carbonization at a relatively low temperature (180-200℃) to maximize the retention of its cellulose skeleton and oxygen-containing functional groups (-COOH, -OH). These functional groups are key sites for forming hydrogen bonds with phthalate molecules, and are also the basis for subsequent interaction with polyethyleneimine (PEI) and nano-alumina carrier.
[0022] 3. The preparation method of the hydrothermal carbon-based composite material for adsorbing bisphenol A endocrine disruptors provided by the present invention adopts a mild process of aqueous phase ultrasonic-assisted composite and low-temperature thermal crosslinking of polyethyleneimine, which perfectly preserves the surface chemical properties of each component. The introduction of polyethyleneimine and low-temperature crosslinking further enhance the material's specific adsorption capacity for phthalates and its structural stability.
[0023] 4. The preparation method of the hydrothermal carbon-based composite material for adsorbing bisphenol A endocrine disruptors provided by the present invention has a mild preparation process that ensures the complete preservation of the oxygen-containing functional groups of hydrothermal carbon and the amino groups of polyethyleneimine, providing abundant active sites for efficient adsorption of phthalates.
[0024] 5. The method for preparing hydrothermal carbon-based composite materials for adsorbing bisphenol A endocrine disruptors provided by the present invention involves mixing nano-alumina aerogel and wheat straw hydrothermal carbon, ensuring the proportion of nano-alumina aerogel, which can form a complete three-dimensional network to effectively support and disperse the hydrothermal carbon, avoid the aggregation of hydrothermal carbon particles and blockage of pores, ensure the overall specific surface area and pore volume of the composite material, facilitate mass transfer, ensure the effective adsorption sites of the hydrothermal carbon, and ensure the subsequent polyethyleneimine loading. Attached Figure Description
[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0026] Figure 1 This is an image of the appearance of hydrothermal charcoal;
[0027] Figure 2 The adsorption curve of titanate by the adsorbent of nano-alumina loaded with hydrothermal carbon was obtained in Example 1.
[0028] Figure 3 Example 1 shows the adsorption rate of nano-alumina loaded with hydrothermal carbon for different concentrations of titanate esters.
[0029] Figure 4 Example 1 shows the adsorption capacity of nano-alumina loaded with hydrothermal carbon after several cycles. Detailed Implementation
[0030] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] The present invention provides a method for preparing an adsorbent of nano-alumina loaded with hydrothermal carbon, comprising the following steps:
[0032] S1) Mix crushed wheat straw with deionized water and hydrothermally react at 180-200℃ for 4-5 hours. Cool, wash, and dry to obtain wheat straw hydrothermal char.
[0033] S2) Mix nano-alumina aerogel and wheat straw hydrothermal char at a ratio of (1-3):1, add deionized water, ultrasonically disperse, and dry to obtain a composite carrier;
[0034] S3) Dissolve polyethyleneimine in a solvent to obtain an impregnation solution, add the composite carrier to the impregnation solution, evaporate the solvent, and heat treat at 130-150℃ for 1.5-3 h to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0035] Specifically, the mass ratio of the composite carrier to polyethyleneimine is 1:(0.2-0.4).
[0036] Specifically, polyethyleneimine is dissolved in a solvent to obtain an impregnation solution with a concentration of 10-20 wt%.
[0037] Specifically, the preparation method of nano-alumina aerogel is as follows:
[0038] Using aluminum isopropoxide as the aluminum source and nitric acid as the gel solvent, after a sol-gel process, followed by aging, solvent replacement, and drying at normal pressure, nano-alumina aerogel was obtained by calcination at 400-500℃. The specific surface area of the nano-alumina aerogel was 350-450 m² / g, and the pore volume was 1.2-1.8 cm³ / g.
[0039] Specifically, the molecular weight of polyethyleneimine is 1800-10000 Da; the solvent is water, and the concentration of the impregnation solution is 10-20 wt%.
[0040] Specifically, before crushing, the wheat straw is washed with deionized water and dried at 105°C.
[0041] Specifically, the drying process is carried out under normal pressure at a temperature of 70-90℃.
[0042] Specifically, the ultrasonic dispersion power is 300-500W, the dispersion time is 30-60min, and the mass ratio of wheat straw to deionized water is 1:(8-12).
[0043] The present invention also provides an adsorbent based on nano-alumina loaded with hydrothermal carbon as described in any one of the above-mentioned methods.
[0044] The present invention also provides an application of an adsorbent based on nano-alumina loaded with hydrothermal carbon as described above for adsorbing ester pollutants in water.
[0045] This invention uses nano-alumina aerogel prepared by the sol-gel method as the main carrier. Its three-dimensional network structure provides an ideal attachment space and mass transfer channel for hydrothermal carbon and polyethyleneimine. The obtained adsorbent can effectively adsorb ester pollutants.
[0046] This invention uses wheat straw as raw material and performs hydrothermal carbonization at a relatively low temperature (180-200℃) to maximize the retention of its cellulose skeleton and oxygen-containing functional groups (-COOH, -OH). These functional groups are key sites for forming hydrogen bonds with phthalate molecules and are also the basis for subsequent interactions with polyethyleneimine (PEI) and nano-alumina carriers.
[0047] The mild process of aqueous phase ultrasonic-assisted composite and low-temperature thermal crosslinking of polyethyleneimine perfectly preserves the surface chemical properties of each component. The introduction of polyethyleneimine and low-temperature crosslinking further enhance the material's specific adsorption capacity for phthalates and its structural stability.
[0048] The mild preparation process of this invention ensures that the oxygen-containing functional groups of hydrothermal carbon and the amino groups of polyethyleneimine are completely preserved, providing abundant active sites for the efficient adsorption of phthalates.
[0049] In this invention, nano-alumina aerogel and wheat straw hydrothermal char are mixed at a ratio of (1-3):1 to ensure the proportion of nano-alumina aerogel. This mixture can form a complete three-dimensional network to effectively support and disperse the hydrothermal char, preventing the hydrothermal char particles from agglomerating and clogging the pores. This ensures the overall specific surface area and pore volume of the composite material, which is conducive to mass transfer and ensures the effective adsorption sites of the hydrothermal char. At the same time, it also ensures the subsequent polyethyleneimine loading.
[0050] Example 1
[0051] The preparation method of nano-alumina aerogel in this embodiment is as follows:
[0052] Weigh 10g of aluminum isopropoxide, add 100mL of deionized water at 80℃, and add 1M nitric acid dropwise under vigorous stirring until pH=4, forming a transparent sol;
[0053] The sol was sealed and aged at 60°C for 24 hours to form a gel.
[0054] The gel was subjected to three solvent replacements, each 8 hours apart. After replacement, it was dried at 80°C and atmospheric pressure for 24 hours, and then calcined in a muffle furnace at 450°C at a rate of 2°C / min for 2 hours to obtain nano-alumina aerogel. The specific surface area of the nano-alumina aerogel was 400 m² / g, and the pore volume was 1.5 cm³ / g.
[0055] The preparation method of the adsorbent of nano-alumina loaded with hydrothermal carbon in this embodiment includes the following steps:
[0056] 101) Wheat straw was washed with deionized water, dried at 105℃ to constant weight, and pulverized. 10g of pulverized wheat straw was weighed, mixed with 1000mL of deionized water, and subjected to hydrothermal reaction at 180℃ for 5 hours. After cooling, the mixture was washed until neutral and dried at 70℃ for 12 hours to obtain brownish-red wheat straw hydrothermal charcoal with a distinct fibrous structure. Figure 1 As shown;
[0057] 102) Mix nano-alumina aerogel and wheat straw hydrothermal char, with a mass ratio of hydrothermal char to nano-alumina aerogel of 1:1, add 50 mL of deionized water, sonicate at 400 W for 40 min, and dry at 80 °C to obtain a composite carrier.
[0058] 103) Polyethyleneimine (Mw=1800 Da) was dissolved in a solvent to obtain an impregnation solution with a concentration of 10 wt%. The dried composite carrier was added to the impregnation solution with a mass ratio of composite carrier to polyethyleneimine of 1:0.4. The mixture was stirred at room temperature for 6 hours, the solvent was evaporated at 60°C, and the mixture was heat-treated at 130°C under vacuum for 2 hours to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0059] The solvent in this embodiment is water.
[0060] The application of the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment in the adsorption of phthalic acid pollutants in water is as follows: Specifically, simulated wastewater with a concentration of 50 mg / L of dibutyl phthalate (DBP) was prepared. In a 250 mL Erlenmeyer flask, 100 mL of simulated wastewater and 20 mg of the obtained nano-alumina-loaded hydrothermal carbon adsorbent were added. The flask was kept at a constant temperature of 25°C and 150 rpm and shaken. Samples were taken at different time points, filtered through a 0.45 μm filter membrane, and the concentration of DBP in the filtrate was determined by high performance liquid chromatography.
[0061] like Figure 2 As shown, the experimental results are as follows: the saturated adsorption capacity of DBP by the adsorbent of nano-alumina loaded with hydrothermal carbon can reach 600 mg / g.
[0062] Figure 3 Experimental results show that the adsorption of DBP by the nano-alumina-loaded hydrothermal carbon adsorbent increases with increasing DBP concentration, reaching a maximum adsorption capacity of 600 mg / g at a DBP concentration of approximately 200 mg / L.
[0063] After adsorption saturation, the adsorbent was collected and desorbed by shaking with 20 mL of ethanol solution at 25°C for 2 hours. The desorbed adsorbent was then washed, dried, and used for the next adsorption-desorption cycle test.
[0064] like Figure 4 As shown, after 5 adsorption-desorption cycles, the adsorption retention rate of DBP is as high as 90%.
[0065] Example 2
[0066] The only difference between this embodiment and Embodiment 1 is that the mass ratio of hydrothermal carbon to nano-alumina aerogel is 1:3.
[0067] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0068] Example 3
[0069] The only difference between this embodiment and Embodiment 1 is that the mass ratio of hydrothermal carbon to nano-alumina aerogel is 1:2.
[0070] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0071] Example 4
[0072] The preparation method of nano-alumina aerogel in this embodiment is as follows:
[0073] Weigh 10g of aluminum isopropoxide, add 100mL of deionized water at 80℃, and add 1M nitric acid dropwise under vigorous stirring until pH=4, forming a transparent sol;
[0074] The sol was sealed and aged at 60°C for 24 hours to form a gel.
[0075] The gel was subjected to three solvent replacements, each 8 hours apart. After replacement, it was dried at 80°C and atmospheric pressure for 24 hours, and then calcined in a muffle furnace at 400°C at a rate of 2°C / min for 2-3 hours to obtain nano-alumina aerogel. The specific surface area of the nano-alumina aerogel was 450 m² / g, and the pore volume was 1.8 cm³ / g.
[0076] The preparation method of the adsorbent of nano-alumina loaded with hydrothermal carbon in this embodiment includes the following steps:
[0077] 401) Wash wheat straw with deionized water, dry it at 105℃ to constant weight, and crush it; weigh 10g of crushed wheat straw, mix the crushed wheat straw with 1000mL of deionized water, and hydrothermally react at 200℃ for 4 hours. Cool, wash until neutral, and dry at 90℃ for 12 hours to obtain brown wheat straw hydrothermal charcoal with obvious fibrous structure.
[0078] 402) Mix nano-alumina aerogel and wheat straw hydrothermal char, with a mass ratio of hydrothermal char to nano-alumina aerogel of 1:1, add 50 mL of deionized water, sonicate at 400 W for 40 min, and dry at 80 °C to obtain a composite carrier.
[0079] 403) Polyethyleneimine (Mw=2000 Da) was dissolved in a solvent to obtain an impregnation solution with a concentration of 20 wt%. The dried composite carrier was added to the impregnation solution with a mass ratio of composite carrier to polyethyleneimine of 1:0.4. The mixture was stirred at room temperature for 6 hours, the solvent was evaporated at 60 °C, and the mixture was heat-treated at 150 °C under vacuum for 3 hours to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0080] The solvent in this embodiment is water.
[0081] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0082] Example 5
[0083] The preparation method of the adsorbent of nano-alumina loaded with hydrothermal carbon in this embodiment includes the following steps:
[0084] 501) Wheat straw was washed with deionized water, dried at 105℃ to constant weight, and pulverized; 10g of pulverized wheat straw was weighed, and the pulverized wheat straw was mixed with 1000mL of deionized water and hydrothermally reacted at 190℃ for 4 hours. After cooling, it was washed until neutral and dried at 90℃ for 12 hours to obtain brown wheat straw hydrothermal charcoal with obvious fibrous structure.
[0085] 502) Mix nano-alumina aerogel (preparation method is the same as in Example 4) and wheat straw hydrothermal char, with a mass ratio of hydrothermal char to nano-alumina aerogel of 1:1. Add 50 mL of deionized water, sonicate at 400 W power for 40 min, and dry at 80 °C to obtain a composite carrier.
[0086] 503) Polyethyleneimine (Mw=2000 Da) was dissolved in a solvent to obtain an impregnation solution with a concentration of 20 wt%. The dried composite carrier was added to the impregnation solution with a mass ratio of composite carrier to polyethyleneimine of 1:0.4. The mixture was stirred at room temperature for 6 hours, the solvent was evaporated at 60 °C, and the mixture was heat-treated at 140 °C under vacuum for 3 hours to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0087] The solvent in this embodiment is water.
[0088] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0089] Comparative Example 1
[0090] The only difference between this comparative example and Example 1 is that there is no nano-alumina aerogel in step 102.
[0091] The test method for the adsorbent obtained by hydrothermal carbon is the same as that in Example 1, and the test results are shown in Table 1.
[0092] Comparative Example 2
[0093] The only difference between this comparative example and Example 1 is that wheat straw hydrothermal char is not used in step 102.
[0094] The test method for the obtained nano-alumina adsorbent is the same as that in Example 1, and the test results are shown in Table 1.
[0095] Comparative Example 3
[0096] The only difference between this comparative example and Example 1 is that the mass ratio of wheat straw hydrothermal char to nano alumina aerogel in step 102 is 1:0.5.
[0097] The test method for the obtained nano-alumina-loaded hydrothermal carbon adsorbent is the same as that in Example 1, and the test results are shown in Table 1.
[0098] Comparative Example 4
[0099] The difference between this comparative example and Example 1 is that in step 101), the pulverized wheat straw and deionized water are mixed and hydrothermally reacted at 230°C for 4-5 hours. After cooling, washing, and drying, wheat straw hydrothermal char is obtained.
[0100] Comparative Example 5
[0101] The difference between this comparative example and Example 1 lies in step 103), where polyethyleneimine is dissolved in a solvent to obtain an impregnation solution, the composite carrier is added to the impregnation solution, the solvent is evaporated, and the mixture is heat-treated at 120°C for 4 hours to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0102] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0103] Comparative Example 6
[0104] The difference between this comparative example and Example 1 lies in step 103), where polyethyleneimine is dissolved in a solvent to obtain an impregnation solution, the composite carrier is added to the impregnation solution, the solvent is evaporated, and the mixture is heat-treated at 160°C for 4 hours to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
[0105] The specific method for applying the nano-alumina-loaded hydrothermal carbon adsorbent obtained in this embodiment to adsorb ester pollutants in water is the same as in Example 1. The specific test results are shown in Table 1.
[0106] Table 1. Performance test results of adsorbents with nano-alumina and hydrothermal carbon
[0107]
[0108] Compared with Example 1, Comparative Example 1 showed that the maximum adsorption capacity and adsorption capacity retention rate were much lower than those of Example 1. This was mainly because the nano-alumina aerogel was not added, so a three-dimensional network could not be formed to effectively support and disperse the hydrothermal carbon. The surface area was low, the number of exposed active sites was small, and the loaded polyethyleneimine made the prepared adsorbent unable to meet the requirements for use.
[0109] Compared to Example 1, Comparative Example 2, which did not include wheat straw hydrothermal char, had a much lower maximum adsorption capacity and adsorption capacity retention rate than Example 1. This is mainly because the mesoporous structure and abundant functional groups of the hydrothermal char itself provide a large part of the adsorbent's adsorption capacity. Although nano-alumina has a certain specific surface area, the particles are prone to agglomeration, resulting in a decrease in the actual effective surface area. The pore structure is simple, and the adsorption sites are limited.
[0110] Compared to Example 1, Comparative Example 3 showed significantly lower maximum adsorption capacity and adsorption retention rate. The amount of nano-alumina aerogel added was less than 50% of the total amount, indicating insufficient alumina content as the structural framework and main carrier. This insufficient alumina content prevented the formation of a complete and robust three-dimensional network to effectively support and disperse the hydrothermal carbon. This could lead to the aggregation of hydrothermal carbon particles, clogging pores and reducing the overall specific surface area and pore volume of the composite material, hindering mass transfer. It could also bury some effective adsorption sites of the hydrothermal carbon, rendering them unusable. Furthermore, the reduced carrier content would limit the maximum effective loading of polyethyleneimine.
[0111] Compared to Example 1, Comparative Example 4 increased the hydrothermal reaction temperature in step 101 to 230°C, resulting in a lower maximum adsorption capacity and adsorption capacity retention rate than Example 1. Under hydrothermal reaction at 230°C, although the degree of carbonization was deepened, the cellulose and hemicellulose in the straw underwent excessive decomposition and aromatization, leading to a significant loss of oxygen-containing functional groups (such as carboxyl-COOH and hydroxyl-OH) on their surface. These oxygen-containing functional groups are key sites for forming hydrogen bonds with phthalate molecules and are also the basis for subsequent interactions with polyethyleneimine (PEI) and nano-alumina support. The reduction of functional groups will directly lead to a decrease in the adsorbent's inherent affinity for phthalates and a reduction in the overall adsorption capacity.
[0112] Compared to Example 1, Comparative Example 5 modified the heat treatment temperature in step 103 to 130°C. The highest adsorption capacity and adsorption capacity retention rate of the adsorbent were lower than those in Example 1. It can be seen that the heat treatment in step 103 is crucial. If the temperature is too low, the polyethyleneimine mainly exists in the form of physical adsorption and the degree of cross-linking is insufficient. In subsequent adsorption-desorption cycles, especially in the liquid phase environment, it is easy to dissolve and lose, resulting in rapid degradation of the adsorbent performance.
[0113] Compared to Example 1, Comparative Example 6, with a heat treatment temperature of 160°C in step 103, achieved a significantly lower maximum adsorption capacity and adsorption capacity retention rate than Example 1. This indicates that excessively high temperatures can lead to two adverse effects: firstly, the polyethyleneimine molecular chains may undergo excessive cross-linking or even partial thermal decomposition, resulting in a decrease in the density of active amine groups, thereby weakening its specific chemisorption capacity with phthalates; secondly, under aerobic conditions, the oxidation of polyethyleneimine may be accelerated, affecting its long-term stability. A heat treatment condition of 130-150°C effectively achieves cross-linking and curing of polyethyleneimine while maximally preserving its functional amine groups, ensuring the high efficiency and durability of the adsorbent.
[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing an adsorbent of nano-alumina loaded with hydrothermal carbon, characterized in that: Includes the following steps: The crushed wheat straw and deionized water are mixed and hydrothermally reacted at 180-200℃ for 4-5 hours. After cooling, washing, and drying, wheat straw hydrothermal char is obtained. Nano-alumina aerogel and wheat straw hydrothermal char were mixed at a ratio of (1-3):1, deionized water was added, ultrasonically dispersed, and dried to obtain a composite carrier. Polyethyleneimine was dissolved in a solvent to obtain an impregnation solution. The composite carrier was added to the impregnation solution, the solvent was evaporated, and the solution was heat-treated at 130-150℃ for 1.5-3 h to obtain an adsorbent of nano-alumina loaded with hydrothermal carbon.
2. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: The mass ratio of the composite carrier to polyethyleneimine is 1:(0.2-0.4).
3. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: Polyethyleneimine is dissolved in a solvent to obtain an impregnation solution with a concentration of 10-20 wt%.
4. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: The preparation method of nano-alumina aerogel is as follows: Using aluminum isopropoxide as the aluminum source and nitric acid as the gel solvent, after a sol-gel process, followed by aging, solvent replacement, and drying at normal pressure, nano-alumina aerogel was obtained by calcination at 400-500℃. The specific surface area of the nano-alumina aerogel was 350-450 m² / g, and the pore volume was 1.2-1.8 cm³ / g.
5. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: The molecular weight of polyethyleneimine is 1800-10000 Da; the solvent is water, and the concentration of the impregnation solution is 10-20 wt%.
6. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: Before crushing, wheat straw is washed with deionized water and dried at 105℃.
7. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: Drying is carried out under normal pressure at a temperature of 70-90℃.
8. The method for preparing the adsorbent of nano-alumina loaded with hydrothermal carbon according to claim 1, characterized in that: The ultrasonic dispersion power is 300-500W, and the dispersion time is 30-60min; the mass ratio of wheat straw to deionized water is 1:(8-12).
9. An adsorbent based on nano-alumina loaded with hydrothermal carbon as described in any one of claims 1-8.
10. An application of an adsorbent based on nano-alumina loaded with hydrothermal carbon as described in claim 9 for adsorbing ester pollutants in water.