Natural aldehyde-functionalized all-biomass aerogel and preparation method thereof

Abstract

A natural aldehyde-functionalized all-biomass aerogel and a preparation method thereof, the method comprises: (1) dispersing chitosan in a starch-like fiber solution and stirring to obtain a uniform mixed solution; (2) adding genipin as a crosslinking agent to the mixed solution obtained in step (1), heating and stirring for a period of time to obtain an aerogel precursor solution, and allowing the same to stand to undergo crosslinking to obtain a hydrogel; (3) freezing the hydrogel obtained in step (2), and then freeze-drying to obtain an aerogel; (4) soaking the aerogel obtained in step (3) in a natural aldehyde solution for graft modification, then removing and rinsing, and subsequently drying to obtain the aldehyde-functionalized aerogel.

Description

A natural aldehyde functionalized whole-biomass aerogel and a preparation method thereof TECHNICAL FIELD

[0001] The present application belongs to the field of aerogels, and relates to a natural aldehyde functionalized whole-biomass aerogel and a preparation method thereof. BACKGROUND

[0002] Plasticizers are processing aids widely used in polymer materials to improve their processability and plasticity. Phthalate esters (PAEs) are the most commonly used plasticizers (> 85%), with a global annual production of 4.9 million tons. However, PAEs are easily transferred to the environment through non-covalent bonding with the polymer matrix, causing environmental pollution. Numerous studies have shown that PAEs have many hazards to human health. In addition, PAEs can enter food through various pathways, such as environmental pollution leading to food raw material pollution, food processing and food plastic packaging leading to pollution, and non-human addition, etc. Therefore, PAEs have attracted more and more attention worldwide. Previous studies have mainly focused on the toxicity and detection of PAEs, and the development of efficient PAEs removal technology has become a research hotspot in recent years.

[0003] Adsorption, advanced oxidation processes, and biological treatment are effective technologies for removing PAEs. Among various treatment methods, adsorption is superior to other methods due to its clean operation. In addition, the industrialization of the adsorption process does not require large factories. Therefore, compared with advanced oxidation processes and biological treatment, non-destructive technologies such as adsorption are more attractive from both environmental protection and economic efficiency aspects.

[0004] Aerogels are a class of three-dimensional materials with open, porous, and air-filled structures, which have low density, high porosity, and large specific surface area, making them very suitable for use as adsorbents. Considering economic factors and safety issues, biopolymer composite aerogels (polysaccharides and proteins) have become ideal candidates for water purification, mainly due to their non-toxicity, low cost, abundant reserves, wide sources, biodegradability, and unique characteristics such as biocompatibility and usability. SUMMARY TECHNICAL PROBLEM

[0005] Phthalates have many hazards to human health, but due to their wide range of applications, they can enter food processing through various pathways, causing immeasurable effects. Adsorption is an excellent solution due to its convenience and efficiency, so it is necessary to develop an adsorbent material suitable for removing phthalates.

[0006] TECHNICAL SCHEME

[0007] The application selects chitosan and whey protein isolate amyloid fibril as the adsorption material, and produces aerogel with excellent mechanical properties, structural stability and high PAEs affinity through a simple and safe preparation process.

[0008] The application also uses natural biological crosslinker genipin to prepare chitosan-whey protein isolate amyloid fibril covalent network, so as to improve the mechanical properties and structural stability of the aerogel, and ensure the safety of the aerogel. In addition, natural aldehyde is grafted through Schiff base covalent action, so as to improve the mechanical properties of the chitosan-whey protein isolate amyloid fibril composite aerogel and the affinity to PAEs. In order to obtain satisfactory removal efficiency, the effects of two kinds of aromatic aldehydes and three kinds of fatty aldehydes with different chain lengths or degrees of saturation on improving the removal efficiency of PAEs are studied.

[0009] The application provides a preparation method of natural aldehyde functionalized full-biomass aerogel, which comprises the following steps:

[0010] (1) dispersing chitosan in an amyloid fibril solution to obtain a uniform mixed solution through stirring;

[0011] (2) adding genipin as a crosslinking agent into the mixed solution obtained in step (1), and stirring for a period of time to obtain an aerogel precursor solution, and then standing and crosslinking to obtain a hydrogel;

[0012] (3) freezing the hydrogel obtained in step (2), and then freeze-drying to obtain an aerogel;

[0013] (4) immersing the aerogel obtained in step (3) in a natural aldehyde solution for graft modification, then taking out and eluting, and then drying to obtain an aldehyde functionalized aerogel.

[0014] In an embodiment of the application, the preparation method of the amyloid fibril solution in step (1) comprises the following steps:

[0015] S1, purification of whey protein isolate: taking protein powder into water, stirring to obtain a protein dispersion, then adjusting the pH of the protein dispersion to 4-5, then centrifuging to take supernatant, then passing the supernatant through a 0.4-0.5 μm water filter membrane, and finally freeze-drying the obtained filtrate to obtain purified protein;

[0016] S2, preparation of amyloid fibril solution: dispersing the purified protein powder in water, stirring to obtain a protein solution, then adjusting the pH of the protein solution to 2-2.5, and then stirring to obtain a whey protein isolate amyloid fibril solution.

[0017] Further, the protein powder in step S1 is one of soybean protein isolate, whey protein isolate and lysozyme.

[0018] Preferably, the protein powder in step S1 is whey protein isolate.

[0019] Further, the protein powder concentration of the protein dispersion in step S1 is 5-15 wt%.

[0020] Further, the stirring in step S1 is at a speed of 100-1000 rpm for 8-12 h.

[0021] Further, the centrifugation in step S1 is at 8000-10000 x g for 20-30 min.

[0022] Further, the purified protein powder concentration of the protein solution in step S2 is 1-5 wt%.

[0023] Further, the stirring in step S2 is at a speed of 100-1000 rpm at 70-90℃ for 8-12 h.

[0024] In one embodiment of the present application, the concentration of amyloid fibrils in the amyloid fibril solution in step (1) is 1-1.25% (w / v).

[0025] In one embodiment of the present application, the amyloid fibril solution in step (1) further contains 1-2 wt% acetic acid.

[0026] In one embodiment of the present application, the mass ratio of chitosan to amyloid fibrils in step (1) is 1.5-2.5:1.

[0027] In one embodiment of the present application, the genipin is added in the form of a genipin ethanol solution in step (2); the concentration of genipin in the genipin ethanol solution is 5-15% (w / v).

[0028] In one embodiment of the present application, the ratio of the mass of genipin added in step (2) to the mass of chitosan in step (1) is 1:15-25.

[0029] In one embodiment of the present application, the heating temperature in step (2) is 45-55℃.

[0030] In one embodiment of the present application, the heating time in step (2) is 15-30 min.

[0031] In one embodiment of the present application, the temperature for standing for crosslinking in step (2) is 20-25℃.

[0032] In one embodiment of the present application, the time for standing for crosslinking in step (2) is 24-32 h.

[0033] In an embodiment of the present application, the temperature for freezing in step (3) is -20 to -10 DEG C, and the time is 15 to 30 hours.

[0034] In an embodiment of the present application, the pressure for freeze-drying in step (3) is 1 to 10 pa, the temperature is -50 to -60 DEG C, and the time is 60 to 72 hours.

[0035] In an embodiment of the present application, the natural aldehyde in step (4) includes one or more of citral, citronellal, cinnamaldehyde, p-anisaldehyde, and trans-2-hexenal.

[0036] Preferably, the natural aldehyde in step (4) is citral.

[0037] In an embodiment of the present application, the solvent for the natural aldehyde solution in step (4) is anhydrous ethanol, and the concentration of the natural aldehyde in the natural aldehyde solution is 1.5 to 1.75% (w / v).

[0038] In an embodiment of the present application, the temperature for graft modification in step (4) is 60 to 70 DEG C, and the time is 10 to 12 hours.

[0039] In an embodiment of the present application, the elution in step (4) is elution using anhydrous ethanol.

[0040] The present application provides a natural aldehyde functionalized full-biomass aerogel prepared according to the above method.

[0041] The natural aldehyde functionalized full-biomass aerogel provided by the present application is applied in the field of environmental protection or food processing.

[0042] Compared with the prior art, the present application has the following beneficial effects:

[0043] 1. The present application first prepares a chitosan-starch-like fiber covalent network aerogel using a natural crosslinking agent, which has excellent mechanical properties, structural stability and high safety.

[0044] 2. The present application produces an aerogel with excellent mechanical properties, structural stability and high affinity for DBP through a simple preparation process. The materials used for the gel are chitosan and whey protein isolate, which have the advantages of non-toxicity, low cost, abundant reserves, environmental protection and biodegradability. Natural aldehyde is used as a modifier, which has the advantages of non-toxicity and antibacterial properties, and has great application value for industrial production.

[0045] 3. The aerogel prepared by the present application has high safety and high affinity for PAEs, and can be applied to the removal of PAEs, especially for the food industry. BRIEF DESCRIPTION OF DRAWINGS

[0046] FIG. 1: Stress-strain curve of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 1-5.

[0047] FIG. 2: Dibutyl phthalate removal efficiency of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 1-5.

[0048] FIG. 3: Appearance of the chitosan-starch-like fiber aerogel in Example 5.

[0049] FIG. 4: Scanning electron microscope image of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Example 5.

[0050] FIG. 5: Dibutyl phthalate removal efficiency (a) and scanning electron microscope (b) image of the chitosan-starch-like fiber aerogel in Comparative Example 2 and Example 5.

[0051] FIG. 6: Citral grafting amount of the chitosan-starch-like fiber aerogel in Examples 6-10.

[0052] FIG. 7: Stress-strain curve of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 6-10.

[0053] FIG. 8: Water contact angle of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 6-10.

[0054] FIG. 9: Swelling ratio of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 6-10.

[0055] FIG. 10: Thermal stability of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 6-10.

[0056] FIG. 11: Dibutyl phthalate removal efficiency of the chitosan-starch-like fiber aerogel in Comparative Example 1 and Examples 6-10.

[0057] FIG. 12: Multiple phthalate removal efficiency of the chitosan-starch-like fiber aerogel in Example 8. DETAILED DESCRIPTION

[0058] In order to make the objects, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be described clearly and completely below in connection with specific examples. Obviously, the described examples are some, but not all, of the embodiments of the present application. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0059] In each of the following examples, the preparation method of the whey protein isolate starch-like fiber is as follows:

[0060] First, the purification of whey protein isolate was performed. Briefly, 10 g of whey protein isolate powder was added into 100 mL of deionized water. Then the mixture was stirred overnight at 600 rpm using a magnetic stirrer to allow the protein to be fully hydrated. The resulting protein dispersion was then adjusted to pH 4.75 and centrifuged at 10,000 x g for 30 min to remove any insoluble materials. The supernatant was then passed through a 0.45 pm water filter to remove any residual insoluble proteins. Finally, the purified whey protein isolate was obtained by vacuum freeze-drying.

[0061] For amyloid fibril preparation, 2 g of the purified whey protein isolate powder was dispersed in 100 mL of deionized water and stirred overnight to allow the protein to be fully hydrated. The resulting protein solution was then adjusted to pH 2.0 and stirred at 300 rpm in a 90 °C water bath for 8 h to promote the formation of protein fibrils. Finally, the fibrillation reaction was terminated by cooling in an ice water bath for at least 30 min to obtain a whey protein isolate amyloid fibril solution (2%, w / v).

[0062] Example 1

[0063] Step 1 : 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid fibril solution (containing 1% acetic acid) with a concentration of 1% (w / v) and stirred until completely dissolved to obtain a uniform mixed solution.

[0064] Step 2: 0.4 mL of genipin ethanol solution (10% (w / v)) was added to the mixed solution obtained in Step 1 as a crosslinking agent, and the mixture was stirred at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The solution was left to stand at room temperature for 24 h to promote crosslinking, and a hydrogel was obtained.

[0065] Step 3: The hydrogel obtained in Step 2 was frozen in a -18 °C refrigerator for 24 h and vacuum freeze-dried for 60 h to obtain an aerogel.

[0066] Step 4: The aerogel obtained in Step 3 was soaked in a cinnamon aldehyde ethanol solution with a concentration of 1.5% (w / v) and incubated at 65 °C for 10 h for graft modification. Then the aerogel was thoroughly rinsed with anhydrous ethanol and dried in a fume hood for 24 h to obtain a cinnamon aldehyde functionalized chitosan-whey protein isolate amyloid fibril aerogel.

[0067] Example 2

[0068] Step 1 : 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid fibril solution (containing 1% acetic acid) with a concentration of 1% (w / v) and stirred until completely dissolved to obtain a uniform mixed solution.

[0069] Step 2: To the mixed solution obtained in Step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirred at 50 °C, 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0070] Step 3: The hydrogel obtained in Step 2 was frozen in a -18 °C refrigerator for 24 h, and vacuum freeze-dried for 60 h to obtain an aerogel.

[0071] Step 4: The aerogel obtained in Step 3 was soaked in a p-anisaldehyde ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then it was taken out and rinsed thoroughly with absolute ethanol, and dried in a fume hood for 24 h to obtain a p-anisaldehyde functionalized chitosan-whey protein isolate amyloid aerogel.

[0072] Example 3

[0073] Step 1: 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirred until completely dissolved to obtain a uniform mixed solution.

[0074] Step 2: To the mixed solution obtained in Step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirred at 50 °C, 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0075] Step 3: The hydrogel obtained in Step 2 was frozen in a -18 °C refrigerator for 24 h, and vacuum freeze-dried for 60 h to obtain an aerogel.

[0076] Step 4: The aerogel obtained in Step 3 was soaked in a p-anisaldehyde ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then it was taken out and rinsed thoroughly with absolute ethanol, and dried in a fume hood for 24 h to obtain a p-anisaldehyde functionalized chitosan-whey protein isolate amyloid aerogel.

[0077] Example 4

[0078] Step 1: 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirred until completely dissolved to obtain a uniform mixed solution.

[0079] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0080] Step 3: The hydrogel obtained in step 2 was frozen in a refrigerator at -18 °C for 24 h, and vacuum freeze-drying was performed for 60 h to obtain an aerogel.

[0081] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then, the aerogel was taken out, rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral-functionalized chitosan-whey protein isolate amyloid aerogel.

[0082] Example 5

[0083] Step 1: 0.8 g of chitosan was dispersed in 40 mL of a whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirring was performed until complete dissolution to obtain a uniform mixed solution.

[0084] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0085] Step 3: The hydrogel obtained in step 2 was frozen in a refrigerator at -18 °C for 24 h, and vacuum freeze-drying was performed for 60 h to obtain an aerogel.

[0086] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then, the aerogel was taken out, rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral-functionalized chitosan-whey protein isolate amyloid aerogel.

[0087] Comparative Example 1

[0088] Step 1: 0.8 g of chitosan was dispersed in 40 mL of a whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirring was performed until complete dissolution to obtain a uniform mixed solution.

[0089] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0090] Step 3: The hydrogel obtained in step 2 was frozen in a -18 °C refrigerator for 24 h and vacuum freeze-dried for 60 h to obtain the aerogel without natural aldehyde grafting.

[0091] Comparative Example 2

[0092] Step 1: 1.2 g of chitosan was dispersed in 40 mL of deionized water (containing 1% acetic acid) and stirred until completely dissolved to obtain a uniform mixed solution.

[0093] Step 2: 0.4 mL of genipin ethanol solution (10% (w / v)) was added to the mixed solution obtained in step 1 as a crosslinking agent, and stirred at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The solution was left to stand at room temperature for 24 h to promote crosslinking, and a hydrogel was obtained.

[0094] Step 3: The hydrogel obtained in step 2 was frozen in a -18 °C refrigerator for 24 h and vacuum freeze-dried for 60 h to obtain the aerogel.

[0095] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.5% (w / v) for grafting modification at 65 °C for 10 h. Then it was taken out and rinsed thoroughly with anhydrous ethanol, and dried in a fume hood for 24 h to obtain the aldehyde-functionalized chitosan aerogel.

[0096] Detection process:

[0097] 0.8 g of the aerogel samples of Comparative Example 1 and Examples 1-5 were respectively placed in 100 mL of DBP solution (2 mg / L), and then placed on a shaker to shake at 120 rpm at 25 °C until adsorption equilibrium. Then the aerogel was taken out and the residual concentration of DBP was detected by gas chromatography-mass spectrometry.

[0098] Detection results:

[0099] Figure 1 shows the stress-strain curves of the chitosan-starch-like fiber aerogels in Comparative Example 1 and Examples 1-5. It can be seen that all the aerogels have good mechanical properties. The maximum compressive strength of the aerogel in Comparative Example 1 without aldehyde modification is still up to 595 Kpa, which is attributed to their covalent gel network. The mechanical properties of the aerogels in Examples 1-5 are further improved after aldehyde modification, showing higher stress under the same strain, indicating the enhancement of mechanical strength. Among them, the aerogel in Example 5 shows the best mechanical properties, indicating that citral grafting is an effective strategy to improve chitosan-starch-like fiber aerogels, which may be attributed to its good compatibility with the material matrix.

[0100] Figure 2 shows the DBP removal efficiency of the chitosan-starch-like fibril aerogels in Comparative Example 1 and Examples 1-5. It can be seen that the chitosan-starch-like fibril aerogel in Comparative Example 1 has the lowest DBP removal efficiency, which can be attributed to its lower DBP affinity. The DBP removal efficiency of the aerogels in Examples 1-5 is significantly improved after grafting with natural aldehydes, which can be mainly attributed to the hydrophobic interaction and π-π stacking between the natural aldehyde molecules and DBP. In addition, the aerogels in Examples 3-5 have higher DBP removal capacity compared to Examples 1-2, which indicates that the stronger hydrophobic interaction between the straight-chain aldehyde and DBP is the key to high removal efficiency, rather than the π-π stacking of aromatic aldehyde. The increasing trend of the removal efficiency of the aerogels in Examples 3-5 indicates that the increase of the length of the straight-chain aldehyde and the increase of the unsaturation degree can also promote the adsorption of DBP.

[0101] Figure 3 shows the appearance of the chitosan-starch-like fibril aerogel in Example 5. It can be seen that the prepared aerogel can be stably stood on a dandelion without destroying its structure, which indicates that it has the characteristics of low density and high porosity, which is suitable for application in the field of adsorption.

[0102] Figure 4 shows the scanning electron micrographs of the chitosan-starch-like fibril aerogels in Comparative Example 1 and Example 5. It can be seen that the aerogel in Comparative Example 1 has randomly distributed irregular large pores and honeycomb-like macroporous structures, which are caused by large ice crystals formed during the freezing process at -18°C. The porous structure provides abundant active sites for the adsorption of pollutant molecules. The aerogel in Example 5 retains the original honeycomb-like macroporous structure after grafting with citral, which indicates that the aerogel has good structural stability and can resist environmental drying during the modification process. In addition, compared with the aerogel in Comparative Example 1, the network structure of the aerogel in Example 5 becomes denser, which is beneficial to the adsorption application. More importantly, the pore wall of the aerogel in Example 5 is thicker than that in Comparative Example 1, which indicates that the grafting of citral increases the thickness of the aerogel pore wall, which can improve the mechanical properties and stability of the aerogel by creating a more robust porous structure.

[0103] Figure 5 shows the DBP removal efficiency (a) and scanning electron micrograph (b) of the chitosan-starch-like fibril aerogels in Comparative Example 2 and Example 5. It can be seen from Figure 5a that the chitosan aerogel in Comparative Example 2 has a lower removal efficiency compared to Example 5, which indicates the positive role of the starch-like fibrils in DBP removal. It can be seen from Figure 5b that the aerogel in Comparative Example 2 has a similar pore structure to the aerogel in Example 5, however, its pore wall surface is smooth and no fibrous material is attached, which indicates that the starch-like fibrils are attached to the surface of the aerogel, which increases the roughness and provides a large number of adsorption sites, which is the key to improving the removal efficiency.

[0104] Example 6

[0105] Step 1: 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid fibril solution (containing 1% acetic acid) with a concentration of 1% (w / v), stirred until completely dissolved to obtain a uniform mixed solution.

[0106] Step 2: 0.4 mL of genipin ethanol solution (10% (w / v)) was added to the mixed solution obtained in step 1 as a crosslinking agent, stirred at 50°C, 300 rpm for 20 min to obtain a uniform aerogel precursor solution, and then placed at room temperature for 24 h to promote crosslinking to obtain a hydrogel.

[0107] Step 3: The hydrogel obtained in step 2 was frozen in a -18°C refrigerator for 24 h, and vacuum freeze-dried for 60 h to obtain an aerogel.

[0108] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 0.5% (w / v) for graft modification at 65°C for 10 h, then taken out and rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral functionalized chitosan-whey protein isolate amyloid fibril aerogel.

[0109] Example 7

[0110] Step 1: 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid fibril solution (containing 1% acetic acid) with a concentration of 1% (w / v), stirred until completely dissolved to obtain a uniform mixed solution.

[0111] Step 2: 0.4 mL of genipin ethanol solution (10% (w / v)) was added to the mixed solution obtained in step 1 as a crosslinking agent, stirred at 50°C, 300 rpm for 20 min to obtain a uniform aerogel precursor solution, and then placed at room temperature for 24 h to promote crosslinking to obtain a hydrogel.

[0112] Step 3: The hydrogel obtained in step 2 was frozen in a -18°C refrigerator for 24 h, and vacuum freeze-dried for 60 h to obtain an aerogel.

[0113] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.0% (w / v) for graft modification at 65°C for 10 h, then taken out and rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral functionalized chitosan-whey protein isolate amyloid fibril aerogel.

[0114] Example 8

[0115] Step 1: 0.8 g of chitosan was dispersed in 40 mL of whey protein isolate amyloid fibril solution (containing 1% acetic acid) with a concentration of 1% (w / v), stirred until completely dissolved to obtain a uniform mixed solution.

[0116] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0117] Step 3: The hydrogel obtained in step 2 was frozen in a refrigerator at -18 °C for 24 h, and vacuum freeze-drying was performed for 60 h to obtain an aerogel.

[0118] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then, the aerogel was taken out, rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral functionalized chitosan-whey protein isolate amyloid aerogel.

[0119] Example 9

[0120] Step 1: 0.8 g of chitosan was dispersed in 40 mL of a whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirring was performed until complete dissolution to obtain a uniform mixed solution.

[0121] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0122] Step 3: The hydrogel obtained in step 2 was frozen in a refrigerator at -18 °C for 24 h, and vacuum freeze-drying was performed for 60 h to obtain an aerogel.

[0123] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 1.5% (w / v) for graft modification at 65 °C for 10 h. Then, the aerogel was taken out, rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral functionalized chitosan-whey protein isolate amyloid aerogel.

[0124] Example 10

[0125] Step 1: 0.8 g of chitosan was dispersed in 40 mL of a whey protein isolate amyloid solution (containing 1% acetic acid) with a concentration of 1% (w / v), and stirring was performed until complete dissolution to obtain a uniform mixed solution.

[0126] Step 2: To the mixed solution obtained in step 1, 0.4 mL of genipin ethanol solution (10% (w / v)) was added as a crosslinking agent, and stirring was performed at 50 °C and 300 rpm for 20 min to obtain a uniform aerogel precursor solution. The crosslinking was promoted by standing at room temperature for 24 h to obtain a hydrogel.

[0127] Step 3: The hydrogel obtained in step 2 was frozen in a -18 °C refrigerator for 24 h and vacuum freeze-dried for 60 h to obtain an aerogel.

[0128] Step 4: The aerogel obtained in step 3 was soaked in a citral ethanol solution with a concentration of 3.0% (w / v) for 10 h at 65 °C for grafting modification, then taken out and rinsed with absolute ethanol, and dried in a fume hood for 24 h to obtain a citral functionalized chitosan-whey protein isolate amyloid aerogel.

[0129] Detection process:

[0130] 0.8 g of the aerogel samples of Comparative Example 1 and Examples 6-10 were respectively placed in 100 mL of PAEs solution (2 mg / L), and then placed on a shaker to shake at 120 rpm at 25 °C until adsorption equilibrium. Then the aerogels were taken out and the residual concentration of PAEs was detected by gas chromatography-mass spectrometry.

[0131] Detection results:

[0132] Figure 6 shows the amount of citral grafting of the chitosan-amyloid aerogels in Examples 6-10, and it can be seen that the amount of citral grafting increases linearly with the increase of the concentration of citral, and the highest reaches 0.31 g / g, indicating that the chitosan-amyloid aerogel surface contains a large number of active amino groups as citral grafting sites.

[0133] Figure 7 shows the stress-strain curves of the chitosan-amyloid aerogels in Comparative Example 1 and Examples 6-10, and it can be seen that all the aerogels have good mechanical properties, which may be related to their honeycomb pore wall structure. The compressive strength of the chitosan-amyloid aerogel in Comparative Example 1 is the smallest. With the increase of the concentration of citral, the compressive stress of the aerogel gradually increases. The maximum compressive strength of the aerogel increases from 595 KPa in Comparative Example 1 to 1005 KPa in Example 10, increasing by 68.9%. This confirms that citral grafting can further improve the mechanical properties of the chitosan-amyloid aerogel. The increase in the density of the chitosan-amyloid aerogel and the increase in the cell wall thickness caused by citral grafting may be the main contributors to this event. It is worth noting that when the concentration of citral exceeds 2% (w / v), the compressive stress of the aerogel does not increase significantly, indicating the limited ability of citral to improve the mechanical properties of the material.

[0134] Figure 8 shows the water contact angle (WCA) of the chitosan-starch-like aerogels in Comparative Example 1 and Examples 6-10. It can be seen that the chitosan-starch-like aerogel in Comparative Example 1 has a water contact angle of 0°, mainly due to the presence of a large number of hydrophilic groups in its network. After citral grafting, the water contact angle of the aerogels increases significantly (67.0-121.9°), which can be attributed to the anchoring of low-polarity groups (alkyl chains) on the surface of the chitosan-starch-like aerogel and the consumption of hydrophilic amino groups, while indicating the successful grafting of citral. When the concentration of citral is less than 1.5%, the water contact angle of the chitosan-starch-like aerogels in Examples 6-7 does not exceed 90°, still showing hydrophilicity, which can be attributed to the lower grafting density of citral, and the original hydrophilic groups still dominate. With the further increase of the concentration of citral, the WCA of the aerogel in Example 5 reaches 121.9°, indicating a higher grafting density of citral.

[0135] Figure 9 shows the swelling ratio of the chitosan-starch-like aerogels in Comparative Example 1 and Examples 6-10. It can be seen that the chitosan-starch-like aerogel in Comparative Example 1 has the highest water swelling ratio of 26.42 g / g, which is due to the large number of hydrophilic groups in the aerogel holding water molecules in its network structure through hydrogen bonding. However, the volume of the aerogel does not change significantly before and after water absorption, and the structure remains stable. After citral grafting, the swelling ratio of the chitosan-starch-like aerogels in Examples 6-10 is greatly reduced, and the aerogel in Example 10 has a swelling ratio as low as 7.81 g / g, less than 30% of the aerogel in Comparative Example 1, indicating good structural stability in water. And with the increase of the grafting rate of citral, this change is more significant. This can be attributed to the fact that the low-polarity alkyl chains hinder the diffusion of water into the interior of the aerogel. Another possible reason is that citral grafting can make the aerogel have higher rigidity, which limits the deformability of the polymer network, thereby reducing the water swelling ratio.

[0136] Figure 10 shows the thermal stability of the chitosan-starch-like aerogels in Comparative Example 1 and Examples 6-10. It can be seen that the weight loss process of the chitosan-starch-like aerogel in Comparative Example 1 mainly consists of three steps. The first step occurs in the temperature range of 30-218 °C with a weight loss of 22.09%, which is related to the strong hydrophilicity of the aerogel in Comparative Example 1. The first step can be divided into two stages: the first stage (30-120 °C) is attributed to the loss of free water and water connected by hydrogen bonds in the sample; the second stage is attributed to the release of water more tightly connected by polar interactions with carboxylic acid groups. The second step occurs in the temperature range of 218-300 °C with a weight loss of 22.51%, which can be attributed to the depolymerization of the polymer network structure, decomposition of hydroxyl groups and deacetylation of chitosan. The next weight loss of 29.41% occurs between 300-500 °C, which corresponds to the carbonization of proteins and polysaccharides. Compared with the aerogel in Comparative Example 1, the aerogels in Examples 6-10 have a water loss of 8.73-11.87% between 30-120 °C, depending on the concentration of citral, which is significantly lower than the water loss of the aerogel sample in Comparative Example 1. This can be related to the good hydrophobic properties of the aldehyde-functionalized chitosan-starch-like aerogels, and with the increase of the concentration of citral, the hydrophobicity is enhanced, resulting in the reduction of residual water on the surface and inside of the aerogels. This is consistent with the results of the contact angle analysis. In Figure 10b, it can be observed that the initial decomposition temperature of the aerogels in Examples 6-10 is about 185 °C, which is lower than 218 °C of the aerogel in Comparative Example 1, indicating that citral grafting leads to a slight weakening of the thermal stability of the aerogels. Nevertheless, the aerogel samples in Examples 6-10 can still remain stable at temperatures up to nearly 200 °C.

[0137] Figure 11 shows the dibutyl phthalate removal efficiency of the chitosan-starch-like aerogels in Comparative Example 1 and Examples 6-10. It can be seen that the aerogel in Comparative Example 1 has the lowest dibutyl phthalate removal efficiency, which can be attributed to the weaker hydrophobic interactions, indicating that citral grafting is an effective strategy to improve the affinity of PAEs. The aerogels in Examples 6-10 show different removal efficiencies for dibutyl phthalate, among which Example 8 has the highest removal efficiency, which can be attributed to its higher amount of citral grafting and suitable hydrophobic properties.

[0138] Figure 12 shows the different PAEs removal efficiencies of the chitosan-starch-like aerogel in Example 8. It can be seen that due to the abundant functional groups on the surface of the aerogel and a large number of adsorption sites, as well as the high affinity of PAEs caused by citral grafting, the aerogel can adsorb PAEs through hydrogen bonds, Π-Π stacking and hydrophobic interactions, showing good removal efficiency for dibutyl phthalate, diisobutyl phthalate, dipentyl phthalate, dihexyl phthalate, dioctyl phthalate, di(2-ethylhexyl) phthalate and butyl benzyl phthalate.

[0139] The above embodiments are not intended to limit the scope of the present application, nor are the steps described intended to limit the order in which they are performed. Those skilled in the art will recognize that modifications to the embodiments described are apparent and fall within the scope of the claims of the present application.

Claims

1. A process for the preparation of natural aldehyde functionalized whole biomass aerogels, characterized by, The method comprises the following steps: (1) dispersing chitosan in amyloid fiber solution to obtain a uniform mixed solution by stirring; (2) adding genipin as a crosslinking agent to the mixed solution obtained in step (1) and stirring under heating for a period of time to obtain an aerogel precursor solution, and then allowing the solution to stand for crosslinking to obtain a hydrogel; (3) freezing the hydrogel obtained in step (2) and then freeze-drying to obtain an aerogel; (4) immersing the aerogel obtained in step (3) in a natural aldehyde solution for graft modification, then taking out and eluting, and then drying to obtain an aldehyde-functionalized aerogel.

2. The preparation method according to claim 1, characterized in that, The method for preparing the amyloid fiber in step (1) comprises the following steps: S1, purification of whey protein isolate: adding protein powder to water and stirring to obtain a protein dispersion, then adjusting the pH of the protein dispersion to 4-5, then centrifuging to obtain supernatant, then passing the supernatant through a 0.4-0.5 μm water-based filter membrane, and finally freeze-drying the obtained filtrate to obtain purified protein; S2, preparation of amyloid fiber: dispersing the purified protein powder in water and stirring to obtain a protein solution, then adjusting the pH of the protein solution to 2-2.5, then stirring and drying to obtain whey protein isolate amyloid fiber.

3. The preparation method according to claim 2, characterized in that, The protein powder in step S1 is whey protein isolate.

4. The method of claim 2, wherein the step of forming the first and second layers is performed by a method comprising: In step S1, the protein powder concentration of the protein dispersion is 5-15 wt%; the stirring is stirring at a speed of 100-1000 rpm for 8-12 h; and the centrifugation is centrifugation at 8000-10000 x g for 20-30 minutes.

5. The preparation method according to claim 2, characterized in that, In step S2, the purified protein powder concentration of the protein solution is 1-5 wt%; and the stirring is stirring at a speed of 100-1000 rpm at 70-90℃ for 8-12 h.

6. The preparation method according to claim 1, characterized in that, In step (1), the concentration of amyloid fiber in the amyloid fiber solution is 1-1.25%, w / v; and the amyloid fiber solution contains 1-2 wt% acetic acid.

7. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of chitosan to amyloid fiber is 1.5-2.5:

1.

8. The preparation method according to claim 1, characterized in that, In step (2), the genipin is added in the form of a genipin ethanol solution; the concentration of genipin in the genipin ethanol solution is 5-15%, w / v; and the mass ratio of the amount of genipin added to the mass of chitosan in step (1) is 1:15-25.

9. The method of claim 1, wherein the method further comprises the step of: In step (2), the heating temperature is 45-55℃; the heating time is 15-30 min; the temperature for standing for crosslinking is 20-25℃; and the time for standing for crosslinking is 24-32 h.

10. The method of claim 1, wherein the method further comprises the step of: In step (3), the freezing temperature is -20 to -10℃, and the time is 15-30 h.

11. The method of claim 1, wherein the method further comprises the step of: In step (3), the freeze-drying pressure is 1-10 pa, the temperature is -50 to -60℃, and the time is 60-72 h.

12. The method of claim 1, wherein the method further comprises the step of: In step (4), the natural aldehyde includes one or more of citral, citronellal, cinnamyl aldehyde, p-anisaldehyde, and trans-2-hexenal.

13. The method of claim 1, wherein the method further comprises the step of: In step (4), the natural aldehyde is citral.

14. The method of claim 1, wherein the method further comprises the step of: In step (4), the solvent of the natural aldehyde solution is anhydrous ethanol; and the concentration of the natural aldehyde in the natural aldehyde solution is 1.5-1.75%, w / v.

15. The method of claim 1, wherein the method further comprises the step of: In step (4), the graft modification temperature is 60-70℃, and the time is 10-12 h.

16. The method of claim 1, wherein the method further comprises: In step (4), the elution is elution using anhydrous ethanol.

17. A natural aldehyde functionalized whole biomass aerogel characterized in that, The natural aldehyde-functionalized whole-biomass aerogel is prepared according to the preparation method of any one of claims 1-16. The natural aldehyde-functionalized whole-biomass aerogel is prepared according to the preparation method of any one of claims 1-16.

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