Soy protein / polyvinyl alcohol-dopamine composite water treatment material having sponge structure

Abstract

The present invention relates to the technical field of bio-based water treatment materials, and specifically relates to a soy protein / polyvinyl alcohol-dopamine composite water treatment material having a sponge structure. The material is prepared by means of the steps of: step I: obtaining carboxylated polyvinyl alcohol; step II: introducing dopamine hydrochloride to react with same to obtain a dopamine-grafted polyvinyl alcohol solution; step III: subjecting the dopamine-grafted polyvinyl alcohol solution to dialysis and rotary evaporation concentration treatment to obtain a dopamine-grafted polyvinyl alcohol concentrated solution; step IV: adding soy protein isolate to the dopamine-grafted polyvinyl alcohol concentrated solution, and performing freeze drying to obtain a complex; and step V: soaking the complex in an n-hexane solution of methyltrimethoxysilane, and finally drying in a drying oven to obtain the soy protein / polyvinyl alcohol-dopamine composite water treatment material having a sponge structure. The material is environmentally friendly, has an elastic and porous structure, can repeatedly adsorb oil products, and has selective adsorption for cationic dyes.

Description

A soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure Technical Field

[0001] This invention relates to the field of bio-based water treatment materials technology, specifically to a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure. Background Technology

[0002] Pollution of aquatic ecosystems causes diseases and even death in humans, plants, and other organisms worldwide. To improve environmental sustainability, effective wastewater management is essential, and water must be purified to a level safe for drinking, washing, and discharge into rivers, lakes, and oceans. Currently, various water purification technologies exist, such as adsorption, chemical precipitation, ion exchange, reverse osmosis, and electrochemical treatment. Among these, adsorption has become a promising solution due to its high efficiency, low cost, and ease of operation. Most adsorbents studied are in powder or membrane form, both of which have the following drawbacks: First, powdered adsorbents have a large specific surface area but are difficult to recover, which is detrimental to practical water treatment applications; second, membrane adsorbents are too thin, and although they have a strong adsorption capacity per unit weight, the single adsorption capacity of membrane materials is insufficient, and they are easily damaged in practical applications. Due to the effectiveness, low cost, eco-friendliness, and biodegradability of biomass-based adsorbents, and also in line with the American Chemical Society's "green chemistry" initiative, the use of biomass-based adsorbents in the field of water treatment is more attractive than other adsorbents. Therefore, there is an urgent need to develop a biomass-based adsorbent with large adsorption capacity, simple preparation method, and easy recovery to overcome the limitations of existing adsorbents. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure. This material can not only efficiently adsorb oil and dye pollutants, but also can be reused, and has the advantages of being environmentally friendly and low cost.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure is provided, which is prepared by the following method, the method comprising the following steps:

[0006] Step 1: Dissolve polyvinyl alcohol in anhydrous dimethyl sulfoxide to obtain a polyvinyl alcohol solution. Cool the solution to room temperature, then add succinic anhydride and triethylamine in sequence and mix them to obtain a carboxylated polyvinyl alcohol solution.

[0007] Step 2: Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to the carboxylated polyvinyl alcohol solution and stir to react. Then add dopamine hydrochloride and triethylamine and continue the reaction at room temperature and under nitrogen to obtain a dopamine-grafted polyvinyl alcohol solution.

[0008] Step 3: The dopamine-grafted polyvinyl alcohol solution is concentrated by dialysis and rotary evaporation to obtain a concentrated dopamine-grafted polyvinyl alcohol solution.

[0009] Step 4: Add soy protein isolate to the dopamine-grafted polyvinyl alcohol concentrate solution, use deionized water for quantitative measurement, then add glycerol and mix well, adjust the pH to 9-11, continue stirring until homogeneous, and then freeze dry to obtain the complex.

[0010] Step 5: Mix methyltrimethoxysilane and n-hexane evenly to obtain a mixed soaking solution. Add the composite to the mixed soaking solution and soak. After soaking, dry in an oven to obtain a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure.

[0011] In some embodiments, in step one, the weight ratio of polyvinyl alcohol, anhydrous dimethyl sulfoxide solution, succinic anhydride and triethylamine is 1~3:60~120:0.2~0.8:0.2~0.8.

[0012] In some embodiments, in step two, the weight ratio of the carboxylated polyvinyl alcohol solution, the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dopamine hydrochloride, and triethylamine is 90~120:0.5~10:0.3~0.6:0.5~1:0.2~0.6.

[0013] In some implementations, in step four, the ratio of the volume of deionized water to the volume of glycerol is 10:0.1~0.5.

[0014] In some implementations, the mixing reaction time in step one is 20-30 hours.

[0015] In some implementations, in step two, the reaction continues at room temperature for 20-30 hours.

[0016] In some embodiments, in step three, the dopamine-grafted polyvinyl alcohol solution after dialysis is concentrated by rotary evaporation to 4 to 5 times the original concentration of the dopamine-grafted polyvinyl alcohol solution.

[0017] In some implementations, in step four, the mixture is stirred in a magnetic stirrer for 0.5 to 2 hours.

[0018] In some embodiments, the complex is soaked in the mixed soaking solution for 1 to 3 hours.

[0019] In some embodiments, in step five, the drying temperature in the oven is 50~70°C.

[0020] The beneficial effects of the soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure of the present invention are as follows:

[0021] (1) The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure of the present invention, due to the gradual slow movement of water molecules in the soybean protein / polyvinyl alcohol-dopamine mixture during freezing and the orderly aggregation due to hydrogen bond interactions, forms an ice crystal structure in the soybean protein / polyvinyl alcohol-dopamine mixture during the molding process. This allows the ice crystals to sublimate during vacuum freeze-drying, forming pores at the ice crystal locations, thus creating a three-dimensional interconnected porous material, which is beneficial for the adsorption and retention of oils (toluene, kerosene, hydraulic oil, and soybean oil). By controlling the amount of ice crystals, the composite sponge density can be achieved to 0.1 g / cm³. 3 This allows the composite sponge to float on the water surface after absorbing oil, facilitating the rapid recovery of the water-treated sponge. It also allows the pore surface area of ​​the composite sponge to reach 0.75 m². 2 / g, with a porosity of up to 92% and a total pore volume of up to 11 mL / g, resulting in a greater saturation capacity for adsorbing oils.

[0022] (2) The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure of the present invention has dopamine grafted onto polyvinyl alcohol to obtain an elastic structure. This elastic structure is added to soybean protein isolate, which effectively improves the brittleness of soybean protein isolate itself. The two components of soybean protein isolate and polyvinyl alcohol-dopamine can be prepared into a composite sponge with elastic characteristics, which can be reused after adsorbing oil and extruding.

[0023] (3) The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure of the present invention, due to the grafting of succinic anhydride and dopamine, gives the material phenolic hydroxyl and carboxyl functional groups. The presence of the two acidic groups, carboxyl and phenolic hydroxyl, causes the material to ionize H+ in aqueous solution. + Under electrostatic interaction, the generated anionic functional groups have a stronger selective adsorption effect on cationic dyes (methylene blue), which is beneficial to the adsorption of cationic dyes and increases the dye adsorption capacity.

[0024] (4) The invention has a sponge-structured soybean protein / polyvinyl alcohol-dopamine composite water treatment material. Soy protein isolate is an amphiphilic substance that is not only lipophilic but can also adsorb dyes dissolved in water.

[0025] (5) The invention of a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure uses soybean protein isolate, polyvinyl alcohol and dopamine as biomass raw materials. It does not rely on petrochemical products, avoids secondary pollution, and has the characteristics of being inexpensive, renewable and easy to degrade, making it suitable for large-scale production and application. Attached Figure Description

[0026] Figure 1 is a flowchart of the synthesis of SPI / PVA-DP composite material with a sponge structure;

[0027] Figure 2 shows a comparison of the adsorption performance of different oils on the SPI / PVA-DP composite material with a sponge structure.

[0028] Figure 3 shows the oil-water separation efficiency of the SPI / PVA-DP composite material with a sponge structure for different oil products;

[0029] Figure 4 shows the adsorption capacity of methylene blue dye for the SPI / PVA-DP composite material with a sponge structure.

[0030] Figure 5 shows the pore size distribution of three SPI / PVA-DP composite materials with sponge structures;

[0031] Figure 6 shows (a) XPS spectra of PVA, DP, and PVA-DP; (b) ATR-FTIR spectra of PVA and PVA-DP; (c), (e), and (g) C1s curve fitting results for pure PVA, pure DP, and PVA-DP, respectively; and (d), (f), and (h) N1s curve fitting results for pure PVA, pure DP, and PVA-DP, respectively.

[0032] Figure 7 shows the SEM image of the SPI / PVA-DP shear plane with a sponge structure;

[0033] Figure 8 shows the compressive stress-strain curves of SPI / PVA and SPI / PVA-DP composite materials at 50% strain;

[0034] Figure 9 shows the shape of SPI / PVA and SPI / PVA-DP under 90% compressive strain. Detailed Implementation

[0035] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Example

[0036] The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure disclosed in this embodiment, as shown in Figure 1, is prepared by the following method, which includes the following steps:

[0037] Step 1: Dissolve polyvinyl alcohol in anhydrous dimethyl sulfoxide to obtain a polyvinyl alcohol solution. Cool the solution to room temperature, then add succinic anhydride and triethylamine in sequence and mix them to obtain a carboxylated polyvinyl alcohol solution.

[0038] First, polyvinyl alcohol (PVA) is dissolved in anhydrous dimethyl sulfoxide (DMSO). PVA is soluble in DMSO because DMSO is a highly polar solvent that can form hydrogen bonds with the hydroxyl groups in PVA, thus aiding in its dissolution.

[0039] The obtained polyvinyl alcohol-DMSO solution was cooled to room temperature to facilitate subsequent reactions. Succinic anhydride was then added to the cooled mixture. Succinic anhydride is a commonly used carboxylic anhydride that reacts with the hydroxyl groups in polyvinyl alcohol to introduce carboxyl functional groups. After adding succinic anhydride, triethylamine was further added. Triethylamine may act as a catalyst or acid-binding agent here, promoting the reaction between succinic anhydride and polyvinyl alcohol to form carboxylated polyvinyl alcohol. After adding triethylamine, the mixture needs to be thoroughly stirred to ensure uniform reaction and complete carboxylation, resulting in carboxylated polyvinyl alcohol. This modified polyvinyl alcohol has more carboxyl functional groups, which can improve its water solubility and crosslinking reactivity.

[0040] Step 2: Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to the carboxylated polyvinyl alcohol solution and stir to react. Then add dopamine hydrochloride and triethylamine and continue the reaction at room temperature and under nitrogen to obtain a dopamine-grafted polyvinyl alcohol solution.

[0041] 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and N-hydroxysuccinimide (NHS) were added to carboxylated polyvinyl alcohol. EDC·HCl and NHS are commonly used carboxyl activators; EDC·HCl reacts with carboxyl groups to form an active intermediate, which then reacts with NHS to generate the NHS ester intermediate. After adding EDC·HCl and NHS, the solution was stirred to promote the reaction. Dopamine hydrochloride and triethylamine were then added to the reaction system. Dopamine hydrochloride provided dopamine molecules, while triethylamine acted as a base catalyst, promoting the reaction between the NHS ester and the primary amine groups in the dopamine molecules to form stable amide bonds. After adding dopamine hydrochloride and triethylamine, the reaction was continued under stirring at room temperature and a nitrogen atmosphere to ensure that the dopamine molecules could fully react with the NHS ester to form dopamine-grafted polyvinyl alcohol.

[0042] Step 3: The dopamine-grafted polyvinyl alcohol solution is concentrated by dialysis and rotary evaporation to obtain a concentrated dopamine-grafted polyvinyl alcohol solution.

[0043] Dialysis removes unreacted monomers, low molecular weight polymers, and small molecule impurities from the solution. This process typically lasts for two days to ensure optimal dialysis results. After dialysis, the dopamine-grafted polyvinyl alcohol solution is transferred to a rotary evaporator. By reducing pressure and heating, the solvent (usually water) evaporates, increasing the concentration of dopamine-grafted polyvinyl alcohol in the solution. This process effectively reduces solution volume and removes unwanted impurities, yielding a high-concentration dopamine-grafted polyvinyl alcohol solution.

[0044] Step 4: Add soy protein isolate to the dopamine-grafted polyvinyl alcohol concentrate solution, use deionized water for quantitative measurement, then add glycerol and mix well, adjust the pH to 9-11, continue stirring until homogeneous, and then freeze dry to obtain the complex.

[0045] A certain amount of deionized water is added to the solution to adjust its concentration and viscosity, making it suitable for subsequent processing. Glycerin can enhance the plasticity of the material by weakening the intermolecular forces between polymer chains and increasing their mobility. After adding all components, the solution needs to be thoroughly stirred to ensure uniform distribution and a homogeneous mixture. The pH of the solution is adjusted to 9-11 by adding an alkaline substance (such as sodium hydroxide). This pH range is beneficial for protein dissolution and the stability of dopamine-grafted polyvinyl alcohol. After adjusting the pH, the solution is stirred continuously to ensure uniform distribution of the pH adjuster and that the solution remains homogeneous. The homogeneous mixture is then freeze-dried. Freeze-drying, a method of removing water from the solution under low temperature and vacuum conditions, preserves the microstructure and active ingredients of the material, avoids damage to heat-sensitive components, and allows the removal of water to create a porous structure where ice crystals were previously present.

[0046] Step 5: Mix methyltrimethoxysilane and n-hexane evenly to obtain a mixed soaking solution. Add the composite to the mixed soaking solution and soak. After soaking, dry in an oven to obtain a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure.

[0047] After the above steps, a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure is obtained. This material combines the properties of soybean protein, polyvinyl alcohol, and dopamine, providing high specific surface area and porosity through its sponge structure.

[0048] This process involves multiple steps, including surface modification of the material, freeze-drying, immersion treatment, and heat treatment, ultimately producing a composite material with specific structure and properties. The sponge-like structure of this material may help improve its adsorption performance in water treatment.

[0049] In this embodiment, in step one, the weight ratio of polyvinyl alcohol, anhydrous dimethyl sulfoxide solution, succinic anhydride and triethylamine is 1~3:60~120:0.2~0.8:0.2~0.8, preferably 2.2:108:0.5:0.5.

[0050] In this embodiment, in step two, the weight ratio of the carboxylated polyvinyl alcohol solution, the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dopamine hydrochloride, and triethylamine is 90~120:0.5~10:0.3~0.6:0.5~1:0.2~0.6, preferably 111:0.9:0.5:0.9:0.5.

[0051] In this embodiment, in step four, the ratio of the volume of deionized water to the volume of glycerol is 10:0.1~0.5, preferably 10:0.2. Specific parameters can be selected according to actual conditions and are not limited to a single value here.

[0052] In this embodiment, the mixing reaction time in step one is 20-30 hours, preferably 24 hours. Specific parameters can be selected based on actual conditions and are not limited to a single value here.

[0053] In this embodiment, in step two, the reaction continues at room temperature for 20-30 hours, preferably 24 hours. Specific parameters can be selected based on actual conditions and are not limited to a single value here.

[0054] In this embodiment, in step three, the dopamine-grafted polyvinyl alcohol solution after dialysis is concentrated by rotary evaporation to 4-5 times its original concentration. Specific parameters can be selected according to actual conditions and are not limited to a single specific value here.

[0055] In this embodiment, in step four, the mixture is stirred in a magnetic stirrer for 0.5 to 2 hours, preferably 1 hour. Specific parameters can be selected according to actual conditions and are not limited to a single parameter here.

[0056] In this embodiment, the soaking time of the freeze-dried composite in the mixed soaking solution is 1-3 hours, preferably 2 hours. Specific parameters can be selected according to actual conditions and are not limited to a single value here.

[0057] In this embodiment, in step five, the drying temperature in the oven is 50~70℃, preferably 60℃. Specific parameters can be selected according to actual conditions and are not limited to a single value here.

[0058] Effect verification:

[0059] To further verify the characteristics and functions of the soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure of the present invention, experimental examples and comparative examples were conducted.

[0060] The abbreviations for each component are as follows:

[0061] SPI / PVA-DP Soy Protein Isolate / Polyvinyl Alcohol-Dopamine

[0062] SPI / PVA Soy Protein Isolate / Polyvinyl Alcohol

[0063] SPI Soy Protein Isolate

[0064] PVA (Polyvinyl alcohol)

[0065] DP dopamine

[0066] Test case

[0067] Step 1: Synthesis of carboxylated PVA. PVA (2.2 g, 50 mmol AOH groups) was dissolved in anhydrous DMSO (100 mL), and the solution was cooled to room temperature. Succinic anhydride (0.5 g, 5.0 mmol) and triethylamine (0.5 g, 5.0 mmol) were added sequentially, and the reaction was carried out for 24 h to obtain carboxylated PVA.

[0068] Step 2: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC HCl) (957.8 mg, 5.0 mmol) and N-hydroxysuccinimide (NHS) (575 mg, 5 mmol) were added to the reaction solution containing carboxyl-functionalized PVA and stirred for 30 min. Then, dopamine hydrochloride (948.20 mg, 5.0 mmol) and triethylamine (505.95 mg, 5.0 mmol) were added, and the reaction was stirred at room temperature and under N2 for 24 h to obtain dopamine-grafted polyvinyl alcohol (PVA-DP).

[0069] Step 3: After dialyzing the sample solution for 2 days, concentrate the sample solution to 4-5 times by rotary evaporation, take 2 mL of the sample solution, freeze dry it, and weigh it to determine the concentration of the sample solution;

[0070] Step 4: Weigh SPI at SPI:PVA-DP weight ratios of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 and add it to a 25 mL beaker containing PVA-DP sample solution, with a solid content of 0.3 g. Add deionized water to control the final volume to 10 mL. Add 0.2 mL of glycerol to each sample solution, and finally adjust the pH of the sample solution to 10 with 15% NaOH solution. Stir the above sample solution at room temperature for 1 h using a magnetic stirrer, then remove and freeze-dry.

[0071] Step 5: The freeze-dried samples were immersed in 20 mL of 1.5% methyltrimethoxysilane (MTMS) / n-hexane solution for 2 h. Subsequently, they were dried in an oven at 60 °C to obtain cylindrical SPI / PVA-DP products with a diameter of 30 mm and a height of 15 mm.

[0072] The soybean protein / polyvinyl alcohol-dopamine composite water treatment materials with sponge structures obtained in the experimental examples (hereinafter referred to as sponge structures), namely SPI / PVA-DP composite sponges, adsorbed toluene, kerosene, hydraulic oil, and soybean oil, and their saturated adsorption capacity, adsorption rate, and reusability were compared. As shown in Figure 2(a), compared with commercial PP oil-absorbing felt, the 60:40, 40:60, and 20:80 sponge structures of soybean protein / polyvinyl alcohol-dopamine composite water treatment materials have a larger oil adsorption capacity, reaching a maximum of 9.21 g / g. The 100:0, 80:20, and 0:100 structures are slightly inferior to PP oil-absorbing felt. As shown in Figures 2(b), (c), (d), and (e), all composite sponges can almost reach full adsorption within 5 minutes, and reach saturated adsorption capacity within 30 minutes. Figures 2(f), (g), (h), and (i) demonstrate the reusability of the composite sponge for adsorbing different oils. Even after 10 uses, the recovery rate remains above 90%, and the adsorption capacity even increases compared to the first use. Furthermore, Figure 3 shows that the SPI / PVA-DP composite sponge achieves oil-water separation efficiencies of over 95% for toluene, kerosene, hydraulic oil, and soybean oil. Therefore, this composite sponge can be used in practical oil-water separation applications.

[0073] In a 200 μg / mL methylene blue solution, all the composite sponges obtained in the experimental examples showed adsorption values ​​for methylene blue exceeding 48 mg / g (Figure 4). The 100:0, 80:20, and 60:40 composite sponges exhibited higher adsorption values ​​of 54.5 mg / g, 54.2 mg / g, and 54.4 mg / g, respectively. Simultaneously, the adsorption efficiency of these composite sponges for methylene blue exceeded 85%, indicating their effective adsorption of the cationic dye (methylene blue). In contrast, when the composite sponge was subjected to two hours of adsorption in a 150 μg / mL anionic dye (Acid Blue 92), no adsorption of Acid Blue 92 was detected. Clearly, the composite sponge, rich in anionic groups such as phenolic hydroxyl and carboxyl groups, exhibits selective adsorption of cationic dyes.

[0074]

[0075] Figure 5 shows the pore size distribution of SPI / PVA-DP composite sponges with three different weight ratios. The 80:20 and 60:40 composite sponges exhibit similar average pore sizes of 61.95 μm and 61.75 μm, respectively, while the 40:60 composite sponge has an average pore size of 40.70 μm. The porosities of the 80:20, 60:40, and 40:60 composite sponges are 91.88%, 91.15%, and 89.00%, respectively. This indicates that the composite sponge has a high porosity and large pore structure. Its total pore volume and total pore surface area demonstrate that the composite sponge has a large adsorption space and adsorption surface, confirming its advantages in various applications of water treatment. Table 1 shows that the sample densities range from 0.08 to 0.12 g / cm³. 3 This indicates that the composite material can be prepared using a small amount of raw materials, and is lightweight and efficient.

[0076] To verify the successful grafting of DP onto PVA, XPS technology (Figure 6) was used to analyze surface chemical changes and chemical composition. For pure PVA, C1s, O1s, and N1s peaks were detected, with C and O accounting for 68.50% and 31.20% of the PVA content, respectively, while N accounted for only 0.30%, suggesting that N may be a contaminant or that the sample is impure. Since DP itself contains N, a very strong N1s peak was detected, which is absent in pure PVA. However, in the XPS spectrum of the PVA-DP sample, a relatively strong N1s peak appeared, with C, O, and N accounting for 63.53%, 21.18%, and 2.2% of the sample content, respectively. Clearly, the C and O contents of the target sample were lower than those of pure PVA, while the N content was higher. Furthermore, the C1s peak fractionation revealed a new peak at 288.1 eV, belonging to C=O. The C=O is due to the grafting of succinic anhydride onto PVA. Subsequently, when DP is grafted with carboxylated polyvinyl alcohol, C=O will also be generated. This confirms that the reaction formula is valid and the PVA-DP synthesis is successful.

[0077] In the infrared spectra of PVA and PVA-DP (Figure 6b), at 3290 cm⁻¹ -1 There is a broad and strong absorption at 2920 cm⁻¹, which is attributed to the symmetric stretching vibration of the -OH group; while at 2920 cm⁻¹... -1 The peak at 1090 cm⁻¹ is attributed to the CH stretching vibration peak of saturated C; -1 The peak at this point may be due to the CO stretching vibration of alcohol or phenolic hydroxyl groups. The peak at this point is relatively stronger in the target product PVA-DP compared to pure PVA, indicating that the addition of phenolic hydroxyl groups to DP increases the total number of hydroxyl groups in the target product. PVA-DP peaks at 1720 cm⁻¹ -1 A new peak was observed at 1650 cm⁻¹, indicating the formation of an ester bond (-COO) in the target product PVA-DP. Meanwhile, PVA-DP showed a peak at 1650 cm⁻¹. -1 The new peaks generated at this point represent the C=C stretching vibration of the aromatic ring. The appearance of these two new peaks further confirms that DP has been successfully grafted onto PVA.

[0078] As shown in Figure 7, all samples exhibit a porous structure. The composite sponge prepared with soy protein isolate (i.e., 100:0) has a relatively simple pore structure, with fewer pores on the pore walls compared to the 20 μm micrographs of the other samples. The other samples have very rich pore structures, especially the 80:20, 60:40, and 40:60 samples, which have very dense pores on the pore walls. Furthermore, the higher the protein content, the larger the pores, indicating that the addition of soy protein isolate has a positive effect on the pore structure of this porous composite sponge.

[0079] Comparative Example

[0080] To illustrate the effect of adding dopamine in this invention, a comparative example of a soybean protein / polyvinyl alcohol composite sponge for water treatment is provided below:

[0081] At 90 °C, PVA was dissolved in 10 mL of deionized water. After complete dissolution, SPI was added to a 25 mL beaker (SPI:PVA weight ratio of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100), with a solid content of 0.3 g. The pH of the sample solution was adjusted to 10 with 15% NaOH solution. The mixture was stirred in a magnetic stirrer at room temperature for 1 h. The solution was then removed and freeze-dried to obtain a cylindrical SPI / PVA product with a diameter of 30 mm and a height of 15 mm.

[0082] As shown in Figure 8, the SPI / PVA composite sponge had lost more than 20% of its height after the fifth compression at 50% strain and could not recover. After 10 cycles of 50% compression strain, the composite sponge was severely deformed, proving its lack of elasticity. In contrast, the dopamine-grafted composite sponge only underwent slight deformation after 50 cycles of 50% compression strain and almost recovered to its original height upon release of the external force. Figure 9 shows that, within the same batch and of the same size, the SPI / PVA composite sponge became flattened after 90% strain. Except for the 100:0 strain, other SPI / PVA-DP composite sponges could almost recover to their original height, indicating that most SPI / PVA-DP composite sponges possess good elasticity and compression properties.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure, characterized in that, It is prepared by the following method, which includes the following steps: Step 1: Dissolve polyvinyl alcohol in anhydrous dimethyl sulfoxide to obtain a polyvinyl alcohol solution. Cool the solution to room temperature, then add succinic anhydride and triethylamine in sequence and mix them to obtain a carboxylated polyvinyl alcohol solution. Step 2: Add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide to the carboxylated polyvinyl alcohol solution and stir to react. Then add dopamine hydrochloride and triethylamine and continue the reaction at room temperature and under nitrogen to obtain a dopamine-grafted polyvinyl alcohol solution. Step 3: The dopamine-grafted polyvinyl alcohol solution is concentrated by dialysis and rotary evaporation to obtain a concentrated dopamine-grafted polyvinyl alcohol solution. Step 4: Add soy protein isolate to the dopamine-grafted polyvinyl alcohol concentrate solution, use deionized water for quantitative measurement, then add glycerol and mix well, adjust the pH to 9-11, continue stirring until homogeneous, and then freeze dry to obtain the complex. Step 5: Mix methyltrimethoxysilane and n-hexane evenly to obtain a mixed soaking solution. Add the composite to the mixed soaking solution and soak. After soaking, dry in an oven to obtain a soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure.

2. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step one, the weight ratio of polyvinyl alcohol, anhydrous dimethyl sulfoxide solution, succinic anhydride and triethylamine is 1~3:60~120:0.2~0.8:0.2~0.

8.

3. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step two, the weight ratio of the carboxylated polyvinyl alcohol solution, the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, dopamine hydrochloride and triethylamine is 90~120:0.5~10:0.3~0.6:0.5~1:0.2~0.

6.

4. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step four, the ratio of the volume of deionized water after quantitative determination to the volume of glycerol is 10:0.1~0.

5.

5. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step one, the mixing reaction takes 20-30 hours.

6. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step two, the reaction continues at room temperature for 20-30 hours.

7. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step three, the dopamine-grafted polyvinyl alcohol solution after dialysis is concentrated by rotary evaporation to 4 to 5 times the original concentration of the dopamine-grafted polyvinyl alcohol solution.

8. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step four, stir in a magnetic stirrer for 0.5 to 2 hours.

9. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, The composite is soaked in the mixed soaking solution for 1 to 3 hours.

10. The soybean protein / polyvinyl alcohol-dopamine composite water treatment material with a sponge structure according to claim 1, characterized in that, In step five, the drying temperature in the oven is 50~70℃.

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