Natural polyphenol-based hydrogel for metal wastewater treatment as well as preparation method and application of natural polyphenol-based hydrogel
Hydrogels were prepared by copolymerizing natural polyphenols and oxidized polysaccharides, which solved the problems of low stability and low energy coupling efficiency of hydrogel materials in metal wastewater treatment. This resulted in high efficiency in photothermal conversion and evaporation performance, making it suitable for the purification and desalination of metal wastewater.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-23
- Publication Date
- 2026-03-27
AI Technical Summary
Existing hydrogel materials lack the ability to capture metal ions and convert them into photothermal energy, resulting in insufficient stability and low energy coupling efficiency in solar interface evaporation systems, making it difficult to efficiently treat metal wastewater.
Natural polyphenol-based hydrogels are prepared by phenolic reaction of natural polyphenols and oxidized polysaccharides, enabling in-situ growth of polyphenols in the hydrogel network, enhancing photothermal capabilities, and forming highly efficient endogenous photothermal units by chelating metal ions.
It significantly improves the photothermal conversion efficiency and evaporation performance of hydrogels, achieving a metal wastewater treatment efficiency of up to 4.02 kg m⁻² h⁻¹, and enhances freshwater collection capacity.
Smart Images
Figure CN121736293A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the field of solar interface evaporation materials, and particularly relates to a natural polyphenol-based hydrogel for metal wastewater treatment and a preparation method and application thereof. BACKGROUND
[0002] Freshwater scarcity has become a global crisis, with about 4 billion people facing water threats, and a quarter of urban water supply systems under great pressure. At the same time, with the continuous expansion of industrial scale, the discharge of various metal-containing wastewater is rising, further exacerbating water security risks. Under this background, developing efficient and sustainable metal wastewater treatment and reuse technologies has become one of the key paths to alleviate the water resource bottleneck.
[0003] Solar interface evaporation technology (SWG) has shown great potential in seawater desalination and wastewater purification due to its efficient evaporation mechanism and sustainable characteristics driven by solar energy. Among them, the evaporation system based on hydrogel has become the research focus in this field due to its unique three-dimensional hydrophilic network, excellent water transport and water holding capacity, which is particularly beneficial to form "intermediate water" at the interface that is easy to evaporate, thereby reducing evaporation enthalpy and improving energy efficiency.
[0004] Natural polyphenols (such as tannic acid, gallic acid, etc.) are a class of bio-based compounds rich in phenolic hydroxyl and ortho-phenol functional groups, which can efficiently capture various metal ions (such as Cu 2+ , Fe 3+ , etc.) in wastewater through coordination bonds and form metal-polyphenol complexes, so they are often used as heavy metal adsorbents. However, in the existing water treatment technology system, such complexes are usually only treated as adsorption products or waste, and the changes in energy band structure and potential photo-thermal conversion ability that accompany the formation of the complexes are often not fully exploited or effectively utilized in the construction of solar interface evaporation systems.
[0005] However, the current mainstream hydrogel materials (such as polyvinyl alcohol, polyacrylamide-based gel) themselves lack metal ion capture and photo-thermal conversion ability. Existing technologies usually adopt two strategies for functionalization: one is to simply dope natural polyphenols into the gel network, but in this method, the polyphenols are easily leached out, resulting in insufficient material stability and service life; the other is to introduce exogenous photo-thermal agents (such as carbon nanotubes, Ti2O3, polypyrrole, etc.) to endow them with photo-thermal properties, but this approach has two major defects: first, most photo-thermal agents are highly hydrophobic, which can destroy the hydrophilic network of the hydrogel, hinder water transport and the formation of "intermediate water", and weaken the optimization effect of evaporation enthalpy; second, the photo-thermal agent and the polymer matrix are usually only physically blended, and the heat generated is mainly dissipated in a large amount of free water, rather than being efficiently transferred to the intermediate water near the polymer chain, resulting in low heat energy utilization efficiency and severely restricting the further improvement of evaporation performance.
[0006] In summary, current technologies have not yet achieved stable and efficient composites of natural polyphenols within a hydrogel framework, nor have they effectively solved the energy coupling problem between photothermal conversion and intermediate water evaporation. Therefore, there is an urgent need to develop a novel material construction technology that can chemically and securely integrate natural polyphenols into a hydrogel framework, enabling them to sustainably perform metal ion chelation while utilizing the in-situ metal-polyphenol coordination structure formed after chelation as a highly efficient endogenous photothermal unit. Summary of the Invention
[0007] The present invention aims to maximize the limitation and utilization of the heat generated by photothermal conversion for heating the intermediate water inside the gel network, thereby significantly improving the mass transfer efficiency from solar energy to latent heat of vaporization, and ultimately achieving efficient and synergistic purification and desalination of metal wastewater.
[0008] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a natural polyphenol-based hydrogel for metal wastewater treatment, characterized in that a solution containing the natural polyphenol and a solution containing the oxidized polysaccharide are mixed at a mass ratio of natural polyphenol to oxidized polysaccharide of 1:(1~3), and then reacted at 50~70°C for 6~36 h to obtain a natural polyphenol-based hydrogel for metal wastewater treatment. In some preferred embodiments, the mass ratio of the natural polyphenol to the oxidized polysaccharide is 1:2, the reaction temperature is 65°C, and the reaction time is 8~24 h.
[0009] This invention enables natural polyphenols to grow in situ on a hydrogel network through a one-step direct reaction, via phenol-formaldehyde reaction and synergistic assembly with an oxidized polysaccharide network. Furthermore, it utilizes metal chelation capabilities to enhance the photothermal capacity of the hydrogel framework, structurally resolving the poor interfacial compatibility and hydrophilicity / hydrophobicity contradictions caused by the introduction of exogenous photothermal agents. This invention also specifically addresses the problem of low thermal management efficiency in traditional interfacial hydrogels.
[0010] This invention achieves the preparation of high photothermal hydrogels by limiting the mass ratio of natural polyphenols and oxidized polysaccharides and the reaction conditions. When the mass ratio of raw materials is higher than 1:1 or lower than 1:3, it is difficult to form a gel. When the reaction temperature is higher than 70℃ or lower than 50℃, or the reaction time is too low or too high, it will lead to excessively strong or weak cross-linking of the gel, resulting in severe shrinkage of the product, which will prevent it from absorbing water and thus affect its performance.
[0011] In some embodiments, the natural polyphenols are preferably grape seed extract or red wine extract, and more preferably grape seed extract.
[0012] In some embodiments, the oxidized polysaccharide is preferably one or more of oxidized dextran, oxidized deacetylated chitosan, and oxidized konjac glucomannan, and more preferably oxidized dextran.
[0013] In some embodiments, the solution containing natural polyphenols is prepared by dissolving natural polyphenols in a solvent, the solvent including one or more of water, ethanol, and acetonitrile, more preferably ethanol.
[0014] In some embodiments, the solution containing oxidized polysaccharide is obtained by dissolving the oxidized polysaccharide and an alkaline agent in a good solvent, wherein the alkaline agent is preferably sodium hydroxide or sodium carbonate, and the good solvent is deionized water.
[0015] In some embodiments, after the solution containing the natural polyphenols and the solution containing the oxidized polysaccharides have been mixed and reacted, a further soaking treatment is performed in a solution containing transition metal ions. Preferably, the transition metal ions include Fe. 2+ Fe 3+ Cu 2+ One or more.
[0016] This invention directly incorporates natural polyphenols into the gel network and further enhances the photothermal capabilities of the gel's framework by chelating metal ions. Since the intermediate water mainly exists near the gel framework, and the heat energy required for the evaporation of the intermediate water is significantly reduced compared to free water, the gel framework, possessing strong photothermal capabilities, can better heat the intermediate water, achieving efficient heat utilization.
[0017] According to a second aspect of the present invention, the present invention also provides a natural polyphenol-based hydrogel, which is prepared by the above-described preparation method, comprising using natural polyphenols as functional molecules, copolymerizing with oxidized polysaccharides to form a three-dimensional network in situ, thereby obtaining a natural polyphenol-based hydrogel.
[0018] According to a third aspect of the present invention, the application of the above-mentioned natural polyphenol-based hydrogel in a solar interface evaporator is also provided.
[0019] The technical principle adopted in this invention is as follows: using natural polyphenols and oxidized polysaccharides as the main raw materials, a hydrogel is constructed through the phenolic reaction of natural polyphenols and oxidized polysaccharides, and the metal chelating ability of polyphenols is used to further provide photothermal capacity to the hydrogel skeleton.
[0020] Compared with the prior art, the present invention can achieve the following beneficial effects:
[0021] 1. The present invention provides a method for preparing a natural polyphenol-based hydrogel. The method involves rationally analyzing and designing the molecular structure from a chemical perspective, and the resulting hydrogel has polyphenols that are uniformly distributed on the hydrogel skeleton.
[0022] 2. The method of the present invention uses natural polyphenols and oxidized polysaccharides as raw materials. Through copolymerization of natural polyphenols and oxidized polysaccharides, a hydrogel is synthesized in the next step under alkaline heating environment. The hydrogel can effectively chelate metal ions, achieving the purpose of metal ion adsorption in the first step and improving its own photothermal capacity.
[0023] 3. This invention provides a strategy for treating metal wastewater using natural polyphenol-based hydrogels. The hydrogels can adsorb metal ions in the wastewater, thereby fully converting light energy into heat energy across the entire wavelength range of ultraviolet-visible-infrared light, exhibiting a stronger photothermal conversion efficiency. The evaporation efficiency in wastewater can reach up to 4.02 kg m³. -2 h -1 This will further enhance the capacity for freshwater collection and demonstrate great application potential in the field of wastewater treatment. Attached Figure Description
[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.
[0025] Figure 1 The image shows a scanning electron microscope (SEM) image of gel 1 prepared in Example 1.
[0026] Figure 2 The surface temperature rise curves of gels 1, 3, 4, and 5 prepared in Examples 1, 2, 3, and 4 are shown.
[0027] Figure 3 The above are the temperature rise curves for gels 1 and 2.
[0028] Figure 4 This is a schematic diagram showing the evaporation performance test results of gels 1, 3, 4, and 5 under a single solar radiation intensity.
[0029] Figure 5 This is a schematic diagram showing the evaporation performance test results of gels 1 and 2 under a certain solar radiation intensity.
[0030] Figure 6 This is a comparison diagram of the heat distribution inside the novel hydrogel of this invention and a traditional hydrogel.
[0031] Figure 7 This is a photograph of the morphology of gel 1.
[0032] Figure 8 This is a morphological photograph of the cross-section of gel 2.
[0033] Figure 9 This is a morphological photograph of gel 6.
[0034] Figure 10 This is a photograph of the morphology of gel 2.
[0035] Figure 11 Morphological photographs of gels 7 and 8.
[0036] Figure 12 A photograph of the appearance of the hydrogel prepared for Comparative Example 1.
[0037] Figure 13 The image shows the morphology of the hydrogel prepared for Comparative Example 2.
[0038] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0039] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0040] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.
[0041] In the following examples, the natural polyphenols were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No.: 84929-27-1), and all other reagents were purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; the dextran was a number-average molecular weight of 40,000 linked by β-1,3-glycosidic bonds.
[0042] In the following embodiments, the order of preparing the oxidized polysaccharide and the natural polyphenol solution is not limited, nor is the order of preparing the natural polyphenol solution and the solution containing the oxidized polysaccharide limited; any changes to the above order made by those skilled in the art do not exceed the protection scope of this invention.
[0043] Example 1
[0044] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, including the following steps:
[0045] Step 1: Dissolve 10 g of polysaccharide in 500 mL of deionized water, add 0.46 mol of sodium periodate, stir in the dark for 1 day, then dialyze using a 1.2 W dialysis bag to remove small molecules, and freeze-dry to obtain oxidized polysaccharide. The polysaccharide is dextran.
[0046] Step 2: Dissolve 100 mg of grape seed extract in 1 mL of ethanol to obtain a natural polyphenol solution.
[0047] Step 3: Dissolve 200 mg of the oxidized polysaccharide from Step 1 and 10 mg of Na2CO3 in 1 mL of deionized water and stir at room temperature to obtain a solution containing the oxidized polysaccharide.
[0048] Step 4: Under stirring conditions, add the natural polyphenol solution from Step 2 to the solution containing oxidized polysaccharides from Step 3 and mix well. Seal and place in a 65°C oven to stand for 12 hours to obtain a natural polyphenol-based hydrogel.
[0049] Step 5: Immerse the natural polyphenol-based hydrogel from Step 4 in water to remove impurities, specifically small molecules and unreacted raw materials. The hydrogel after impurity removal is labeled as Gel 1.
[0050] Step 6: Soak Gel 1 in a 10 mg / ml ferric chloride aqueous solution for 12 hours, then immerse the hydrogel in water to remove impurities and unchelated ferric chloride salts. The hydrogel after impurity removal is labeled as Gel 2.
[0051] Example 2
[0052] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, which is the same as steps one to five in Example 1, except that in step three, the mass of oxidized polysaccharide is 150 mg, the volume of deionized water is 0.75 mL, and the resulting hydrogel is labeled as gel 3.
[0053] Example 3
[0054] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, which is the same as steps one to five in Example 1, except that in step three, the mass of oxidized polysaccharide is 100 mg, the volume of deionized water is 0.5 mL, and the resulting hydrogel is labeled as gel 4.
[0055] Example 4
[0056] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, which is the same as steps one to five in Example 1, except that in step three, the mass of oxidized polysaccharide is 300 mg, the volume of deionized water is 1.5 mL, and the resulting hydrogel is labeled as gel 5.
[0057] Performance evaluation of hydrogel samples from Examples 1-4:
[0058] Figure 1 This is a scanning electron microscope (SEM) image of the natural polyphenol-based hydrogel (gel 1) from Example 1. The sample preparation process included: freezing the hydrogel in liquid nitrogen and then lyophilizing it to obtain an aerogel; sputter-coating the aerogel with gold to obtain the sample. According to... Figure 1 As can be seen, the hydrogel of this invention produces a cross-linked gel network, exhibiting a gel-like morphology. The gel skeleton appears as a whole, proving that the direct composite of natural polyphenols and oxidized polysaccharides forms a hydrogel, which can ensure the stability of natural polyphenols and their resistance to leaching.
[0059] Figure 2The graphs show the surface temperature changes of gels 1, 3, 4, and 5 under a single solar radiation intensity. The testing method included immersing the hydrogels in water and applying a light intensity of 1 W / m². -2 mm -1 Xenon lamps were used to simulate sunlight, and infrared cameras were used to record the temperature rise of the hydrogel surface. The results are as follows: Figure 2 As shown, all four gels exhibited a certain evaporation efficiency, indicating that the gel preparation method has broad applicability. Meanwhile, gel 1 showed slightly higher evaporation performance; therefore, gel 1 was selected for subsequent metal wastewater treatment.
[0060] Figure 3 This is a schematic diagram showing the photothermal performance test results of gels 1 and 2. The test method included: immersing the above hydrogels in water and irradiating them with a xenon lamp simulating sunlight (light intensity of 1 Wm). -2 mm -1 The surface temperature rise of the hydrogel was recorded using an infrared camera, and the results are as follows: Figure 3 As shown. Based on Figure 3 It can be seen that after soaking Fe 3+ After solution treatment, the temperature rise of gel 2 was significantly higher than that of gel 1, proving that the Fe solution was soaked in the solution. 3+ The solution can effectively enhance the photothermal properties of the hydrogel. This demonstrates that the gel can effectively enhance the photothermal properties by adsorbing Fe. 3+ This achieves the initial enrichment of metal ions and the enhancement of its own photothermal properties.
[0061] Figure 4 The diagram shows the evaporation performance test results of gels 1, 3, 4, and 5 in metal wastewater under a single solar radiation intensity, with all other test conditions being identical. The test method included: taking a glass dish, adding water, placing the hydrogel inside, and covering the water surface between the hydrogel and the glass dish with PC non-porous foam to expose only the upper surface of the hydrogel for evaporation, thus obtaining the evaporation performance testing device. This device was placed on a precision electronic balance, and xenon lamps were used to simulate sunlight, vertically irradiating the surface of the hydrogel. The mass change caused by water evaporation was monitored in real time, and the evaporation rate of the hydrogel was calculated. The evaporation rate calculation formula is: Δv = m / Δt, where m is the mass change of water during the experiment (in kg), and Δt is the vertical projected area of the solar interface evaporator's illuminated surface (in m²). 2 t represents the evaporation time in hours (h). It is evident that the natural polyphenol-based hydrogel of this invention exhibits excellent evaporation capacity in metal wastewater, enabling the collection of distilled water from metal wastewater through photothermal evaporation to achieve water purification.
[0062] Figure 5This diagram illustrates the evaporation performance of gels 1 and 2 in metal wastewater under the same sunlight intensity and other identical test conditions. The results show that after soaking in iron ions, the photothermal capacity of the gels is significantly enhanced, thus increasing the evaporation efficiency from the original 3.03 kg m³. -2 h -1 up to 4.02 kg m -2 h -1 Therefore, it can be seen that after the gel adsorbs metal ions to enhance its photothermal capacity, the interfacial evaporation performance is significantly enhanced, which can significantly improve the acquisition of fresh water.
[0063] Figure 6 This diagram compares the heat distribution mechanism within the novel hydrogel (natural polyphenol-based hydrogel) of this invention with that of a conventional hydrogel. It shows that the gel skeleton of the novel gel is the heat source, so more of the generated heat is utilized by the intermediate water. In contrast, the heat source of the conventional hydrogel is randomly distributed within the hydrogel, and the generated heat also randomly heats the intermediate and free water. Therefore, the novel hydrogel of this invention has higher heat utilization efficiency.
[0064] Figure 7 The image shows the morphology of gel 1. As can be seen, the natural polyphenol-based hydrogel of the present invention has a uniform color and moderate strength.
[0065] Figure 8 This is a morphological photograph of the cross-section of gel 2. Due to the slow diffusion of metal ions, the outer ring of the hydrogel, after chelating the metal, is significantly darker in color than the interior of the gel. This is beneficial for the outer light-receiving layer to obtain stronger photothermal efficiency, thereby improving the evaporation efficiency.
[0066] Example 5
[0067] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, including the following steps:
[0068] Step 1: Dissolve 10 g of polysaccharide in 500 mL of deionized water, add 0.46 mol of sodium periodate, stir in the dark for 1 day, then dialyze using a 1.2 W dialysis bag to remove small molecules, and freeze-dry to obtain oxidized polysaccharide. The polysaccharide is dextran.
[0069] Step 2: Dissolve 100 mg of grape seed extract in 1 mL of ethanol to obtain a natural polyphenol solution.
[0070] Step 3: Dissolve 150 mg of the oxidized polysaccharide from Step 1 and 10 mg of Na2CO3 in 1.5 mL of deionized water and stir at room temperature to obtain a solution containing the oxidized polysaccharide.
[0071] Step 4: Dissolve 10 mg of ferric chloride in 1 ml of deionized water and stir at room temperature to obtain a solution containing Fe. 3+ The solution.
[0072] Step 5: Under stirring conditions, add the natural polyphenol solution described in Step 2 to the oxidized polysaccharide solution described in Step 3, followed by the Fe-containing solution described in Step 4. 3+ The solution was stirred evenly and then placed in a 65℃ oven to stand for 12 hours to obtain a gel.
[0073] Step 6: Remove impurities from the gel obtained in Step 5, and label the resulting hydrogel sample as Gel 6; wherein the impurity removal is performed by immersing the gel in water, with the aim of removing small molecules and unreacted raw materials.
[0074] Figure 9 This is a photograph of the morphology of gel 6 prepared in Example 5. It can be seen that Fe was added beforehand. 3+ The solution, in the end, yielded a gel that was far inferior to gel 2. Figure 10 The gel is black, and gel 6 has extremely poor mechanical strength, making it very brittle. Therefore, in the gel preparation process, it is necessary to first form a gel, and then soak Fe. 3+ Only solutions containing transition metal ions can yield natural polyphenol-based hydrogels with excellent strength and outstanding photothermal properties.
[0075] Example 6
[0076] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, including the following steps:
[0077] Step 1: Dissolve 10 g of polysaccharide in 500 mL of deionized water, add 0.46 mol of sodium periodate, stir in the dark for 1 day, then dialyze with a 1.2W dialysis bag to remove small molecules, freeze dry to obtain oxidized polysaccharide; the polysaccharide is konjac glucomannan.
[0078] Step 2: Dissolve 100 mg of grape seed extract in 1 mL of ethanol to obtain a natural polyphenol solution.
[0079] Step 3: Dissolve 300 mg of the oxidized polysaccharide from Step 1 and 10 mg of Na2CO3 in 1.5 mL of deionized water and stir at room temperature to obtain a solution containing the oxidized polysaccharide.
[0080] Step 4: Under stirring conditions, add the natural polyphenol solution from Step 2 to the solution containing oxidized polysaccharides from Step 3. After stirring until the mixture is homogeneous, seal the container and place it in a 65°C oven to allow the reaction to proceed for 12 hours to obtain a gel.
[0081] Step 5: Remove impurities from the gel obtained in Step 4, and label the resulting hydrogel sample as Gel 7. The impurity removal is performed by immersing the gel in water, with the aim of removing small molecules and unreacted raw materials.
[0082] Example 7
[0083] This embodiment provides a method for preparing a natural polyphenol-based hydrogel, including the following steps:
[0084] Step 1: Dissolve 10 g of polysaccharide in 500 mL of deionized water, add 0.46 mol of sodium periodate, stir in the dark for 1 day, then dialyze with a 1.2W dialysis bag to remove small molecules, freeze dry to obtain oxidized polysaccharide; the polysaccharide is deacetylated chitosan.
[0085] Step 2: Dissolve 100 mg of grape seed extract in 1 mL of ethanol to obtain a natural polyphenol solution.
[0086] Step 3: Dissolve 300 mg of the oxidized polysaccharide from Step 1 and 10 mg of Na2CO3 in 1.5 mL of deionized water and stir at room temperature to obtain a solution containing the oxidized polysaccharide.
[0087] Step 4: Under stirring conditions, add the natural polyphenol solution from Step 2 to the solution containing oxidized polysaccharides from Step 3. After stirring until the mixture is homogeneous, seal the container and place it in a 65°C oven to allow the reaction to proceed for 12 hours to obtain a gel.
[0088] Step 5: Remove impurities from the gel obtained in Step 4, and label the resulting hydrogel sample as Gel 8; the impurity removal is performed by immersing the gel in water, with the aim of removing small molecules and unreacted raw materials.
[0089] Morphological images of gels 7 and 8 from Examples 6 and 7 are shown below. Figure 11 As shown, hydrogels can be prepared using deacetylated chitosan or konjac glucomannan as polysaccharide raw materials through the method of the present invention. Compared with gel 1 prepared using glucomannan as polysaccharide raw material, gels 7 and 8 were also found to have good evaporation capacity in metal wastewater and could achieve the purpose of purifying water quality by collecting distilled water from metal wastewater. However, due to the change in polysaccharide raw materials, the strength changed, the stability was relatively poor, and the service life was not as good as that of Example 1.
[0090] Comparative Example 1
[0091] This comparative study investigated the effect of reaction time on the properties of hydrogels. The preparation method was the same as that in Example 1, except that the reaction time in step four was 6 h.
[0092] Comparative Example 2
[0093] This comparative study investigated the effect of reaction time on the properties of hydrogels. The preparation method was the same as that in Example 1, except that the reaction time in step four was 40 h.
[0094] The hydrogel morphologies of Comparative Examples 1 and 2 are as follows: Figure 12 and13 As shown, when the reaction time is extended to 40 hours, the hydrogel becomes brittle and structurally unstable. When the reaction time is shortened to 6 hours, the hydrogel structure becomes soft, tends to flow, and its strength is significantly reduced, making it prone to breakage. Extensive testing has determined that a reaction time of 8-24 hours is optimal.
[0095] Comparative Example 3
[0096] This comparative study investigated the effect of alkaline preparations in a solution containing oxidized polysaccharides on the hydrogel product. The preparation method was basically the same as in Example 1, except that sodium hydroxide was used to replace an equal amount of sodium carbonate in step three.
[0097] Comparative Example 3 did not obtain a stable hydrogel, possibly because the sodium hydroxide was too alkaline and the reaction was too violent, resulting in a shorter lifespan for the gel compared to Example 1.
[0098] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.
Claims
1. A method for preparing a natural polyphenol-based hydrogel for treating metal wastewater, characterized in that, A solution containing natural polyphenols and a solution containing oxidized polysaccharides are mixed at a mass ratio of 1:(1~3) and reacted at 50~70℃ for 6~36 h to obtain a natural polyphenol-based hydrogel for metal wastewater treatment.
2. The method for preparing natural polyphenol-based hydrogels for metal wastewater treatment according to claim 1, characterized in that, The natural polyphenols are grape seed extract or red wine extract; And / or, the oxidized polysaccharide is one or more of oxidized dextran, oxidized deacetylated chitosan, and oxidized konjac glucomannan.
3. The method for preparing natural polyphenol-based hydrogels for metal wastewater treatment according to claim 1, characterized in that, The solvent in the solution containing the natural polyphenols is one or more of water, ethanol, and acetonitrile; And / or, the solution containing the oxidized polysaccharide is obtained by dissolving the oxidized polysaccharide and an alkaline preparation in a good solvent.
4. The method for preparing the natural polyphenol-based hydrogel for metal wastewater treatment according to claim 3, characterized in that, The alkaline agent is sodium hydroxide or sodium carbonate, and the good solvent is deionized water.
5. The method for preparing a natural polyphenol-based hydrogel for metal wastewater treatment according to any one of claims 1-4, characterized in that, After the solution containing the natural polyphenols and the solution containing the oxidized polysaccharides are mixed and reacted, the mixture is further soaked in a solution containing transition metal ions.
6. The method for preparing the natural polyphenol-based hydrogel for metal wastewater treatment according to claim 5, characterized in that, The transition metal ions include Fe 2+ Fe 3+ Cu 2+ One or more.
7. A natural polyphenol-based hydrogel, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.
8. The application of the natural polyphenol-based hydrogel of claim 5 or the photothermal-enhanced natural polyphenol-based hydrogel of claim 7 in a solar interface evaporator.