A microporous hydrophilic sponge material and a method for its preparation

Abstract

The present application relates to a kind of microporous hydrophilic sponge material and the preparation method of the sponge material.The microporous hydrophilic sponge is polyvinyl alcohol sponge, is obtained by the following raw material system reaction, by weight fraction, including each raw material component as follows: first polyvinyl alcohol 100 parts, second polyvinyl alcohol 50-100 parts, deionized water 500-800 parts, formaldehyde aqueous solution 90-150 parts, aliphatic dialdehyde aqueous solution 0.2-0.6 parts, sulfuric acid 30-50 parts;The degree of polymerization of the first polyvinyl alcohol is 1500-2400;The degree of polymerization of second polyvinyl alcohol is 300-700.The microporous hydrophilic sponge material can be used for emulsion separation, average pore size is 5-15 μm, emulsion separation efficiency is greater than 95%;Water flux is greater than 4000 L h ‑1 m ‑2 bar ‑1 .

Description

Technical Field

[0001] This invention relates to the field of porous sponge materials, and more specifically, to a microporous hydrophilic sponge material and a method for preparing the sponge material. Background Technology

[0002] With the development of modern industry, a large amount of oily wastewater has been generated, posing a serious threat to human health and the natural environment. Oils in oily wastewater typically fall into four categories: floatable oil, dispersed oil, emulsified oil, and dissolved oil. Floatable and dispersed oils have larger particle sizes and are unstable, making removal methods relatively simple. Emulsified oils, however, have diameters less than 20 μm and are stably dispersed in the aqueous phase under the action of surfactants, posing a greater hazard and being difficult to separate. Common emulsion separation strategies include gravity separation, centrifugation, flotation, and coalescence separation, but these methods are energy-intensive and have low separation efficiency. Therefore, seeking low-energy-consumption, high-efficiency emulsion separation technologies is a hot topic in this field.

[0003] Sponges, as three-dimensional porous materials, possess advantages such as high porosity, low density, and low cost, and have attracted much attention in the field of emulsion separation in recent years. Sponges used for emulsion separation are divided into hydrophilic and oleophilic types. Their separation principle utilizes special wettability to selectively filter either the aqueous or oil phase. Compared with oleophilic sponges, hydrophilic sponges have higher separation efficiency, higher reusability, and avoid secondary pollution, thus possessing greater application potential. Polyvinyl alcohol (PVA) sponges are a type of hydrophilic sponge material produced by the acetal reaction of polyvinyl alcohol (PVA) with formaldehyde under acidic conditions. The main raw material for producing PVA sponges is high-polymerization-degree PVA, typically above 1700. However, when using only PVA as a raw material to prepare microporous sponges, the pore structure is prone to collapse, making it difficult to directly obtain sponge materials with open-cell structures. Therefore, to prepare sponge materials, pore-forming agents or surfactants are usually added to create pores. However, in the process of preparing PVA sponges, the use of pore-forming agents such as starch can easily cause environmental pollution, and the resulting sponge material has excessively large pore sizes, resulting in insufficient oil droplet interception capabilities.

[0004] Suitable pore size, high porosity, and excellent hydrophilicity are fundamental conditions for effective emulsion separation using microporous light water sponges. Currently, microporous light water polyvinyl alcohol sponges prepared by finely adjusting the amounts of pore-forming agents and formaldehyde are difficult to simultaneously meet the separation efficiency and water flux requirements for emulsion separation.

[0005] The information disclosed in the Background section is only for the purpose of helping to understand the background of the present invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] To address the aforementioned challenges, this invention prepares a microporous, light-water polyvinyl alcohol sponge by utilizing the synergistic reaction of various polyvinyl alcohol raw materials and different aldehydes without using starch or surfactants or other pore-forming agents.

[0007] The purpose of this invention is to provide a microporous hydrophilic sponge material and its preparation method. This microporous hydrophilic sponge material can be used for emulsion separation, with an average pore size of 5-15 μm, an emulsion separation efficiency greater than 95%, and a water flux greater than 4000 L / h. -1 m - 2 bar -1 .

[0008] The pore-forming mechanism of this invention differs from previous literature. The raw materials used include at least two PVA raw materials with different degrees of polymerization and two aldehyde raw materials with different functional groups. It mainly utilizes the differences in migration and reactivity caused by the different viscosity and activity of different PVA raw materials and aldehyde raw materials in the reaction system, so that some PVA reacts first to form a low-shrinkage porous framework structure. Then, within this porous framework, the remaining unreacted PVA undergoes an acetal reaction, ultimately forming an acetal sponge structure with high overall open porosity and low shrinkage.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a microporous hydrophilic sponge material, characterized in that the microporous hydrophilic sponge is a polyvinyl alcohol sponge, obtained by reacting the following raw material system, comprising the following raw materials by weight: 100 parts of first polyvinyl alcohol, 50-100 parts of second polyvinyl alcohol, 500-800 parts of deionized water, 90-150 parts of formaldehyde aqueous solution, 0.2-0.6 parts of aliphatic dialdehyde aqueous solution, and 30-50 parts of sulfuric acid; the degree of polymerization of the first polyvinyl alcohol is 1500-2400; the degree of polymerization of the second polyvinyl alcohol is 300-700; the concentration of the formaldehyde aqueous solution is 37 wt%; the concentration of the aliphatic dialdehyde aqueous solution is 50 wt%; and the concentration of sulfuric acid is 98 wt%.

[0010] The first polyvinyl alcohol has a degree of polymerization of 1500–2400, preferably 1700–2100. The degree of hydrolysis is not particularly limited, but is typically 88%–99%. The second polyvinyl alcohol has a degree of polymerization of 300–700, preferably 300–500. The degree of hydrolysis is not particularly limited, but is typically 88%–99%. When the first polyvinyl alcohol comprises 100 parts, the second polyvinyl alcohol comprises 50–100 parts; preferably, the second polyvinyl alcohol comprises 50–80 parts.

[0011] When the first polyvinyl alcohol in the raw material is 100 parts, the amount of formaldehyde aqueous solution added is 90-150 parts, and the formaldehyde concentration is 37 wt%. Preferably, the amount of formaldehyde added is 120-130 parts. When the first polyvinyl alcohol in the raw material is 100 parts, the amount of aliphatic dialdehyde added is 0.2-0.6 parts, and the aliphatic dialdehyde concentration is 50%. Preferably, the amount of aliphatic dialdehyde added is 0.4-0.6 parts.

[0012] Insufficient formaldehyde results in an incomplete cross-linking network, causing the sponge to resemble a gel. Increasing the formaldehyde content further reduces the pore size, which, while meeting emulsion separation requirements, often leads to an excessive decrease in hydrophilicity, resulting in extremely low water flux during oil-water separation, making it difficult to meet separation requirements. Insufficient aliphatic dialdehyde can cause two problems: firstly, it fails to effectively reduce formaldehyde usage; secondly, its impact on pore size is limited, and it can cause long-axis stretching of the pores, deforming them from normal circles to ellipses. Excessive addition results in excessively small pores, which, while meeting oil-water separation requirements, also leads to insufficient water flux.

[0013] Aliphatic dialdehydes can be one of glyoxal, succinaldehyde, glutaraldehyde, and trimethylglutaraldehyde. Considering reactivity, water solubility, and migration, succinaldehyde and glutaraldehyde are preferred, with glutaraldehyde being the most preferred.

[0014] Because formaldehyde has a small molecular weight, it tends to react with the two adjacent hydroxyl groups on the polyvinyl alcohol (PVA) molecular chain, undergoing intramolecular condensation to form a stable six-membered ring. Aliphatic dialdehydes, on the other hand, have a relatively large molecular weight and two terminal aldehyde groups, making them more likely to react with hydroxyl groups on different PVA molecular chains, linking the different chains together and reducing the distance between them, thus acting as cross-linking bridges. This process leads to the formation of a more complex porous framework structure. As the reaction proceeds, the remaining unreacted PVA continues to react along the framework; therefore, even a very small amount of aliphatic dialdehyde can alter the pore structure of a sponge.

[0015] When the first polyvinyl alcohol in the raw material is 100 parts, the amount of sulfuric acid added is 30-50 parts, and the sulfuric acid concentration is 98%. If the amount of sulfuric acid is too small, the acetal reaction between PVA and the two aldehydes will be slow, the cross-linked network will not be fully formed, and the sponge will be gel-like.

[0016] The preparation method for this microporous sponge material is not particularly limited and may include the following steps:

[0017] (1) Dissolve a certain mass fraction of the first polyvinyl alcohol and the second polyvinyl alcohol in deionized water to obtain two polyvinyl alcohol aqueous solutions;

[0018] (2) Then mix the two polyvinyl alcohol aqueous solutions evenly, and add 37wt% formaldehyde, 50wt% aliphatic dialdehyde and 98wt% sulfuric acid in a predetermined mass fraction. Stir for 30 minutes to mix evenly to obtain a mixed reaction solution.

[0019] (3) Then transfer the mixed reaction solution into the mold and place the mold in an oven at 80°C for 5 hours to cure; clean with deionized water to obtain microporous sponge material.

[0020] The microporous hydrophilic sponge material prepared by this invention can be used for emulsion separation, with an average pore size of 5–15 μm and an emulsion separation efficiency greater than 95%; the water flux is greater than 4000 L / h. -1 m -2 bar -1 This invention, by adding a very small amount of aliphatic dialdehyde, not only effectively reduces the pore size but also significantly reduces the amount of formaldehyde used in the reaction process. Thus, a microporous sponge with suitable pore size and high light water content is prepared, which cannot be obtained using formaldehyde alone. The prepared hydrophilic sponge material can be used in fields such as emulsion separation. Attached Figure Description

[0021] Figure 1 The ultraviolet spectra of xylene / water emulsions at different concentrations, and the standard curve for linear fitting of emulsion concentration and absorbance;

[0022] Figure 2 Scanning electron microscope image of the polyvinyl alcohol light water microporous sponge material prepared in Example 2; Detailed Implementation

[0023] The technical solution of the present invention will be further described and illustrated below through specific embodiments, but the present invention is not limited to the embodiments described. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commonly used raw materials in the art, and the methods used in the embodiments are all conventional methods in the art.

[0024] The testing methods for pore size, porosity, separation efficiency, and water flux are as follows.

[0025] Pore ​​size: The average pore size of the sponge was obtained by statistically analyzing the SEM images of the sponge using Image-Pro Plus 6.0 software.

[0026] Porosity: Polyvinyl alcohol sponges were cut into regular cubic samples and completely dried using a freeze dryer to measure their volume. The sponges were then immersed in beakers filled with water to promote complete water absorption. Afterward, the absorbent sponges were placed on the support of a density balance to measure their mass in water. Finally, the sponges were removed from the water, and their mass in air filled with absorbed water was measured. Each set of sponges was measured five times, and the results can be calculated using the following formula:

[0027] F=(m1-m2)g=ρ w gV0

[0028]

[0029]

[0030]

[0031] Where F is the buoyancy force on the sponge; P is the porosity of the sponge; ρ is the apparent density of the sponge; W is the water absorption rate of the sponge; ρ w It is the density of water, with a value of 1 g / cm³. 3 m0 is the mass of the dry sponge; m1 is the mass of the absorbent sponge in the air; m2 is the mass of the absorbent sponge in water; V0 is the volume of the absorbent sponge; V1 is the volume of the internal pores of the sponge; V2 is the volume of the dry sponge.

[0032] Separation efficiency: Emulsion separation was characterized using standard samples. The standard sample used xylene as the oil phase and OP-10 as the surfactant. One part xylene, 99 parts deionized water, and 0.1 parts OP-10 were stirred in a mechanical stirrer at 300 rpm for 4 hours to form a homogeneous and stable white emulsion. The emulsion was diluted to prepare oil phase concentrations of 1.0, 0.8, 0.6, 0.4, and 0.2 g / L xylene / water emulsions. Polyvinyl alcohol sponges were cut into cuboids with sides of 60 mm and a thickness of 5 mm and fixed between filter elements. The prepared emulsions were poured into funnels, and emulsion separation was performed using a vacuum pump at a pressure difference of 0.055 MPa. Using a UV-Vis spectrophotometer, with deionized water as a reference, the spectra of emulsions with different oil phase concentrations were tested. The maximum absorption wavelength of the emulsion was finally determined to be 265 nm. (Details follow...) Figure 1 As shown in (a). Figure 1 (b) A standard curve for xylene based on absorbance at the maximum absorption wavelength. The concentration of xylene in the filtrate after the separation process was measured using the standard curve. The separation efficiency was calculated using the following formula:

[0033]

[0034] Where R is the emulsion separation efficiency; C1 is the concentration of xylene in the original emulsion; and C2 is the concentration of xylene after emulsion separation.

[0035] Water flux:

[0036]

[0037] Where V is the volume of the emulsion after sponge filtration; A is the effective area of ​​the sponge for emulsion separation; T is the separation time; and P is the pressure applied by the vacuum pump.

[0038] Example 1

[0039] A method for preparing a microporous hydrophilic sponge material is as follows:

[0040] 100 parts by mass of PVA1799 and 50 parts by mass of PVA0388 were dissolved in a certain amount of distilled water to obtain two polyvinyl alcohol aqueous solutions; then the two polyvinyl alcohol aqueous solutions were mixed evenly to obtain a polyvinyl alcohol mixture containing 100 parts by mass of PVA1799, 50 parts by mass of PVA0388 and 750 parts by mass of deionized water.

[0041] Then, to the above polyvinyl alcohol mixture, add 123 parts by weight of 37 wt% formaldehyde and 0.5 parts by weight of 50 wt% glutaraldehyde. Also add 47 parts by weight of 98% sulfuric acid diluted with deionized water. Stir for 30 minutes to mix thoroughly, obtaining a mixed reaction solution. During the mixing process, continue to add an appropriate amount of deionized water to this mixed reaction solution, so that the total deionized water content in the mixed reaction solution is 1200 parts by weight.

[0042] The mixed reaction solution was then transferred into a mold, and the mold was placed in an oven at 80°C for 5 hours to cure. After neutralization and cleaning, polyvinyl alcohol microporous sponge material was obtained.

[0043] Example 2

[0044] 100 parts by mass of PVA1799 and 67 parts by mass of PVA0388 were dissolved in a certain amount of distilled water to obtain two polyvinyl alcohol aqueous solutions; then the two polyvinyl alcohol aqueous solutions were mixed evenly to obtain a polyvinyl alcohol mixture containing 100 parts by mass of PVA1799, 67 parts by mass of PVA0388 and 900 parts by mass of deionized water.

[0045] Then, to the above polyvinyl alcohol mixture, add 123 parts by weight of 37 wt% formaldehyde and 0.5 parts by weight of 50 wt% glutaraldehyde. Also add 47 parts by weight of 98% sulfuric acid diluted with deionized water. Stir for 30 minutes to mix thoroughly, obtaining a mixed reaction solution. During the mixing process, continue to add an appropriate amount of deionized water to this mixed reaction solution, so that the total deionized water content in the mixed reaction solution is 1200 parts by weight.

[0046] The mixed reaction solution was then transferred into a mold, and the mold was placed in an oven at 80°C for 5 hours to cure. After neutralization and cleaning, polyvinyl alcohol microporous sponge material was obtained.

[0047] Example 3

[0048] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the mass fraction of PVA0388 is 100 parts by mass, while the rest are the same as in Example 2.

[0049] Comparative Example 1

[0050] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the mass fraction of PVA0388 is 25 parts by mass, while the rest are the same as in Example 2.

[0051] Comparative Example 2

[0052] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the mass fraction of PVA0388 is 150 parts by mass, while the rest are the same as in Example 2.

[0053]

[0054] Examples 1-3 have an average pore size of 5-15 μm, an emulsion separation efficiency greater than 95%, and a water flux greater than 4000 L / h. - 1 m -2 bar -1 The scanning microscope image of Example 2 is shown below. Figure 2 As shown, the scanning microscope images of the other embodiments are similar, demonstrating that the microporous hydrophilic sponge material prepared in this application has high porosity, emulsion separation efficiency, and water flux.

[0055] Examples 1-3 were prepared under the same conditions, except for the increasing mass fraction of PVA0388. The mass fractions of PVA0388 were 50, 67, and 100 parts by mass, respectively. As the mass fraction increased, the pore size gradually increased, the emulsion separation efficiency gradually decreased, while the water flux continuously increased. Based on the experimental data, Example 2 achieved the best balance between emulsion separation efficiency and water flux.

[0056] The average pore size of Comparative Example 1 was too small, resulting in a low water flux despite its emulsion separation efficiency of 99.1%; while the emulsion separation efficiency of Comparative Example 2 was only 88.2%.

[0057] Example 4

[0058] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the formaldehyde solution has a mass fraction of 150 parts, while the rest are the same as in Example 2.

[0059] Example 5

[0060] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the formaldehyde solution comprises 90 parts by mass, while the rest are the same as in Example 2.

[0061] Comparative Example 3

[0062] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the formaldehyde solution has a mass fraction of 180 parts, while the rest are the same as in Example 2.

[0063] Comparative Example 4

[0064] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that the formaldehyde solution has a mass fraction of 80 parts, while the rest are the same as in Example 2.

[0065]

[0066] Comparing Examples 2, 4, and 5 longitudinally, the higher the mass fraction of formaldehyde solution, the smaller the pore size. This is mainly because as the amount of formaldehyde increases, the number of cross-linking points per unit volume also increases, making the cross-linked network's skeletal structure denser and thus reducing the pore size. Furthermore, the increase in formaldehyde content also reduces the number of remaining hydroxyl groups in the sponge, affecting its hydrophilicity.

[0067] As shown in Comparative Example 3, as the formaldehyde content increased to 180 parts by mass, the pore size of the sponge decreased to 3.5 μm. Despite its extremely high emulsion separation efficiency, its water flux was only 2100 L / h. -1 m -2 bar -1

[0068] As shown in Comparative Example 4, when the formaldehyde content was reduced to 80 parts by mass, normal microporous sponges could not be prepared; only gel-like substances could be obtained. It was impossible to measure their pore size, separation efficiency, and water flux. This was mainly because the amount of formaldehyde added was insufficient, resulting in insufficient cross-linking and the inability to form a network skeleton structure.

[0069] Example 6

[0070] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: the 50wt% glutaraldehyde solution is 0.2 parts by mass, while the rest are the same as in Example 2.

[0071] Example 7

[0072] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: the 50wt% glutaraldehyde solution is 0.6 parts by mass, while the rest are the same as in Example 2.

[0073] Comparative Example 5

[0074] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: the 50wt% glutaraldehyde solution is 0.1 parts by mass, and the rest are the same as in Example 2.

[0075] Comparative Example 6

[0076] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: the 50wt% glutaraldehyde solution is 0.65 parts by mass, while the rest are the same as in Example 2.

[0077]

[0078] Comparing Examples 2, 6, and 7 longitudinally, the addition of only 0.2–0.6 parts by mass of glutaraldehyde solution resulted in a very drastic reduction in pore size. Because formaldehyde has a small molecular weight, it tends to react with the two adjacent hydroxyl groups on the polyvinyl alcohol (PVA) molecular chain, undergoing intramolecular condensation to form a stable six-membered ring. Glutaraldehyde, with its relatively large molecular weight and two terminal aldehyde groups, is more inclined to react with hydroxyl groups on different PVA molecular chains, connecting the different chains and reducing the distance between them, thus acting as a cross-linking bridge. This process leads to the establishment of a more complex porous framework structure. As the reaction proceeds, the remaining unreacted PVA continues to react along the framework; therefore, even a very small amount of glutaraldehyde can alter the pore structure of the sponge.

[0079] As shown in Comparative Example 5, when the 50wt% glutaraldehyde solution is 0.1 parts by mass, the bridging between molecules is insufficient, the morphology of the bubbles is significantly deformed, and many irregular pore sizes appear, resulting in a final emulsion separation efficiency of only 80.7%.

[0080] As shown in Comparative Example 6, when the 50wt% glutaraldehyde solution is 0.65 parts by mass, the intermolecular bridging is excessive, the pore size of the bubbles decreases to 3.3 μm, and the water flux initially reaches 2230 L / h. -1 m -2 bar -1 .

[0081] Comparative Example 7

[0082] 100 parts by mass of PVA1799 and 67 parts by mass of PVA0388 were dissolved in a certain amount of distilled water to obtain two polyvinyl alcohol aqueous solutions; then the two polyvinyl alcohol aqueous solutions were mixed evenly to obtain a polyvinyl alcohol mixture containing 100 parts by mass of PVA1799, 67 parts by mass of PVA0388 and 900 parts by mass of deionized water.

[0083] Then, 123 parts by mass of 37 wt% formaldehyde were added to the above polyvinyl alcohol mixture. Then, 47 parts by mass of 98% sulfuric acid, diluted with deionized water, were also added. The mixture was stirred for 30 minutes to ensure homogeneity, resulting in a mixed reaction solution. During the mixing process, an appropriate amount of deionized water was continuously added to this mixed reaction solution, so that the total deionized water content in the mixed reaction solution was 1200 parts by mass.

[0084] The mixed reaction solution was then transferred into a mold, and the mold was placed in an oven at 80°C for 5 hours to cure. After neutralization and cleaning, polyvinyl alcohol microporous sponge material was obtained.

[0085] Comparative Example 8

[0086] A method for preparing a microporous hydrophilic sponge material differs from Comparative Example 7 in that: 37wt% of formaldehyde is used in 180 parts by mass, while the rest are the same as in Comparative Example 7.

[0087]

[0088] Comparative Examples 7 and 8, without the addition of aliphatic dialdehyde, showed a significantly larger pore size compared to Example 2 with the addition of glutaraldehyde, and the emulsion separation efficiency decreased to 45% and 75.8%, respectively. Comparative Examples 7 and 8 demonstrate that the pore size decreases with increasing formaldehyde content. Therefore, it can be inferred that by further increasing the formaldehyde content, for example to 305 parts by mass, the average pore size can be reduced to 5.1 μm. However, this leads to excessive consumption of hydroxyl groups in the sponge, resulting in decreased hydrophilicity and extremely low water flux, even less than 1000 L / h. -1 m -2 bar -1 .

[0089] Example 8

[0090] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: instead of using 0.5 parts by weight of a 50% glutaraldehyde solution, a 0.5 parts by weight of a 50 wt% butyraldehyde solution is used; otherwise, the method is the same as in Example 2.

[0091] Comparative Example 9

[0092] A method for preparing a microporous hydrophilic sponge material differs from Example 2 in that: instead of using 0.5 parts by weight of a 50% glutaraldehyde solution, a 0.5 parts by weight of a 50 wt% adipaldehyde solution is used; otherwise, the method is the same as in Example 2.

[0093]

[0094] In a longitudinal comparison of Examples 2 and 8, the 50% glutaraldehyde solution was changed to a 50% succinaldehyde solution. As can be seen from the above data, succinaldehyde is not as effective as glutaraldehyde in reducing pore size.

[0095] As can be seen from Example 2 and Comparative Example 9, after adding 50 wt% hexadialdehyde solution, the foam cells underwent irregular deformation, and the emulsion separation efficiency decreased to 72.5%.

Claims

1. A microporous hydrophilic sponge material, characterized in that, The microporous hydrophilic sponge is a polyvinyl alcohol sponge, obtained by reacting the following raw material system, which, by weight, includes the following raw materials: 100 parts of first polyvinyl alcohol, 50-100 parts of second polyvinyl alcohol, 500-800 parts of deionized water, 90-150 parts of formaldehyde aqueous solution, 0.2-0.6 parts of aliphatic dialdehyde aqueous solution, and 30-50 parts of sulfuric acid; the degree of polymerization of the first polyvinyl alcohol is 1500-2400; the degree of polymerization of the second polyvinyl alcohol is 300-700; the concentration of the formaldehyde aqueous solution is 37 wt%; the concentration of the aliphatic dialdehyde aqueous solution is 50 wt%; and the concentration of sulfuric acid is 98 wt%; the aliphatic dialdehyde is one of butyraldehyde and glutaraldehyde.

2. In the microporous hydrophilic sponge material according to claim 1, when the first polyvinyl alcohol is 100 parts, the second polyvinyl alcohol is 50-80 parts.

3. In the microporous hydrophilic sponge material according to claim 1, the amount of formaldehyde added is 120-130 parts, and the amount of aliphatic dialdehyde added is 0.4-0.6 parts.

4. In the microporous hydrophilic sponge material according to claim 1, the aliphatic dialdehyde is glutaraldehyde.

5. The method for preparing the microporous hydrophilic sponge material according to claim 1, comprising the following steps: (1) Dissolve a certain mass fraction of the first polyvinyl alcohol and the second polyvinyl alcohol in deionized water to obtain two polyvinyl alcohol aqueous solutions; (2) Then mix the two polyvinyl alcohol aqueous solutions evenly, and add 37wt% formaldehyde, 50wt% aliphatic dialdehyde and 98wt% sulfuric acid in a predetermined mass fraction. Stir for 30 minutes to mix evenly to obtain a mixed reaction solution. (3) Then transfer the mixed reaction solution into the mold and place the mold in an oven at 80°C for 5 hours to cure; clean with deionized water to obtain microporous sponge material.

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