Preparation method and application of interpenetrating network gel based on bentonite mineral

Abstract

The invention discloses a preparation method and application of interpenetrating network gel based on bentonite minerals, and belongs to the technical field of collapsible loess improvement. According to the prepared bentonite mineral interpenetrating network gel (BT-PAA / PEG / PVA), bentonite serves as a crosslinking node and cooperates with a PAA ion network, a PEG flexible chain segment and a PVA rigid hydroxyl network to construct a triple interpenetrating structure, high water absorption, compression resistance, salt resistance and long-term stability are achieved, the gel is applied to collapsible loess improvement, and the collapsible loess improvement effect is good. And gel particles and soil particles are combined to form an anchoring effect, so that the permeability of a soil body is reduced and the soil body is prevented from collapsing.

Description

Technical Field

[0001] The invention relates to the technical field of collapsible loess improvement, and in particular to a preparation method and application of an interpenetrating network gel based on bentonite minerals. Background Art

[0002] The collapsibility problem of loess refers to the weakening of the bonding force between loess particles due to the penetration and adsorption of water in a humid environment, resulting in significant volume deformation and a decrease in strength. This phenomenon is particularly prominent in the Loess Plateau and its surrounding areas, seriously affecting the stability and safety of infrastructure such as buildings, roads, and bridges. The deformation of collapsible soil can not only lead to uneven settlement of the foundation, causing cracks and deformation in buildings, but can also cause serious engineering accidents. The collapsibility problem of loess is a complex and severe engineering problem. Eliminating loess collapsibility is crucial to ensuring the long-term stability and safety of infrastructure.

[0003] In recent years, the use of gel materials to improve soil has become a research hotspot. Due to their excellent mechanical properties and water absorption, gels have become a key area of soil improvement. Through scientific improvement methods, loess stability can be significantly improved, providing reliable foundation support for infrastructure. At present, the methods for improving collapsible loess include dynamic compaction and replacement, improvement with resin materials or chemical curing agents, and reinforcement with microbial-induced calcium carbonate precipitation. However, all of the above schemes have some problems. For example, the dynamic compaction and replacement method has limited reinforcement effect and reinforcement depth for soils that are easily affected by water (collapsible loess), and cannot completely eliminate the collapsibility of the soil; the long-term stability of resin materials (SAP, BT-SAP, etc.) is poor, and the liquid absorption rate is too large, which cannot completely improve the contact state of soil particles and has limited improvement on soil properties (strength, impermeability, and water retention); the use of chemical curing agents (cement, calcium lignin sulfonate, etc.) to improve collapsible loess has a greater impact on plant growth and groundwater, easily leads to soil salinization, and is prone to cracks in the subsequent soil wetting process; the use of microbial-induced calcium carbonate precipitation to reinforce collapsible loess has high environmental requirements, low reinforcement efficiency, and a long reinforcement period.

[0004] Based on the above problems, a collapsible loess modifier based on bentonite mineral interpenetrating network gel was proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of an interpenetrating network gel based on bentonite minerals to solve the problems in the background technology.

[0006] To achieve the above object, the present invention provides a method for preparing an interpenetrating network gel based on bentonite minerals, comprising the following steps:

[0007] S1. Powdered sodium bentonite was placed in deionized water and magnetically stirred until no agglomerated particles were visible to obtain a bentonite dispersion solution A.

[0008] S2. dissolving acrylic acid monomer in deionized water, slowly adding sodium hydroxide solution dropwise in a water bath to neutralize the solution, adjusting the degree of neutralization of the solution to 50-90%, then adding bentonite dispersion solution A, and magnetically stirring to obtain a mixed solution B;

[0009] S3. Under gradient temperature conditions, polyethylene glycol and polyvinyl alcohol were added to the mixed solution B in stages, and the mixed solution C was obtained after magnetic stirring.

[0010] S4, dissolving N,N-methylenebisacrylamide in deionized water to obtain a crosslinker solution; dissolving potassium persulfate in deionized water to obtain an initiator solution;

[0011] S5, adding the crosslinker solution dropwise to the mixed solution C, stirring magnetically until mixed, and then slowly adding the initiator solution dropwise, stirring magnetically again to obtain a bentonite mineral interpenetrating network gel mixture, and then stopping stirring to precipitate the bentonite mineral interpenetrating network gel;

[0012] S6. Chop the bentonite mineral interpenetrating network gel into small pieces, soak them in a mixture of water and ethanol to wash away unreacted acrylic acid monomer to obtain gel fragments, dry them, crush them, and sieve them to obtain powdered bentonite mineral interpenetrating network gel.

[0013] Preferably, in said S1, the concentration of the bentonite dispersion solution A is 30-60 wt%.

[0014] Preferably, in S2, the neutralization degree of the solution is adjusted to 60-80%.

[0015] Preferably, in S2, the amount of deionized water is 1 to 3 times the amount of the acrylic acid monomer, the water bath temperature is lower than 30° C., and in the mixed solution B, the amount of bentonite is 10 to 50% of the mass of the acrylic acid monomer.

[0016] Preferably, the specific steps of S3 are: first, slowly heating the mixed solution B to 40-60° C., adding polyethylene glycol and magnetically stirring, stirring evenly, heating to 70-80° C., adding polyvinyl alcohol, and magnetically stirring to obtain a mixed solution C;

[0017] The amount of polyethylene glycol and polyvinyl alcohol used is 5-25 wt% of the acrylic acid monomer, and the molecular weight of polyethylene glycol is 4000-10000.

[0018] Preferably, in S1-S3, the magnetic stirring time is 10 to 20 minutes, and the stirring speed is 500 to 800 r / min.

[0019] Preferably, in S4, the amount of N,N-methylenebisacrylamide used is 0.1-0.5 wt % of the acrylic acid monomer, and the amount of potassium persulfate used is 0.5-2.5 wt % of the acrylic acid monomer.

[0020] Preferably, in S5, the magnetic stirring time after the cross-linking agent solution is added and the magnetic stirring time after the initiator solution is added are both 5 to 10 minutes, and the magnetic stirring speed is 500 to 1000 r / min.

[0021] Preferably, in S6, the volume ratio of water to ethanol is 1:9, and the soaking time is 10 to 30 minutes; the drying process adopts a gradient temperature increase, specifically: drying at 50°C for 2 hours, drying at 60°C for 4 hours, and drying at 80°C for 12 hours;

[0022] The crushing process is to use a jaw crusher to crush the particles to a size of ≤5mm and a ball mill to crush them to a size of D50 ≤50μm;

[0023] The sieving process is to sieve through a 100-mesh sieve.

[0024] The present invention also provides a bentonite mineral interpenetrating network gel, which is prepared by the above preparation method.

[0025] Preferably, the prepared bentonite mineral interpenetrating network gel is used as a modifier in improving collapsible loess, specifically, the powdered bentonite mineral interpenetrating network gel is added to the loess, and the addition amount is 0.25-1 wt % of the loess.

[0026] Therefore, the preparation method and application of the bentonite mineral interpenetrating network gel of the present invention have the following beneficial effects:

[0027] (1) The present invention breaks through the limitations of the traditional bentonite-PAA single network structure, uses bentonite as a cross-linking node, and synergizes the PAA ion network, PEG flexible chain segments and PVA rigid hydroxyl network to construct a triple interpenetrating structure. By regulating the neutralization degree of the acrylic acid monomer and premixing it with the bentonite dispersion, a multi-level interpenetrating structure is formed with PAA-bentonite as the ion cross-linking main network and PEG-PVA as the physical entanglement secondary network; the flexible chain segments of PEG and the rigid hydroxyl groups of PVA work synergistically to form hydrogen bonds and van der Waals force multiple action sites between the bentonite layers and the polymer interface, forming a physical / chemical cross-linked interpenetrating network, so that the gel has high water absorption, compression resistance, salt resistance and long-term stability.

[0028] (2) The present invention involves a gradient heating and step-by-step cross-linking process. PEG is first introduced at 40-60°C, utilizing its temperature-sensitive properties to promote molecular chain extension and pre-cross-linking with PAA. PVA is then added at 70-80°C to strengthen interfacial bonding through intercalation of hydroxyl groups with bentonite sheets. Finally, with the coordination of an initiator and a cross-linking agent, free radical polymerization and chemical cross-linking reactions are triggered in stages to form a hierarchical three-dimensional network. Through temperature-time coupling control, dynamic matching of bentonite dispersion, polymer intercalation, and cross-linking reactions is achieved, significantly increasing the cross-linking density of the gel and avoiding phase separation and local stress concentration.

[0029] (3) The present invention uses bentonite mineral interpenetrating network gel as an improver for the improvement of collapsible loess. The gel absorbs water and expands to fill soil pores, reducing permeability. When dehydrated, the network shrinks to provide support and prevent soil collapse. The gel particles combine with soil particles to form an "anchoring effect," improving shear strength and compressive modulus. Using natural bentonite as the skeleton reduces the amount of synthetic polymers used, lowering costs. The preparation process is free of toxic solvents, and the product is biodegradable and environmentally friendly.

[0030] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the SEM image of Example 1 of the present invention;

[0032] Figure 2 This is a SEM image of a comparative example of the present invention;

[0033] Figure 3 FTIR analysis charts of Examples 1-5 of the present invention and the comparative example;

[0034] Figure 4 The XRD patterns of Example 1 and the comparative example are shown below;

[0035] Figure 5 This is a graph showing the liquid absorption rate results of the products in Examples 1-5 of the present invention. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0038] Example 1

[0039] The preparation of bentonite mineral interpenetrating network gel comprises the following steps:

[0040] S1. Powdered sodium bentonite was added to deionized water and magnetically stirred at 600 rpm for 15 min until no agglomerated particles were visible, to obtain a 50 wt% bentonite dispersion solution A.

[0041] S2. Dissolve acrylic acid monomer in deionized water, add NaOH solution dropwise in a 25°C water bath for neutralization, adjust the neutralization degree of the solution to 70%, then add bentonite dispersion solution A, and magnetically stir at a rate of 600 r / min for 15 min to obtain a mixed solution B, wherein the mass of the acrylic acid monomer in the mixed solution B is 20 g, and the amount of bentonite is 20% of the mass of the acrylic acid monomer;

[0042] S3. First, slowly heat the mixed solution B to 50° C., add PEG-4000, and magnetically stir at a rate of 600 r / min for 15 minutes. The amount of PEG is 30 wt% of the acrylic acid monomer. Then, heat the mixture to 75° C., add PVA, and magnetically stir at a rate of 600 r / min for 15 minutes. The amount of PVA is 15 wt% of the acrylic acid monomer to obtain a mixed solution C.

[0043] S4, dissolving N,N-methylenebisacrylamide in deionized water to obtain a crosslinker solution; dissolving potassium persulfate (1 wt% of acrylic acid monomer) in deionized water to obtain an initiator solution;

[0044] S5. Add the crosslinker solution dropwise to the mixed solution C, and magnetically stir at a rate of 600 r / min for 8 minutes. The amount of N,N-methylenebisacrylamide is 0.1 wt% of the acrylic acid monomer; then slowly add the initiator solution dropwise, and magnetically stir at a rate of 800 r / min for 8 minutes. The amount of potassium persulfate is 1.5 wt% of the acrylic acid monomer; after stopping stirring, a bentonite mineral interpenetrating network gel is precipitated;

[0045] S6. Cut the bentonite mineral interpenetrating network gel into small pieces, soak them in a mixture of water and ethanol in a volume ratio of 1:9 for 20 minutes, wash away the unreacted acrylic acid monomer, and obtain gel fragments. Dry them at 50°C for 2 hours, 60°C for 4 hours, and 80°C for 12 hours to constant weight, and then crush them. First, use a jaw crusher to coarsely crush them to a particle size of ≤5 mm, and then place them in a ball mill to finely crush them to D50 ≤50 μm; after passing through a 100-mesh sieve, a powdery bentonite mineral interpenetrating network gel is obtained.

[0046] Example 2

[0047] The steps of this embodiment are the same as those of embodiment 1, except that the amount of N,N-methylenebisacrylamide is changed to 0.1 wt % of the acrylic acid monomer.

[0048] Example 3

[0049] The steps of this embodiment are the same as those of embodiment 1, except that the amount of N,N-methylenebisacrylamide is changed to 0.2 wt % of the acrylic acid monomer.

[0050] Example 4

[0051] The steps of this embodiment are the same as those of embodiment 1, except that the amount of N,N-methylenebisacrylamide is changed to 0.4 wt % of the acrylic acid monomer.

[0052] Example 5

[0053] The steps of this embodiment are the same as those of embodiment 1, except that the amount of N,N-methylenebisacrylamide is changed to 0.5 wt % of the acrylic acid monomer.

[0054] Comparative Example 1

[0055] Pure bentonite was used as a comparative example.

[0056] The bentonite mineral interpenetrating network gel obtained in Example 1 and the bentonite in Comparative Example 1 were observed by scanning electron microscopy. Figure 1 、 Figure 2 As shown, it can be seen that in Example 1, the polymer is intercalated between the bentonite layers, and the excess polymer forms a porous structure on the bentonite surface.

[0057] The products in the above examples 1-5 were subjected to infrared spectroscopy analysis. Figure 3 As shown, Example 1 is recorded as MBA0.3, Example 2 is recorded as MBA0.1, Example 3 is recorded as MBA0.2, Example 4 is recorded as MBA0.4, Example 5 is recorded as MBA0.5, and the comparative example is recorded as BT. -1 The wavenumber range is dominated by the hydroxyl (-OH) stretching vibration absorption peak. Pure bentonite (BT) exhibits a broad absorption band in this range, originating from its surface and interlayer hydroxyl groups. The addition of methylenebisacrylamide (MBA) significantly enhances the absorption peak intensity of the MBA0.1 to MBA0.5 curves, becoming more pronounced and broader with increasing MBA addition. This is because polymers such as polyvinyl alcohol (PVA) and polyethylene glycol (PEG) contain a large number of hydroxyl groups. After intercalation into the bentonite interlayers, the number of hydroxyl groups in the system increases and hydrogen bonds are formed with the bentonite, altering the hydroxyl vibrational environment and strongly suggesting successful polymer intercalation.

[0058] 1720cm -1 The stretching vibration peak of the free carboxyl group (-COOH) of polyacrylic acid appears in the sample curve with MBA added, but not in the BT curve, which proves the introduction of polymers such as polyacrylic acid; 1120cm -1The position and shape of the ether bond (COC) stretching vibration peak of polyethylene glycol nearby are basically stable after adding MBA. -1 The changes in the absorption peak range, the appearance of the carboxyl peak of polyacrylic acid, and the stability of the characteristic peak of bentonite indicate that with the addition of MBA, the polymer is successfully intercalated into the interlayers of bentonite, forming a bentonite-polymer intercalation system.

[0059] The bentonite mineral interpenetrating network gel obtained in Example 1 and the bentonite in Comparative Example 1 were subjected to X-ray diffraction. The results are as follows: Figure 4 As shown, it can be seen that the 001 peak of bentonite is 6.94°, and the 001 peak of MBA0.3 is 4.74°. According to the Bragg equation:

[0060] nλ=2d / sinθ;

[0061] Where n is the diffraction order (usually 1), λ is the X-ray wavelength (Cu Kα radiation: λ = 0.15406 nm); θ is the diffraction angle (in radians, 2θ needs to be converted to θ); d is the interplanar spacing (nm);

[0062] The calculation results show that the interlayer spacing of bentonite is 1.28nm and that of MBA0.3 is 1.87nm, indicating that the polymer is intercalated, resulting in an increase in the interlayer spacing of bentonite.

[0063] The bentonite mineral interpenetrating network gel obtained in Examples 1-5 was tested for liquid absorption, and the results were as follows: Figure 5 As shown in the figure, it can be seen that when the MBA content is 0.06g (i.e., 0.3wt% of the acrylic acid), the liquid absorption rate reaches the maximum. As the MBA content increases, the salt absorption rate gradually decreases. The optimal liquid absorption rate in the embodiment is 312.76g / g.

[0064] Application Examples

[0065] The powdered bentonite mineral interpenetrating network gel obtained in Example 5 was uniformly mixed into loess at 1 wt% of the dry mass of loess. The loess had a moisture content of 19% and a dry density of 1.62 g / cm 3 , add appropriate amount of water to the soil, dry mix for 3 minutes, then add water and wet mix for 5 minutes, compact it into a cylinder with a diameter of 3.91 cm and a height of 8 cm (compaction degree ≥ 95%), and test the performance after curing for 3 days.

[0066] Using pure loess as a comparative example, water sensitivity testing of collapsible loess was conducted. The results showed that the pure loess group collapsed after 5 seconds, with the soil presenting scattered particles and the water being relatively turbid, indicating that a large number of soil particles were scattered in the water. However, the experimental group incorporating powdered bentonite mineral interpenetrating network gel from the application example did not collapse until 30 seconds. After the collapse, the water was relatively clear and the collapsed blocks were large, indicating that the material provided effective support for the soil structure and produced an effective bonding effect on the soil, significantly reducing the water sensitivity of the loess.

[0067] Therefore, the present invention provides a preparation method and application of an interpenetrating network gel based on bentonite minerals, which uses bentonite exfoliated nanosheets as cross-linking nodes, and synergistically constructs a triple interpenetrating structure with PAA ion network, PEG flexible chain segments and PVA rigid hydroxyl network, and has high water absorption, compression resistance, salt resistance and long-term stability. It is applied to the improvement of collapsible loess, so that the gel particles are combined with soil particles to form an "anchoring effect", reducing soil permeability and preventing soil collapse.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an interpenetrating network gel based on bentonite minerals, characterized in that: The following steps are involved: S1. Powdered sodium bentonite was placed in deionized water and magnetically stirred until no agglomerated particles were visible to obtain a bentonite dispersion solution A. S2. dissolving acrylic acid monomer in deionized water, slowly adding sodium hydroxide solution dropwise in a water bath to neutralize the solution, adjusting the degree of neutralization of the solution to 50-90%, then adding bentonite dispersion solution A, and magnetically stirring to obtain a mixed solution B; S3. Under gradient temperature conditions, polyethylene glycol and polyvinyl alcohol were added to the mixed solution B in stages, and the mixed solution C was obtained after magnetic stirring. S4, dissolving N,N-methylenebisacrylamide in deionized water to obtain a crosslinker solution; dissolving potassium persulfate in deionized water to obtain an initiator solution; S5, adding the crosslinker solution dropwise to the mixed solution C, stirring magnetically until mixed, and then slowly adding the initiator solution dropwise, stirring magnetically again, and stopping stirring to precipitate the bentonite mineral interpenetrating network gel; S6. Chop the bentonite mineral interpenetrating network gel into small pieces, soak them in a mixture of water and ethanol to wash away unreacted acrylic acid monomers, dry them, grind them, and sieve them to obtain powdered bentonite mineral interpenetrating network gel.

2. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: In the above S1, the concentration of the bentonite dispersion solution A is 30-60 wt%.

3. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: In the above-mentioned S2, the amount of deionized water is 1 to 3 times the amount of the acrylic acid monomer, the water bath temperature is lower than 30° C., and the amount of bentonite in the mixed solution B is 10 to 50% of the mass of the acrylic acid monomer.

4. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: The specific steps of S3 are: first, slowly heating the mixed solution B to 40-60° C., adding polyethylene glycol and magnetically stirring, stirring evenly, heating to 70-80° C., adding polyvinyl alcohol, and magnetically stirring to obtain a mixed solution C; The amount of polyethylene glycol and polyvinyl alcohol used is 5-25 wt% of the acrylic acid monomer, and the molecular weight of polyethylene glycol is 4000-10000.

5. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: In S1-S3, the magnetic stirring time is 10-20 min, and the stirring speed is 500-800 r / min.

6. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: In the above S4, the amount of N,N-methylenebisacrylamide is 0.1-0.5 wt % of the acrylic acid monomer, and the amount of potassium persulfate is 0.5-2.5 wt % of the acrylic acid monomer.

7. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, characterized in that: In the above S5, the magnetic stirring time after the cross-linking agent solution is added and after the initiator solution is added is 5 to 10 minutes, and the magnetic stirring speed is 500 to 1000 r / min.

8. The method for preparing a bentonite mineral interpenetrating network gel according to claim 1, wherein: In the S6, the volume ratio of water to ethanol is 1:9, and the soaking time is 10 to 30 minutes; the drying process adopts a gradient temperature increase, specifically: drying at 50°C for 2 hours, drying at 60°C for 4 hours, and drying at 80°C for 12 hours.

9. A bentonite mineral interpenetrating network gel, characterized in that: The bentonite mineral interpenetrating network gel is prepared by the preparation method according to any one of claims 1 to 8.

10. The bentonite mineral interpenetrating network gel according to claim 9, characterized in that: The prepared bentonite mineral interpenetrating network gel is applied to the improvement of collapsible loess, specifically, the powdered bentonite mineral interpenetrating network gel is mixed into the loess, and the mixing amount is 0.25-1wt% of the loess.

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