A fast-setting hydrogel, its preparation method and application

Abstract

A rapid-setting hydrogel, its preparation method, and its application are disclosed. The hydrogel comprises 40 wt.%–60 wt.% of solution A and 60 wt.%–40 wt.% of solution B. Solution A contains an aqueous solution of polyvinyl alcohol, microcrystalline cellulose, and microcapsule particles. The microcapsule particles consist of encapsulating material and Bacillus bacteria encapsulated within the encapsulating material. The melting temperature of the encapsulating material is between 30 and 50°C. Solution B is an aqueous solution of sodium tetraborate. This hydrogel can spontaneously form a hydrogel barrier layer in situ beneath the soil layer and effectively treats infiltrated pollutants, improving the ecological environment of contaminated soil.

Description

Technical Field

[0001] This invention relates to the field of emergency soil barrier remediation, specifically to a fast-setting hydrogel, its preparation method, and its application. Background Technology

[0002] Currently, there are few emergency remediation methods for severely contaminated soil caused by sudden heavy metal leaks. Conventional physical remediation, chemical remediation, and biological remediation methods each have their own drawbacks and are not suitable for remediating contaminated soil in sudden pollution events. Rapidly preventing the vertical diffusion of various pollutants has always been a challenge; however, ex-situ remediation cannot address pollution in a timely manner. Summary of the Invention

[0003] Technical problem solved: In view of the above-mentioned technical problem, the present invention provides a fast-setting hydrogel, its preparation method and application. The hydrogel can spontaneously form a hydrogel barrier layer in situ below the soil layer and can effectively treat infiltrated pollutants and improve the ecological environment of polluted soil.

[0004] Technical solution: A fast-setting hydrogel, composed of 40wt.%-60wt.% of solution A and 60wt.%-40wt.% of solution B, wherein solution A contains polyvinyl alcohol aqueous solution, microcrystalline cellulose and microcapsule particles, wherein the microcapsule particles are composed of encapsulating material and Bacillus bacteria encapsulated in the encapsulating material, and the melting temperature of the encapsulating material is between 30-50℃; solution B is sodium tetraborate aqueous solution.

[0005] Preferably, the encapsulating material is one of beeswax, petrolatum, and petroleum wax.

[0006] Preferably, the particle size of the microcapsule particles is between 50 μm and 500 μm.

[0007] Preferably, in the above-mentioned solution A, the mass fraction of the polyvinyl alcohol aqueous solution is 80%, the mass fraction of the microcapsule particles is 10%, the mass fraction of the microcrystalline cellulose is 10%, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 10%-30%, and the total mass of the Bacillus accounts for 5%-15% of the total mass of the microcapsule particles.

[0008] Preferably, the concentration of sodium tetraborate in solution B is 0.01 mmol to 0.03 mmol.

[0009] The preparation method of the above hydrogel includes the following steps: (1) preparing a polyvinyl alcohol aqueous solution: dissolving polyvinyl alcohol completely in water at a temperature of 90-95℃, and cooling to obtain a polyvinyl alcohol aqueous solution, wherein the mass percentage of polyvinyl alcohol in the solution is 10%-30%; (2) preparing a sodium tetraborate aqueous solution: dissolving 0.01mmol-0.03mmol of sodium tetraborate completely in water, wherein the sodium tetraborate aqueous solution is solution B; (3) preparing microcapsule particles: preparing microcapsule particles containing Bacillus using a cooling method; (4) adding the microcapsule particles and microcrystalline cellulose into the polyvinyl alcohol aqueous solution and mixing them evenly to obtain solution A, wherein the mass fraction of the microcapsule particles is 10%.

[0010] The cooling method in step (3) above includes the following steps: Preparation of blend: Bacillus is dispersed in liquid culture medium and mixed with the encapsulating material. While stirring, the mixture is heated until the encapsulating material is completely melted to obtain a blend. The mixing ratio is controlled so that the mass fraction of Bacillus in the blend is between 5% and 15%. Granulation: The blend is added dropwise to pure water at 4-10℃. The blend solidifies into granules upon cooling. Washing: The granules are washed with pure water to remove the residual culture medium on their surface and then dried to obtain the microcapsule particles.

[0011] The above-mentioned hydrogels are used in emergency barrier remediation of site contamination.

[0012] The specific steps of the above application are as follows: a vertical shaft is set up, and liquid A and heated liquid B are injected into the target soil layer through a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0013] Preferably, the temperature of the heated liquid B is 30-50°C.

[0014] Beneficial Effects: Compared with ordinary hydrogels, the rapid-setting hydrogel prepared by this invention is simple to manufacture, has a fast gelation speed, and exhibits superior pollutant barrier performance, breaking through the traditional applications and forms of pollutant barrier in hydrogels. During the gelation process, some of the Bacillus bacteria contained within are released into the soil, while others cross-link within the hydrogel network. The encapsulating material also provides the energy required for Bacillus growth. The Bacillus degrades organic pollutants, solidifies heavy metal ions, and improves the ecological environment of contaminated soil. The rapid-setting hydrogel prepared by this invention combines barrier and remediation functions, is simple to operate, and can be widely applied in the field of emergency soil remediation. Detailed Implementation

[0015] The present invention will be further explained below with reference to specific embodiments. Example 1

[0016] This embodiment provides a rapid-setting hydrogel for emergency barrier remediation of site contamination and its application. It comprises a polyvinyl alcohol aqueous solution, microcrystalline cellulose, and petrolatum microcapsules dispersed in the polyvinyl alcohol aqueous solution as solution A, and a sodium tetraborate aqueous solution as solution B. The petrolatum microcapsules encapsulate Bacillus spores. Based on the total mass of the polyvinyl alcohol aqueous solution, the mass fraction of the petrolatum microcapsules is 10%, the mass fraction of the microcrystalline cellulose is 10%, and the mass fraction of the polyvinyl alcohol aqueous solution is 80%. The polyvinyl alcohol aqueous solution contains 10% polyvinyl alcohol, has a pH of 7, and the total mass of the Bacillus spores accounts for 5%-15% of the total mass of the petrolatum microcapsules. The sodium tetraborate aqueous solution contains 0.01 mmol of sodium tetraborate, and the heating temperature is 30°C.

[0017] Liquid A and heated liquid B are injected into the target soil layer using a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, rapidly forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0018] Its gelation time is 2 minutes, the petrolatum microcapsule particles dissolve by 30%, the porosity is 5%, and the stable permeation rate is 10. -6 m / s, effective diffusion coefficient 10 -4 cm 2 / s, the maximum migration distance of heavy metals is 40m after 60 days of Modflow simulation. Example 2

[0019] This embodiment provides a rapid-setting hydrogel for emergency barrier remediation of site contamination and its application. It comprises a polyvinyl alcohol aqueous solution, microcrystalline cellulose, and petroleum wax microcapsule particles dispersed in the polyvinyl alcohol aqueous solution as solution A, and a sodium tetraborate aqueous solution as solution B. The petroleum wax microcapsule particles encapsulate Bacillus. Based on the total mass of solution A, the mass fraction of petroleum wax microcapsule particles is 10%, the mass fraction of microcrystalline cellulose is 10%, and the mass fraction of the polyvinyl alcohol aqueous solution is 80%. The polyvinyl alcohol aqueous solution contains 10% polyvinyl alcohol, has a pH of 7, and the total mass of the Bacillus accounts for 5%-15% of the total mass of the petroleum wax microcapsule particles. The sodium tetraborate aqueous solution contains 0.01 mmol of sodium tetraborate, and the heating temperature is 30°C.

[0020] Liquid A and heated liquid B are injected into the target soil layer using a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, rapidly forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0021] Its gelation time is 3 minutes, the petroleum wax microcapsule particles dissolve by 38%, the porosity is 7%, and the stable permeation rate is 10. -5 m / s, effective diffusion coefficient 10-5 cm 2 / s, the maximum migration distance of heavy metals is 32m after 60 days of Modflow simulation. Example 3

[0022] This embodiment provides a rapid-setting hydrogel for emergency barrier remediation of site contamination and its application. Solution A consists of a polyvinyl alcohol aqueous solution, microcrystalline cellulose, and beeswax microcapsule particles dispersed in the polyvinyl alcohol aqueous solution; Solution B consists of a sodium tetraborate aqueous solution. The beeswax microcapsule particles encapsulate Bacillus. Based on the total mass of Solution A, the mass fraction of beeswax microcapsule particles is 10%, the mass fraction of microcrystalline cellulose is 10%, and the mass fraction of the polyvinyl alcohol aqueous solution is 80%. The polyvinyl alcohol aqueous solution contains 10% polyvinyl alcohol and has a pH of 7. The total mass of the Bacillus accounts for 5%-15% of the total mass of the beeswax microcapsule particles. The sodium tetraborate aqueous solution contains 0.01 mmol of sodium tetraborate, and the heating temperature is 30°C.

[0023] Liquid A and heated liquid B are injected into the target soil layer using a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, rapidly forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0024] Its gelation time is 30 seconds, the beeswax microcapsule particles dissolve by 50%, the porosity is 15%, and the stable permeation rate is 10. -6 m / s, effective diffusion coefficient 10 -7 cm 2 / s, the maximum migration distance of heavy metals is 23m after 60 days of Modflow simulation. Example 4

[0025] This embodiment provides a rapid-setting hydrogel for emergency barrier remediation of site contamination and its application. It comprises a polyvinyl alcohol aqueous solution, microcrystalline cellulose, and beeswax microcapsule particles dispersed in the polyvinyl alcohol aqueous solution as solution A, and a sodium tetraborate aqueous solution as solution B. The beeswax microcapsule particles encapsulate Bacillus. Based on the total mass of solution A, the mass fraction of beeswax microcapsule particles is 10%, the mass fraction of microcrystalline cellulose is 10%, and the mass fraction of the polyvinyl alcohol aqueous solution is 80%. The polyvinyl alcohol aqueous solution contains 20% polyvinyl alcohol and has a pH of 7. The total mass of the Bacillus accounts for 5%-15% of the total mass of the beeswax microcapsule particles. The sodium tetraborate aqueous solution contains 0.02 mmol of sodium tetraborate, and the heating temperature is 40°C.

[0026] Liquid A and heated liquid B are injected into the target soil layer using a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, rapidly forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0027] Its gelation time is 22s, the beeswax microcapsule particles dissolve by 90%, the porosity is 15%, and the stable permeation rate is 10. -7 m / s, effective diffusion coefficient 10 -7 cm 2 / s, the maximum migration distance of heavy metals is 21m after 60 days of Modflow simulation. Example 5

[0028] This embodiment provides a rapid-setting hydrogel for emergency barrier remediation of site contamination and its application. Solution A consists of a polyvinyl alcohol aqueous solution, microcrystalline cellulose, and beeswax microcapsule particles dispersed in the polyvinyl alcohol aqueous solution; Solution B consists of a sodium tetraborate aqueous solution. The beeswax microcapsule particles encapsulate Bacillus. Based on the total mass of Solution A, the mass fraction of beeswax microcapsule particles is 10%, the mass fraction of microcrystalline cellulose is 10%, and the mass fraction of the polyvinyl alcohol aqueous solution is 80%. The polyvinyl alcohol aqueous solution contains 30% polyvinyl alcohol and has a pH of 7. The total mass of the Bacillus accounts for 5%-15% of the total mass of the beeswax microcapsule particles. The sodium tetraborate aqueous solution contains 0.03 mmol of sodium tetraborate, and the heating temperature is 50°C.

[0029] Liquid A and heated liquid B are injected into the target soil layer using a vertical liquid-carrying pipe. Liquid A and liquid B diffuse laterally in the soil, meet and mix, and quickly produce a cross-linking reaction, rapidly forming a tight hydrogel layer at the bottom of the contaminated soil layer.

[0030] Its gelation time is 15 seconds, the beeswax microcapsule particles dissolve 100%, the porosity is 15%, and the stable permeation rate is 10. -10 m / s, effective diffusion coefficient 10 -7 cm 2 / s, the maximum migration distance of heavy metals is 20m after 60 days of Modflow simulation.

[0031] Based on the above experimental results, the hydrogel synthesized using the materials prepared in Example 5 has a fast gelation speed and a good barrier effect.

[0032] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. The application of hydrogels in emergency barrier and remediation of site contamination, characterized in that, Solution A consists of polyvinyl alcohol aqueous solution, microcrystalline cellulose, and beeswax microcapsule particles dispersed in the polyvinyl alcohol aqueous solution; solution B consists of sodium tetraborate aqueous solution; the beeswax microcapsule particles contain Bacillus subtilis; based on the total mass of solution A, the mass fraction of beeswax microcapsule particles is 10%, the mass fraction of microcrystalline cellulose is 10%, and the mass fraction of polyvinyl alcohol aqueous solution is 80%; the polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 30% by mass, the pH is 7, and the total mass of Bacillus subtilis accounts for 5%-15% of the total mass of the beeswax microcapsule particles; the sodium tetraborate aqueous solution contains 0.03 mmol of sodium tetraborate and is heated to 50°C; solution A and heated solution B are injected into the target soil layer using a vertical liquid-carrying tube, respectively. Solution A and solution B diffuse laterally in the soil, meet and mix, and rapidly produce a cross-linking reaction, quickly forming a tight hydrogel layer at the bottom of the contaminated soil layer.