Geogrid capable of absorbing water and adsorbing heavy metals as well as preparation method and construction method of geogrid

Abstract

The invention discloses a geogrid capable of absorbing water and adsorbing heavy metal and a preparation method and a construction method thereof, the geogrid comprises geogrid ribs which are distributed in a crossed mode, one side of the geogrid is provided with a plug, and the other side of the geogrid is provided with a clamping hole matched with the plug; the geogrid is prepared from polyethylene, modified polyacrylamide, modified charcoal and a surfactant according to the mass ratio of 70: 15: 15: (0.5-1). The preparation method comprises the following steps: adding pretreated biochar into a silane coupling agent solution, stirring for reaction, and drying to obtain modified biochar; carrying out graft modification on polyacrylamide to obtain modified polyacrylamide; polyethylene, the modified polyacrylamide, the modified biochar and a surfactant are mixed, and geogrid ribs are formed; the geogrid rib is used for producing the geogrid with the buckle and the rapid fixing function, and comprises a plug and a clamping hole. According to the invention, the polyacrylamide and the charcoal are added, so that the water absorption and water retention capacities of the geogrid are improved.

Description

Technical Field

[0001] The invention relates to a geogrid and a preparation method and a construction method thereof, in particular to a geogrid capable of absorbing water and heavy metals and a preparation method and a construction method thereof. Background Art

[0002] As an important geosynthetics, geogrids have been widely used in engineering fields such as road construction, slope protection, soil and water conservation, and ecological restoration. Traditional geogrids usually use polyethylene or polypropylene as the main material, which has good mechanical properties and chemical stability. However, with the increasing demand for environmental protection, efficient construction and soil improvement functions in modern engineering, traditional geogrids have gradually exposed the following shortcomings: the surface of traditional geogrids is smooth, lacks sufficient interfacial adhesion, and has poor fixation effect in the soil, especially in moist or loose soil environments, it is difficult to achieve fast and reliable fixation. Traditional geogrids are mainly fixed by external mechanical methods, have low natural bonding with the soil, and the construction efficiency is more dependent on the process flow, which increases the cost. Traditional geogrids are mostly drainage grids that focus on structural reinforcement and mechanical properties, and have limited effects on dryland moisture retention, ecological slope protection and vegetation restoration projects. In special applications such as contaminated soil remediation or mining area ecological restoration, existing materials cannot effectively adsorb heavy metals, organic pollutants or improve soil fertility, and lack support for ecological restoration. The functions of existing geogrids are mainly concentrated in mechanical properties and structural stability, and lack additional environmentally friendly functions, such as regulating soil pH, improving soil moisture retention capacity or promoting plant growth. Summary of the invention

[0003] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a geogrid that absorbs water and adsorbs heavy metals with strong environmental restoration capabilities. Another purpose of the present invention is to provide a method for preparing a green and environmentally friendly geogrid that absorbs water and adsorbs heavy metals. Another purpose of the present invention is to provide a construction method for a geogrid that absorbs water and adsorbs heavy metals that can be quickly reinforced.

[0004] Technical solution: The geogrid for absorbing water and heavy metals described in the present invention comprises cross-distributed geogrid ribs, a plug is arranged on one side of the geogrid, and a card hole matching the plug is arranged on the other side; the geogrid is made of polyethylene, modified polyacrylamide, modified biochar and surfactant in a mass ratio of 70:15:15:0.5-1; the modified polyacrylamide is polyethylene grafted maleic anhydride modified polyacrylamide, and the modified biochar is a silane coupling agent modified by a silane coupling agent.

[0005] The method for preparing a geogrid capable of absorbing water and heavy metals according to the present invention comprises the following steps:

[0006] Step 1, adding the pretreated biochar to the silane coupling agent solution, stirring and reacting at 55-65° C., after the reaction is completed, repeatedly washing with ethanol to remove the unreacted silane coupling agent, and drying to obtain modified biochar;

[0007] Step 2, grafting and modifying the hydrophilic polyacrylamide to obtain modified polyacrylamide, thereby enhancing the compatibility of polyacrylamide with polyethylene;

[0008] Step 3, polyethylene, modified polyacrylamide, modified biochar and surfactant are mixed in a mass ratio of 70:15:15:0.5-1 to form geogrid ribs;

[0009] Step 4: Use the geogrid ribs to produce a geogrid with a quick-fixing function with a clip, including a plug and a clip hole.

[0010] Furthermore, in step 1, the biochar is straw or bagasse. The silane coupling agent solution is an ethanol solution of 3-glycidylpropyltrimethoxysilane. The pretreatment is ultrasonic cleaning of the biochar with an ethanol solvent, drying at 75-85°C, and oxidative pretreatment with H2O2. Water and ammonia water are added during the stirring reaction, and a partial hydrolysis reaction is carried out while stirring to generate a silanol compound.

[0011] Furthermore, in step 2, the graft modification is performed by adding polyacrylamide, polyethylene grafted maleic anhydride and initiator benzoyl peroxide in a mass ratio of 69.5-69.9:15:15:0.1-0.5 in a twin-screw extruder, blending and reacting at 120-200° C. and mixing evenly, then cooling and crushing into powder to obtain modified polyacrylamide.

[0012] Furthermore, in step 3, the surfactant is sodium dodecyl sulfate and the mixing temperature is 120-180°C.

[0013] The construction method of a geogrid for absorbing water and heavy metals described in the present invention comprises the following steps: cleaning the site, determining the construction scope according to the design drawings, and marking the location for laying the geogrid; designing the layout dimensions of the geogrid, setting the amplitude spacing of the plugs and the card holes, and producing the geogrid according to the design specifications; laying the cushion layer, laying the geogrid flatly on the prepared foundation, and inserting the plugs at both ends of the geogrid into the geogrid at the designed position; and tensioning the geogrid.

[0014] Working principle: Polyacrylamide enhances the water absorption and water retention of geogrids, and is suitable for vegetation restoration or ecological restoration projects. Polyethylene provides the basic mechanical properties of geogrids to ensure their long-term performance. Biochar improves the adsorption and water retention of geogrids, and has the ecological benefit of improving the soil environment. Polyacrylamide is grafted with maleic anhydride by polyethylene. Through this modification process, the water solubility of polyacrylamide may be improved, and its compatibility with other materials is improved, especially with hydrophobic materials. In addition, grafting modification can also enhance the thermal stability and mechanical properties of polyacrylamide. Biochar is modified by silane coupling agent, which can improve the hydrophilicity of biochar, make it more efficient in water treatment, improve the adsorption capacity of pollutants such as organic matter, heavy metal ions, dyes, etc., improve the compatibility of biochar with other organic materials, inorganic materials or polymers, and improve the thermal stability and chemical stability of biochar.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0016] 1. By adding polyacrylamide and biochar, the water absorption and water retention capacity of geogrids is improved, which is suitable for projects such as vegetation slope protection and dryland ecological restoration;

[0017] 2. By adding biochar, geogrids have environmental restoration capabilities. After biochar is combined with heavy metals, metal ions are fixed in a stable carbon structure, reducing their migration and bioavailability. Biochar can also increase the content of soil organic matter and enhance water and fertilizer retention capabilities.

[0018] 3. Biochar comes from waste biomass, which reduces the carbon footprint of materials and conforms to the concept of green environmental protection;

[0019] 4. Compared with traditional geogrids, the plugs and holes at both ends of the geogrid can be quickly reinforced without additional binding. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the present invention;

[0021] Figure 2 It is a schematic diagram of the connection of the geogrid return bag of the present invention;

[0022] Figure 3 It is a schematic diagram of the connection between the plug 2 and the card hole 3 of the present invention. DETAILED DESCRIPTION

[0023] The materials, reagents, instruments, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources. The experimental methods without specific conditions in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer. Polyethylene is selected from linear low-density polyethylene (LLDPE) or high-density polyethylene (HDPE) with a melt index range of 0.5-3g / 10min as the matrix material. Polyacrylamide is selected from polyacrylamide powder with a molecular weight range of 5 million to 10 million, which has good water absorption and gelling properties.

[0024] like Figures 1 to 3 The geogrid is a network structure formed by cross-distributed geogrid ribs 1. A plug 2 is provided on one side of the geogrid, and a card hole 3 matching the plug 2 is provided on the other side. The plug 2 is arrow-shaped and its tip is designed so that it can be easily inserted into the card hole 3. The arrow-shaped plug 2 is used to connect the two ends of the geogrid or other geotechnical materials to ensure that the material does not move during construction or long-term use. The semicircular card hole 3 is a hole bent into a semicircle and is usually used in conjunction with a plug.

[0025] The construction method of geogrid includes the following steps:

[0026] S1. Clean the site, determine the construction scope according to the design drawings, and mark the location for laying the geogrid.

[0027] S2. Design the layout dimensions of the geogrid and set the width between the plug 2 and the hole 3.

[0028] S3. Send the designed rapid reinforcement geogrid drawings to the manufacturer for production according to the design specifications.

[0029] S4: Lay the cushion layer, lay the geogrid evenly on the prepared foundation, and insert the plugs 2 at both ends of the geogrid into the holes 3 at the designed positions. Ensure that the connection between the plugs 3 and the holes 3 is tight and firm without looseness.

[0030] S5. According to the design requirements, the geogrid shall be appropriately tensioned using tensioning equipment.

[0031] Example 1

[0032] A method for preparing a geogrid capable of absorbing water and heavy metals comprises the following steps:

[0033] Step 1: Ultrasonic clean the biochar with ethanol solvent to remove surface impurities, dry it at 75°C, and perform oxidation pretreatment with H2O2 to increase the density of surface hydroxyl groups. Add the pretreated biochar to the silane coupling agent solution and stir the reaction at 55°C. After the reaction is completed, wash it repeatedly with ethanol to remove the unreacted silane coupling agent, dry it at 60°C in a vacuum to obtain modified biochar, and crush it into powder. The biochar is prepared from straw by pyrolysis process, with an average particle size of 50nm and a surface area of ​​≥100m 2 / g, and the surface is rich in hydroxyl and carboxyl groups.

[0034] Step 2: The hydrophilic polyacrylamide is grafted and modified by polyethylene grafted maleic anhydride. In a twin-screw extruder, polyacrylamide, polyethylene grafted maleic anhydride and initiator benzoyl peroxide are added to the twin-screw extruder according to mass percentages of 70wt%, 29.5wt%, and 0.5wt%, and the temperature is controlled at 120°C, the screw speed is 50rpm, and a high-speed mixer is used to mix at room temperature for 10 minutes to ensure that the components are evenly distributed. The reaction and uniform mixing of the two materials are promoted by high-temperature blending, and then cooled and crushed into powder to obtain a uniform modified polyacrylamide.

[0035] Step 3: Mix polyethylene, modified polyacrylamide, modified biochar, and surfactant sodium dodecyl sulfate at a mass ratio of 69.5:15:15:0.5 at 120°C, feed the composite material particles into a single screw extruder, and extrude them into sheets through a special die head. The sheet thickness is 1.0 mm. Use laser cutting to process the sheet into a grid-like structure with a pore size of 10 mm. Form geogrid ribs 1.

[0036] Step 4: Stretch the grid-shaped geogrid ribs 1 at 80°C with a stretching ratio of 24 times to increase the tensile strength and toughness of the material. Plugs 2 and clamping holes 3 are set at both ends of the geogrid ribs 1 to facilitate quick connection and fixation at the construction site. A method for preparing a geogrid that absorbs water and heavy metals, comprising the following steps:

[0037] Example 2

[0038] Step 1: Ultrasonic clean the biochar with ethanol solvent to remove surface impurities, dry it at 85°C, and perform oxidation pretreatment with H2O2 to increase the density of surface hydroxyl groups. Add the pretreated biochar to the silane coupling agent solution and stir the reaction at 65°C. After the reaction is completed, repeatedly clean it with ethanol to remove the unreacted silane coupling agent, dry it at 100°C in a constant temperature drying oven to obtain modified biochar, and crush it into powder. The biochar is prepared from sugarcane bagasse by pyrolysis process, with an average particle size of 200nm and a surface area of ​​≥100m 2 / g, and the surface is rich in hydroxyl and carboxyl groups.

[0039] Step 2: The hydrophilic polyacrylamide is grafted and modified by polyethylene grafted maleic anhydride. In a twin-screw extruder, polyacrylamide, polyethylene grafted maleic anhydride and initiator benzoyl peroxide are added to the twin-screw extruder according to mass percentages of 70wt%, 29.5wt%, and 0.5wt%, and the temperature is controlled within the range of 200°C, the screw speed is 100rpm, and a high-speed mixer is used to mix at room temperature for 10 minutes to ensure that the components are evenly distributed. The reaction and uniform mixing of the two materials are promoted by high-temperature blending, and then cooled and crushed into powder to obtain a uniform modified polyacrylamide.

[0040] Step 3: Mix polyethylene, modified polyacrylamide, modified biochar, and surfactant sodium dodecyl sulfate at a mass ratio of 69.9:15:15:0.1 at 180°C, feed the composite material particles into a single screw extruder, and extrude them into sheets through a special die head. The sheet thickness is 3.0 mm. Use laser cutting to process the sheet into a grid-like structure with a pore size of 30 mm. Form geogrid ribs 1.

[0041] Step 4: Stretch the grid-shaped geogrid rib 1 at 100° C. with a stretching ratio of 24 times to increase the tensile strength and toughness of the material. Plugs 2 and clamping holes 3 are provided at both ends of the geogrid rib 1 to facilitate quick connection and fixing at the construction site.

[0042] Example 3

[0043] A method for preparing a geogrid capable of absorbing water and heavy metals comprises the following steps:

[0044] Step 1: Ultrasonic clean the biochar with ethanol solvent to remove surface impurities, dry it at 80°C, and perform oxidation pretreatment with H2O2 to increase the density of surface hydroxyl groups. Add the pretreated biochar to the silane coupling agent solution and stir the reaction at 60°C. After the reaction is completed, wash it repeatedly with ethanol to remove the unreacted silane coupling agent, dry it at 80°C in a vacuum drying oven to obtain modified biochar, and crush it into powder. The biochar is prepared from sugarcane bagasse by pyrolysis process, with an average particle size of 100nm and a surface area of ​​≥100m 2 / g, and the surface is rich in hydroxyl and carboxyl groups.

[0045] Step 2: The hydrophilic polyacrylamide is grafted and modified by polyethylene grafted maleic anhydride. In a twin-screw extruder, polyacrylamide, polyethylene grafted maleic anhydride and initiator benzoyl peroxide are added to the twin-screw extruder according to mass percentages of 70wt%, 29.5wt%, and 0.5wt%, and the temperature is controlled within the range of 160°C, the screw speed is 75rpm, and a high-speed mixer is used to mix at room temperature for 10 minutes to ensure that the components are evenly distributed. The reaction and uniform mixing of the two materials are promoted by high-temperature blending, and then cooled and crushed into powder to obtain a uniform modified polyacrylamide.

[0046] Step 3: Mix polyethylene, modified polyacrylamide, modified biochar, and surfactant sodium dodecyl sulfate at a mass ratio of 69.79:15:15:0.3 at 150°C, feed the composite material particles into a single screw extruder, and extrude them into sheets through a special die head. The sheet thickness is 2.0 mm. Use laser cutting to process the sheet into a grid-like structure with a pore size of 20 mm. Form geogrid ribs 1.

[0047] Step 4: Stretch the grid-shaped geogrid ribs 1 at 90°C with a stretching ratio of 24 times to increase the tensile strength and toughness of the material. Plugs 2 and clamping holes 3 are provided at both ends of the geogrid ribs 1 to facilitate quick connection and fixing at the construction site.

[0048] Comparative Example

[0049] The remaining steps of this comparative example are the same as those of Example 3, with the only difference being that the biochar in step 1 is not modified.

[0050] The geogrids obtained in Example 3 and the comparative example were tested for their heavy metal adsorption capacity, as shown in Table 1. The acidic environment will cause some oxygen-containing functional groups (such as carboxyl, hydroxyl, phenolic hydroxyl, etc.) to be partially deprotonated, which usually increases the density of negative charges on the surface of biochar. Therefore, the adsorption of positively charged metal ions (such as lead, cadmium, and copper) is usually stronger under acidic conditions. In an alkaline environment, functional groups such as carboxyl and phenolic hydroxyl on the surface of biochar will be more dissociated and negatively charged, which helps to enhance its adsorption of heavy metal ions. The increase in the negative charge density of biochar can enhance the adsorption of positively charged metal ions through ion exchange mechanisms and electrostatic adsorption.

[0051] Silane coupling agent modification significantly increases the adsorption capacity of heavy metals by introducing functional groups such as amino groups on the surface of biochar. After amino modification, the biochar has more hydrophilic functional groups on the surface, which helps to improve its adsorption capacity for water-soluble heavy metal ions. The modified biochar usually shows strong adsorption for specific heavy metal ions and can selectively remove harmful heavy metals according to environmental requirements. The modified biochar has lower environmental requirements and its heavy metal adsorption capacity in the three environments is basically the same.

[0052] Table 1 Comparison of adsorption capacity of unmodified biochar and biochar modified with silane coupling agent for heavy metals

[0053]

[0054] Table 2 Water absorption capacity of substrate

[0055] type Unmodified biochar (g / g) Biochar modified by silane coupling agent (g / g) Polyacrylamide (g / g) water 1-3 2-4 10-15

[0056] Table 2 shows the water absorption capacity of the geogrid obtained by mixing polyethylene, polyacrylamide powder and biochar particles in the proportion of 69.79%, 15% and 15% in Example 3 of the present invention, which is 4.3-8.6 g / g, and the water absorption capacity of the geogrid made of 1 mm thick is 400-800 g / m 2 , while traditional geogrids do not have the ability to absorb water.

[0057] Table 3 Heavy metal adsorption capacity of the composite geogrid substrate obtained in Example 3 of the present invention

[0058]

[0059] Table 3 is a comparison of the heavy metal adsorption capacity of the traditional base geogrid and the base geogrid after the polyethylene, polyacrylamide powder and biochar particles of the present invention are mixed in the proportions of 69.79%, 15% and 15%.

[0060] Table 4 Heavy metal adsorption capacity per square meter of the geogrid obtained in Example 3 of the present invention

[0061]

[0062] Table 4 shows the heavy metals that can be adsorbed per square meter by the 1 mm geogrid made of the composite material of Example 3 of the present invention, wherein the weight of the composite material substrate is 94 g / m 2 .

[0063] Polypropylene grafted maleic anhydride modified polyacrylamide provides more hydrophilic groups, which enhances the adsorption capacity of the composite material for water-soluble or polar pollutants (such as heavy metal ions). Biochar modified with silane coupling agent increases the surface active groups, which can strongly adsorb organic pollutants or heavy metal ions. The combination of the two may provide multiple adsorption sites on the same surface, enhancing the adsorption capacity for different types of pollutants. The modified polyacrylamide and biochar may make the surface of the composite material more porous and increase the adsorption surface area, which helps to improve the adsorption performance. Polypropylene grafted maleic anhydride modified polyacrylamide may improve the hydrophilicity of the composite material, while biochar modified with silane coupling agent may make the material more stable in water. The combination of the two may not only increase the adsorption capacity, but also improve the durability of the composite material in the water environment.

[0064] The geogrid obtained in Example 3 of the present invention increases the ability of the geogrid to absorb and store water and adsorb heavy metals by adding polyacrylamide and biochar, providing a better choice for ecological slope protection and vegetation restoration, soil and water conservation, dryland restoration and contaminated soil remediation projects.

[0065] Table 5 Performance comparison between traditional geogrid and composite geogrid of the present invention

[0066]

[0067] As shown in Table 5, the performance comparison between the conventional geogrid of the comparative example and the geogrid obtained in Example 3 of the present invention in different application scenarios is shown.

[0068] Table 6 shows the cost comparison between the conventional geogrid and the composite geogrid of the present invention.

[0069] The total cost of the composite geogrid is slightly higher than that of the 100% polyethylene geogrid, which increases by about 5% to 8%. However, the geogrid obtained in Example 3 of the present invention has improved water absorption and retention, heavy metal adsorption and rapid reinforcement capabilities, making the geogrid of the present invention suitable for more application scenarios, and playing the role of ecological slope protection and vegetation restoration, soil and water conservation, dry land restoration and contaminated soil restoration.

[0070] Table 6 Comparison of the cost of the conventional geogrid in the comparative example and the geogrid obtained in Example 3 of the present invention

[0071]

[0072] (Polyethylene: 8,000 yuan / ton; biochar: 3,000 yuan / ton; polyacrylamide: 13,000 yuan / ton).

Claims

1. A geogrid for absorbing water and heavy metals, characterized by: The invention comprises cross-distributed geogrid ribs (1), a plug (2) being arranged on one side of the geogrid, and a clamping hole (3) matching the plug (2) being arranged on the other side; the geogrid is made of polyethylene, modified polyacrylamide, modified biochar and surfactant in a mass ratio of 70:15:15:0.5-1; the modified polyacrylamide is polyethylene grafted maleic anhydride modified polyacrylamide, and the modified biochar is a silane coupling agent modified by a silane coupling agent.

2. A method for preparing a geogrid for absorbing water and heavy metals, characterized in that: The following steps are involved: Step 1, adding the pretreated biochar to the silane coupling agent solution, stirring and reacting at 55-65° C., after the reaction is completed, repeatedly washing with ethanol to remove the unreacted silane coupling agent, and drying to obtain modified biochar; Step 2, grafting and modifying the hydrophilic polyacrylamide to obtain modified polyacrylamide; Step 3, polyethylene, modified polyacrylamide, modified biochar and surfactant are mixed in a mass ratio of 70:15:15:0.5-1 to form geogrid ribs (1); Step 4: Use the geogrid ribs (1) to produce a geogrid with a snap-on quick-fixing function, including a plug (2) and a snap-on hole (3).

3. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 1, the biochar is straw or bagasse.

4. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 1, the silane coupling agent solution is an ethanol solution of 3-glycidylpropyltrimethoxysilane.

5. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 1, the pretreatment is to ultrasonically clean the biochar with an ethanol solvent, dry it at 75-85° C., and perform oxidation pretreatment with H2O2.

6. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 1, water and aqueous ammonia are added during the stirring reaction, and a partial hydrolysis reaction is carried out while stirring to generate a silanol compound.

7. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 2, the graft modification is to add polyacrylamide, polyethylene grafted maleic anhydride and initiator benzoyl peroxide in a mass ratio of 69.5-69.9:15:15:0.1-0.5 in a twin-screw extruder, blend and react at 120-200° C. and mix evenly, then cool and crush into powder to obtain modified polyacrylamide.

8. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 3, the surfactant is sodium dodecyl sulfate.

9. The method for preparing a geogrid capable of absorbing water and heavy metals according to claim 2, characterized in that: In the step 3, the mixing temperature is 120-180°C.

10. The construction method of a geogrid for absorbing water and heavy metals according to claim 1, characterized in that: The following steps are involved: Clean the site, determine the construction scope according to the design drawings, and mark the location of the geogrid; design the layout size of the geogrid, set the amplitude spacing of the plug (2) and the card hole (3), and produce the geogrid according to the design specifications; Lay the cushion layer, lay the geogrid evenly on the prepared foundation, and insert the plugs (2) at both ends of the geogrid into the geogrid at the designed position; Tensioning the geogrid.

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