A heavy metal contaminated soil remediation agent and preparation method thereof

Abstract

The invention discloses a heavy metal contaminated soil remediation agent and a preparation method thereof, wherein the heavy metal contaminated soil remediation agent, by weight, includes 25-70 parts of modified hydrotalcite nanosheets, 5-30 parts of cellulose ether, 5-55 parts of organic resin, and 70-260 parts of inorganic fillers, and the preparation raw materials of the modified hydrotalcite nanosheets include hydrotalcite, organic acid, aminosilane coupling agent and cross-linking agent. By adding modified hydrotalcite nanosheets, hydrotalcite is modified, and the modified hydrotalcite nanosheets and organic resins have internal connections, thereby constructing an organic-inorganic three-dimensional skeleton structure, which plays an interfacial stress transfer and dissipation role, thereby effectively improving the soil bearing capacity. By controlling the addition amount of the modified hydrotalcite nanosheets and the organic resin, the modified hydrotalcite nanosheets and the organic resin construct a robust organic-inorganic three-dimensional skeleton structure to improve the soil bearing capacity.

Description

Technical Field

[0001] The present invention relates to the field of soil remediation, and in particular to a heavy metal contaminated soil remediation agent and a preparation method thereof. Background Art

[0002] With the relocation and reconstruction of electroplating plants, landfills, chemical plants and other enterprises, the soil in the original industrial sites has absorbed too many heavy metals or organic pollutants. Heavy metal pollutants are prone to remain in the soil environment due to their potential, concealment, low mobility, persistence and non-biodegradability. After biological enrichment and biomagnification in the food chain, they will eventually endanger human health. The soil in the original industrial sites needs to be repaired in a timely manner.

[0003] The causes of heavy metal pollution in soil are complex, and usually present the following characteristics: multiple heavy metal pollutants coexist and are concentrated in large-scale distribution, which seriously affects the environmental quality. Vertical barrier is a commonly used technology in contaminated site remediation projects, which controls the spread of pollutants by vertically blocking the contaminated site. In actual projects, underground continuous walls are usually used for vertical barrier. However, underground continuous walls have problems such as easy seepage at the joints and circumferential flow of wall concrete, which affects the overall anti-seepage barrier performance. In response to multi-metal composite contaminated soil, it is urgent to develop easy-to-prepare, economical and green heavy metal contaminated soil remediation agents, so as to achieve reasonable control of the risk of soil pollutant migration. Summary of the invention

[0004] In order to overcome the above-mentioned shortcomings, one of the purposes of the present invention is to provide a heavy metal contaminated soil remediation agent that can achieve efficient solidification of contaminated soil and significantly improve soil bearing capacity.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is: a heavy metal contaminated soil remediation agent, which includes, by weight: 25-70 parts of modified hydrotalcite nanosheets, 5-30 parts of cellulose ether, 5-55 parts of organic resin, and 70-260 parts of inorganic filler.

[0006] Modified hydrotalcite nanosheets are added to modify the hydrotalcite, and the modified hydrotalcite nanosheets are internally connected with the organic resin, thereby constructing an organic-inorganic three-dimensional skeleton structure, which plays a role in interfacial stress transfer and dissipation, thereby effectively improving the soil bearing capacity. Exemplarily, the modified hydrotalcite nanosheets are in the range of 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 70 parts, or any two of them; the organic resin is in the range of 5 parts, 10 parts, 12 parts, 15 parts, 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, or any two of them.

[0007] Cellulose ether is added. Cellulose ether has good water absorption effect and generates a certain viscosity after water absorption, which is beneficial to improve the interfacial bonding force between inorganic materials. In addition, cellulose ether can complex heavy metal ions in the system. The cellulose ether molecular chain and the organic-inorganic three-dimensional skeleton formed by the modified hydrotalcite nanosheets and the organic resin are intertwined and entangled, which helps to trap heavy metal ions in the entire skeleton structure and solidify and seal the pollutants. Exemplarily, the cellulose ether is in the range of 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, 30 parts or any two of them.

[0008] Inorganic fillers are introduced. On the one hand, the generated gel products are interspersed in the pores of the contaminated soil, making the soil structure more compact and improving the soil strength for the functional application of the site; on the other hand, in response to the call for low carbon, inorganic fillers are solid waste fillers, which can make use of large amounts of solid waste as resources and achieve solid waste disposal. For example, the inorganic fillers are in the range of 70 parts, 75 parts, 100 parts, 125 parts, 150 parts, 175 parts, 200 parts, 225 parts, 250 parts, 260 parts or any two of them.

[0009] Furthermore, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.1-1.0).

[0010] Furthermore, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.3-0.8). By controlling the weight ratio of the modified hydrotalcite nanosheets to the organic resin, the modified hydrotalcite nanosheets and the organic resin construct a robust organic-inorganic three-dimensional skeleton structure. If there are too many modified hydrotalcite nanosheets and too little organic resin, the two cannot reach a grafting balance, the organic-inorganic three-dimensional skeleton is relatively loose, and the cohesion between soil particles decreases, so the mechanical properties of the soil decrease; if there are too few modified hydrotalcite nanosheets, the degree of damage to the water film on the surface of the soil particles decreases, the cohesion of the soil particles decreases, and the organic-inorganic three-dimensional skeleton in the soil is relatively loose, so the mechanical properties of the soil decrease. Exemplarily, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8 or a range consisting of any two of them.

[0011] Furthermore, the cellulose ether is at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose.

[0012] Furthermore, the cellulose ether is at least one of carboxymethyl cellulose and sodium carboxymethyl cellulose. Carboxymethyl cellulose or sodium carboxymethyl cellulose can cooperate with organic resin to make the soil intertwined to form a complex network, fix the soil particles inside, and absorb excess water, thereby adjusting the internal structure of the soil; it can also chelate heavy metal ions in the soil, thereby effectively fixing the heavy metal ions and achieving the effect of soil stabilization and solidification.

[0013] Furthermore, the organic resin is at least one of epoxy resin, polyacrylamide and polyvinyl alcohol.

[0014] Furthermore, the organic resin is polyacrylamide, which has a large molecular weight, a high viscosity coefficient, excellent water absorption capacity and chemical activity, and can be adsorbed on the surface of soil particles to increase the cohesion between soil particles, thereby regulating soil hydraulic properties and improving soil structural stability.

[0015] The aldehyde groups at both ends of the cross-linking agent glutaraldehyde react with the primary amine on the hydrotalcite modified by the silane coupling agent and the primary amine on the polyacrylamide, respectively, to construct an interpenetrating organic-inorganic three-dimensional skeleton structure, which can further improve the bearing capacity of the soil.

[0016] Furthermore, the inorganic filler is at least one of feldspar waste, red mud, fly ash, and steel slag. In the soil system, the gel material generated by the hydration of the inorganic filler will adhere to the organic-inorganic three-dimensional skeleton formed by the hydrotalcite modified by glutaraldehyde, polyacrylamide and silane coupling agent, fill the pores of the three-dimensional skeleton, make the soil system structure more compact, and better fix pollutants for the functional application of the site.

[0017] Furthermore, the raw materials for preparing the modified hydrotalcite nanosheets include, by weight, hydrotalcite, organic acid, aminosilane coupling agent and crosslinking agent.

[0018] Furthermore, the raw materials for preparing the modified hydrotalcite nanosheets include, by weight:

[0019] 20-60 parts of hydrotalcite, illustratively, the amount of hydrotalcite is 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts or any two thereof;

[0020] 20-80 parts of organic acid, illustratively, the organic acid is in the range of 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts or any two thereof;

[0021] 0.4-2.0 parts of aminosilane coupling agent, illustratively, the aminosilane coupling agent is in the range of 0.4 parts, 0.6 parts, 0.8 parts, 1.0 parts, 1.2 parts, 1.4 parts, 1.6 parts, 1.8 parts, 2.0 parts or any two thereof;

[0022] The proportions of hydrotalcite, organic acid, aminosilane coupling agent and crosslinking agent in the modified hydrotalcite nanosheet raw material are only for indicating the weight ratio relationship between hydrotalcite, organic acid and aminosilane coupling agent in the process of preparing the modified hydrotalcite nanosheet, and have no corresponding relationship with the proportions of modified hydrotalcite nanosheet added to the heavy metal contaminated soil remediation agent (25-70 parts).

[0023] Furthermore, the hydrotalcite is at least one of silicate calcium aluminum hydrotalcite, silicate magnesium aluminum hydrotalcite, carbonate calcium aluminum hydrotalcite, and carbonate magnesium aluminum hydrotalcite. Copper ions, zinc ions, etc. in the soil can replace calcium and magnesium ions in the modified hydrotalcite nanosheets by isomorphous substitution to achieve the effect of fixing heavy metal ions in the soil.

[0024] Furthermore, the organic acid is at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and terephthalic acid, preferably at least one of oxalic acid, malonic acid, and succinic acid. Oxalic acid can completely replace the carbonate in the hydrotalcite without destroying the layers of the hydrotalcite. The interlayer spacing of the hydrotalcite after intercalation becomes larger, and the crystallinity decreases, so that water molecules can easily enter the interlayer of the hydrotalcite, thereby destroying the layer structure of the hydrotalcite, and converting the two-dimensional structure of the hydrotalcite into a smaller size and larger specific surface area of ​​the hydrotalcite nanosheet. The hydrotalcite nanosheet is connected to contain a large number of carboxyl groups and has hydrophilicity.

[0025] Furthermore, the aminosilane coupling agent is at least one of KH550, KH602, JH-M902, and KH792, preferably at least one of KH602 and KH792.

[0026] Furthermore, the cross-linking agent is glutaraldehyde.

[0027] Another object of the present invention is to provide a method for preparing the heavy metal contaminated soil remediation agent as described above, comprising the following steps:

[0028] S4, dispersing the aminated hydrotalcite nanosheets in a solvent, adding a cross-linking agent, stirring, filtering, washing, and drying to obtain modified hydrotalcite nanosheets;

[0029] S5. Weigh the modified hydrotalcite nanosheets, cellulose ether, organic resin, and inorganic filler, and then mix the modified hydrotalcite nanosheets, cellulose ether, organic resin, and inorganic filler evenly to obtain a heavy metal contaminated soil remediation agent.

[0030] Furthermore, the solvent described in step S4 is selected from alcohol solvents, specifically, at least one of ethanol, propanol, and butanol can be selected, preferably ethanol.

[0031] Further, in step S4, the concentration of the cross-linking agent is 4-7wt%, which can be understood as, after the addition of the cross-linking agent, the cross-linking agent accounts for 4-7% of the total weight of ethanol. Exemplarily, the concentration of the cross-linking agent is in the range of 4wt%, 5wt%, 6wt%, 7wt% or any two thereof.

[0032] One end of the modified hydrotalcite nanosheet contains a large number of carboxyl groups and is easy to absorb water, which is hydrophilic, and the other end is a hydrophobic long chain of aminosilane coupling agent grafted glutaraldehyde, which is hydrophobic, so that the modified hydrotalcite nanosheet has amphiphilicity.

[0033] Furthermore, the preparation method of ammoniated hydrotalcite nanosheets is:

[0034] S1, dispersing the hydrotalcite in a solvent to obtain a hydrotalcite suspension;

[0035] S2, diluting an organic acid in a solvent to obtain an organic acid solution, adding the organic acid solution to the hydrotalcite suspension, stirring, filtering, washing, and drying to obtain hydrotalcite nanosheets;

[0036] S3, placing an aminosilane coupling agent in a solvent, adding hydrotalcite nanosheets, filtering, washing, and drying to obtain ammoniated hydrotalcite nanosheets.

[0037] Furthermore, the solvents described in steps S1, S2 and S3 are all selected from alcohol solvents, specifically, at least one of ethanol, propanol and butanol can be selected, preferably ethanol.

[0038] The beneficial effects of the present invention are:

[0039] 1) The soil stabilization agent obtained by compounding modified hydrotalcite nanosheets, cellulose ether, organic resin and solid waste filler can improve the soil carrying capacity and the pollutant solidification and sealing effect, and achieve the purpose of reasonable, efficient and low-carbon contaminated soil remediation and resource utilization.

[0040] 2) Add modified hydrotalcite nanosheets. On the one hand, the modified hydrotalcite nanosheets have "amphiphilic" properties, that is, one end contains a large number of carboxyl groups and hydrotalcite nanosheets with water absorption, which can destroy the water film originally formed on the surface of soil particles, reduce the repulsion between soil particles, increase the adhesion and agglomeration between soil particles, make soil particles adsorb each other, and improve the curing effect. The alkyl long chain grafted on the other end forms a hydrophobic film on the surface of soil particles, preventing water intrusion and effectively avoiding water penetration, thereby improving the stability and durability of the soil barrier layer. On the other hand, the aldehyde group at the end of the long chain can react with the amino group on polyacrylamide, expand and extend the cross-linked network of polyacrylamide, and construct an interpenetrating organic-inorganic three-dimensional skeleton structure. Thirdly, the carboxyl group grafted on the hydrotalcite can also complex with metal cations in the soil, which can effectively trap heavy metal ions in the organic-inorganic three-dimensional skeleton formed by the modified hydrotalcite nanosheets and organic resin, further playing a role in fixing metal pollutants.

[0041] 3) Adding cellulose ether. Cellulose ether has good water absorption effect and produces a certain viscosity after absorbing water, which is beneficial to improve the interfacial adhesion between inorganic materials. In addition, cellulose ether can complex heavy metal ions in the system. The cellulose ether molecular chain and the organic-inorganic three-dimensional skeleton formed by modified hydrotalcite nanosheets and organic resin are intertwined and entangled, which helps to trap heavy metal ions in the entire skeleton structure and solidify and seal the pollutants.

[0042] 4) Adding inorganic fillers, on the one hand, the generated gel products are interspersed in the pores of the contaminated soil, making the soil structure more compact and improving the soil strength to facilitate the functional application of the site; on the other hand, in response to the call for low-carbon development, inorganic fillers are used as solid waste fillers to recycle large amounts of solid waste and realize solid waste disposal.

[0043] 5) By controlling the weight ratio of modified hydrotalcite nanosheets and organic resin, the modified hydrotalcite nanosheets and organic resin construct a robust organic-inorganic three-dimensional skeleton structure, thereby improving the mechanical properties of the soil. DETAILED DESCRIPTION

[0044] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0045] Except as shown in the operating examples or otherwise indicated, all numbers used in the specification and claims to indicate the amount of ingredients, physicochemical properties, etc. are understood to be adjusted by the term "about" in all cases. Therefore, unless otherwise indicated, the numerical parameters listed in the above specification and the attached claims are approximate values, and those skilled in the art can use the teachings disclosed herein to seek to obtain the desired properties and appropriately change these approximate values. The use of numerical ranges expressed as endpoints includes all numbers within the range and any range within the range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4 and 5, etc.

[0046] An embodiment of the present invention provides a method for preparing a heavy metal contaminated soil remediation agent, which specifically comprises the following steps:

[0047] S1. Dispersing 20-60 parts of hydrotalcite in 100-300 parts of solvent to obtain a hydrotalcite suspension.

[0048] In some embodiments, the solvent in step S1 is an alcohol solvent, preferably at least one of ethanol, propanol, and butanol, and more preferably ethanol.

[0049] S2. Dilute 20-80 parts of an organic acid in 20-80 parts of a solvent to obtain an organic acid solution, then dropwise add the organic acid solution to the hydrotalcite suspension in a stirring state. After the dropwise addition is completed, continue stirring for 4-6 hours, filter, wash, and dry to obtain hydrotalcite nanosheets.

[0050] In some embodiments, the organic acid is at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and terephthalic acid, preferably at least one of oxalic acid, malonic acid, and succinic acid.

[0051] In some embodiments, the organic acid is preferably at least one of oxalic acid, malonic acid, and succinic acid.

[0052] In some embodiments, the solvent in step S2 is an alcohol solvent, preferably at least one of ethanol, propanol, and butanol, and more preferably ethanol.

[0053] S3, placing 0.4-2.0 parts of aminosilane coupling agent in 150-400 parts of solvent, adding the hydrotalcite nanosheets prepared in step S2, stirring at 40-70° C. for 2-5 hours, filtering, washing and drying to obtain ammoniated hydrotalcite nanosheets.

[0054] In some embodiments, the aminosilane coupling agent is at least one of KH550, KH602, JH-M902, and KH792.

[0055] In some embodiments, the aminosilane coupling agent is preferably at least one of KH602 and KH792.

[0056] In some embodiments, the solvent in step S3 is an alcohol solvent, preferably at least one of ethanol, propanol, and butanol, and more preferably ethanol.

[0057] S4, place 25-65 parts of ammoniated hydrotalcite nanosheets in 100-400 parts of solvent, add a crosslinker to a concentration of 4-7wt%, stir for 0.5-2h, filter, wash, and dry to obtain modified hydrotalcite nanosheets. The concentration of the crosslinker is the mass concentration of the crosslinker in the ethanol solution. For example, 25 parts of ammoniated hydrotalcite nanosheets are placed in 100 parts of ethanol, and 5 parts of a crosslinker are added, then the concentration of the crosslinker is (5 / 100)*100%= 5wt%. By controlling the concentration of the crosslinker, it is ensured that the crosslinker can be grafted with polyacrylamide to form a three-dimensional network. If the concentration of the crosslinker is too low, the other end of the crosslinker will be capped, and thus it will not be possible to graft with polyacrylamide to form a three-dimensional network.

[0058] In some embodiments, the solvent in step S4 is an alcohol solvent, preferably at least one of ethanol, propanol, and butanol, and more preferably ethanol.

[0059] In some embodiments, the cross-linking agent is glutaraldehyde.

[0060] S5. Weigh 25-70 parts of the modified hydrotalcite nanosheets prepared in step S4, 5-30 parts of cellulose ether, 5-55 parts of organic resin, and 70-260 parts of inorganic filler, and then mix the modified hydrotalcite nanosheets, cellulose ether, organic resin, and inorganic filler to obtain a heavy metal contaminated soil remediation agent.

[0061] In some embodiments, based on weight, the modified hydrotalcite nanosheets are 26-64 parts, the cellulose ether is 9-30 parts, the organic resin is 8-51 parts, and the solid waste filler is 75-250 parts.

[0062] In some embodiments, the mass ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.1-1.0).

[0063] In some embodiments, the mass ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.3-0.8).

[0064] In some embodiments, the cellulose ether is at least one of carboxymethyl cellulose, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose.

[0065] In some embodiments, the cellulose ether is preferably at least one of carboxymethyl cellulose and sodium carboxymethyl cellulose.

[0066] In some embodiments, the organic resin is at least one of epoxy resin, polyacrylamide, and polyvinyl alcohol.

[0067] In some embodiments, the organic resin is preferably polyacrylamide.

[0068] In some embodiments, the inorganic filler is one or more of feldspar waste, red mud, fly ash, and steel slag.

[0069] Example

[0070] The following examples describe the disclosure of the present invention in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present invention will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0071] Example 1

[0072] A heavy metal contaminated soil repair agent comprises the following components: 45 parts of modified hydrotalcite nanosheets, 18 parts of cellulose ether (sodium carboxymethyl cellulose), 24 parts of organic resin (polyacrylamide), 150 parts of inorganic filler (60 parts of fly ash (average particle size 45 microns) and 90 parts of steel slag (average particle size 200 microns)).

[0073] Wherein, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is: 45:24=1:0.53.

[0074] The raw materials of the modified hydrotalcite nanosheets are: 36 parts of hydrotalcite (silicate calcium aluminum hydrotalcite), 48 parts of organic acid (oxalic acid), 0.8 parts of aminosilane coupling agent (KH602), and 12 parts of crosslinking agent (glutaraldehyde, the concentration of the crosslinking agent in the ethanol solution is 6%).

[0075] A method for preparing a heavy metal contaminated soil remediation agent comprises the following steps:

[0076] S1, dispersing 36 parts of silicate calcium aluminum hydrotalcite in 200 parts of ethanol to obtain a hydrotalcite suspension;

[0077] S2, diluting 48 parts of oxalic acid in 50 parts of ethanol to obtain an oxalic acid solution, and then adding the oxalic acid solution dropwise to the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 5 hours, and the hydrotalcite nanosheets are obtained by filtering, washing and drying;

[0078] S3, placing 0.8 parts of aminosilane coupling agent KH602 in 200 parts of ethanol, and then adding the hydrotalcite nanosheets prepared in step S2, stirring at 60° C. for 4 hours, filtering, washing, and drying to obtain ammoniated hydrotalcite nanosheets;

[0079] S4. Weigh 45 parts of the ammoniated hydrotalcite nanosheets prepared in step S3 and place them in 200 parts of ethanol, add 12 parts of glutaraldehyde to make the concentration of the crosslinking agent 6 wt %, stir for 1 hour, filter, wash and dry to obtain modified hydrotalcite nanosheets.

[0080] S5. Weigh 45 parts of the modified hydrotalcite nanosheets prepared in step S4, 18 parts of sodium carboxymethyl cellulose, 24 parts of polyacrylamide, 60 parts of fly ash (average particle size 45 μm), and 90 parts of steel slag (average particle size 200 μm), and then mix the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0081] Example 2

[0082] A heavy metal contaminated soil repair agent comprises the following components: 26 parts of modified hydrotalcite nanosheets, 9 parts of cellulose ether (carboxymethyl cellulose), 8.5 parts of organic resin (polyacrylamide), 75 parts of inorganic filler (30 parts of fly ash (average particle size 60 microns) and 45 parts of steel slag (average particle size 250 microns)).

[0083] Wherein, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is 26:8.5=1:0.33.

[0084] The raw materials of the modified hydrotalcite nanosheets are: 20 parts of hydrotalcite (silicate calcium aluminum hydrotalcite), 26 parts of organic acid (malonic acid), 0.4 parts of aminosilane coupling agent (KH602), and 7.5 parts of cross-linking agent (glutaraldehyde, the concentration of the cross-linking agent in the ethanol solution is 5%).

[0085] A method for preparing a heavy metal contaminated soil remediation agent comprises the following steps:

[0086] S1, dispersing 20 parts of silicate calcium aluminum hydrotalcite in 120 parts of ethanol to obtain a hydrotalcite suspension;

[0087] S2, diluting 26 parts of malonic acid in 30 parts of ethanol to obtain a malonic acid solution, and then adding the malonic acid solution drop by drop into the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 4 hours, and the hydrotalcite nanosheets are obtained by filtering, washing and drying;

[0088] S3, placing 0.4 parts of aminosilane coupling agent KH602 in 120 parts of ethanol, and then adding the hydrotalcite nanosheets prepared in step S2, stirring at 70° C. for 3 hours, filtering, washing, and drying to obtain ammoniated hydrotalcite nanosheets;

[0089] S4, weighing 25 parts of the ammoniated hydrotalcite nanosheets prepared in step S3, placing them in 150 parts of ethanol, adding 7.5 parts of glutaraldehyde to make the concentration of the crosslinking agent 5wt%, stirring for 2h, filtering, washing and drying to obtain modified hydrotalcite nanosheets.

[0090] S5. Weigh 26 parts of the modified hydrotalcite nanosheets prepared in step S4, 9 parts of carboxymethyl cellulose, 8.5 parts of polyacrylamide, 30 parts of fly ash (average particle size 60 microns), and 45 parts of steel slag (average particle size 250 microns), and then mix the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0091] Example 3

[0092] A heavy metal contaminated soil repair agent comprises the following components: 64 parts of modified hydrotalcite nanosheets, 30 parts of cellulose ether (sodium carboxymethyl cellulose), 51 parts of organic resin (polyacrylamide), 250 parts of inorganic filler (100 parts of fly ash (average particle size 40 microns) and 150 parts of steel slag (average particle size 180 microns)).

[0093] Wherein, the weight ratio of the modified hydrotalcite nanosheets to the organic resin is 64:51=1:0.80.

[0094] The raw materials of the modified hydrotalcite nanosheets are: 60 parts of hydrotalcite (silicate calcium aluminum hydrotalcite), 80 parts of organic acid (oxalic acid), 1.8 parts of aminosilane coupling agent (KH792), and 21 parts of cross-linking agent (glutaraldehyde, the concentration of the cross-linking agent in the ethanol solution is 7%).

[0095] A method for preparing a heavy metal contaminated soil remediation agent comprises the following steps:

[0096] S1, dispersing 60 parts of silicate calcium aluminum hydrotalcite in 300 parts of ethanol to obtain a hydrotalcite suspension;

[0097] S2, diluting 80 parts of oxalic acid in 80 parts of ethanol to obtain an oxalic acid solution, and then adding the oxalic acid solution dropwise to the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 6 hours, and the hydrotalcite nanosheets are obtained by filtering, washing, and drying;

[0098] S3, placing 1.8 parts of aminosilane coupling agent KH792 in 400 parts of ethanol, and then adding the hydrotalcite nanosheets prepared in step S2, stirring at 40° C. for 5 hours, filtering, washing, and drying to obtain ammoniated hydrotalcite nanosheets;

[0099] S4, weighing 60 parts of the aminated hydrotalcite nanosheets prepared in step S3 and placing them in 300 parts of ethanol, adding 21 parts of glutaraldehyde to make the concentration of the crosslinking agent 7wt%, stirring for 0.7h, filtering, washing and drying to obtain modified hydrotalcite nanosheets.

[0100] S5. Weigh 64 parts of the modified hydrotalcite nanosheets prepared in step S4, 30 parts of sodium carboxymethyl cellulose, 51 parts of polyacrylamide, 100 parts of fly ash (average particle size 40 microns), and 150 parts of steel slag (average particle size 180 microns), and then mix the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0101] Example 4

[0102] The preparation methods of Example 4 and Example 1 are basically the same, the main difference being that in step S2, adipic acid is used instead of oxalic acid, that is, step S2 is: S2, 48 parts of adipic acid are diluted in 50 parts of ethanol to obtain an adipic acid solution, and then the adipic acid solution is added dropwise to the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 5 hours, and the hydrotalcite nanosheets are obtained by filtering, washing, and drying.

[0103] Example 5

[0104] The preparation methods of Example 5 and Example 1 are basically the same, the main difference being that in step S3, the aminosilane coupling agent is replaced by KH550 instead of KH602, that is, step S3 is: S3, 0.8 parts of aminosilane coupling agent KH550 is placed in 200 parts of ethanol, and then the hydrotalcite nanosheets prepared in step S2 are added, stirred at 60°C for 4h, filtered, washed, and dried to obtain ammoniated hydrotalcite nanosheets.

[0105] Example 6

[0106] The preparation methods of Example 6 and Example 1 are basically the same, the main difference is that the modified hydrotalcite nanosheets and organic resin polyacrylamide added in step S5 are different in the proportions, specifically 58 parts of modified hydrotalcite nanosheets and 11 parts of organic resin polyacrylamide, and the weight ratio of modified hydrotalcite nanosheets to organic resin is 58:11=1:0.19.

[0107] Example 7

[0108] The preparation methods of Example 7 and Example 1 are basically the same, the main difference is that the modified hydrotalcite nanosheets and organic resin polyacrylamide added in step S5 are different in the proportions, specifically 36 parts of modified hydrotalcite nanosheets and 33 parts of organic resin polyacrylamide, and the weight ratio of modified hydrotalcite nanosheets to organic resin is 36:33=1:0.92.

[0109] Example 8

[0110] The preparation methods of Example 8 and Example 1 are basically the same, the main difference being that in S4, the concentration of the crosslinking agent is 3wt%. Specifically, 45 parts of the ammoniated hydrotalcite nanosheets prepared in step S3 are weighed and placed in 200 parts of ethanol, 6 parts of glutaraldehyde are added to make the concentration of the crosslinking agent 3wt%, stirred for 1 hour, filtered, washed, and dried to obtain modified hydrotalcite nanosheets.

[0111] Comparative Example 1

[0112] The preparation methods of Comparative Example 1 and Example 1 are basically the same, the main difference being that in step S2, acetic acid is used instead of oxalic acid, that is, step S2 is: S2, 48 parts of acetic acid are diluted in 50 parts of ethanol to obtain an acetic acid solution, and then the acetic acid solution is added dropwise to the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 5 hours, and the hydrotalcite nanosheets are obtained by filtering, washing, and drying.

[0113] Comparative Example 2

[0114] The preparation methods of Comparative Example 2 and Example 1 are basically the same, the main difference being that in the process of preparing the modified hydrotalcite nanosheets, the modified hydrotalcite nanosheets are first modified with a silane coupling agent and then intercalated with oxalic acid, that is, the specific steps of preparing the modified hydrotalcite nanosheets are:

[0115] S1. Place 0.8 parts of aminosilane coupling agent KH602 in 200 parts of ethanol, add 36 parts of silicate calcium aluminum hydrotalcite, disperse evenly, stir at 60°C for 4 hours, filter, wash and dry to obtain ammoniated hydrotalcite nanosheets;

[0116] S2, dispersing the ammoniated hydrotalcite nanosheets prepared in step S1 in 200 parts of ethanol to obtain a hydrotalcite suspension;

[0117] S3. Dilute 48 parts of oxalic acid in 50 parts of ethanol to obtain an oxalic acid solution, then add the oxalic acid solution drop by drop into the hydrotalcite suspension under stirring. After the addition is completed, continue stirring for 5 hours, filter, wash and dry to obtain acidified hydrotalcite nanosheets.

[0118] S4. Weigh 45 parts of the acidified hydrotalcite nanosheets prepared in step S3 and place them in 200 parts of ethanol, add 12 parts of glutaraldehyde to make the concentration of the crosslinking agent 6 wt %, stir for 1 hour, filter, wash and dry to obtain modified hydrotalcite nanosheets.

[0119] Comparative Example 3

[0120] The preparation methods of Comparative Example 3 and Example 1 are basically the same, the main difference being that no cross-linking agent glutaraldehyde is added during the preparation of the modified hydrotalcite nanosheets. The specific steps are:

[0121] A method for preparing a heavy metal contaminated soil remediation agent comprises the following steps:

[0122] S1, dispersing 36 parts of hydrotalcite in 200 parts of ethanol to obtain a hydrotalcite suspension;

[0123] S2, diluting 48 parts of oxalic acid in 50 parts of ethanol to obtain an oxalic acid solution, and then adding the oxalic acid solution dropwise to the hydrotalcite suspension under stirring. After the addition is completed, stirring is continued for 5 hours, and the hydrotalcite nanosheets are obtained by filtering, washing and drying;

[0124] S3, placing 0.8 parts of aminosilane coupling agent (KH602) in 200 parts of ethanol, and then adding the hydrotalcite nanosheets prepared in step S2, stirring at 60° C. for 4 hours, filtering, washing, and drying to obtain ammoniated hydrotalcite nanosheets;

[0125] S4. Weigh 45 parts of the ammoniated hydrotalcite nanosheets prepared in step S3, 18 parts of sodium carboxymethyl cellulose, 24 parts of polyacrylamide, 60 parts of fly ash (average particle size 45 μm), and 90 parts of steel slag (average particle size 200 μm), and then mix the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0126] Comparative Example 4

[0127] The preparation methods of Comparative Example 4 and Example 1 are basically the same, the main difference is that 18 parts of cellulose ether (sodium carboxymethyl cellulose) are not added in step S5, and the amount of organic resin (polyacrylamide) is increased by 18 parts. That is, step 5 is: S5, weigh 45 parts of modified hydrotalcite nanosheets prepared in step S4, 42 parts of polyacrylamide, 60 parts of fly ash (average particle size 45 microns), and 90 parts of steel slag (average particle size 200 microns), and then mix the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0128] Comparative Example 5

[0129] The preparation methods of Comparative Example 5 and Example 1 are basically the same, the main difference is that 24 parts of organic resin (polyacrylamide) are not added in step S5, and the amount of cellulose ether (sodium carboxymethyl cellulose) is increased by 24 parts. That is, step 5 is: S5, weighing 45 parts of modified hydrotalcite nanosheets prepared in step S4, 42 parts of sodium carboxymethyl cellulose, 60 parts of fly ash (average particle size 45 microns), and 90 parts of steel slag (average particle size 200 microns), and then mixing the components evenly to obtain a heavy metal contaminated soil remediation agent.

[0130] Experimental Examples

[0131] Take the air-dried heavy metal ion Cu 2+ 、Zn 2+ , Pb 2+To 150 g of contaminated soil sample, 4% of the weight of the soil was added with the stabilizing agent prepared in Examples 1-8 and Comparative Examples 1-5, and the mixture was evenly mixed. Water was then added to make the soil moisture content 18%. After sufficient stirring, a cylindrical specimen of Φ150 mm × H150 mm was prepared. The specimen was demoulded, and the unconfined compressive strength (bearing capacity) and the concentration of heavy metal ions in the soil were tested after curing for 7 days.

[0132] The unconfined compressive strength is tested in accordance with T0805-1994 "Test method for unconfined compressive strength of materials stabilized with inorganic binders".

[0133] Heavy metal content detection: The soil after curing is crushed and toxic leaching (heavy metal leaching test) is carried out according to HJ T299-2007 "Toxicity leaching method of solid waste leaching - sulfuric acid and nitric acid method".

[0134] Table 1: Soil carrying capacity and heavy metal content

[0135]

[0136] From the data detected in Examples 1 to 3, it can be seen that the heavy metal contaminated soil remediation agent prepared in Examples 1 to 3 can well enhance the bearing capacity of the soil and reduce the heavy metal Cu in the soil. 2+ 、Zn 2+ and Pb 2+ The content.

[0137] Compared with Example 1, Example 4 has a significant decrease in bearing capacity and a decrease in the fixation effect of heavy metal ions. This may be because adipic acid is used instead of oxalic acid in Example 4, and the carbon chain in the structure is relatively long, which weakens the hydrophilicity of the carboxyl end of the modified hydrotalcite nanosheets, affects the degree of water film destruction on the surface of soil particles, and the soil particles have poor cohesion and insufficient bearing capacity. At the same time, replacing oxalic acid with adipic acid may reduce the introduced carboxyl content, thereby weakening the fixation effect on heavy metal ions in the soil.

[0138] In Comparative Example 1, the carrying capacity and heavy metal ion fixation ability further decreased. The possible reason may be that acetic acid was used instead of oxalic acid. Acetic acid has only one carboxyl group and can only be used to intercalate hydrotalcite layers. It does not have additional carboxyl groups to adsorb on soil particles, cooperate with the hydrophobic end to destroy the water film on the surface of soil particles, and cannot fix the heavy metal ions in the soil.

[0139] In Example 5, the bearing capacity and heavy metal ion fixation capacity are not much different from those in Example 1. This may be due to the short chain length of the coupling agent KH550 and the slightly weaker hydrophobicity, which has a slight impact on the three-dimensional network construction, but the overall impact is not significant. The heavy metal contaminated soil remediation agent prepared in Example 5 can still well enhance the bearing capacity of the soil and reduce the heavy metal Cu in the soil. 2+、Zn 2+ and Pb 2+ The content.

[0140] In Example 6, the bearing capacity decreased, which may be due to the excessive amount of modified hydrotalcite nanosheets and the insufficient amount of polyacrylamide, which failed to achieve grafting balance, incomplete construction of the organic-inorganic three-dimensional skeleton, and the lack of water absorption and bonding effects of polyacrylamide, so the mechanical properties of the soil decreased.

[0141] In Example 7, the bearing capacity decreased, and the metal ion content in the soil increased after treatment. This may be due to the fact that there are too few modified hydrotalcite nanosheets, the overall degree of damage to the water film on the surface of the soil particles is insufficient, the cohesion of the soil particles is reduced, and the organic-inorganic three-dimensional skeleton formed in the soil is relatively loose, so the mechanical properties of the soil are reduced. In addition, too few modified hydrotalcite nanosheets reduce the chelation effect of metal ions in the soil, which increases the metal ion content in the soil after treatment.

[0142] In Example 8, the load-bearing capacity decreased, which may be due to the glutaraldehyde concentration of 3 wt %. The low glutaraldehyde concentration will cause the other end of part of the glutaraldehyde to be blocked, thus affecting the construction of the three-dimensional network between the polyacrylamide and the polyacrylic acid amide.

[0143] In Comparative Example 2, the fixation effect of heavy metal ions is significantly reduced. This may be because in the process of preparing the modified hydrotalcite nanosheets, the silane coupling agent is first used for amination modification, and then the oxalic acid is intercalated. After the silane coupling agent is grafted on the surface, the intercalation of oxalic acid is affected, resulting in a significant decrease in the intercalation degree. The fixation effect on heavy metal ions in the soil is significantly lower than that of the heavy metal contaminated soil remediation agent prepared in the example.

[0144] In Comparative Example 3, the bearing capacity is significantly reduced. This may be because the hydrotalcite nanosheets are not modified with glutaraldehyde. On the one hand, it is not conducive to increasing the length of the grafted fatty chain segment on the surface of the hydrotalcite, and is not conducive to increasing the hydrophobicity of the other end, that is, it is not conducive to improving the aggregation force between soil particles. On the other hand, it is unable to cooperate with polyacrylamide to construct an organic-inorganic three-dimensional skeleton structure. Therefore, compared with Example 1, the bearing capacity of the soil is significantly reduced.

[0145] Sodium carboxymethyl cellulose can cooperate with organic resins to make the soil intertwined to form a complex network, fix the soil particles inside, and absorb excess water, thereby adjusting the internal structure of the soil; it can also chelate heavy metal ions in the soil, thereby effectively fixing the heavy metal ions and achieving the effect of soil stabilization and solidification.

[0146] In Comparative Example 4, only polyacrylamide was used without sodium carboxymethyl cellulose, and the fixation effect on heavy metal ions became poor.

[0147] In comparative example 5, the bearing capacity is seriously reduced, which may be due to the fact that in the technical solution of the present application, polyacrylamide acts as a crosslinking agent with glutaraldehyde, and the aldehyde group at one end thereof reacts with the primary amine on the hydrotalcite modified by the silane coupling agent, and is grafted to the surface of the modified hydrotalcite nanosheet. In the process of adding the soil stabilization agent to the soil for treatment, in the process of stabilizing the contaminated soil, the aldehyde group on the surface of the modified hydrotalcite nanosheet reacts with the primary amine on the polyacrylamide, and directly constructs an interpenetrating organic-inorganic three-dimensional skeleton structure in the system, thereby improving the overall strength of the system. Polyacrylamide has a large molecular weight, a high viscosity coefficient, excellent water absorption capacity and chemical activity, and can be adsorbed on the surface of soil particles to increase the cohesion between soil particles, thereby regulating the soil hydraulic properties and improving the structural stability of the soil. When only sodium carboxymethyl cellulose is used in comparative example 5, without polyacrylamide, it cannot react with the modified hydrotalcite nanosheet, and cannot participate in the construction of the organic-inorganic skeleton to provide strength, and the bearing capacity of the soil is significantly reduced.

[0148] Therefore, the present invention uses a soil stabilization agent obtained by compounding modified hydrotalcite nanosheets, cellulose ether, organic resin and solid waste filler to improve the soil carrying capacity and the pollutant complexation and sealing effect, thereby achieving the purpose of reasonable, efficient and low-carbon contaminated soil remediation and resource utilization.

[0149] By adding modified hydrotalcite nanosheets, on the one hand, the modified hydrotalcite nanosheets have "amphiphilic" properties, that is, the hydrotalcite nanosheets containing a large number of carboxyl groups and water-absorbing functions at one end can destroy the water film originally formed on the surface of soil particles, reduce the repulsion between soil particles, increase the adhesion and agglomeration between soil particles, make soil particles adsorb each other, improve the curing effect, and the alkyl long chain grafted at the other end forms a hydrophobic film on the surface of soil particles to prevent water intrusion and effectively avoid water penetration, thereby improving the stability and durability of the soil barrier layer. On the other hand, the aldehyde group at the end of the long chain can react with the amino group on polyacrylamide in the system, expand and extend the cross-linked network of polyacrylamide, and construct an interpenetrating organic-inorganic three-dimensional skeleton structure. Thirdly, the carboxyl groups grafted on the hydrotalcite can also complex with metal cations in the soil, further playing a role in fixing metal pollutants.

[0150] By adding cellulose ether, it can absorb water and generate viscosity, which is beneficial to improving the interfacial bonding strength. The carboxyl-containing cellulose ether complexes the heavy metal ions in the system. The cellulose ether molecular chains and the organic-inorganic three-dimensional skeleton formed by modified hydrotalcite nanosheets and organic resins are intertwined and entangled, which can effectively trap heavy metal ions in the skeleton structure and solidify and seal the pollutants.

[0151] By adding inorganic fillers, on the one hand, the generated gel product is interspersed in the pores of the contaminated soil, making the soil structure more compact and improving the soil strength to facilitate the functional application of the site; on the other hand, in response to the call for low-carbon development, inorganic fillers are used as solid waste fillers to transform large amounts of solid waste into resources and realize solid waste disposal.

[0152] By controlling the weight ratio of modified hydrotalcite nanosheets and organic resin, the modified hydrotalcite nanosheets and organic resin construct a robust organic-inorganic three-dimensional skeleton structure, thereby improving the mechanical properties of the soil.

[0153] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A heavy metal contaminated soil remediation agent, characterized in that: By weight, it comprises 25-70 parts of modified hydrotalcite nanosheets, 5-30 parts of cellulose ether, 5-55 parts of organic resin, and 70-260 parts of inorganic filler; The organic resin is polyacrylamide; The raw materials for preparing the modified hydrotalcite nanosheets include hydrotalcite, organic acid, aminosilane coupling agent and cross-linking agent; The organic acid is at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and terephthalic acid; The cross-linking agent is glutaraldehyde; The preparation method of modified hydrotalcite nanosheets is as follows: S1, dispersing the hydrotalcite in a solvent to obtain a hydrotalcite suspension; S2, diluting an organic acid in a solvent to obtain an organic acid solution, adding the organic acid solution to the hydrotalcite suspension, stirring, filtering, washing, and drying to obtain hydrotalcite nanosheets; S3, placing an aminosilane coupling agent in a solvent, and then adding hydrotalcite nanosheets, filtering, washing, and drying after the reaction to obtain ammoniated hydrotalcite nanosheets; S4, dispersing the aminated hydrotalcite nanosheets in a solvent, adding a cross-linking agent, stirring, filtering, washing, and drying to obtain modified hydrotalcite nanosheets.

2. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The weight ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.1-1.0).

3. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The weight ratio of the modified hydrotalcite nanosheets to the organic resin is 1:(0.3-0.8).

4. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The cellulose ether is at least one of sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; The inorganic filler is at least one of feldspar waste, red mud, fly ash and steel slag.

5. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The cellulose ether is sodium carboxymethyl cellulose.

6. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The raw materials for preparing the modified hydrotalcite nanosheets include, by weight, 20-60 parts of hydrotalcite, 20-80 parts of organic acid, and 0.4-2.0 parts of aminosilane coupling agent.

7. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The hydrotalcite is at least one of silicate-type calcium aluminum hydrotalcite, silicate-type magnesium aluminum hydrotalcite, carbonate-type calcium aluminum hydrotalcite, and carbonate-type magnesium aluminum hydrotalcite; The aminosilane coupling agent is at least one of KH550, KH602, JH-M902 and KH792.

8. The heavy metal contaminated soil remediation agent according to claim 1, characterized in that: The organic acid is at least one of oxalic acid, malonic acid and succinic acid; the aminosilane coupling agent is at least one of KH602 and KH792.

9. A method for preparing a heavy metal contaminated soil remediation agent according to any one of claims 1 to 8, characterized in that: The steps include: S1, dispersing the hydrotalcite in a solvent to obtain a hydrotalcite suspension; S2, diluting an organic acid in a solvent to obtain an organic acid solution, adding the organic acid solution to the hydrotalcite suspension, stirring, filtering, washing, and drying to obtain hydrotalcite nanosheets; S3, placing an aminosilane coupling agent in a solvent, and then adding hydrotalcite nanosheets, filtering, washing, and drying after the reaction to obtain ammoniated hydrotalcite nanosheets; S4, dispersing the aminated hydrotalcite nanosheets in a solvent, adding a cross-linking agent, stirring, filtering, washing, and drying to obtain modified hydrotalcite nanosheets; S5, weighing the modified hydrotalcite nanosheets, cellulose ether, organic resin, and inorganic filler, and then uniformly mixing the modified hydrotalcite nanosheets, cellulose ether, organic resin, and inorganic filler to obtain a heavy metal contaminated soil remediation agent; In step S4, the concentration of the cross-linking agent is 4-7 wt %.

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