CN112893437A

CN112893437A - Soil remediation method

Info

Publication number: CN112893437A
Application number: CN202110054782.7A
Authority: CN
Inventors: 侯德义; 王刘炜
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2021-01-15
Filing date: 2021-01-15
Publication date: 2021-06-04

Abstract

The invention provides a soil remediation method, which comprises the following steps: adding high-water-absorption metal binding powder into soil to be repaired polluted by one or more heavy metals, wherein the high-water-absorption metal binding powder can bind heavy metal ions from the soil and has water absorption and expansibility capable of absorbing deionized water more than one hundred times of the weight of the high-water-absorption metal binding powder, and the addition amount of the high-water-absorption polymer is 4-6% of the mass of the soil to be repaired; and adding water into the soil to be repaired into which the high-water-absorptivity metal bonding powder is added.

Description

Soil remediation method

Technical Field

The invention relates to the technical field of environmental remediation, in particular to a soil remediation method.

Background

Heavy metal pollution of soil poses serious threats to ecological environment, food safety and human health. Soil heavy metal pollution often presents compound characteristics, and the compound pollution of heavy metals such as manganese, zinc, arsenic, lead, cadmium, mercury and the like is caused by multi-source superposition of natural background, industrial emission, agricultural activity and traffic emission, and the pollution characteristics of concentrated connection and complex cause appear, so that the ecological environment of the area is seriously threatened. Aiming at the multi-metal composite polluted soil, a scientific prevention and treatment method strategy needs to be researched urgently, so that the cooperative risk impedance of various pollutants is realized.

Stabilization is the most common remediation method for soil pollution remediation. By adding stabilizing agents into the polluted soil, the geochemical state of the heavy metal can be converted from a more active water-soluble exchange state, a carbonate binding state and the like to an inert state such as a residue state with low migration risk and the like. However, it is worth noting that the current stabilization repair method is usually directed to the short-term repair effect, but neglects the long-term influence of repair. Because the contaminants are not actually separated from the soil, once environmental conditions change (e.g., soil cracks to produce microcracks), heavy metals tend to migrate across the medium, creating potential environmental risks to surface and groundwater. It has been shown that the natural rainfall process is the leading cause of failure of stabilization. In the rainfall process of the nature, soil microcracks are generated, soil aggregates are unstable, and a potential path is provided for the migration of heavy metal pollutants in soil.

Therefore, how to prevent the generation of soil microcracks and ensure the long-term effect of stabilization repair is a technical problem to be solved urgently.

Disclosure of Invention

Therefore, a need exists for a soil remediation method that can prevent the occurrence of soil microcracks and achieve long-term stabilization of heavy metals in contaminated soil.

In one aspect of the invention, a soil remediation method is provided, comprising the steps of:

adding high-water-absorptivity metal binding powder into soil to be repaired polluted by one or more heavy metals, wherein the high-water-absorptivity metal binding powder can irreversibly bind heavy metal ions from the soil and has water absorptivity and expansibility capable of absorbing deionized water more than hundred times of the weight of the high-water-absorptivity metal binding powder, and the addition amount of the high-water-absorptivity polymer is 4-6% of the mass of the soil to be repaired; and

and adding water into the soil to be repaired into which the high-water-absorptivity metal bonding powder is added.

In one embodiment, the high water absorption metal bonding powder comprises a high water absorption polymer which is a cross-linked network structure and contains-OH and-NH₂、-N⁺、-C＝O、-COO^-One or more groups of (a).

In one embodiment, the polymer is selected from one or more of polyacrylamide, alginic acid, sodium alginate, polyacrylic acid, and polyethylene glycol.

In one embodiment, the polymer is polyacrylamide, or the polymer is polyacrylamide and alginic acid.

In one embodiment, the super absorbent metal bonded powder further comprises a soil passivator selected from one or more of a silicate soil passivator, a lime soil passivator, a charcoal soil passivator, and a natural mineral soil passivator.

In one embodiment, the weight ratio of the superabsorbent polymer to the soil passivating agent is 1: (1-10).

In one embodiment, the super absorbent metal bonding powder is a mixed powder of polyacrylamide, alginic acid and a silicate soil passivator.

In one embodiment, the addition amount of the water is 10-70% of the mass of the soil to be repaired.

In one embodiment, the average particle size of the super absorbent metal bonded powder is not more than 0.15 mm.

In one embodiment, the super absorbent metal bonding powder is capable of bonding Cr, Mn, Ni, Zn, Pb, and Cd.

According to the soil remediation method provided by the invention, the high-water-absorptivity metal binding powder is added into the soil to be remediated, can irreversibly bind heavy metal ions in the soil, and has water absorptivity and expansibility capable of absorbing deionized water with the weight being more than one hundred times of the self weight, and the high-water-absorptivity metal binding powder can rapidly absorb water after encountering water molecules to expand the volume of the water molecules so as to fill up soil microcracks, and can irreversibly bind the heavy metal ions from the soil, so that the soil remediation method can effectively resist the problems of increased migration of heavy metal pollutants and increased pollution risk caused by rainfall and other processes, and realize long-term stable remediation of the heavy metals in the contaminated soil.

Drawings

FIG. 1 is a flow chart of a soil remediation method of the present invention;

FIG. 2 is a schematic diagram illustrating the passivation of heavy metal ions by a soil remediation method according to one embodiment of the present invention;

FIG. 3 is a scanning electron microscope image of the soil after remediation according to example 1 of the present invention;

FIG. 4 is an enlarged view of the scanning electron microscope at circle in FIG. 3;

FIG. 5 is a graph comparing the stabilization rates of each heavy metal in the soil of example 1 of the present invention and each metal in the soil of comparative example 1;

FIG. 6 shows the stabilization rates before and after aging of each heavy metal in soil according to example 2 of the present invention;

FIG. 7 is a graph showing the change in Mn concentration in soil with the number of aging times in example 2 of the present invention;

FIG. 8 is a graph showing the change of Zn concentration in soil according to example 2 of the present invention with the number of aging times;

FIG. 9 is a curve showing the variation of Cd concentration in soil with aging frequency in example 2 of the present invention;

FIG. 10 is a graph showing the change of the concentration of Pd in soil according to example 2 of the present invention with the number of aging times;

FIG. 11 is a photograph showing micro-cracks in soil according to example 2 and comparative example 2 of the present invention;

FIG. 12 is a comparison of total lengths of soil microfractures for example 2 of the present invention and comparative example 2;

FIG. 13 is a comparison of the total number of soil microfractures for example 2 of the present invention and comparative example 2.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Other than as shown in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients, physical and chemical properties, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". For example, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can be suitably varied by those skilled in the art in seeking to obtain the desired properties utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range and any range within that range, for example, 1 to 5 includes 1, 1.1, 1.3, 1.5, 2, 2.75, 3, 3.80, 4, and 5, and the like.

Referring to fig. 1, the present invention provides a soil remediation method, including the following steps:

s10, adding super absorbent metal bonding powder into soil to be repaired polluted by one or more heavy metals, wherein the super absorbent metal bonding powder can bond heavy metal ions from the soil and has water absorption and expansibility capable of absorbing deionized water with the weight being more than one hundred times of the self weight, and the addition amount of the super absorbent polymer is 4-6% of the mass of the soil to be repaired; and

s20, adding water into the soil to be repaired into which the high water absorption metal bonding powder is added.

As used herein, the term "swellability" means that the superabsorbent metal binding powder increases in volume by itself after absorbing water. The expansibility of the invention means that the volume of the high water absorption metal bonding powder is expanded to at least hundreds of times or even thousands of times after absorbing water. More preferably, the superabsorbent metal bonding powder may swell hundreds of times, even thousands of times, in at least 30 seconds.

The high water absorption metal bonding powder also has water retention property, and water is not easy to extrude out of the high water absorption metal bonding powder under external pressure.

As used herein, the term "remediation" refers to a process of reducing, separating, or removing contamination from a contaminated site in order to mitigate or minimize damage to the health or environment of the animal.

The subject of the remediation may be any known "heavy metal" that is typically introduced to the site as a result of mining or another industrial process such as smelting, tanning or paint production. As used herein, the term "heavy metal" refers to a metal element having a high atomic weight, for example, mercury, chromium, cadmium, arsenic, silver, gold, uranium, and lead. Specifically, the heavy metal is a metal having a specific gravity of about 5.0 or more compared with water. As used herein, "heavy metal ion" refers to an elemental heavy metal particle or elemental heavy metal particle system with a net charge. Non-limiting examples of heavy metals include vanadium, cobalt, chromium, iron, arsenic, germanium, molybdenum, gold, antimony, tin, bismuth, zinc, copper, tungsten, rhenium, uranium, selenium, nickel, lead, mercury, cadmium, silver, manganese, palladium, and platinum. The term heavy metal ion encompasses heavy metal ion complexes (complexes).

The superabsorbent metal binding powder of the present invention can have any size suitable for the process and conditions, including but not limited to, macroparticles, microparticles, nanoparticles, or combinations thereof. In a preferred embodiment, the super absorbent metal bonded powder is micro-particles and nano-particles. As used herein, the term "particle" or "microparticle" refers to an entity having a finite mass and internal structure. Generally, a particle is a collection of atoms or molecules in sufficient quantity to allow it to have macroscopic properties such as volume, density, pressure, and temperature. The term "fine particles" as used herein means particles having an average particle diameter of 0.15mm or less but larger than 1 μm. Further preferably, the super absorbent metal bonded powder is a nanoparticle, i.e., a particle having an average diameter of generally from about 1 to 1000 nm. The most obvious advantage that nanostructured materials offer for environmental remediation is that they provide a very high specific surface area. The advantages of using extremely small particles of the superabsorbent metal binding powders in terms of their surface area to volume ratio are considerable, such as more uniform mixing with soil, better water absorption, higher water absorption efficiency, higher reactivity, etc. The size of the super absorbent metal bonding powder can be reduced to be less than 0.15mm, even micron or nanometer by a physical mode of grinding or ball milling.

The soil remediation method provided by the invention can be suitable for in-situ remediation and also can be suitable for ex-situ remediation.

In one embodiment, the soil remediation method of the invention adopts in-situ remediation, i.e., the super absorbent metal binding powder is directly applied to the soil to be remediated. In this embodiment, the method for determining the quality of the soil to be restored may be: determining the soil restoration depth H, calculating the volume V (V-S H) of the soil to be restored according to the restoration area S, and then calculating the volume m (which can be sampled and calculated and is generally 1.3 g/cm) of the soil according to the volume weight m of the dry soil³～1.6g/cm³) And calculating the mass M (M-M V) of the soil to be restored.

In this embodiment, the soil remediation method of the present invention may include adding the super absorbent metal binding powder to the soil to be remediated in any convenient manner. Preferably, the powder is added to a certain depth of the soil. This may be accomplished by any convenient means, such as plowing, by means of a tool or using a slurry of a highly water absorbent metal binding powder applied to the surface of the soil to be remediated and infiltrated to the desired depth of the soil.

In another embodiment, the soil remediation method of the invention adopts ex-situ remediation, namely, the soil to be remediated is dug out of the contaminated site as the soil to be remediated, and then the soil is transferred to a different place for remediation. And adding the high-water-absorptivity metal bonding powder into the soil to be repaired, adding water to reach a proper water content, maintaining the soil on site for 6-8 days, and transferring the soil to a polluted site for landfill.

In some preferred embodiments, the superabsorbent metal binding powder is a superabsorbent polymer having a cross-linked network structure and containing-OH, -NH₂、-N⁺、-C＝O、-COO^-One or more groups of (a). The crosslinked network structure is apt to trap heavy metals and to give the polymer high water absorption, and the larger the pore diameter of the crosslinked network structure is, the higher the water absorption capacity is, but for trapping heavy metals, the larger the pore diameter of the crosslinked network structure is, the less likely it is to be trapped. -OH, -NH₂、-N⁺、-C＝O、-COO^-All have good hydrophilicity and can complex heavy metal ions. -N⁺OH can complex heavy metal anions, -NH₂、-C＝O、-COO^-Heavy metal cations can be complexed.

The polymer comprises at least one repeated molecular structural unit, wherein the molecular structural unit comprises a main chain and at least one side chain, the main chain can be a carbon chain, a carbon-oxygen hetero chain, a carbon ring or a carbon heterocyclic ring, and the side chain contains-OH and-NH₂、-N⁺、-C＝O、-COO^-At least one group of (1).

In some preferred embodiments, the side chain contains at least-OH, -C ═ O, -COO^-A group of (1). The embodiment is particularly suitable for polluted soil compounded by multiple heavy metal cations, such as Cd-Pb, Cd-Zn, Ni-Mn and the like, the traditional restoration method is often influenced by the relationship of cation competitive adsorption, sufficient active sites cannot be provided to realize stabilization, the super absorbent polymer is a cross-linked network structure, heavy metals can be swept into the cross-linked structure by a net catcher through establishing a homogeneous and cross-linked network structure in the soil, the structure contains abundant cross-distributed complexing groups, and sufficient sites are provided to realize complexing and fixing of the heavy metals, as shown in FIG. 2.

In other preferred embodimentsIn which the side chain contains at least-N⁺and-COO^-Two groups. The embodiment mode is particularly suitable for the polluted soil compounded by heavy metal anions and cations, such as Cr-Cd, Cr-Mn, Cr-Zn, Cr-Pb and the like, wherein Cr is an anion. The traditional repairing method only can realize the passivation of anions or cations due to the single electric property, and cannot realize the cooperative passivation of the anions and the cations. In the embodiment, the metal oxide has positive and negative charge groups, and can coordinate to passivate heavy metal cations and anions.

In some particularly preferred embodiments, the polymer is selected from one or more of polyacrylamide, alginic acid, sodium alginate, polyacrylic acid, and polyethylene glycol. The polymers have more proper cross-linked network structures, the pore sizes of the cross-linked network structures in the polymers can meet the requirement of high water absorption for repairing soil microcracks, heavy metals can be captured more effectively, the distribution density of groups capable of being combined with heavy metal ions in the cross-linked network structures is more proper, and more abundant active sites which are beneficial to passivation of the heavy metals can be provided. Therefore, the polymers can better repair the soil polluted by the heavy metals.

In some more preferred embodiments, the polymer is selected from polyacrylamides.

In yet other more preferred embodiments, the polymer is selected from the group consisting of polyacrylamide and alginic acid.

The amount of the super absorbent polymer added can be any value between 4% and 6% of the mass of the soil to be repaired, and can also include, but is not limited to, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, and 5.8%.

In some embodiments, the superabsorbent metal bonding powder may further comprise a soil passivating agent. The soil passivator can be one or more selected from silicate soil passivator, lime soil passivator, charcoal soil passivator and natural mineral soil passivator. The soil passivating agent may include, but is not limited to, cement, clay minerals, phosphorus-based minerals, iron-containing minerals, zero-valent iron, biochar, calcium oxide, calcium hydroxide, magnesium oxide, and combinations thereof.

The weight ratio of the super absorbent polymer to the soil passivating agent may be 1: any ratio between (1-10), for example, but not limited to, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1: 9.

In a preferred embodiment, the super absorbent metal bonding powder is a mixed powder of polyacrylamide, alginic acid and a silicate cement soil passivator.

The purpose of adding water in the step S20 in the soil remediation method is to make the high water absorption metal bonding powder quickly absorb water and swell.

The addition amount of the water can be any value between 10% and 70% of the mass of the soil to be repaired, and can also include, but is not limited to, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60% and 65%, for example.

The following are specific examples. The present invention is intended to be further described in detail to assist those skilled in the art and researchers to further understand the present invention, and the technical conditions and the like do not limit the present invention. Any modification made within the scope of the claims of the present invention is within the scope of the claims of the present invention. The contaminated soil described below was taken from the same contaminated site.

Example 1

Adding polyacrylamide dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite polluted soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Example 2

Uniformly mixing polyacrylamide dry powder (the moisture content is less than 10%) and alginic acid dry powder (the moisture content is less than 10%) for 5min in a mass ratio of 1:1 to obtain a super absorbent polymer, and then adding portland cement (the mass ratio of the super absorbent polymer to the portland cement is 1: 4). Adding the mixture into Mn, Zn, Cd and Pb composite polluted soil according to the adding dose of 5 percent of the soil mass (the system comprises 100g of soil, 20g of portland cement, 2.5g of polyacrylamide and 2.5g of alginic acid), and adding 50 percent of water (based on the soil mass).

Example 3

Adding polyacrylamide dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite polluted soil according to the adding amount of 4% of the soil mass, and adding 10% of water (by the soil mass).

Example 4

Adding polyacrylamide dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite polluted soil according to the adding amount of 10% of the soil mass, and adding 70% of water (by the soil mass).

Example 5

Adding polyacrylamide dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb compound contaminated soil according to the adding amount of 4.5% of the soil mass, and then adding 50% of water (by the soil mass).

Example 6

Adding alginic acid dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Example 7

Adding sodium alginate dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Example 8

Uniformly mixing polyacrylamide dry powder (the water content is less than 10%) and alginic acid dry powder (the water content is less than 10%) according to a mass ratio of 1:1, adding the polyacrylamide dry powder and alginic acid dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to an adding dose of 5% of the soil mass (100g of soil, 2.5g of polyacrylamide and 2.5g of alginic acid), and adding 50% of water (calculated by the soil mass).

Example 9

Adding polyacrylic acid dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Example 10

Adding polyethylene glycol dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Comparative example 1

Adding the traditional repairing material iron oxide (main component: alpha-FeOOH) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding dosage of 5% of the soil mass, and adding 30% of water (by the soil mass).

Comparative example 2

Adding the Portland cement into Mn, Zn, Cd and Pb composite contaminated soil according to the adding dose of 5% of the soil mass, and adding 50% of water (by the soil mass).

Comparative example 3

Adding starch-based hydrogel dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite contaminated soil according to the adding amount of 5% of the soil mass, and adding 30% of water (by the soil mass).

Comparative example 4

Adding polyacrylamide dry powder (the water content is less than 10%) into Cr, Mn, Ni, Zn and Pb composite polluted soil according to the adding amount of 3% of the soil mass, and adding 30% of water (by the soil mass).

The process parameter lists of examples 1 to 10 and comparative examples 1 to 4 are shown in table 1 below, each soil was placed in a culture dish having a diameter of 10cm and cultured under the same culture conditions (natural environment), and the total crack length reduction rate and the total crack number reduction rate in the micro crack repairing effect were referred to in comparative example 2.

TABLE 1

Each of the soils of examples 1 to 10 and comparative examples 1 to 4 was subjected to dry-wet cycle aging treatment. The aging treatment is specifically operated as follows: adding water into the soil, standing for 24h, and then drying at 40 ℃ to obtain a dry-wet cycle, wherein the dry-wet cycle is performed for 10 times.

Taking the soil samples subjected to the dry-wet cycle aging treatment, taking the soils of examples 1-10 and comparative examples 1-4 as experimental samples and the original soil as a control sample, carrying out TCLP leaching on the soil samples by using an acetic acid buffer solution, measuring the concentration of heavy metals in the leachate by using ICP-MS, and calculating the heavy metal stabilization rate (the concentration of the heavy metals in the leachate of the experimental sample/the concentration of the heavy metals in the leachate of the control sample), wherein the results are shown in Table 2:

TABLE 2

The soil of example 1, example 2, comparative example 1 and comparative example 2 was selected below for further study comparison.

The appearance of the soil is observed through a scanning electron microscope image, and the scanning electron microscope image of the soil in the example 1 is shown in fig. 3, so that the soil presents smooth characteristics in the micron size, and the smooth part with stripes can be observed in a concealed manner, which indicates that the filled soil micro cracks exist in the smooth part. The appearance of the circle in fig. 3 is enlarged, and as shown in fig. 4, the appearance structure shows a flocculent and swollen characteristic.

FIG. 5 is a graph comparing the stabilization rates of each heavy metal in the soil of example 1 and that of the soil of comparative example 1, and it can be seen that the stabilization rates of Cr, Mn, Ni, Zn, and Pb in the soil of example 1 are increased by 1.47, 2.75, 0.59, 0.51, and 5.02 times, respectively, compared with the stabilization rates of the corresponding heavy metals in the soil of comparative example 1.

In example 2, the stabilizing rates of Zn, Cd and Pb before and after soil aging can reach more than 90%, as shown in FIG. 6.

Example 2 the curves of the concentration of Mn, Zn, Cd, Pb in soil as a function of the number of aging times are shown in fig. 7 to 10, in which the dotted lines are the concentrations of the respective heavy metals in the leachate of the original soil. As can be seen from the figure, the soil of example 2 has very good anti-aging effect and influence on the migration of heavy metals, and the stabilization rate of the heavy metals in the aging process can be kept stable.

The soils of example 2 and comparative example 2 were cultured in culture dishes having a diameter of 10cm under the same conditions, respectively, and the repairing effects thereof were observed and studied.

As shown in fig. 11, the soil of comparative example 2 showed micro-fissures during the culture, while the heavy gold soil of example 2 showed almost no micro-fissures. The total length of soil cracks and the number of cracks were observed and measured, and the crack generation rate (the number of cracks divided by the area of the culture dish) was calculated, and as shown in fig. 12 and 13, the total length of cracks was reduced by 93% and the total number of cracks was reduced by 82% in the soil of example 2, compared with the soil of comparative example 2, indicating that the soil remediation method of example 2 is very effective in the remediation of soil micro cracks.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A soil remediation method, comprising the steps of:

2. The soil remediation method of claim 1, wherein the superabsorbent metal binding powder comprises a superabsorbent polymer having a cross-linked network structure and containing-OH, -NH₂、-N⁺、-C＝O、-COO^-One or more groups of (a).

3. The soil remediation method of claim 2 wherein the polymer is selected from one or more of polyacrylamide, alginic acid, sodium alginate, polyacrylic acid and polyethylene glycol.

4. The soil remediation method of claim 3 wherein said polymer is polyacrylamide, or alternatively wherein said polymer is polyacrylamide and alginic acid.

5. The soil remediation method of claim 2, wherein the super absorbent metal-binding powder further comprises a soil-passivating agent selected from one or more of a silicate-based soil-passivating agent, a lime-based soil-passivating agent, a charcoal-based soil-passivating agent, and a natural mineral-based soil-passivating agent.

6. The soil remediation method of claim 5, wherein the weight ratio of superabsorbent polymer to soil passivating agent is from 1: (1-10).

7. The soil remediation method of claim 5, wherein the super absorbent metal binding powder is a mixed powder of polyacrylamide, alginic acid, and a silicate-based soil passivator.

8. The soil remediation method of any one of claims 1 to 7 wherein the water is added in an amount of from 10% to 70% by mass of the soil to be remediated.

9. The soil remediation method of any one of claims 1 to 7, wherein the superabsorbent metal binding powder has an average particle size of 0.15mm or less.

10. The soil remediation method of any one of claims 1 to 7, wherein the super absorbent metal binding powder is capable of binding Cr, Mn, Ni, Zn, Pb, and Cd.