Composite gel material as well as preparation method and application thereof

Abstract

The invention discloses a composite gel material as well as a preparation method and application thereof, and relates to the technical field of gel materials. The composite gel material is prepared from the following raw materials: chitosan, modified iron oxide hydroxide and a cross-linking agent, the modified iron oxide hydroxide is aluminum ion doped iron oxide hydroxide. The composite gel material provided by the invention can be used as a soil remediation material, can be used for remediation of heavy metal contaminated soil, can effectively adsorb heavy metal ions, promote oxidation of arsenic and enhance the treatment effect of arsenic, has a good fixing effect on heavy metals, is beneficial to preventing migration and pollution of the heavy metals, and has a good application prospect. Meanwhile, the water-retaining property and the fertilizer-retaining property of the soil are remarkably improved, the problem that an existing soil remediation material cannot meet soil remediation and soil nutrition protection at the same time is solved, and the soil remediation material is an effective measure for pollution treatment and heavy metal remediation of the soil.

Description

Technical Field

[0001] The present invention relates to the technical field of gel materials, and particularly relates to a composite gel material, a preparation method thereof, and an application thereof. Background Art

[0002] The pollution of heavy metals in soil is a long-term and complex problem, and multiple factors such as remediation efficiency, soil health, and the sustainability of agricultural production need to be considered during the remediation process. Traditional soil remediation methods (such as chemical precipitation method, elution method, etc.) may lead to the loss of beneficial nutrients in the soil, affect the soil fertility and structural stability, and cannot achieve the dual goals of heavy metal pollution remediation and soil nutrient protection. For example, a large amount of water or chemical reagents are required in some conventional remediation processes, which cause the elution and loss of nutrients (such as nitrogen, phosphorus, potassium, etc.) in the soil, thereby affecting the growth of crops and the sustainability of the soil.

[0003] The prior art discloses a carbon-bacteria coupled heavy metal soil remediation material, which uses goethite-modified biochar and Burkholderia as the main functional components. Although the obtained material can be used for the removal of heavy metal cations, due to the large amount of negative charges on the surface of the organic material, the removal effect on heavy metal anions is very small. And existing iron-based materials (such as iron ore powder, iron oxide, etc.) have unstable effects when remediating soil heavy metal pollution. Although they can adsorb and passivate certain heavy metals, this is because iron-based materials may undergo polymerization, precipitation, or redox reactions, thereby affecting their adsorption ability and long-term effect on heavy metals. In addition, most current soil remediation methods fail to effectively prevent the secondary release of heavy metals during the process of removing or fixing heavy metals. Especially in an environment containing reducing microorganisms, heavy metals often release back into the soil solution due to reduction reactions, forming secondary pollution. For example, iron-based materials may react with reducing bacteria in the soil, resulting in the reduction and dissolution of iron minerals, and then releasing the adsorbed heavy metals, leading to a decline in the remediation effect. Therefore, most current heavy metal soil remediation materials or methods have different limitations, such as being unable to take into account the removal of anions and cations, having poor long-term adsorption effects, or being unable to simultaneously meet soil remediation and soil nutrient protection. Summary of the Invention

[0004] The present invention aims to at least solve one of the above technical problems existing in the prior art. For this purpose, the object of the present invention is to provide a composite gel material, which uses chitosan, modified ferric oxyhydroxide, and a cross-linking agent as the main preparation raw materials, can effectively adsorb heavy metal ions, and at the same time achieve the effects of water retention, fertilizer retention, and acidification mitigation, and has a stable heavy metal passivation effect, avoiding the problem of secondary pollution.

[0005] The second aspect of the present invention lies in providing a preparation method of the composite gel material.

[0006] The third aspect of the present invention lies in providing a soil remediation material.

[0007] The fourth aspect of the present invention lies in providing a soil remediation method.

[0008] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0009] The first aspect of the present invention provides a composite gel material, and the raw materials for preparation include chitosan, modified ferric oxyhydroxide, and a crosslinking agent; the modified ferric oxyhydroxide is aluminum ion-doped ferric oxyhydroxide.

[0010] In the composite gel material of the present invention, chitosan, as a natural organic substance, can improve the water retention and fertilizer retention capabilities of the soil. By using a crosslinking agent to enhance the network structure of chitosan, the resulting gel helps to reduce nutrient loss and ensure soil fertility. At the same time, the composite gel material contains modified ferric oxyhydroxide, which is aluminum-doped ferric oxyhydroxide. The transition metal aluminum ions undergo isomorphous substitution with the iron atoms on the ferric oxyhydroxide, which will cause the lattice arrangement of the ferric oxyhydroxide to be disordered, forming a large number of structural defects and highly active oxygen vacancies. Therefore, it can provide a large number of adsorption sites, and the adsorption and passivation effects on heavy metals can be improved by the enhanced surface defects. Its oxidation ability for arsenic is also beneficial to inhibiting the migration of arsenic, making it difficult for the already adsorbed and fixed heavy metal ions to be released secondarily. And because the modified ferric oxyhydroxide exists in the gel, the gel network structure effectively isolates the ferric oxyhydroxide from contact with the reducing bacteria in the environment containing reducing microorganisms, avoiding the reduction and dissolution of ferric oxyhydroxide caused by the reduction reaction, thereby reducing the secondary pollution of heavy metals. Heavy metal ions belong to single atoms or molecules, and their sizes are much smaller than those of reducing bacteria. Therefore, while effectively isolating the reducing bacteria, the gel does not hinder the adsorption of heavy metal ions. In addition, the network structure of the gel not only maintains the stability of the ferric oxyhydroxide but also avoids the aggregation and precipitation of the modified ferric oxyhydroxide, enhancing its dispersibility and stability in the soil, thus realizing the synergistic promotion effect of soil remediation and heavy metal passivation.

[0011] Therefore, the composite gel material provided by the present invention can solve multiple problems in the remediation of soil heavy metal pollution, such as heavy metal removal and soil nutrient protection, and has important practical application significance, especially in the fields of agricultural pollution control, soil health restoration, and environmental protection, etc., with broad application prospects.

[0012] It should be noted that chitosan finally exists in the composite gel material in the form of chitosan hydrochloride.

[0013] In some embodiments of the present invention, in the composite gel material, the mass concentration of the crosslinking agent is 0.4 - 1.2%.

[0014] In some embodiments of the present invention, in the composite gel material, the mass concentration of the crosslinking agent is 0.5 to 1%.

[0015] The concentration of the crosslinking agent affects the gel network structure of the composite gel material and affects the water retention and fertilizer retention effects.

[0016] In some embodiments of the present invention, the crosslinking agent includes at least one of glutaraldehyde and sucralose.

[0017] In some embodiments of the present invention, the specific surface area of the composite gel material is 700 to 1000 m 2 / g.

[0018] In some embodiments of the present invention, the specific surface area of the composite gel material is 750 to 960 m 2 / g.

[0019] The second aspect of the present invention provides a preparation method of the composite gel material described in the first aspect of the present invention, including the following steps:

[0020] Mix modified ferric oxyhydroxide with a chitosan solution, add a crosslinking agent, and carry out a crosslinking reaction to obtain the composite gel material.

[0021] During the preparation process of the present invention, the modified ferric oxyhydroxide is fully mixed with the chitosan solution, so that the modified ferric oxyhydroxide is completely dispersed in the chitosan solution, and no undissolved particles should appear during the process.

[0022] After adding the crosslinking agent, the mixture of the modified ferric oxyhydroxide and the chitosan solution will gradually become viscous and form a gel. This is because a chemical reaction occurs between the amino group and the aldehyde group of the crosslinking agent and the chitosan molecule, forming a stable crosslinked network structure and enhancing the chemical stability of the gel.

[0023] In some embodiments of the present invention, the mass concentration of chitosan in the chitosan solution is 1 to 3%.

[0024] In some embodiments of the present invention, the solvent of the chitosan solution includes an acetic acid solution; the pH of the acetic acid solution is 4 to 6.

[0025] In some embodiments of the present invention, the precipitating agent includes sodium hydroxide; the concentration of the sodium hydroxide is 4 to 6 mol / L.

[0026] In some embodiments of the present invention, the time of the crosslinking reaction is 1.5 to 2.5 h.

[0027] In some embodiments of the present invention, the preparation method of the modified ferric oxyhydroxide includes the following steps:

[0028] Mix a ferric salt solution and an aluminum salt solution, add a precipitant to carry out a precipitation reaction to obtain a precipitate, and purify it to obtain the modified iron oxyhydroxide.

[0029] In some embodiments of the present invention, the ferric salt includes ferric chloride; the aluminum salt includes aluminum chloride; the molar ratio of the ferric chloride to the aluminum chloride is 1:(0.2 - 0.7).

[0030] In some examples of the present invention, the molar ratio of the ferric chloride to the aluminum chloride is 1:(0.3 - 0.5).

[0031] Specifically, the molar ratio of the ferric chloride to the aluminum chloride can be 1:0.3, 1:0.4, 1:0.5 or 1:0.7.

[0032] In some embodiments of the present invention, the end point pH of the precipitation reaction is 7.0 - 7.5.

[0033] In some embodiments of the present invention, the purification method includes dialysis.

[0034] In some examples of the present invention, the dialysis step includes dispersing the precipitate in water and performing dialysis using a dialysis bag with a cut-off molecular weight of 95 - 105 KD; the dialysis time is 70 - 75 h.

[0035] In some embodiments of the present invention, an aging step is further included after purification.

[0036] In some examples of the present invention, the aging temperature is 65 - 75 °C; the aging time is 55 - 65 h.

[0037] The third aspect of the present invention provides a soil remediation material, including the composite gel material described in the first aspect of the present invention, or the composite gel material prepared by the preparation method described in the second aspect of the present invention.

[0038] To solve the problems of soil heavy metal pollution and soil protection, generally, a soil remediation material is required to improve the physical and chemical properties of the soil while remediating heavy metals, especially enhancing the water and fertilizer retention capacity of the soil, so as to reduce the loss of nutrients during the remediation process and ensure the soil fertility and plant growth conditions. The composite gel material of the present invention forms a gel network structure through chitosan and a cross-linking agent, and at the same time loads modified iron oxyhydroxide, and has good water and fertilizer retention properties, and can enhance the water and fertilizer retention capacity of the soil.

[0039] In addition, the composite gel material of the present invention has a long-term fixation and passivation effect on heavy metal ions. The gel network structure is combined with modified ferric oxyhydroxide, which avoids the aggregation precipitation and reduction dissolution of ferric oxyhydroxide. While avoiding the secondary release of heavy metals, it can maintain or enhance its adsorption capacity.

[0040] The fourth aspect of the present invention provides a soil remediation method, which uses the composite gel material described in the first aspect of the present invention or the soil remediation material described in the third aspect of the present invention for soil remediation.

[0041] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0042] The composite gel material of the present invention uses chitosan, modified ferric oxyhydroxide and a cross-linking agent as raw materials for preparation. The modified ferric oxyhydroxide has abundant adsorption sites, and the gel formed by chitosan and the cross-linking agent has chemical stability and good water and fertilizer retention effects on the soil. The obtained composite gel material has a high adsorption capacity and high adsorption efficiency for heavy metal ions, can be used as a soil remediation material, can solve the problem of soil nutrient loss while repairing heavy metal pollution, ensure the soil fertility and plant growth conditions, and reduce the risk of secondary pollution. Specific Embodiments

[0043] The content of the present invention will be further described in detail below through specific examples. The raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial channels or can be obtained by existing technical methods without special instructions. Unless otherwise specified, the test or measurement methods are conventional methods in the art.

[0044] The following will be described in detail in combination with specific examples and comparative examples.

[0045] Example 1

[0046] A composite gel material, the raw materials for preparation include chitosan, modified ferric oxyhydroxide and a cross-linking agent glutaraldehyde; wherein, the modified ferric oxyhydroxide is aluminum ion-doped ferric oxyhydroxide; the mass concentration of glutaraldehyde in the composite gel material is 1%;

[0047] The preparation method of the composite gel material includes the following steps:

[0048] S1. Preparation of modified ferric oxyhydroxide:

[0049] The ferric chloride and aluminum chloride solutions (molar ratio 1:0.5, chloride ion concentration 4.5 mol / L) were fully mixed, and then a precipitant sodium hydroxide (5 mol / L) was added dropwise, and the magnetic stirring speed was maintained at 150 rpm; when the mixed solution of ferric chloride and aluminum chloride began to coprecipitate, the temperature of the mixed solution was continued to be controlled at 25° C. until the pH value of the mixed solution increased to 8.0, the addition of the precipitant was stopped, and then the magnetic stirring was maintained at 150 rpm for 3 hours;

[0050] After the mixture is stirred, it is centrifuged to obtain a precipitate, which is dispersed in deionized water and placed in a dialysis bag with a molecular weight cutoff of 100KD. The dialysis bag is used for purification to remove the residual solvent, unreacted ions and other impurities in the precipitate suspension; the dialysis time is 72 hours;

[0051] The obtained precipitate suspension after purification was placed in an oven and aged at 70°C for 60 hours to obtain modified iron oxide hydroxide with rich surface defects;

[0052] S2. Mixing of modified ferric hydroxide and chitosan:

[0053] 15 g of chitosan was dissolved in an acetic acid solution (pH = 5), stirred until completely dissolved, and undissolved particles were avoided to form a transparent chitosan solution (mass concentration of 3%); then the chitosan solution was fully mixed with 1 g of modified ferric hydroxide to make the modified ferric hydroxide completely dispersed in the chitosan solution, wherein the mass ratio of chitosan to modified ferric hydroxide was 15:1; the specific surface area of the modified ferric hydroxide was 367 m 2 / g;

[0054] S3. Crosslinker reaction to form gel:

[0055] The crosslinking agent glutaraldehyde is dissolved in deionized water, and then added to the chitosan solution containing modified ferric hydroxide obtained in step S2 to form a precursor solution, and stirred evenly to ensure that the crosslinking agent is fully distributed; the mass concentration of the crosslinking agent in the precursor solution is 1%, and the mass ratio of chitosan to modified ferric hydroxide is 15:1; the precursor solution is allowed to stand for 2 hours to allow the crosslinking reaction to proceed fully, and a composite gel material is obtained; the specific surface area of the composite gel material is 959m 2 / g.

[0056] Example 2

[0057] A composite gel material and a preparation method thereof, which are different from Example 1 in that: the mass concentration of the crosslinking agent in the composite gel material is 0.5%; in the preparation method thereof, the mass concentration of the crosslinking agent in the precursor solution is 0.5%.

[0058] Example 3

[0059] A composite gel material and its preparation method. The preparation raw materials are the same as those in Example 1, except that in the preparation process of the modified ferric oxyhydroxide, the molar ratio of ferric chloride to aluminum chloride is 1:0.3; the specific surface area of the obtained modified ferric oxyhydroxide is 253 m 2 / g, and the specific surface area of the composite gel material is 753 m 2 / g.

[0060] Comparative Example 1

[0061] A chitosan gel. The difference in its preparation method from that of Example 1 is that the modified ferric oxyhydroxide is not added; the specific surface area of this chitosan gel is 561 m 2 / g.

[0062] Comparative Example 2

[0063] A chitosan gel. The difference in its preparation method from that of Example 2 is that the modified ferric oxyhydroxide is not added.

[0064] Comparative Example 3

[0065] A ferric oxyhydroxide. The difference in its preparation method from step S1 of Example 1 is that aluminum chloride is not added; the rest is the same as step S1 of Example 1; the specific surface area of this ferric oxyhydroxide is 116 m 2 / g.

[0066] Test Example

[0067] Using the gel materials obtained in the examples and comparative examples as soil remediation materials, the soil samples were taken from Yingtan City, Jiangxi Province (28°8′39″ N, 116°47′21″ E), the surface soil of 0 - 20 cm. The collected soil samples were air-dried and passed through a 2 mm sieve for subsequent soil experiments, and their physical and chemical properties are shown in Table 1. At the same time, control groups were set up by replacing the gel materials with the raw materials used in the examples and comparative examples, and the materials used for different control groups are shown in Table 2 below.

[0068] Table 1 Physical and Chemical Properties of the Soil for the Experiment

[0069]

[0070]

[0071] Table 2 Raw Materials for Replacing the Gel Materials in Different Control Groups

[0072]

[0073] At the same time, a group containing only the same soil without adding any gel material or its raw materials was set as the blank control group.

[0074] The specific test methods are as follows:

[0075] 1. Take equal amounts of materials in the examples, comparative examples, and each control group and add them to the same soil respectively for soil nutrient protection tests:

[0076] Water retention test: By simulating drought conditions (temperature 40°C, humidity 35%), record the changes in soil water content in different groups, measure the soil water evaporation rate within 48 hours, and thus obtain the water retention rate.

[0077] Fertilizer retention test: Apply standard fertilizer (nitrogen, phosphorus, potassium ternary compound fertilizer, total nutrient mass content is 35%, nitrogen, phosphorus, potassium mass ratio is 1:3:2, mixed fertilizer application amount is 5g), record the fertilizer release rate after fertilization, and use the soil extraction method to analyze the fertilizer residue amount at 48 hours after fertilization to obtain the fertilizer retention rate; fertilizer retention rate = fertilizer residue amount at 48 hours / fertilizer application amount × 100%.

[0078] Soil organic matter content: Dry the soil sample and take an appropriate amount (2g); put the sample into a high-temperature furnace and heat it at 550°C for more than 4 hours; calculate the organic matter content through the reduction of the sample mass. Organic matter content (%) = (initial soil mass - soil mass after incineration) / (initial soil mass)

[0079] 2. Heavy metal ion removal test:

[0080] Add a solution containing heavy metal ions Pb 2+ , Cu 2+ , Cd 2+ and As (arsenite) to the soil, mix evenly, and after the soil adsorbs for 1 hour, add the materials in the examples, comparative examples, and each control group to the soil. After reacting for 1 hour, analyze and calculate the changes in heavy metal ion concentration. During the adsorption process, the pH is between 6.0 and 7.4, and the Eh is between 251 and 260 mV. Calculate the adsorption amount according to the adsorption rate equation of the adsorption isotherm.

[0081] 3. Oxidation ability test for trivalent arsenic:

[0082] Use the same method as in "2. Heavy metal ion removal test" to make the soil carry out an adsorption test, then extract the arsenic existing in the soil with hydrochloric acid, and then use a liquid chromatography atomic fluorescence spectrometer (LC-AFS) to test the arsenic valence state to obtain the concentrations of trivalent arsenic and pentavalent arsenic. Trivalent arsenic oxidation rate = trivalent arsenic concentration / (trivalent arsenic concentration + pentavalent arsenic concentration) × 100%.

[0083] The test results are shown in Tables 3 to 6.

[0084] Table 3 Soil nutrient protection test results

[0085]

[0086] As can be seen from Table 3, when the composite gel material obtained in the embodiments of the present invention is used as a soil remediation material, it can effectively ensure the nutrients of the soil, has good water and fertilizer retention effects, can significantly improve the water retention capacity of the soil, and the soil organic matter content is also increased. Compared with the blank control group without using any soil remediation material, its water retention rate and fertilizer retention rate are increased by at least 20%. And as the mass concentration of the cross-linking agent rises from 0.5% to 1%, the water retention rate of the soil after use rises from 65% to 72%. In Comparative Example 1 and Comparative Example 2, modified ferric oxyhydroxide was not added, and only chitosan gel was used. The water retention rate and fertilizer retention rate were both lower than those of the examples, and the soil organic matter content was also lower. In Control Group 1 and Control Group 2, chitosan or modified ferric oxyhydroxide was used alone, and the effects were worse than those of Examples 1-2 and Comparative Examples 1-2. This indicates that the combination of modified ferric oxyhydroxide and chitosan gel helps the slow release and stability of soil organic matter after fertilization, and can improve the water retention effect of the soil.

[0087] Table 4 Test Results of Heavy Metal Ion Adsorption Capacity

[0088]

[0089]

[0090] Table 5 Test Results of Heavy Metal Ion Adsorption Efficiency

[0091]

[0092] As can be seen from Table 4 and Table 5, when the composite gel material of the present invention is used as a soil remediation material, both the adsorption capacity and adsorption efficiency for heavy metal ions are significantly improved. The adsorption capacity for arsenic is not less than 60%, and the adsorption efficiency is not less than 90%. And the adsorption efficiencies for Pb 2+ , Cu 2+ , Cd 2+ also all reach more than 70%, which are significantly higher than those of the comparative examples and control groups. At the same time, by comparing Example 1 and Example 3, it can be seen that as the molar ratio of ferric chloride to aluminum chloride decreases, the adsorption efficiency of the obtained composite gel material for heavy metal ions in the soil increases. It should be noted that the adsorption efficiency of the blank control group is the adsorption efficiency of the ions by the adsorption of the soil itself after the heavy metal ions are added to the soil.

[0093] In addition, the addition of the cross-linking agent endows the formed chitosan gel with an amorphous structure having a larger adsorption surface, and the modified iron oxyhydroxide also has more adsorption sites. Therefore, it can adsorb more heavy metal ions, and has a better anchoring effect, avoiding the rapid desorption of the adsorbed heavy metal ions. At the same time, the protection of the gel for the modified iron oxyhydroxide also avoids the problem of desorption caused by the action of reducing bacteria in the soil environment on the modified iron oxyhydroxide, resulting in secondary pollution.

[0094] Table 6 Test results of arsenic oxidation ability

[0095]

[0096]

[0097] As can be seen from Table 6, using the composite gel material of the present invention as a soil remediation material has excellent arsenic oxidation ability. For example, Examples 1 and 3 in Table 6 show significant advantages in arsenic oxidation, can effectively oxidize As(III) to As(V), and the arsenic oxidation rate is not less than 70%. Moreover, the arsenic oxidation rate increases with the increase of the aluminum doping amount. This is because the active oxygen vacancies on the surface of the iron oxyhydroxide modified by aluminum doping enable it to catalyze the oxidation reaction of arsenic, and the chitosan gel provides a stable environment, which helps to improve the efficiency of the oxidation reaction. In contrast, the blank soil group without adding any remediation material can only achieve 20% arsenic oxidation.

[0098] In summary, the composite gel material provided by the present invention can be used as a soil remediation material for the remediation of heavy metal-polluted soil. It can effectively adsorb heavy metal ions, promote the oxidation of arsenic, enhance the treatment effect of arsenic, and has a good fixation effect on heavy metals, which is beneficial to preventing the migration and pollution of heavy metals. At the same time, it also significantly improves the water retention and fertilizer retention of the soil, solving the problem that the existing soil remediation materials cannot simultaneously meet the requirements of soil remediation and soil nutrient protection. It is an effective measure for soil pollution treatment and heavy metal remediation.

[0099] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A composite gel material, characterized in that, The preparation raw materials include chitosan, modified iron oxyhydroxide, and a crosslinking agent; the modified iron oxyhydroxide is aluminum ion-doped iron oxyhydroxide.

2. The composite gel material according to claim 1, characterized in that In the composite gel material, the mass concentration of the crosslinking agent is 0.4-1.2%; and / or, the crosslinking agent includes at least one of glutaraldehyde and sucralose.

3. A method for preparing the composite gel material according to claim 1 or 2, characterized in that, It includes the following steps: Mix the modified iron oxyhydroxide with the chitosan solution, add the crosslinking agent, and carry out a crosslinking reaction to obtain the composite gel material.

4. The preparation method according to claim 3, characterized in that, The preparation method of the modified iron oxyhydroxide includes the following steps: Mix the ferric salt solution and the aluminum salt solution, add a precipitating agent to carry out a precipitation reaction to obtain a precipitate, and purify it to obtain the modified iron oxyhydroxide.

5. The preparation method according to claim 4, wherein The ferric salt includes ferric chloride; the aluminum salt includes aluminum chloride; the molar ratio of ferric chloride to aluminum chloride is 1:(0.2-0.7).

6. The preparation method according to claim 3, characterized in that, The mass concentration of chitosan in the chitosan solution is 1-3%.

7. The preparation method according to claim 4, characterized in that, The end point pH of the precipitation reaction is 7.0-7.

5.

8. The preparation method according to claim 4, characterized in that, The purification method includes dialysis; and / or, an aging step is further included after the purification.

9. A soil remediation material, characterized in that, It includes the composite gel material according to any one of claims 1-2, or the composite gel material prepared by the preparation method according to any one of claims 3-8.

10. A soil remediation method, characterized in that, Use the composite gel material according to any one of claims 1-2 or the soil remediation material according to claim 9 for soil remediation.

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