Method for remediation of heavy metal-contaminated humus soil and humus soil obtained by the method

Abstract

The present application belongs to the field of resource utilization of landfill humus, and particularly relates to a method for repairing heavy metal contaminated humus in a landfill and the humus obtained by the method. The method comprises adding a strong oxidizing agent, acid and gel material into the heavy metal contaminated humus, and then removing heavy metal ions under certain conditions to obtain inorganic mineral mud slurry precipitate free of heavy metals, and extracting humic acid. Finally, the extracted humic acid is added into the inorganic mineral mud slurry precipitate free of heavy metals to obtain the repaired humus. The method is simple and easy to operate, does not need to add soil conditioner, has low cost, good repair effect, high content of recovered heavy metal ions, and is conducive to further treatment and resource utilization. The humus obtained by the method does not contain heavy metals and bacteria, is rich in humic acid, can be used as high-quality nutrient soil, and is conducive to further resource utilization of the humus.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of resource utilization of landfill humus, and particularly relates to a method for repairing heavy metal contaminated humus in a landfill and humus obtained by the method. BACKGROUND

[0002] When domestic waste enters the landfill, electronic components, batteries, paints, and oil paints with high heavy metal content are also buried together with the domestic waste due to the lack of classification, which makes the heavy metal content in the humus of the landfill high. The heavy metals entering the humus mainly exist in the forms of water-soluble state, exchange state, carbonate combined state, organic combined state, iron and manganese oxide combined state, and residual state. Among them, the heavy metal ions in the water-soluble state and the exchange state are more easily absorbed by plants and have the strongest toxicity. The carbonate combined state heavy metal ions are most sensitive to pH value and are easily released into the environment when the pH value decreases. The organic combined state heavy metal is integrated with various organic matters such as animal and plant residues and humus in the soil, and the organic matter in nature is easily decomposed after a long time, thereby causing the heavy metal to be released. The iron and manganese oxide combined state heavy metal is adsorbed by the specific exchange position of the soil iron and manganese oxide or clay mineral, and can only be replaced by metal ions with similar or stronger affinity, and can exist stably. The residual state heavy metal generally exists in the soil lattice of silicate, primary and secondary minerals, and is not easily released under normal conditions in nature, and can be stably present in sediments for a long time.

[0003] Therefore, to reduce the toxicity of heavy metals in humus, the focus is on reducing the content of heavy metals in the water-soluble state, exchange state, carbonate combined state, and organic combined state. The humus contaminated by heavy metals generally does not have natural self-purification ability, and the current heavy metal pollution treatment methods including primary membrane separation, adsorption, ion exchange, leaching, chemical precipitation, and electrodynamic repair are used to purify and remove, such as Chinese patent CN111760902B (right), Chinese patent application CN116836706A (disclosed), but the humus contains a lot of organic colloid, which can form a package for the water-soluble state, exchange state, and carbonate heavy metal salt in the humus, and the chelate formed by humic acid and heavy metal can inhibit the migration of heavy metal, so it is difficult to remove the heavy metal in the humus well by this method.

[0004] Some researchers have also removed heavy metals by adding soil conditioners. For example, Chinese patent CN104560047B (authorized) discloses adding heavy metal passivators to the soil. These heavy metal passivators include humic acid, thiol compounds, etc. However, this method can only reduce the absorption of heavy metals, especially mercury, by plants and cannot remove heavy metals from humus soil. Moreover, this method requires the addition of a large amount of additional reagents, and there is also the problem of high treatment costs. For example, Chinese patent CN103706624B (authorized) discloses a method for remediating heavy metal-contaminated soil. This method treats the heavy metals in the humus soil by spreading 1 to 5 cm of humic acid on the surface of the contaminated soil. However, the humus soil only contains a small amount of free heavy metal ions, which are coated with a large amount of organic colloids, resulting in poor heavy metal removal. Another example is Chinese patent application CN 104492803 A, which discloses a cleaning method for remediating heavy metal-contaminated soil. This method involves treating the contaminated soil with water, an oxidant, an acid, and a salt, followed by solid-liquid separation. A flocculant is then added to the separated liquid to precipitate the heavy metal ions, which are then filtered to remove the heavy metals. However, after the strong oxidant and acid treatment, the heavy metals chelate with humic acid and are present in large quantities in the separated solid. The ionic heavy metal content in the separated liquid is relatively low, resulting in limited heavy metal removal. Summary of the Invention

[0005] In order to solve the technical problems in the prior art that humus soil in landfills contains a large amount of heavy metals that are not conducive to reuse, and that heavy metals are difficult to precipitate and migrate due to the presence of organic colloids and humic acid in the humus soil, and that the use of soil conditioners leads to high treatment costs and complicated treatment processes, the present invention proposes a method for repairing humus soil contaminated by heavy metals and the humus soil obtained by the method.

[0006] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0007] The first aspect of the present invention provides a method for remediating heavy metal-contaminated humus soil, comprising the following steps:

[0008] S1. Add a strong oxidant to the humus soil, add acid solution to adjust the pH to 1-4, then add a gel material to react, and then separate the organic and inorganic matter to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral slurry precipitate;

[0009] S2. Adding alkaline solution to the organic precipitate containing heavy metal-humic acid chelate obtained in step S1 to adjust its pH to 12-14 for reaction, allowing it to settle and then performing solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0010] S3, adding part of the sodium humate-containing alkaline solution obtained in step S2 to the acid inorganic mineral slurry obtained in step S1 to adjust the pH value to 7-8, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0011] S4, adding an acid to the remaining sodium humate-containing alkaline solution obtained in step S2 to adjust the pH value to 6.0-7.0, and then performing solid-liquid separation to obtain humic acid;

[0012] S5, adding the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain a remediated post-humus soil.

[0013] In some embodiments, the strong oxidizing agent in step S1 is at least one of a sodium hypochlorite solution and a hydrogen peroxide solution, and the concentration of the strong oxidizing agent is 0.01-0.5 mol / L.

[0014] In some embodiments, the acid in step S1 is selected from any one of a hydrochloric acid solution, a sulfuric acid solution, and a nitric acid solution, and the concentration of the acid is 0.5-2 mol / L.

[0015] In some embodiments, the solid-liquid ratio of the humus added in step S1 to the strong oxidizing agent added in step S1 is 1:2-5, and the mass ratio of the strong oxidizing agent to the acid added in step S1 is 1:1-8.

[0016] In some embodiments, the gel material in step S1 is at least one of hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose, and hydroxypropyl methyl cellulose.

[0017] In some embodiments, the concentration of the gel material in the system after the gel material is added in step S1 is 0.1-0.5 g / L.

[0018] In some embodiments, the reaction time in step S1 is 6-12 h.

[0019] In some embodiments, the method for separating the organic and inorganic matter in step S1 is to use a rotating spiral chute for separation.

[0020] In some embodiments, the spiral chute has an outer diameter of 300-1500 mm, a transverse inclination angle of 7-12°, a pitch of 200-1000 mm, and 5-12 turns; the inorganic mineral slurry and the organic matter precipitate containing heavy metal-humic acid chelates can be more thoroughly separated by taking advantage of the difference in specific gravity between the inorganic mineral slurry and the organic matter precipitate containing heavy metal-humic acid chelates.

[0021] In some embodiments, the alkali solution in step S2 is a strong alkali solution selected from at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 0.5-2 mol / L.

[0022] In some embodiments, the time for the standing precipitation in step S2 is 6-12 h, and after the standing, the supernatant is removed to realize the solid-liquid separation.

[0023] In some embodiments, the temperature of the reaction in step S2 is 60-98 ℃, and the reaction time is 3-6 h.

[0024] In some embodiments, the water content of the heavy metal-free inorganic mineral slurry in step S3 is 30-80%.

[0025] In some embodiments, the acid solution in step S4 is selected from any one of a hydrochloric acid solution, a sulfuric acid solution and a nitric acid solution.

[0026] In a second aspect of the present application, a humus soil prepared by any one of the above methods is provided.

[0027] The method of the present application has the following beneficial effects:

[0028] (1) The present application can separate the heavy metals in the heavy metal-polluted landfill humus soil by adding a strong oxidant, an acid solution and a gel material to react, separating the organic and inorganic matters and treating with an alkali solution, etc., so that the humus soil with very low content of heavy metals and bacteria and rich in humic acid is obtained. The humus soil can be used as high-quality nutrient soil, and the resource utilization of the humus soil is facilitated, and the added value of the landfill humus soil is improved.

[0029] (2) The method for repairing the heavy metal-polluted humus soil provided by the present application is simple and easy to operate, and no additional soil conditioner or other reagent is added in the treatment process, no harmful components are introduced, the treatment cost is low, the repairing effect on the landfill humus soil is good, and the large-scale treatment of the landfill humus soil can be realized.

[0030] (3) The heavy metal ions separated by the method of the present application are concentrated in the organic matter precipitate, which is beneficial to the further treatment and resource utilization of the separated heavy metals.

[0031] Other beneficial effects of the embodiments of the present application will be further described below. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The flow chart of the method for repairing the heavy metal-polluted humus soil according to the embodiments of the present application is shown. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0034] The embodiment of the present invention adds a strong oxidant, acid solution and gel material to the heavy metal contaminated humus soil, then removes the heavy metal ions through specific treatment under certain conditions to obtain the Wuji mineral mud without heavy metals and extracts humic acid, and finally adds the extracted humic acid to the Wuji mineral mud without heavy metals to obtain the repaired humus soil, thereby realizing the repair of the heavy metal contaminated landfill humus soil.

[0035] The method is simple and easy to operate, does not require the addition of additional soil conditioners, has low cost, and has a good remediation effect. The obtained heavy metal-containing organic matter precipitate has a high content of heavy metal ions, which is conducive to further treatment and resource utilization. The humus soil obtained after treatment using this method has an extremely low heavy metal content, does not contain toxic and harmful substances such as pathogens, and contains more humic acid and other substances. It can be used as high-quality nutrient soil and can better realize the resource utilization of humus soil.

[0036] The embodiment of the present invention shows a method for repairing heavy metal-contaminated humus soil, comprising the following steps:

[0037] S1. Add a strong oxidant to the humus soil, add acid solution to adjust the pH to 1-4, then add a gel material to react, and then separate the organic and inorganic matter to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral slurry precipitate;

[0038] S2. Adding alkaline solution to the organic precipitate containing heavy metal-humic acid chelate obtained in step S1 to adjust its pH to 12-14 for reaction, allowing it to settle and then performing solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0039] S3, adding a portion of the alkaline solution containing sodium humate obtained in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1 to adjust the pH value thereof to 7-8, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0040] S4, adding acid to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 6.0-7.0, and performing solid-liquid separation to obtain humic acid;

[0041] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0042] Wherein, in step S1, the strong oxidant is at least one of sodium hypochlorite solution and hydrogen peroxide solution, and the concentration of the strong oxidant is 0.01-0.5 mol / L; the acid solution is selected from any one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution, and the concentration of the acid solution is 0.5-2 mol / L; the solid-liquid ratio of the humus soil and the added strong oxidant in step S1 is 1:2-5, and the mass ratio of the added strong oxidant to the added acid solution is 1:1-8; the gel material is at least one of hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose and hydroxypropyl methyl cellulose; after the gel material is added, the concentration of the gel material in the system is 0.1-0.5 g / L; the reaction time is 6-12 hours; the method for separating organic and inorganic matter is to use a rotating spiral chute for separation. The outer diameter of the spiral chute is 300-1500 mm, the lateral inclination angle is 7-12 degrees, the pitch is 200-1000 mm, and the number of turns is 5-12 turns. By utilizing the difference in specific gravity between the inorganic mineral slurry and the organic precipitate containing heavy metal-humic acid chelates, the inorganic mineral slurry and the organic precipitate containing heavy metal-humic acid chelates can be separated more thoroughly.

[0043] In step S2, the alkali solution is at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 0.5 to 2 mol / L. The reaction temperature is 60 to 98°C, and the reaction time is 3 to 6 hours. The static precipitation time is 6 to 12 hours. After static precipitation, the supernatant is removed to achieve solid-liquid separation.

[0044] In step S3, the water content of the inorganic mineral slurry precipitate containing no heavy metals is 30-80%.

[0045] In step S4, the acid solution is selected from any one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution.

[0046] The embodiment of the present invention also shows a humus soil obtained by the above method.

[0047] Example 1

[0048] S1, to 100 parts of humus soil, 300 parts of 0.05 mol / L sodium hypochlorite solution were added, and 1 mol / L hydrochloric acid solution was added to adjust the pH to 2.5 and react for 6 hours, and then hydroxyethyl cellulose was added to the system until the concentration of hydroxyethyl cellulose was 0.3 g / L, and then the organic and inorganic matter were separated by a spiral chute to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral mud precipitate;

[0049] S2. Add 1 mol / L sodium hydroxide solution to the heavy metal-humic acid chelate organic precipitate obtained in step S1, adjust its pH to 13, react at 80° C. for 6 h, then let it stand for 12 h to precipitate, and then perform solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0050] S3, adding the alkaline solution containing humic acid in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1, adjusting the pH value thereof to 7.0, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0051] S4, adding hydrochloric acid solution to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 7.0, and obtain humic acid by solid-liquid separation;

[0052] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0053] Example 2

[0054] S1, to 100 parts of humus soil, 300 parts of 0.3 mol / L hydrogen peroxide were added, and 2 mol / L nitric acid solution was added to adjust the pH to 1.0 and react for 6 hours, and then carboxymethyl hydroxyethyl cellulose was added until the concentration of acrylamide in the system was 0.1 g / L, and then the organic and inorganic matter were separated by a spiral chute to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral mud precipitate;

[0055] S2. Add 0.5 mol / L sodium hydroxide solution to the heavy metal-humic acid chelate organic precipitate obtained in step S1, adjust its pH to 12, react at 60° C. for 6 h, then let it stand for 12 h to precipitate, and then perform solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0056] S3, adding the alkaline solution containing humic acid in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1, adjusting the pH value thereof to 7.5, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0057] S4, adding nitric acid solution to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 6.0, and obtain humic acid by solid-liquid separation;

[0058] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0059] Example 3

[0060] S1, to 100 parts of humus soil, 300 parts of 0.5 mol / L sodium hypochlorite solution were added, and 0.5 mol / L sulfuric acid solution was added to adjust the pH to 4 and react for 6 hours, and then methyl hydroxyethyl cellulose was added until the concentration of acrylic acid in the system was 0.5 g / L, and then the organic and inorganic matter were separated by a spiral chute to obtain an organic precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral mud precipitate;

[0061] S2. Add 2 mol / L sodium hydroxide solution to the heavy metal-humic acid chelate organic precipitate obtained in step S1, adjust its pH to 12, react at 98° C. for 6 h, then let it stand for 12 h to precipitate, and then perform solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0062] S3, adding the alkaline solution containing humic acid in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1, adjusting the pH value thereof to 8, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0063] S4. Add sulfuric acid solution to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 6.5, and obtain humic acid by solid-liquid separation;

[0064] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0065] Comparative Example 1

[0066] S1. Add 300 parts of water to 100 parts of humus soil, add 1 mol / L hydrochloric acid to adjust the pH to 2.5 and react for 6 hours, then add hydroxyethyl cellulose to the system until the concentration of hydroxyethyl cellulose is 0.3 g / L, and then separate the organic and inorganic matter through a spiral chute to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral mud precipitate;

[0067] S2. Add 1 mol / L sodium hydroxide solution to the heavy metal-humic acid chelate organic precipitate obtained in step S1, adjust its pH to 13, react at 80° C. for 6 h, then let it stand for 12 h to precipitate, and then perform solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0068] S3, adding the alkaline solution containing humic acid in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1, adjusting the pH value thereof to 7.0, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0069] S4, adding hydrochloric acid to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 7.0, and performing solid-liquid separation to obtain humic acid;

[0070] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0071] Comparative Example 2

[0072] S1, adding 300 parts of 0.05 mol / L sodium hypochlorite solution to 100 parts of humus soil, and adding 1 mol / L hydrochloric acid solution to adjust the pH to 2.5 and react for 6 hours, then separating the organic and inorganic matter through a spiral chute to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral mud precipitate;

[0073] S2. Add 1 mol / L sodium hydroxide solution to the heavy metal-humic acid chelate organic precipitate obtained in step S1, adjust its pH to 13, react at 80° C. for 6 h, then let it stand for 12 h to precipitate, and then perform solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals;

[0074] S3, adding the alkaline solution containing humic acid in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1, adjusting the pH value thereof to 7.0, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals;

[0075] S4, adding hydrochloric acid solution to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 7.0, and obtain humic acid by solid-liquid separation;

[0076] S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

[0077] The idea of ​​the present invention to solve the technical problem is:

[0078] First, strong oxidants and acid are added to destroy the colloidal structure formed by organic colloids in the humus soil, exposing the heavy metals wrapped in the colloids in the soil; then, under the action of the acid, the colloidal heavy metals are converted into ionic state and precipitated;

[0079] The precipitated heavy metal ions have the strongest chelation effect with humic acid under acidic conditions, thus achieving chelation between humic acid and precipitated heavy metals. After the addition of the gel material, since humic acid and other organic matter in the humus soil are rich in many oxygen-containing functional groups, such as carboxyl (-COOH) and hydroxyl (-OH), these functional groups are highly active and easily undergo dehydrogenation reactions and proton binding reactions, causing the carboxyl and hydroxyl groups in the humic acid to condense with the hydroxyl and / or carboxyl groups in the gel material, respectively, to produce macromolecular gel. Finally, heavy metals in the form of water-soluble, exchangeable, carbonate-bound, etc. in the soil are converted into heavy metal-humic acid chelate organic matter precipitation;

[0080] Then, by utilizing the difference in specific gravity between organic matter and inorganic minerals, the heavy metal-humic acid chelate organic matter precipitation and the inorganic mineral slurry precipitation are more thoroughly separated; in addition, the specific combination of acid and strong oxidant can more thoroughly kill harmful pathogens in the humus soil, thereby further rendering the humus soil harmless;

[0081] Then add alkali solution to the heavy metal-humic acid chelate organic matter precipitate. Under alkaline environment, the organic chelate structure formed by heavy metals and humic acid is destroyed, and the heavy metals in the humic acid are redissolved and form heavy metal-containing organic matter precipitate under alkaline environment. At the same time, small molecular humic acid can be produced, and further soluble sodium humate is generated. Humic acid is obtained after further adjustment by adding acid solution.

[0082] The organic matter and heavy metal contents in the humus soil of the landfill before treatment and the humus soil obtained in the examples and comparative examples were tested. The test results are shown in Table 1 and Table 2, respectively.

[0083] Table 1 Organic matter and heavy metal contents in landfill humus soil before treatment

[0084] Organic matter content Lead content Arsenic content Mercury content Cadmium content Copper content Chromium content 13.8％ 342.7mg / L 4.35mg / L 3.16mg / L 0.46mg / L 782.7mg / L 356.1mg / L

[0085] Table 2 Comparison of organic matter and heavy metal content in humus soil prepared in Examples and Comparative Examples

[0086] Test items Organic matter content Lead content Arsenic content Mercury content Cadmium content Copper content Chromium content Example 1 5.3％ 10.2mg / L 0.15mg / L 0.05mg / L 0.03mg / L 11.5mg / L 30.1mg / L Example 2 5.8％ 8.7mg / L 0.13mg / L 0.05mg / L 0.02mg / L 8.4mg / L 23.6mg / L Example 3 5.2％ 11.4mg / L 0.2mg / L 0.08mg / L 0.05mg / L 13.7mg / L 38.4mg / L Comparative Example 1 3.3％ 150.3mg / L 3.48mg / L 3.05mg / L 0.31mg / L 314.6mg / L 187.3mg / L Comparative Example 2 3.8％ 210.6mg / L 2.74mg / L 1.89mg / L 0.37mg / L 584.2mg / L 238.4mg / L

[0087] From the above test results, it can be seen that the method provided by the present invention is used to treat humus soil contaminated by heavy metals in landfills, and the removal effect of heavy metals is good. After treatment, the content of lead, arsenic, mercury, cadmium, copper and chromium in the humus soil is low. In Comparative Example 1, since acid-strong oxidant is not used to destroy the structure of organic colloid particles in the humus soil, the heavy metals wrapped by the colloid particles are difficult to be removed, and the organic colloid particles in the soil are closely combined with inorganic minerals, and the separation of organic and inorganic substances is not thorough, resulting in poor heavy metal removal effect; in Comparative Example 2, since no gel material is added, humic acid does not form a macromolecular gel and is more easily adsorbed by inorganic minerals in the soil. The separation of the formed inorganic organic matter is not thorough enough, which leads to the inorganic mineral slurry precipitation still containing a large amount of humic acid-heavy metal chelates, resulting in poor heavy metal removal effect.

Claims

1. A method for repairing humus soil contaminated by heavy metals, characterized in that: The following steps are involved: S1. Add a strong oxidant to the humus soil, add acid solution to adjust the pH to 1-4, then add a gel material to react, and then separate the organic and inorganic matter to obtain an organic matter precipitate containing heavy metal-humic acid chelate and an acidic inorganic mineral slurry precipitate; S2. Adding alkaline solution to the organic precipitate containing heavy metal-humic acid chelate obtained in step S1 to adjust its pH to 12-14 for reaction, allowing it to settle and then performing solid-liquid separation to obtain an alkaline solution containing sodium humate and an organic precipitate containing heavy metals; S3, adding a portion of the alkaline solution containing sodium humate obtained in step S2 to the acidic inorganic mineral slurry precipitate obtained in step S1 to adjust the pH value thereof to 7-8, and then performing solid-liquid separation to obtain an inorganic mineral slurry precipitate free of heavy metals; S4, adding acid to the alkaline solution containing sodium humate obtained in the remaining step S2 to adjust its pH value to 6.0-7.0, and performing solid-liquid separation to obtain humic acid; S5. Add the humic acid obtained in step S4 to the inorganic mineral slurry precipitate free of heavy metals obtained in step S3 to obtain repaired humus soil.

2. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: The strong oxidant in step S1 is at least one of a sodium hypochlorite solution and a hydrogen peroxide solution, and the concentration of the strong oxidant is 0.01 to 0.5 mol / L.

3. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: The acid solution in step S1 is selected from any one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution, and the concentration of the acid solution is 0.5-2 mol / L.

4. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: In step S1, the solid-liquid ratio of the humus soil and the added strong oxidant is 1:2-5, and the mass ratio of the added strong oxidant to the added acid solution is 1:1-8.

5. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: The gel material in step S1 is at least one of hydroxyethyl cellulose, carboxymethyl hydroxyethyl cellulose, methyl hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

6. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: After the gel material is added in step S1, the concentration of the gel material in the system is 0.1 to 0.5 g / L.

7. The method for repairing heavy metal-contaminated humus soil according to claim 1, characterized in that: The alkali solution in step S2 is at least one of a sodium hydroxide solution and a potassium hydroxide solution, and the concentration of the alkali solution is 0.5 to 2 mol / L.

8. The method for remediating heavy metal-contaminated humus soil according to claim 1, characterized in that: The method for separating the organic and inorganic substances in step S1 is to use a rotating spiral chute for separation.

9. The method for remediating heavy metal-contaminated humus soil according to claim 1, characterized in that: The reaction temperature in step S2 is 60-98° C., and the reaction time is 3-6 h.

10. Humus obtained by the method according to any one of claims 1 to 9.

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