Soil remediation agent as well as preparation method and application thereof

Abstract

The invention discloses a soil remediation agent as well as a preparation method and application thereof, and relates to the technical field of soil remediation. The preparation method of the soil remediation agent comprises the following steps: mixing papermaking black liquid with an alkaline solution containing calcium ions to obtain a mixed solution, filtering the mixed solution to obtain filter residues, and carbonizing to obtain the soil remediation agent. According to the preparation method of the soil remediation agent provided by the technical scheme of the invention, the black liquor waste is taken as a raw material, the soil remediation agent with a porous structure is prepared through a pyrolysis carbonization process, and the prepared soil remediation agent not only can improve the pH of acid soil and remarkably reduce the leaching concentration of heavy metal cadmium, but also can provide necessary nutritional ingredients for crops. The preparation method of the soil remediation agent provided by the technical scheme of the invention realizes efficient recycling of the papermaking black liquid, and can be used for solving the problems of high cost and poor cadmium pollution treatment effect of the soil remediation agent.

Description

Technical Field

[0001] The present invention relates to the technical field of soil treatment, and in particular to a soil repair agent and a preparation method and application thereof. Background Art

[0002] Heavy metal cadmium in cultivated soil can easily accumulate in organisms through crops, posing a huge threat to human health and the environment. Soil acidification is also one of the increasingly serious problems. Soil acidification is not only an important reason for the decline in soil fertility, but also an important factor restricting the sustainable development of agricultural production. Soil acidification can cause the activation of heavy metals such as aluminum, manganese, chromium, and cadmium, thereby affecting plant growth, such as aluminum poisoning and manganese poisoning. Moreover, after the activated heavy metals are absorbed and accumulated by crops, they endanger the health of humans and animals through the food chain. Therefore, many scholars are committed to developing efficient acid soil treatment technologies and heavy metal pollution control technologies.

[0003] Soil improvement is to take corresponding measures to improve soil properties and soil fertility in response to the poor texture and structure of the soil. Soil remediation agents are an important application of soil improvement. In recent years, applying remediation agents to acidic heavy metal contaminated soil to adsorb and fix pollution sources and reduce soil pollution is one of the effective means of remediating acidic heavy metal contaminated soil. Some remediation agents including calcium phosphate, phosphate rock, fly ash, etc. have been used as fixatives for heavy metals in contaminated soil. However, these remediation agents are costly and easily lead to secondary pollution. Biochar contains a large number of active organic functional groups and has great potential for the removal and passivation of pollutants such as heavy metals and organic matter in wastewater and soil. For example, patent CN117658098A discloses a method for treating cadmium using straw porous carbon material as an adsorbent, but the adsorbent repair capacity of this single carbon component is low; for example, patent CN102321484A discloses an organic and environmentally friendly soil conditioner for improving acidified or acidic soil. The soil conditioner produced by this invention can increase the pH value of the soil, increase the nutrients such as calcium, magnesium, phosphorus, and potassium in the soil, increase the organic matter content of the soil, improve the soil's ability to retain water and fertilizer, improve the physical and chemical properties of the soil, and reduce heavy metal toxicity. However, this soil conditioner has the defects of complex preparation process, high cost, and limited source of raw materials.

[0004] Therefore, to address the problems of heavy metal cadmium pollution and soil acidification in cultivated soil, lower-cost and more efficient remediation agents need to be developed urgently. Summary of the invention

[0005] The main purpose of the present invention is to provide a soil remediation agent and a preparation method and application thereof, aiming to solve the problems of high cost of soil remediation agents and poor effect on cadmium pollution control.

[0006] To achieve the above object, the present invention provides a method for preparing a soil remediation agent, comprising the following steps:

[0007] The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue, which is carbonized to obtain a soil repair agent.

[0008] The present invention provides a method for preparing a soil remediation agent, comprising the following steps:

[0009] The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue to obtain a solid.

[0010] The solid matter is mixed with ammonium salt and carbonized to obtain a soil remediation agent.

[0011] In one embodiment, the mass ratio of the solid matter to the ammonium salt is 1:(0.1-1).

[0012] In one embodiment, the ammonium salt includes at least one of ammonium phosphate, ammonium hydrogen phosphate and ammonium nitrate.

[0013] In one embodiment, the papermaking black liquor is prepared by a sulfite process.

[0014] In one embodiment, the alkaline solution containing calcium ions comprises a calcium hydroxide solution.

[0015] In one embodiment, the pH of the mixed solution is 8-10.

[0016] In one embodiment, the carbonization temperature is 300-800° C.; and / or,

[0017] The carbonization time is 1 to 10 hours.

[0018] The present invention provides a soil remediation agent, the soil remediation agent comprising a soil remediation agent prepared by the method for preparing a soil remediation agent according to any one of claims 1 to 5, wherein the specific surface area of ​​the soil remediation agent is 0.02 to 0.29 cm 3 / g.

[0019] The present invention provides an application of the soil remediation agent, wherein the soil remediation agent is used to adjust the pH of acidic soil.

[0020] The present invention provides an application of the soil remediation agent, wherein the soil remediation agent is used for passivating cadmium ions in soil.

[0021] In one embodiment, the application comprises the following steps:

[0022] Mix the soil with the soil remediation agent and treat it for 5 to 150 days.

[0023] In one embodiment, the mass ratio of the soil remediation agent to soil is (0.01-0.1):1.

[0024] In one embodiment, the step of mixing the soil with the soil remediation agent comprises: mixing the soil, the soil remediation agent and water;

[0025] Wherein, the mass ratio of soil to water is 10:(1-8).

[0026] The beneficial effects of the technical solution of the present invention are as follows:

[0027] (1) The preparation method provided by the present invention prepares a calcium-doped biochar soil remediation agent by calcifying and precipitating papermaking black liquor and carbonizing the same. The preparation method has low equipment requirements, simple process, low cost, and is suitable for large-scale production and application, thus solving the problems of complex processing process, high equipment requirements and high cost in the prior art of treating papermaking black liquor;

[0028] (2) The preparation method of the biochar repair agent of the present invention uses papermaking black liquor as the main raw material, which has the advantages of being easy to obtain, widely available, and low in price. The prepared calcium-doped biochar soil repair agent is used to prepare a soil repair agent and realize the repair of heavy metal-contaminated farmland. The pH value of acidic soil can be significantly increased by introducing a large amount of calcium elements; the synergistic effect of the introduced calcium and phosphorus elements can reduce the leaching concentration of heavy metal cadmium in the soil; in addition, the introduced calcium, phosphorus, nitrogen and other elements are not only harmless to the soil, but also can provide essential nutrients for the growth of crops. Therefore, the soil repair agent prepared by the present invention can solve the problem of papermaking waste disposal, and can also be used to solve the problems of soil acidification and soil heavy metal pollution, and provide the soil with essential nutrients for the growth of crops. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0031] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0032] With the rapid development of electroplating, metallurgy, chemical industry and other fields, cadmium pollution in cultivated soil is becoming increasingly serious. Heavy metal cadmium in cultivated soil can easily accumulate in organisms through crops, posing a huge threat to human health and the environment. Soil acidification is also one of the increasingly serious problems. Soil acidification is not only an important reason for the decline in soil fertility, but also an important factor restricting the sustainable development of agricultural production. Soil acidification can cause the activation of heavy metals such as aluminum, manganese, chromium, and cadmium, thereby affecting plant growth, such as aluminum poisoning and manganese poisoning. Moreover, after the activated heavy metals are absorbed and accumulated by crops, they endanger the health of humans and animals through the food chain. Therefore, many scholars are committed to developing efficient acid soil treatment technology and heavy metal pollution control technology.

[0033] Soil improvement and remediation agents are an important application of soil improvement. In recent years, applying remediation agents to acidic heavy metal contaminated soil to adsorb and fix pollution sources and reduce soil pollution is one of the effective means of remediating acidic heavy metal contaminated soil. Some remediation agents including calcium phosphate, phosphate rock, fly ash, etc. have been used as fixatives for heavy metals in contaminated soil. However, these remediation agents are costly and can easily cause secondary pollution. Therefore, in order to address the problems of heavy metal cadmium pollution and soil acidification in cultivated soil, more cost-effective and efficient remediation agents are urgently needed to be developed.

[0034] Papermaking black liquor is a high-concentration organic wastewater produced in the chemical pulping process. It mainly comes from the chemical recovery stage in pulp production. There are two main chemical pulping methods, alkaline pulping and sulfite pulping. The black liquor produced by ammonium sulfite pulping contains lignin, potassium, magnesium, calcium and other elements. The composite material formed after pyrolysis contains rich functional groups such as hydroxyl and carboxyl. At present, the black liquor produced by ammonium sulfite pulping is mainly used for the preparation of pickling corrosion inhibitors, the preparation of organic acids, and composting. Compared with alkaline papermaking black liquor, although acid papermaking black liquor also has certain applications, due to the complex process, large equipment investment, and the high ash content and impurities of the separated lignin, it is difficult to use, which greatly limits the application of sulfite pulping black liquor.

[0035] In view of this, the present invention proposes a method for preparing a soil remediation agent, comprising the following steps:

[0036] The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue, which is carbonized to obtain a soil repair agent.

[0037] The technical solution of the present invention uses black liquor waste in the sulfite pulping process as raw material, adds an alkaline solution containing calcium ions to adjust the pH, filters, and dries to obtain a solid product, and then carbonizes the solid product to prepare a calcium-doped biochar soil remediation agent. It should be noted that, in the preparation method of the present invention, papermaking black liquor is used as a raw material, and the prepared soil remediation agent combines the material advantages of papermaking black liquor, contains elements such as potassium, magnesium, calcium, and rich functional groups such as hydroxyl and carboxyl, which is beneficial to the fixation of heavy metal ions during soil remediation; adding an alkaline solution containing calcium ions to the papermaking black liquor can precipitate biomass such as lignin, hemicellulose and sugars in the papermaking black liquor, and the filter residue obtained after precipitation will be used as a raw material for subsequent carbonization to prepare the soil remediation agent. In addition, calcium ions are introduced to supplement the cations in the acidified soil, which is beneficial to repair soil acidification, increase the adsorption of cadmium ions, and can also help to supplement the soil with nutrients necessary for plant growth; the biomass filter residue obtained after precipitation is subjected to high-temperature carbonization to obtain a calcium-doped carbon material, that is, a calcium-doped soil remediation agent, which has low cost and its components are harmless to the soil.

[0038] The preparation method of the present invention has low equipment requirements, simple process, low cost, and is suitable for large-scale production and application. In addition, the prepared soil remediation agent has a good adsorption effect on heavy metal cadmium. The soil remediation agent is used to treat acidic soil or cadmium-contaminated soil. After a period of time, the pH of the acidic soil can be increased, and the leaching concentration of heavy metal cadmium in the soil can be reduced. The introduced calcium element can provide essential nutrients for the growth of crops. Therefore, the technical solution of the present invention can achieve the repair of acidic soil or heavy metal-contaminated soil, and solve the problems of high preparation cost and poor effect of cadmium pollution control of existing soil remediation agents. In addition, the technical solution of the present invention uses papermaking black liquor as raw material, which is convenient, easy to obtain, widely available and inexpensive. It can not only solve the problem of papermaking waste disposal, but also solve the problems of complex processing technology, high equipment requirements and high cost in the treatment of papermaking black liquor in the prior art.

[0039] The present invention also provides a method for preparing a soil remediation agent, comprising the following steps:

[0040] The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue to obtain a solid.

[0041] The solid matter is mixed with ammonium salt and carbonized to obtain a soil repair agent.

[0042] An alkaline solution containing calcium ions is added to the papermaking black liquor to calcify and precipitate the biomass in the papermaking black liquor. Subsequently, the solid obtained after the calcification precipitation and the ammonium salt are co-carbonized at high temperature, which is conducive to the preparation of a porous biochar soil remediation agent. It should be noted that the introduction of ammonium salt and solid co-carbonization, on the one hand, the ammonium salt pyrolyzes at high temperature to produce gas, which has a certain pore-forming effect on the soil remediation agent, is conducive to the preparation of a porous soil remediation agent, and increases the specific surface area of ​​the soil remediation agent, thereby improving the adsorption effect of the soil remediation agent on heavy metal ions; on the other hand, some non-metallic elements in the ammonium salt are conducive to the formation of a multi-element doped soil remediation agent, which provides the necessary nutrients for the growth of crops and can improve the adsorption effect of heavy metal ions. Compared with the soil remediation agent prepared without adding ammonium salt, the soil remediation agent prepared by the method of introducing ammonium salt and solid co-carbonization can increase the pore volume of the soil remediation agent, and when treating acidic cadmium contaminated soil, the effect of increasing the pH of the acidic soil is better, and the effect of reducing the leaching content of heavy metal cadmium in the soil is also better.

[0043] The preparation method provided by the technical solution of the present invention realizes a porous soil remediation agent by co-carbonizing biomass and ammonium salt. No additional porous raw materials need to be added to prepare the porous soil remediation agent. The preparation process is simple, the preparation cost is low, and it is suitable for large-scale production applications.

[0044] In an embodiment of the present invention, the carbonization is performed under an inert atmosphere, and the inert atmosphere may be one or more of N2, He and Ar.

[0045] In an embodiment of the present invention, the mass ratio of the solid matter to the ammonium salt is 1:(0.1-1). Setting the mass ratio of the solid matter to the ammonium salt within this range ensures that the prepared soil remediation agent has a good soil remediation effect while controlling the production cost.

[0046] In an embodiment of the present invention, the ammonium salt includes at least one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium nitrate. The ammonium salt includes at least one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium nitrate, which means that the ammonium salt can be any one of ammonium phosphate, ammonium hydrogen phosphate, and ammonium nitrate, or two or more of ammonium phosphate, ammonium hydrogen phosphate, and ammonium nitrate. When the ammonium salt is ammonium phosphate or ammonium hydrogen phosphate, a porous structure of phosphorus, calcium, and nitrogen co-doped biochar soil remediation agent can be obtained; when the ammonium salt is ammonium nitrate, a porous structure of nitrogen and calcium co-doped biochar soil remediation agent can be obtained.

[0047] In an embodiment of the present invention, the papermaking black liquor is prepared by a sulfite method. Papermaking black liquor contains a large amount of lignin and elements such as potassium, magnesium, and calcium. The composite material formed after pyrolysis contains abundant functional groups such as hydroxyl and carboxyl, and compounds containing elements such as calcium and magnesium can also interact with heavy metal cations to form mononuclear or binuclear complexes, so that the composite material has the structural and material conditions to be used as a heavy metal ion fixing material. The technical solution of the present invention selects conventional papermaking black liquor to prepare soil remediation agent, and does not limit the specific components of papermaking black liquor.

[0048] In an embodiment of the present invention, the alkaline solution containing calcium ions includes a calcium hydroxide solution. Calcium is one of the essential elements for plant growth and plays an important role in the growth and development of plants. By introducing calcium ions, not only can the pH value of the soil be increased, but also the necessary calcium nutrition can be provided to plants, thereby promoting the healthy growth of plants.

[0049] In an embodiment of the present invention, the pH of the mixed solution is 8 to 10. By controlling the amount of alkaline solution containing calcium ions added to make the pH of the mixed solution 8 to 10, the pH of the mixed solution is set within this range, so that the papermaking black liquor can be fully precipitated and solidified, and the introduced calcium content can be controlled within a suitable range.

[0050] In an embodiment of the present invention, the carbonization temperature is 300-800°C; the carbonization time is 1-10h. At a lower carbonization temperature, the biomass material is not completely pyrolyzed, the formed biochar material has a small specific surface area, and the pore structure is not well developed, resulting in a weakened adsorption capacity of the material and limited fixation effect on heavy metal ions; at a higher carbonization temperature, the structure of the biochar material is more stable, but too high a temperature may cause the pore structure of the biochar material to shrink and partially close, resulting in a decrease in specific surface area, and too high a temperature may also reduce the functional groups on the surface of the biochar, thereby affecting the adsorption performance. Setting the carbonization temperature and carbonization time in the above range is conducive to obtaining a biochar soil remediation agent with good stability and good adsorption effect. Preferably, the carbonization temperature is 300-600°C; the carbonization time is 2-5h.

[0051] The present invention provides a soil remediation agent, the soil remediation agent includes a soil remediation agent prepared according to the preparation method of the soil remediation agent, and the specific surface area of ​​the soil remediation agent is 0.02 to 0.29 cm 3 / g. The soil remediation agent provided by the technical solution of the present invention has a certain porous structure, which can enhance the lattice fixation effect of the soil remediation agent on heavy metal ions and is beneficial to reducing the cadmium concentration in the soil.

[0052] The present invention provides an application of the soil remediation agent, which is used to adjust the pH of acidic soil. Calcium can increase the cation exchange capacity of the soil and replace the hydrogen ions (H + ) and aluminum ions (Al 3+ ), these ions are usually the main cause of soil acidification. And calcium ions can neutralize the acidic substances in the soil to produce neutral compounds, thereby increasing the pH value of the soil.

[0053] The present invention proposes an application of the soil remediation agent, which is used to passivate cadmium ions in the soil. The passivation process can reduce the activity of heavy metal ions and stabilize the heavy metal structure, making the heavy metal ions more stable, reducing the toxicity of heavy metal ions to the environment, and promoting the migration and stability of heavy metals in the soil. Using the soil remediation agent provided by the present invention to treat cadmium-contaminated soil can significantly reduce the leaching concentration of heavy metal cadmium, and can be used for the treatment and restoration of cadmium-contaminated land.

[0054] In an embodiment of the present invention, the application comprises the following steps:

[0055] Mix the soil with the soil remediation agent and treat it for 5 to 150 days.

[0056] In an embodiment of the present invention, the mass ratio of the soil remediation agent to the soil is (0.01-0.1):1. It should be noted that the introduction of calcium can significantly reduce the pH value of acidic soil, and the synergistic effect of calcium and phosphorus can significantly increase the efficiency of fixing and repairing heavy metal cadmium. Therefore, the amount of the remediation agent applied in the present invention is lower than that of the conventional remediation agent, and the required repair time is shorter. In addition, after applying the remediation agent described in the present invention, the nutrient content in the soil can also be increased, which is beneficial to the growth of crops.

[0057] In an embodiment of the present invention, the step of mixing the soil with the soil remediation agent comprises: mixing the soil, the soil remediation agent and water;

[0058] The mass ratio of soil to water is 10:(1-8). When performing soil remediation, an appropriate amount of water and soil remediation agent is added to the soil to make the soil moisture content reach the range of 10% to 80%, thereby ensuring the effective diffusion and reaction of the remediation agent, high remediation efficiency and good remediation effect.

[0059] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention, and are not used to limit the present invention.

[0060] In the following examples, the papermaking black liquor is from a paper mill in Xiangyang City, Hubei Province;

[0061] The uncontaminated soil comes from 10 to 20 cm above the surface of a farmland in Pengjiazhuang Village, Miaotan Town, Gucheng County, Hubei Province.

[0062] Example 1

[0063] A method for preparing a soil remediation agent comprises the following steps:

[0064] (1) adding calcium hydroxide to the papermaking black liquor to adjust the pH to 8, stirring for 2 hours and then centrifuging to obtain a solid product, and drying the solid product for later use;

[0065] (2) 100 g of the dry solid product was placed in a porcelain boat, placed in a tube furnace, heated to 500 °C under N2 protection and carbonized for 1 h to obtain a non-porous calcium-doped soil remediation agent.

[0066] Example 2

[0067] A method for preparing a soil remediation agent comprises the following steps:

[0068] (1) adding calcium hydroxide to the papermaking black liquor to adjust the pH to 10, stirring for 5 hours and then centrifuging to obtain a solid product, and drying the solid product for later use;

[0069] (2) 100 g of the dry solid product was mixed with 1 g of ammonium phosphate, then placed in a porcelain boat, placed in a tube furnace, heated to 600 °C under He protection and carbonized for 2 h to obtain a porous phosphorus, calcium and nitrogen doped soil remediation agent.

[0070] Example 3

[0071] A method for preparing a soil remediation agent comprises the following steps:

[0072] (1) adding calcium hydroxide to the papermaking black liquor to adjust the pH to 9, stirring for 5 hours and then centrifuging to obtain a solid product, and drying the solid product for later use;

[0073] (2) 100 g of the dry solid product was mixed with 10 g of ammonium hydrogen phosphate, then placed in a porcelain boat, placed in a tube furnace, heated to 400 °C under Ar protection and carbonized for 5 h to obtain a porous phosphorus, calcium and nitrogen doped soil remediation agent.

[0074] Example 4

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

[0076] (1) adding calcium hydroxide to the papermaking black liquor to adjust the pH to 10, stirring for 2 hours and then centrifuging to obtain a solid product, and drying the solid product for later use;

[0077] (2) 100 g of the dry solid product, 2 g of ammonium phosphate and 2 g of ammonium hydrogen phosphate were mixed, then placed in a porcelain boat, placed in a tube furnace, heated to 400 °C under N2 protection and carbonized for 5 h to obtain a porous phosphorus, calcium and nitrogen doped soil remediation agent.

[0078] Example 5

[0079] A method for preparing a soil remediation agent comprises the following steps:

[0080] (1) adding calcium hydroxide to the papermaking black liquor to adjust the pH to 10, stirring for 2 hours and then centrifuging to obtain a solid product, and drying the solid product for later use;

[0081] (2) 100 g of the dry solid product was mixed with 5 g of ammonium nitrate, and then placed in a porcelain boat, placed in a tube furnace, heated to 300 °C under N2 protection and carbonized for 5 h to obtain a porous nitrogen and calcium doped soil remediation agent.

[0082] Example 6

[0083] An application of a soil remediation agent comprises the following steps:

[0084] (1) Preparation of acidic cadmium-contaminated soil: Weigh 1 kg of uncontaminated soil sample with a pH of 5.8, then add 20 mg of cadmium to the soil sample, add water to the soil (at a liquid-to-solid ratio of 1:1 mL / mg), stir evenly, age for 30 days, and then air-dry naturally to obtain an acidic cadmium-contaminated soil sample;

[0085] (2) Adding the soil remediation agent of Example 1 to the cadmium-contaminated soil for passivation treatment for 5 days; wherein the mass ratio of the remediation agent to the soil is 0.01:1.

[0086] Example 7

[0087] An application of a soil remediation agent comprises the following steps:

[0088] The soil remediation agent of Example 2 was added to the acidic cadmium-contaminated soil for passivation treatment for 20 days; wherein the mass ratio of the remediation agent to the soil was 0.03:1.

[0089] Example 8

[0090] An application of a soil remediation agent comprises the following steps:

[0091] The soil remediation agent of Example 3 was added to the acidic cadmium-contaminated soil for passivation treatment for 150 days; wherein the mass ratio of the remediation agent to the soil was 0.05:1.

[0092] Example 9

[0093] An application of a soil remediation agent comprises the following steps:

[0094] The soil remediation agent of Example 4 was added to the acidic cadmium-contaminated soil for passivation treatment for 90 days; wherein the mass ratio of the remediation agent to the soil was 0.1:1.

[0095] Example 10

[0096] An application of a soil remediation agent comprises the following steps:

[0097] The soil remediation agent of Example 5 was added to the acidic cadmium-contaminated soil for passivation treatment for 90 days; wherein the mass ratio of the remediation agent to the soil was 0.1:1.

[0098] Performance Testing

[0099] The soil pH value and cadmium leaching concentration of the acidic cadmium-contaminated soil treated with the soil remediation agent in Examples 6-10 were measured. The test results are shown in Table 1.

[0100] Table 1 Test of the repair effect of the soil repair agent of Examples 6-10

[0101]

[0102] As shown in Table 1, the use of the soil remediation agents of Examples 6-10 to treat cadmium-contaminated soil can increase the pH value of acidic soil and reduce the leaching concentration of heavy metal cadmium in the soil, and the leaching concentration of heavy metal cadmium in the soil can be reduced by up to 75%;

[0103] It can also be seen from Table 1 that the pore volume of the soil remediation agents of Examples 7-10 is greater than that of Example 6, the effect of increasing soil pH is better than that of Example 6, and the effect of reducing the heavy metal cadmium content in the soil is also better than that of Example 6, indicating that the soil remediation agent prepared by introducing ammonium salts has a better soil treatment effect than the soil remediation agent prepared without adding ammonium salts, and the introduction of ammonium salts is conducive to the preparation of a soil remediation agent with a porous structure.

[0104] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the technical concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a soil remediation agent, characterized in that: The following steps are involved: The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue, which is carbonized to obtain a soil repair agent.

2. A method for preparing a soil remediation agent, characterized in that: The following steps are involved: The papermaking black liquor and the alkaline solution containing calcium ions are mixed to obtain a mixed solution, and the mixed solution is filtered to obtain a filter residue to obtain a solid. The solid matter is mixed with ammonium salt and carbonized to obtain a soil repair agent.

3. The method for preparing the soil remediation agent according to claim 2, characterized in that: The mass ratio of the solid matter to the ammonium salt is 1:(0.1-1); and / or, The ammonium salt includes at least one of ammonium phosphate, ammonium hydrogen phosphate and ammonium nitrate.

4. The method for preparing the soil remediation agent according to claim 1 or 2, characterized in that: The papermaking black liquor is prepared by a sulfite process; and / or, The alkaline solution containing calcium ions comprises a calcium hydroxide solution; and / or, The pH of the mixed solution is 8-10.

5. The method for preparing the soil remediation agent according to claim 1 or 2, characterized in that: The carbonization temperature is 300-800° C.; and / or, The carbonization time is 1 to 10 hours.

6. A soil remediation agent, characterized in that: The soil remediation agent comprises a soil remediation agent prepared by the method for preparing a soil remediation agent according to any one of claims 1 to 5, wherein the specific surface area of ​​the soil remediation agent is 0.02 to 0.29 cm 3 / g.

7. Use of the soil remediation agent according to claim 6, characterized in that: The soil remediation agent is used for adjusting the pH of acidic soil.

8. An application of the soil remediation agent as claimed in claim 6, characterized in that: The soil remediation agent is used for passivating cadmium ions in the soil.

9. The use according to claim 7 or 8, characterized in that The application comprises the following steps: Mix the soil with the soil remediation agent and treat it for 5 to 150 days.

10. The use according to claim 9, characterized in that The mass ratio of the soil remediation agent to the soil is (0.01-0.1):1; and / or, The step of mixing the soil with the soil remediation agent comprises: mixing the soil, the soil remediation agent and water; Wherein, the mass ratio of soil to water is 10:(1-8).

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