A soil conditioner and method for improving soil health

Abstract

The application provides a soil conditioner and a soil health improvement method, and steps include: mixing activated illite and dry cow dung, adding an activation solution to the mixture according to a solid-liquid ratio of 1:5-1:20, first ultrasonic oscillation, then mixing for secondary activation, then washing with a large amount of water until pH is constant, drying to obtain a dried mixture; compounding the dried mixture with calcium oxide to obtain the soil conditioner. The application uses natural minerals and waste biomass-based raw materials to develop a non-iron-based, green and sustainable remediation material, which can realize the synergistic stabilization of Cd and As composite pollution in a karst area in southwest China, and can also realize the improvement of soil health indexes such as microbial diversity, soil TOC, CEC, available P and available K; the application can not only solve the technical problem of difficult simultaneous stabilization of Cd and As, but also avoid the influence of the stabilized material on soil health.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil remediation and environmental functional materials, and particularly relates to a soil conditioner and a soil health improvement method. BACKGROUND

[0002] Healthy soil is the basis for achieving sustainable development, but soil degradation is caused by soil pollution, nutrient loss, and reduced biodiversity, among other reasons. Heavy metal pollution is an important problem causing soil degradation.

[0003] For farmland soil, the most prominent element exceeding the standard is cadmium (Cd), in addition, it is usually accompanied by pollution of elements such as arsenic (As). The karst region in southwest China is the main rice production area, and the high geological background causes Cd and As co-contamination in paddy soil. In the soil environment, Cd is a positively charged cation, while As is a negatively charged oxygen-containing acid anion, and the geochemical behavior of the two is antagonistic, making it difficult to co-treat. Stabilization is a common remediation measure for treating heavy metal pollution in paddy soil, which reduces the mobility of heavy metal elements in soil by adding exogenous remediation agents.

[0004] The existing patent CN202110905728.9 relates to a method for repairing cadmium-arsenic contaminated soil, comprising the following steps: step one, adding sodium percarbonate to the cadmium-arsenic contaminated soil, stirring uniformly, and then standing for 2-4 hours to obtain the oxidized cadmium-arsenic contaminated soil, wherein the addition amount of sodium percarbonate is 0.5-3wt% of the soil mass; step two, adding hematite powder and calcium-based compound to the oxidized cadmium-arsenic contaminated soil, stirring uniformly, and then stabilizing for 3-7 days, wherein the addition amount of hematite powder is 0.5-5wt% of the soil mass, and the addition amount of calcium-based compound is 0.5-2.5wt% of the soil mass; step three, after the soil is stabilized for 3-7 days in step two, 3-mercapto propyl methoxy silane is sprayed onto the surface of the soil, then stirred uniformly, and then stabilized for 5-10 days. This repair method can oxidize and stabilize heavy metal cadmium-arsenic contaminated soil with different pollution levels, has good repair effect, and the repair method is simple.

[0005] Existing patent CN202211485088.1 discloses a heavy metal passivating agent, soil remediation material, and a method for remediating cadmium and arsenic compound pollutants. The heavy metal passivating agent includes iron salts, manganese compounds, and zinc salts. A Fe-Mn-Zn ternary complex is synthesized via a secondary co-precipitation method. After washing and drying, a passivating material is obtained for synergistic remediation of cadmium and arsenic pollution in soil. The disclosed remediation material, through adsorption, oxidation-adsorption, reduction, ion exchange, and surface complexation, induces cadmium and arsenic to form stable chemical forms, reducing their migration in soil and their diffusion capacity in the environment, thus mitigating the ecological risks of heavy metals and further reducing their harmful effects on human health. It also effectively removes cadmium and arsenic ions from water bodies. This remediation material has a simple preparation process, short production cycle, is easy to store, convenient to use, and environmentally friendly, and can be widely applied to the remediation of cadmium and arsenic compound pollution in the environment.

[0006] Currently, agents used for the remediation of Cd and As combined pollution are mainly iron-based materials. However, a large dosage of iron-based materials is often required to achieve a satisfactory stabilization effect (stabilization rate greater than 50%), which may pose a certain threat to soil health after addition. Therefore, this invention provides a soil conditioner and a method for improving soil health. Summary of the Invention

[0007] The purpose of this invention is to provide a soil conditioner and a method for improving soil health. Using natural minerals and waste biomass-based raw materials, a non-iron-based, green and sustainable remediation material has been developed, which can achieve synergistic stabilization of Cd and As compound pollution in the karst areas of Southwest China. At the same time, it can also improve soil health indicators such as microbial diversity, soil TOC, CEC, available P, and available K. It can solve the technical problem of simultaneous stabilization of Cd and As, and avoid the impact of stabilization materials on soil health.

[0008] On the one hand, the present invention provides a soil conditioner, the steps of which include: mixing activated Yimeng soil and dried cow manure, adding an activation solution to the mixture at a solid-liquid ratio of 1g:(5-20)mL, first ultrasonically vibrating, then mixing for secondary activation, filtering and rinsing with a large amount of water until the pH is constant, and drying to obtain a dried mixture; and compounding the dried mixture with calcium oxide to obtain a soil conditioner.

[0009] Furthermore, the preparation method of the activated imidacloprid includes adding imidacloprid to an activation solution at a solid-liquid ratio of 1g:(5-20)mL, mixing at 60-80℃ for 1-2h, filtering, rinsing with a large amount of water until the pH is constant, and then drying to obtain the product.

[0010] Furthermore, the dried cow dung is obtained by drying fresh cow dung at 40-60℃ for 48-72 hours.

[0011] Further, the mixing needs to be stirred, and the stirring speed is 200-300 rpm.

[0012] Further, the drying is drying at 40-60 DEG C for 48-72 h.

[0013] Further, the size of the illite is 80-120 mesh.

[0014] Further, the mass ratio of the activated illite and dry cow dung is 1:1-1:1.5.

[0015] Further, the ultrasonic oscillation time is 15-30 min.

[0016] Further, the secondary activation time is 4-6 h.

[0017] Further, the mass ratio of the dried mixture and calcium oxide is 2:1-2.5:1.

[0018] Further, the activation solution contains 1-3 M citric acid and 1-3 M glacial acetic acid.

[0019] In another aspect, the application also provides a soil conditioner prepared by the aforementioned method.

[0020] In another aspect, the soil conditioner and the preparation method thereof in the application are applied to soil remediation.

[0021] In another aspect, the application also provides a soil health improvement method, and the steps include: adding the soil conditioner prepared by the preparation method 3-7 days before rice transplanting, the adding dosage is 2-10 t / ha, and the mixing depth is 0-20 cm. The mixing depth represents the depth of mixing the soil conditioner with the soil.

[0022] The application has the following beneficial effects:

[0023] The application realizes the three goals of Cd stabilization, As stabilization and soil health improvement in paddy soil by non-iron-based materials; the soil health improvement method in the application can increase the microbial diversity, increase the soil TOC, increase the soil CEC, increase the soil available P and increase the soil available K;

[0024] The mineral used in the application is illite instead of other clay minerals, because illite is a widely distributed hydrophilic layered natural clay mineral, is a transition product produced in the natural conversion process from montmorillonite to illite, is an intercalated mixed mineral of illite and montmorillonite, has the properties of montmorillonite and illite, has more complex pore structure, better extension and swelling performance, is more conducive to the adsorption of heavy metals and the fixation of nutrients, and can realize the stabilization of heavy metals while avoiding the loss of available nutrients;

[0025] The activation solution in the application is composed of weak acid, meets the concept of green chemistry, and aims to realize hole expansion, uniformly mix materials, increase oxygen-containing functional groups on the surface of materials, and be conducive to the synergistic stabilization of As and Cd; the alkalinity of the material is reduced to avoid the activation of As after the material is added; the material mixture after activation is acidic, at this time, the addition of calcium oxide is not to create an alkaline environment of the soil, but to adjust the pH of the material to neutral to avoid great disturbance to the soil pH, and avoiding great disturbance to the soil pH is the key to guaranteeing soil microbial diversity;

[0026] The soil conditioner prepared in the application is rich in oxygen-containing functional groups, and realizes the synergistic stabilization of As and Cd through surface complexation; at the same time, the soil conditioner developed in the application does not cause great disturbance to the soil pH and Eh, is conducive to long-term stabilization; the low molecular weight organic acid adsorbed in the pores of illite is conducive to the activity of microorganisms, so that the soil pH and Eh do not change significantly, thereby realizing the increase of soil microbial diversity;

[0027] The soil conditioner prepared in the application is rich in oxygen-containing functional groups, and realizes the synergistic stabilization of As and Cd through surface complexation; at the same time, the soil conditioner developed in the application does not cause great disturbance to the soil pH and Eh, is conducive to long-term stabilization; the low molecular weight organic acid adsorbed in the pores of illite is conducive to the activity of microorganisms, so that the soil pH and Eh do not change significantly, thereby realizing the increase of soil microbial diversity; DETAILED DESCRIPTION

[0028] The technical solutions of the application will be described below clearly and completely. Obviously, the described embodiments are part of the embodiments of the application, instead of all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0029] Embodiment 1

[0030] The embodiment provides a soil conditioner, and the preparation steps include:

[0031] (1) Illite activation: illite (purity 98.0%) was added to the activation solution according to the solid-liquid ratio of 1 g: 10 mL, mixed and stirred at 60°C for 1 h, the stirring speed was 250 rpm, after filtration, washed with a large amount of water until pH constant, and dried at a temperature of 50°C for 60 h;

[0032] wherein the composition of the activation solution is: 1 M citric acid and 1 M glacial acetic acid;

[0033] (2) Preparation of soil conditioner: the activated illite was mixed with dry cow dung according to the mass ratio of 3:4, the above-activated solution was added to the mixture according to the solid-liquid ratio of 1 g: 10 mL, ultrasonic oscillation was performed for 15 min first, then mixed for 4 h, secondary activation was performed, after filtration, washed with a large amount of water until pH constant, and then dried at a temperature of 50°C for 60 h; the dried mixture and calcium oxide were compounded according to the mass ratio of 7:3 to obtain the soil conditioner.

[0034] wherein the dry cow dung is fresh cow dung dried at 50°C for 60 h.

[0035] The soil health improvement method in this example includes: 2 t / ha of the material is added 3 days before transplanting, and the material and the soil with a depth of 20 cm are fully mixed.

[0036] Example 2

[0037] On the basis of Example 1, the material dosage is adjusted to 5 t / ha, and the other steps and conditions are consistent with Example 1.

[0038] Example 3

[0039] On the basis of Example 1, the material dosage is adjusted to 10 t / ha, and the other steps and conditions are consistent with Example 1.

[0040] Example 4

[0041] On the basis of Example 1, the citric acid is adjusted to 3 M, the glacial acetic acid is adjusted to 1 M, and the other steps and conditions are consistent with Example 1.

[0042] Example 5

[0043] On the basis of Example 1, the citric acid is adjusted to 1 M, the glacial acetic acid is adjusted to 3 M, and the other steps and conditions are consistent with Example 1.

[0044] Example 6

[0045] On the basis of Example 1, the citric acid is adjusted to 3 M, the glacial acetic acid is adjusted to 3 M, and the other steps and conditions are consistent with Example 1.

[0046] Comparative Example 1

[0047] On the basis of example 1, the material dosage is adjusted to 1 t / ha, and other steps and conditions are consistent with example 1.

[0048] Comparative example 2

[0049] On the basis of example 1, the material dosage is adjusted to 12 t / ha, and other steps and conditions are consistent with example 1.

[0050] Comparative example 3

[0051] On the basis of example 1, only 3 M citric acid is added without glacial acetic acid, and other steps and conditions are consistent with example 1.

[0052] Comparative example 4

[0053] On the basis of example 1, only 3 M glacial acetic acid is added without citric acid, and other steps and conditions are consistent with example 1.

[0054] Comparative example 5

[0055] On the basis of example 1, the activation step is omitted, and the three raw materials are simply mixed, and other steps and conditions are consistent with example 1.

[0056] Comparative example 6

[0057] On the basis of example 1, the citric acid is adjusted to 3 M, and the glacial acetic acid is adjusted to 4 M, and other steps and conditions are consistent with example 1.

[0058] Comparative example 7

[0059] On the basis of example 1, the citric acid is adjusted to 4 M, and the glacial acetic acid is adjusted to 3 M, and other steps and conditions are consistent with example 1.

[0060] Comparative example 8

[0061] On the basis of example 1, no calcium oxide is added, and other steps and conditions are consistent with example 1.

[0062] Comparative example 9

[0063] On the basis of example 1, the mass ratio of the mixture after drying and calcium oxide is adjusted to 1.5:1, and other steps and conditions are consistent with example 1.

[0064] Comparative example 10

[0065] On the basis of example 1, the mass ratio of the mixture after drying and calcium oxide is adjusted to calcium oxide 3:1, and other steps and conditions are consistent with example 1.

[0066] Comparative example 11

[0067] On the basis of Example 1, the mass ratio of activated illite and dry cow dung after activation was adjusted to 1:0.8, and other steps and conditions were consistent with Example 1.

[0068] Comparative Example 12

[0069] On the basis of Example 1, the mass ratio of activated illite and dry cow dung after activation was adjusted to 1:2, and other steps and conditions were consistent with Example 1.

[0070] Comparative Example 13

[0071] On the basis of Example 1, illite was replaced by kaolinite (kaolin, purity 98.8%), and other steps and conditions were consistent with Example 1.

[0072] Comparative Example 14

[0073] On the basis of Example 1, illite was replaced by illite (purity 98.2%), and other steps and conditions were consistent with Example 1.

[0074] Comparative Example 15

[0075] On the basis of Example 1, illite was replaced by montmorillonite (montmorillonite, purity 99.5%), and other steps and conditions were consistent with Example 1.

[0076] Comparative Example 16

[0077] On the basis of Example 1, illite was replaced by sepiolite (purity 98.5%), and other steps and conditions were consistent with Example 1.

[0078] Comparative Example 17

[0079] On the basis of Example 1, illite was replaced by palygorskite (attapulgite) (purity 97.5%), and other steps and conditions were consistent with Example 1.

[0080] Comparative Example 18

[0081] On the basis of Example 1, the mixing time of the first activation was adjusted to 0.5 h, and other steps and conditions were consistent with Example 1.

[0082] Comparative Example 19

[0083] On the basis of Example 1, the mixing time of the first activation was adjusted to 3 h, and other steps and conditions were consistent with Example 1.

[0084] Comparative Example 20

[0085] On the basis of Example 1, the mixing time of the second activation was adjusted to 3 h, and other steps and conditions were consistent with Example 1.

[0086] Comparative Example 21

[0087] Based on the embodiment 1, the secondary activation mixing time is adjusted to 7 h, and other steps and conditions are consistent with those of the embodiment 1.

[0088] Test example: The soil conditioners prepared in the embodiments 1-6 and the comparative examples 1-21 are evaluated for performance as follows:

[0089] For a paddy field in a karst area in the southwest region, the soil conditioner material is added 3 days before transplanting. At the mature stage of the rice, the soil available heavy metals are characterized using deionized water extraction method, the content of the soil available heavy metals is analyzed by ICP-MS to obtain the stabilization rate (more than 50% is appropriate); the soil microbial diversity is characterized by the Shannon index through 16s rRNA analysis after the material is added (the larger the better), and then the soil TOC, CEC, available P and available K contents are measured. The results are shown in the following table:

[0090]

[0091] According to the above table, the following analysis is made for the comparative examples that fail to achieve the purpose: in the comparative example 1, the material addition amount is insufficient; in the comparative example 2, the material is excessively added, and the microbial diversity decreases; in the comparative examples 3 and 4, the material activation degree is insufficient; in the comparative example 5, the material is not activated; in the comparative examples 6 and 7, too much acid is introduced, which inhibits the soil microbial activity; in the comparative examples 8 and 10, the acid is not effectively neutralized, which inhibits the soil microbial activity and causes Cd activation; in the comparative example 9, too much alkali is introduced, which causes As activation and inhibits the microbial activity; in the comparative example 11, the organic matter proportion is low, and the soil health activation effect is not obvious; in the comparative example 12, the organic matter proportion is too high, and the heavy metal colloidal activation occurs; in the comparative examples 13-17, the stability effect is poor due to the replacement of the minerals; in the comparative examples 18 and 20, the activation time is insufficient; in the comparative example 19, the activation time is too long, which causes partial pore collapse, and the effect becomes worse; in the comparative example 21, the activation time is too long, which causes partial pore excessive filling and blockage, and the effect becomes worse.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the present application and not to limit the technical solutions described in the present application; those skilled in the art should understand that the present application can still be modified or replaced equivalently; and all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered in the claim scope of the present application.

Claims

1. A method of preparing a soil conditioner, characterized by the steps of The preparation method of the soil conditioner comprises the following steps: Preparation method of activated illite: the illite is added into an activation solution according to a solid-liquid ratio of 1 g: (5-20) mL, mixed at 60-80 DEG C for 1-2 h, washed with a large amount of water until the pH is constant, and then dried to obtain the activated illite; the activation solution comprises 1-3 M citric acid and 1-3 M glacial acetic acid; The activated illite and dry cow dung are mixed, the activation solution is added into the mixture according to a solid-liquid ratio of 1 g: (5-20) mL, ultrasonic oscillation is performed, secondary activation is performed by mixing, the mixture is washed with a large amount of water until the pH is constant, and then dried to obtain the mixture; the dried mixture and calcium oxide are compounded to obtain the soil conditioner; The mass ratio of the activated illite and the dry cow dung is 1:1-1:1.5; the secondary activation time is 4-6 h; and the mass ratio of the dried mixture and the calcium oxide is 2:1-2.5:

1.

2. A method of preparing a soil conditioner as claimed in claim 1, wherein, The ultrasonic oscillation time is 15-30 min.

3. A soil conditioner, characterized in that, The soil conditioner is prepared by using the preparation method of any one of claims 1-2.

4. The application of the preparation method of the soil conditioner in claim 3 in soil remediation.

5. A method of improving soil health, characterized by the steps of The soil conditioner prepared by using the preparation method of any one of claims 1-2 is added 3-7 days before rice seedling transplanting, the addition amount is 2-10 t / ha, and the mixing depth is 0-20 cm. The preparation method of the soil conditioner comprises the following steps: Preparation method of activated illite: the illite is added into an activation solution according to a solid-liquid ratio of 1 g: (5-20) mL, mixed at 60-80 DEG C for 1-2 h, washed with a large amount of water until the pH is constant, and then dried to obtain the activated illite; the activation solution comprises 1-3 M citric acid and 1-3 M glacial acetic acid; The activated illite and dry cow dung are mixed, the activation solution is added into the mixture according to a solid-liquid ratio of 1 g: (5-20) mL, ultrasonic oscillation is performed, secondary activation is performed by mixing, the mixture is washed with a large amount of water until the pH is constant, and then dried to obtain the mixture; the dried mixture and calcium oxide are compounded to obtain the soil conditioner; The mass ratio of the activated illite and the dry cow dung is 1:1-1:1.5; the secondary activation time is 4-6 h; and the mass ratio of the dried mixture and the calcium oxide is 2:1-2.5:

1. The ultrasonic oscillation time is 15-30 min. The soil conditioner is prepared by using the preparation method of any one of claims 1-2.

4. The application of the preparation method of the soil conditioner in claim 3 in soil remediation. The soil conditioner prepared by using the preparation method of any one of claims 1-2 is added 3-7 days before rice seedling transplanting, the addition amount is 2-10 t / ha, and the mixing depth is 0-20 cm.

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