Soil conditioner and soil health improving method

Abstract

The invention provides a soil conditioner and a soil health improving method. The method comprises the following steps: mixing activated illite-montmorillonite soil and dry cow dung, adding an activation solution into the mixture according to a solid-to-liquid ratio of 1: 5-1: 20, carrying out ultrasonic oscillation, mixing, carrying out secondary activation, washing with a large amount of water until the pH value is constant, and drying to obtain a dried mixture; and compounding the dried mixture with calcium oxide to obtain the soil conditioner. Natural minerals and waste biomass-based raw materials are adopted, a non-iron-based, green and sustainable repairing material is developed, synergistic stabilization of Cd and As combined pollution in the southwest karst area can be achieved, and meanwhile, improvement of soil health indexes such as microbial diversity, soil TOC, soil CEC, effective P and effective K can be achieved; the technical problem that Cd and As are difficult to stabilize synchronously can be solved, and the influence of a stabilizing material on soil health can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of soil remediation and environmental functional materials, and in particular to a soil conditioner and a method for improving soil health. Background Art

[0002] Healthy soil is the foundation for sustainable development, but agricultural soil is threatened by soil pollution, nutrient loss, biodiversity reduction, etc. Among them, heavy metal pollution is a major problem causing soil degradation.

[0003] The current situation of heavy metal pollution in soil is severe, showing the characteristics of complex causes, concentrated and continuous distribution, and coexistence of complex pollution. For agricultural 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 area is the main rice producing area. The high geological background causes the widespread existence of Cd and As complex pollution in paddy soil. In the soil environment, Cd is a positively charged cation, while As is a negatively charged oxygen-containing acid anion. The geochemical behaviors of the two are antagonistic to each other, making it difficult to coordinate management. Stabilization is a commonly used remediation measure for the treatment of heavy metal pollution in paddy soil. Through the addition of exogenous remediation agents, the mobility of heavy metal elements in the soil is correspondingly reduced.

[0004] Existing patent CN202110905728.9 relates to a method for repairing cadmium-arsenic contaminated soil, comprising the following steps: Step 1, adding sodium percarbonate to the cadmium-arsenic contaminated soil, stirring it thoroughly, and standing it for 2-4 hours to obtain the cadmium-arsenic contaminated soil after oxidation treatment, wherein the amount of sodium percarbonate added is 0.5-3wt% of the soil mass; Step 2, adding hematite powder and calcium-based compounds to the cadmium-arsenic contaminated soil after oxidation treatment, stirring it thoroughly, and stabilizing it for 3-7 days, wherein the amount of hematite powder added is 0.5-5wt% of the soil mass, and the amount of calcium-based compounds added is 0.5-2.5wt% of the soil mass; Step 3, after the soil is stabilized for 3-7 days in step 2, 3-mercaptopropylmethoxysilane is sprayed on the soil surface, and then stirred thoroughly, and stabilized for 5-10 days. This kind of repair method can oxidize and stabilize heavy metal cadmium-arsenic contaminated soils with different degrees of pollution, with good repair effect and simple repair method.

[0005] Existing patent CN202211485088.1 discloses heavy metal passivators, soil remediation materials and cadmium-arsenic composite pollutant remediation methods. The heavy metal passivators include iron salts, manganese compounds and zinc salts. The Fe-Mn-Zn ternary complex is synthesized by the secondary coprecipitation method, and the passivation material for synergistically repairing soil heavy metal cadmium and arsenic pollution is obtained after washing and drying. The disclosed remediation material generates stable chemical forms of heavy metal cadmium and arsenic through adsorption, oxidation-adsorption, reduction, ion exchange and surface complexation, reduces the migration of cadmium and arsenic in the soil, reduces its migration and diffusion capacity in the environment, reduces the ecological risks of heavy metals, and further reduces the harmful effects of heavy metals on human health. At the same time, it can also effectively remove cadmium and arsenic ions in water bodies. The preparation process of the remediation material is simple, the production cycle is short, it is easy to store, easy to use, and environmentally friendly, and can be widely used in the remediation of cadmium and arsenic composite pollution in the environment.

[0006] At present, the agents for the treatment of Cd and As composite pollution are mainly iron-based materials, but a large amount of iron-based materials is often required to achieve a more ideal stabilization effect (making the stabilization rate greater than 50%), which may pose a certain threat to soil health after addition. Based on this, the present invention provides a soil conditioner and a soil health improvement method. Summary of the invention

[0007] The purpose of the present invention is to provide a soil conditioner and a method for improving soil health. Natural minerals and waste biomass-based raw materials are used to develop non-iron-based, green and sustainable repair materials, which can achieve the synergistic stabilization of Cd and As complex pollution in the southwestern karst area, and at the same time can also achieve the improvement of soil health indicators such as microbial diversity, soil TOC, CEC, effective P, and effective K; it can not only solve the technical problem of the difficulty in synchronous stabilization of Cd and As, but also avoid the impact of stabilization materials on soil health.

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

[0009] Furthermore, the preparation method of the activated illite and montmorillonite comprises adding illite and montmorillonite to an activation solution at a solid-liquid ratio of 1 g: (5-20) mL, mixing at 60-80° C. for 1-2 hours, filtering, washing with a large amount of water until the pH is constant, and then drying to obtain the activated illite and montmorillonite.

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

[0011] Furthermore, the mixing needs to be stirred at a speed of 200-300 rpm.

[0012] Furthermore, the drying is carried out at 40-60° C. for 48-72 hours.

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

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

[0015] Furthermore, the ultrasonic oscillation time is 15-30 minutes.

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

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

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

[0019] On the other hand, the present invention also provides a soil conditioner prepared by the above method.

[0020] On the other hand, the soil conditioner and the preparation method thereof of the present invention are used in soil remediation.

[0021] On the other hand, the present invention also provides a method for improving soil health, comprising: adding a soil conditioner prepared by the preparation method according to any one of claims 1 to 7 3 to 7 days before transplanting rice seedlings, with an addition dosage of 2 to 10 t / ha and a mixing depth of 0 to 20 cm. The mixing depth refers to the depth at which the soil conditioner is mixed with the soil.

[0022] The beneficial effects of the present invention are:

[0023] The present invention uses non-ferrous materials to simultaneously achieve the three goals of paddy field soil Cd stabilization, As stabilization, and soil health improvement; the soil health improvement method of the present invention can achieve an increase in soil microbial diversity, an increase in soil TOC, an increase in soil CEC, an increase in soil effective P, and an increase in soil effective K;

[0024] The mineral used in the present invention is illite and montmorillonite rather than other clay minerals. This is because illite and montmorillonite is a widely distributed hydrophilic layered natural clay mineral, a transition product produced in the natural transformation process from montmorillonite to illite, and an intercalated mixed mineral of illite and montmorillonite. It has the properties of both montmorillonite and illite, and its pore structure is more complex, and its ductility and swelling properties are better, which is more conducive to the adsorption of heavy metals and the fixation of nutrients, and can achieve heavy metal stabilization while avoiding the loss of effective nutrients.

[0025] The activation solution in the present invention is composed of weak acid, which conforms to the concept of green chemistry, and its purpose is to achieve pore expansion, make the materials evenly mixed, increase the oxygen-containing functional groups on the surface of the materials, which is beneficial to the coordinated stabilization of As and Cd; reduce the alkalinity of the materials to avoid the activation of As after the materials are added. The material mixture after activation is acidic. At this time, adding calcium oxide is not to create an alkaline environment for the soil, but to adjust the pH of the material to neutral, avoiding a large disturbance to the soil pH, and avoiding a large disturbance to the soil pH is the key to ensuring the diversity of soil microorganisms;

[0026] The soil conditioner prepared in the present invention is rich in oxygen-containing functional groups, and achieves the coordinated stabilization of As and Cd through surface complexation; at the same time, the soil conditioner developed in the present application will not cause a large disturbance to the soil pH and Eh, which is conducive to long-term stabilization; since the low molecular weight organic acid adsorbed in the pores of illite and montmorillonite is conducive to the activity of microorganisms, the soil pH and Eh do not change significantly, thereby achieving an increase in soil microbial diversity;

[0027] The soil conditioner prepared in the present invention contains high carbon (cow dung) and illmitate CEC, which increases the TOC and CEC of the soil, increases the effective nutrient content of the soil, and further increases the effective P and K of the soil. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is 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.

[0029] Example 1

[0030] This embodiment provides a soil conditioner, the preparation steps of which include:

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

[0032] The activation solution is composed of: 1M citric acid and 1M glacial acetic acid;

[0033] (2) Preparation of soil conditioner: The activated illite and mondensis soil was mixed with dry cow dung in a mass ratio of 3:4, and the above activation solution was added to the mixture in a solid-liquid ratio of 1 g:10 mL. The mixture was first ultrasonically oscillated for 15 min, then mixed for 4 h, and activated again. After filtering, it was rinsed with a large amount of water until the pH value was constant, and then dried at a temperature of 50°C for 60 h; the dried mixture was compounded with calcium oxide in a mass ratio of 7:3 to obtain a soil conditioner.

[0034] The dry cow dung is obtained by drying fresh cow dung at 50°C for 60 hours.

[0035] The soil health improvement method in this embodiment includes: adding 2 t / ha of material 3 days before transplanting rice seedlings, and fully mixing the material with the soil at a depth of 20 cm.

[0036] Example 2

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

[0038] Example 3

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

[0040] Example 4

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

[0042] Example 5

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

[0044] Example 6

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

[0046] Comparative Example 1

[0047] On the basis of Example 1, the material dosage was adjusted to 1 t / ha, and the other steps and conditions were consistent with those in Example 1.

[0048] Comparative Example 2

[0049] On the basis of Example 1, the material dosage was adjusted to 12 t / ha, and the other steps and conditions were consistent with those in Example 1.

[0050] Comparative Example 3

[0051] On the basis of Example 1, only 3M citric acid was added without glacial acetic acid, and other steps and conditions were consistent with those in Example 1.

[0052] Comparative Example 4

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

[0054] Comparative Example 5

[0055] On the basis of Example 1, the activation step was omitted and the three raw materials were simply mixed. The other steps and conditions were consistent with those in Example 1.

[0056] Comparative Example 6

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

[0058] Comparative Example 7

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

[0060] Comparative Example 8

[0061] On the basis of Example 1, calcium oxide was not added, and other steps and conditions were consistent with Example 1.

[0062] Comparative Example 9

[0063] On the basis of Example 1, the mass ratio of the dried mixture to calcium oxide was adjusted to 1.5:1, and the other steps and conditions were consistent with those in Example 1.

[0064] Comparative Example 10

[0065] On the basis of Example 1, the mass ratio of the dried mixture to calcium oxide was adjusted to 3:1 for calcium oxide, and the other steps and conditions were the same as those in Example 1.

[0066] Comparative Example 11

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

[0068] Comparative Example 12

[0069] On the basis of Example 1, the mass ratio of activated illite and dry cow dung was adjusted to 1:2, and the 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 those in Example 1.

[0072] Comparative Example 14

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

[0078] Comparative Example 17

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

[0080] Comparative Example 18

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

[0082] Comparative Example 19

[0083] Based on Example 1, the primary activation mixing time was adjusted to 3 h, and the other steps and conditions were consistent with those in Example 1.

[0084] Comparative Example 20

[0085] Based on Example 1, the secondary activation mixing time was adjusted to 3 h, and the other steps and conditions were consistent with Example 1.

[0086] Comparative Example 21

[0087] Based on Example 1, the secondary activation mixing time was adjusted to 7 h, and the other steps and conditions were consistent with Example 1.

[0088] Test Example: The performance of the soil conditioners prepared in Examples 1-6 and Comparative Examples 1-21 was evaluated as follows:

[0089] For the rice fields in a karst area in the southwest, soil conditioner materials were added 3 days before transplanting. The deionized water extraction method was used to characterize the effective heavy metals in the soil during the rice maturity period, and the content of effective heavy metals in the soil was analyzed by ICP-MS to obtain the stabilization rate (preferably greater than 50%); the Shannon index of the soil after the addition of 16s rRNA analysis materials was used to characterize the microbial diversity (the larger the better), and then the soil TOC, CEC, effective P, and effective K content were determined at the same time. The results are shown in the following table:

[0090]

[0091]

[0092] According to the contents of the above table, the comparative examples that failed to achieve the purpose are analyzed as follows: the amount of material added in comparative example 1 is insufficient; the material in comparative example 2 is excessively added, and the microbial diversity decreases; the degree of material activation in comparative examples 3 and 4 is insufficient; the material in comparative example 5 is not activated; too much acid is introduced in comparative examples 6 and 7, inhibiting the activity of soil microorganisms; the acidity in comparative examples 8 and 10 is not effectively neutralized, inhibiting the activity of soil microorganisms, resulting in Cd activation; too much alkali is introduced in comparative example 9, causing As activation and inhibiting microbial activity; the proportion of organic matter in comparative example 11 is low, and the soil health activation effect is not obvious; the proportion of organic matter in comparative example 12 is too high, and heavy metal colloids are activated; comparative examples 13-17 have poor stabilization effects due to the replacement of minerals; comparative examples 18 and 20 are due to insufficient activation time; the activation time in comparative example 19 is too long, causing partial pore collapse, and the effect is worse; the activation time in comparative example 21 is too long, causing partial pores to be overfilled and blocked, and the effect is worse.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a soil conditioner, characterized in that the steps include: The activated illite and dry cow dung are mixed, and an activation solution is added to the mixture at a solid-liquid ratio of 1g:(5-20)mL, first ultrasonically oscillated, then mixed for secondary activation, filtered, rinsed with a large amount of water until the pH value is constant, and dried to obtain a mixture; the dried mixture is compounded with calcium oxide to obtain a soil conditioner.

2. The method for preparing a soil conditioner according to claim 1, characterized in that: The preparation method of the activated illite comprises adding illite to an activation solution at a solid-liquid ratio of 1 g: (5-20) mL, mixing at 60-80° C. for 1-2 hours, filtering, washing with a large amount of water until the pH value is constant, and then drying.

3. The method for preparing a soil conditioner according to claim 1, characterized in that: The mass ratio of the activated illite and montmorillonite to dry cow dung is 1:1-1:1.

5.

4. The method for preparing a soil conditioner according to claim 1, characterized in that: The ultrasonic oscillation time is 15-30 minutes.

5. The method for preparing a soil conditioner according to claim 1, characterized in that: The secondary activation time is 4-6h.

6. The method for preparing a soil conditioner according to claim 1, characterized in that: The mass ratio of the dried mixture to calcium oxide is 2:1-2.5:

1.

7. The method for preparing a soil conditioner according to claim 1 or 2, characterized in that: The activation solution comprises 1-3 M citric acid and 1-3 M glacial acetic acid.

8. A soil conditioner, characterized in that: The soil conditioner is prepared by the method for preparing the soil conditioner according to any one of claims 1 to 7.

9. Use of the soil conditioner according to any one of claims 1 to 7 or the preparation method of the soil conditioner according to claim 8 in soil remediation.

10. A method for improving soil health, characterized in that the steps include: The soil conditioner prepared by the preparation method according to any one of claims 1 to 7 is added 3 to 7 days before transplanting, the dosage is 2 to 10 t / ha, and the mixing depth is 0 to 20 cm.

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