Soil conditioner capable of reducing cadmium and increasing selenium as well as preparation method and application of soil conditioner

Abstract

The invention belongs to the technical field of soil amendments, and particularly relates to a cadmium-reducing selenium-increasing soil amendment and a preparation method and application thereof. The soil conditioner disclosed by the invention is prepared from the following components in parts by weight: 40 to 80 parts of modified attapulgite, 20 to 40 parts of monopotassium phosphate, 20 to 40 parts of sodium silicate, 4 to 6 parts of slaked lime and 4 to 6 parts of zeolite, the modified attapulgite is obtained by heating and calcining attapulgite and then carrying out alkali modification. The soil conditioner disclosed by the invention can be used for efficiently reducing the content of effective cadmium (Cd) in soil and increasing the content of effective selenium (Se).

Description

Technical Field

[0001] The invention belongs to the technical field of soil conditioners, and in particular relates to a soil conditioner for reducing cadmium and increasing selenium, and a preparation method and application thereof. Background Art

[0002] High-cadmium (Cd) and selenium-rich (Se) soil is a unique type of Cd pollution existing in selenium-rich farmland. The Cd element that causes the pollution mainly comes from the weathering of the parent rock. During the natural soil formation process, the parent rock that weathers to form selenium-rich soil often has the phenomenon of Cd element accompanying it. This phenomenon will cause the release of Cd together with Se.

[0003] Investigations and studies on selenium-rich areas have found that selenium-rich farmland in these areas has varying degrees of Cd pollution, and agricultural products planted in some seriously polluted farmland have more Cd exceeding the standard, posing a threat to the food safety of local selenium-rich agricultural products in Se-rich areas. At present, the development of passivators for Cd pollution mainly focuses on the single pollution of heavy metals, and there is little research on the effect of passivators on Se. Some soil heavy metal improvers only reduce the effectiveness of heavy metals, but do not improve or even reduce the effectiveness of Se. Therefore, the development of "selenium-rich cadmium-blocking" improvers is of great significance to the safe use of selenium-rich farmland. Summary of the invention

[0004] In order to make up for the lack of "selenium-rich cadmium-blocking" soil conditioners in reducing cadmium and enriching cadmium in cadmium-contaminated farmland in natural selenium-rich areas, the present invention provides a cadmium-reducing and selenium-enhancing soil conditioner and a preparation method and application thereof.

[0005] The present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a soil conditioner for reducing cadmium and increasing selenium, which comprises the following components by weight:

[0007] 40-80 parts of modified attapulgite, 20-40 parts of potassium dihydrogen phosphate, 20-40 parts of sodium silicate, 4-6 parts of slaked lime, and 4-6 parts of zeolite;

[0008] The modified attapulgite is obtained by heating and calcining attapulgite and then performing alkali modification.

[0009] As the preferred cadmium-reducing and selenium-enhancing soil conditioner of the present invention, the heating and calcining conditions are: temperature 450-600° C., time 5-6 hours.

[0010] Compared with acid-modified attapulgite, the alkali-modified attapulgite of the present invention can improve soil pH to a certain extent while changing the surface structure of attapulgite to increase the cation exchange capacity so that the Cd ion adsorption capacity is larger, so as to increase the effectiveness of soil Se and promote the absorption of Se by plants. Potassium dihydrogen phosphate and sodium silicate can reduce the effectiveness of soil Cd through ion antagonism and chelation. At the same time, phosphate and silicate belong to the same negative acid root ion as selenate, the main form of existence of effective Se in the soil, and will not produce antagonism, thereby reducing its effectiveness. The soil conditioner prepared by modified attapulgite, potassium dihydrogen phosphate, sodium silicate, slaked lime and zeolite of the present invention is indispensable in terms of soil selenium enrichment and cadmium resistance, and any change in the amount of raw materials will also reduce its improvement effect.

[0011] The modified attapulgite, potassium dihydrogen phosphate, sodium silicate, slaked lime and zeolite of the present invention are indispensable in terms of selenium enrichment and cadmium inhibition.

[0012] Modified attapulgite, 20-40 parts of potassium dihydrogen phosphate, 20-40 parts of sodium silicate, 4-6 parts of slaked lime, 4-6 parts of zeolite

[0013] As a further preferred embodiment of the soil conditioner for reducing cadmium and increasing selenium according to the present invention, the alkali modification adopts a sodium hydroxide solution with a concentration of 1 to 3 mol / L.

[0014] As a further preferred embodiment of the cadmium-reducing and selenium-enhancing soil conditioner of the present invention, the mass ratio of the heated and calcined attapulgite to the sodium hydroxide solution is 1:4-6.

[0015] As a further preferred embodiment of the soil conditioner for reducing cadmium and increasing selenium according to the present invention, the alkali modification time is 3 to 5 hours.

[0016] In a second aspect, the present invention provides a method for preparing the cadmium-reducing and selenium-enhancing soil conditioner, comprising the following steps:

[0017] S1. After crushing the attapulgite, calcining at 450-600°C for 5-6h;

[0018] S2, mixing the calcined attapulgite with a sodium hydroxide solution having a concentration of 1 to 3 mol / L and reacting for 3 to 5 hours, then taking it out, washing the attapulgite with water until it is neutral, and then air-drying and grinding it to obtain modified attapulgite;

[0019] S3. Calculate by weight, weigh 40 to 80 parts of modified attapulgite, 20 to 40 parts of potassium dihydrogen phosphate, 20 to 40 parts of sodium silicate, 4 to 6 parts of slaked lime, and 4 to 6 parts of zeolite, and mix them to obtain the soil conditioner for reducing cadmium and increasing selenium.

[0020] As a preferred embodiment of the preparation method of the present invention, in S1, attapulgite is crushed to 180-200 mesh.

[0021] As a preferred embodiment of the preparation method of the present invention, in S2, the air-dried attapulgite is ground into 20-30 mesh.

[0022] In a third aspect, the present invention provides the use of the cadmium-reducing and selenium-enhancing soil conditioner in soil that is rich in selenium and blocks cadmium.

[0023] In a fourth aspect, the present invention provides the use of the cadmium-reducing and selenium-enhancing soil conditioner in crop planting, wherein the cadmium-reducing and selenium-enhancing soil conditioner is applied to the soil two weeks before crop planting, followed by tillage and mixing.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In the present invention, the attapulgite is alkali-modified after heating and calcining. Compared with the commonly used acid-modified and surfactant-modified attapulgite, the alkali-modified attapulgite has a better effect on increasing the effective Se content in the soil, and also has a good effect on reducing the effective Cd content in the soil.

[0026] 2. The present invention uses potassium dihydrogen phosphate and sodium silicate as constituent materials. Potassium dihydrogen phosphate and sodium silicate can be used as fertilizers after being applied to the soil to improve soil nutrients and promote crop growth. Potassium dihydrogen phosphate and sodium silicate can also reduce the effectiveness of soil Cd. At the same time, phosphate and silicate are both negative acid radical ions in the main existing form of selenate in the effective state of Se in the soil, and will not produce antagonism, thereby reducing its effectiveness.

[0027] 3. The cadmium-reducing and selenium-enriching soil conditioner produced by the present invention has high stability and good cadmium-reducing and selenium-enriching effects. Moreover, the material is natural and the risk of secondary pollution to the soil environment is relatively small. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with specific examples, but it should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0029] Example 1

[0030] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0031] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 450°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh). The above mixture was then mixed with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner and applied to the soil.

[0032] Example 2

[0033] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0034] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 450°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 40g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh). The above mixture was then mixed with 20g of potassium dihydrogen phosphate and 20g of sodium silicate to prepare a soil conditioner and applied to the soil.

[0035] Example 3

[0036] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0037] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 450°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 80g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh). The above mixture was then mixed with 40g of potassium dihydrogen phosphate and 40g of sodium silicate to prepare a soil conditioner and applied to the soil.

[0038] Example 4

[0039] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0040] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 550°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh). The above mixture was then mixed with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner and applied to the soil.

[0041] Example 5

[0042] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0043] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 600°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 80g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh). The above mixture was then mixed with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner and applied to the soil.

[0044] Comparative Example 1

[0045] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0046] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 450°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 60g of the modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite (20 mesh), and then the prepared soil conditioner was applied to the soil.

[0047] Comparative Example 2

[0048] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0049] The attapulgite was crushed to 200 mesh, and then the crushed attapulgite was heated at 450°C in a muffle furnace for 6 hours. The heated attapulgite was placed in a reactor and 2 mol / L sodium hydroxide was added at a mass ratio of 1:5 to react for 4 hours to prepare modified attapulgite. The modified attapulgite was rinsed with deionized water until the pH was neutral, and then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of slaked lime and 5g of zeolite. The above mixture was then mixed with 30g of potassium dihydrogen phosphate to prepare a soil conditioner and applied to the soil. Comparative Example 3

[0050] A soil conditioner for reducing cadmium and increasing selenium is prepared by the following steps:

[0051] The sodium hydroxide was replaced by hydrochloric acid having a concentration of 2 mol / L, and the rest was the same as in Example 1.

[0052] Comparative Example 4

[0053] A soil conditioner for reducing cadmium and increasing selenium

[0054] The modified attapulgite is used as the only component, and the preparation of the modified attapulgite is the same as that in Example 1.

[0055] In order to prove the selenium-enriching and cadmium-blocking effects of the soil conditioners of Examples 1 to 5 and Comparative Examples 1 to 4 of the present invention in the soil, the following verification tests were conducted:

[0056] 1) Pot plant test

[0057] The potted test was conducted in the experimental greenhouse in Yangling District, Xianyang City, Shaanxi Province from April 2024 to June 2024. The soil used was from Hengkou Town, Hanbin District, Ankang City, Shaanxi Province. The pH of the test soil sample was 6.26, the organic matter content was 31.92g / kg, the cadmium content was 1.34mg / kg, and the selenium content was 0.840mg / kg. A total of 8 different treatment groups were set up, with 2kg of soil in each pot. The amount of soil conditioner added to each treatment was 3% of the soil mass, and the test soil without conditioner was used as a blank control (CK). Soil samples were collected 45 days after the conditioner was added (regular watering was performed to keep the soil moist), and the soil available Se and Cd were determined, and the soil available Cd removal rate and soil available Se growth rate were calculated.

[0058] The results are shown in Table 1. The soil conditioners of Examples 1 to 5 of the present invention all have good cadmium reduction and selenium enrichment effects, and are significantly better than those of Comparative Examples 1 to 4.

[0059] Table 1 Selenium-rich cadmium-blocking effect data

[0060]

[0061] Note: “ / ” means that the data is not included.

[0062] It should be noted that when the claims of the present invention involve numerical ranges, it should be understood that the two endpoints of each numerical range and any numerical value between the two endpoints can be selected. In order to avoid redundancy, the present invention describes a preferred embodiment.

[0063] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0064] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A soil conditioner for reducing cadmium and increasing selenium, characterized in that: Calculated by weight, it includes the following components: 40-80 parts of modified attapulgite, 20-40 parts of potassium dihydrogen phosphate, 20-40 parts of sodium silicate, 4-6 parts of slaked lime, and 4-6 parts of zeolite; The modified attapulgite is obtained by heating and calcining attapulgite and then performing alkali modification.

2. The soil conditioner for reducing cadmium and increasing selenium according to claim 1, characterized in that: The heating and calcining conditions are: temperature 450-600° C., time 5-6 hours.

3. The soil conditioner for reducing cadmium and increasing selenium according to claim 2, characterized in that: The alkali modification is carried out using a sodium hydroxide solution with a concentration of 1 to 3 mol / L.

4. The soil conditioner for reducing cadmium and increasing selenium according to claim 3, characterized in that: The mass ratio of the heated and calcined attapulgite to the sodium hydroxide solution is 1:4-6.

5. The soil conditioner for reducing cadmium and increasing selenium according to claim 4, characterized in that: The time for alkali modification is 3 to 5 hours.

6. The method for preparing the soil conditioner for reducing cadmium and increasing selenium according to claim 5, characterized in that: The following steps are involved: S1. After crushing the attapulgite, calcining at 450-600°C for 5-6h; S2, mixing the calcined attapulgite with a sodium hydroxide solution having a concentration of 1 to 3 mol / L and reacting for 3 to 5 hours, then taking it out, washing the attapulgite with water until it is neutral, and then air-drying and grinding it to obtain modified attapulgite; S3. Calculate by weight, weigh 40 to 80 parts of modified attapulgite, 20 to 40 parts of potassium dihydrogen phosphate, 20 to 40 parts of sodium silicate, 4 to 6 parts of slaked lime, and 4 to 6 parts of zeolite, and mix them to obtain the soil conditioner for reducing cadmium and increasing selenium.

7. The method for preparing the soil conditioner for reducing cadmium and increasing selenium according to claim 6, characterized in that: In S1, attapulgite is crushed to 180-200 meshes.

8. The method for preparing the soil conditioner for reducing cadmium and increasing selenium according to claim 6, characterized in that: In S2, the air-dried attapulgite is ground into 20-30 mesh.

9. Use of the cadmium-reducing and selenium-enhancing soil conditioner according to any one of claims 1 to 5 in selenium-enriched and cadmium-blocking soil.

10. Use of the soil conditioner for reducing cadmium and increasing selenium according to any one of claims 1 to 5 in crop planting, characterized in that: The cadmium-reducing and selenium-enhancing soil conditioner is applied to the soil two weeks before crop planting, and then the soil is tilled and mixed.

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