A soil conditioner for reducing cadmium and increasing selenium and a preparation method and application thereof

Abstract

The application belongs to the technical field of soil improver, and particularly relates to a soil improver for reducing cadmium and increasing selenium, and a preparation method and application thereof. The soil improver comprises the following components in parts by weight: 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 alkali modification. The soil improver can efficiently reduce the content of effective cadmium (Cd) in soil and increase the content of effective selenium (Se).

Description

Technical Field

[0001] This invention belongs to the field of soil conditioner technology, specifically relating to a soil conditioner that reduces cadmium and increases selenium, its preparation method, and its application. Background Technology

[0002] High cadmium (Cd) and selenium (Se) soil is a unique type of Cd pollution found in selenium-rich arable land. 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 contains Cd elements. This phenomenon leads to the release of Cd along with Se.

[0003] Investigations in selenium-rich areas have revealed varying degrees of Cd contamination in their arable land. In some severely contaminated areas, agricultural products grown there exhibited significantly elevated Cd levels, threatening the food safety of selenium-rich agricultural products in these regions. Current research on passivating agents for Cd contamination primarily focuses on single heavy metal pollution, with limited studies on the effects of passivating agents on selenium. Some soil amendments for heavy metals only reduce the bioavailability of heavy metals without improving, or even reducing, their bioavailability on selenium. Therefore, developing "selenium-enriched cadmium-inhibiting" amendments is crucial for the safe utilization of selenium-rich arable land. Summary of the Invention

[0004] To fill the gap in the application of "selenium-enriched cadmium-inhibiting" soil conditioners for reducing cadmium and increasing selenium in cadmium-contaminated farmland in naturally selenium-rich areas, this invention provides a soil conditioner for reducing cadmium and increasing selenium, its preparation method, and its application.

[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, comprising the following components by weight:

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

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

[0009] As a preferred embodiment of the cadmium-reducing and selenium-enhancing soil conditioner of the present invention, the heating and calcination conditions are: temperature 450-600℃, time 5-6h.

[0010] Compared to acid-modified attapulgite, the alkali-modified attapulgite of this invention, while altering the surface structure to increase cation exchange capacity and thus enhance Cd ion adsorption, can also increase soil pH to a certain extent, thereby increasing soil Se availability and promoting plant absorption of Se. Potassium dihydrogen phosphate and sodium silicate can reduce soil Cd availability through ion antagonism and chelation. Furthermore, phosphate and silicate ions, like selenate ions (the main form of available Se in the soil), are anionic anions and do not exhibit antagonistic effects, thus reducing their availability. The soil conditioner of this invention, prepared from modified attapulgite, potassium dihydrogen phosphate, sodium silicate, slaked lime, and zeolite, is indispensable for preventing cadmium contamination in selenium-enriched soils, and any change in the amount of raw materials will reduce its improvement effect.

[0011] The modified attapulgite, potassium dihydrogen phosphate, sodium silicate, slaked lime, and zeolite of this invention are all indispensable for selenium enrichment and cadmium inhibition.

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

[0013] As a further preferred embodiment of the cadmium-reducing and selenium-enhancing soil conditioner described in this invention, alkali modification is performed using a sodium hydroxide solution with a concentration of 1–3 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 calcined attapulgite soil to the sodium hydroxide solution is 1:4-6.

[0015] As a further preferred embodiment of the cadmium-reducing and selenium-enhancing soil conditioner described in this invention, the alkali modification time is 3-5 hours.

[0016] Secondly, 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 clay, calcine it at 450-600℃ for 5-6 hours;

[0018] S2. After mixing the calcined attapulgite with a sodium hydroxide solution of 1-3 mol / L for 3-5 hours, remove the mixture, rinse the attapulgite with water until neutral, and then air-dry and grind it to obtain modified attapulgite.

[0019] S3. Weigh 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 by weight and mix them to obtain the cadmium-reducing and selenium-enhancing soil conditioner.

[0020] As a preferred embodiment of the preparation method described in this invention, in step S1, the attapulgite clay is pulverized to 180-200 mesh.

[0021] As a preferred embodiment of the preparation method described in this invention, in step S2, the air-dried attapulgite clay is ground to 20-30 mesh.

[0022] Thirdly, the present invention provides the application of the cadmium-reducing and selenium-enhancing soil conditioner in selenium-enriched and cadmium-inhibiting soil.

[0023] Fourthly, the present invention provides the application 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, and then tilled and mixed.

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

[0025] 1. In this invention, attapulgite is calcined and then alkali-modified. Compared with commonly used acid-modified and surfactant-modified attapulgite, alkali-modified attapulgite has a better effect on increasing the available Se content in the soil and also has a better effect on reducing the available Cd content in the soil.

[0026] 2. This invention uses potassium dihydrogen phosphate and sodium silicate as constituent materials. After being applied to the soil, potassium dihydrogen phosphate and sodium silicate can be used as fertilizers to improve soil nutrients and promote crop growth. Potassium dihydrogen phosphate and sodium silicate can also reduce the availability of Cd in the soil. At the same time, phosphate and silicate are both anion-containing acid radicals, and will not produce antagonistic effects, thereby reducing their availability.

[0027] 3. This invention produces a soil conditioner that reduces cadmium and enriches selenium, exhibiting high stability and excellent cadmium-reducing and selenium-enriching effects. Furthermore, it utilizes natural materials, minimizing the risk of secondary pollution to the soil environment. Detailed Implementation

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

[0029] Example 1

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

[0031] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 450℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2 mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of quicklime and 5g of zeolite (20 mesh). This mixture was then combined with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner, which was then applied to the soil.

[0032] Example 2

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

[0034] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 450℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 40g of modified attapulgite was mixed with 5g of quicklime and 5g of zeolite (20 mesh). This mixture was then combined with 20g of potassium dihydrogen phosphate and 20g of sodium silicate to prepare a soil conditioner, which was applied to the soil.

[0035] Example 3

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

[0037] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 450℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2 mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 80g of the modified attapulgite was mixed with 5g of quicklime and 5g of zeolite (20 mesh). This mixture was then combined with 40g of potassium dihydrogen phosphate and 40g of sodium silicate to prepare a soil conditioner, which was then applied to the soil.

[0038] Example 4

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

[0040] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 550℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2 mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of quicklime and 5g of zeolite (20 mesh). This mixture was then combined with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner, which was applied to the soil.

[0041] Example 5

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

[0043] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 600℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2 mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 80g of the modified attapulgite was mixed with 5g of quicklime and 5g of zeolite (20 mesh). This mixture was then combined with 30g of potassium dihydrogen phosphate and 30g of sodium silicate to prepare a soil conditioner, which was then 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] Attapulgite was crushed to 200 mesh, and then heated in a muffle furnace at 450°C for 6 hours. The heated attapulgite was then placed in a reaction vessel and a 2 mol / L sodium hydroxide solution (mass ratio 1:5) was added and reacted for 4 hours to produce modified attapulgite. The modified attapulgite was washed 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 quicklime and 5g of zeolite (20 mesh), and then the resulting 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] Attapulgite was pulverized to 200 mesh, then heated in a muffle furnace at 450℃ for 6 hours. The heated attapulgite was then placed in a reaction vessel and reacted with 2 mol / L sodium hydroxide at a mass ratio of 1:5 for 4 hours to produce modified attapulgite. The modified attapulgite was washed with deionized water until the pH was neutral, then air-dried and ground to 20 mesh. 60g of modified attapulgite was mixed with 5g of quicklime and 5g of zeolite. This mixture was then combined with 30g of potassium dihydrogen phosphate to prepare a soil conditioner, which was applied to the soil. Comparative Example 3

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

[0051] Hydrochloric acid with a concentration of 2 mol / L was used to replace sodium hydroxide, and the rest was the same as in Example 1.

[0052] Comparative Example 4

[0053] A soil conditioner that reduces cadmium and increases selenium

[0054] The modified attapulgite was used as the sole component, and its preparation was the same as in Example 1.

[0055] To demonstrate the selenium-enriched cadmium-inhibiting effect of the soil conditioners of Examples 1-5 and Comparative Examples 1-4 in soil, the following verification experiments were conducted:

[0056] 1) Pot experiment

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

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

[0059] Table 1 Data on the effect of selenium-enriched cadmium inhibition

[0060]

[0061] Note: " / " indicates that the data item is not included.

[0062] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. To avoid redundancy, the present invention describes preferred embodiments.

[0063] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends 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 modified attapulgite, 20-40 parts potassium dihydrogen phosphate, 20-40 parts sodium silicate, 4-6 parts quicklime, and 4-6 parts zeolite. The modified attapulgite is obtained by calcining attapulgite and then modifying it with alkali. The heating and calcination conditions are: temperature 450~600℃, time 5~6 h; Alkali modification was carried out using sodium hydroxide solution with a concentration of 1-3 mol / L.

2. The soil conditioner for reducing cadmium and increasing selenium according to claim 1, characterized in that, The mass ratio of the attapulgite clay after heating and calcination to the sodium hydroxide solution is 1:4~6.

3. The soil conditioner for reducing cadmium and increasing selenium according to claim 2, characterized in that, The alkali modification time is 3-5 hours.

4. The method for preparing the cadmium-reducing and selenium-enhancing soil conditioner according to claim 3, characterized in that, Includes the following steps: S1. After crushing the attapulgite clay, calcine it at 450~600℃ for 5~6 hours; S2. After mixing the calcined attapulgite with a sodium hydroxide solution of 1-3 mol / L for 3-5 hours, remove the mixture, rinse the attapulgite with water until neutral, and then air-dry and grind it to obtain modified attapulgite. S3. Weigh 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 by weight and mix them to obtain the cadmium-reducing and selenium-enhancing soil conditioner.

5. The method for preparing the cadmium-reducing and selenium-enhancing soil conditioner according to claim 4, characterized in that, In S1, the attapulgite clay is crushed to 180-200 mesh.

6. The method for preparing the cadmium-reducing and selenium-enhancing soil conditioner according to claim 4, characterized in that, In S2, the air-dried attapulgite clay is ground to 20-30 mesh.

7. The application of the soil conditioner for reducing cadmium and increasing selenium as described in any one of claims 1 to 3 in the application of selenium enrichment and cadmium inhibition in soil.

8. The application of the cadmium-reducing and selenium-enhancing soil conditioner according to any one of claims 1 to 3 in crop cultivation, characterized in that, The cadmium-reducing and selenium-enhancing soil conditioner was applied to the soil two weeks before crop planting, and then tilled and mixed in.

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