CN110938435A - Long-acting soil cadmium passivator, preparation method and application - Google Patents
Long-acting soil cadmium passivator, preparation method and application Download PDFInfo
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- CN110938435A CN110938435A CN201911220956.1A CN201911220956A CN110938435A CN 110938435 A CN110938435 A CN 110938435A CN 201911220956 A CN201911220956 A CN 201911220956A CN 110938435 A CN110938435 A CN 110938435A
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Abstract
The invention discloses a long-acting soil cadmium passivator, a preparation method and application thereof. The long-acting soil cadmium passivator comprises calcite mineral powder, humic acid and a binder, wherein the mass fraction of the humic acid is 1-5%, and the mass fraction of the binder is 3-6%; during preparation, calcite mineral powder is placed in a disc granulator; humic acid and a binder are mixed and then added with water to form an aqueous solution, the aqueous solution enters a disc granulator through multi-angle spraying, and the materials are agglomerated into granules through granulation. According to the long-acting soil cadmium passivator, calcite mineral powder is selected to be matched with humic acid, so that the in-season passivation effect is improved, and a good subsequent passivation effect can be kept; the passivator prepared by the preparation method provided by the invention has regular particles and high dispersion speed after meeting water.
Description
Technical Field
The invention belongs to the field of polluted soil treatment, and particularly relates to a long-acting soil cadmium passivator, a preparation method and application thereof.
Background
In the treatment of medium and light cadmium polluted soil, the biological effectiveness of cadmium is reduced by using the passivator, so that the accumulation of cadmium in the plant body and the edible part is reduced, and the operability in production practice is strong, so that the method has popularization and application prospects.
The action mechanism of the soil cadmium passivator reported in domestic literature is mainly characterized in that the bioavailability of cadmium in soil is reduced by the self-adsorption, chelation and fixation functions of the passivator, such as biochar, zeolite and the like, or by adjusting the acid-base environment of soil, such as lime, powdered rock phosphate and the like.
The current practical application of the soil cadmium passivator mainly has the problems of unsatisfactory passivation effect, main effect on current seasons, poor after-effect and the like, and the aim of realizing safe production in medium and light cadmium-polluted soil is difficult to ensure, so that the popularization and the application of the passivator in the cadmium-polluted soil treatment are limited.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a long-acting soil cadmium passivator which is applied to soil to improve the in-season passivating effect and keep good subsequent passivating effect.
Therefore, the invention adopts the following technical scheme: the long-acting soil cadmium passivator comprises calcite mineral powder, humic acid and a binder, wherein the mass fraction of the humic acid is 1-5%, and the mass fraction of the binder is 3-6%.
The calcite mineral powder is gradually decomposed in soil, and is used for improving the pH value of the soil and improving the season passivation effect. According to the invention, the proper bonding strength is achieved by adding the binder, and the humic acid is added to ensure the current-season passivation effect and simultaneously keep a good subsequent passivation effect.
Preferably, the calcium carbonate content of the calcite mineral powder is more than 90%.
Preferably, the particle size of the calcite mineral powder is 10-30 meshes, and the mass fraction of humic acid is 2-4%. The size of the particle size determines the decomposition rate after the cadmium passivation solution is applied to the soil, and further determines the passivation effect on the cadmium in the soil. The coarser the particle size, the slower the decomposition rate, the longer the duration effect of the passivation, but the lower the passivation effect in the season. Conversely, the finer the particle size, the better the passivation effect but the shorter the duration. According to the invention, mineral powder with the processing particle size of 10-30 meshes is selected, and 3% of humic acid is matched, so that the in-season decomposition rate is improved to a certain extent, and a good follow-up effect is kept.
Most preferably, the particle size of the calcite mineral powder is 20 meshes, and the mass fraction of humic acid is 3%. The invention selects the mineral powder with the processing grain diameter of 20 meshes and matches with 3 percent of humic acid, thereby not only improving the in-season decomposition rate to a certain extent, but also keeping the best follow-up effect.
Preferably, the binder is corn starch, the particle size of the binder is 50-150 meshes, and the mass fraction of the binder is 5%. If the granules cannot be rapidly dispersed during harrowing after being applied to soil, gradual degree difference with the granules as the center is formed due to small mobility of the mineral powder, so that spatial difference of passivation effect is generated. The present invention alters the above situation by adding corn starch.
Most preferably, the particle size of the binder is 100 mesh, and the mass fraction thereof is 5%. The passivant of the invention takes 100-mesh corn starch as a binder, a certain bonding strength can be achieved by adding 5% in the granulation process, and the passivant can be dispersed after being wetted with water for 3-5 minutes, so that the passivant and soil can be uniformly mixed under the conditions of mechanical spreading and mechanical plowing.
The invention adopts another technical scheme that: the preparation method of the long-acting soil cadmium passivator comprises the steps of placing calcite mineral powder in a disc granulator; humic acid and a binder are mixed and then added with water to form an aqueous solution (the addition of water is only required to dissolve the binder and can be used for spraying), and the aqueous solution enters a disc granulator through multi-angle spraying, so that the materials are agglomerated into granules through granulation. The water solution is adopted for spraying, and the component proportion can be flexibly adjusted to achieve the purpose of particle forming.
Furthermore, the bottom of the disc granulator is made of glass fiber reinforced plastics, so that the adhesion of inner walls generated during granulation can be effectively reduced, irregular granulation is prevented, and the material return amount is greatly reduced.
Furthermore, a plurality of separation nets are arranged inside the disc granulator, and the granules are automatically sieved during granulation, so that the sizes of the formed granules are similar.
The invention adopts another technical scheme that: when the long-acting soil cadmium passivator is applied to soil, in order to ensure that the passivator is uniformly mixed with the soil when the long-acting soil cadmium passivator is applied to the soil in the field, the application time of the soil with different textures is selected as follows: the sandy or sandy loam with light texture can be applied before and after irrigation and then plowed and harrowed; before irrigation, the clay or clay loam with heavy texture needs to be harrowed under a dry condition, a passivator is applied after large and small soil blocks are smashed, and finally the harrowing is uniform; the soil blocks are not easy to be broken mechanically after the heavy soil is watered, so that the uniformity is influenced.
After the passivating agent is applied, the depth of the plough is controlled to reach the plough bottom layer, and deep ploughing is carried out once when the plough layer is thick, so that the soil and the passivating agent are uniformly mixed within the root growth range.
The invention has the following beneficial effects: according to the long-acting soil cadmium passivator, calcite mineral powder is selected to be matched with humic acid, so that the in-season passivation effect is improved, and a good subsequent passivation effect can be kept. The long-acting soil cadmium passivator prepared by the preparation method provided by the invention has regular particles and high dispersion speed after meeting water.
Drawings
FIG. 1 is a graph showing the results of tests in long sand late rice with the passivator according to example 3 of the invention;
FIG. 2 is a graph showing the results of a test conducted on a single rice thoroughfare Jiangqing by the passivating agent according to example 3 of the present invention;
FIG. 3 is a graph showing the results of a test conducted on single season rice in Shaoguangyuan county, the passivator of the present invention as described in example 3;
FIG. 4 is a graph showing the change of the pH value of the soil after 1 year of application of ore powder with different particle sizes.
Detailed Description
The invention is further described with reference to the drawings and the detailed description.
Example 1
The embodiment provides a long-acting soil cadmium passivator, which consists of 1% by mass of humic acid, 3% by mass of corn starch and the balance of calcite mineral powder. The calcium carbonate content of the calcite mineral powder is 86%, and the particle size is 10 meshes. The grain size of the corn starch is 50 meshes.
Example 2
The embodiment provides a long-acting soil cadmium passivator, which consists of 5 mass percent of humic acid, 6 mass percent of corn starch and the balance of calcite mineral powder. The calcium carbonate content of the calcite mineral powder is 90%, and the particle size is 30 meshes. The grain size of the corn starch is 150 meshes.
Example 3
The embodiment provides a long-acting soil cadmium passivator, which consists of 3% by mass of humic acid, 5% by mass of corn starch and the balance calcite mineral powder. The calcium carbonate content of the calcite mineral powder is 94%, and the particle size is 20 meshes. The grain size of the corn starch is 100 meshes.
Example 4
This example provides a method of preparing the long-acting soil cadmium deactivator of examples 1-3, by placing calcite mineral powder in a disc granulator; mixing humic acid and binder, adding water to form aqueous solution, spraying at multiple angles, granulating, and oven drying. The bottom of the disc granulator is made of glass fiber reinforced plastics. A plurality of separation nets are arranged in the disc granulator, and the granules are automatically screened during granulation, so that the sizes of the formed granules are similar.
The following tests were carried out using the deactivant described in example 3.
1. The field test effect of the passivator on reducing the cadmium content of rice. The results of the field plot test in different contaminated fields are shown in FIGS. 1-3.
In FIG. 1, in the test of late rice in northern mountain town of Chansha county, Hunan, the content of cadmium in the comparison rice is 0.711mg/kg, the lowest content in the passivating agent treatment is 0.128mg/kg, and the maximum reduction amplitude is 82.0%.
In the figure 2, in the test of the lotus Zhengdan single cropping rice of the thoroughfare area, the cadmium content of the contrast rice is 0.220mg/kg, the lowest content in the passivating agent treatment is 0.041mg/kg, and the maximum reduction amplitude is 81.4%.
In fig. 3, the passivant application plot test was performed on single-season rice in the new river town of the Wenyuan county, Shaoguan city under different water conditions in the same rice field and the same rice variety. Under the condition of dry farming, the cadmium content of the reference rice is 0.761mg/kg, the content in the passivator treatment is 0.203mg/kg, and the maximum reduction amplitude is 73.3 percent. Under the flooding condition of the whole growth period, the cadmium content of the contrast rice and the cadmium content of the passivant-treated rice are 0.073mg/kg and 0.071mg/kg respectively. Under the condition that the rice cadmium accumulation amount is low, the effect of the passivator is not obvious.
2. The sustained effect of the passivating agent.
Table 1. cadmium content of rice as a result of passivant application effect localization test: mg/kg
The results of four years before the positioning test show that the passivating agent shows a slow release process after being applied to soil, the passivating effect is not the most remarkable in the current season, the passivating effect is the most remarkable in the early rice of the next year, and then the passivating agent shows a slow descending trend.
3. The soil passivator with different cadmium pollution degrees has application effects.
TABLE 2 cadmium content (mg/kg) of rice using passivator in different soil
Under different soil cadmium contents, the cadmium content of the rice in season is obviously reduced after the passivant is applied, but according to the requirements of the national food safety standard, the passivant can be applied to the soil with medium and light cadmium pollution to meet the requirements of the edible safety limit value of the rice.
4. The effect of field application.
The application demonstration of the passivator for the early rice field is carried out in North mountain town of Chansha county in Hunan in 2019, and the dosage is 15t/hm2And the area is 3.6 mu. The cadmium content of the rice without the passivator is 0.713mg/kg, and the cadmium content of the rice after the passivator is applied is 0.097mg/kg, which is reduced by 86.4%.
The proportioning and selecting process of the long-acting soil cadmium passivator in the embodiment 3 of the invention is as follows:
1. balance between seasonal effect and sustained effect
The main material selected by the invention is calcite mineral powder with the effective component calcium carbonate content of more than 90%, and the mineral powder is gradually decomposed in soil so as to improve the pH value of the soil. The size of the particle size determines the decomposition rate after the cadmium passivation solution is applied to the soil, and further determines the passivation effect on the cadmium in the soil. The coarser the particle size, the slower the decomposition rate, the longer the lasting effect of the passivation effect, but the lower the effect in the season. Conversely, finer particle sizes are season effective but short in duration.
FIG. 4 shows the data at 15t/hm2Under the dosage, the mineral powder with different grain diameters is directly applied and is applied after 3 percent of humic acid is proportioned, and the pH value of the soil changes after 3 months. After directly applying for 3 months, the pH difference of the soil between 20-mesh treatment and 200-mesh treatment is 0.86, and after applying after matching 3% humic acid, the difference is 0.35 and is reduced by 0.51.
Therefore, the mineral powder with the processing particle size of 20 meshes is selected, and 3% of humic acid is matched, so that the in-season decomposition rate is improved to a certain extent, and the optimal subsequent effect is kept. The field positioning test result shows that the passivation effect reaches 80% in season and lasts for more than four years.
2. Binder selection and proportioning in granular product manufacture
In field application, the powder is difficult to be used for mechanical application, manual application is time-consuming and uneven, and the powdered ore has small mobility after entering the soil, so that uneven application can generate difference of passivation effect on a horizontal space.
If the granules cannot be rapidly dispersed during harrowing after being applied to soil, gradual degree difference with the granules as the center is formed due to small mobility of the mineral powder, so that spatial difference of passivation effect is generated.
The invention takes 100-mesh corn starch as a binder, and a certain bonding strength can be achieved by adding 5 percent in the granulation process, while the corn starch meets the water humidity
And dispersing the soil after 3-5 minutes, and ensuring that the passivator is uniformly mixed with the soil under the conditions of mechanical broadcasting and mechanical raking.
Claims (10)
1. The long-acting soil cadmium passivator is characterized by comprising 1-5% by mass of calcite mineral powder, 3-6% by mass of humic acid and 3-6% by mass of a binder.
2. The long-acting soil cadmium passivator as claimed in claim 1, wherein the calcium carbonate content of the calcite mineral powder is above 90%.
3. The long-acting soil cadmium passivator as claimed in claim 2, wherein the particle size of the calcite mineral powder is 10-30 mesh, and the mass fraction of humic acid is 2-4%.
4. The long-acting soil cadmium passivator as claimed in claim 3, wherein the particle size of the calcite mineral powder is 20 meshes, and the mass fraction of humic acid is 3%.
5. The long-acting soil cadmium passivator as claimed in any one of claims 1 to 4, wherein the binder is corn starch with a particle size of 50-150 mesh and a mass fraction of 5%.
6. The long-acting soil cadmium passivator of claim 5 wherein the particle size of the binder is 100 mesh.
7. The method for preparing the long-acting soil cadmium passivator of any one of claims 1 to 6, wherein calcite mineral powder is placed in a disc granulator; humic acid and a binder are mixed and then added with water to form an aqueous solution, the aqueous solution enters a disc granulator through multi-angle spraying, and the materials are agglomerated into granules through granulation.
8. The preparation method of claim 7, wherein the bottom of the disk pelletizer is made of glass fiber reinforced plastic.
9. The manufacturing method according to claim 7, wherein a plurality of separation nets are arranged inside the disc granulator, and the particle size is automatically sieved during granulation so that the formed particles are similar in size.
10. The long-acting soil cadmium passivator of any one of claims 1 to 6 for use in soil,
in order to ensure that the passivator is uniformly mixed with the soil when the passivator is applied in the field, the application time of the soil with different textures is selected as follows: the sandy or sandy loam with light texture can be applied before and after irrigation and then plowed and harrowed; before irrigation, the clay or clay loam with heavy texture needs to be harrowed under a dry condition, a passivator is applied after large and small soil blocks are smashed, and finally the harrowing is uniform;
after the passivating agent is applied, the depth of the plough harrow is controlled to reach the plough bottom layer, and one-time deep ploughing is required when the plough layer is thick.
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Cited By (2)
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| CN111996006A (en) * | 2020-07-24 | 2020-11-27 | 河南省地质矿产勘查开发局第一地质矿产调查院 | Calcite-based modifier for heavy metal cadmium pollution of agricultural land |
| CN113652233A (en) * | 2021-09-22 | 2021-11-16 | 河南省地质矿产勘查开发局第一地质矿产调查院 | Calcite passivator and application thereof |
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