Iron-based modifier for rapidly degrading farmland soil pesticide and application method of iron-based modifier

Abstract

The invention discloses an iron-based modifier capable of rapidly degrading farmland soil pesticides and an application method of the iron-based modifier. The iron-based modifier comprises 85-95 parts of industrial micron iron powder and 5-15 parts of nitrogen and sulfur doped biochar. The application method of the iron-based modifier comprises the steps that firstly, the iron-based modifier is spread to the surface layer of farmland soil, ploughing and uniform mixing are conducted, and the concentration of the iron-based modifier is 0.25-1.0 g / kg; then irrigating the farmland, covering a film, preserving moisture, isolating oxygen, maintaining for 5-7 days, and uncovering the film; after the water naturally drops, the crop seeds are sown into the soil, and water and fertilizer management is carried out until harvesting is carried out. The iron-based modifier disclosed by the invention can be used for remarkably reducing the content of pesticides in farmland soil and subsequent crops and rapidly reducing the phytotoxicity of residual pesticides in the soil to the crops, and the soil remediation efficiency is high.

Description

Technical Field

[0001] The present invention relates to the technical field of farmland soil pollution remediation, and in particular to an iron-based improver for rapidly degrading farmland soil pesticides and an application method thereof. Background Art

[0002] At present, soil remediation technologies include biochar, compost, zeolite and other stabilizer fixation technologies, chemical agent leaching technologies such as ferric chloride, in-situ electrokinetic remediation, and plant and microbial remediation. However, the above technologies are large in scale, expensive, and time-consuming, making it difficult to achieve large-scale improvement of organically contaminated farmland; at the same time, they are prone to secondary pollution and lead to problems such as soil structure damage and soil fertility degradation.

[0003] Zero-valent iron has high reactivity and can be used as a remediation material to effectively remove pollutants such as organochlorine and heavy metals in the environment. At the same time, iron is the fourth most abundant element in the earth's crust and the most abundant transition metal element on earth; therefore, zero-valent iron is also considered an environmentally friendly soil conditioner.

[0004] For example, the invention patent application with application publication number CN106800939A discloses a repair agent for treating soil heavy metal composite pollution, which includes: 6-8 parts of modified nano carbon black, 2-5 parts of sodium bentonite loaded nano zero-valent iron, 1-2 parts of phosphate minerals and 5-10 parts of decomposed agricultural and forestry waste. Its preparation method is as follows: (1) crushing the phosphate minerals and decomposed agricultural and forestry waste into powder with a particle size of 100-200 mesh, drying and setting aside; (2) mixing the modified nano carbon black, phosphate mineral salt, sodium bentonite loaded nano zero-valent iron and decomposed agricultural and forestry waste according to the formula, stirring in a closed container, and preparing a repair agent for treating soil heavy metal composite pollution.

[0005] The application concentration of nano zero-valent iron in industrial soil remediation is as high as 10-20g / kg. However, as the research deepens, more and more evidence shows that nano zero-valent iron can have toxic effects on a variety of organisms based on size effects. For example, it is reported that broad-leaved cattail and poplar seedlings were cultured in nano zero-valent iron suspensions of different concentrations. The observation results showed that nano zero-valent iron can slow down the growth of broad-leaved cattail and poplar seedlings when the addition amount is higher than 200mg / kg, and symptoms such as yellowing of leaves appear.

[0007] Therefore, it is necessary to establish a low-cost nano-zero-valent iron application technology for rapid repair of pesticide pollution in farmland, which can significantly reduce the pesticide content in farmland soil and subsequent crops, quickly reduce the damage of residual pesticides in the soil to crops, and have high soil remediation efficiency. Summary of the invention

[0008] The invention provides an iron-based modifier for rapidly degrading pesticides in farmland soil and an application method thereof. The method can significantly improve the rapid repair effect of pesticides in pesticide-contaminated farmland soil in a short period of time, reduce the harm of pesticides to subsequent crops, reduce pesticide residues in agricultural products, ensure crop growth, and promote agricultural safety production and sustainable utilization of agricultural environmental resources.

[0009] The purpose of the present invention is to provide an iron-based improver for rapidly degrading pesticides in farmland soil as a method for controlling soil pesticide pollution.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] The present invention provides a method for preparing an iron-based modifier, the preparation method comprising the following steps:

[0012] S1: Take 1-10g of biomass raw material with dry weight and 100-500ml of 1-5g / L thiourea aqueous solution for impregnation and mixing, the stirring speed is 200-800rpm / min, and the stirring time is 2-10h; after stirring evenly, put the impregnated mixed slurry into a refrigerator for freezing; put the frozen slurry into a freeze dryer to remove excess water to obtain a biochar precursor. The dried biochar precursor is placed in an atmosphere furnace, and preheated to 700-900℃ at a heating rate of 1-20℃ / min with nitrogen as the protective gas and maintained for 2-3h. Finally, a black solid is obtained after natural cooling in a nitrogen atmosphere, washed with deionized water several times, and freeze-dried to obtain nitrogen-sulfur co-doped biochar material.

[0013] S2: industrial iron powder and nitrogen-sulfur co-doped biochar powder are mixed evenly according to weight proportions and placed in a zirconia ball mill, zirconia beads are added to the zirconia ball mill, and then the zirconia ball mill is placed in a planetary ball mill, and ball milled at a speed of 400r / min for 10 hours to obtain an iron-based modifier.

[0014] Preferably, as a better implementation mode, the weight ratio of the industrial iron powder and the nitrogen-sulfur co-doped biochar powder is 85-95:5-15.

[0015] Preferably, as a preferred embodiment, the method for preparing the nitrogen-sulfur co-doped biochar material comprises the following steps:

[0016] Another object of the present invention is to provide an application method of an iron-based modifier for rapidly degrading pesticides in farmland soil, comprising the following steps:

[0017] (1) Sprinkling the iron-based improver onto the surface of farmland soil and mechanically tilling the soil to fully mix the iron-based improver with the soil. The concentration of the iron-based improver is 0.25-1.0 g / kg.

[0018] (2) The farmland is then irrigated and covered with film to retain moisture and isolate oxygen. The film is removed after 5-7 days of maintenance. After the water has dried up naturally, the crop seeds are sown into the soil and water and fertilizer management is carried out until harvest.

[0019] Furthermore, as a preferred embodiment, the pesticides include one or more of neonicotinoid pesticides, amide pesticides, dinitroaniline pesticides, organophosphorus pesticides, and the like.

[0020] Furthermore, as a preferred embodiment, the concentration of the iron-based modifier is 0.25-1.0 g / kg, and the tillage depth is 15-20 cm.

[0021] Furthermore, as a preferred embodiment, the irrigation refers to the soil moisture content reaching more than 60%, and the covering measure refers to covering the soil surface with agricultural film.

[0022] The present invention has found in experiments that applying iron-based improvers to farmland soil can significantly reduce the pesticide content in farmland soil and subsequent crops, quickly reduce the damage of residual pesticides in the soil to crops, and improve soil remediation efficiency and crop production efficiency.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The nitrogen-sulfur-doped biochar iron-based improver of the present invention can improve the reaction activity of zero-valent iron by doping biochar with nitrogen and sulfur, and achieve rapid degradation of pesticides in the soil. The effect is significantly higher than that of the iron-based improver synthesized from undoped biochar. After 5-7 days of improvement, the pesticide content in the farmland soil is significantly and rapidly reduced.

[0025] (2) The method of the present invention applies an iron-based amendment to agricultural soil contaminated by pesticides. It is found that there is an interaction between the iron-based amendment and crops. This can not only significantly reduce the content of pesticides in organically contaminated farmland and crops, and reduce the damage to subsequent crops, but also ensure an increase in crop yields, thereby improving soil remediation efficiency and crop production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Fresh weight and total iron content of corn seedlings in soil contaminated with acetochlor treated with different iron-based amendments in Example 1 and Comparative Example 1.

[0027] Figure 2 The residual amount of acetochlor in the soil and leaves of corn seedlings treated with different iron-based amendments in Example 1 and Comparative Example 1.

[0028] Figure 3 Fresh weight and total iron content of lettuce in soil contaminated with thiamethoxam under different application concentrations of the iron-based amendment in Example 2.

[0029] Figure 4 The thiamethoxam residues in soil and lettuce leaves treated with different application concentrations of the iron-based amendment in Example 2.

[0030] Figure 5 The fresh weight of lettuce and the residue of thiamethoxam in Example 2, Comparative Example 2 and commercial nano zero-valent iron treatment. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments. The following are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto.

[0032] Example 1

[0033] Take 10g of rice straw with dry weight and soak it with 500ml of 5g / L thiourea aqueous solution, the stirring speed is 500rpm / min, and the stirring time is 8h; after stirring evenly, put the soaked mixed slurry into a refrigerator and freeze it; put the frozen slurry into a freeze dryer to remove excess water to obtain a biochar precursor.

[0034] The dried biochar precursor was further placed in an atmosphere furnace, pre-heated to 900°C at a heating rate of 10°C / min with nitrogen as the protective gas and maintained for 2 hours, and finally naturally cooled under a nitrogen atmosphere to obtain a black solid, which was washed several times with deionized water and freeze-dried to obtain a nitrogen-sulfur co-doped biochar material.

[0035] Industrial iron powder and nitrogen-sulfur co-doped biochar powder were mixed evenly in a weight ratio of 90:10 and placed in a zirconia ball mill, zirconia beads were added to the zirconia ball mill, and then the zirconia ball mill was placed in a planetary ball mill, and ball milled at a speed of 400 r / min for 10 hours to obtain an iron-based modifier;

[0036] This example uses acetochlor artificially contaminated soil at a concentration of 5 mg / kg; an iron-based modifier is thrown onto the surface of the soil artificially contaminated with acetochlor, and the soil is tilled to fully mix the iron-based modifier with the soil, and the concentration of the iron-based modifier is 1.0 g / kg; the farmland is then irrigated, covered with a film to keep moisture and isolate oxygen, and the film is removed after 7 days of maintenance; corn seeds are sown into the soil after the water naturally dries up, and the growth of corn, the residual amount of acetochlor in the soil and the plants are observed. The total iron in the soil is digested by microwave and then measured by atomic absorption spectrometry.

[0037] Example 2

[0038] Take 5g of leaf powder with a dry weight and soak it in 500ml of 5g / L sulfamide aqueous solution, the stirring speed is 600rpm / min, and the stirring time is 10h; after stirring evenly, put the soaked mixed slurry into a refrigerator to freeze; put the frozen slurry into a freeze dryer to remove excess water to obtain a biochar precursor.

[0039] The dried biochar precursor was further placed in an atmosphere furnace, and pre-heated to 700°C at a heating rate of 15°C / min with nitrogen as the protective gas and maintained for 1.5 hours. Finally, a black solid was obtained after natural cooling under a nitrogen atmosphere. The solid was washed several times with deionized water and freeze-dried to obtain a nitrogen-sulfur co-doped biochar material.

[0040] Industrial iron powder and nitrogen-sulfur co-doped biochar powder were mixed evenly in a weight ratio of 85:15 and placed in a zirconia ball mill, zirconia beads were added to the zirconia ball mill, and then the zirconia ball mill was placed in a planetary ball mill, and ball milled at a speed of 300 r / min for 8 hours to obtain an iron-based modifier;

[0041] This example uses artificial poisoning with thiamethoxam at a concentration of 5 mg / kg; the iron-based modifier is thrown onto the surface of the soil artificially poisoned with acetochlor, and the soil is ploughed to fully mix the iron-based modifier with the soil. The application concentrations of the iron-based modifier are 0.10, 0.25 and 0.50 g / kg respectively; the farmland is then irrigated, covered with a film to keep moisture and oxygen away, and the film is removed after 5 days of maintenance; lettuce seeds are sown into the soil after the water naturally dries up, and the growth of lettuce, the residue of thiamethoxam in the soil and plants are observed. The total iron in the soil is determined by atomic absorption spectrometry after microwave digestion.

[0042] Comparative Example 1

[0043] 10 g of dried rice straw was placed in an atmosphere furnace, and preheated to 900 °C at a heating rate of 10 °C / min with nitrogen as the protective gas and maintained for 2 h. Finally, a black solid was obtained after natural cooling in a nitrogen atmosphere, that is, undoped biochar material.

[0044] Industrial iron powder and undoped biochar powder were mixed evenly in a weight ratio of 90:10 and placed in a zirconia ball mill, zirconia beads were added to the zirconia ball mill, and then the zirconia ball mill was placed in a planetary ball mill, and ball milled at a speed of 400 r / min for 10 hours to obtain an undoped control iron-based modifier;

[0045] This example uses acetochlor for artificial contamination at a concentration of 5 mg / kg; a control iron-based modifier is thrown onto the surface of the soil artificially contaminated with acetochlor, and plowing is performed to fully mix the iron-based modifier with the soil, and the concentration of the iron-based modifier is 1.0 g / kg; the farmland is then irrigated, covered with a film to keep moisture and oxygen away, and the film is removed after 7 days of maintenance; corn seeds are sown into the soil after the water naturally dries up, and the growth of corn, the residual amount of acetochlor in the soil and the plants are observed. The total iron in the soil is digested by microwave and then determined by atomic absorption spectrometry.

[0046] Comparative Example 2

[0047] Place 10g of dried leaf powder in an atmosphere furnace, pre-heat to 700℃ at a heating rate of 15℃ / min with nitrogen as the protective gas and maintain for 1.5h, finally, naturally cool down under a nitrogen atmosphere to obtain a black solid, wash it several times with deionized water, and freeze-dry it to obtain undoped biochar material.

[0048] Industrial iron powder and undoped biochar powder were mixed evenly in a weight ratio of 85:15 and placed in a zirconia ball mill, zirconia beads were added to the zirconia ball mill, and then the zirconia ball mill was placed in a planetary ball mill, and ball milled at a speed of 300 r / min for 8 hours to obtain an undoped control iron-based modifier;

[0049] This example uses artificial poisoning with thiamethoxam at a concentration of 5 mg / kg; the iron-based modifier is thrown onto the surface of the soil artificially poisoned with acetochlor, and the soil is ploughed to fully mix the iron-based modifier with the soil, and the concentrations of the iron-based modifier are 0.10, 0.25 and 0.50 g / kg respectively; the farmland is then irrigated, covered with a film to keep moisture and oxygen away, and the film is removed after 5 days of maintenance; after the water naturally dries up, lettuce seeds are sown into the soil, and the growth of lettuce, the residue of thiamethoxam in the soil and plants are observed. The total iron in the soil is digested by microwave and determined by atomic absorption spectrometry.

[0050] The experimental results are as follows Figure 1-2 As shown, in Example 1 and Comparative Example 1, 1.0 g / kg of iron-based modifier was applied to farmland contaminated with acetochlor, and it was found that there was an interaction between the iron-based modifier and the corn plants, which not only ensured the improvement of the growth ability of corn and slowed down the occurrence of acetochlor damage, but also significantly reduced the content of acetochlor in the soil and corn plants.

[0051] The experimental results are as follows Figure 3-4As shown, in Example 2, different concentrations of iron-based modifiers were applied to farmland soil contaminated with thiamethoxam, and it was found that the iron-based modifier at a dosage of 0.25 g / kg or more could not only ensure the increase in lettuce yield, but also significantly reduce the content of thiamethoxam in organically contaminated farmland soil and lettuce; and the increase in lettuce yield and the reduction in thiamethoxam content were positively correlated with the concentration of the iron-based modifier.

[0052] This example uses commercial nano zero-valent iron and undoped control iron-based improver (Comparative Example 2) as the control group of the iron-based improver (Example 2) of the present invention. The dosage concentration of the three is 0.5g / kg, and the rest of the contents are the same. The experimental results are as follows Figure 5 As shown, the iron-based modifier of Example 2 was applied to farmland soil contaminated with the pesticide thiamethoxam, and it was found that the iron-based modifier significantly improved the yield of lettuce and reduced the content of thiamethoxam in farmland soil and crops contaminated with organic pesticides, which was significantly better than the pesticide control, commercial nano zero-valent iron and undoped control iron-based modifier (Comparative Example 2). The above test results show that the iron-based modifier can achieve synchronous degradation of farmland soil pesticides and promote crop growth, and its performance is excellent, significantly better than commercial nano zero-valent iron and undoped control iron-based modifiers.

[0053] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. An iron-based conditioner for rapidly degrading pesticides in farmland soil and an application method thereof, comprising the following steps: S1: Preparation of nitrogen-sulfur co-doped biochar, adding biomass raw materials to a nitrogen-sulfur compound aqueous solution, fully immersing and then freezing in a refrigerator; placing the frozen slurry in a freeze dryer to remove excess water to obtain a biochar precursor; placing the dried biochar precursor in an atmosphere furnace for pyrolysis to obtain a black solid, washing it with deionized water several times and then freeze-drying it to obtain a nitrogen-sulfur co-doped biochar material; Preparation of S2 iron-based modifier: industrial micron iron powder and nitrogen-sulfur co-doped biochar are mixed according to the mass ratio, and after being evenly mixed, they are placed in a ball milling jar to which zirconium oxide beads have been added, and then the ball milling jar is placed in a planetary ball mill, and ball milled at a speed of 300-400r / min for 8-20h to obtain the iron-based modifier; S3: Sprinkling the iron-based amendment onto the surface of the farmland soil and mechanically tilling the soil to fully mix the iron-based amendment with the soil; S4: The farmland is then irrigated, covered with a film to retain moisture and isolate oxygen, and the film is removed after 5-7 days of maintenance; After the water has dried up naturally, sow the crop seeds into the soil and manage water and fertilizer until harvest.

2. The method for preparing an iron-based conditioner for rapidly degrading farmland soil pesticides according to claim 1, characterized in that: The biomass fibers in step S1 include crop straw, forestry waste, newspapers, waste paper, etc.

3. The method for preparing an iron-based conditioner for rapidly degrading farmland soil pesticides according to claim 1, characterized in that: The nitrogen-containing sulfur compounds in step S1 include but are not limited to thiourea and sulfamide.

4. The method for preparing an iron-based conditioner for rapidly degrading farmland soil pesticides according to claim 1, characterized in that: In the step S1, 1-10 g of biomass raw material with a dry weight is soaked and mixed with 100-500 ml of an aqueous solution of a nitrogen-containing sulfur compound with a concentration of 1-5 g / L, the stirring speed is 200-800 rpm / min, and the stirring time is 2-10 h; after stirring evenly, the soaked mixed slurry is placed in a refrigerator and frozen; the frozen slurry is placed in a freeze dryer to remove excess water to obtain a biochar precursor.

5. The method for preparing an iron-based conditioner for rapidly degrading farmland soil pesticides according to claim 1, characterized in that: In the step S1, the dried biochar precursor is placed in an atmosphere furnace, and is preheated to 700-900°C at a heating rate of 1-20°C / min with nitrogen as the protective gas and maintained for 2-3 hours. Finally, a black solid is obtained after natural cooling in a nitrogen atmosphere, which is then washed several times with deionized water and freeze-dried to obtain a nitrogen-sulfur co-doped biochar material.

6. The iron-based modifier as described in S2 of claim 1, characterized in that The content of industrial micron iron powder (50-100 microns) is 85-95 parts, and the content of nitrogen-sulfur co-doped biochar is 5-15 parts. After the two are mixed, they are ball-milled at a speed of 300-400r / min for 8-20h.

7. The pesticide-contaminated farmland soil as described in S3 of claim 1, characterized in that: The pesticides include neonicotinoid pesticides, amide pesticides, dinitroaniline pesticides, and organophosphorus pesticides.

8. The iron-based conditioner for rapidly degrading farmland soil pesticides and its application method as claimed in claim 1, characterized in that: The concentration of iron-based amendment in S3 is 0.25-1.0 mg / kg, and the tillage depth is 15-20 cm.

9. The irrigation and film covering maintenance as described in S4 of claim 1, characterized in that: The irrigation mentioned above refers to the soil moisture content reaching more than 60%, and the film covering measure refers to the use of agricultural film to cover the soil surface.

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