Soil conditioner and preparation method thereof

Abstract

The invention discloses a soil conditioner and a preparation method thereof, relates to a conditioner and a preparation method thereof, and solves the problems of soil pollution and soil acidification. The soil conditioner is composed of dolomite and urea. The preparation method comprises the following steps: (1) weighing dolomite and urea; (2) respectively grinding dolomite and urea, and uniformly mixing; and (3) roasting in a muffle furnace, grinding, and passing through a hole sieve. The low-cost raw materials dolomite and urea are combined according to a specific proportion, the preparation method is simple, the acidification condition of soil can be improved, the pH value of the soil can be increased, the permeability of the soil can be increased, the physicochemical properties of the soil can be improved, and wide application prospects are achieved.

Description

Technical Field

[0001] The invention relates to an improver and a preparation method thereof. Background Art

[0002] At present, the application of lime is an effective and commonly used method to improve acidic soil and eliminate aluminum toxicity. However, the large-scale or long-term application of lime will not only cause soil compaction, but the addition of a large amount of calcium will cause antagonism to magnesium and potassium, thereby causing an imbalance of the three elements of soil calcium, potassium and magnesium, leading to a reduction in yield. Excessive application of lime in acidic soil may also cause the co-precipitation of magnesium and aluminum hydrate oxides, reducing the Mg content in the soil solution. 2+ activity and plant effectiveness. In addition, there are also a lot of reports on the application of industrial waste and minerals in acidic soil improvement. For example, alkali residue, fly ash, dolomite powder, etc. can improve acidic soil, but there are also some shortcomings. For example, alkali residue and fly ash contain a certain proportion of heavy metal elements, which pose certain environmental risks and health hazards. Dolomite powder contains a large amount of calcium and magnesium elements. Long-term application will also have an antagonistic effect on soil potassium, affecting the effectiveness of potassium. Due to the advantages of abundant reserves, low cost, and environmental friendliness of dolomite, it has attracted widespread attention in scientific research as a pure natural acid-reducing material.

[0003] At present, my country's black soil generally has the following key quality problems that affect the sustainable use of soil: serious soil acidification problem. First, the natural acidification process is inevitable: soil silicate minerals and secondary minerals weather rapidly, cations such as calcium and magnesium are lost in the soil, and aluminum hydroxide accumulates in the soil and releases H in the form of aluminosilicate. + , leading to continuous soil acidification; second, acid rain: the atmospheric pollution caused by the accelerated industrialization process has led to an increase in the frequency of acid rain; third, unreasonable fertilization of farmland: the chemical fertilizers currently promoted in my country are mainly acidic or physiologically acidic fertilizers, while the proportion of organic fertilizers is constantly decreasing, which further aggravates the problem of soil acidification. Serious soil pollution problems. First, mining and metallurgy and other industrial mining industries have led to increased emissions of "three wastes", while the heavy metal ores and associated products such as cadmium, lead, and arsenic in non-ferrous metals in the southern region are relatively high, and industrial processes have led to serious pollutant emissions; second, heavy metal emissions from agricultural and animal husbandry wastes: third, soil acidification and the promotion of high-yield varieties have led to increased absorption and accumulation of crops.

[0004] How to effectively control and reduce soil pollution and soil acidification is an increasingly serious international problem, especially in my country. Therefore, the invention of an acidifying soil conditioner has positive significance in the field of conditioner preparation technology. Summary of the invention

[0005] In order to solve the problems of soil pollution and soil acidification, the present invention provides a soil conditioner and a preparation method thereof.

[0006] The soil improver of the invention consists of 1 to 10 parts of dolomite and 1 to 40 parts of urea in parts by weight.

[0007] The preparation method of the soil conditioner is carried out according to the following steps:

[0008] (i) Weigh 1 to 10 parts of dolomite and 1 to 40 parts of urea by weight;

[0009] (ii) grinding the dolomite and urea weighed in step (i) respectively, passing through a 200-mesh sieve, and then mixing evenly;

[0010] (iii) placing the mixture obtained in step (ii) into a crucible, placing it in a muffle furnace and calcining it under air flow, heating it to 500°C at a heating rate of 5°C / min and maintaining it for 2 hours; taking out the calcined residue, grinding it with an agate mortar, passing it through a 200-mesh sieve, and collecting it to obtain a soil conditioner.

[0011] The present invention uses dolomite as raw material, and its molecular formula is CaMg(CO 3 ) 2 Dolomite is a mineral with abundant reserves and reasonable price. The raw material is alkaline and rich in mineral elements such as calcium and magnesium. It is a carbonate non-metallic mineral. After application, it can increase soil pH, supplement soil mineral nutrition, improve soil physical and chemical properties, improve soil fertility, and reduce waste pollution. The present invention mixes dolomite with urea and roasts it to form a typical soil conditioner. It has strong ion exchange and ion adsorption capabilities, can effectively adsorb aluminum ions, effectively improve the utilization rate of chemical fertilizers and organic fertilizers, increase soil base exchange capacity, and neutralize soil acidity. The present invention can significantly improve the pH conditions and base ion composition of the soil, reduce soil acidification and salinization caused by long-term planting, can directly improve soil physical and chemical properties, and improve land productivity.

[0012] The present invention combines low-cost raw materials dolomite and urea in a specific ratio, and the preparation method is simple. It can not only improve the acidification of soil and increase soil pH, but also increase soil permeability and improve soil physical and chemical properties. The soil conditioner of the present invention has a simple preparation process, sufficient raw materials, low cost, and obvious improvement effect. It is used to prevent and control soil acidification and solve the problem of affecting its sustainable utilization due to the decline of soil quality, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a scanning electron microscope image of the soil conditioner A in Example 1;

[0014] Figure 2 is a scanning electron microscope image of the soil conditioner B in Example 1;

[0015] Figure 3 This is a comparison chart of the optimal application amount of soil conditioner in Example 2. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0018] Specific implementation method 1: The soil conditioner of this implementation method is composed of 1 to 10 parts of dolomite and 1 to 40 parts of urea in parts by weight.

[0019] The modifier described in this embodiment is applied to the soil at a solid-to-solid ratio of 0.5%.

[0020] In this embodiment, the diameter of dolomite particles does not exceed 0.0750 mm; the diameter of urea particles does not exceed 0.0750 mm.

[0021] Specific implementation method 2: The soil conditioner in this implementation method is composed of 2 to 8 parts of dolomite and 10 to 30 parts of urea by weight. Other steps and parameters are the same as those in specific implementation method 1.

[0022] Specific implementation method 3: The soil conditioner in this implementation method is composed of 5 parts of dolomite and 10 parts of urea by weight. Other steps and parameters are the same as those in specific implementation method 1.

[0023] Specific embodiment 4: The preparation method of the soil conditioner in this embodiment is carried out according to the following steps:

[0024] (i) Weigh 1 to 10 parts of dolomite and 1 to 40 parts of urea by weight;

[0025] (ii) grinding the dolomite and urea weighed in step (i) respectively, passing through a 200-mesh sieve, and then mixing evenly;

[0026] (iii) placing the mixture obtained in step (ii) into a crucible, placing it in a muffle furnace and calcining it under air flow, heating it to 500°C at a heating rate of 5°C / min and maintaining it for 2 hours; taking out the calcined residue, grinding it with an agate mortar, passing it through a 200-mesh sieve, and collecting it to obtain a soil conditioner.

[0027] The modifier prepared in this embodiment is applied to the soil at a solid-to-solid ratio of 0.5%.

[0028] Calcining dolomite and urea under anaerobic or anoxic conditions will produce biochar. Over time, the effect of urea based on biochar will weaken, which may be because the aged biochar particles reduce the soil porosity and adsorption capacity and can no longer provide unstable C. Therefore, the ability of biochar particles to enhance soil aeration will weaken over time. On the contrary, the cavitation effect of urea on the material during the calcination process of air and the dolomite conversion promoted by urea make the porosity and adsorption capacity of the soil not reduced by time. In step three of this embodiment, the introduction of air for roasting is more economical than the introduction of other gases such as nitrogen and argon, and is a high-function material preparation technology with development prospects and mass production. The technical solution of this embodiment has the advantages of simple process, low cost, easy replication, and can be widely used in facility soil improvement, acid soil transformation, etc.

[0029] The reason for adding urea in this embodiment is that urea can be used as a starting material for synthesizing various compounds. Under calcination conditions of 500°C, it is a suitable material for producing graphitized carbon nitride (gC nitride) with a two-dimensional structure and rich triazine units. 3 N 4 ) is a precursor of gC, and urea is added in the present invention because of its advantages of low price, wide application, fast dissolution, and high nitrogen content. 3 N 4 The nitrogen-containing functional groups in the urea can effectively combine with the surface of the mineral, providing active sites for the adsorption of the material, thereby significantly enhancing the material's ability to adsorb cationic pollutants in the soil. In addition, urea will decompose during the calcination process, and the gas it produces will affect the structure and morphology of the adsorbent, making the adsorbent's surface area larger and the pore structure more open. This structural change can not only improve the adsorption capacity of the adsorbent, but also accelerate the adsorption rate, thereby further enhancing its practicality in soil remediation.

[0030] Effect of roasting urea and dolomite together in step 3 of this embodiment:

[0031] Urea is usually lost through nitrification and volatilization, so this embodiment requires calcining urea and dolomite at 500°C to promote the conversion of dolomite into nano-calcite. During the calcination process, urea will pyrolyze and produce gas, which will cause cavitation on the material and enhance the surface properties of the material. Heating dolomite and urea together can also improve the utilization efficiency of urea and reduce the negative impact on the environment. In this embodiment, a gC 3 N 4-Using urea as a precursor, a modified dolomite adsorbent was successfully prepared by calcination in a muffle furnace at 500°C for efficient adsorption of Al in soil 3 + .

[0032] Specific embodiment 5: This embodiment differs from specific embodiment 4 in that in step (2), dolomite and urea are ground in a mortar for 5 to 15 minutes respectively. Other steps and parameters are the same as those of specific embodiment 4.

[0033] Specific implementation method 6: This implementation method is different from specific implementation method 4 in that the pressure of the air introduced in step (3) is 0.1-0.5 MPa. The other steps and parameters are the same as those in specific implementation method 4.

[0034] Specific embodiment 7: This embodiment differs from specific embodiment 4 in that the flow rate of air introduced in step (3) is 100 ml / min. Other steps and parameters are the same as those in specific embodiment 4.

[0035] Specific embodiment eight: This embodiment differs from the specific embodiment four in that the filter residue after roasting in step (iii) is used

[0036] The grinding time of the agate mortar is 5 to 15 minutes. Other steps and parameters are the same as those of the fourth embodiment.

[0037] Example 1 Comparative experiment to verify the performance of the soil conditioner of the present invention

[0038] The soil pH value of the soil from Erlongshan Farm in Heilongjiang Province used in this embodiment is 5.8.

[0039] In this embodiment, four groups of soil conditioners are set, namely, no application of conditioner, application of dolomite powder, application of compound conditioner A, and application of compound conditioner B. Each experimental group is carried out using a constant temperature shaking table experimental device, the shaking table temperature is set to 25±0.5°C and the speed is 220r / min, and then the performance of each group of soil conditioners is tested.

[0040] Specific methods:

[0041] Dolomite powder group: Dolomite powder was used alone and mixed with soil at a solid-to-solid ratio of 0.5%.

[0042] The compounded modifier group A adopts the modifier prepared by the method of the present invention, and the specific preparation method is as follows: 1 part of dolomite and 20 parts of urea are weighed according to the weight parts; dolomite and urea are ground respectively and passed through a 200-mesh sieve, and then mixed evenly; the obtained mixture is put into a crucible, and under the premise of air flow, it is placed in a muffle furnace, and the temperature is raised to 500°C at a heating rate of 5°C / min for high-temperature roasting for 2h, and the roasted filter residue is taken out and ground with an agate mortar for 10min, and passed through a 200-mesh sieve modifier A. Modifier A and soil are mixed at a solid-to-solid ratio of 0.5%.

[0043] The compounded modifier group B used in this embodiment uses the modifier prepared by the method of the present invention, and the specific preparation method is as follows: 1 part of dolomite and 1 part of urea are weighed according to the weight ratio; dolomite and urea are ground separately and passed through a 200-mesh sieve, and then mixed evenly; the obtained mixture is put into a crucible, and under the premise of air flow, it is placed in a muffle furnace, and the temperature is raised to 500°C at a heating rate of 5°C / min and high-temperature roasted for 2h, and the slag after roasting is taken out and ground with an agate mortar for 10min, and passed through a 200-mesh sieve modifier A. Modifier B is mixed with soil at a solid-to-solid ratio of 0.5%.

[0044] Experimental results:

[0045] 1. Figure 1 The results of soil conditioner A are shown in the SEM image of soil conditioner B in this example. Figure 3 As shown, it can be noticed that soil conditioner A is composed of a large number of loosely packed sponge-like particles and presents a porous sponge-like state. Figure 2 The scanning electron microscope image of the soil conditioner B in this embodiment shows that many fine particles are gathered on the surface of the soil conditioner B, and there are obvious pores between the fine particles, and the pores are connected. The surface of the soil conditioner B forms an aggregate of smaller particles, and the surface is smoother than that of the soil conditioner A. This microstructure is because the release of carbon dioxide leaves gaps on the dolomite surface during the calcination process. Therefore, the dolomite surface becomes rough, which can improve the permeability of the soil.

[0046] 2. The performance test results of each group of experiments are shown in Tables 1 to 6, wherein Table 1 shows the difference in soil pH of different treatments 28 days after the application of the soil conditioner, Table 2 shows the difference in soil organic matter content of different treatments 28 days after the application of the soil conditioner, Table 3 shows the difference in soil organic carbon content of different treatments 28 days after the application of the soil conditioner, Table 4 shows the difference in exchangeable total acid content of different soil treatments 28 days after the application of the soil conditioner, Table 5 shows the difference in exchangeable aluminum content of different soil treatments 28 days after the application of the soil conditioner, and Table 6 shows the difference in exchangeable hydrogen ion content of different soil treatments 28 days after the application of the soil conditioner.

[0047] Table 1 Differences in soil pH of different treatments after 28 days of application of soil conditioners

[0048] Experimental treatment Soil pH No improver applied 5.9 Dolomite powder 6.9 Soil Conditioner A 6.8 Soil conditioner B 7.1

[0049] Table 2 Differences in soil organic matter content in different treatments after 28 days of application of soil conditioners

[0050] Experimental treatment Soil organic matter content (g / kg) No improver applied 52.10 Dolomite powder 52.09 Soil Conditioner A 52.00 Soil conditioner B 49.88

[0051] Table 3 Differences in soil organic carbon content in different treatments after 28 days of application of soil conditioners

[0052] Experimental treatment Soil organic carbon content (g / kg) No improver applied 30.22 Dolomite powder 30.21 Soil Conditioner A 30.16 Soil conditioner B 28.93

[0053] Table 4 Differences in soil exchangeable total acid content in different treatments after 28 days of application of soil conditioners

[0054]

[0055]

[0056] Table 5 Differences in exchangeable aluminum content in soils of different treatments 28 days after application of soil conditioners

[0057] Experimental treatment Exchangeable aluminum content in soil (cmol / kg) No improver applied 1.48 Dolomite powder 1.10 Soil Conditioner A 0.85 Soil conditioner B 0.12

[0058] Table 6 Differences in exchangeable hydrogen ion content in soils of different treatments 28 days after application of soil conditioners

[0059] Experimental treatment Soil exchangeable hydrogen ion content (cmol / kg) No improver applied 0.65 Dolomite powder 0.40 Soil Conditioner A 0.70 Soil conditioner B 0.68

[0060] It can be seen from the contents recorded in Table 1 that the improver provided by the present invention can significantly increase the soil pH value, indicating that the components added by the present invention play a synergistic role. From the test data in Tables 1 to 6, it can be seen that various beneficial elements are increased. The use of soil improver B can increase the pH value of acidic black soil from 5.9 to 7.1, which shows that the improver can play its characteristics in a short time. From the physical and chemical data, it can be seen that the acidified black soil has been well improved, the soil pH value has been increased, and the active aluminum has been reduced from 1.48 cmol / kg to 0.12 cmol / kg, with a reduction of 1.36 cmol / kg, which basically eliminates the harm of aluminum poisoning and plays an excellent improvement role on acidic black soil.

[0061] The improver of the present invention has excellent performance and can be used to prevent and control soil acidification and solve the problem of soil quality degradation affecting its sustainable utilization.

[0062] Example 2 Determining the Optimal Application Rate of the Soil Improver of the Present Invention

[0063] The dolomite powder, improver A and improver B described in Example 1 were used as the three experimental groups, and the dolomite powder was used as the control group. Different application ratios were used to determine the optimal application amount of the soil improver of the present invention. The three groups of improvers were applied to the soil at a solid-to-solid ratio of 0.5%, 1%, 1.5%, 2.5% and 5%, respectively. The results are shown in FIG. Figure 3 As shown, Figure 3 This is a comparison chart of the best application amount of soil conditioners. That is, with dolomite powder as the control group, soil conditioner A and soil conditioner B were added to acidic black soil at different addition ratios to screen and determine the best addition ratio of soil conditioners. Figure 3 It can be seen that with the gradual increase in the addition ratio, the pH value of the acidic soil does not change significantly. Therefore, we can choose a solid-to-solid ratio of 0.5%, which can not only have a good improvement effect on acidified or acidic black soil, but also achieve the purpose of reducing costs, increasing efficiency and saving costs.

Claims

1. A soil conditioner, characterized in that The soil conditioner consists of 1 to 10 parts of dolomite and 1 to 40 parts of urea in parts by weight.

2. A soil conditioner according to claim 1, characterized in that The soil conditioner consists of 2 to 8 parts of dolomite and 10 to 30 parts of urea in parts by weight.

3. A soil conditioner according to claim 1, characterized in that The soil conditioner consists of 5 parts of dolomite and 10 parts of urea in terms of weight.

4. The method for preparing a soil conditioner according to claim 1, characterized in that The preparation method of the soil conditioner is carried out according to the following steps: (i) Weigh 1 to 10 parts of dolomite and 1 to 40 parts of urea by weight; (ii) grinding the dolomite and urea weighed in step (i) respectively, passing through a 200-mesh sieve, and then mixing evenly; (iii) placing the mixture obtained in step (ii) into a crucible, placing it in a muffle furnace and calcining it under air flow, heating it to 500°C at a heating rate of 5°C / min and maintaining it for 2 hours; taking out the calcined residue, grinding it with an agate mortar, passing it through a 200-mesh sieve, and collecting it to obtain a soil conditioner.

5. The method for preparing a soil conditioner according to claim 4, characterized in that In step (ii), dolomite and urea are ground in a mortar for 5 to 15 minutes respectively.

6. The method for preparing a soil conditioner according to claim 4, characterized in that The pressure of the air introduced in step (iii) is 0.1-0.5 MPa.

7. The method for preparing a soil conditioner according to claim 4, characterized in that The flow rate of air introduced in step (iii) is 100 ml / min.

8. The method for preparing a soil conditioner according to claim 4, characterized in that The calcined filter residue in step (iii) is ground with an agate mortar for 5 to 15 minutes.

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