A soil conditioner and a method of making the same

Abstract

This invention relates to a soil conditioner and its preparation method, addressing the problems of soil pollution and soil acidification. The soil conditioner comprises dolomite and urea. Preparation method: (I) Weigh dolomite and urea; (II) Grind dolomite and urea separately and then mix them evenly; (III) Calcine in a muffle furnace, grind, and sieve. This invention combines low-cost raw materials dolomite and urea in a specific ratio, with a simple preparation method. It not only improves soil acidification and increases soil pH but also increases soil permeability and improves soil physicochemical properties, showing broad application prospects.

Description

Technical Field

[0001] This invention relates to a modifier and its preparation method. Background Technology

[0002] Currently, applying lime is a relatively effective and commonly used method for improving acidic soils and eliminating aluminum toxicity. However, excessive or prolonged application of lime can not only cause soil compaction, but the addition of large amounts of calcium can also cause antagonism between magnesium and potassium, leading to an imbalance of the three elements in the soil and resulting in reduced yields. Excessive application of lime in acidic soils may also cause the co-precipitation of magnesium and aluminum hydrate oxides, reducing the magnesium content in the soil solution. 2+ The activity and bioavailability of plants are also important considerations. Furthermore, there are numerous reports on the application of industrial waste and minerals in acidic soil improvement, such as alkali slag, fly ash, and dolomite powder. These can all improve acidic soils, but they also have some drawbacks. For example, alkali slag and fly ash contain a certain proportion of heavy metals, posing certain environmental risks and health hazards. Dolomite powder, due to its high calcium and magnesium content, can also have an antagonistic effect on soil potassium with long-term application, affecting potassium availability. Because of its abundant reserves, low cost, and environmental friendliness, dolomite has attracted widespread attention in scientific research as a purely natural acid-reducing material.

[0003] Currently, my country's black soil commonly faces several key quality problems affecting sustainable soil utilization, including severe soil acidification. Firstly, natural acidification is unavoidable: soil silicate minerals and secondary minerals weather rapidly, leading to the loss of cations such as calcium and magnesium, while aluminum hydroxide accumulates in the soil and releases H+ in the form of aluminosilicate. + The serious soil pollution problem stems from several factors: firstly, the increasing acidification of the soil; secondly, acid rain, caused by air pollution resulting from accelerated industrialization; and thirdly, the irrational application of fertilizers in farmland, with the current promotion of chemical fertilizers in my country primarily consisting of acidic or physiologically acidic fertilizers, while the proportion of organic fertilizers is continuously decreasing, further exacerbating the soil acidification problem. The pollution is caused by several factors, including: firstly, increased emissions of waste from mining, metallurgy, and other industrial processes; secondly, heavy metal emissions from agricultural and livestock waste; and thirdly, soil acidification and the promotion of high-yield varieties leading to increased absorption and accumulation of these pollutants by crops.

[0004] Effectively controlling and mitigating soil pollution and soil acidification is a growing international problem, particularly prominent in my country. Therefore, inventing an acidification-resistant soil conditioner is of significant importance to the field of conditioner preparation technology. Summary of the Invention

[0005] This invention provides a soil conditioner and its preparation method to address the problems of soil pollution and soil acidification.

[0006] The soil conditioner of the present invention is composed of 1 to 10 parts by weight of dolomite and 1 to 40 parts by weight of urea.

[0007] The soil conditioner is prepared according to the following steps:

[0008] (a) Weigh out 1 to 10 parts of dolomite and 1 to 40 parts of urea according to the weight ratio;

[0009] (II) Grind the dolomite and urea weighed in step (I) separately and pass them through a 200-mesh sieve, then mix them evenly.

[0010] (III) The mixture obtained in step (II) is placed in a crucible and calcined in a muffle furnace under air circulation. The temperature is increased to 500℃ at a rate of 5℃ / min and held for 2 hours. The calcined residue is removed, ground in an agate mortar, and passed through a 200-mesh sieve to collect the soil conditioner.

[0011] This invention uses dolomite as a raw material, with the molecular formula CaMg(CO3)2. Dolomite is an abundant and reasonably priced mineral. It is alkaline, rich in calcium, magnesium, and other mineral elements, and is a carbonate non-metallic mineral. After application, it can increase soil pH, replenish soil mineral nutrients, improve soil physicochemical properties, enhance soil fertility, and reduce waste pollution. This invention mixes dolomite with urea and roasts it to form a typical soil conditioner with strong ion exchange and adsorption capabilities. It can effectively adsorb aluminum ions, effectively improve the utilization rate of chemical and organic fertilizers, increase soil base exchange capacity, and neutralize soil acidity. This invention can significantly improve soil pH conditions and base ion composition, reduce soil acidification and salinization caused by long-term planting, directly improve soil physicochemical properties, and increase land productivity.

[0012] This invention combines low-cost raw materials dolomite and urea in a specific ratio, resulting in a simple preparation method. This method not only improves soil acidification and increases soil pH but also enhances soil permeability and improves soil physicochemical properties. The soil conditioner described in this invention features a simple preparation process, abundant raw materials, low cost, and significant improvement effects. It is suitable for controlling soil acidification and addressing the problem of declining soil quality affecting its sustainable use, demonstrating broad application prospects. Attached Figure Description

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

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

[0015] Figure 3This is a comparison chart of the optimal application rate of soil conditioner in Example 2. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

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

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

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

[0021] Specific Implementation Method Two: In this implementation method, the soil conditioner consists of 2-8 parts by weight of dolomite and 10-30 parts by weight of urea. Other steps and parameters are the same as in Specific Implementation Method One.

[0022] Specific Implementation Method 3: In this implementation method, the soil conditioner consists of 5 parts by weight of dolomite and 10 parts by weight of urea. Other steps and parameters are the same as in Specific Implementation Method 1.

[0023] Specific Implementation Method Four: The preparation method of the soil conditioner in this implementation method is carried out according to the following steps:

[0024] (a) Weigh out 1 to 10 parts of dolomite and 1 to 40 parts of urea according to the weight ratio;

[0025] (II) Grind the dolomite and urea weighed in step (I) separately and pass them through a 200-mesh sieve, then mix them evenly.

[0026] (III) The mixture obtained in step (II) is placed in a crucible and calcined in a muffle furnace under air circulation. The temperature is increased to 500℃ at a rate of 5℃ / min and held for 2 hours. The calcined residue is removed, ground in an agate mortar, and passed through a 200-mesh sieve to collect the soil conditioner.

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

[0028] Calcining dolomite and urea under anaerobic or hypoxic conditions produces biochar. Over time, the effect of urea based on biochar weakens, possibly because aged biochar particles reduce soil porosity and adsorption capacity, and can no longer provide unstable carbon. Therefore, the ability of biochar particles to enhance soil aeration diminishes over time. Conversely, the cavitation effect of urea during air-introduced calcination and the urea-promoted dolomite transformation ensure that soil porosity and adsorption capacity do not decrease over time. In this embodiment, the air-introduced calcination step three is more economical than introducing nitrogen, argon, or other gases, and represents a promising technology for the mass production of high-performance materials. This embodiment also boasts advantages such as simple process, low cost, ease of replication, and wide applicability for facility soil improvement and acid soil remediation.

[0029] The reason for adding urea in this embodiment is that urea can serve as a starting material for synthesizing various compounds. Under calcination conditions of 500°C, it is a precursor for producing graphitized carbon nitride (g-C3N4) with a two-dimensional structure and abundant tri-triazine units. Furthermore, urea is chosen for its advantages such as low cost, wide applicability, rapid dissolution, and high nitrogen content. The nitrogen-containing functional groups in g-C3N4 can effectively bind to the surface of minerals, providing active sites for adsorption and significantly enhancing the material's adsorption capacity for cationic pollutants in soil. Moreover, urea decomposes during calcination, and the resulting gases affect the structure and morphology of the adsorbent, resulting in a larger surface area and more open pores. This structural change not only improves the adsorption capacity but also accelerates the adsorption rate, further enhancing its practicality in soil remediation.

[0030] The effect of roasting urea and dolomite together in step three of this embodiment:

[0031] Urea is typically lost through nitration and volatilization. Therefore, this embodiment requires calcining urea and dolomite at 500°C to promote the conversion of dolomite into nano-calcite. During calcination, urea undergoes pyrolysis, generating gases that cavitate the material, enhancing its surface properties. Heating dolomite and urea together also improves urea utilization efficiency and reduces negative environmental impact. In this embodiment, a modified dolomite adsorbent was successfully prepared by calcining g-C3N4- with urea as a precursor in a muffle furnace at 500°C for efficient adsorption of Al in soil. 3 + .

[0032] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that, in step (two), the dolomite and urea are ground separately in a mortar and pestle for 5-15 minutes. Other steps and parameters are the same as in Specific Implementation Method Four.

[0033] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Four in that the air pressure introduced in step (III) is 0.1–0.5 MPa. Other steps and parameters are the same as in Specific Implementation Method Four.

[0034] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Four in that the air flow rate in step (III) is 100 ml / min. Other steps and parameters are the same as in Specific Implementation Method Four.

[0035] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Four in that: in step (III), the filter residue after roasting is used...

[0036] The grinding time in the agate mortar is 5 to 15 minutes. Other steps and parameters are the same as in Specific Implementation Method Four.

[0037] Example 1: Comparative experiment to verify the performance of the soil conditioner described in this invention.

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

[0039] This embodiment sets up four groups of soil conditioners: no conditioner applied, dolomite powder applied, compound conditioner A applied, and compound conditioner B applied. Each experimental group is tested using a constant temperature shaking incubator, with the shaking incubator temperature set at 25±0.5℃ and the shaking speed at 220r / min. The performance of each group of soil conditioners is then tested.

[0040] Specific methods:

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

[0042] The compound amendment A group uses the amendment prepared by the method of this invention. The specific preparation method is as follows: Weigh 1 part dolomite and 20 parts urea according to the specified weight ratio; grind the dolomite and urea separately and pass them through a 200-mesh sieve, then mix them evenly; place the resulting mixture into a crucible, and under the premise of air circulation, place it in a muffle furnace and calcine at a heating rate of 5℃ / min to 500℃ for 2 hours. Remove the calcined residue and grind it in an agate mortar for 10 minutes, then pass it through a 200-mesh sieve to form amendment A. Amendment A is mixed with soil at a solid-solid ratio of 0.5%.

[0043] In this embodiment, the compound amendment B group uses the amendment prepared by the method of this invention. The specific preparation method is as follows: Weigh 1 part dolomite and 1 part urea according to the specified weight ratio; grind the dolomite and urea separately and pass them through a 200-mesh sieve, then mix them evenly; place the resulting mixture into a crucible, and under the premise of air circulation, place it in a muffle furnace and calcine at a heating rate of 5℃ / min to 500℃ for 2 hours. Remove the calcined residue and grind it in an agate mortar for 10 minutes, then pass it through a 200-mesh sieve to form amendment A. Amendment B is mixed with soil at a solid-solid ratio of 0.5%.

[0044] Experimental results:

[0045] 1. Figure 1 The scanning electron microscope (SEM) image of soil conditioner B in this embodiment is shown below. The results for conditioner A are as follows: Figure 3 As shown, it can be noted that soil conditioner A consists of a large number of loosely packed sponge-like particles, exhibiting a porous sponge-like structure. Figure 2 The image shown is a scanning electron microscope (SEM) image of soil conditioner B in this embodiment. The surface of soil conditioner B shows numerous fine particles aggregated, with distinct pores between them, and these pores are interconnected. The surface of soil conditioner B forms aggregates of smaller particles, and its surface is smoother than that of soil conditioner A. This microstructure is due to the release of carbon dioxide during calcination, which leaves gaps on the dolomite surface. Therefore, the dolomite surface becomes roughened, improving soil permeability.

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

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

[0048] Test treatment Soil pH No amendments 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 among different treatments 28 days after application of soil conditioner.

[0050] Test treatment Soil organic matter content (g / kg) No amendments 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 among different treatments 28 days after application of soil conditioner.

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

[0053] Table 4. Differences in total exchangeable acid content of soils under different treatments 28 days after soil amendment application.

[0054]

[0055]

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

[0057] Test treatment Soil exchangeable aluminum content (cmol / kg) No amendments 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 under different treatments 28 days after application of soil conditioner.

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

[0060] As shown in Table 1, the soil conditioner provided by this invention can significantly increase the soil pH value, indicating that the components added in this invention have a synergistic effect. The test data in Tables 1-6 show an increase in various beneficial elements. Using soil conditioner B can increase the pH value of acidic black soil from 5.9 to 7.1, indicating that the conditioner can exert its properties in a short time. The physicochemical data show that the acidified black soil has been significantly improved, the soil pH value has increased, and the active aluminum content has decreased from 1.48 cmol / kg to 0.12 cmol / kg, a reduction of 1.36 cmol / kg, essentially eliminating the harmful effects of aluminum toxicity and demonstrating excellent improvement effects on acidic black soil.

[0061] The soil conditioner of this invention has excellent performance and can be used to control soil acidification and solve the problem of soil degradation affecting its sustainable use.

[0062] Example 2 determines the optimal application rate of the soil conditioner of the present invention.

[0063] Using the dolomite powder, amendment A, and amendment B described in Example 1 as three experimental groups, with dolomite powder as the control group, and employing different application ratios, the optimal application amount of the soil amendment of this invention was determined. The three amendments were applied to the soil at solid-to-solid ratios of 0.5%, 1%, 1.5%, 2.5%, and 5%, respectively. The results are as follows: Figure 3 As shown, Figure 3 This chart compares the optimal application rates of soil conditioners, using dolomite powder as a control group. It examines soil conditioners A and B applied at different ratios to acidic black soil to screen and determine the optimal application ratio. Figure 3It can be seen that as the addition ratio gradually increases, the pH value of acidic soil does not change significantly. Therefore, we can choose an addition ratio of 0.5% to achieve both a good improvement effect on acidified or acidic black soil and the goal of reducing costs and increasing efficiency.

Claims

1. An acidic soil conditioner, characterized in that... The soil conditioner is composed of 1-10 parts by weight of dolomite and 1-40 parts by weight of urea. The preparation method of the soil conditioner is carried out according to the following steps: (a) Weigh out 1 to 10 parts of dolomite and 1 to 40 parts of urea according to the weight ratio; (ii) Grind the dolomite and urea weighed in step (i) separately and pass them through a 200-mesh sieve, then mix them evenly; (iii) The mixture obtained in step (ii) is placed in a crucible and calcined in a muffle furnace under air circulation. The temperature is increased to 500°C at a rate of 5°C / min and held for 2 hours. The calcined residue is removed, ground in an agate mortar, and passed through a 200-mesh sieve to collect the soil conditioner.

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

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

4. A method for preparing an acidic soil conditioner, characterized in that... The preparation method of the soil conditioner is carried out according to the following steps: (a) Weigh out 1 to 10 parts of dolomite and 1 to 40 parts of urea according to the weight ratio; (ii) Grind the dolomite and urea weighed in step (i) separately and pass them through a 200-mesh sieve, then mix them evenly; (iii) The mixture obtained in step (ii) is placed in a crucible and calcined in a muffle furnace under air circulation. The temperature is increased to 500°C at a rate of 5°C / min and held for 2 hours. The calcined residue is removed, ground in an agate mortar, and passed through a 200-mesh sieve to collect the soil conditioner.

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

6. The method for preparing an acidic soil conditioner according to claim 4, characterized in that... The air pressure introduced in step (iii) is 0.1~0.5MPa.

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

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

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