A method for improving acidified soil based on slow-release amendment

Abstract

The present invention discloses a method for improving acidified soil using a slow-release soil conditioner, comprising the following steps: S1, pretreatment of coal gangue; S2, preparation of humic acid; S3, preliminary soil treatment; S4, reuse treatment; S5, pulping; S6, curing; and S7, deep soil treatment. The present invention uses coal gangue as the main raw material, prepares humic acid in two steps, and then utilizes the reuse of the humic acid to finally prepare a soil conditioner. To address the problem of high heavy metal content in acidified soil, a secondary treatment method is used, which can improve the effect of the secondary treatment after preliminary soil pH adjustment. This solves the problem that traditional coal gangue or its modified substances are ineffective in treating acidified soil, achieves optimal economic benefits, and maximizes the effect of the two soil conditioners while saving on usage.

Description

Technical Field

[0001] The present invention relates to the technical field of soil treatment, and in particular to a method for improving acidified soil based on a slow-release improver. Background Art

[0002] Soil pH is crucial to plant growth. However, in pursuit of yields, traditional agricultural practices such as liming, burning manure, and applying organic fertilizers have been gradually abandoned, leading to an imbalance in nutrient levels in cultivated soils. The long-term and extensive application of chemical fertilizers is a major cause of soil acidification. Acidification is a key aspect of the weathering process, causing a decrease in pH and the formation of acidic soils. This affects the activity of soil organisms, alters the form of nutrients in the soil, reduces nutrient availability, and promotes the dissolution of free manganese and aluminum ions into the soil solution, which can be toxic to crops.

[0003] Traditional measures to control acidified soils include applying lime, adjusting acidity, and supplementing calcium to increase nutrient availability. However, given the presence of numerous other pollutants in acidified soils, these traditional methods often have drawbacks. For example, as soil acidity increases, the accumulation of heavy metals such as chromium and cadmium in the soil increases significantly, and traditional methods are unable to effectively suppress these heavy metals.

[0004] Gangue itself is a complex material composed of various rocks and minerals, with a low carbon content. Generally, the calorific value of gangue increases with increasing carbon mass fraction, while the volatile matter decreases with increasing ash content. Due to its high combined content of SiO2, Al2O3, and Fe2O3, the ash melting point of gangue ranges from 1050 to 1800°C, making it suitable for use as a refractory material. Gangue primarily consists of mineral components such as quartz, clay minerals, and carbonaceous materials, and is very similar to natural zeolite. It can be used to prepare aluminum-silicon and carbon-based chemical products and as an adsorbent.

[0005] At present, some scholars have studied the application of coal gangue or its modified substances in the soil as an amendment, but there are few studies that provide a systematic method for preparing and applying the amendment for acidified soil. Summary of the Invention

[0006] In response to the above-mentioned problems, the present invention provides a method for improving acidified soil based on a slow-release amendment.

[0007] The technical solution of the present invention is:

[0008] A method for improving acidified soil based on a slow-release amendment comprises the following steps:

[0009] S1. Gangue pretreatment: The gangue raw material is ball-milled and then sieved through a 100-140 mesh sieve to obtain gangue particles. The gangue particles are frozen at -10--6°C for 4-5 hours, taken out, and heated at 230-240°C for 10-15 minutes to obtain activated gangue particles.

[0010] S2. Preparation of humic acid: The activated gangue particles prepared in step S1 are mixed with a nitric acid solution, stirred and reacted for 0.5 to 1 hour to obtain pre-oxidized gangue particles. The pre-oxidized gangue particles are taken out and mixed with a strong alkaline solution, wherein the mass concentration of the pre-oxidized gangue particles is 12 to 15 g / L. The reaction temperature is controlled to be 100±5°C, stirred and reacted for 1.5 to 2 hours, cooled to room temperature, and centrifuged to collect the supernatant. Hydrochloric acid solution is added to the supernatant to make up the volume, and the mixture is precipitated, centrifuged, washed, and dried to obtain humic acid powder.

[0011] S3, preliminary soil treatment: the humic acid powder prepared in step S2 is mixed with biochar in a weight ratio of 1:1 to obtain a preliminary soil conditioner, and the preliminary soil conditioner is added to the acidified soil to be treated in an amount of 80-120 kg / mu, and the soil moisture content is controlled to 30-35% for 7-10 days;

[0012] S4, recycling treatment: recovering the mixture of the preliminary soil conditioner and the partially acidified soil in step S3 as a recycled soil conditioner;

[0013] S5. Slurry preparation: mixing the activated gangue particles prepared in step S1 with fly ash, cement, starch binder, aluminum powder, and the recycled soil conditioner in step S4, adding water, and continuously stirring and mixing with ultrasonic stirring for 1 to 2 hours to obtain a preliminary slurry, wherein the weight ratio of the activated gangue particles to water, fly ash, cement, starch binder, aluminum powder, and recycled soil conditioner is: 1000: 600 to 800: 20 to 30: 40 to 50: 5 to 8: 0.5 to 1: 400 to 500, wherein the recycled soil conditioner is the recycled soil conditioner recovered in all steps S4;

[0014] S6, curing: placing the preliminary slurry prepared in step S5 in a mold and curing at a constant temperature for 10 to 12 hours, and drying and crushing after demoulding to obtain a slow-release acidified soil conditioner;

[0015] S7, deep soil treatment: evenly distribute all the slow-release acidified soil conditioner in step S6 and apply it to the acidified soil that has been preliminarily treated in step S3.

[0016] Furthermore, in step S2, the mass fraction of the nitric acid solution is 10%, and the weight ratio of the nitric acid solution to the activated coal gangue particles is 1:4-5.

[0017] Description: Nitric acid solution can be used to activate coal gangue and improve its activity.

[0018] Furthermore, the mass fraction of the strong alkaline solution in step S2 is 10%, and the solute of the strong alkaline solution is a mixture of sodium pyrophosphate and sodium hydroxide in a weight ratio of 1:1.

[0019] Description: Strong alkaline solution can be used to dissolve coal gangue and extract humic acid.

[0020] Furthermore, in step S2, the stirring rate is 60-80 rpm, the room temperature is 25-27°C, the centrifugal speed is 5000-8000 rpm, the molar concentration of the hydrochloric acid solution is 1-2 mol / L, the amount of hydrochloric acid solution added is 100-150% of the total amount of pre-oxidized coal gangue particles and strong alkaline solution, the washing is performed three times with anhydrous ethanol, the drying temperature is 60-70°C, and the drying time is 1-2 hours.

[0021] Furthermore, the biochar in step S3 is straw biochar or rice husk biochar.

[0022] Description: By mixing biochar with humic acid extracted from coal gangue and then conducting preliminary soil treatment, the soil pH can be initially adjusted and heavy metals can be complexed, which can facilitate better results in subsequent secondary treatment.

[0023] Furthermore, the total mass of the recycled soil conditioner in step S4 is 80-85% of the total mass of the added preliminary soil conditioner, and the proportion of acidified soil in the recycled soil conditioner does not exceed 10 wt %.

[0024] Note: By optimizing the reuse ratio of the initial soil conditioner, the best economic effect can be achieved, and the effect of the two soil conditioners can be maximized while saving the dosage.

[0025] Furthermore, the ultrasonic stirring power in step S5 is 500-800W.

[0026] Furthermore, in step S6, the curing temperature is 55-60° C., and the particle size of the crushed slow-release acidified soil conditioner is less than 3 mm.

[0027] Note: By optimizing and adjusting the curing temperature, the soil conditioner can be ensured to have good water retention and heat preservation properties.

[0028] Furthermore, in step S7, the slow-release acidified soil conditioner in step S6 is applied to the acidified soil in an amount of 200 to 300 kg / mu.

[0029] Note: We provide two different application methods for the slow-release acidified soil conditioner prepared by the method of the present invention. One of them is to apply it to the acidified soil that has been preliminarily treated during the preparation process to further deepen the treatment of the acidified soil in the area. It is generally used when the acidified soil pollution in the area is relatively serious.

[0030] The other method is to use the humic acid powder and biochar prepared in step S2 to effectively control the pollution level of the acidified soil after preliminary treatment. The slow-release acidified soil conditioner prepared in this case can be applied to acidified soils in other areas with any pollution level, and the appropriate application amount can be selected according to the pollution level. The scope of application is no longer limited to acidified soils that have undergone preliminary treatment, and the application is more extensive.

[0031] The beneficial effects of the present invention are:

[0032] The method for improving acidified soil based on a slow-release improver of the present invention uses coal gangue as a main raw material, prepares humic acid in two steps, and finally prepares a soil improver by recycling the humic acid. To address the problem of high heavy metal content in acidified soil, secondary treatment is adopted, which can improve the effect of secondary treatment after preliminary adjustment of soil pH, solves the problem that traditional coal gangue or its modified substances have poor treatment effect on acidified soil, achieves the best economic effect, and maximizes the effect of the two soil improvers while saving dosage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of a method for improving acidified soil based on a slow-release improver. DETAILED DESCRIPTION

[0034] Example 1

[0035] A method for improving acidified soil based on a slow-release amendment comprises the following steps:

[0036] S1. Gangue pretreatment: The gangue raw material is ball-milled and then sieved through a 150-mesh sieve to obtain gangue particles. The gangue particles are frozen at -8°C for 4.5 hours, taken out, and heated at 235°C for 12 minutes to obtain activated gangue particles.

[0037] S2. Preparation of humic acid: The activated gangue particles prepared in step S1 were mixed with nitric acid solution, wherein the mass fraction of the nitric acid solution was 10%, and the weight ratio of the nitric acid solution to the activated gangue particles was 1:4.5. The mixture was stirred for 1 hour to obtain pre-oxidized gangue particles. The pre-oxidized gangue particles were taken out and mixed with a strong alkaline solution, wherein the mass fraction of the strong alkaline solution was 10%, and the solute of the strong alkaline solution was sodium pyrophosphate and sodium hydroxide mixed in a weight ratio of 1:1. The mass concentration of the pre-oxidized gangue particles was 13 g / L. The reaction temperature was controlled. The mixture is stirred at 100° C. for 2 hours, cooled to room temperature, and then centrifuged to collect the supernatant. Hydrochloric acid solution is added to the supernatant to make up the volume, and the mixture is precipitated, centrifuged, washed, and dried in sequence to obtain humic acid powder. The stirring rate is 70 rpm, the room temperature is 26° C., the centrifugal speed is 6000 rpm, the molar concentration of the hydrochloric acid solution is 1.5 mol / L, the amount of the hydrochloric acid solution added is 120% of the total amount of the pre-oxidized coal gangue particles and the strong alkaline solution, the washing is performed three times with anhydrous ethanol, the drying temperature is 65° C., and the drying time is 1.5 hours.

[0038] S3. Preliminary soil treatment: The humic acid powder prepared in step S2 was mixed with biochar in a weight ratio of 1:1, where the biochar was rice husk biochar, to obtain a preliminary soil conditioner. The preliminary soil conditioner was added to the acidified soil to be treated in an amount of 100 kg / mu, and the soil moisture content was controlled to 32% for 8 days;

[0039] S4, recycling treatment: recovering the mixture of the preliminary soil conditioner and part of the acidified soil in step S3 as a recycled soil conditioner, wherein the total mass of the recycled soil conditioner is 82% of the total mass of the added preliminary soil conditioner, and the acidified soil accounts for 6 wt% of the recycled soil conditioner;

[0040] S5. Slurry preparation: Mix the activated gangue particles prepared in step S1 with fly ash, cement, starch binder, aluminum powder, and the recycled soil conditioner in step S4, add water, and continue ultrasonic stirring for 1.5 hours at a power of 600 W to obtain a preliminary slurry, wherein the weight ratio of the activated gangue particles to water, fly ash, cement, starch binder, aluminum powder, and recycled soil conditioner is 1000:700:25:45:6:0.8:450, wherein the recycled soil conditioner is the recycled soil conditioner recovered in all steps S4;

[0041] S6. Curing: The preliminary slurry prepared in step S5 is placed in a mold and cured at a constant temperature for 11 hours. After demolding, the slurry is dried and crushed to obtain a slow-release acidified soil conditioner. The curing temperature is 58° C. The particle size of the crushed slow-release acidified soil conditioner is 2.5 mm.

[0042] S7, deep soil treatment: evenly distribute all the slow-release acidified soil conditioner in step S6 and apply it to the acidified soil that has been preliminarily treated in step S3.

[0043] Example 2

[0044] The difference between this embodiment and embodiment 1 is that the specific parameters of step S1, the pretreatment of coal gangue, are different.

[0045] S1. Gangue pretreatment: The gangue raw material is ball-milled and then sieved through a 100-mesh sieve to obtain gangue particles. The gangue particles are frozen at -10°C for 4 hours, taken out and heated at 230°C for 15 minutes to obtain activated gangue particles.

[0046] Example 3

[0047] The difference between this embodiment and embodiment 1 is that the specific parameters of step S1, the pretreatment of coal gangue, are different.

[0048] S1. Gangue pretreatment: The gangue raw material is ball-milled and then sieved through a 140-mesh sieve to obtain gangue particles. The gangue particles are frozen at -6°C for 5 hours, taken out and heated at 240°C for 10 minutes to obtain activated gangue particles.

[0049] Note: The parameter adjustments in Examples 1 to 3 are conventional adjustments within a reasonable range. When a lower freezing temperature is selected, the freezing time is appropriately shortened. When a higher heating temperature is selected, the heating time is appropriately reduced, and vice versa.

[0050] Example 4

[0051] The difference between this embodiment and embodiment 1 is that the specific parameters of step S2, humic acid preparation, are different.

[0052] S2, humic acid preparation: the activated gangue particles prepared in step S1 are mixed with nitric acid solution, the mass fraction of the nitric acid solution is 10%, the weight ratio of the nitric acid solution to the activated gangue particles is 1:4, and the mixture is stirred for 0.5h to obtain pre-oxidized gangue particles. The pre-oxidized gangue particles are taken out and mixed with a strong alkaline solution, the mass fraction of the strong alkaline solution is 10%, and the solute of the strong alkaline solution is sodium pyrophosphate and sodium hydroxide mixed in a weight ratio of 1:1, wherein the mass concentration of the pre-oxidized gangue particles is 12g / L, and the reaction temperature is controlled. The temperature is 95°C, the reaction is stirred for 1.5 hours, and the supernatant is collected by centrifugation after cooling to room temperature. Hydrochloric acid solution is added to the supernatant to make up the volume, and the mixture is precipitated, centrifuged, washed, and dried in sequence to obtain humic acid powder; wherein the stirring rate is 60 rpm, the room temperature is 25°C, the centrifugal speed is 5000 rpm, the molar concentration of the hydrochloric acid solution is 2 mol / L, the amount of hydrochloric acid solution added is 100% of the total amount of the pre-oxidized coal gangue particles and the strong alkaline solution, the washing is performed three times with anhydrous ethanol, the drying temperature is 70°C, and the drying time is 1 hour.

[0053] Example 5

[0054] The difference between this embodiment and embodiment 1 is that the specific parameters of step S2, humic acid preparation, are different.

[0055] S2, humic acid preparation: the activated gangue particles prepared in step S1 are mixed with nitric acid solution, the mass fraction of the nitric acid solution is 10%, and the weight ratio of the nitric acid solution to the activated gangue particles is 1:5, and the mixture is stirred for 1 hour to obtain pre-oxidized gangue particles. The pre-oxidized gangue particles are taken out and mixed with a strong alkaline solution, the mass fraction of the strong alkaline solution is 10%, and the solute of the strong alkaline solution is sodium pyrophosphate and sodium hydroxide mixed in a weight ratio of 1:1, wherein the mass concentration of the pre-oxidized gangue particles is 15g / L, and the reaction temperature is controlled. The temperature is 105°C, the reaction is stirred for 2 hours, and the supernatant is collected by centrifugation after cooling to room temperature. Hydrochloric acid solution is added to the supernatant to make up the volume, and the mixture is precipitated, centrifuged, washed, and dried in sequence to obtain humic acid powder; wherein the stirring rate is 80 rpm, the room temperature is 27°C, the centrifugal speed is 8000 rpm, the molar concentration of the hydrochloric acid solution is 1 mol / L, the amount of hydrochloric acid solution added is 150% of the total amount of the pre-oxidized coal gangue particles and the strong alkaline solution, the washing is performed three times with anhydrous ethanol, the drying temperature is 60°C, and the drying time is 2 hours.

[0056] Example 6

[0057] This embodiment differs from embodiment 1 in that:

[0058] S3, preliminary soil treatment: the humic acid powder prepared in step S2 is mixed with biochar in a weight ratio of 1:1, where the biochar is straw biochar, to obtain a preliminary soil conditioner, which is added to the acidified soil to be treated in an amount of 80 kg / mu, and the soil moisture content is controlled to 30% for 7 days;

[0059] S4, recycling treatment: Recover the mixture of the preliminary soil conditioner and part of the acidified soil in step S3 as recycled soil conditioner, wherein the total mass of the recycled soil conditioner is 80% of the total mass of the added preliminary soil conditioner, and the acidified soil accounts for 5wt% of the recycled soil conditioner.

[0060] Example 7

[0061] This embodiment differs from embodiment 1 in that:

[0062] S3, preliminary soil treatment: the humic acid powder prepared in step S2 is mixed with biochar in a weight ratio of 1:1, where the biochar is straw biochar, to obtain a preliminary soil conditioner, which is added to the acidified soil to be treated in an amount of 120 kg / mu, and the soil moisture content is controlled to 35% for 10 days;

[0063] S4. Reuse treatment: Recover the mixture of the preliminary soil conditioner and part of the acidified soil in step S3 as a recycled soil conditioner, wherein the total mass of the recycled soil conditioner is 85% of the total mass of the added preliminary soil conditioner, and the acidified soil accounts for 8 wt % of the recycled soil conditioner.

[0064] Example 8

[0065] This embodiment differs from embodiment 1 in that:

[0066] S5. Slurry preparation: Mix the activated gangue particles prepared in step S1 with fly ash, cement, starch binder, aluminum powder, and the recycled soil conditioner prepared in step S4, add water, and continue ultrasonic stirring for 1 hour at an ultrasonic stirring power of 500 W to obtain a preliminary slurry, wherein the weight ratio of the activated gangue particles to water, fly ash, cement, starch binder, aluminum powder, and recycled soil conditioner is: 1000:600:20:40:5:0.5:400;

[0067] S6. Curing: The preliminary slurry prepared in step S5 is placed in a mold and cured at a constant temperature for 10 hours. After demolding, the slurry is dried and crushed to obtain a slow-release acidified soil conditioner. The curing temperature is 55° C. The particle size of the crushed slow-release acidified soil conditioner is 1 mm.

[0068] Example 9

[0069] This embodiment differs from embodiment 1 in that:

[0070] S5. Slurry preparation: Mix the activated gangue particles prepared in step S1 with fly ash, cement, starch binder, aluminum powder, and the recycled soil conditioner prepared in step S4, add water, and continue ultrasonic stirring for 2 hours at an ultrasonic stirring power of 800 W to obtain a preliminary slurry, wherein the weight ratio of the activated gangue particles to water, fly ash, cement, starch binder, aluminum powder, and recycled soil conditioner is 1000:800:30:50:8:1:500;

[0071] S6. Curing: The preliminary slurry prepared in step S5 is placed in a mold and cured at a constant temperature for 12 hours. After demolding, the slurry is dried and crushed to obtain a slow-release acidified soil conditioner. The curing temperature is 60° C. The particle size of the crushed slow-release acidified soil conditioner is 2 mm.

[0072] Example 10

[0073] This embodiment differs from embodiment 1 in that:

[0074] The weight ratio of activated coal gangue particles to water, fly ash, cement, starch binder, aluminum powder and recycled soil conditioner is: 1000:800:20:50:5:1:500.

[0075] Example 11

[0076] This embodiment differs from embodiment 1 in that:

[0077] The weight ratio of activated coal gangue particles to water, fly ash, cement, starch binder, aluminum powder and recycled soil conditioner is: 1000:600:30:40:8:0.5:400.

[0078] Note: The ratio of activated gangue particles to other components mainly affects its buffering capacity for nutrients and trace elements in the soil. The higher the proportion of activated gangue particles, the stronger its buffering capacity, which improves the nutrient retention rate in the soil and improves the soil structure. Other components can be selected within the parameter range given in the present invention.

[0079] Example 12

[0080] This embodiment differs from embodiment 1 in that:

[0081] In step S7, the slow-release acidified soil conditioner in step S6 is applied to the acidified soil at an application rate of 225 kg / mu.

[0082] Example 13

[0083] In step S7, the slow-release acidified soil conditioner in step S6 is applied to the acidified soil at an application rate of 200 kg / mu.

[0084] Example 14

[0085] In step S7, the slow-release acidified soil conditioner in step S6 is applied to the acidified soil at an application rate of 300 kg / mu.

[0086] Experimental example

[0087] Next, we study the actual use effect of the slow-release acidified soil conditioner of the present invention in acidified soil, mainly studying and analyzing its effect on the pH change of the acidified soil, the plant emergence rate of the cultivated plants, and the heavy metal content in the cultivated plants, and comparing them with the comparative examples. Among them, Comparative Example 1 is the use of humic acid prepared by the present invention alone, Comparative Example 2 is the use of straw biochar alone, Comparative Example 3 is the use of humic acid prepared by the present invention and straw biochar in a 1:1 mixture, Comparative Examples 1 to 3 use the improvement method in Example 1, and Comparative Example 4 is the acidified soil without adding any soil conditioner. The results are shown in Table 1.

[0088] Table 1 Effects of soil conditioners in each case

[0089]

[0090] As can be seen from the data in the above table, after applying the soil conditioner in Example 1 of the present invention, the pH value in the soil can be effectively improved, thereby indirectly achieving the effect of increasing crop yield, which has obvious advantages compared to each comparative example. This also shows that the soil conditioner in Example 1 of the present invention combined with the in-situ secondary application method in Example 1 can effectively improve the soil pH and alleviate the problem of soil acidification;

[0091] The test method for the content of heavy metal elements in plants is as follows: first weigh 0.1g of plant sample, add 5mL of nitric acid solution and perform microwave digestion, transfer to a 25mL volumetric flask to make up the volume, and finally filter with a 0.45μm microporous filter membrane and analyze using ICP-OES. By comparison, it can be found that after applying the soil conditioner in Example 1 of the present invention, the plant emergence rate can be effectively improved. This may be because the complex porous structure of the conditioner in the soil after the second application has stronger water and heat retention, and at the same time has strong fixation for organic matter and nutrients in the soil, which is also not available in the various comparative examples.

[0092] Finally, the content of heavy metal Cr in plants also clearly reflects that the soil conditioner in Example 1 of the present invention has a certain passivation effect on heavy metals in acidified soil. At the same time, the amount of heavy metal dissolution contained in the raw materials of the soil conditioner in Example 1 of the present invention is very small, which meets the national standards.

Claims

1. A method for improving acidified soil based on a slow-release soil conditioner, characterized in that: The following steps are involved: S1. Gangue pretreatment: The gangue raw material is ball-milled and then sieved through a 100-140 mesh sieve to obtain gangue particles. The gangue particles are frozen at -10--6°C for 4-5 hours, taken out, and heated at 230-240°C for 10-15 minutes to obtain activated gangue particles. S2. Preparation of humic acid: The activated gangue particles prepared in step S1 are mixed with a nitric acid solution, stirred and reacted for 0.5 to 1 hour to obtain pre-oxidized gangue particles. The pre-oxidized gangue particles are taken out and mixed with a strong alkaline solution, wherein the mass concentration of the pre-oxidized gangue particles is 12 to 15 g / L. The reaction temperature is controlled to be 100±5°C, and the reaction is stirred and reacted for 1.5 to 2 hours. After cooling to room temperature, the supernatant is collected by centrifugation, and a hydrochloric acid solution is added to the supernatant to make up the volume. The humic acid powder is obtained after precipitation, centrifugation, washing, and drying. S3, preliminary soil treatment: the humic acid powder prepared in step S2 is mixed with biochar in a weight ratio of 1:1 to obtain a preliminary soil conditioner, and the preliminary soil conditioner is added to the acidified soil to be treated in an amount of 80-120 kg / mu, and the soil moisture content is controlled to 30-35% for 7-10 days; S4, recycling treatment: recovering a mixture of part of the preliminary soil conditioner and part of the acidified soil in step S3 as a recycled soil conditioner; S5. Slurry preparation: mixing the activated gangue particles prepared in step S1 with fly ash, cement, starch binder, aluminum powder, and the recycled soil conditioner in step S4, adding water, and continuously stirring and mixing with ultrasonic stirring for 1-2 hours to obtain a preliminary slurry, wherein the weight ratio of the activated gangue particles to water, fly ash, cement, starch binder, aluminum powder, and recycled soil conditioner is: 1000: 600-800: 20-30: 40-50: 5-8: 0.5-1: 400-500, wherein the recycled soil conditioner is the recycled soil conditioner recovered in all steps S4; S6, curing: placing the preliminary slurry prepared in step S5 in a mold and curing at a constant temperature for 10 to 12 hours, and drying and crushing after demoulding to obtain a slow-release acidified soil conditioner; S7, deep soil treatment: evenly distribute all the slow-release acidified soil conditioner in step S6 and apply it to the acidified soil that has been preliminarily treated in step S3.

2. The method for improving acidified soil based on a slow-release improver according to claim 1, characterized in that: The mass fraction of the nitric acid solution in step S2 is 10%, and the weight ratio of the nitric acid solution to the activated coal gangue particles is 1:4-5.

3. The method for improving acidified soil based on a slow-release modifier according to claim 1, characterized in that: The mass fraction of the strong alkaline solution in step S2 is 10%, and the solute of the strong alkaline solution is a mixture of sodium pyrophosphate and sodium hydroxide in a weight ratio of 1:

1.

4. The method for improving acidified soil based on a slow-release conditioner according to claim 1, characterized in that: In step S2, the stirring rate is 60-80 rpm, the room temperature is 25-27° C., the centrifugal speed is 5000-8000 rpm, the molar concentration of the hydrochloric acid solution is 1-2 mol / L, the amount of hydrochloric acid solution added is 100-150% of the total amount of the pre-oxidized coal gangue particles and the strong alkaline solution, the washing is performed three times with anhydrous ethanol, the drying temperature is 60-70° C., and the drying time is 1-2 h.

5. The method for improving acidified soil based on a slow-release improver according to claim 1, characterized in that: The biomass charcoal in step S3 is straw biomass charcoal or rice husk biomass charcoal.

6. The method for improving acidified soil based on a slow-release soil conditioner according to claim 1, characterized in that: The total mass of the recycled soil conditioner in step S4 is 80-85% of the total mass of the added preliminary soil conditioner, and the proportion of acidified soil in the recycled soil conditioner does not exceed 10 wt %.

7. The method for improving acidified soil based on a slow-release improver according to claim 1, characterized in that: The ultrasonic stirring power in step S5 is 500-800W.

8. The method for improving acidified soil based on a slow-release improver according to claim 1, characterized in that: The curing temperature in step S6 is 55-60° C., and the particle size of the crushed slow-release acidified soil conditioner is less than 3 mm.

9. The method for improving acidified soil based on a slow-release soil conditioner according to claim 1, characterized in that: In step S7, the slow-release acidified soil conditioner in step S6 is applied to the acidified soil in an amount of 200-300 kg / mu.

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