Method for preparing mineral soil from steel-covered blast furnace tailings for modifying saline-alkali soil and treating desertification

Abstract

The invention relates to a method for preparing mineral soil from steel-clad blast furnace tailings for modifying saline-alkali soil and treating desertification, which comprises the following steps: crushing the steel-clad blast furnace tailings until the particle size is 100-200 meshes, and separating ferromagnetic substances through magnetic separation; silicate impurities are removed through flotation, and harmful heavy metals such as lead and cadmium are selectively adsorbed through an ion exchange method; the residual mineral powder contains sulfur, calcium, phosphorus and potassium; the mineral powder and the organic fertilizer are mixed according to the weight ratio of 1: 0.8-1: 2, the saline-alkali soil formula focuses on calcium / sulfur, and the desertification formula increases phosphorus / potassium; 0.1%-0.5% of lanthanum nitrate / cerium nitrate rare earth solution is added, so that the enzyme activity of the soil is improved. According to the method for preparing the mineral soil from the steel-clad blast furnace tailings for modifying the saline-alkali soil and treating desertification, the steel-clad blast furnace tailings and other industrial solid wastes are effectively utilized, environmental pollution is reduced, the fertility of the improved soil is high, the improved soil is suitable for planting Chinese herbal medicines and crops, and green organic planting is achieved by improving the soil and reducing dependence on chemical fertilizers and pesticides; waste is turned into wealth, the soil improvement cost is reduced, and the crop yield and quality are improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of comprehensive resource utilization, soil improvement and agricultural sustainable development, and specifically provides a method for preparing mineral soil from Baotou Steel's blast furnace slag for the improvement of saline-alkali land and the treatment of desertification. Background Art

[0002] With the rapid development of industrialization, a large amount of blast furnace slag from Baotou Steel and other solid wastes generated by the steel industry have caused serious pressure on the environment. At the same time, the large areas of saline-alkali land and desertified land in China have severely restricted the development of agriculture and the improvement of the ecological environment.

[0003] Currently, solid wastes such as blast furnace slag from Baotou Steel in the steel industry contain heavy metal elements, and long-term stacking is likely to cause environmental pollution. On the other hand, the saline-alkali land and desertified land in China cover hundreds of millions of mu. Traditional improvement methods rely on chemical fertilizers, which are prone to cause soil compaction, fertility degradation and secondary salinization. In the existing technology, solid waste treatment mostly focuses on metal recovery, while ignoring its potential for resource utilization in soil improvement; soil remediation technology lacks a systematic plan for collaborative treatment with solid waste. Therefore, there is an urgent need for a method for preparing mineral soil from Baotou Steel's blast furnace slag for the improvement of saline-alkali land and the treatment of desertification to solve the contradiction between environmental governance and agricultural development. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the present invention provides a method for preparing mineral soil from Baotou Steel's blast furnace slag for the improvement of saline-alkali land and the treatment of desertification, which has the advantages of effectively utilizing industrial solid waste, reducing environmental pollution, improving saline-alkali land and desertified soil, increasing soil fertility, reducing the dependence on chemical fertilizers and pesticides, and realizing green organic planting, etc., and solves the problems that traditional improvement methods rely on chemical fertilizers, are prone to cause soil compaction, fertility degradation and secondary salinization. In the existing technology, solid waste treatment mostly focuses on metal recovery, while ignoring its potential for resource utilization in soil improvement; soil remediation technology lacks a systematic plan for collaborative treatment with solid waste.

[0005] To achieve the above object, the present invention provides the following technical solution: A method for preparing mineral soil from Baotou Steel's blast furnace slag for the improvement of saline-alkali land and the treatment of desertification, comprising the following steps:

[0006] Step 1: Pretreatment of solid waste and extraction of heavy metals

[0007] 1) Crush the blast furnace slag of Baotou Steel to a particle size of 100-200 mesh, and separate ferromagnetic substances by magnetic separation;

[0008] 2) Remove silicate impurities by flotation, and selectively adsorb harmful heavy metals such as lead and cadmium by ion exchange method;

[0009] 3) The remaining mineral powder contains sulfur, calcium, phosphorus and potassium;

[0010] Step 2: Preparation of soil conditioner

[0011] 1) Mix the mineral powder and organic fertilizer in a weight ratio of 1:0.8 - 1:2. For the saline-alkali land formula, the emphasis is on calcium / sulfur, and for the desertification formula, the phosphorus / potassium is increased;

[0012] 2) Add 0.1% - 0.5% lanthanum / cerium rare earth nitrate solution to enhance soil enzyme activity;

[0013] Step 3: Soil improvement method

[0014] 1) Spread the conditioner evenly at 3000 - 5000 kg / mu and deeply plow the soil to 25 - 35 cm;

[0015] 2) According to the initial pH value, add humic acid (1 - 2 kg / mu) to assist in neutralizing alkalinity;

[0016] 3) Supplement with slow-release nitrogen fertilizer (urea, 50 - 100 kg / mu) at the initial stage of planting to avoid nutrient imbalance;

[0017] Step 4: Quality control and monitoring

[0018] 1) The heavy metal residue in the improved soil should meet the "Soil Environmental Quality - Agricultural Land Standard" (GB15618 - 2018);

[0019] 2) Continuously monitor for 3 years that the soil organic matter content increases by ≥30% and the crop yield increases by 20% - 40%.

[0020] Furthermore, in the crushing step, the crushing particle size of the BF slag from Baotou Steel is controlled at 150 - 200 mesh, the magnetic separation magnetic field intensity is 0.8 - 1.2 Tesla, sodium dodecyl sulfonate is used as the collector in flotation, the ion exchange resin is sulfonic acid type strongly acidic cation exchange resin. In the ion exchange step, two-stage series ion exchange columns are used. The first stage is for adsorbing lead ions, the second stage is for adsorbing cadmium ions, and the regeneration period of the exchange column is 10 - 15 batches.

[0021] Furthermore, the sulfur content in the remaining mineral powder is 15% - 20%, the calcium content is 10% - 18%, the phosphorus content is 5% - 8%, the potassium content is 3% - 5%, and the heavy metal lead and cadmium residues are both lower than the limits specified in the "Soil Environmental Quality - Agricultural Land Standard" (GB15618 - 2018).

[0022] Furthermore, the dynamic ratio in the preparation of the soil conditioner is that the ratio of mineral powder to organic fertilizer in the saline-alkali land formula is 1:1, and in the desertification formula is 1:1.5. When used for desertified land, 0.5% - 1.0% of water retaining agent needs to be incorporated into the conditioner, and the water retaining agent is polyacrylamide or starch graft copolymer.

[0023] Further, in the preparation of the soil conditioner, the rare earth solution elements are a mixture of lanthanum nitrate and cerium nitrate, and the mass ratio of the two is 1:1 to 3:1, and the total addition amount is 0.1%-0.5%.

[0024] Further, in the process of preparing the soil conditioner, 0.05%-0.1% of compound microbial inoculant is additionally added. The inoculant includes Bacillus subtilis, phosphate-solubilizing bacteria and nitrogen-fixing bacteria, and the viable bacteria amount is 1×10 8 CFU / g. After the soil conditioner is applied, salt-tolerant pioneer plants or leguminous plants are preferably planted to accelerate the repair of soil structure.

[0025] Further, in the soil improvement method, for severely saline-alkali land with pH≥9.0, 1-2 kg / mu of humic acid is additionally added to the conditioner and applied in two times with an interval of 3-6 months.

[0026] Further, the improved soil needs to meet the following physical and chemical indexes:

[0027] The organic matter content ≥2.0%;

[0028] The cation exchange capacity (CEC) ≥15 cmol(+) / kg;

[0029] The soil bulk density ≤1.3 g / cm 3 ;

[0030] The water holding capacity is increased by ≥30%.

[0031] Further, in the deep plowing step, the plowing depth is 25-35 cm, and at least one irrigation is required after plowing, and the irrigation water volume is 30-50 cubic meters per mu to promote the fusion of the conditioner and the soil.

[0032] Compared with the prior art, the technical solution of the present application has the following beneficial effects:

[0033] 1. The method for using Baotou Iron and Steel blast furnace slag to prepare mineral soil for transforming saline-alkali land and controlling desertification effectively utilizes Baotou Iron and Steel blast furnace slag and other industrial solid wastes, reduces environmental pollution, the improved soil has high fertility, is suitable for planting Chinese herbal medicines and crops, reduces the dependence on chemical fertilizers and pesticides by improving the soil, realizes green and organic planting, turns waste into treasure, reduces the soil improvement cost, and improves the yield and quality of crops.

[0034] 2. The method for preparing mineral soil from the tail slag of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification uses a multi-stage combined process of "crushing - magnetic separation - flotation - ion exchange" to accurately separate harmful elements for plants such as lead and cadmium, recover valuable metals such as iron and zinc, dynamically adjust the ratio of mineral powder to organic fertilizer according to the soil type (saline-alkali land / desertification), and introduce rare earth elements (0.1%-0.5%) to enhance the activity of soil microorganisms. Minerals such as sulfur and calcium in the modifier and organic matter act synergistically to neutralize soil alkalinity and improve water and fertilizer retention capacity, and the fertility can last for more than 20 years. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the method for preparing mineral soil from the tail slag of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification according to the present invention;

[0036] Figure 2 It is a flow chart of the solid waste pretreatment and heavy metal extraction according to the present invention;

[0037] Figure 3 It is a flow chart of the soil improvement method according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0039] Embodiment 1

[0040] Please refer to Figures 1-3 , a method for preparing mineral soil from the tail slag of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification in this embodiment is characterized by including the following steps:

[0041] Step 1. Solid waste pretreatment and heavy metal extraction

[0042] 1) The crushing particle size of the tail slag of Baotou Steel's blast furnace is controlled at 200 mesh;

[0043] 2) The magnetic separation magnetic field intensity is 1.2 Tesla, sodium dodecyl sulfonate is used as a collector for flotation, the ion exchange resin is a sulfonic acid type strongly acidic cation exchange resin, two-stage series ion exchange columns are used, the first stage is for adsorbing lead ions, the second stage is for adsorbing cadmium ions, and the regeneration period of the exchange column is 10 - 15 batches;

[0044] 3) The sulfur content in the remaining mineral powder is 20%, the calcium content is 18%, the phosphorus content is 8%, the potassium content is 5%, and the residual amounts of heavy metals lead and cadmium are both lower than the limits specified in the "Soil Environmental Quality - Agricultural Land Standard" (GB 15618-2018).

[0045] Step Two: Preparation of Soil Conditioner

[0046] 1) The mineral powder and organic fertilizer are mixed at a weight ratio of 1:2. The saline-alkali land formula focuses on calcium / sulfur, and the desertification formula increases phosphorus / potassium. The dynamic ratio is that the mineral powder:organic fertilizer in the saline-alkali land formula is 1:1, and the mineral powder:organic fertilizer in the desertification formula is 1:1.5. When used for desertified land, 1.0% of a water-retaining agent needs to be incorporated into the conditioner. The water-retaining agent is polyacrylamide or starch graft copolymer;

[0047] 2) Add 0.5% of lanthanum / cerium rare earth solution to enhance soil enzyme activity. The elements in the rare earth solution are a mixture of lanthanum nitrate and cerium nitrate, and the mass ratio of the two is 3:1, with a total addition amount of 0.5%;

[0048] 3) Additionally add 0.1% of a compound microbial inoculant. The inoculant contains Bacillus subtilis, phosphate-solubilizing bacteria, and nitrogen-fixing bacteria, and the viable bacteria count is 1×10 8 CFU / g. After applying the soil conditioner, pioneer plants resistant to saline-alkali or leguminous plants should be preferentially planted to accelerate the repair of soil structure;

[0049] Step Three: Soil Improvement Method

[0050] 1) Spread the conditioner evenly at 5000 kg / mu and deeply plow the soil by 35 cm. In the deep plowing step, the plowing depth is 35 cm. After plowing, at least one irrigation is required, and the irrigation water volume is 50 cubic meters per mu to promote the integration of the conditioner and the soil;

[0051] 2) According to the initial pH value, add humic acid (2 kg / mu) to assist in neutralizing alkalinity;

[0052] 3) Supplement with slow-release nitrogen fertilizer (100 kg / mu of urea) at the initial stage of planting to avoid nutrient imbalance;

[0053] 4) For severely saline-alkali land with a pH of 9.0, an additional 2 kg / mu of humic acid is added to the conditioner and applied in two batches with an interval of 6 months

[0054] Step Four: Quality Control and Monitoring

[0055] 1) The heavy metal residues in the improved soil should meet the "Soil Environmental Quality - Agricultural Land Standard" (GB 15618-2018);

[0056] 2) Continuously monitor for 3 years to ensure that the soil organic matter content increases by 30% and the crop yield increases by 40%.

[0057] Example 2

[0058] Please refer to Figures 1-3 , a method for preparing mineral soil from the tailings of Baotou Steel's blast furnace for the improvement of saline-alkali land and the treatment of desertification in this embodiment, is characterized in that it includes the following steps:

[0059] Step 1: Solid waste pretreatment and heavy metal extraction

[0060] 1) The crushing particle size of the tailings of Baotou Steel's blast furnace is controlled at 150 mesh;

[0061] 2) The magnetic separation magnetic field strength is 0.8 Tesla. Sodium dodecyl sulfonate is used as a collector in flotation. The ion exchange resin is a sulfonic acid type strong acidic cation exchange resin. Two-stage series ion exchange columns are used. The first stage is used to adsorb lead ions, and the second stage is used to adsorb cadmium ions. The regeneration period of the exchange column is 10 batches;

[0062] 3) The sulfur content in the remaining ore powder is 15%, the calcium content is 10%, the phosphorus content is 5%, the potassium content is 3%, and the residual amounts of heavy metals lead and cadmium are both lower than the limits specified in the "Soil Environmental Quality Standard for Agricultural Land" (GB15618-2018);

[0063] Step 2: Preparation of soil conditioner

[0064] 1) The ore powder and organic fertilizer are mixed at a weight ratio of 1:0.8. The saline-alkali land formula focuses on calcium / sulfur, and the desertification formula increases phosphorus / potassium. The dynamic ratio is that the ore powder:organic fertilizer in the saline-alkali land formula is 1:1, and the ore powder:organic fertilizer in the desertification formula is 1:1.5. When used for desertified land, 0.5% of a water-retaining agent needs to be incorporated into the conditioner. The water-retaining agent is polyacrylamide or starch graft copolymer;

[0065] 2) Add 0.1% of lanthanum / cerium rare earth nitrate solution to improve soil enzyme activity. The rare earth solution elements are a mixture of lanthanum nitrate and cerium nitrate, and the mass ratio of the two is 1:1, and the total addition amount is 0.1%;

[0066] 3) An additional 0.05% of a composite microbial agent is added. The agent contains Bacillus subtilis, phosphorus-solubilizing bacteria, and nitrogen-fixing bacteria, and the viable bacteria amount is 1×10 8 CFU / g. After the soil conditioner is applied, salt-tolerant pioneer plants or leguminous plants are preferably planted first to accelerate the repair of the soil structure;

[0067] Step 3: Soil improvement method

[0068] 1) The conditioner is evenly spread at 3000 kg / mu, and the soil is deeply plowed and turned over by 25 cm. In the step of deep plowing and turning over the soil, the turning depth is 25 cm. After turning over the soil, at least one irrigation is required, and the irrigation water volume is 30 cubic meters per mu to promote the integration of the conditioner and the soil;

[0069] 2) According to the initial pH value, add humic acid (1 kg / mu) to assist in neutralizing alkalinity;

[0070] 3) At the initial stage of planting, slow-release nitrogen fertilizer (50 kg / mu of urea) is supplemented to avoid nutrient imbalance;

[0071] 4) For severely saline-alkali land with a pH of 8.5, an additional 1 kg / mu of humic acid is added to the modifier and applied in two times with an interval of 3 months

[0072] Step Four: Quality Control and Monitoring

[0073] 1) The heavy metal residue in the soil after improvement shall comply with the "Soil Environmental Quality - Agricultural Land Standard" (GB 15618-2018);

[0074] 2) Continuously monitor for 3 years that the soil organic matter content increases by 27% and the crop yield increases by 20%.

[0075] Specifically, the soil after improvement shall meet the following physical and chemical indexes:

[0076] Organic matter content ≥ 2.0%;

[0077] Cation exchange capacity (CEC) ≥ 15 cmol(+) / kg;

[0078] Soil bulk density ≤ 1.3 g / cm 3 ;

[0079] Water holding capacity increase ≥ 30%.

[0080] Experimental Example 1: Saline-alkali Land Improvement

[0081] Raw materials: BF slag of Baotou Steel, crushed to 180 meshes, after magnetic separation - flotation - ion exchange, sulfur (18%) and calcium (15%) ore powder are obtained;

[0082] Modifier formula: ore powder: organic fertilizer = 1:1, adding 0.3% lanthanum nitrate;

[0083] Application: 4000 kg / mu, deep plowing 30 cm, supplemented with 1.5 kg / mu of humic acid;

[0084] Effect: After 1 year, the soil pH drops from 9.2 to 7.8, and the corn yield increases by 35%.

[0085] Experimental Example 2: Desertified Soil Improvement

[0086] Formula: ore powder (phosphorus 8%, potassium 5%): organic fertilizer = 1:1.5, adding 0.2% cerium nitrate;

[0087] Application: 5000 kg / mu, deep plowing 25 cm;

[0088] Effect: After 2 years, the soil water holding capacity increased by 50%, and the survival rate of sea buckthorn increased to 85%.

[0089] Experimental Example 3: Verification of Adaptability from Different Solid Waste Sources

[0090] Raw materials: Blast furnace slag from Angang and Baotou Steel (composition: sulfur 12%, calcium 10%, phosphorus 6%, iron 8%); blast furnace slag from WISCO and Baotou Steel (sulfur 16%, calcium 14%, phosphorus 7%, zinc 2%);

[0091] Treatment process: Crush to 200 mesh, magnetic separation (1.0 Tesla) to recover iron / zinc, flotation (collector sodium dodecyl sulfate) to remove silicate, and ion exchange (sulfonic acid resin) to adsorb lead (residual amount < 2 mg / kg) and cadmium (< 0.5 mg / kg);

[0092] Amendment formula: Mineral powder: Organic fertilizer = 1:1, add 0.3% lanthanum nitrate;

[0093] Application scenario: Moderately saline-alkali land in North China (pH 8.5 - 9.0);

[0094] Effect:

[0095] Amendment with Angang slag: After 1 year, the soil organic matter increased from 1.2% to 2.5%, and the wheat yield increased by 28%;

[0096] Amendment with WISCO slag: Zinc element promoted the stress resistance of crops, and the cotton yield increased by 32%.

[0097] Experimental Example 4: Improvement of Extreme Saline-alkali Land (pH ≥ 9.5)

[0098] Raw materials: Blast furnace slag from Baotou Steel, with lead residue < 1 mg / kg after ion exchange;

[0099] Amendment formula: Mineral powder: Organic fertilizer = 1:1, add 0.5% cerium nitrate + 2 kg / mu of humic acid;

[0100] Application: Apply in two times (interval of 4 months), total amount 5000 kg / mu, deep plowing 35 cm;

[0101] Effect:

[0102] Phase 1: After 6 months, the pH decreased from 9.6 to 8.3, and the salt content decreased by 40%;

[0103] Phase 2: After 12 months, plant the salt-tolerant crop Suaeda glauca, and the coverage rate increased from 10% to 75%;

[0104] After 3 years, corn can be rotated, and the yield reaches 80% of that of conventional farmland.

[0105] Experimental Example 5: Long-term Fertility Tracking Experiment

[0106] Amendment: Mineral powder (sulfur 18%, calcium 15%): organic fertilizer = 1:1, adding 0.2% lanthanum nitrate + 0.05% compound microbial agent (Bacillus subtilis 1×10 8 CFU / g);

[0107] Application: In the desertified land of Inner Mongolia, apply 4000 kg / mu at one time and plow deeply by 30 cm;

[0108] Monitoring results:

[0109] In the first year: The soil water holding capacity increased from 15% to 45%, and the survival rate of seabuckthorn was 65%;

[0110] In the third year: The organic matter stabilized at 2.8%, the root depth of seabuckthorn increased by 50%, and a stable vegetation layer was formed;

[0111] In the fifth year: No additional chemical fertilizer was needed, and the soil bulk density decreased from 1.5 g / cm 3 to 1.25 g / cm 3 , and the fertility remained stable

[0112] In summary, the method for preparing mineral soil from Baotou blast furnace slag for transforming saline-alkali land and controlling desertification, through the multi-stage combined process of "crushing - magnetic separation - flotation - ion exchange", accurately separates harmful elements to plants such as lead and cadmium, recovers valuable metals such as iron and zinc, dynamically adjusts the ratio of mineral powder to organic fertilizer according to the soil type (saline-alkali land / desertification), and introduces rare earth elements (0.1% - 0.5%) to enhance the activity of soil microorganisms. The sulfur, calcium and other minerals in the amendment and the organic matter act synergistically to neutralize the soil alkalinity, improve the water and fertilizer retention capacity, and the fertility can be sustained for more than 20 years.

[0113] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent in such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, article or device including the said element.

[0114] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing mineral soil from the tail slag of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification, characterized in that, It includes the following steps: Step 1: Solid waste pretreatment and heavy metal extraction 1) Crush the BF tailings of Baotou Steel to a particle size of 100-200 mesh, and separate ferromagnetic substances by magnetic separation; 2) Remove silicate impurities by flotation, and selectively adsorb harmful heavy metals such as lead and cadmium by ion exchange method; 3) The remaining ore powder contains sulfur, calcium, phosphorus and potassium; Step 2: Preparation of soil conditioner 1) Mix the ore powder and organic fertilizer in a weight ratio of 1:0.8-1:

2. The formula for saline-alkali land focuses on calcium / sulfur, and the formula for desertification land increases phosphorus / potassium; 2) Add 0.1%-0.5% lanthanum / cerium rare earth nitrate solution to enhance soil enzyme activity; Step 3: Soil improvement method 1) Spread the conditioner evenly at 3000-5000 kg / mu, and deeply plow the soil to a depth of 25-35 cm; 2) According to the initial pH value, add humic acid (1-2 kg / mu) to assist in neutralizing alkalinity; 3) Supplement with slow-release nitrogen fertilizer (urea, 50-100 kg / mu) at the initial stage of planting to avoid nutrient imbalance; Step 4: Quality control and monitoring 1) The heavy metal residue in the improved soil should meet the "Soil Environmental Quality Standard for Agricultural Land" (GB15618-2018); 2) Continuously monitor for 3 years that the soil organic matter content increases by ≥30%, and the crop yield increases by 20%-40%.

2. A method for preparing mineral soil using the tailings of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification according to claim 1, characterized in that, In the crushing step, the crushing particle size of the BF tailings of Baotou Steel is controlled at 150-200 mesh, the magnetic separation magnetic field intensity is 0.8-1.2 Tesla, dodecyl sulfonate is used as the collector in flotation, and the ion exchange resin is a sulfonic acid type strong acidic cation exchange resin. In the ion exchange step, two-stage series ion exchange columns are used. The first stage is used to adsorb lead ions, and the second stage is used to adsorb cadmium ions. The regeneration period of the exchange column is 10-15 batches.

3. A method for preparing mineral soil from the tail slag of Baotou Steel's blast furnace for the renovation of saline-alkali land and the treatment of desertification according to claim 1, characterized in that, The sulfur content in the remaining ore powder is 15%-20%, the calcium content is 10%-18%, the phosphorus content is 5%-8%, the potassium content is 3%-5%, and the heavy metal lead and cadmium residues are both lower than the limits specified in the "Soil Environmental Quality Standard for Agricultural Land" (GB15618-2018).

4. A method for preparing mineral soil using the blast furnace slag of Baotou Steel to transform saline-alkali land and control desertification according to claim 1, characterized in that, The dynamic ratio of the soil conditioner preparation is that the ore powder:organic fertilizer in the saline-alkali land formula is 1:1, and the ore powder:organic fertilizer in the desertification land formula is 1:1.

5. When used for desertified land, 0.5%-1.0% of water-retaining agent needs to be incorporated into the conditioner, and the water-retaining agent is polyacrylamide or starch graft copolymer.

5. A method for preparing mineral soil from the BF slag of Baotou Steel for saline-alkali land improvement and desertification control according to claim 1, characterized in that In the preparation of the soil conditioner, the rare earth solution elements are a mixture of lanthanum nitrate and cerium nitrate, and the mass ratio of the two is 1:1 to 3:1, and the total addition amount is 0.1%-0.5%.

6. A method for preparing mineral soil using the tailings of Baotou Steel's blast furnace for saline-alkali land improvement and desertification control according to claim 1, characterized in that, During the preparation of the soil conditioner, an additional 0.05%-0.1% of the compound microbial inoculant is added. The inoculant contains Bacillus subtilis, phosphate-solubilizing bacteria, and nitrogen-fixing bacteria, and the viable bacteria count is 1×10 8 CFU / g. After the soil conditioner is applied, salt-tolerant pioneer plants or leguminous plants are preferably planted to accelerate the repair of the soil structure.

7. A method for preparing mineral soil from the tailings of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification according to claim 1, characterized in that, In the soil improvement method, for severely saline-alkali land with pH≥9.0, an additional 1-2 kg / mu of humic acid is added to the conditioner and applied in two times with an interval of 3-6 months.

8. A method for preparing mineral soil by using the tailings of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification according to claim 1, wherein, The improved soil needs to meet the following physical and chemical indexes: Organic matter content ≥2.0%; Cation exchange capacity (CEC) ≥15 cmol(+) / kg; Soil bulk density ≤ 1.3 g / cm 3 ; Water holding capacity increases by ≥30%.

9. A method for preparing mineral soil from the tailings of Baotou Steel's blast furnace for improving saline-alkali land and controlling desertification according to claim 1, characterized in that, In the deep plowing step, the plowing depth is 25-35 cm, and at least one irrigation is required after plowing. The irrigation water volume is 30-50 cubic meters per mu to promote the integration of the conditioner and the soil.

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