Low-fluorine spongy ardealite-based greening soil material and preparation method thereof

Abstract

The invention discloses a low-fluorine spongy ardealite-based greening soil material and a preparation method thereof, and relates to the technical field of comprehensive utilization of ardealite. Ardealite is adopted; gibbsite, hydromica, Dikjite, halloysite and red clay are used as anion adsorption minerals; a water-soluble phosphate; and then adding organic matters, an environment regulator and an additive. In combination with the characteristics of phosphogypsum, on the basis of rigorous colloid surface chemistry and solution theories, various common and easily available reaction substances and soil forming additives are selected in a targeted manner, and scientific and ordered preparation steps are adopted; the low-fluorine spongy ardealite-based greening soil material which is excellent in structure, large in fertility loading capacity and high in persistence is efficiently obtained at low cost. The problems that in the prior art, the fluorine content is reduced through water washing, the water requirement is large, the cost is high, the period is long, washing water cannot be balanced, secondary water pollution is caused, and beneficial elements are lost are solved, and the problems that in the prior art, soil hardening and low porosity occur when ardealite is adopted for preparing a soil material are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of phosphogypsum, and particularly relates to a low-fluorine sponge-like phosphogypsum-based greening soil material and a preparation method thereof. Background Art

[0002] The comprehensive utilization of phosphogypsum has always been a difficult problem. From statistical data, the global stockpile of phosphogypsum has exceeded 6 billion tons, and it still continues to grow at a rate of about 200 million tons per year, but the comprehensive utilization rate is only about 25%. The annual production of phosphogypsum in China is close to 80 million tons, and the stockpile is 800 million tons, while the utilization rate is less than 45%. The problems of stockpiling and continuous emission of phosphogypsum have become a serious bottleneck restricting the sustainable development of the phosphorus chemical industry. Therefore, it is urgent to broaden the comprehensive utilization of phosphogypsum.

[0003] In terms of mineral composition, particle size distribution, formation process of aggregate structure, soil-forming structure, etc., phosphogypsum is the bulk industrial solid waste closest to natural soil, so it is increasingly used to manufacture soil-like materials. At the same time, phosphogypsum can be used as a source of calcium and sulfur during plant cultivation. By modifying and adjusting and supplementing nutrient elements, it can be used as a soil material for slope revegetation, abandoned mine land reclamation, restoration of degraded forest and grassland, treatment of rocky desertification land and urban landscaping. It is an important path for large-scale consumption of phosphogypsum in the future.

[0004] The existing phosphogypsum artificial soil materials mainly focus on soil fertility and soil reconstruction. Generally speaking, the existing technologies have the following defects and deficiencies:

[0005] Based on the characteristics of the phosphorus chemical industry, phosphogypsum contains a certain amount of fluorine elements, including insoluble and soluble fluorides. In particular, soluble fluorine will have an adverse impact on animals, plants and humans. Although the current greening soil standard does not stipulate the fluorine content, in the application field of phosphogypsum materials, fluorine is an important control factor. Most of the existing technologies do not treat the fluorides in phosphogypsum soil materials, forming potential environmental risks during the application process; or use a simple water washing process. On the one hand, it increases a large amount of costs, and on the other hand, it generates new water pollution in the scenario where the washing water cannot be balanced. On the one hand, other beneficial components such as phosphorus elements are washed away, resulting in waste. At the same time, the existing technologies for preparing soil materials with phosphogypsum are prone to soil compaction, low porosity and other soil structure problems, resulting in poor plant growth adaptability.

[0006] Therefore, it is urgent to develop a phosphogypsum-based greening soil material and a preparation method thereof to treat fluorides and solve the problem of low porosity. Summary of the Invention

[0007] The purpose of the present invention is to provide a low-fluorine sponge-like phosphogypsum-based greening soil material and a preparation method thereof, so as to solve the problems of cumbersome fluorine treatment and low soil porosity in the existing technology.

[0008] To solve the above technical problems, the present invention adopts the following technical solutions: A low-fluorine spongy phosphogypsum-based greening soil material, which is characterized by including the following materials in parts by weight:

[0009] 100 parts of phosphogypsum;

[0010] 5 - 20 parts of anion adsorption minerals;

[0011] 0.01 - 0.1 part of water-soluble phosphate;

[0012] 10 - 25 parts of organic matter;

[0013] 0.05 - 0.2 part of environmental regulator;

[0014] 0.1 - 1 part of additive.

[0015] A further technical solution is that the phosphogypsum is at least one of untreated phosphogypsum and calcined phosphogypsum. The specifically calcined phosphogypsum is that the phosphogypsum is calcined at 100 - 200 °C for 0.5 - 12 h to remove part of the crystal water in the phosphogypsum, forming a material mainly composed of hemihydrate gypsum; or calcined at 650 - 850 °C for 0.5 - 6 h to remove all the crystal water in the phosphogypsum, forming a material mainly composed of anhydrite; or calcined at 350 - 550 °C for 0.5 - 5 h, part of the phosphogypsum removes part of the crystal water and another part of the phosphogypsum removes all the crystal water, forming a material mainly composed of a mixture of hemihydrate gypsum and anhydrite or a so-called composite gypsum.

[0016] A further technical solution is that the anion adsorption mineral is at least one of gibbsite, hydromica, dickite, halloysite, and red soil clay.

[0017] A further technical solution is that the water-soluble phosphate is at least one of calcium hydrogen phosphate and calcium dihydrogen phosphate.

[0018] A further technical solution is that the organic matter is at least one of substrate soil, humus soil, domestic sewage sludge, and river and lake bottom mud. The organic matter is subjected to aerobic fermentation and anaerobic fermentation and composting treatment to make its quality meet the B-level standard in GB 4284-2018.

[0019] A further technical solution is that the environmental regulator is at least one of ammonia water, ammonium carbonate, ammonium bicarbonate, calcium oxide, and calcium hydroxide.

[0020] A further technical solution is that the additive is at least one of plant fibers, multi-element medium and trace element fertilizers, organic acids, and microorganisms. The plant fibers are at least one of straw, rice husk, rice straw, greening waste branches and leaves, tobacco waste branches and leaves, corncob, and waste mushroom bags; the multi-element medium and trace element fertilizers contain at least one of magnesium, iron, manganese, copper, zinc, molybdenum, and boron elements; the organic acids contain at least one of humic acid, fulvic acid, humic acid, humin, fulvic acid, amine fresh ester, brassinolide, gibberellin, polyglutamic acid, and amino acids; the microorganisms include at least one of EM bacteria, Bacillus subtilis, Trichoderma harzianum, Bacillus amyloliquefaciens, Bacillus cereus, Methylotrophic Bacillus, Bacillus licheniformis, and Bacillus megaterium.

[0021] The present invention also discloses a preparation method of a low-fluorine sponge-like phosphogypsum-based greening soil material:

[0022] S1. Mix phosphogypsum with an anion adsorption mineral. First, mix the dry materials evenly, add water and mix again evenly to control the water content of the attached water in the mixed material at 10-20%.

[0023] S2. Let the mixed material stand and age for 3-5 days.

[0024] S3. Mix the aged material in S2 with water-soluble phosphate, organic matter, environmental regulator, and additive again evenly. Control the pH value at 6-8 through the environmental regulator, and age again for 3-5 days to make the pH value drop back to 5.5-7.5 to obtain the target product.

[0025] Reaction mechanism:

[0026] Combined with the self-properties of the phosphogypsum soil material, based on the surface chemical anion adsorption effect of soil colloids and the thermodynamic characteristics such as the extremely low formation enthalpy (about -12500 kJ / mol) of apatite group minerals, the soluble fluoride ions in the soil are fixed on the hydroxylated or hydrated surface of soil minerals through electrostatic adsorption and irreversible ligand exchange adsorption, or react with elements and groups such as calcium, phosphorus, iron, and aluminum in the soil to form insoluble apatite group minerals, greatly reducing the content of soluble fluoride in the phosphogypsum soil. At the same time, a large amount of gas is generated during the reaction and remains inside the gypsum, forming a sponge-like structure with a large internal specific surface area, making the soil material have a large fertility loading capacity and slow and continuous release characteristics. At the same time, a loose, ventilated, and permeable soil structure is constructed to form a low-fluorine, sponge-like phosphogypsum-based greening soil material, which can be used as a vegetation soil in the fields of slope, mine waste land, rocky desertification land restoration and treatment, and landscaping, reducing the environmental risks brought by the large-scale application of phosphogypsum soil.

[0027] Such as Figure 1As shown in the figure, the electrostatic adsorption of fluoride ions by soil colloids is mainly controlled by the electrostatic attraction between cations on the colloid surface and fluoride ions. The present invention mainly involves increasing H + NH 3+ 、Al 3+ 、Fe 3+ The concentration of positively charged cationic groups, such as hydroxyl groups, on the colloid surface allows for the electrostatic adsorption effect to adsorb and fix fluoride ions. By cleverly utilizing the low initial pH of phosphogypsum and the relatively abundant cations on the colloid surface, electrostatic adsorption of fluoride ions occurs. As the reaction proceeds, the system pH gradually increases, the electrostatic adsorption effect slows, and ligand exchange adsorption begins to dominate. Simultaneously, the reaction produces a certain amount of gas, such as CO2, which is retained in the soil material to form through-pores, significantly improving the soil's pore structure.

[0028] The ligand-exchange adsorption of fluoride ions by soil colloids primarily occurs when fluoride ions enter the coordination shells of metal atoms on the colloid surface, coordinate with hydroxyl or hydrated groups therein, and are fixed to the colloid surface via covalent or coordination bonds. This reaction occurs in a neutral environment. This invention exploits the pH rise to a neutral state after the electrostatic adsorption effect is complete. By supplementing adsorption sites and fine-tuning the reaction environment, the ligand-exchange adsorption effect is optimized.

[0029] During the middle and late stages of the adsorption effect, the pH of the system reaches neutral or slightly alkaline, which is just the environment for the precipitation reaction of the fluorapatite family. The present invention, by precisely controlling the mass of the reactants and the reaction conditions, based on the extremely low formation enthalpy of the fluorapatite family, causes fluoride ions to form insoluble precipitates in the middle and late stages of soil material preparation, further reducing the concentration of water-soluble fluorine compounds. During the precipitation reaction and formation process, the pH of the system slowly decreases. Through precise control, the pH of the phosphogypsum soil material is kept in the neutral and slightly acidic range, that is, the pH value is 5.5 to 7.5, ultimately achieving conditions suitable for plant growth.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] This invention combines the inherent properties of phosphogypsum with rigorous colloidal surface chemistry and solution theory, selectively selecting various commonly available reactants and soil-forming additives, and adopting a scientific and orderly preparation process to efficiently and cost-effectively produce a low-fluorine, sponge-like phosphogypsum-based greening soil material with excellent structure, large fertility loading, and strong sustainability. This overcomes the problems of existing methods of reducing fluoride content through water washing, such as high water requirements, high costs, long cycles, unbalanced washing water, secondary water pollution, and loss of beneficial elements. It also addresses the problem of soil structural defects such as soil compaction and low porosity that can occur in existing methods of using phosphogypsum to prepare soil materials, leading to poor plant growth adaptability.

[0032] Based on strict scientific logic, the present invention ingeniously designs the preparation method, making the process interlocking and the effects cumulative layer by layer. Compared with the traditional prior art, it can more quickly and effectively reduce the content of soluble fluorides in the phosphogypsum soil material, and form a large number of pores in the soil material. The non-capillary porosity of the soil can reach more than 25%, making the phosphogypsum soil material have an excellent structure suitable for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the reaction principle diagram of the present invention.

[0034] Figure 2 It is the physical picture of the product of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0036] Embodiment 1

[0037] A low-fluorine spongy phosphogypsum-based greening soil material, comprising the following materials in parts by weight:

[0038] 100 parts of phosphogypsum for building (hemihydrate gypsum);

[0039] 20 parts of red soil clay, screened through a 20-mesh sieve;

[0040] 0.05 part of calcium dihydrogen phosphate;

[0041] 15 parts of substrate soil;

[0042] 0.1 part of ammonium bicarbonate and 0.05 part of calcium oxide;

[0043] 0.02 part of magnesium-iron-molybdenum-boron compound fertilizer, 0.01 part of potassium fulvate, 0.02 part of 85% mineral source fulvic acid, 0.01 part of composite microbial agent of Trichoderma harzianum and Bacillus subtilis, 0.5 part of rice husk and rice straw.

[0044] The specific preparation method is as follows:

[0045] S1. Mix the phosphogypsum for building and the red soil clay, and after mixing evenly, add the substrate soil and evenly add water using an umbrella-shaped nozzle, with a water-cement ratio of 0.4-0.5:1, to fully hydrate the building gypsum. After mixing the materials evenly, age for 3 days and then crush and screen, controlling the particle size to be less than 1 cm and the moisture content to be controlled at 15-20%.

[0046] S2 adds the remaining materials to the materials in step S1, adds water and mixes evenly. The water-cement ratio is 0.1 - 0.3:1. After aging for 3 days, a low-fluoride phosphogypsum-based greening soil material is obtained.

[0047] Soil test results: pH value is 6.35, soil bulk density is 1.2 kg / dm 3 , water content is 21%, non-capillary porosity is 33%, organic matter is 34 g / kg, hydrolyzable nitrogen is 177 mg / kg, available phosphorus is 55 mg / kg, available potassium is 291 mg / kg, water-soluble fluorine (horizontal oscillation method) is 1.7 mg / L. In the ryegrass planting experiment, germination starts after 3 days, and the seed germination rate is greater than 75%. The plant height exceeds 10 cm after 15 days.

[0048] Example 2

[0049] A low-fluoride spongy phosphogypsum-based greening soil material, including the following materials by weight:

[0050] Phosphogypsum (gypsum dihydrate) 50 parts, phosphogypsum for building 50 parts;

[0051] Red soil clay 10 parts, gibbsite 1 part, both are sieved through 20-mesh sieve and then mixed evenly;

[0052] Monocalcium phosphate 0.05 part;

[0053] Humus soil 10 parts, substrate soil 10 parts;

[0054] Ammonia water 0.05 part (diluted with 1:100 water), ammonium bicarbonate 0.1 part, calcium oxide 0.05 part;

[0055] Calcium, magnesium, iron, zinc, boron multi-component compound fertilizer 0.01 part, potassium humate 0.01 part, humic acid mixture 0.01 part, EM compound microbial inoculum 0.01 part, crushed straw plant fiber 0.3 part.

[0056] The specific preparation method is as follows:

[0057] S1. Mix phosphogypsum, phosphogypsum for building with red soil clay and gibbsite, add humus soil and substrate soil after mixing evenly and add water (including diluted ammonia water) evenly. The water-cement ratio is 0.4 - 0.5:1 to fully hydrate the building gypsum. After aging the evenly mixed materials for 3 days, crush and screen them, control the particle size to be less than 1 cm, and control the water content to be 15 - 20%.

[0058] S2. Add the remaining materials to the materials in step S1, add water and mix evenly. The water-cement ratio is 0.1 - 0.3:1. After aging for 3 days, a low-fluoride phosphogypsum-based greening soil material is obtained.

[0059] Soil test results: pH value is 6.51, soil bulk density is 1.3 kg / dm 3, with a moisture content of 22%, a non-capillary porosity of 31%, 44 g / kg of organic matter, 199 mg / kg of hydrolyzable nitrogen, 48 mg / kg of available phosphorus, 297 mg / kg of available potassium, and 1.1 mg / L of water-soluble fluorine (horizontal oscillation method). In the ryegrass planting experiment, germination started after three days, and the seed germination rate was greater than 80%. After 15 days, the plant height exceeded 10 cm.

[0060] Example 3

[0061] A low-fluorine sponge-like phosphogypsum-based greening soil material, comprising the following materials in parts by weight:

[0062] 20 parts of phosphogypsum (gypsum dihydrate), 50 parts of phosphoric acid building gypsum, and 30 parts of phosphoric acid composite gypsum;

[0063] 5 parts of red soil clay, 1 part of gibbsite, and 5 parts of mixed minerals such as hydromica, dickite, and halloysite. After passing through a 20-mesh sieve, they are mixed evenly;

[0064] 0.02 part of monocalcium phosphate and 0.01 part of calcium dihydrogen phosphate;

[0065] 10 parts of humus soil, 10 parts of substrate soil, and 5 parts of river and lake bottom mud;

[0066] 0.05 part of ammonia water (diluted with 1:100 water), 0.1 part of ammonium bicarbonate, and 0.05 part of calcium hydroxide;

[0067] 0.01 part of multi-element compound fertilizer, 0.01 part of potassium humate, 0.01 part of humic acid mixture, 0.01 part of compound microbial inoculant, and 0.5 part of waste mushroom bag plant fiber.

[0068] The specific preparation method is as follows:

[0069] S1 Mix phosphogypsum, phosphoric acid building gypsum, phosphoric acid composite gypsum with red soil clay, gibbsite, and mixed minerals. After mixing evenly, add humus soil, substrate soil, and river and lake bottom mud and evenly add water (including diluted ammonia water) to fully hydrate the building gypsum. After mixing the materials evenly, age for 3 days, then crush and screen to control the particle size to be less than 1 cm, and control the moisture content to be 15 - 20%.

[0070] S2 Add the remaining materials to the materials in step S1, add water and mix evenly. After aging for 3 days, a low-fluorine phosphogypsum-based greening soil material is obtained.

[0071] Soil test results: pH value 6.75, soil bulk density 1.2 kg / dm 3, with a moisture content of 25%, a non-capillary porosity of 35%, 45 g / kg of organic matter, 171 mg / kg of hydrolyzable nitrogen, 55 mg / kg of available phosphorus, 301 mg / kg of available potassium, and 1.5 mg / L of water-soluble fluorine (horizontal oscillation method). In the ryegrass planting experiment, germination started after three days, and the seed germination rate was greater than 80%. The plant height exceeded 10 cm after 15 days.

[0072] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A low-fluoride spongy phosphogypsum-based greening soil material, characterized in that It comprises the following materials in parts by weight: 100 parts of phosphogypsum; 5 - 20 parts of anion - adsorbing mineral; 0.01 - 0.1 part of water - soluble phosphate; 10 - 25 parts of organic matter; 0.05 - 0.2 part of environmental regulator; 0.1 - 1 part of additive.

2. The low-fluoride spongy phosphogypsum-based greening soil material according to claim 1, characterized in that: The phosphogypsum is at least one of untreated phosphogypsum and calcined phosphogypsum.

3. The low-fluoride spongy phosphogypsum-based greening soil material according to claim 1, characterized in that: The anion - adsorbing mineral is at least one of gibbsite, hydromica, dickite, halloysite, and red - soil clay.

4. The low-fluoride spongy phosphogypsum-based greening soil material according to claim 1, characterized in that: The water - soluble phosphate is at least one of calcium hydrogen phosphate and calcium dihydrogen phosphate.

5. A low-fluoride sponge-like phosphogypsum-based greening soil material according to claim 1, characterized in that: The organic matter is at least one of substrate soil, humus soil, domestic sewage sludge, and river - lake bottom mud.

6. The low-fluoride spongy phosphogypsum-based greening soil material according to claim 1, characterized in that: The environmental regulator is at least one of ammonia water, ammonium carbonate, ammonium bicarbonate, calcium oxide, and calcium hydroxide.

7. A low-fluorine spongy phosphogypsum-based greening soil material according to claim 1, characterized in that: The additive is at least one of plant fiber, multi - element medium - and - trace - element fertilizers, organic acids, and microorganisms; the plant fiber is at least one of straw, rice husk, rice straw, greening waste branches and leaves, tobacco waste branches and leaves, corncob, and waste mushroom bags; the multi - element medium - and - trace - element fertilizers contain at least one of magnesium, iron, manganese, copper, zinc, molybdenum, and boron elements; the organic acids contain at least one of humic acid, fulvic acid, humic acid, humin, fulvic acid, diethyl aminoethyl hexanoate, brassinolide, gibberellin, polyglutamic acid, and amino acid; the microorganisms include at least one of EM bacteria, Bacillus subtilis, Trichoderma harzianum, Bacillus amyloliquefaciens, Bacillus cereus, Bacillus methylotrophicus, Bacillus licheniformis, and Bacillus megaterium.

8. A low-fluoride sponge-like phosphogypsum-based greening soil material according to any one of claims 1 to 7, characterized in that: The preparation method of the soil material is as follows: S1. Mix the phosphogypsum and the anion - adsorbing mineral. First, mix the dry materials evenly, then add water and mix evenly again, so that the moisture content of the attached water in the mixed material is controlled at 10 - 20%; S2. Let the mixed material stand for aging for 3 - 5 days; S3. Mix the aged material in S2 with the water - soluble phosphate, organic matter, environmental regulator, and additive evenly again. Control the pH value at 6 - 8 through the environmental regulator, and age for 3 - 5 days again to obtain the target product.

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