A multifunctional mineral soil conditioner and its preparation method

Abstract

The present invention discloses a multifunctional mineral soil conditioner and a preparation method thereof. The method comprises the following steps: S1, vibrating and filtering byproduct gypsum and water, collecting the filter residue, and drying to obtain a first solid product; S2, adding the first solid product to an acid solution of a certain concentration, grinding and filtering, collecting the grinding filtrate, adding sodium hydroxide and hydrochloric acid to adjust the pH value and stirring, and filtering twice to obtain a calcium ion solution; S3, adding a certain amount of phosphorus-containing solution, adjusting the pH value with sodium hydroxide and hydrochloric acid solution, washing the reaction precipitate with deionized water, centrifuging, and drying to obtain a second solid reactant; S4, mixing the second solid reactant, a non-metallic mineral, an organic acid, and a binder to obtain a third solid mixture; S5, granulating the third solid mixture and drying to obtain a multifunctional mineral soil conditioner. The present invention can achieve more stable solidification of soil fluoride, buffer soil pH, and provide soil nutrient supply of calcium and phosphate fertilizers.

Description

Technical Field

[0001] The present invention relates to the technical field of soil conditioners, in particular to a multifunctional mineral soil conditioner and a preparation method thereof. Background Art

[0002] Soil fluoride comes from the natural geochemical effects of the earth on the one hand, and from the large amount of fluorine-containing waste discharged during industrial production processes such as steel smelting, electrolytic aluminum, and phosphorus chemical industry on the other hand. Fluoride in untreated soil enters the human food chain through leaching from surface water or groundwater, endangering human health. my country's high-fluoride areas are mainly concentrated in most parts of Guizhou, Chongqing and southwestern Hubei. The fluoride content in the soil in high-fluoride areas exceeds 980 mg / kg (far exceeding 150 mg / kg). The water-soluble fluoride content in the soil is the hub of the soil-water-plant-animal fluoride environmental risk, and is also an important factor in controlling and treating fluoride pollution. The problem of soil fluoride pollution is imminent, and it is urgent to develop efficient and economical soil defluoridation conditioners.

[0003] For soil fluoride pollution, the main remediation technologies currently include chemical passivation, chemical leaching, electric remediation, plant extraction, plant barrier and other remediation technologies. Although chemical leaching and electric remediation have high remediation efficiency, they are expensive, and there are only some small-scale pilot remediation projects at present; plant extraction and plant barrier control the remediation cost, but the remediation efficiency is low, and they face the problem of secondary pollution. Existing remediation technologies mainly adopt the principle of chemical passivation. By adding lime, gypsum, calcium magnesium salts, etc., fluorine metal compounds (CaF2, MgF2, etc.) are generated, which reduces the environmental soluble fluorine and weakens the bioaccessibility of fluorine. However, the current remediation efficiency of chemical passivation technology is 20% to 80%. At the same time, CaF2 (Ksp = 4×10 -11 ) and other fluorine-metal complexes still have the risk of re-release in acidic or alkaline soils, and due to the introduction of a large amount of calcium and magnesium salts, it is easy to cause soil compaction, increase soil pH, increase electrical conductivity, and cause secondary degradation of the soil. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to propose a multifunctional mineral soil conditioner and a preparation method thereof that can achieve more stable solidification of soil fluorine, buffer the soil pH value, and provide soil nutrient supply of calcium and phosphate fertilizers.

[0005] The preparation method of a multifunctional mineral soil conditioner of the present invention comprises the following steps:

[0006] S1, placing the by-product gypsum on a shaking bed at a fixed temperature for a period of time according to a certain liquid-solid ratio, filtering and taking the filter residue, further repeating the shaking several times, filtering and taking the filter residue, and drying at a certain temperature to obtain a first solid product;

[0007] S2, adding the first solid product to an acid solution of a certain concentration, compounding according to a certain liquid-solid ratio, placing it in a ball mill, grinding it at a certain speed for a period of time, collecting the grinding filtrate through primary filtration, adding sodium hydroxide and hydrochloric acid to adjust the pH value and stirring, and obtaining a first solution after secondary filtration;

[0008] S3, adding a certain amount of phosphorus-containing solution to the first solution, adjusting the pH with sodium hydroxide and hydrochloric acid solution, stirring and reacting at a certain temperature for a period of time, washing the reaction precipitate with deionized water, centrifuging, and drying to obtain a second solid reactant;

[0009] S4, fully mixing the second solid reactant, the non-metallic mineral, the organic acid, and the binder in a certain proportion to obtain a third solid mixture;

[0010] S5. Add a certain amount of water / anhydrous ethanol to the third solid mixture, quickly stir to form a mass, extrude and granulate, and quickly dry to obtain a multifunctional mineral soil conditioner.

[0011] Furthermore, in step S1, the by-product gypsum is one or more of phosphogypsum, desulfurized gypsum, fluorinated gypsum, and titanium gypsum, the liquid-solid ratio is 1 to 5:1, the shaking bed speed is 100 to 400 r / min, the shaking temperature is 25 to 60°C, the shaking is repeated 2 to 5 times, and the drying temperature is 45 to 105°C.

[0012] Furthermore, in step S2, the acid solution used is one or more of formic acid, hydrochloric acid, nitric acid, and sulfuric acid, the mass fraction of the acid solution is 5% to 20%, the liquid-solid ratio is 3 to 8:1, the ball milling speed is 100 to 500 r / min, the grinding time is 30 to 60 min, ammonia / sodium hydroxide is added to adjust the pH to 5.0 to 10.0, the continuous stirring speed is 400 to 1000 r / min, and the stirring time is 5 to 20 min.

[0013] Furthermore, in step S3, the phosphorus-containing solution is one of phosphoric acid, diammonium hydrogen phosphate, sodium hydrogen phosphate, and disodium hydrogen phosphate; the phosphorus concentration is 0.5 to 5 mmol / L; the amount of the phosphorus solution added is 25% to 50% of the amount of calcium ion in the first solution in step S2; the amount of the phosphorus solution is calculated as phosphorus, and the amount of the calcium ion solution is calculated as calcium; the pH is adjusted to 8.0 to 11.0 using ammonia water / sodium hydroxide and brine; the reaction temperature is 0 to 10° C., the stirring speed is 400 to 800 r / min, and the stirring reaction time is 2 to 10 min.

[0014] Furthermore, in step S4, the non-metallic minerals include one or more of illite, diatomaceous earth, montmorillonite, kaolin, halloysite, white / biotite, attapulgite, fly ash, coal gangue, and iron tailings.

[0015] Furthermore, the organic acid includes one or more of lactic acid, humic acid, citric acid, and malic acid.

[0016] Furthermore, the binder includes one or more of carboxymethyl cellulose, pregelatinized starch, and polyvinyl alcohol.

[0017] Furthermore, in step S4, the mass percentages of the substances are as follows: 45-65% of the second solid reactant, 25-50% of the non-metallic mineral, 2-8% of the organic acid, 0.5-3% of the pregelatinized starch, and 0.5-3% of the carboxymethyl cellulose.

[0018] Furthermore, in step S5, the amounts of water and ethanol added are 1-5% and 1-5% of the mass of the third solid mixture, respectively; the extrusion pressure is 2-7 MPa, the duration is 1-3 min, and the drying temperature is 70-120°C.

[0019] The multifunctional mineral soil conditioner is prepared by the above-mentioned preparation method.

[0020] Compared with the existing technical solutions, the embodiments of the present invention have at least the following advantages and effects:

[0021] 1. The present invention provides a multifunctional mineral soil conditioner to achieve in-situ fluorine pollution fixation technology, which is different from the existing calcium fluoride (Ksp = 4 × 10 -11 ) or magnesium fluoride (Ksp = 7.1 × 10 -11 ) passivation scheme, the fluorapatite generated by this scheme (Ksp=3.02×10 -59 ) to achieve more stable and efficient in-situ fixation of soil fluoride; it can be applied to soil in high-fluoride areas.

[0022] 2. The present invention utilizes organic acid to control the release of excess calcium ions, thereby improving the secondary soil degradation problem caused by the introduction of excessive metal salts in traditional technologies and significantly reducing the amount of soil conditioners required for soil input.

[0023] 3. The multifunctional mineral soil conditioner provided by the present invention is widely used in various pH conditions, solving the problem that traditional fluoride removal soil conditioners have poor effects under acidic conditions.

[0024] 4. This invention utilizes the excellent specific surface area and adsorption properties of non-metallic minerals to capture and adsorb free fluorine, further solidifying it in situ on the surface of the non-metallic minerals, thereby enhancing the in-situ passivation and fixation of fluorine and increasing its fixation rate. The high cation exchange properties of non-metallic minerals further limit calcium ion dissolution from the composite multifunctional mineral soil conditioner, mitigating the risk of secondary degradation.

[0025] 5. The multifunctional mineral soil conditioner provided by the present invention also releases the nutrient element phosphorus. On the one hand, it provides soil nutrition as a phosphorus fertilizer, and on the other hand, it cooperates with organic acids to buffer the soil pH, so that the soil pH is maintained at a neutral condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The multifunctional mineral soil conditioner prepared in Example 1 was used to test the amount of the artificially prepared fluorine-containing solution.

[0027] Figure 2 The effect of the multifunctional mineral soil conditioner prepared in Example 1 on the fluorine content in the solution;

[0028] Figure 3 The effect of the multifunctional mineral soil conditioner prepared in Example 1 on the phosphorus content in the solution;

[0029] Figure 4 The effect of the multifunctional mineral soil conditioner prepared in Example 1 on the pH value of the solution;

[0030] Figure 5 The multifunctional mineral soil conditioner prepared in Example 1 was tested for fluorine removal under different pH conditions;

[0031] Figure 6 The fluoride removal performance test of the multifunctional mineral soil conditioner prepared in Example 1 under different coexisting ions;

[0032] Figure 7 Comparison of the distribution and regulation of fluorine in the soil after 60 days of cultivation using the multifunctional mineral soil conditioner prepared in Example 1;

[0033] Figure 8 The content of available phosphorus in the soil of the multifunctional mineral soil conditioner prepared in Example 1 after 60 days of soil cultivation;

[0034] Figure 9 This is a comparison diagram of the XRD patterns of the multifunctional mineral soil conditioner prepared in Example 1 before and after the fluorine adsorption reaction;

[0035] Figure 10 This is a SEM image of the multifunctional mineral soil conditioner prepared in Example 1;

[0036] Figure 11 This is a SEM image of the multifunctional mineral soil conditioner prepared in Example 1 after curing with fluorine;

[0037] Figure 12 This is the EDS energy spectrum of the multifunctional mineral soil conditioner prepared in Example 1 after curing fluorine. DETAILED DESCRIPTION

[0038] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0039] Example 1:

[0040] (1) Preparation of multifunctional mineral soil conditioner

[0041] The phosphogypsum and deionized water were set to a liquid-solid ratio of 3, placed on a constant temperature shaking bed, vibrated at 40°C for 3 hours, and the shaking speed was set to 200 r / min. After filtering, the filter residue was taken and further shaken three times, and then the filter residue was filtered and dried at 75°C to obtain a first solid product. The first solid product was added with 10% hydrochloric acid, the liquid-solid ratio was set to 5, and then placed in a ball mill, and ground at a speed of 400 r / min for 30 minutes. The grinding filtrate was collected after primary filtration, and ammonia / sodium hydroxide and hydrochloric acid were added to adjust the pH to 9.0. After stirring at 400 r / min for 10 minutes, it was filtered twice to obtain a calcium ion solution. A diammonium phosphate solution (3 mmol / L) containing 33% of the amount of calcium in the calcium ion solution was added, and the pH was adjusted to 10.0 with ammonia water. The mixture was stirred at 5°C for 3 minutes. The reaction precipitate was washed twice with anhydrous ethanol and once with deionized water. The mixture was centrifuged at 9000 r / min for 3 minutes. The precipitate was collected and freeze-dried to obtain a second solid reactant. A third solid mixture was obtained by mixing 57% of the second solid reactant, 37% of montmorillonite, 3% of humic acid, 1% of malic acid, 1% of pregelatinized starch, and 1% of carboxymethyl cellulose. The third solid mixture was added with a certain amount of 4% deionized water and 2% anhydrous ethanol, and the mixture was rapidly stirred to form a mass. The mixture was extruded at a pressure of 5 MPa for 2 minutes to form granules. The mixture was quickly dried at 85°C to obtain a multifunctional mineral soil conditioner.

[0042] (2) Solution experiment of multifunctional mineral soil conditioner

[0043] The multifunctional mineral soil conditioner prepared in this embodiment was used to set up a dosage experiment. 0.005, 0.01, 0.015, 0.02, 0.03, 0.04, 0.05, and 0.06 g of sample were weighed in 10 ml of artificially configured fluoride ion solution (F-: 50 mg / L, pH = 6). The reaction solution was placed on a vibrator and reacted at 25 ° C for 36 h. The residual fluoride ion concentration of the solution was then determined using the fluoride ion selective electrode method. The amount of the conditioner used was calculated to be 3 g / L, which would allow the solution fluoride ion content to meet the national standard of 1.5 mg / L. Experiments were also conducted at different pH values. Artificially configured fluoride ion solution was used to simulate the soil pH range: 4, 5, 6, 7, 8, and 9. 0.03 g of sample was weighed and reacted in 10 ml of fluoride ion solution of different pH values ​​for 36 h. The residual fluoride ion concentration of the solution was then determined using the fluoride ion selective electrode method. It was calculated that under all pH conditions, the removal rate of fluoride ions in the liquid was above 94%. An experiment on the kinetic changes of solution ions was carried out. 0.6 g of soil conditioner was dissolved in 200 ml of fluoride ion solution (F: 50 mg / L, pH = 6). The sampling time points were set at 5, 30, 60, 180, 300, 360, 420, 540, 720, 1440, 2160, 2880, and 4320 min, and the pH value of the solution was recorded each time. After sampling, the fluoride ion selective electrode method was used to determine the fluoride ion in the solution, and the calcium and phosphorus concentrations in the solution were determined using ICP-OES.

[0044] (3) Soil experiment of multifunctional mineral soil conditioner

[0045] 5g and 15g of soil conditioner were weighed and placed in 500g of high-fluoride soil. Seven control samples were prepared: a blank (no additives), a second solid sample (1% and 3%), and montmorillonite (1% and 3%). After mixing, deionized water was added to the soil until saturated. Continuous sampling was conducted over 60 days to monitor fluoride distribution and available phosphorus content in the soil, with sampling times of 0, 3, 7, 14, 28, and 60 days. After 60 days of incubation, soil samples were collected for fluoride content analysis. Soluble fluoride was extracted with deionized water, metal oxide-bound fluoride was extracted with hydroxylamine hydrochloride solution, organic matter-bound fluoride was extracted with a nitric acid-hydrogen peroxide-ammonium acetate mixture, and solid fluoride was extracted using an alkaline solution. Available phosphorus in the soil was extracted with a 0.5 mol / L NaHCO3 solution. Fluoride concentration was determined using a fluoride ion-selective electrode, and phosphorus concentration in the solution was determined using inductively coupled plasma ion emission spectroscopy (ICP-OES). When 3% soil conditioner was added, the soluble fluorine content in the soil was calculated to be reduced by 94.75%, and the available phosphorus content increased from 89.2 mg / kg to 208.3 mg / kg.

[0046] See attached Figure 1The multifunctional mineral soil conditioner prepared in this embodiment was tested for removing artificially prepared fluoride-containing solution. As the dosage of the conditioner increased, the fluoride ion content in the solution decreased, and at a dosage of 3 g / L, it dropped to 1.0 mg / L, meeting the national drinking water (GB 5749-2022) standard for fluoride ion content in water bodies.

[0047] See attached Figure 2 The multifunctional mineral soil conditioner prepared in this embodiment changes the fluoride in the solution. As time changes, the fluoride ion concentration gradually decreases, and the conditioner group has better fluoride removal performance.

[0048] See attached Figure 3 The multifunctional mineral soil conditioner prepared in this embodiment changes the phosphorus concentration in the solution over time. It can be seen that under the same dosage, the conditioner group can release more phosphorus (P), and the endpoint phosphorus (P) concentration is more than three times that of the second solid, with an excellent slow-release phosphorus effect.

[0049] See attached Figure 4 The multifunctional mineral soil conditioner prepared in this embodiment changes the pH of the solution over time. It is noted that the pH of the solution first increases and then decreases, and finally maintains at around 7-8, which indicates that the soil conditioner also has the function of stabilizing the soil pH.

[0050] See attached Figure 5 The multifunctional mineral soil conditioner prepared in this embodiment was tested for fluorine removal under different pH conditions. It can be seen that under different pH conditions, the conditioner can achieve excellent fluorine removal effect, and the removal rate of fluoride ions in the solution is above 93%, which indicates that the soil conditioner can be applied to most soil pH values ​​and has broad application prospects.

[0051] See attached Figure 6 , is a comparison of the fluoride removal performance of the soil conditioner and the second solid under different coexisting ions. The results show that chloride ions, sulfate ions, bicarbonate ions, and nitrate ions that may exist in the environment have little effect on the performance, further confirming its wide environmental applicability.

[0052] See attached Figure 7 The multifunctional mineral soil conditioner prepared in this example was used to in-situ remediate fluoride contamination in soil. It can be seen that after 60 days of remediation, the relative content of biotoxic, water-soluble fluorine significantly decreased to 0.21%. Comparisons of a blank, montmorillonite, and a second solid mixture revealed that the soil fluoride fixation effect of using only montmorillonite or the second solid was significantly worse than that of the multifunctional mineral soil conditioner prepared in this example. This confirms that the multifunctional mineral soil conditioner's ability to fix soil fluoride is a synergistically enhanced result of the interaction between the montmorillonite and the second solid reactant.

[0053] See attached Figure 8 The relative content of available phosphorus in the soil prepared in this example was measured at 0, 3, 7, 14, 28, and 60 days of incubation. As the incubation time increased, the available phosphorus content in the soil reached an equilibrium value on the 28th day and stabilized at around 210 mg / kg, confirming that the multifunctional mineral soil conditioner had a slow-release phosphorus effect in the soil.

[0054] See attached Figure 9 , which is the XRD comparison diagram of the multifunctional mineral soil conditioner prepared in this embodiment before and after the reaction. It can be clearly seen that after the fluorine removal reaction, a crystalline phase of fluorapatite is generated, confirming that the in-situ solidification of fluorine forms stable fluorapatite, reducing the biological toxicity of fluoride ions in the soil.

[0055] See attached Figure 10 , which is an SEM image of the multifunctional mineral soil conditioner prepared in this example, it can be seen that the second solid mixture and the montmorillonite layer structure are combined with each other.

[0056] See attached Figure 11 , is the SEM image of the multifunctional mineral soil conditioner prepared in this embodiment after solidification with fluorine, compared with the attached Figure 10 A new granular structure was generated on the surface of the montmorillonite layer, proving that the defluorinated and solidified fluorapatite grew on the surface of montmorillonite.

[0057] See attached Figure 12 , which is the EDS energy spectrum of the multifunctional mineral soil conditioner prepared in this embodiment after solidification with fluorine treatment. It can be seen that the element distribution of F is the same as that of Si, Al, Ca, and P elements, and is in a uniformly dispersed state, confirming that montmorillonite plays a template role in the fixation of fluorine.

[0058] The multifunctional mineral soil conditioner of this embodiment can adsorb and capture free fluorine, further solidifying it in situ on the montmorillonite surface, thereby enhancing the in-situ passivation and fixation of fluorine and increasing its fixation rate. The high cation exchange properties of montmorillonite further limit calcium ion dissolution from the composite multifunctional mineral soil conditioner, mitigating the risk of secondary degradation.

[0059] Example 2:

[0060] (1) Preparation of multifunctional mineral soil conditioner

[0061] The desulfurized gypsum and deionized water were set to a liquid-solid ratio of 3, placed on a constant temperature shaking bed, vibrated at 60°C for 3 hours, and the shaking speed was set to 300r / min. After filtering, the filter residue was taken and further shaken three times, and then the filter residue was filtered and dried at 105°C to obtain the first solid product. The first solid product was added with 20% hydrochloric acid, the liquid-solid ratio was set to 3, and then placed in a ball mill, and ground at a speed of 200r / min for 45min. The grinding filtrate was collected after primary filtration, and ammonia / sodium hydroxide and hydrochloric acid were added to adjust the pH to 10.0. After stirring at 500r / min for 10min, it was filtered twice to obtain a calcium ion solution. Add 20% of the amount of calcium in the calcium ion solution, disodium hydrogen phosphate (2.5mmol / L) solution, ammonia water to adjust the pH to 10.0, stir and react at 5°C for 10 minutes, wash the reaction precipitate twice with anhydrous ethanol, then wash it once with deionized water, centrifuge it at 8000r / min for 5 minutes, collect the precipitate and freeze-dry it to obtain a second solid reactant. Use 45% of the second solid reactant, 45% of kaolinite, 7% of malic acid, and 3% of carboxymethyl cellulose to mix thoroughly to obtain a third solid mixture. Add a certain amount of 4% deionized water and 2% anhydrous ethanol to the third solid mixture, stir it quickly to form a mass, press it at a pressure of 7Mpa for 2 minutes to form granules, and quickly dry it at 85°C to obtain a multifunctional mineral soil conditioner.

[0062] (2) Solution experiment of multifunctional mineral soil conditioner

[0063] The multifunctional mineral soil conditioner prepared in this example was used to treat a fluoride ion solution (F-: 50 mg / L, pH = 6). The calculated dosage of the conditioner was 3.5 g / L, which was sufficient to ensure that the fluoride ion content of the solution met the national standard (GB 5749-2022) of 1.0 mg / L.

[0064] (3) Soil experiment of multifunctional mineral soil conditioner

[0065] Weighing 15g of the soil conditioner from this example and placing it in 500g of high-fluoride soil, the addition of 3% soil conditioner reduced the soluble fluoride content in the soil by 92.4%, while the available phosphorus content increased from 89.2mg / kg to 195.3mg / kg.

[0066] Example 3:

[0067] (1) Preparation of multifunctional mineral soil conditioner

[0068] The titanium gypsum and deionized water are set to a liquid-solid ratio of 4, placed on a constant temperature shaking bed, vibrated at 50°C for 4 hours, and the shaking speed is set to 300r / min. After filtering, the filter residue is taken and further shaken three times, the filter residue is filtered and dried at 75°C to obtain the first solid product. The first solid product is added with 15% hydrochloric acid, the liquid-solid ratio is set to 3, and then placed in a ball mill. It is ground at a speed of 200r / min for 45min, and the grinding filtrate is collected after one filtration. Ammonia water / sodium hydroxide and hydrochloric acid are added to adjust the pH to 10.0. After stirring at 500r / min for 10min, it is filtered twice to obtain a calcium ion solution. A sodium hydrogen phosphate solution (4 mmol / L) containing 20% ​​of the amount of calcium in the calcium ion solution was added, and the pH was adjusted to 10.0 with ammonia water. The mixture was stirred at 5°C for 10 minutes. The reaction precipitate was washed twice with anhydrous ethanol and once with deionized water. The mixture was centrifuged at 8000 r / min for 5 minutes, and the precipitate was collected and freeze-dried to obtain a second solid reactant. A third solid mixture was obtained by mixing 60% of the second solid reactant, 10% of kaolinite, 20% of diatomaceous earth, 1.5% of citric acid, 3% of humic acid, 3% of lactic acid, and 2.5% of pregelatinized starch. The third solid mixture was added with a certain amount of 4% deionized water and 2% anhydrous ethanol, and the mixture was rapidly stirred to form a mass. The mixture was extruded at a pressure of 5 MPa for 5 minutes to form granules. The mixture was quickly dried at 85°C to obtain a multifunctional mineral soil conditioner.

[0069] (2) Solution experiment of multifunctional mineral soil conditioner

[0070] The multifunctional mineral soil conditioner prepared in this example was used to treat a fluoride ion solution (F-: 50 mg / L, pH = 6). The calculated dosage of 2 g / L of the conditioner was sufficient to ensure that the fluoride ion content of the solution met the national standard (GB 5749-2022) of 1.0 mg / L.

[0071] (3) Soil experiment of multifunctional mineral soil conditioner

[0072] Weighing 15g of the soil conditioner from this example and placing it in 500g of high-fluoride soil, the addition of 3% soil conditioner reduced the soluble fluoride content in the soil by 95.1%, while the available phosphorus content increased from 89.2mg / kg to 231.7mg / kg.

[0073] Example 4:

[0074] (1) Preparation of multifunctional mineral soil conditioner

[0075] After mixing phosphogypsum and desulfurized gypsum in a ratio of 1:1, the mixture was added with deionized water to set the liquid-solid ratio to 3, placed on a constant temperature shaking bed, vibrated at 50°C for 4 hours, and the shaking speed was set to 300r / min. After filtering, the filter residue was taken and further shaken three times, filtered and the filter residue was taken, and dried at 75°C to obtain the first solid product. The first solid product was added with 15% hydrochloric acid, the liquid-solid ratio was set to 3, and then placed in a ball mill, ground at a speed of 200r / min for 45min. The grinding filtrate was collected after the first filtration, and ammonia / sodium hydroxide and hydrochloric acid were added to adjust the pH to 10.0. After stirring at a speed of 500r / min for 10min, the calcium ion solution was obtained after the second filtration. A phosphoric acid solution (3 mmol / L) of 25% of the amount of calcium in the above calcium ion solution is added, and the pH is adjusted to 11.0 with ammonia water. The mixture is stirred at 10°C for 5 minutes. The reaction precipitate is washed twice with anhydrous ethanol and once with deionized water. The mixture is centrifuged at 8000 r / min for 5 minutes, and the precipitate is collected and freeze-dried to obtain a second solid reactant. A third solid mixture is obtained by mixing 55% of the second solid reactant, 20% of attapulgite, 20% of halloysite, 2% of lactic acid, 2% of pregelatinized starch, and 1% of polyvinyl alcohol. The third solid mixture is added with a certain amount of 4% deionized water and 2% anhydrous ethanol, and the mixture is quickly stirred into a mass. The mixture is extruded at a pressure of 5 MPa for 5 minutes to form granules. The mixture is quickly dried at 85°C to obtain a multifunctional mineral soil conditioner.

[0076] (2) Solution experiment of multifunctional mineral soil conditioner

[0077] The multifunctional mineral soil conditioner prepared in this example was used to treat a fluoride ion solution (F-: 50 mg / L, pH = 6). The calculated dosage of 2 g / L of the conditioner was sufficient to ensure that the fluoride ion content of the solution met the national standard (GB 5749-2022) of 1.0 mg / L.

[0078] (3) Soil experiment of multifunctional mineral soil conditioner

[0079] Weighing 15g of the soil conditioner from this example and placing it in 500g of high-fluoride soil, the addition of 3% soil conditioner reduced the soluble fluoride content in the soil by 92.7%, while the available phosphorus content increased from 89.2mg / kg to 204.4mg / kg.

[0080] Example 5:

[0081] (1) Preparation of multifunctional mineral soil conditioner

[0082] Titanium gypsum and desulfurized gypsum were mixed in a 1:1 ratio and then mixed with deionized water to set the liquid-solid ratio to 3. The mixture was placed on a constant temperature shaking bed and vibrated at 60°C for 3 hours. The shaking speed was set to 200r / min. After filtering, the filter residue was taken and the shaking was repeated 3 times. The filter residue was filtered and dried at 85°C to obtain the first solid product. The first solid product was added with 18% hydrochloric acid, the liquid-solid ratio was set to 3, and then placed in a ball mill. It was ground at a speed of 400r / min for 30min. The grinding filtrate was collected after one filtration, and ammonia / sodium hydroxide and hydrochloric acid were added to adjust the pH to 9.0. The speed was set to 400r / min and stirred for 5min. After secondary filtration, a calcium ion solution was obtained. A sodium hydrogen phosphate (5 mmol / L) solution containing 25% of the amount of calcium in the calcium ion solution was added, and the pH was adjusted to 10.0 with ammonia water. The mixture was stirred at 4°C for 5 minutes. The reaction precipitate was washed twice with anhydrous ethanol and once with deionized water. The mixture was centrifuged at 8000 r / min for 5 minutes, and the precipitate was collected and freeze-dried to obtain a second solid reactant. A third solid mixture was obtained by mixing 35% of the second solid reactant, 15% of illite, 15% of muscovite, 25% of montmorillonite, 5% of malic acid, 3% of polyvinyl alcohol, and 2% of carboxymethyl cellulose. The third solid mixture was added with a certain amount of 4% deionized water and 2% anhydrous ethanol, and the mixture was rapidly stirred to form a mass. The mixture was extruded at a pressure of 5 MPa for 5 minutes to form granules. The mixture was quickly dried at 85°C to obtain a multifunctional mineral soil conditioner.

[0083] (2) Solution experiment of multifunctional mineral soil conditioner

[0084] The multifunctional mineral soil conditioner prepared in this example was used to treat a fluoride ion solution (F-: 50 mg / L, pH = 6). The calculated dosage of the conditioner was 4 g / L, which was sufficient to ensure that the fluoride ion content of the solution met the national standard (GB 5749-2022) of 1.0 mg / L.

[0085] (3) Soil experiment of multifunctional mineral soil conditioner

[0086] Weighing 15g of the soil conditioner from this example and placing it in 500g of high-fluoride soil, the addition of 3% soil conditioner reduced the soluble fluoride content in the soil by 90.2%, while the available phosphorus content increased from 89.2mg / kg to 179.3mg / kg.

[0087] Any matters not mentioned above shall be subject to the existing technology.

[0088] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a multifunctional mineral soil conditioner, characterized in that: The steps include: S1, placing the by-product gypsum on a shaking bed at a fixed temperature for a period of time according to a certain liquid-solid ratio, filtering and taking the filter residue, further repeating the shaking several times, filtering and taking the filter residue, and drying at a certain temperature to obtain a first solid product; S2, adding the first solid product to an acid solution of a certain concentration, compounding according to a certain liquid-solid ratio, placing it in a ball mill, grinding it at a certain speed for a period of time, collecting the grinding filtrate through primary filtration, adding sodium hydroxide and hydrochloric acid to adjust the pH value and stirring, and obtaining a first solution after secondary filtration; S3. Add a certain amount of phosphorus-containing solution to the first solution, and adjust the pH to 8.0-11.0 using ammonia / sodium hydroxide and brine; the reaction temperature is 0-10°C, the stirring speed is 400-800 r / min, and the stirring reaction time is 2-10 min. The reaction precipitate is washed with deionized water, centrifuged, and dried to obtain a second solid reactant; S4, fully mixing the second solid reactant, the non-metallic mineral, the organic acid, and the binder in a certain proportion to obtain a third solid mixture; S5. Add a certain amount of water / anhydrous ethanol to the third solid mixture, quickly stir to form a mass, extrusion granulate, and quickly dry to obtain a multifunctional mineral soil conditioner; In step S4, the mass percentages of the substances are as follows: second solid reactant 45-65%, non-metallic mineral 25-50%, organic acid 2-8%, pregelatinized starch 0.5-3%, binder 0.5-3%; The concentration of phosphorus is 0.5~5 mmol / L, and the amount of the phosphorus solution added is 25%~50% of the amount of calcium ion in the first solution in step S2. The amount of the phosphorus solution is calculated in terms of phosphorus, and the amount of the calcium ion solution is calculated in terms of calcium.

2. The preparation method according to claim 1, wherein: In step S1, the by-product gypsum is one or more of phosphogypsum, desulfurized gypsum, fluorinated gypsum, and titanium gypsum, the liquid-solid ratio is 1-5:1, the shaking bed speed is 100-400 r / min, the shaking temperature is 25-60°C, the shaking is repeated 2-5 times, and the drying temperature is 45-105°C.

3. The preparation method according to claim 1, wherein: In step S2, the acid solution used is one or more of formic acid, hydrochloric acid, and nitric acid, the mass fraction of the acid solution is 5% to 20%, the liquid-to-solid ratio is 3 to 8:1, the ball milling speed is 100 to 500 r / min, the grinding time is 30 to 60 min, ammonia / sodium hydroxide and hydrochloric acid are added to adjust the pH to 5.0 to 10.0, the stirring speed is continuously 400 to 1000 r / min, and the stirring time is 5 to 20 min.

4. The preparation method according to claim 1, wherein: In step S3, the phosphorus-containing solution is one of phosphoric acid, diammonium hydrogen phosphate, sodium hydrogen phosphate, and disodium hydrogen phosphate.

5. The preparation method according to claim 1, wherein: In step S4, the non-metallic minerals include one or more of illite, diatomaceous earth, montmorillonite, kaolin, halloysite, white / biotite, attapulgite, fly ash, coal gangue, and iron tailings.

6. The preparation method according to claim 1, wherein: The organic acid includes one or more of lactic acid, humic acid, citric acid and malic acid.

7. The preparation method according to claim 1, wherein: The binder includes one or more of carboxymethyl cellulose, pregelatinized starch, and polyvinyl alcohol.

8. The preparation method according to claim 1, wherein: In step S5, the amounts of water and ethanol added are 1-5% and 1-5% of the mass of the third solid mixture, respectively; the extrusion pressure is 2-7 MPa, the duration is 1-3 min, and the drying temperature is 70-120°C.

9. A multifunctional mineral soil conditioner prepared by the preparation method according to any one of claims 1 to 8.

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