Preparation and application of metallurgical slag waste alkali material for harmlessly treating ardealite

Abstract

The invention discloses a metallurgical slag waste alkali material for innocent treatment of ardealite and a preparation method and application of the metallurgical slag waste alkali material. The method comprises the following steps: carrying out dry mixing and mechanical stirring on metallurgical slag and metal oxide according to a mass ratio of (3-1.5): 1 to obtain a waste alkali material dry basis; and adding water, stirring and pre-activating for 1-2 hours to form a slurry finished product. The slurry is mixed with ardealite according to the mass ratio of the dry basis to the ardealite being (1: 100)-(2: 100), and after stirring, standing and curing, soluble phosphorus and fluorine can be effectively cured, and the pH value is stabilized between 6 and 9. The metallurgical slag and the metal oxide are used as raw materials, the cost is low, the process is simple, harmless treatment of phosphogypsum and resource utilization of metallurgical solid waste are achieved, and good economic benefits and environmental benefits are achieved.

Description

Technical Field

[0001] This invention relates to a method for preparing a metallurgical slag waste alkali material for the harmless treatment of phosphogypsum, and also to the application of this metallurgical slag waste alkali material in the harmless treatment of phosphogypsum, belonging to the field of solid waste resource utilization technology. Background Technology

[0002] Phosphogypsum is a large-scale solid waste byproduct generated during the wet-process phosphoric acid production industry. Statistics show that approximately 4-5 tons of phosphogypsum are produced for every ton of phosphoric acid (calculated as P2O5). Long-term reliance on the wet-process phosphoric acid production has led to a continuous increase in my country's phosphogypsum stockpile, currently exceeding 820 million tons, causing severe environmental and land resource pressure.

[0003] Phosphogypsum's main component is calcium sulfate dihydrate, and it also contains soluble phosphorus, fluorine, heavy metals, and organic impurities. Among these, soluble phosphorus and fluorine are the most prominent pollutants during phosphogypsum storage. Due to their solubility, phosphorus and fluorine easily enter surrounding water bodies in soluble form through rainwater leaching or leachate, potentially leading to eutrophication and long-term pollution of soil and groundwater.

[0004] Currently, the common method for the harmless treatment of phosphogypsum is lime neutralization, which involves adding lime to fix soluble phosphorus and fluorine into insoluble compounds. While this method has some effectiveness, it requires large amounts of lime, and in practice, it is difficult to simultaneously achieve stable environmental protection requirements for soluble phosphorus, soluble fluorine, and pH value. Therefore, the treatment effect is limited and the cost is high.

[0005] On the other hand, metallurgical slag, a typical industrial solid waste generated during the smelting of metals such as steel, magnesium, and manganese, accounts for approximately 600-700 million tons annually in my country. The large-scale stockpiling of metallurgical slag not only occupies land but also poses environmental risks. Therefore, promoting the resource-efficient utilization of metallurgical slag has become an urgent need for the industry. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention provides a method for the harmless treatment of phosphogypsum using metallurgical slag waste alkali materials, thereby solving the problems of slow reaction rate and low adsorption efficiency of existing metallurgical slag solid waste with phosphorus and fluorine.

[0007] To achieve the above objectives, the present invention first provides a method for preparing metallurgical slag alkali material for the harmless treatment of phosphogypsum, comprising the following steps: (1) Mix metallurgical slag and metal oxide at a mass ratio of (3-1.5):1, and mechanically stir at a speed of ≥60 r / min for ≥30 min to obtain the dry basis of waste alkali material; (2) Add water to the dry base of the waste alkali material obtained in step (1), and control the mass ratio of metallurgical slag: metal oxide: water to be (3~1.5):1:(10~20). Stir mechanically at a speed of ≥60r / min and pre-activate for 1~2h to convert the metal oxide into highly active hydroxide, and obtain a slurry product that can simultaneously solidify soluble phosphorus and fluorine in phosphogypsum and adjust the pH value to neutral. The metallurgical slag is selected from at least one of steel slag, magnesium slag, and manganese slag; the metal oxide is selected from at least one of calcium oxide, magnesium oxide, and aluminum oxide.

[0008] Preferably, in step (1), the metallurgical slag is magnesium slag and the metal oxide is calcium oxide, wherein the mass ratio of magnesium slag to calcium oxide is 3:1.

[0009] Preferably, in step (1), the metallurgical slag is magnesium slag and the metal oxide is aluminum oxide or magnesium oxide, wherein the mass ratio of magnesium slag to aluminum oxide is 1:0.6, or the mass ratio of magnesium slag to magnesium oxide is 1:0.375.

[0010] Preferably, in step (1), the metallurgical slag is steel slag or manganese slag, and the metal oxide is calcium oxide, wherein the mass ratio of steel slag to calcium oxide is 1:0.5, or the mass ratio of manganese slag to calcium oxide is 1.5:0.5.

[0011] Based on this, the present invention further provides an application of the above-mentioned metallurgical slag waste alkali material in the harmless treatment of phosphogypsum, specifically including the following steps: The slurry product is added to phosphogypsum at a mass ratio of waste alkali material dry basis to phosphogypsum dry basis of 1:100 to 2:100. After mechanical stirring for ≥1 hour, it is allowed to stand and solidify for ≥4 hours so that the treated phosphogypsum meets the following requirements: soluble phosphorus concentration ≤0.5mg / L; soluble fluorine concentration ≤10mg / L; pH value 6 to 9.

[0012] Preferably, the mass ratio of the dry basis of the waste alkali material to the dry basis of phosphogypsum is 2:100.

[0013] Preferably, the static curing time is 4 to 8 hours.

[0014] Ideally, the pH value of the treated phosphogypsum should be 7–8.

[0015] Preferably, the treated phosphogypsum is in a semi-dry, light gray granular state with a particle size of 0.1–0.8 mm.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The metallurgical slags (steel slag, magnesium slag, manganese slag, etc.) used in this invention are rich in alkaline oxides such as CaO, MgO, and Fe2O3, and are all strongly alkaline waste materials. Specifically, steel slag is a solid waste produced by steelmaking technology, and its main components include Ca2SiO4, Fe2O3, and MgO. Magnesium slag is a solid waste produced during the smelting of metallic magnesium, and its main components are Ca2SiO4 and MgO. Manganese slag is a solid waste produced during the smelting of metallic manganese, and its main components include Ca2SiO4, FeS2, Al2O3, and MnO. All of the above metallurgical slags belong to the residues produced by metal smelting processes that require treatment, and are typical sources of solid waste pollution.

[0017] 2. This invention utilizes the alkaline oxides such as CaO, MgO, and Fe2O3 abundant in the above-mentioned metallurgical slag to solidify the soluble phosphorus and soluble fluorine in phosphogypsum, thereby generating insoluble phosphides and fluorides, and realizing the resource-based secondary utilization of metallurgical slag.

[0018] 3. This invention mixes metal oxides with metallurgical slag, increasing the number of active sites in the composite waste alkali material and improving the final solidification of phosphorus and fluorine, thus ensuring the treatment effect of phosphogypsum.

[0019] 4. This invention prepares a slurry from metallurgical slag waste alkali material after pre-activation in water. This slurry exhibits strong alkalinity, effectively controlling the pH value of phosphogypsum. Simultaneously, the metal oxides within the metallurgical slag waste alkali material are further converted into hydroxides, exhibiting a higher affinity for soluble phosphorus and fluorine. This allows the treated phosphogypsum to simultaneously meet the standards for soluble phosphorus, soluble fluorine, and pH value, thus satisfying national emission standards and solving the environmental problems associated with phosphogypsum.

[0020] 5. The preparation process of the metallurgical slag waste alkali material and its harmless treatment process for phosphogypsum provided by the present invention is simple, requires low equipment, is easy to operate, and is easy to implement on a large scale.

[0021] 6. This invention can also be further extended to the treatment of phosphorus- and fluoride-containing wastewater generated in various industries such as industry, agriculture, and medicine, and has broad application prospects. Attached Figure Description

[0022] Figure 1 The images show the XRD patterns of the original magnesium slag and the magnesium slag-based composite calcium oxide waste alkali material prepared in Example 2. Detailed Implementation

[0023] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only used to illustrate the technical solution of the present invention and are not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are still within the protection scope of the present invention.

[0024] In the metal smelting industry, the most common metallurgical slags—steel slag, magnesium slag, and manganese slag—are rich in alkaline oxides such as CaO, MgO, and Fe2O3 due to their metal smelting processes. These can be considered highly alkaline waste materials. Theoretically, these highly alkaline metallurgical slags have an affinity for phosphorus and fluorine, and thus possess the potential to remove soluble phosphorus and fluorine from phosphogypsum.

[0025] In practical applications, the effective active components in the aforementioned industrial metallurgical slag are low, specifically the relative content of free alkaline oxides such as CaO, MgO, and Fe2O3 is low, and some of these alkaline oxides are encapsulated by inert matrices such as silicates. The reaction rate between these effective components in the metallurgical slag and the phosphorus and fluorine in phosphogypsum is slow, or even negligible. Therefore, directly reacting the metallurgical slag with phosphogypsum results in low adsorption efficiency and fails to meet the requirements for harmless treatment.

[0026] How to effectively activate the adsorption sites of metallurgical slag and improve its curing efficiency for soluble phosphorus and fluorine in phosphogypsum has become an urgent technical problem to be solved. Once solved, metallurgical slag can be reused, and soluble phosphorus and fluorine can be cured efficiently and at low cost, with significant market prospects.

[0027] Therefore, this invention increases the adsorption sites of metallurgical slag by adding metal oxides and pre-activating it in an aqueous medium, converting the metal oxides into highly reactive hydroxides, thus significantly enhancing its affinity and immobilization ability for phosphorus and fluorine. This method effectively improves the adsorption efficiency and reaction rate of soluble phosphorus and fluorine in phosphogypsum by metallurgical slag-based waste alkali materials.

[0028] This invention is applicable to the environmentally friendly treatment of phosphogypsum, a byproduct of the wet-process phosphoric acid production, while simultaneously realizing the resource utilization of industrial solid wastes such as metallurgical slag. By converting metal smelting residues into highly efficient waste alkali materials and using them to solidify soluble phosphorus and fluorine pollutants in phosphogypsum, this invention achieves the dual environmental benefits of harmless treatment of phosphogypsum and value-added utilization of solid waste.

[0029] Example 1: Steel slag-based composite calcium oxide waste alkali material A method for preparing metallurgical slag alkali material includes the following steps: S1: Weigh 100g of steel slag and 50g of calcium oxide, and mechanically stir at 60r / min for 30min to obtain the dry basis of steel slag-based waste alkali material.

[0030] S2: Add 500 mL of deionized water to the dry base of steel slag-based waste alkali material, mechanically stir at 120 r / min, mix evenly, and pre-activate for 2 h to obtain the slurry product of steel slag-based waste alkali material.

[0031] Example 2: Magnesium slag-based composite calcium oxide waste alkali material A method for preparing metallurgical slag alkali material includes the following steps: S1: Weigh 150g of magnesium slag and 50g of calcium oxide, and mechanically stir at 60r / min for 30min to obtain the dry basis of magnesium slag-based waste alkali material.

[0032] S2: Add 500 mL of deionized water to the dry base of magnesium slag-based waste alkali material, mechanically stir at 120 r / min, mix evenly, and pre-activate for 2 h to obtain the slurry product of magnesium slag-based waste alkali material.

[0033] like Figure 1 The image shows the X-ray diffraction (XRD) patterns of the original magnesium slag and the magnesium slag-based composite calcium oxide waste alkali material prepared in Example 2. The XRD patterns show that the main components of the magnesium slag are Ca2SiO4 and MgO, while the main components of the magnesium slag-based waste alkali material are Ca2SiO4, MgO, and CaO.

[0034] Example 3: Manganese slag-based composite calcium oxide waste alkali material A method for preparing metallurgical slag alkali material includes the following steps: S1: Weigh 150g of manganese slag and 50g of calcium oxide, and mechanically stir at 60r / min for 30min to obtain dry basis of manganese slag-based waste alkali material.

[0035] S2: Add 500 mL of deionized water to the dry base of manganese slag-based waste alkali material, mechanically stir at 120 r / min, mix evenly, and pre-activate for 2 h to obtain the slurry product of manganese slag-based waste alkali material.

[0036] Example 4: Magnesium slag-based composite alumina waste alkali material A method for preparing metallurgical slag alkali material includes the following steps: S1: Weigh 100g of magnesium slag and 60g of alumina, and mechanically stir at 60r / min for 60min to obtain the dry basis of magnesium slag-based waste alkali material.

[0037] S2: Add 1000mL of deionized water to the dry base of magnesium slag-based waste alkali material, and mechanically stir at 120r / min until uniformly mixed. After pre-activation for 2 hours, the slurry product of magnesium slag-based waste alkali material is obtained.

[0038] Example 5: Magnesium slag-based composite magnesium oxide waste alkali material A method for preparing metallurgical slag alkali material includes the following steps: S1: Weigh 80g of magnesium slag and 30g of magnesium oxide, and mechanically stir at 60r / min for 30min to obtain the dry basis of magnesium slag-based waste alkali material.

[0039] S2: Add 600 mL of deionized water to the dry base of magnesium slag-based waste alkali material, mechanically stir at 80 r / min, mix evenly, and pre-activate for 1 h to obtain the slurry product of magnesium slag-based waste alkali material.

[0040] Example 6: Comparative Example 1 S1: Weigh 50g of steel slag, add it to 250mL of deionized water, and mechanically stir at 120r / min until it is evenly mixed. After pre-activation for 2h, steel slag slurry is obtained.

[0041] Example 7: Comparative Example 2 S1: Weigh 50g of magnesium slag, add it to 250mL of deionized water, and mechanically stir at 120r / min until it is evenly mixed. After pre-activation for 2h, magnesium slag slurry is obtained.

[0042] Example 8: Comparative Example 3 S1: Weigh 50g of manganese slag, add it to 250mL of deionized water, and mechanically stir at 120r / min until it is evenly mixed. After pre-activation for 2h, manganese slag slurry is obtained.

[0043] Example 9: Application Example 1: The mass ratio of metallurgical slag waste alkali material (dry material) to phosphogypsum (dry material) is 2:100. Take 200g of phosphogypsum and add the corresponding amount of steel slag, magnesium slag, and manganese slag-based waste alkali material slurry from Example 1, Example 2, or Example 3, which are defined as steel slag-based waste alkali material, magnesium slag-based waste alkali material, and manganese slag-based waste alkali material, respectively. Mechanically stir at 100r / min for 1 hour, then stop stirring and let it stand to solidify for 4 hours.

[0044] As can be seen, the processed phosphogypsum is in a semi-dry, light gray granular state with a particle size of 0.1–0.8 mm.

[0045] Comparative Example 1: The mass ratio of steel slag, magnesium slag, and manganese slag (dry material) to phosphogypsum (dry material) is 2:100. Take 200g of phosphogypsum and add the corresponding amount of steel slag, magnesium slag, and manganese slag slurry from Examples 6, 7, or 8. Mechanically stir at 100r / min for 1 hour, then stop stirring and let it stand to solidify for 4 hours.

[0046] As can be seen, the processed phosphogypsum is in a semi-dry, light gray granular state with a particle size of 0.1–0.8 mm.

[0047] The phosphogypsum cured under the two different treatment methods were leached with pure water. According to the national standard for the determination of total phosphorus in water (GB 11893-1989), the initial and post-treatment concentrations of soluble phosphorus in the phosphogypsum were determined using a spectrophotometer. According to the national standard for the detection of fluoride ions in water (GB 11894-2014), the initial and post-treatment concentrations of soluble fluoride in the phosphogypsum were determined using ion chromatography. The initial and post-treatment pH values ​​of the leachate were measured using a pH meter. The experimental results are shown in Table 1 below. Table 1. Phosphorus and fluorine content and pH value in phosphogypsum before and after curing using different methods. According to GB 8978-1996 Integrated Wastewater Discharge Standard and GB 18599-2020 Pollution Control Standard for Storage and Filling of General Industrial Solid Waste, as shown in Table 1 above, if only the basic phosphorus and fluoride removal capabilities of metallurgical slag itself are used, the pH value of phosphogypsum and soluble phosphorus and fluoride can be partially neutralized, but the effect is extremely limited.

[0048] The magnesium slag-based waste alkali material prepared in Example 2, when used to treat phosphogypsum according to the above scheme, can simultaneously meet the purification standards of: soluble phosphorus below 0.5 mg / L, soluble fluoride below 10 mg / L, and pH value between 6 and 9. Although the steel slag and manganese slag prepared in Examples 1 and 3 have relatively limited effects, they still have certain significance in solid waste treatment and environmental management, and in preventing secondary pollution.

[0049] Example 10: Application Example 2: The mass ratio of dry magnesium slag-based waste alkali material to phosphogypsum is 2:100. Take 200g of phosphogypsum and add the corresponding amount of magnesium slag-based waste alkali material slurry from Examples 2, 4, or 5, respectively, and define them as magnesium slag-based waste alkali material-1, magnesium slag-based waste alkali material-2, and magnesium slag-based waste alkali material-3. Mechanically stir at 100r / min for 1h, then stop stirring and let it stand to solidify for 8h.

[0050] As can be seen, the processed phosphogypsum is in a semi-dry, light gray granular state with a particle size of 0.1–0.8 mm.

[0051] Comparative Example 2: The mass ratio of magnesium slag to phosphogypsum is 2:100. Take 200g of phosphogypsum and add the corresponding amount of magnesium slag slurry from Example 7. Stir mechanically at 100r / min for 1h, then stop stirring and let it stand to solidify for 8h.

[0052] As can be seen, the processed phosphogypsum is in a semi-dry, light gray granular state with a particle size of 0.1–0.8 mm.

[0053] The phosphogypsum cured under the two different treatment methods were leached with pure water. According to the national standard for the determination of total phosphorus in water (GB 11893-1989), the initial and post-treatment concentrations of soluble phosphorus in the phosphogypsum were determined using a spectrophotometer. According to the national standard for the detection of fluoride ions in water (GB 11894-2014), the initial and post-treatment concentrations of soluble fluoride in the phosphogypsum were determined using ion chromatography. The initial and post-treatment pH values ​​of the leachate were measured using a pH meter. The experimental results are shown in Table 2 below. Table 2. Phosphorus and fluorine content and pH value in phosphogypsum before and after curing using different methods. In Example 9, the magnesium slag-based composite alkali showed the best effect in the harmless treatment of phosphogypsum. In this example, the magnesium slag composite calcium oxide showed the best effect, and the magnesium slag composite magnesium oxide and magnesium slag composite alumina also showed relatively good effects.

[0054] Compared to Example 9, this embodiment has a longer curing time for phosphorus and fluoride, resulting in lower concentrations of soluble phosphorus and soluble fluoride in the final phosphogypsum. However, using only magnesium slag (Example 7) cannot reduce the soluble phosphorus in phosphogypsum to below 0.5 mg / L or the soluble fluoride to below 10 mg / L. The magnesium slag-based waste alkali material prepared by this method using magnesium slag and calcium oxide can effectively control the three indicators of soluble phosphorus, soluble fluoride, and pH value to meet the standards. Magnesium slag combined with composite magnesium oxide and aluminum oxide can also effectively bring the three indicators of soluble phosphorus, soluble fluoride, and pH value close to meeting the standards.

[0055] Finally, it should be noted that the above embodiments are only used to explain and illustrate the technical solutions of the present invention, and do not constitute a limitation on its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention. Such modifications or substitutions should not be considered as departing from the scope of the technical solutions of the present invention.

Claims

1. A method for preparing a metallurgical slag alkali material for the harmless treatment of phosphogypsum, characterized in that... Includes the following steps: (1) Mix metallurgical slag and metal oxide at a mass ratio of (3-1.5):1, and mechanically stir at a speed of ≥60 r / min for ≥30 min to obtain the dry basis of waste alkali material; (2) Add water to the dry base of the waste alkali material obtained in step (1), and control the mass ratio of metallurgical slag: metal oxide: water to be (3~1.5):1:(10~20). Stir mechanically at a speed of ≥60r / min and pre-activate for 1~2h to convert the metal oxide into highly active hydroxide, and obtain a slurry product that can simultaneously solidify soluble phosphorus and fluorine in phosphogypsum and adjust the pH value to neutral. The metallurgical slag is selected from at least one of steel slag, magnesium slag, and manganese slag; the metal oxide is selected from at least one of calcium oxide, magnesium oxide, and aluminum oxide.

2. The preparation method according to claim 1, characterized in that: In step (1), the metallurgical slag is magnesium slag and the metal oxide is calcium oxide, wherein the mass ratio of magnesium slag to calcium oxide is 3:

1.

3. The preparation method according to claim 1, characterized in that: In step (1), the metallurgical slag is magnesium slag, and the metal oxide is aluminum oxide or magnesium oxide, wherein the mass ratio of magnesium slag to aluminum oxide is 1:0.6, or the mass ratio of magnesium slag to magnesium oxide is 1:0.

375.

4. The preparation method according to claim 1, characterized in that: In step (1), the metallurgical slag is steel slag or manganese slag, and the metal oxide is calcium oxide, wherein the mass ratio of steel slag to calcium oxide is 1:0.5, or the mass ratio of manganese slag to calcium oxide is 1.5:0.

5.

5. The application of the metallurgical slag waste alkali material according to any one of claims 1 to 4 in the harmless treatment of phosphogypsum, characterized in that... Includes the following steps: The slurry product is added to phosphogypsum at a mass ratio of waste alkali material dry basis to phosphogypsum dry basis of 1:100 to 2:

100. After mechanical stirring for ≥1 hour, it is allowed to stand and solidify for ≥4 hours so that the treated phosphogypsum meets the following requirements: soluble phosphorus concentration ≤0.5mg / L; soluble fluorine concentration ≤10mg / L; pH value 6 to 9.

6. The application as described in claim 5, characterized in that: The mass ratio of the dry basis of the waste alkali material to the dry basis of phosphogypsum is 2:

100.

7. The application as described in claim 5, characterized in that: The static curing time is 4 to 8 hours.

8. The application as described in claim 5, characterized in that: The pH value of the treated phosphogypsum is 7-8.

9. The application as described in claim 5, characterized in that: The treated phosphogypsum is a semi-dry, light gray granular substance with a particle size of 0.1–0.8 mm.

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