Phosphogypsum and strontium residue synergistic harmless treatment mixed residue and harmless treatment method and application

Abstract

The present application relates to the technical field of waste residue resource utilization, and particularly relates to a kind of phosphogypsum and strontium residue synergic harmless treatment mixed slag and harmless treatment method and application, by the reasonable proportioning mixing of phosphogypsum and strontium residue, and the addition of oxidizing agent is combined, by stirring aging, so that the mixture obtained by mixing in the mixture S 2‑ Transformed into SO4 2‑ , reduce the content of S 2‑ In the mixture, at the same time, free SO4 2‑ In phosphogypsum and transformed SO4 2‑ Can be combined with Sr 2+ Generation of insoluble strontium sulfate, F ‑ In phosphogypsum and calcium ion in strontium residue combine to generate calcium fluoride and realize solidification, reduce the leaching rate of sulfide, sulfate, phosphate, fluoride, Sr 2+ Etc. in the mixture, reduce the leaching toxicity of the mixture formed by mixing phosphogypsum and strontium residue.

Description

Technical Field

[0001] This invention relates to the field of waste residue resource utilization technology, and in particular to a method and application of harmless treatment of mixed residue of phosphogypsum and strontium slag in synergistic harmless treatment. Background Technology

[0002] Phosphogypsum is an industrial solid waste produced in the wet-process phosphoric acid production process. Its main component is calcium sulfate dihydrate, and it also contains arsenic, cadmium, lead, chromium, mercury, thallium, and fluorine. - It contains harmful elements and is acidic, classifying it as a Class II general industrial solid waste. Currently, the annual production of phosphogypsum exceeds 70 million tons, but its resource utilization rate is low, leading to the need for large-scale stockpiling. This not only damages the ecological environment but also occupies a significant amount of land. Therefore, how to harmlessly treat phosphogypsum and then utilize it as a resource has become a pressing technical challenge for those skilled in the art.

[0003] Currently, some research has been conducted on the technology for the harmless treatment and resource utilization of phosphogypsum. For example, patent application number 202311251023.5 discloses a technical solution for preparing a phosphogypsum-barium slag mixture through the synergistic harmless treatment of phosphogypsum and barium slag. This involves grinding phosphogypsum, biomass, minerals, and peroxides to prepare a composite phosphogypsum raw material. Then, a biological treatment method is used, incorporating phosphate-solubilizing fungi and combining this with physical adsorption treatment. This effectively immobilizes harmful pollutants such as soluble phosphorus, eutectic phosphorus, and fluorides from the barium slag and phosphogypsum, achieving green and harmless synergistic treatment of barium slag and phosphogypsum, and reducing the hazards caused by phosphogypsum stockpiling.

[0004] For example, patent application number 201910149830.3 discloses a method for the synergistic harmless treatment of electrolytic manganese slag and phosphogypsum. The method involves uniformly mixing electrolytic manganese slag and phosphogypsum, preparing a slurry according to the solid-liquid ratio, and then adding an alkaline agent (one or more of calcined raw materials, calcium oxide, and magnesium oxide) to adjust the pH of the slurry to ensure that the pH value of the slurry is 6-9, thus obtaining a mixture. The mixture is then transported to a storage site or used for other purposes to reduce the hazards caused by the storage of phosphogypsum. At the same time, it achieves the fixation of soluble fluorine, phosphorus, manganese, and ammonia nitrogen in electrolytic manganese slag and phosphogypsum, simplifying the process flow.

[0005] It is evident that existing treatment methods can mitigate the hazards of phosphogypsum stockpiling to some extent, solidify harmful elements, reduce the potential and probability of secondary pollution caused by phosphogypsum stockpiling, and enable resource utilization of the treated phosphogypsum, thereby reducing the stockpile volume. However, for large-scale phosphogypsum stockpiles, multiple treatment technologies are needed to accelerate phosphogypsum disposal and achieve a rapid reduction in stockpile volume. Furthermore, the comprehensive harmless treatment and resource utilization of phosphogypsum remains a long-term focus for those skilled in the art.

[0006] Strontium slag is a waste residue produced during the carbothermic reduction of celestite to prepare industrial strontium carbonate. It is a water-quenched slag, alkaline in nature, and belongs to Class II general industrial solid waste. Strontium slag contains acid-soluble and water-soluble strontium ions, S... 2- The presence of harmful components such as strontium slag necessitates its harmless treatment before it can be utilized for resource recovery. Otherwise, it will cause secondary environmental pollution and hinder the resource recovery of strontium slag.

[0007] In summary, based on the current technological status of harmless treatment of phosphogypsum and strontium slag, our research team has jointly considered the harmless treatment of phosphogypsum and strontium slag, and constructed a technical approach for the synergistic harmless treatment of phosphogypsum and strontium slag, providing a new approach for the synergistic harmless treatment of strontium slag and phosphogypsum. Summary of the Invention

[0008] Given that both phosphogypsum and strontium slag are industrial by-product solid wastes containing a large number of harmful elements, they require harmless treatment before storage or resource utilization; otherwise, they will cause secondary pollution to the environment. Furthermore, phosphogypsum is acidic while strontium slag is alkaline. Mixing them utilizes the principle of acid-base neutralization to effectively solidify harmful elements such as strontium, sulfur, phosphorus, and fluorine, reducing the risks associated with resource utilization. This invention provides a method and application for the harmless treatment of mixed slag from phosphogypsum and strontium slag through appropriate processing technology and proportion control. This method helps improve the resource utilization efficiency of phosphogypsum and strontium slag and reduces the environmental pollution caused by the storage or resource utilization of solid wastes such as phosphogypsum and strontium slag.

[0009] The specific technical solution is as follows:

[0010] One of the objectives of this invention is to provide a method for the synergistic harmless treatment of phosphogypsum and strontium slag. On a dry basis, phosphogypsum and strontium slag are mixed in a mass ratio of 5-15:1, then an oxidant solution is added, stirred and mixed evenly, and aged.

[0011] By rationally mixing phosphogypsum and strontium slag, and adding an oxidant, followed by stirring and aging, the resulting mixture was found to contain higher levels of sulfur (S). 2- Converted into SO4 2-Reduce S in the mixture 2- The content of SO4 in phosphogypsum, and at the same time, the free SO4 in phosphogypsum 2- and the converted SO4 2- Able to be with Sr 2+ The F in phosphogypsum combines to form insoluble strontium sulfate. - It solidifies by combining with calcium ions in strontium slag to form calcium fluoride, thereby reducing the levels of sulfides, sulfates, phosphates, fluorides, and Sr in the mixture. 2+ The leaching rate of phosphogypsum and strontium residue was reduced, thereby decreasing the leaching toxicity of the mixture.

[0012] In order to improve the leaching toxicity of the mixture during the stacking and aging process, the mass ratio of the phosphogypsum to the strontium slag is preferably 5-11:1.

[0013] More preferably, the mass ratio of the phosphogypsum to the strontium slag is 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or 11:1.

[0014] To ensure sufficient contact and improve the effectiveness of the harmless treatment, the aging time is preferably at least 1 day. More preferably, it is 1 day, 3 days, 5 days, 10 days, 15 days, or 90 days.

[0015] In order to ensure that the solution retains its oxidizing properties and achieve S 2- Converted into SO4 2- Meanwhile, in order to ensure that the oxidant is evenly dispersed in the mixed slag and reduce the sulfur content in the mixture, 2- For the purpose of determining the content of the oxidant, preferably, the oxidant solution is prepared by dissolving at least one of hydrogen peroxide, sodium hypochlorite, and potassium permanganate.

[0016] More preferably, the mass concentration of the oxidant solution is 5-10%.

[0017] More preferably, the amount of oxidant solution added is 10-20% of the mass of the strontium slag.

[0018] To ensure uniform mixing after the oxidant solution is added and to improve S 2- Converted into SO4 2- Reduce S in the mixture 2- To optimize the content of [specific ingredient], preferably, the stirring rate for mixing is 50-180 r / min, and the stirring time is 30-60 min. More preferably, the stirring rate for mixing is 120 r / min, and the stirring time is 60 min.

[0019] The second objective of this invention is to provide a mixed residue for the synergistic harmless treatment of phosphogypsum and strontium slag obtained by the above method.

[0020] The third objective of this invention is to provide a synergistic harmless treatment mixture of phosphogypsum and strontium slag obtained by the above method for use in the preparation of building materials or as an ecological restoration material.

[0021] Compared with the prior art, the technical effects of this invention are reflected in:

[0022] This invention utilizes a properly controlled mixing ratio of acidic phosphogypsum and alkaline strontium slag, combined with the addition of an oxidant solution, to achieve synergistic harmless treatment through stirring and aging. This process not only brings the pH of the mixture close to neutral but also allows the free acids (sulfuric acid, phosphoric acid) in the phosphogypsum to form insoluble strontium salts with the acid-soluble and water-soluble strontium ions in the strontium slag, thus achieving solidification. Simultaneously, the fluoride ions in the phosphogypsum can combine with the calcium ions present in the strontium slag for solidification, reducing the leaching rates of sulfides, phosphates, fluorides, strontium ions, and sulfates. This reduces the leaching toxicity of the mixture, minimizing the potential for secondary pollution from stockpiling or resource utilization. The mixture can be used as a building material or ecological restoration material; it can also be used in the preparation of building materials or ecological restoration materials, contributing to increased disposal of industrial solid wastes such as phosphogypsum and strontium slag and reducing stockpiling.

[0023] This invention creates a method that can coat and solidify the small amounts of harmful elements such as arsenic, thallium, lead, mercury, and thallium remaining in phosphogypsum during the formation of strontium sulfate and other strontium salts. Furthermore, it utilizes the insolubility of strontium sulfate and other strontium salts to achieve solidification, so that phosphogypsum and strontium slag can be converted into low-hazard industrial solid waste after being mixed in an appropriate mass ratio, thereby reducing the potential for secondary pollution to the environment from stockpiling or resource utilization.

[0024] The process of this invention is simple and easy to industrialize and promote. Attached Figure Description

[0025] In order to enable those skilled in the art to fully understand the technical solution of the present invention, the present invention is now described in conjunction with the technical solution content and the accompanying drawings.

[0026] Figure 1 A process flow diagram is provided for this invention. Detailed Implementation

[0027] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0028] like Figure 1 As shown, in some embodiments, the method for the synergistic harmless treatment of phosphogypsum and strontium slag involves mixing phosphogypsum and strontium slag at a mass ratio of 5-15:1 (dry basis), for example: 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc., then adding an oxidant solution, stirring and mixing thoroughly, and aging. By properly controlling the mass ratio of phosphogypsum and strontium slag, combined with the addition of an oxidant solution and stirring and aging treatment, the S content in the strontium slag is reduced. 2- The strontium ions are converted into sulfate ions. The converted sulfate ions and the free acid ions (sulfate and phosphate) in phosphogypsum can form insoluble strontium sulfate and strontium phosphate salts with strontium ions in strontium slag, thereby solidifying the strontium ions, reducing the leaching rate of free acid in phosphogypsum and strontium ions in strontium slag, and improving the harmless treatment effect of phosphogypsum and strontium slag.

[0029] This invention creates a process where, after phosphogypsum and strontium slag are mixed in an appropriate ratio, an oxidant solution is added and stirred for aging. This process enables the combination of fluoride ions and calcium ions, achieving the solidification of fluoride ions. Furthermore, it utilizes the formation process of strontium sulfate and strontium phosphate to encapsulate other harmful element ions, and leverages the insolubility of strontium salts such as strontium sulfate and strontium phosphate to achieve solidification. This reduces the water solubility and leaching of the phosphogypsum and strontium slag mixture during storage, improves the harmless treatment effect, and reduces storage risks.

[0030] like Figure 1 As shown, in some embodiments, the phosphogypsum is pulverized and passed through an 80-100 mesh sieve to prepare phosphogypsum powder; the strontium slag is pulverized and passed through an 80-100 mesh sieve to prepare strontium slag powder. The phosphogypsum powder and strontium slag powder are then mixed in an appropriate mass ratio, and an oxidizing agent solution is added and the mixture is stirred and aged. This process helps to expose harmful elements and free acid ions encapsulated in the phosphogypsum, while simultaneously exposing harmful elements and sulfur encapsulated in the strontium slag. 2-Ions and other substances are exposed, and then mixed with an appropriate mass ratio. After adding an oxidant solution and stirring for aging, the formation of insoluble strontium salts (strontium sulfate, strontium phosphate) is promoted, thereby encapsulating harmful elements, reducing the leaching rate of harmful components in the mixture, and reducing the pollution capacity of the phosphogypsum and strontium slag mixture for stockpiling or resource utilization.

[0031] In some embodiments, the oxidant solution is prepared by dissolving at least one of hydrogen peroxide, sodium hypochlorite, and potassium permanganate. The mass concentration of the oxidant solution is 5-10%. The amount of the oxidant solution added is 10-20% of the mass of the strontium slag.

[0032] In some embodiments, the stirring rate is 120 r / min and the stirring time is 60 min.

[0033] In some embodiments, the aging time is at least 1 day, for example: 1 day, 5 days, 10 days, 15 days, 90 days, etc.

[0034] To better verify the technical effects of this invention, the research team conducted the following experimental studies. The samples prepared during the experiments and the leaching toxicity test data of the obtained samples are described below:

[0035] The phosphogypsum used was sourced from a wet-process phosphoric acid production enterprise in Guizhou Province. Its main chemical composition and moisture content are shown in Table 1 below:

[0036] Table 1

[0037]

[0038] The strontium slag used was sourced from a strontium carbonate production enterprise in Guizhou Province. Its main chemical element composition and moisture content are shown in Table 2 below:

[0039] Table 2

[0040]

[0041] The oxidizing agent solution used can be hydrogen peroxide, sodium hypochlorite, or potassium permanganate solution with a mass concentration of 5-10%. Sodium hypochlorite solution was used in the following examples.

[0042] Experiment 1: Study on the effect of different mass ratios of phosphogypsum and strontium slag on leaching toxicity.

[0043] Phosphogypsum and strontium slag are crushed separately and passed through a 100-mesh sieve to obtain phosphogypsum powder and strontium slag powder. On a dry basis, the phosphogypsum powder and strontium slag powder are mixed according to the mass ratio in Table 3 below, stirred at 120 r / min for 60 min, and then aged to obtain harmless mixed slag.

[0044] The obtained harmless treated mixed residue was used to prepare leachate using the "Horizontal Oscillation Method for Leaching Toxicity of Solid Waste" (HJ557-2010). The pH value and the levels of sulfide (mg / L), sulfate (mg / L), phosphate (mg / L), fluoride (mg / L), and Sr in the leachate were then measured. 2+ The content (mg / L) is shown in Table 3 below:

[0045] A: This is the mass ratio of phosphogypsum to strontium slag;

[0046] B: Aging time, d;

[0047] C: Leachate test indicators.

[0048] Table 3

[0049]

[0050] Table 3 shows that: (1) As the mass ratio of phosphogypsum to strontium slag gradually increases, the pH value gradually decreases. The optimal mass ratio of phosphogypsum to strontium slag is 5–11:1, and within this mass ratio, the pH of the mixed slag is between 6 and 9. (2) As the mass ratio of phosphogypsum to strontium slag gradually increases, the leaching concentrations of sulfate and phosphate gradually increase. Within the entire implemented mass ratio range, the sulfate leaching concentration in the mixed slag is less than 100 mg / L. When the mass ratio is less than 11:1, the phosphate leaching concentration is <0.5 mg / L, which meets the Class I standard limit of the Integrated Wastewater Discharge Standard (GB8978-1996). (3) As the mass ratio of phosphogypsum to strontium slag gradually increases, the leaching concentration of fluoride gradually increases, but the change is not significant. Within the entire implemented mass ratio range, the sulfate leaching concentration in the mixed slag is less than 10 mg / L, which meets the Class I standard limit of the Integrated Wastewater Discharge Standard (GB8978-1996). (4) As the mass ratio of phosphogypsum to strontium slag gradually increases, the leaching concentration of strontium ions gradually decreases. When the mass ratio is ≥5:1, the leaching concentration of strontium ions in the mixed slag is <9mg / L. (5) As the mass ratio of phosphogypsum to strontium slag gradually increases, the leaching concentration of sulfides shows a decreasing trend. However, the concentration of sulfides in the leachate of mixed slag with different proportions is higher than 1mg / L, which cannot meet the first-class standard limit of the "Integrated Wastewater Discharge Standard" (GB8978-1996). (6) As the aging time increases, the stability of the harmless treatment mixed residue gradually increases. However, as can be seen from Examples 1 to 10, when the mass ratio of phosphogypsum to strontium slag is 4-8:1, the sulfide leaching concentration decreases as the aging time reaches 15 days. When the mass ratio of phosphogypsum to strontium slag is 3:1 and when the mass ratio of phosphogypsum to strontium slag is 9-11:1, the sulfide leaching concentration increases as the aging time reaches 15 days.

[0051] In summary, when the mass ratio of phosphogypsum to strontium slag is controlled at 5-11:1, the mixed slag exhibits the optimal pH range and a low leaching concentration of strontium ions (below 10 mg / L). Strictly controlling the mass ratio of phosphogypsum to strontium slag, with prolonged stockpiling time, helps reduce the leaching capacity of components such as sulfides, sulfates, phosphates, and fluorides, further increasing the amount of phosphogypsum that can be utilized and accelerating its disposal.

[0052] Experiment 2: Study on the effect of different aging times on leaching toxicity.

[0053] Based on Example 1 in Experiment 1, with other parameters unchanged, the aging times were 1 day, 5 days, 10 days, 15 days, and 90 days, respectively. The test results are shown in Table 4.

[0054] Table 4

[0055]

[0056] Table 4 shows that as the aging time increases, the pH and strontium ion concentrations in the leachate remain stable; sulfate, phosphate, and fluoride concentrations all show a decreasing trend. Sulfide concentrations initially increase and then decrease, but after 90 days of aging, the sulfide concentration in the leachate is still higher than 1 mg / L, failing to meet the Class I standard limit of the "Integrated Wastewater Discharge Standard" (GB8978-1996). Therefore, further measures, such as adding oxidants, are needed to reduce the sulfide concentration.

[0057] Experiment 3: Effect of different oxidant concentrations on the leaching concentration of sulfides in mixed slag.

[0058] Based on Example 1 in Experiment 1, with other parameters unchanged, the oxidant used was sodium hypochlorite solution, and its mass concentrations were 0% (water without sodium hypochlorite added based on Example 1), 1%, 3%, 5%, 8%, and 10%, respectively. The amount of oxidant solution added accounted for 15% of the mass of strontium slag powder. The sulfide leaching concentration was measured, and the results are shown in Table 5.

[0059] Table 5

[0060]

[0061] Table 5 shows that the concentration of sulfides in the leachate decreases with increasing sodium hypochlorite solution concentration. When the oxidant concentration is greater than 5%, the concentration of sulfides in the leachate is less than 1 mg / L, which meets the Class I standard limit of the Integrated Wastewater Discharge Standard (GB8978-1996). Therefore, when preparing mixed slag using the synergistic harmless treatment of phosphogypsum and strontium slag, adding an oxidant can further reduce the leaching of sulfides and improve the harmless stability of the mixed slag.

[0062] Other matters not covered in this invention can be addressed by referring to existing technology or common knowledge known to those skilled in the art, and by conventional technical means. For example, how to prepare a sodium hypochlorite solution as an oxidizing agent; or how to prepare an oxidizing agent solution using potassium permanganate or hydrogen peroxide, etc. The purpose of adding the oxidizing agent solution in this invention is to utilize its oxidizing properties. Therefore, when selecting the solute components for preparing the oxidizing agent solution, as long as they can maintain their oxidizing properties after preparation, and are able to neutralize sulfur dioxide... 2- Converted into SO4 2- If it cannot be selected, then it cannot be selected.

Claims

1. A method for the synergistic harmless treatment of phosphogypsum and strontium slag, characterized in that, On a dry basis, phosphogypsum and strontium slag are mixed at a mass ratio of 5-11:1, then an oxidant solution is added. The mixture is stirred at a speed of 50-180 r / min for 30-60 min until homogeneous, and then aged for at least 1 day to ensure that the resulting mixture contains sufficient sulfur. 2- Converted into SO4 2- Reduce S in the mixture 2- The content of SO4 in phosphogypsum, and at the same time, the free SO4 in phosphogypsum 2- and the converted SO4 2- Able to be with Sr 2+ The F in phosphogypsum combines to form insoluble strontium sulfate. - It solidifies by combining with calcium ions in strontium slag to form calcium fluoride; The oxidant solution is prepared by dissolving at least one of hydrogen peroxide, sodium hypochlorite, and potassium permanganate in a solution with a mass concentration of 5-10%; the amount of the oxidant solution added accounts for 10-20% of the strontium slag.

2. The method for the synergistic harmless treatment of phosphogypsum and strontium slag as described in claim 1, characterized in that, The mass ratio of the phosphogypsum to the strontium slag is 5:1, 6:1, 7:1, 8:1, 9:1, 10:1 or 11:1.

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