A reagent for immobilizing beryllium and thallium in solid waste and its application method

Abstract

This application relates to a reagent and method for immobilizing beryllium and thallium in solid waste, belonging to the field of solid waste treatment technology. The reagent consists of a soluble sulfide and a soluble phosphate, wherein the mass ratio of the soluble sulfide to the soluble phosphate is 1:0.5 to 1:2. The method of application utilizes the synergistic effect of the soluble sulfide and soluble phosphate, optimizing the reagent ratio and process parameters to achieve simultaneous solidification of beryllium and thallium under ambient temperature and pressure conditions. After treatment, the thallium leaching concentration is <5 μg / L and the beryllium concentration is <1 μg / L, exceeding national standards. The resulting solidified body exhibits high stability and low disposal costs, effectively avoiding the risk of secondary leaching, significantly reducing the environmental risk of beryllium and thallium-containing solid wastes such as lithium smelting slag, achieving harmless disposal, and effectively solving the pollution problem of such wastes.

Description

Technical Field

[0001] This application belongs to the field of solid waste treatment technology, specifically relating to a reagent for immobilizing beryllium and thallium in solid waste and its application method. Background Technology

[0002] Beryllium (Be) and thallium (Tl) are highly toxic, carcinogenic, and teratogenic heavy metals. Their environmental release poses serious ecological and health risks, thus necessitating effective treatment of solid waste containing these elements. Beryllium-thallium-containing solid wastes come from diverse sources and have complex compositions. Improper disposal can easily lead to the release and migration of beryllium and thallium through rainwater leaching. Lithium smelting slag is a typical beryllium-thallium-containing solid waste generated during lithium extraction from lithium ore. This slag is rich in highly toxic beryllium (Be, content 50~1000 μg / kg) and thallium (Tl, content 10~500 μg / kg). Typical chemical compositions include 20~60 wt.% CaSO4, 5~30 wt.% (Na,K)(Si3Al)O8, 10~20 wt.% (Ca,Na)(Si,Al)4O8, 1~5 wt.% Fe2O3, and 1~5 wt.% CaF2. Existing technologies struggle to achieve stable solidification of such solid wastes, especially under acidic conditions. The leaching concentrations of beryllium and thallium often exceed the limits specified in the "Standard for Pollution Control of Solid Waste Landfill" (GB 18598-2019), with thallium having a particularly high leaching limit. This results in significant environmental pollution risks and fails to meet the requirements for harmless disposal. Therefore, developing efficient and stable solidification technologies and reagents is crucial for the harmless disposal of beryllium- and thallium-containing solid wastes such as lithium smelting slag.

[0003] Currently, the fixation technology for beryllium and thallium in solid waste still faces many challenges. Traditional methods, such as cement solidification or single sulfide fixation, have low fixation efficiency, while chelating agent trapping methods suffer from drawbacks such as demanding operating conditions and high costs. Many fixation methods require high temperatures or expensive reagents to achieve beryllium and thallium fixation, resulting in high energy consumption and treatment costs. Furthermore, the leaching concentrations of beryllium and thallium in the solidified products often fail to meet national standards. In addition, existing reagent combinations lack specificity and cannot efficiently form stable mineral phases, thus limiting their industrial application.

[0004] Existing research has disclosed some specific solutions, but all of them have obvious limitations: CN120382038A discloses a method for treating lithium-containing thallium tailings from lithium mica extraction, which employs acid rinsing and nano-iron adsorption processes. Although this method can efficiently remove thallium (leaching toxicity <0.1mg / L, removal rate >99%), it cannot simultaneously fix beryllium. Furthermore, nano-iron materials are expensive, and the acid rinsing wastewater increases treatment costs and environmental risks.

[0005] CN120346793A discloses an adsorbent for purifying thallium-containing wastewater and its application, which develops a kaolin-sodium alginate aerogel adsorbent suitable for purifying thallium-containing wastewater. However, it has limited effectiveness in fixing unstable thallium in solid waste residues, thus limiting its applicability.

[0006] CN120309273A discloses a non-fired lightweight aggregate with high lithium slag content and a method for preparing it by synergistic use of lepidolite slag and spodumene slag. By synergistically utilizing lepidolite slag and spodumene slag to prepare non-fired lightweight aggregate, the dry basis content of lithium slag can be increased to more than 80% and beryllium can be effectively solidified. However, this scheme does not involve the fixation treatment of thallium.

[0007] CN118558703A discloses a method for the harmless treatment of lithium slag to remove thallium and beryllium. It proposes a method combining ball milling mechanical activation and chemical agents to treat lithium slag. It points out that ball milling can increase the specific surface area and promote fixation, but the amount of agent added is as high as 5.0 wt%, and the final leaching concentrations of thallium and beryllium (Tl<10μg / L, Be<20μg / L) are still difficult to stably meet the strict standard of thallium (Tl<5μg / L).

[0008] CN121161019A discloses a method for deep removal of beryllium and thallium from lepidolite smelting slag. Through acid leaching, complexation, precipitation and adsorption steps, it can achieve efficient deep removal of beryllium and thallium and make the purified lithium slag meet environmental protection standards. However, this method has a complex process, strong reagent dependence, large amount of reagent added and may generate acidic wastewater, resulting in high treatment costs. In addition, it is only applicable to lepidolite smelting slag and has a limited scope of application.

[0009] In summary, existing technologies either only target one of the elements, beryllium or thallium, or suffer from problems such as insufficient fixation efficiency, poor stability, high cost, or complex processes. Currently, there is a lack of an economical and practical method that can simultaneously, efficiently, and stably fix beryllium and thallium in lithium smelting slag under mild conditions. Summary of the Invention

[0010] In view of this, this application provides a reagent and method for immobilizing beryllium and thallium in solid waste. This method utilizes the synergistic effect of soluble sulfides and soluble phosphates, optimizes the reagent ratio and process parameters, and achieves simultaneous solidification of beryllium and thallium under ambient temperature and pressure conditions. After treatment, the thallium leaching concentration is <5 μg / L and the beryllium concentration is <1 μg / L, which is better than the national standard requirements. The resulting solidified body has high stability and low disposal cost, effectively avoiding the risk of secondary leaching, significantly reducing the environmental risk of beryllium and thallium-containing solid wastes such as lithium smelting slag, achieving harmless disposal, and effectively solving the pollution problem of such wastes.

[0011] Firstly, this application provides a reagent for immobilizing beryllium and thallium in solid waste, comprising a soluble sulfide and a soluble phosphate, wherein the mass ratio of the soluble sulfide to the soluble phosphate is 1:0.5 to 1:2. This application utilizes a synergistic mineralization mechanism of the two reagents to achieve efficient immobilization of beryllium and thallium. In the soluble sulfide, sulfur combines with thallium to form a thallium sulfide mineral phase, while the soluble phosphate combines with beryllium and thallium to form insoluble phosphates such as NaBePO4 or TlCaPO4. This mechanism is not only designed specifically for the chemical properties of the two elements but also utilizes the inherent calcium and sodium elements in solid waste (such as lithium smelting slag) as mineralization inducers, promoting the co-conversion of beryllium and thallium into thermodynamically stable inert minerals under ambient temperature and pressure conditions, thereby efficiently immobilizing the two elements. By adjusting the mass ratio within the above-mentioned preferred range, the simultaneous solidification of beryllium and thallium can be better achieved, overcoming the limitation that a single agent can only target one element. Furthermore, the solidified body formed has high stability and can effectively inhibit the secondary leaching of heavy metals under acidic conditions, significantly reducing environmental risks.

[0012] In some embodiments, the soluble sulfide includes at least one of sodium sulfide, potassium sulfide, and ammonium sulfide. Sodium sulfide, potassium sulfide, and ammonium sulfide are all commonly used industrial reagents with good water solubility and high reactivity, ensuring uniform release of sulfur ions and improving thallium fixation efficiency. Moreover, these compounds are widely available, inexpensive, safe to handle, and easy to mix and control during actual treatment, further enhancing the long-term stability of the solidified body and effectively inhibiting the secondary leaching of heavy metals under acidic conditions. This provides an efficient and economical solution for the harmless disposal of thallium-containing solid waste.

[0013] In some embodiments, the soluble phosphate includes at least one of sodium phosphate, potassium phosphate, and ammonium phosphate. Sodium phosphate, potassium phosphate, and ammonium phosphate are all common industrial reagents with good water solubility and high reactivity, ensuring uniform release of phosphate ions and improving the stability and consistency of beryllium fixation efficiency. These compounds are widely available, low in cost, safe to handle, and easy to precisely control during the mixing process, further enhancing the long-term chemical stability of the solidified body, effectively inhibiting secondary dissolution of beryllium under acidic conditions, reducing environmental risks, and providing an efficient, economical, and easily scalable solution for the harmless disposal of beryllium-thallium-containing solid waste.

[0014] Secondly, this application also provides a method for using an agent to fix beryllium and thallium in solid waste, comprising the following steps: S1, mixing solid waste with the agent to obtain a solid mixture; wherein the average particle size of the solid waste is ≤400μm, and the solid waste includes beryllium and thallium; S2, adding water to the solid mixture to obtain a solid-liquid mixture for reaction; the solid-liquid ratio of the solid-liquid mixture is 1:0.5~1:2; S3, separating the solid-liquid mixture after reaction to obtain a solidified body; the solidified body is the product of beryllium and thallium fixation. Based on the synergistic mineralization mechanism of the two types of agents, the inherent calcium, sodium, and other elements in solid waste (such as lithium smelting slag) are used as mineralization inducers to promote the co-conversion of beryllium and thallium into thermodynamically stable inert minerals under normal temperature and pressure conditions, thereby efficiently fixing the two elements. Controlling the solid-liquid ratio within the above-mentioned preferred range ensures uniform distribution of the reaction medium, promotes sufficient ion contact and migration, and enhances the integrity and efficiency of the mineralization reaction. A reasonable solid-liquid ratio can avoid problems such as waste of reagents or insufficient reaction, ensure the long-term chemical stability of the solidified body, effectively inhibit the secondary dissolution of beryllium and thallium under acidic conditions, and reduce environmental risks.

[0015] In some embodiments, the mass percentage of the agent is 0.2~1.0 wt.% based on 100% of the mass of the solid mixture. By controlling the mass percentage of the agent within the above-mentioned preferred range, it is possible to ensure that the soluble sulfide and soluble phosphate reach the optimal concentration balance in the solid waste, ensuring uniform distribution of the agent and sufficient contact with beryllium and thallium ions. This avoids the problem of incomplete reaction caused by insufficient or excessive local concentrations, and utilizes the waste components as mineralization inducers to reduce dependence on exogenous agents, thereby fully activating the synergistic mineralization mechanism and achieving efficient and simultaneous solidification of beryllium and thallium.

[0016] In some embodiments, the solid waste is lithium smelting slag, including lepidolite smelting slag and / or spodumene smelting slag; the beryllium element is present in a silicate-bound state, and the thallium element is present in a sulfate-bound state.

[0017] In some embodiments, the beryllium content of the lithium smelting slag is 50~1000 μg / kg, and the thallium content is 10~500 μg / kg. By limiting the beryllium and thallium contents to the above-mentioned preferred ranges, the risk of incomplete fixation due to excessively high beryllium and thallium contents can be avoided, while the waste of reagent resources due to excessively low contents can be prevented, ensuring the sufficiency and economy of the solidification reaction.

[0018] In some embodiments, the lithium smelting slag, based on 100% by mass, contains 20 to 60 wt.% CaSO4; for example, it can be a value within the range of 25.0 wt.%, 35.5 wt.%, 47.0 wt.%, 50.0 wt.%, 52.0 wt.%, 55.0 wt.%, 58.0 wt.%, 60.0 wt.%, or any two of these values, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] In some embodiments, the lithium smelting slag, based on 100% by mass, contains 5 to 30 wt.% (Na,K)(Si3Al)O8; for example, it can be a value within the range of 5.0 wt.%, 10.5 wt.%, 15.0 wt.%, 20.0 wt.%, 25.0 wt.%, 26.5 wt.%, 28.0 wt.%, 30.0 wt.%, or any two of these values, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0020] In some embodiments, the lithium smelting slag, based on 100% by mass, contains 10-20 wt.% (Ca,Na)(Si,Al)4O8; for example, it can be a value within the range of 10.0 wt.%, 10.5 wt.%, 12.5 wt.%, 15.0 wt.%, 15.5 wt.%, 16.0 wt.%, 18.0 wt.%, 20.0 wt.%, or any two of these values, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0021] In some embodiments, the lithium smelting slag, based on 100% by mass, contains 1 to 5 wt.% Fe2O3; for example, it can be a value within the range of 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, 2.5 wt.%, 3.0 wt.%, 3.5 wt.%, 4.0 wt.%, 5.0 wt.%, or any two of these values, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0022] In some embodiments, the lithium smelting slag, based on 100% by mass, contains 1 to 5 wt.% CaF2; for example, it can be a value within the range of 1.0 wt.%, 1.5 wt.%, 2.0 wt.%, 2.5 wt.%, 3.0 wt.%, 3.5 wt.%, 4.0 wt.%, 5.0 wt.%, or any two of these values, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] These components can act as natural mineralization inducers, promoting the formation of stable beryllium phosphate minerals from beryllium and phosphate, and the formation of low-soluble thallium sulfide precipitates from thallium and sulfides, through the synergistic effect of soluble sulfides and phosphates. This achieves efficient and simultaneous fixation of beryllium and thallium. In terms of beneficial effects, this optimized composition enhances the practicality and reliability of the method: the slag's own components ensure the sufficiency and consistency of the mineralization reaction, enhance the long-term chemical stability of the solidified body, and effectively inhibit the secondary leaching of heavy metals under acidic conditions; simultaneously, no additional additives are required, reducing raw material and processing costs. The process is simple and easy to scale up, providing an efficient, economical, and stable technical guarantee for the harmless disposal of lithium smelting slag.

[0024] In some embodiments, the reaction time is 20 to 40 minutes. Regulating the reaction time within the above-mentioned preferred range ensures efficient and simultaneous curing of beryllium and thallium, avoiding inefficiency caused by insufficient or excessive reaction.

[0025] The beneficial effects of this invention are as follows: 1. This application innovatively utilizes the synergistic mineralization effect of soluble sulfides and phosphates to simultaneously and efficiently fix trace amounts of highly toxic elements beryllium and thallium with different properties in solid waste. This overcomes the limitations of traditional methods that can only target single elements, and can cope with different beryllium and thallium content ranges, especially high content cases, highlighting the wide range of reagent selection and greatly improving treatment efficiency and universality.

[0026] 2. After treatment by the method of this application, the acid leaching concentration of thallium in solid waste can be stably reduced to below 5 μg / L, and the leaching concentration of beryllium can be as low as below 1 μg / L. The leaching toxicity of the solidified body after treatment is significantly better than the national solid waste identification standard, which provides a solid foundation for the safe disposal or resource utilization of solid waste containing beryllium and thallium, such as lithium smelting slag.

[0027] 3. This application utilizes the calcium, sodium and other elements abundant in solid waste containing beryllium and thallium, such as lithium smelting slag, as mineralization inducers to directly convert beryllium and thallium into thermodynamically stable inert mineral phases. The resulting solidified body has high stability and low disposal cost, effectively avoiding the risk of secondary leaching.

[0028] 4. The method of this application does not require harsh conditions such as high temperature and high pressure, requires a small amount of reagent, and has a simple operation process. While achieving ultra-low leaching concentration, it significantly reduces investment and operating costs and has excellent prospects for industrial application. Attached Figure Description

[0029] Figure 1 A flowchart illustrating the method of using a reagent for immobilizing beryllium and thallium in solid waste, as provided in this application. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] For simplicity, this application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly stated; and any lower limit can be combined with other lower limits to form a range not explicitly stated, just as any upper limit can be combined with any other upper limit to form a range not explicitly stated. Furthermore, although not explicitly stated, every point or individual value between the endpoints of the range is included within that range. Therefore, each point or individual value can be used as its own lower or upper limit and combined with any other point or individual value or with other lower or upper limits to form a range not explicitly stated.

[0033] To address the aforementioned technical problems, this application provides a reagent for immobilizing beryllium and thallium in solid waste, comprising a soluble sulfide and a soluble phosphate, wherein the mass ratio of the soluble sulfide to the soluble phosphate is 1:0.5 to 1:2.

[0034] In addition, this application also provides a method for using a reagent to fix beryllium and thallium in solid waste, see reference. Figure 1 The flowchart shown includes the following steps: S1, mixing solid waste with a reagent to obtain a solid mixture; the average particle size of the solid waste is ≤400µm, and the solid waste includes beryllium and thallium; S2, adding water to the solid mixture to obtain a solid-liquid mixture for reaction; the solid-liquid ratio of the solid-liquid mixture is 1:0.5~1:2; S3, separating the solid-liquid mixture after reaction to obtain a solidified body; the solidified body is the product of beryllium and thallium being fixed. Specific Implementation Example 1 1) A solid mixture is obtained by mixing lithium smelting slag and reagents (sodium sulfide and sodium phosphate in a mass ratio of 1:0.5). The main chemical composition of the lithium smelting slag, by mass percentage, includes 50 wt.% CaSO4, 25 wt.% (Na,K)(Si3Al)O8, 20 wt.% (Ca,Na)(Si,Al)4O8, 2 wt.% Fe2O3, and 3 wt.% CaF2. The average particle size of the lithium smelting slag is ≤400 μm, and the contents of highly toxic elements beryllium and thallium are 200 μg / kg and 70 μg / kg, respectively. The reagents account for 0.5 wt.% of the total mass of the solid mixture.

[0036] 2) The obtained solid mixture was added to water at a solid-liquid ratio of 1:1 and allowed to stand for 30 minutes to react, thus obtaining a solid-liquid mixture; 3) Separate the solid-liquid mixture to obtain a solidified lithium smelting slag.

[0037] Example 2 The preparation method is similar to that in Example 1, except that: 1) Reagent (sodium sulfide to sodium phosphate in a mass ratio of 1:1).

[0038] Example 3 The preparation method is similar to that in Example 1, except that: 1) Reagent (sodium sulfide to sodium phosphate in a mass ratio of 1:1.5).

[0039] Example 4 The preparation method is similar to that in Example 3, except that: 1) The mass percentage of the reagent is 0.2 wt.% based on the mass of the solid mixture being 100%.

[0040] Example 5 The preparation method is similar to that in Example 1, except that: 1) Reagent (sodium sulfide to sodium phosphate in a mass ratio of 1:2).

[0041] Comparative Example 1 The preparation method is similar to that in Example 1, except that: 1) Mix lithium smelting slag and sodium sulfide as a single reagent to obtain a solid mixture.

[0042] Comparative Example 2 The preparation method is similar to that in Example 1, except that: 1) Mix lithium smelting slag and sodium phosphate as a single reagent to obtain a solid mixture.

[0043] The lithium smelting slag solids obtained in Examples 1-6 and Comparative Examples 1-2 were crushed, ground, and passed through a sieve with a 9.5 mm aperture. Heavy metal leaching toxicity tests and long-term leaching tests (5 days) were conducted using the solid waste leaching toxicity leaching method - sulfuric acid and nitric acid method (HJ / T 299~2007). The summary results of beryllium and thallium leaching concentrations are shown in Table 1.

[0044] Table 1

[0045] As shown in Table 1, Examples 1-5 using the reagents and methods of this invention can simultaneously solidify trace amounts of highly toxic elements beryllium and thallium in solid waste, obtaining lithium smelting slag solidified bodies that meet leaching toxicity standards. Furthermore, based on the long-term leaching concentration test results of thallium and beryllium, the obtained solidified bodies exhibit high stability, low disposal costs, and effectively avoid the risk of secondary leaching, meeting the future needs of the lithium smelting industry for solidifying hazardous elements.

[0046] As shown in Table 1, the thallium leaching concentration in Example 1 (mass ratio 1:0.5) was 4.541 μg / L and the beryllium concentration was 0.007 μg / L, while the thallium leaching concentration in Example 3 (mass ratio 1:1.5) was further reduced to 0.002 μg / L and the beryllium concentration was 0.010 μg / L. This indicates that adjusting the mass ratio within the preferred range can further enhance the fixation efficiency of thallium and beryllium. In Comparative Example 1, the beryllium leaching concentration using sodium sulfide alone reached 112.352 μg / L, far exceeding the national standard, while the thallium concentration was 3.121 μg / L. This indicates that while a single sulfide can partially fix thallium, it cannot effectively solidify beryllium because beryllium requires phosphate to form stable phosphate minerals. In Comparative Example 2 (sodium phosphate alone), the thallium leaching concentration was 7.393 μg / L (exceeding the standard), and the beryllium concentration was 1.751 μg / L. This shows that a single phosphate can solidify beryllium but is insufficient to fix thallium because thallium relies on sulfides to form thallium sulfide precipitates. Therefore, a single reagent (soluble sulfide or soluble phosphate) is insufficient for fixing the highly toxic elements beryllium and thallium. However, when two reagents are used in combination in a certain proportion, the effect is better than that of a single reagent, and both beryllium and thallium can be fixed simultaneously.

[0047] As shown in Table 1, the thallium leaching concentration in Example 4 (0.2 wt.% of reagent) was 2.312 μg / L and the beryllium concentration was 0.095 μg / L. In Example 3 (0.5 wt.% of reagent), the thallium leaching concentration was further reduced to 0.002 μg / L and the beryllium concentration was 0.010 μg / L. This indicates that adjusting the reagent mass ratio within the preferred range can further enhance the fixation efficiency of thallium and beryllium.

[0048] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A reagent for immobilizing beryllium and thallium in solid waste, characterized in that, It is composed of soluble sulfides and soluble phosphates, wherein the mass ratio of soluble sulfides to soluble phosphates is 1:0.5 to 1:

2.

2. The pharmaceutical preparation according to claim 1, characterized in that, The soluble sulfide includes at least one of sodium sulfide, potassium sulfide, and ammonium sulfide.

3. The pharmaceutical preparation according to claim 1, characterized in that, The soluble phosphate includes at least one of sodium phosphate, potassium phosphate, and ammonium phosphate.

4. The method of using the reagent for immobilizing beryllium and thallium in solid waste according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Mix the solid waste with the reagent to obtain a solid mixture; wherein the average particle size of the solid waste is ≤400μm, and the solid waste includes beryllium and thallium. S2. Water is added to the solid mixture to obtain a solid-liquid mixture, which is then reacted; the solid-liquid ratio of the solid-liquid mixture is 1:0.5~1:2; S3. The solid-liquid mixture after the reaction is subjected to solid-liquid separation to obtain a solidified body; the solidified body is the product of beryllium and thallium being fixed.

5. The method of use according to claim 4, characterized in that, Based on the mass of the solid mixture being 100%, the mass percentage of the agent is 0.2~1.0 wt.%.

6. The method of use according to claim 4, characterized in that, The solid waste is lithium smelting slag, including lepidolite smelting slag and / or spodumene smelting slag; the beryllium element is present in a silicate-bound state, and the thallium element is present in a sulfate-bound state.

7. The method of use according to claim 6, characterized in that, The beryllium content of the lithium smelting slag is 50~1000μg / kg, and the thallium content is 10~500μg / kg.

8. The method of use according to claim 6, characterized in that, The lithium smelting slag, based on 100% by mass, contains: 20-60 wt.% CaSO4, 5-30 wt.% (Na,K)(Si3Al)O8, 10-20 wt.% (Ca,Na)(Si,Al)4O8, 1-5 wt.% Fe2O3, and 1-5 wt.% CaF2.

9. The method of use according to claim 4, characterized in that, The reaction time is 20-40 minutes.

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