Method for reducing the content of tungsten in silicon-phosphorus-magnesium slag

Abstract

This invention discloses a method for reducing the tungsten content in magnesium phosphate slag, belonging to the field of rare metal hydrometallurgy and solid waste resource utilization. The method includes the following steps: crushing and ball milling the magnesium phosphate slag to obtain pretreated magnesium phosphate slag; mixing the pretreated magnesium phosphate slag with a weakly acidic complexing leachate, and performing a leaching reaction and solid-liquid separation to obtain low-tungsten magnesium phosphate slag and a tungsten-containing leachate. This invention, by ball milling the magnesium phosphate slag and mixing it with a weakly acidic complexing leachate for leaching, can efficiently and deeply remove tungsten impurities while maximizing the retention of the main components of the magnesium phosphate slag, thereby achieving tungsten enrichment and recovery, and resource utilization of the magnesium phosphate slag. The method of this invention operates under mild conditions, requiring no high-temperature roasting or strong acid leaching, and has low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of rare metal hydrometallurgy and solid waste resource utilization technology, and in particular to a method for reducing the tungsten content in silicon-phosphorus-magnesium slag. Background Technology

[0002] Silicon-phosphorus-magnesium slag is a typical solid waste generated during tungsten smelting, phosphorus chemical production, or magnesium salt production. It often contains a certain amount of tungsten (usually 0.2%-1.5%). If it is directly stockpiled or sold, it will not only cause the loss of tungsten resources, but also bring environmental hazards due to the risk of tungsten leaching. At the same time, the high tungsten content also limits the resource utilization of silicon-phosphorus-magnesium slag in building materials, metallurgical additives and other fields.

[0003] Existing processing technologies mostly employ high-temperature roasting or strong acid leaching, which suffer from problems such as high energy consumption, significant loss of silicon, phosphorus, and magnesium, and difficulty in tungsten recovery.

[0004] Therefore, developing a mild, efficient, and selective method for removing tungsten from silicon-phosphorus-magnesium slag is of great significance for reducing the volume of solid waste from silicon-phosphorus-magnesium slag, recycling it as a resource, and efficiently recovering tungsten resources. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a method to reduce the tungsten content in silicon-phosphorus-magnesium slag, thereby solving the technical problems of high energy consumption, large loss of silicon-phosphorus-magnesium slag, and high difficulty in tungsten recovery in the existing silicon-phosphorus-magnesium slag treatment technology.

[0006] This invention provides a method for reducing the tungsten content in magnesium phosphate slag, comprising the following steps: The silicon-phosphorus-magnesium slag is crushed and ball-milled to obtain pretreated silicon-phosphorus-magnesium slag. The pretreated silicon-phosphorus-magnesium slag was mixed with a weakly acidic complex leachate, and after leaching reaction and solid-liquid separation, low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate were obtained.

[0007] Furthermore, during the ball milling process, the particle size is reduced to below 200 mesh. If the particle size of the magnesium phosphate slag is too high, the reaction interface cannot be fully exposed, which is not conducive to the leaching of tungsten.

[0008] Furthermore, the silicon-phosphorus-magnesium slag is at least one of silicon-phosphorus-magnesium smelting slag or silicon-phosphorus-magnesium tailings slag.

[0009] Furthermore, by mass percentage, the composition of silicon-phosphorus-magnesium slag includes: W 0.3%-1.2%, SiO2 35%-42%, P2O5 8%-15%, and MgO 22%-31%.

[0010] Furthermore, the weakly acidic complexing leachate is at least one of a citric acid-oxalic acid mixed solution or a hydrogen peroxide-sulfuric acid mixed solution.

[0011] Furthermore, in the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15%-20% and the concentration of oxalic acid is 10%-15%.

[0012] Furthermore, in the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 10%-20%, and the concentration of sulfuric acid is 20%-30%.

[0013] Furthermore, the liquid-to-solid ratio of the weakly acidic complex leachate to the pretreated silica-phosphorus-magnesium slag is (6-10):1.

[0014] Furthermore, during the leaching reaction, the temperature is 50℃-80℃, the time is 2-4 hours, and the stirring speed is 150-300 r / min.

[0015] Furthermore, the above method for reducing the tungsten content in magnesium phosphate slag also includes the following steps: Low-tungsten silicon-phosphorus-magnesium slag is washed with water and dried to obtain low-tungsten silicon-phosphorus-magnesium products. Tungsten-containing leachate is enriched and recovered by adjusting pH and adding precipitants or chelating resins for adsorption. The leachate after enriching and recovering tungsten is recycled for the leaching reaction process.

[0016] Furthermore, adjust the pH to 8-12.

[0017] Furthermore, the precipitant includes, but is not limited to, soluble calcium sources and / or soluble magnesium sources.

[0018] Compared with the prior art, the beneficial effects of the present invention include: This invention involves ball-milling Mg-phosphorus slag and then mixing it with a weakly acidic complex leaching solution for leaching. This process efficiently and deeply removes tungsten impurities while preserving the main components of the Mg-phosphorus slag to the maximum extent, thereby achieving tungsten enrichment and recovery, as well as the resource utilization of the Mg-phosphorus slag. The method of this invention operates under mild conditions, requiring no high-temperature roasting or strong acid leaching, and has low energy consumption. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0020] This invention provides a method for reducing the tungsten content in magnesium phosphate slag, comprising the following steps: S1. The silicon-phosphorus-magnesium slag is crushed and ball-milled to obtain pretreated silicon-phosphorus-magnesium slag. S2. The pretreated silicon-phosphorus-magnesium slag and the weakly acidic complex leachate are mixed, and after leaching reaction and solid-liquid separation, low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate are obtained.

[0021] In this invention, the silicon-phosphorus-magnesium slag is crushed and ball-milled to ensure full exposure of the reaction interface. The pretreated silicon-phosphorus-magnesium slag is then mixed with a weakly acidic complexing leachate, and a leaching reaction is performed to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are largely retained in the slag. This process effectively removes tungsten impurities while maximizing the retention of the main components of the silicon-phosphorus-magnesium slag, simultaneously achieving tungsten enrichment and recovery. The method of this invention operates under mild conditions, requiring no high-temperature roasting or strong acid leaching, and has low energy consumption.

[0022] In this invention, the ball milling process involves grinding the material to a particle size below 200 mesh. If the particle size of the magnesium phosphate slag is too high, the reaction interface cannot be fully exposed, which is detrimental to the leaching of tungsten.

[0023] In this invention, the silicon-phosphorus-magnesium slag is at least one of silicon-phosphorus-magnesium smelting slag or silicon-phosphorus-magnesium tailings slag.

[0024] In some specific embodiments of the present invention, the composition of the silicon-phosphorus-magnesium slag by mass percentage includes: W 0.3%-1.2%, SiO2 35%-42%, P2O5 8%-15%, and MgO 22%-31%.

[0025] In this invention, the weakly acidic complexing leachate is at least one of a citric acid-oxalic acid mixed solution or a hydrogen peroxide-sulfuric acid mixed solution.

[0026] Preferably, in the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15%-20%, including but not limited to 15%, 16%, 17%, 18%, 19%, 20%, etc., and the concentration of oxalic acid is 10%-15%, including but not limited to 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0027] Preferably, in the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 10%-20%, including but not limited to 10%, 12%, 15%, 18%, 20%, etc., and the concentration of sulfuric acid is 20%-30%, including but not limited to 20%, 22%, 25%, 28%, 30%, etc.

[0028] In this invention, the liquid-to-solid ratio of the weakly acidic complex leachate to the pretreated silica-phosphorus-magnesium slag is (6-10):1, including but not limited to 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0029] In this invention, during the leaching reaction, the temperature is 50℃-80℃, including but not limited to 50℃, 60℃, 70℃, 80℃, etc., the time is 2-4 hours, including but not limited to 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc., and the stirring speed is 150-300 r / min, including but not limited to 150 r / min, 200 r / min, 250 r / min, 300 r / min, etc.

[0030] In this invention, the method for reducing the tungsten content in magnesium phosphate slag further includes the following steps: S3. Low-tungsten silicon-phosphorus-magnesium slag is washed with water and dried to obtain low-tungsten silicon-phosphorus-magnesium product. Tungsten-containing leachate is enriched and recovered by adjusting pH and adding precipitant or chelating resin for adsorption. The leachate after enriching and recovering tungsten is recycled for the leaching reaction process.

[0031] In this invention, the above-mentioned low-tungsten silicon-phosphorus-magnesium slag is washed with water and dried to obtain low-tungsten silicon-phosphorus-magnesium products, so as to realize resource utilization; the above-mentioned tungsten-containing leachate is enriched and recovered by adjusting the pH and adding precipitants or chelating resins for adsorption; the leachate after enriching and recovering tungsten can be recycled for the leaching reaction process.

[0032] Preferably, the pH is adjusted to 8-12, including but not limited to 8, 9, 10, 11, 12, etc.

[0033] Preferably, the precipitant includes, but is not limited to, soluble calcium sources and / or soluble magnesium sources.

[0034] Example 1 This embodiment provides a method for reducing the tungsten content in magnesium phosphate slag, including the following steps: (1) Raw material pretreatment: crush and ball mill the silicon-phosphorus-magnesium smelting slag (containing W 0.8%, SiO2 35%, P2O5 12%, MgO 28%) to below 200 mesh to ensure that the reaction interface is fully exposed.

[0035] (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 6:1. Under the condition of stirring speed of 200 r / min, control the leaching reaction temperature at 60℃ and the leaching reaction time at 2.5 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15% and the concentration of oxalic acid is 10%.

[0036] (3) Post-processing: After the reaction is completed, the residue is filtered to obtain low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate. The low-tungsten silicon-phosphorus-magnesium slag is washed three times with deionized water and dried to obtain a low-tungsten silicon-phosphorus-magnesium product that can be recycled. The pH of the tungsten-containing leachate is adjusted to 10 with sodium hydroxide solution, and tungsten is precipitated with saturated calcium chloride solution to achieve tungsten enrichment and recovery. The leachate after tungsten enrichment and recovery can be recycled. During the tungsten precipitation process, the Ca:W ratio is controlled at 1.3:1, the temperature is 70℃, and the time is 4h.

[0037] Example 2 This embodiment provides a method for reducing the tungsten content in magnesium phosphate slag, including the following steps: (1) Raw material pretreatment: crush and ball mill the silicon-phosphorus-magnesium tailings slag (containing 1.2% W, 40% SiO2, 58% P2O, and 22% MgO) to below 200 mesh to ensure that the reaction interface is fully exposed.

[0038] (2) Selective leaching: Prepare a hydrogen peroxide-sulfuric acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the hydrogen peroxide-sulfuric acid mixed solution with the silicon-phosphorus-magnesium tailings slag at a liquid-solid ratio of 8:1. Under the condition of stirring speed of 250 r / min, control the leaching reaction temperature at 70℃ and the leaching reaction time at 3 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 15% and the concentration of sulfuric acid is 25%.

[0039] (3) Post-processing: After the reaction is completed, the residue is filtered to obtain low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate. The low-tungsten silicon-phosphorus-magnesium slag is washed three times with deionized water and dried to obtain a low-tungsten silicon-phosphorus-magnesium product that can be recycled. The pH of the tungsten-containing leachate is adjusted to 10 with sodium hydroxide solution, and tungsten is precipitated with saturated calcium chloride solution to achieve tungsten enrichment and recovery. The leachate after tungsten enrichment and recovery can be recycled. During the tungsten precipitation process, the Ca:W ratio is controlled at 1.3:1, the temperature is 70℃, and the time is 4h.

[0040] Example 3 This embodiment provides a method for reducing the tungsten content in magnesium phosphate slag, including the following steps: (1) Raw material pretreatment: crush and ball mill the silicon-phosphorus-magnesium smelting slag (containing W 0.3%, SiO2 42%, P2O5 15%, MgO 31%) to below 200 mesh to ensure that the reaction interface is fully exposed.

[0041] (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 10:1. Under the condition of stirring speed of 150 r / min, control the leaching reaction temperature at 50℃ and the leaching reaction time at 4 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 20% and the concentration of oxalic acid is 15%.

[0042] (3) Post-processing: After the reaction is completed, the residue is filtered to obtain low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate. The low-tungsten silicon-phosphorus-magnesium slag is washed three times with deionized water and dried to obtain a low-tungsten silicon-phosphorus-magnesium product that can be recycled. The pH of the tungsten-containing leachate is adjusted to 10 with sodium hydroxide solution, and tungsten is precipitated with saturated calcium chloride solution to achieve tungsten enrichment and recovery. The leachate after tungsten enrichment and recovery can be recycled. During the tungsten precipitation process, the Ca:W ratio is controlled at 1.3:1, the temperature is 70℃, and the time is 4h.

[0043] Comparative Example 1 Compared with Example 1, the only difference is that the leaching reaction temperature is 40°C, and step (2) is as follows: (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 6:1. Under the condition of stirring speed of 200 r / min, control the leaching reaction temperature at 40℃ and the leaching reaction time at 2.5 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15% and the concentration of oxalic acid is 10%.

[0044] Comparative Example 2 Compared with Example 1, the only difference is that the leaching reaction temperature is 90°C, and step (2) is as follows: (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 6:1. Under the condition of stirring speed of 200 r / min, control the leaching reaction temperature at 90℃ and the leaching reaction time at 2.5 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15% and the concentration of oxalic acid is 10%.

[0045] Comparative Example 3 Compared with Example 1, the only difference is that the concentration of citric acid is 10% and the concentration of oxalic acid is 5%, and step (2) is as follows: (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 6:1. Under the condition of stirring speed of 200 r / min, control the leaching reaction temperature at 60℃ and the leaching reaction time at 2.5 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 10% and the concentration of oxalic acid is 5%.

[0046] Comparative Example 4 Compared with Example 1, the only difference is that the concentration of citric acid is 25% and the concentration of oxalic acid is 20%. Step (2) is as follows: (2) Selective leaching: Prepare a citric acid-oxalic acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the citric acid-oxalic acid mixed solution with the silicon-phosphorus-magnesium smelting slag at a liquid-to-solid ratio of 6:1. Under the condition of stirring speed of 200 r / min, control the leaching reaction temperature at 60℃ and the leaching reaction time at 2.5 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 25% and the concentration of oxalic acid is 20%.

[0047] Comparative Example 5 Compared with Example 2, the only difference is that the concentration of hydrogen peroxide is 5% and the concentration of sulfuric acid is 15%. Step (2) is as follows: (2) Selective leaching: Prepare a hydrogen peroxide-sulfuric acid mixed solution and use it as a weakly acidic complex leaching solution. Mix the hydrogen peroxide-sulfuric acid mixed solution with the silicon-phosphorus-magnesium tailings slag at a liquid-solid ratio of 8:1. Under the condition of stirring speed of 250 r / min, control the leaching reaction temperature at 70℃ and the leaching reaction time at 3 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 5% and the concentration of sulfuric acid is 15%.

[0048] Comparative Example 6 Compared with Example 2, the only difference is that the concentration of hydrogen peroxide is 25% and the concentration of sulfuric acid is 35%. Step (2) is as follows: (2) Selective leaching: Prepare a hydrogen peroxide-sulfuric acid mixed solution and use it as a weakly acidic complexing leaching solution. Mix the hydrogen peroxide-sulfuric acid mixed solution with the silicon-phosphorus-magnesium tailings slag at a liquid-solid ratio of 8:1. Under the condition of stirring speed of 250 r / min, control the leaching reaction temperature at 70℃ and the leaching reaction time at 3 hours to selectively dissolve tungsten, while the silicon-phosphorus-magnesium components are basically retained in the slag. In the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 25% and the concentration of sulfuric acid is 35%.

[0049] Performance testing The low-tungsten silicon-phosphorus-magnesium products obtained in the above embodiments and comparative examples were tested, and the test results are shown in Table 1.

[0050] Table 1

[0051] Please refer to Table 1. As can be seen from Table 1, by using the methods in Examples 1-3 of the present invention, the tungsten content in the low-tungsten silicon-phosphorus-magnesium product is reduced to below 0.02%, the tungsten removal rate is ≥95%, and the silicon-phosphorus-magnesium retention rate is ≥98%. This shows that the method of the present invention can achieve good removal effect on tungsten while avoiding a large loss of useful components.

[0052] Compared with Example 1, in Comparative Example 1, the leaching reaction temperature was too low, the reaction rate was slowed down, resulting in poor tungsten dissolution and more tungsten remaining in the silicon-phosphorus-magnesium slag.

[0053] Compared with Example 1, in Comparative Example 2, the leaching reaction temperature was too high, the reaction rate increased, and although the leaching effect of tungsten was improved, the retention rate of silicon, phosphorus and magnesium decreased significantly. In addition, the high temperature also caused an increase in energy consumption.

[0054] Compared with Example 1, in Comparative Example 3, the concentrations of citric acid and oxalic acid were too low, resulting in decreased acidity of the system and reduced complexing ability for tungsten, leading to poor tungsten dissolution and more tungsten remaining in the silicophosphorus magnesium slag.

[0055] Compared with Example 1, in Comparative Example 4, the concentrations of citric acid and oxalic acid were too high, and the acidity of the system was significantly increased. Although the leaching effect of tungsten was improved, it would lead to a significant decrease in the retention rate of silicon, phosphorus and magnesium. In addition, the high concentrations of citric acid and oxalic acid would also increase the cost of raw materials.

[0056] Compared with Example 2, in Comparative Example 5, the concentrations of hydrogen peroxide and sulfuric acid were too low, resulting in decreased acidity of the system and reduced complexing ability for tungsten, leading to poor tungsten dissolution and more tungsten remaining in the silicophosphorus magnesium slag.

[0057] Compared with Example 2, in Comparative Example 6, the concentrations of hydrogen peroxide and sulfuric acid were too high, and the acidity of the system was significantly increased. Although the leaching effect of tungsten was improved, it would lead to a significant decrease in the retention rate of silicon, phosphorus and magnesium. In addition, the high concentrations of hydrogen peroxide and sulfuric acid would also increase the cost of raw materials.

[0058] In summary, the beneficial effects of the present invention include: (1) High selectivity: Tungsten removal rate ≥95%, while the main body retention rate of silicon-phosphorus-magnesium slag ≥98%, avoiding a large loss of useful components.

[0059] (2) Mild conditions: No high-temperature roasting is required. A weakly acidic system is used, resulting in less equipment corrosion, lower energy consumption, and safer operation.

[0060] (3) Resource recycling: Tungsten can be efficiently enriched and recycled, realizing the resource utilization of valuable metals in solid waste without secondary pollution.

[0061] (4) Slag resource utilization: After treatment, the tungsten content in the silicon-phosphorus-magnesium slag is reduced to below 0.02%, which can be safely used in building materials, metallurgical additives and other fields to realize solid waste disposal.

[0062] (5) Good economic efficiency: the leaching reagent can be recycled, the reagent consumption is low, the process is short, and it is suitable for large-scale industrial processing.

[0063] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for reducing the tungsten content in magnesium phosphate slag, characterized in that, Includes the following steps: The silicon-phosphorus-magnesium slag is crushed and ball-milled to obtain pretreated silicon-phosphorus-magnesium slag. The pretreated silicon-phosphorus-magnesium slag and the weakly acidic complex leachate are mixed, and after leaching reaction and solid-liquid separation, low-tungsten silicon-phosphorus-magnesium slag and tungsten-containing leachate are obtained.

2. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, During the ball milling process, the balls are milled to a mesh size of 200 or less.

3. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, The silicon-phosphorus-magnesium slag is at least one of silicon-phosphorus-magnesium smelting slag or silicon-phosphorus-magnesium tailings slag.

4. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, The composition of the silicon-phosphorus-magnesium slag by mass percentage includes: W 0.3%-1.2%, SiO2 35%-42%, P2O5 8%-15%, and MgO 22%-31%.

5. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, The weakly acidic complexing leachate is at least one of a citric acid-oxalic acid mixed solution or a hydrogen peroxide-sulfuric acid mixed solution.

6. The method for reducing the tungsten content in magnesium phosphate slag according to claim 5, characterized in that, In the citric acid-oxalic acid mixed solution, the concentration of citric acid is 15%-20%, and the concentration of oxalic acid is 10%-15%. In the hydrogen peroxide-sulfuric acid mixed solution, the concentration of hydrogen peroxide is 10%-20% and the concentration of sulfuric acid is 20%-30%.

7. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, The liquid-to-solid ratio of the weakly acidic complex leachate to the pretreated silica-phosphorus-magnesium slag is (6-10):

1.

8. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, During the leaching reaction, the temperature is 50℃-80℃, the time is 2-4 hours, and the stirring speed is 150-300 r / min.

9. The method for reducing the tungsten content in magnesium phosphate slag according to claim 1, characterized in that, It also includes the following steps: The low-tungsten silicon-phosphorus-magnesium slag is washed with water and dried to obtain the low-tungsten silicon-phosphorus-magnesium product. The tungsten-containing leachate is enriched and recovered by adjusting the pH and adding a precipitant or chelating resin for adsorption. The leachate after enriching and recovering tungsten is recycled for the leaching reaction process.

10. The method for reducing the tungsten content in magnesium phosphate slag according to claim 9, characterized in that, Adjust the pH to 8-12; and / or, The precipitant is a soluble calcium source and / or a soluble magnesium source.

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