Method for deep dephosphorization of a crude sodium tungstate solution

Abstract

The application belongs to the technical field of tungsten hydrometallurgy, and particularly relates to a method for deep phosphorus removal from a crude sodium tungstate solution, which comprises the following steps: placing activated carbon in a dilute nitric acid solution for activation; adding the activated activated carbon into the crude sodium tungstate solution containing a flotation agent and phosphorus elements, performing first stirring, then adding calcium salt, performing second stirring and heating, and finally performing solid-liquid separation to obtain the phosphorus-removed sodium tungstate solution. The oxygen-containing functional groups on the surface of the activated carbon after activation can induce interface mineralization of calcium hydroxyl phosphate, overcome the phosphorus removal bottleneck that cannot be broken through by the traditional calcium salt precipitation method, remove the flotation agent by pre-adsorption of the activated carbon, avoid the wrapping of organic colloids on the precipitated particles, make the settling speed of the phosphorus removal residue fast and the filtration performance good, greatly improve the production operation conditions, significantly reduce the consumption of the subsequent phosphorus removal agent, further reduce the purification cost of tungsten smelting, and be easy to implement and popularize in the existing tungsten smelting production line.

Description

Technical Field

[0001] This application belongs to the field of tungsten hydrometallurgical technology, specifically a method for deep dephosphorization of crude sodium tungstate solution. Background Technology

[0002] In the beneficiation process of scheelite, flotation is commonly used, employing oleic acid and oxidized paraffin soap as collectors. These organic flotation agents inevitably enter the crude sodium tungstate solution obtained from subsequent alkaline decomposition. A particularly prominent problem is that, with the continuation of the production cycle and the increase in the number of alkaline decompositions of the scheelite, the flotation agents adhering to the mineral surface continuously accumulate in the alkaline cooking system and eventually transfer into the solution. These organic substances gradually adhere to and accumulate on the inner walls of the feed tanks and pipes in subsequent processes, forming a continuous source of contamination. This leads to an increasingly higher flotation agent content in the crude sodium tungstate solution of subsequent treatments, making it increasingly difficult to effectively treat using traditional methods.

[0003] The crude sodium tungstate solution contains various impurities such as phosphorus, arsenic, silicon, and molybdenum. Among these, phosphorus impurities severely affect the quality of subsequent ammonium paratungstate (APT) products. When faced with oleic acid, whose concentration increases with each cycle, traditional phosphorus removal methods, such as the magnesium salt method (which generates magnesium ammonium phosphate precipitate), experience a sharp decline in phosphorus removal efficiency. This is because: 1) Organic flotation agents such as oleic acid can encapsulate phosphorus impurities or react with phosphorus removal agents to form stable colloids or complexes, hindering phosphorus precipitation; 2) Large amounts of organic matter can encapsulate newly formed precipitate particles, making it difficult for them to grow and settle, resulting in difficult liquid-solid separation, slow settling of the phosphorus removal slag, and poor filterability; 3) Oleic acid itself may also react with calcium ions to form insoluble substances, increasing reagent consumption and introducing new impurities.

[0004] Patent CN110683582A discloses a method for removing phosphorus from sodium tungstate solution. This method involves adding calcium tungstate to the sodium tungstate solution and controlling the solution pH, temperature, and reaction time to reduce the phosphorus content of phosphate (PO4) in the solution. 3-The tungsten phosphate precipitate is formed by reacting with calcium tungstate as a precipitant. This precipitate is then separated into a low-phosphorus tungsten-containing filtrate and a tungsten-containing dephosphorized filter residue. The low-phosphorus tungsten-containing filtrate can be directly used to prepare the pre-exchange solution for the next ion exchange process in tungsten smelting, while the tungsten-containing dephosphorized filter residue is returned to the previous ore decomposition process to recover the tungsten. This method suffers from incomplete phosphorus removal and a high tungsten content in the dephosphorized residue. Furthermore, returning the tungsten-containing dephosphorized residue to the ore decomposition process requires significant energy and additional alkali to decompose the calcium tungstate in the residue, thus increasing production costs. Patent CN110157898B discloses a method for dephosphorizing a tungstate-containing solution. This method involves adding hydrogen peroxide to the tungstate solution, adjusting the pH to 7-10, and finally adding a calcium-containing compound to the pH-adjusted solution, followed by filtration to obtain a peroxytungstate solution. While this method avoids tungsten loss, it is complex, costly, and the separated peroxytungstate solution needs to be converted into tungstic acid through acid addition and heating to obtain subsequent products.

[0005] Currently, most research on phosphorus removal from crude sodium tungstate solutions focuses on reducing tungsten loss and improving removal efficiency, with little attention paid to effective phosphorus removal in the presence of high-efficiency flotation agents. In crude sodium tungstate solutions with high oleic acid content, traditional phosphorus removal methods often require large amounts of phosphorus removal agents to barely achieve phosphorus removal due to severe interference from organic matter. This is not only costly but also results in unstable performance and difficult solid-liquid separation. Therefore, developing a method that can effectively address high oleic acid content and achieve deep, efficient, and low-cost phosphorus removal is of significant practical importance to the tungsten smelting industry. Summary of the Invention

[0006] To address the aforementioned problems, this application provides a method for deep phosphorus removal from crude sodium tungstate solution. Through the synergistic effect of activated carbon and calcium salts, integrated deep phosphorus removal is achieved, stably reducing the phosphorus concentration in the solution to below 0.02 g / L. This method not only overcomes the difficulties of low phosphorus removal efficiency and poor filtration performance under high oleic acid conditions, but also possesses comprehensive advantages such as simple process, low cost, thorough phosphorus removal, and ease of industrialization.

[0007] This application discloses a method for deep phosphorus removal from a crude sodium tungstate solution, comprising the following steps: S1. Obtain activated carbon and crude sodium tungstate solution, wherein the crude sodium tungstate solution contains flotation agent and phosphorus element; S2. The activated carbon is activated in a dilute nitric acid solution; S3. The activated carbon is added to the crude sodium tungstate solution and stirred for the first time. Then, calcium salt is added, and the mixture is stirred for the second time and heated. After solid-liquid separation, a sodium tungstate solution after phosphorus removal is obtained.

[0008] In the above technical solution, an integrated method of "enhanced adsorption-in-situ precipitation" is adopted. The core of this method lies in endowing activated carbon with a dual-functional interface through dilute nitric acid activation: after the wood powder activated carbon is activated by dilute nitric acid solution, the surface chemical properties are fundamentally changed. Dilute nitric acid treatment can introduce a large number of carboxyl (-COOH) and nitro (-NO2) functional groups on the surface of activated carbon. These functional groups not only exhibit specific chemical adsorption of flotation agents (especially oleic acid) molecules through hydrogen bonding and charge attraction, increasing the adsorption capacity by more than 30% compared to unactivated activated carbon, but more importantly, these functional groups provide a high-density nucleation active sites for subsequent in-situ anchoring of calcium ions. When calcium salts are added to the system containing activated activated carbon, the Ca2+ ions entering the solution... 2+ It preferentially adsorbs and accumulates around oxygen-containing functional groups on the surface of activated carbon, forming a localized supersaturated region. This process induces phosphate (PO4) ions. 3- Heterogeneous nucleation occurs directly on the surface of activated carbon, preferentially growing into insoluble hydroxyapatite along specific crystal planes. Compared to conventional homogeneous precipitation, this interface-induced mechanism further reduces the precipitation equilibrium concentration of phosphorus from approximately 0.05~0.1 g / L to below 0.02 g / L, achieving a deep purification limit unattainable by traditional calcium salt precipitation methods. Simultaneously, this mechanism allows the precipitate to tightly encapsulate the surface of activated carbon particles, forming dense, low-hydrophobic composite particles that can settle rapidly, fundamentally solving the persistent problems of sticky and difficult-to-filter precipitates in high-oleic acid systems.

[0009] In addition, in step S3 above, the activated carbon is added to the crude sodium tungstate solution and stirred for the first time, which can adsorb most of the organic flotation agents such as oleic acid; then calcium salt is added directly to the mixed system, stirred for the second time and heated, so that phosphorus is converted into calcium hydroxyphosphate precipitate; finally, the activated carbon loaded with organic matter and the calcium hydroxyphosphate precipitate can be removed simultaneously through only one solid-liquid separation to obtain the purified sodium tungstate solution.

[0010] Furthermore, the content of the flotation agent in the crude sodium tungstate solution is not less than 5 g / L, the content of phosphorus is 0.1~1 g / L, the COD value of the crude sodium tungstate solution is 2000~5000 ppm, the tungsten content (WO3) is 150~300 g / L, and the flotation agent is oleic acid.

[0011] Furthermore, in step S2, the mass fraction of the dilute nitric acid solution is 1%~5%, and the liquid-to-solid ratio of the dilute nitric acid solution to the activated carbon is (3~10) mL:1g. The concentration of dilute nitric acid mainly controls the introduction of functional groups on the surface of the activated carbon. When the concentration is below 1%, oxidation is insufficient and few functional groups are introduced; when the concentration is above 5%, excessive ablation of the carbon skeleton will lead to a decrease in specific surface area. The liquid-to-solid ratio of the dilute nitric acid solution to the activated carbon affects the uniformity of the reaction and the mass transfer efficiency. When the liquid-to-solid ratio is below 3 mL / g, the reaction will be uneven due to incomplete acid wetting; when the liquid-to-solid ratio is above 10 mL / g, the cost will increase. 3~10 mg / L can fully disperse and dissolve the activated carbon, achieving a stable activation and modification effect.

[0012] Furthermore, in step S2, the activation temperature is 30~80℃ and the activation time is 30~60min.

[0013] Furthermore, step S2 also includes washing the activated carbon with water and drying it.

[0014] Furthermore, in step S2, the specific surface area of ​​the activated carbon after activation is 800~1000 m². 2 / g, maximum particle size ≤75μm. Specific surface area is 800~1000m². 2 The / g particle size provides sufficient surface functional group attachment sites and pore volume, while avoiding the clogging problems caused by excessively small micropores and the fragility of the carbon skeleton due to excessively high specific surface area. A maximum particle size ≤75μm gives the activated carbon excellent suspension properties in dilute nitric acid, ensuring a uniform and rapid activation reaction.

[0015] Furthermore, in step S3, the solid-liquid ratio of the activated carbon to the crude sodium tungstate solution is (1~30) g:1 L.

[0016] Furthermore, in step S3, the calcium salt includes calcium carbonate, calcium oxide, or calcium hydroxide, and the amount of calcium salt added is 2 to 4 times the theoretical amount calculated based on the phosphorus concentration; the theoretical amount is confirmed by the following reaction equation: 5Ca 2+ +3PO4 3- +OH - →Ca5(PO4)3OH Furthermore, in step S3, the maximum particle size of the calcium salt is ≤45μm.

[0017] Furthermore, step S3 also includes adding the activated carbon to the crude sodium tungstate solution, performing a first stirring, and then adjusting the OH content in the crude sodium tungstate solution. -The concentration of the solution was 1.8~2.5 mol / L. Then, calcium salt was added, and the mixture was stirred and heated for the second time. After solid-liquid separation, a sodium tungstate solution after phosphorus removal was obtained.

[0018] Furthermore, the characteristic is that, in step S3, the first stirring speed is 100~300 rpm and the time is 10~60 min, the second stirring speed is 100~300 rpm and the time is 60~120 min, and the heating temperature is 60~100℃.

[0019] Furthermore, in step S3, the phosphorus content in the sodium tungstate solution after phosphorus removal does not exceed 0.02 g / L, and the flotation agent content does not exceed 0.03 g / L.

[0020] This application proposes a method for deep phosphorus removal from crude sodium tungstate solution, which produces the following beneficial effects: Pre-adsorption of flotation agents by activated carbon avoids the encapsulation of precipitate particles by organic colloids, resulting in faster settling speed and better filtration performance of the dephosphorized slag, greatly improving production operating conditions. Simultaneously, it significantly reduces the consumption of subsequent dephosphorizing agents, further lowering the purification cost of tungsten smelting. The activated carbon, after activation, not only possesses excellent organic matter adsorption capacity, but its reconstructed oxygen-containing functional groups can also induce interfacial mineralization of hydroxyapatite, overcoming the phosphorus removal bottleneck that cannot be overcome in traditional calcium salt precipitation methods due to the limitation of calcium phosphate dissolution equilibrium. This method is simple to operate, operates under mild conditions, requires no special equipment, and does not introduce new harmful anions such as chlorine and sulfur, avoiding secondary pollution. It is easy to implement and promote in existing tungsten smelting production lines. Detailed Implementation

[0021] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0022] This application discloses a method for deep phosphorus removal from a crude sodium tungstate solution, comprising the following steps: S1. Obtain activated carbon and crude sodium tungstate solution, the crude sodium tungstate solution containing flotation agent and phosphorus element; Preferably, the crude sodium tungstate solution contains a flotation agent content of not less than 5 g / L, a phosphorus content of 0.1~1 g / L, a COD value of 2000~5000 ppm, a tungsten content (WO3) of 150~300 g / L, and oleic acid as the flotation agent. Specifically, the phosphorus content can be any one or a range between any two of the following: 0.1 g / L, 0.3 g / L, 0.5 g / L, 0.7 g / L, 0.9 g / L, and 1 g / L; the COD value of the crude sodium tungstate solution can be any one or a range between any two of the following: 2000 ppm, 3000 ppm, 4000 ppm, and 5000 ppm; and the tungsten content (WO3) can be any one or a range between any two of the following: 150 g / L, 200 g / L, 250 g / L, and 300 g / L. In some preferred embodiments of this application, the crude sodium tungstate solution may be a crude sodium tungstate solution obtained by alkaline decomposition of scheelite or a crude sodium tungstate solution obtained by further alkaline dissolution of tungstic acid obtained by acid decomposition of scheelite.

[0023] S2. Activate the activated carbon in a dilute nitric acid solution; Preferably, the mass fraction of the dilute nitric acid solution is 1%~5%, the liquid-to-solid ratio of the dilute nitric acid solution to the activated carbon is (3~10) mL:1g; the activation temperature is 30~80℃, and the activation time is 30~60min; the specific surface area of ​​the activated carbon after activation is 800~1000m². 2 / g, maximum particle size ≤75μm. Specifically, the mass fraction of the dilute nitric acid solution can be any one or any two of 1%, 2%, 3%, 4%, 5%; the liquid-solid ratio of the dilute nitric acid solution to activated carbon can be any one or any two of 3mL:1g, 5mL:1g, 7mL:1g, 9mL:1g, 10mL:1g; the activation temperature can be any one or any two of 30℃, 40℃, 50℃, 60℃, 70℃, 80℃; the activation time can be any one or any two of 30min, 40min, 50min, 60min; the specific surface area of ​​the activated carbon after activation is 800m². 2 / g、850m 2 / g、900m 2 / g、850m 2 / g, 1000m 2 The range of / g or any one or both of these values. In some preferred embodiments of this application, the mixture may be stirred during activation; and the activated carbon may be washed with water and dried after activation.

[0024] S3. Add the activated carbon to the crude sodium tungstate solution and stir for the first time. Then add calcium salt, stir for the second time and heat. After solid-liquid separation, obtain the sodium tungstate solution after phosphorus removal. Preferably, the solid-liquid ratio of the activated carbon to the crude sodium tungstate solution is (1~30) g:1 L; the calcium salt includes calcium carbonate, calcium oxide or calcium hydroxide, and the amount of calcium salt added is 2~4 times the theoretical amount calculated based on the phosphorus concentration; the maximum particle size of the calcium salt is ≤45 μm; the first stirring speed is 100~300 rpm and the time is 10~60 min, the second stirring speed is 100~300 rpm and the time is 60~120 min, and the heating temperature is 60~100℃. Specifically, the solid-liquid ratio of the activated carbon to the crude sodium tungstate solution can be any one of 1g:1L, 5g:1L, 10g:1L, 15g:1L, 20g:1L, 25g:1L, 30g:1L, or any combination thereof; the amount of calcium salt added can be any one of 2, 2.5, 3, 3.5, or 4 times the theoretical amount calculated based on the phosphorus concentration, or any combination thereof; the first stirring speed can be any one of 100rpm, 150rpm, 200rpm, 250rpm, 300rpm, or any combination thereof, or any combination thereof. The time interval can be any one or a combination of 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min; the second stirring speed can be any one or a combination of 100 rpm, 150 rpm, 200 rpm, 250 rpm, and 300 rpm; the time can be any one or a combination of 60 min, 80 min, 100 min, and 120 min; and the heating temperature can be any one or a combination of 60°C, 70°C, 80°C, 90°C, and 100°C. In some preferred embodiments of this application, alkali is added before adding calcium salt to adjust the OH- ions in the crude sodium tungstate solution. - The concentration is 1.8~2.5 mol / L, and the alkali can be sodium hydroxide, OH... -The concentration can be any one of 1.8 mol / L, 2.0 mol / L, 2.2 mol / L, 2.4 mol / L, 2.5 mol / L, or any combination thereof. In some preferred embodiments of this application, the phosphorus content in the final dephosphorized sodium tungstate solution does not exceed 0.02 g / L, and the flotation agent content does not exceed 0.03 g / L. The phosphorus and flotation agent removal rates in this application are calculated as follows: Let the volume of the crude sodium tungstate solution be V1, the phosphorus content or flotation agent content be c1, the volume of the dephosphorized sodium tungstate solution be V2, and the phosphorus content or flotation agent content be c2. According to [1-(c2V2) / (c1V1)]×100%, the volume of the solution after phosphorus removal hardly changes, i.e., V1=V2. Therefore, the phosphorus removal rate of this application is not less than 95%, and the flotation agent removal rate is not less than 98%.

[0025] The technical solution of this application will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this application, the activated carbon after activation is obtained in the following manner: A certain amount of activated carbon was added to a 3% dilute nitric acid solution, with a liquid-to-solid ratio of 5 mL:1 g. The mixture was stirred at 50 °C for 45 min, washed with water, and dried to obtain activated carbon with a specific surface area of ​​900 m². 2 / g, maximum particle size ≤66μm.

[0026] Example 1 Take 1 L of crude sodium tungstate solution obtained after alkali decomposition of scheelite, with a WO3 concentration of 228.76 g / L, a phosphorus content of 0.4 g / L, a flotation agent content of 5 g / L, and a COD value of 2500 ppm; add 5 g of the above-mentioned activated carbon to the crude sodium tungstate solution and stir at 200 rpm for 30 min at room temperature; then add caustic soda flakes to the system to remove OH-. - The concentration was adjusted to 2.0 mol / L, and then 7 g of calcium carbonate powder (particle size <45 μm) was added. The mixture was heated to 80℃ and stirred at 200 rpm for 60 min. After the reaction was completed, the mixture was allowed to stand, and the precipitate settled rapidly, leaving a clear supernatant. The solution was filtered to obtain a phosphorus-removed sodium tungstate solution, in which the phosphorus content was 0.015 g / L, the phosphorus removal rate was 96.25%, the flotation agent content was reduced to 0.01 g / L, the flotation agent removal rate was 99.8%, the WO3 concentration was 228.23 g / L, and the WO3 loss rate was less than 0.3%.

[0027] Example 2 Take 1 L of crude sodium tungstate solution obtained by alkali dissolution of tungstic acid (obtained from the acid decomposition of scheelite), which has a WO3 concentration of 254.31 g / L, a phosphorus content of 0.6 g / L, a flotation agent content of 25 g / L, and a COD value of 4000 ppm. Add 15 g of the above-mentioned activated carbon to the crude sodium tungstate solution and stir at 200 rpm for 30 min at room temperature. Then add caustic soda flakes to the system to remove OH-. - The concentration was adjusted to 2.0 mol / L, and then 10 g of calcium carbonate powder (particle size <45 μm) was added. The mixture was heated to 80℃ and stirred at 200 rpm for 60 min. After the reaction was completed, the mixture was allowed to stand, and the precipitate settled rapidly, leaving a clear supernatant. The solution was filtered to obtain a phosphorus-removed sodium tungstate solution, in which the phosphorus content was 0.018 g / L, the phosphorus removal rate was 97%, the flotation agent content was reduced to 0.025 g / L, the flotation agent removal rate was 99.9%, the WO3 concentration was 253.29 g / L, and the WO3 loss rate was less than 0.5%.

[0028] Comparative Example 1 The only difference between this comparative example and Example 1 is that activated carbon is not added to the crude sodium tungstate solution; instead, the OH group is directly adjusted. - The concentration was adjusted to 2.0 mol / L, and then 7g of calcium carbonate powder was added for phosphorus removal.

[0029] The solution became turbid after the reaction, forming a large amount of colloidal precipitate that was difficult to settle, making filtration extremely difficult. The phosphorus content in the filtrate was still as high as 0.25 g / L, with a phosphorus removal rate of only 37.5%. The flotation agent content was 4.8 g / L, with a flotation agent removal rate of only 4%. The WO3 concentration was 227.63 g / L, with a WO3 loss rate of 0.5%.

[0030] Comparative Example 2 The only difference between this comparative example and Example 1 is that only activated carbon is added to the crude sodium tungstate solution, and calcium carbonate powder is not added for phosphorus removal.

[0031] The filtrate after filtration contained 0.3 g / L of phosphorus, with a phosphorus removal rate of only 25%. The flotation agent content was 0.015 g / L, with a flotation agent removal rate of 99.7%. The WO3 concentration was 228.43 g / L, with a WO3 loss rate of 0.1%. This comparative example shows that relying solely on activated carbon adsorption to remove some phosphorus bound to organic matter has a weak phosphorus removal effect.

[0032] Comparative Example 3 The only difference between this comparative example and Example 1 is that unactivated activated carbon was added to the crude sodium tungstate solution.

[0033] The filtrate after filtration contained 0.1 g / L of phosphorus (a removal rate of only 75%), 1.2 g / L of flotation agent (a removal rate of only 76%), and 227.89 g / L of WO3 (a loss rate of 0.4%). This comparative example demonstrates that using unactivated activated carbon significantly reduced the removal efficiency of both phosphorus and flotation agent compared to Example 1.

[0034] Comparative Example 4 The only difference between this comparative example and Example 1 is that activated carbon was added to the crude sodium tungstate solution, and the mixture was stirred at 200 rpm for 30 minutes at room temperature. Solid-liquid separation was then performed to obtain a solution free of oleic acid, and the OH content in the solution was adjusted. - The concentration was adjusted to 2.0 mol / L, and then 7g of calcium carbonate powder was added for phosphorus removal.

[0035] The filtrate after filtration contained 0.03 g / L of phosphorus, with a phosphorus removal rate of only 92.5%, 0.02 g / L of flotation agent, with a flotation agent removal rate of 99.6%, and 226.91 g / L of WO3, with a WO3 loss rate of 0.8%. This comparative example, which performed solid-liquid separation before adding calcium salts, was not only more cumbersome to operate than Example 1, but also resulted in a longer filtration time for the precipitate, a higher flotation agent content in the filtrate, and a lower phosphorus removal efficiency.

[0036] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for deep phosphorus removal from crude sodium tungstate solution, characterized in that, Includes the following steps: S1. Obtain activated carbon and crude sodium tungstate solution, wherein the crude sodium tungstate solution contains flotation agent and phosphorus element; S2. The activated carbon is activated in a dilute nitric acid solution; S3. The activated carbon is added to the crude sodium tungstate solution and stirred for the first time. Then, calcium salt is added, and the mixture is stirred for the second time and heated. After solid-liquid separation, a sodium tungstate solution after phosphorus removal is obtained. The content of the flotation agent in the crude sodium tungstate solution is not less than 5 g / L, and the flotation agent is oleic acid; In step S2, the mass fraction of the dilute nitric acid solution is 1%~5%, and the liquid-to-solid ratio of the dilute nitric acid solution to the activated carbon is (3~10) mL:1g.

2. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, The phosphorus content is 0.1~1g / L, the COD value of the crude sodium tungstate solution is 2000~5000ppm, and the tungsten content (WO3) is 150~300g / L.

3. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, In step S2, the activation temperature is 30~80℃ and the activation time is 30~60min.

4. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, In step S2, the specific surface area of ​​the activated carbon after activation is 800~1000 m². 2 / g, maximum particle size ≤75μm.

5. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, In step S3, the solid-liquid ratio of the activated carbon to the crude sodium tungstate solution is (1~30) g: 1 L.

6. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, In step S3, the calcium salt includes calcium carbonate, calcium oxide, or calcium hydroxide, and the amount of calcium salt added is 2 to 4 times the theoretical amount calculated based on the phosphorus concentration.

7. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, Step S3 further includes adding the activated carbon to the crude sodium tungstate solution, performing a first stirring, and then adjusting the OH content in the crude sodium tungstate solution. - The concentration of the solution was 1.8~2.5 mol / L. Then, calcium salt was added, and the mixture was stirred and heated for the second time. After solid-liquid separation, a sodium tungstate solution after phosphorus removal was obtained.

8. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 1, characterized in that, In step S3, the first stirring speed is 100~300 rpm and the time is 10~60 min, the second stirring speed is 100~300 rpm and the time is 60~120 min, and the heating temperature is 60~100℃.

9. The method for deep phosphorus removal from crude sodium tungstate solution according to claim 2, characterized in that, In step S3, the phosphorus content in the sodium tungstate solution after phosphorus removal does not exceed 0.02 g / L, and the flotation agent content does not exceed 0.03 g / L.