Special phosphorus and arsenic selective precipitation impurity removal method for sodium molybdate solution
By adjusting the pH in the sodium molybdate solution and generating Mg(OH)2 colloid to adsorb impurities, the problem of removing phosphorus and arsenic impurities in the sodium molybdate solution was solved, realizing an efficient and simple impurity removal process, ensuring the purity of molybdenum products and low loss.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies for removing phosphorus and arsenic impurities from sodium molybdate solutions easily introduce additional anionic impurities and have low reaction efficiency, failing to meet the requirements for high-purity molybdenum products.
The pH of the sodium molybdate solution was adjusted to 2-3 by adding a strong acid to precipitate the molybdate solid. The precipitate was then reacted with magnesium oxide and phosphoric acid to generate a purified solution. PO43- and AsO43- were adsorbed by Mg(OH)2 colloid, and a precipitation reaction was carried out at pH 8-10. The purified sodium molybdate solution was obtained by filtration.
It achieves the goals of not introducing additional impurities, shortening the impurity removal time, maintaining the purity of molybdenum products, reducing molybdenum loss, and is suitable for industrial production.
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Figure CN121778784A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of impurity removal technology, and in particular to a method specifically for the selective precipitation of phosphorus and arsenic in sodium molybdate solution to remove impurities. Background Technology
[0002] I. Phosphorus and arsenic are inherent impurities in sodium molybdate solution and cannot be avoided naturally:
[0003] From the perspective of raw materials, the raw materials for preparing sodium molybdate (such as molybdenum ore with associated phosphorus and arsenic) themselves contain large amounts of phosphorus and arsenic. During the smelting and leaching processes, these phosphorus and arsenic compounds will be released in ionic form (such as PO4). 3- AsO4 3- If it enters the sodium molybdate solution, it becomes an "inherent" impurity; if it is not actively removed, it will enter the final product during subsequent processing of the solution (such as crystallization and purification), forming "impurity residue".
[0004] II. Arsenic directly damages the core performance of sodium molybdate, leading to product failure:
[0005] Different applications have different performance requirements for sodium molybdate, but phosphorus and arsenic impurities can specifically disrupt its key functions.
[0006] In the chemical industry (catalysts / supports): Sodium molybdate is often used as a catalyst or support for oxidation and hydrogenation reactions, while phosphorus and arsenic can bind to the active sites of molybdenum, occupying the catalytic center—for example, phosphorus can bind to MoO4. 2- Stable phosphomolybdic heteropolyacids are formed, causing molybdenum to lose its catalytic activity; arsenic, on the other hand, will reduce the selectivity of the catalyst by "poisoning" the active sites, causing the conversion rate of the target reaction to drop from more than 90% to less than 60%, and may even trigger side reactions to generate impurity products.
[0007] In the metallurgical field (molybdenum alloy raw materials): if sodium molybdate containing phosphorus and arsenic is used to prepare molybdenum metal or molybdenum alloys, phosphorus will form a brittle molybdenum phosphide (MoP) phase in the alloy, resulting in a 30-50% decrease in the fracture toughness of the material; arsenic will cause "grain boundary embrittlement", making the alloy prone to cracking during processing, which cannot meet the strength requirements of aerospace and high-end equipment for molybdenum alloys.
[0008] I. Precipitation Method: The traditional mainstream technique, simple to operate but with significant limitations, especially when using salt reagents, which introduces a large amount of additional impurities, such as Cl- from MgCl2. - Using MgSO4 will introduce SO42-. 2- Ions. A new impurity removal step requiring the introduction of new ions needs to be performed subsequently. If metal oxides are used directly, such as MgO, the reaction will be slow, making rapid and extensive impurity removal impossible.
[0009] Precipitation is the earliest industrial technology for removing phosphorus and arsenic. Its core principle is the reaction of metal ions with PO4. 3- AsO4 3- Separation is achieved by forming sparingly soluble salts:
[0010] 1. Magnesium salt precipitation method (MgSO4, MgCl2, etc.)
[0011] Principle: Mg 2+ With PO4 3- Mg3(PO4)2 is formed, along with AsO4. 3- The formation of Mg3(AsO4)2 depends on an alkaline environment to promote precipitation.
[0012] Core weakness:
[0013] Additional anionic impurities are introduced: When using salt reagents, a large amount of additional impurities are introduced, such as Cl- from MgCl2. - Using MgSO4 will introduce SO42-. 2- Ions. A new purification step for the newly introduced ions needs to be performed subsequently.
[0014] The reaction is slow and inefficient: If metal oxides are used directly, such as MgO, the reaction will be slow and it will be impossible to remove a large amount of impurities quickly.
[0015] 2. Calcium salt precipitation method (CaCl2, Ca(OH)2, etc.)
[0016] Principle: Ca 2+ It forms Ca3(PO4)2 and Ca3(AsO4)2 with phosphorus and arsenic, and utilizes the low-cost advantage of calcium salts to remove impurities;
[0017] Core weakness:
[0018] Extremely poor selectivity: Ca 2+ It readily forms CaMoO4 precipitate with molybdate (Ksp = 4.1 × 10⁻⁶). -8 Especially under strongly alkaline conditions with pH > 12 (for calcium salts to remove phosphorus and arsenic, which require high pH), the molybdenum loss rate can reach 8-15%, severely reducing the utilization rate of molybdenum resources; the acid and alkali consumption is large: Ca(OH)2 needs to be added first to adjust the pH to above 12, and then acid needs to be added back to neutral after the reaction, increasing the acid and alkali consumption cost by 15-20 yuan per ton of solution, and generating a large amount of saline wastewater;
[0019] 3. Iron / aluminum salt precipitation method (FeCl3, Al2(SO4)3, etc.)
[0020] Principle: Fe 3+ / Al 3+Simultaneously, metal phosphates / arsenates (such as FePO4, AlAsO4) and hydroxides (such as Fe(OH)3) are generated, and impurities are removed through precipitation and adsorption in a coordinated manner;
[0021] Core weakness:
[0022] Introducing a new impurity ion: Fe 3+ / Al 3+ If an excessive amount is added, residual ions will enter the sodium molybdate solution, causing the Fe / Al content in the subsequent crystallized product to exceed the standard, requiring an additional step to remove them;
[0023] Molybdenum adsorption loss: Fe(OH)3 and Al(OH)3 are high specific surface area adsorbents that can adsorb 1-3% of molybdate ions in the solution, and the adsorbed molybdenum is difficult to desorb and recover.
[0024] pH regulation is complex: Fe 3+ The optimal reaction pH is 4-6, Al 3+ The pH is 5-7, while sodium molybdate solution is usually alkaline (pH 8-10). It is necessary to add acid to adjust the pH first, and then add alkali to neutralize after the reaction. The operation is cumbersome and the reagent consumption is high. Summary of the Invention
[0025] In view of this, this application provides a method specifically for the selective precipitation and removal of impurities from sodium molybdate solution by phosphorus and arsenic, which can effectively overcome the defects of the prior art.
[0026] This application provides a method specifically for the selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, comprising the following steps:
[0027] S1. Add strong acid to a pure sodium molybdate solution to perform acid precipitation. Use strong acid to adjust the pH of the solution to 2-3, so that molybdenum precipitates out as solid molybdate. Then filter to separate and obtain solid molybdate.
[0028] S2. Dissolve the molybdate solid and magnesium oxide in water, and add a small amount of phosphoric acid to ensure that the P concentration in the solution is 50~2000 mg / L. Start stirring the reaction to obtain a purified solution.
[0029] S3. Add the impurity removal solution to the sodium molybdate solution with high P and As content, stir evenly, then add sodium hydroxide to adjust the pH to 8-10, and carry out the precipitation reaction. After the reaction, filter to obtain filter residue and pure sodium molybdate solution. The pure sodium molybdate solution enters the downstream section for further processing, and a portion of the pure sodium molybdate solution is taken out to make a new impurity removal solution.
[0030] Preferably, in step S2, the mass ratio of the molybdate solid, magnesium oxide, and water is 2:1:5 to 8:1:10.
[0031] Preferably, in step S2, the impurity removal agent solution comprises the following components: Mo 50~120g / l, Mg 20~60g / l, P 50~100mg / l.
[0032] Preferably, in step S3, the stirring time is 20 to 60 minutes.
[0033] Preferably, in step S3, the pH adjustment time is 30-60 minutes.
[0034] Preferably, in step S3, the precipitation reaction takes 30 to 120 minutes.
[0035] Preferably, in step S1, the strong acid is nitric acid, sulfuric acid, or hydrochloric acid.
[0036] Preferably, in step S1, the temperature of the acid precipitation is 20~70℃.
[0037] Compared with the prior art, this application has the following advantages:
[0038] 1. No additional anionic impurities are introduced, thus not affecting the quality and purity of subsequent molybdenum products.
[0039] 2. The impurity removal time is short, it can be done at room temperature and pressure, the operation is simple, and the process is easy to industrialize.
[0040] 3. Molybdenum loss is less than 1%. Attached Figure Description
[0041] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0042] Figure 1 This is a schematic flowchart of the method for selective precipitation of phosphorus and arsenic in sodium molybdate solution for impurity removal according to this application. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0044] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.
[0045] In the following examples, unless otherwise specified, all raw materials can be obtained by commercial purchase or conventional methods.
[0046] It should be noted that the principle of making the impurity removal agent is that molybdenum acid and water, with phosphorus preferentially combining to form an acidic phosphomolybdic heteropolyacid (phosphomolybdic heteropolyacid ion) solution, while releasing hydrogen ions from the solid molybdenum acid. Then, solid MgO is slowly added, and the process must be slow while ensuring that the pH is <6 to ensure that the Mg salt is completely dissolved.
[0047] like Figure 1 As shown, the method for selective precipitation of phosphorus and arsenic in sodium molybdate solution for impurity removal in this embodiment includes the following steps:
[0048] 1. Acid precipitation and filtration
[0049] Hydrochloric acid is added to a pure sodium molybdate solution (from a downstream process) to perform acid precipitation. The acidity of the solution is adjusted to pH 2-3, causing molybdenum to precipitate as solid molybdate. The precipitate is then separated by filtration to obtain solid molybdate. The purpose of this step is to initially enrich molybdenum and remove some soluble impurities.
[0050] 2. The stirring reaction of molybdic acid with magnesium oxide, water, and phosphoric acid.
[0051] The molybdate solid obtained in step 1 is mixed with magnesium oxide and water (mass ratio 2:1:5~8:1:10), and a small amount of phosphoric acid is added to ensure the P concentration in the solution is 50~100 mg / L. The reaction is then started with stirring. Under the promotion of the small amount of phosphoric acid, the molybdate solid reacts to form phosphomolybdic acid, which increases the solubility of the molybdate solid and releases sufficient hydrogen ions. These hydrogen ions quickly react with magnesium oxide, promoting the dissolution of Mg, resulting in a solution with Mo 50~120 g / L, Mg 20~60 g / L, and P 50~100 mg / L. This solution is the prepared impurity removal agent (impurity removal solution).
[0052] 3. Additive reaction and filtration
[0053] For sodium molybdate solutions with high P and As content, the molybdenum-specific impurity removal solution prepared in step 2 is added to the solution according to the P and As impurity content in the solution. The amount of addition is based on the molar ratio of Mg:(P+As) being 1.5 to 2.5 times.
[0054] After adding the special impurity remover, stir for 20-60 minutes until evenly mixed. Then, add sodium hydroxide to adjust the pH over 30-60 minutes, gradually adjusting the pH from acidic to 8-10. During this process, Mg generates a large amount of Mg(OH)2 colloid. This colloid has a large specific surface area and a positive charge, thus adsorbing a large amount of PO4. 3- With AsO4 3- This process removes the impurities. After reacting for 30-120 minutes, the mixture is filtered to obtain filter residue and a pure sodium molybdate solution. The pure sodium molybdate solution is then sent to the next stage for further processing. Simultaneously, a portion of the pure sodium molybdate solution is returned to the first stage to prepare a new molybdenum-specific impurity removal agent.
[0055] The entire impurity removal process ensures that the pure sodium molybdate solution does not introduce Cl. - With SO4 2- The presence of anions is the greatest advantage of this application (after purification, no Cl- is introduced into the solution). - With SO4 2- Therefore, it is a trace amount, and the test results are similar.
[0056] Specifically, the method for selective precipitation of phosphorus and arsenic in sodium molybdate solution for impurity removal in this embodiment includes the following steps:
[0057] 1. 1 ml of pure sodium molybdate solution 3 The molybdenum mass fraction is 10%, and hydrochloric acid is added continuously. The initial amount added is based on the equation (2H). + +Na₂MoO₄=H₂MoO₄+2Na + Calculate the amount of 30% hydrochloric acid to be added as 250 kg. After that, continue adding hydrochloric acid at a rate of 10 kg per minute until the pH reaches 2-3.
[0058] 2. Take 150 kg of molybdate solid from the obtained molybdate solid and add 1.5 mg of [amount missing]. 3 Add water, then add 1.5 kg of phosphoric acid (85%), heat to 60°C, react for 1 hour, and after the solution pH is below 2, add approximately 35 kg of MgO. Stir for 2 hours until the solution is clear, and use this as the purified solution for later use.
[0059] 3. Take 1 ml of sodium molybdate solution with high P and As content. 3 Its components are Mo 60g / l, P 1g / l, and As 1g / l.
[0060] Add 0.15m to the high-impact solution 3 The impurity-removed solution obtained in step 2 was treated with approximately 3 kg of sodium hydroxide to adjust the pH to 8-10. After reacting for 60 minutes, the solution was filtered to obtain the filter residue and a pure sodium molybdate solution.
[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A method specifically for the selective precipitation and removal of impurities from sodium molybdate solution by phosphorus and arsenic, characterized in that, Includes the following steps: S1. Add strong acid to a pure sodium molybdate solution to perform acid precipitation. Use strong acid to adjust the pH of the solution to 2-3, so that molybdenum precipitates out as solid molybdate. Then filter to separate and obtain solid molybdate. S2. Dissolve the molybdate solid and magnesium oxide in water, and add a small amount of phosphoric acid to ensure that the P concentration in the solution is 50~2000 mg / L. Start stirring the reaction to obtain a purified solution. S3. Add the impurity removal solution to the sodium molybdate solution with high P and As content, stir evenly, then add sodium hydroxide to adjust the pH to 8-10, and carry out the precipitation reaction. After the reaction, filter to obtain filter residue and pure sodium molybdate solution. The pure sodium molybdate solution enters the downstream section for further processing, and a portion of the pure sodium molybdate solution is taken out to make a new impurity removal solution.
2. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S2, the mass ratio of the molybdate solid, magnesium oxide, and water is 2:1:5 to 8:1:
10.
3. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S2, the impurity removal agent solution comprises the following components: Mo 50~120g / l, Mg 20~60g / l, P 50~100mg / l.
4. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S3, the stirring time is 20 to 60 minutes.
5. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S3, the pH adjustment time is 30-60 minutes.
6. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S3, the precipitation reaction takes 30 to 120 minutes.
7. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S1, the strong acid is nitric acid, sulfuric acid, or hydrochloric acid.
8. The method for selective precipitation and removal of impurities from sodium molybdate solution using phosphorus and arsenic, as described in claim 1, is characterized in that... In step S1, the temperature of the acid precipitation is 20~70℃.