Method for removing vanadium impurities through coupling of sodium chromate feed liquid

Abstract

The invention discloses a method for removing vanadium impurities by coupling sodium chromate feed liquid. The method comprises the following steps: preparing polyferric sulfate vanadium removal liquid; and adjusting the pH value of the sodium chromate feed liquid, then adding the vanadium-removed polyferric sulfate liquid into the sodium chromate feed liquid, and washing with a filter to obtain a sodium chromate neutral liquid. The method has the following beneficial effects that vanadium impurities are removed through coupling when sodium metaaluminate and polymeric ferric sulfate are neutralized, generated ferric hydroxide enters a chromium slag system, and new impurities are not introduced for vanadium removal and quality improvement; the method is simple to operate, free of newly added chromium-containing waste and beneficial to industrial green production. Besides, before the vanadium removal solution is prepared, the polyferric sulfate is modified, potassium sodium tartrate for improving the complexing effect is introduced, styrene for preventing ferric iron from precipitating is introduced, so that the stability of the polyferric sulfate after complexing with aluminum in the sodium chromate solution is improved, and the complex further forms a net-shaped structure by introducing silicic acid sol; the reaction area is increased, and vanadium in the sodium chromate solution can be further removed.

Description

Technical Field

[0001] The invention belongs to the technical field of comprehensive utilization of chromium salts, and in particular relates to a method for removing vanadium impurities by coupling sodium chromate liquid. Background Art

[0002] Chromium salt is one of the main types of inorganic salts. Calcium-free roasting is the main process for the production of sodium vanadium red, a basic product of chromium salt. The development of calcium-free roasting technology, especially the application of oxygen-enriched roasting technology, has increased the conversion rate of chromium materials, reduced the consumption of soda ash and chromium ore, and improved the utilization rate of resources. However, as the calcination quality improves, side reactions are reduced, and the sodium aluminate content of the alkaline slurry for material leaching is reduced. The original aluminum-vanadium simultaneous removal technology cannot meet the quality requirements. The industry's conventional calcium-based vanadium removal process produces carcinogen calcium chromate, which poses an environmental risk.

[0003] For example, CN101318701A discloses a method for removing vanadium impurities from chromium salts by lime in the production of sodium chromate neutral liquid. In this method, lime and sodium chromate generate carcinogenic calcium chromate, and the calcium slag has high loss, which is difficult to dispose of secondary and has certain environmental risks. In addition, lime devanadiumization has high pH requirements, and the front-end pretreatment needs to be stable. For example, CN108502928A discloses a production method for deep devanadiumization in the calcium-free roasting process of chromite. In this method, pseudo-boehmite can achieve the vanadium removal effect, but in the sodium chromate liquid system, the formation of pseudo-boehmite requires the temperature to be lowered by 50-60°C. At this temperature, the sodium chromate has high loss and is not easy to wash. A large amount of clean water needs to be added to the system, increasing the evaporation cost. The subsequent pseudo-boehmite devanadiumization liquid also needs to remove chromium, and the hexavalent chromium must be reconverted into trivalent chromium to form a calcium-free system. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages according to the present invention, a method for removing vanadium impurities by coupling sodium chromate liquid is provided, characterized in that it comprises the following steps:

[0006] Step 1, preparing polyferric sulfate vanadium removal liquid;

[0007] Step 2: adjust the pH of the sodium chromate solution, then add the polyferric sulfate vanadium removal solution into the sodium chromate solution, filter and wash, and obtain a sodium chromate neutral solution.

[0008] Preferably, in step 1, the concentration of the polyferric sulfate vanadium removal solution is 4 to 6 g / L.

[0009] Preferably, in the step 2, dilute sulfuric acid is added to adjust the pH to 6.8-7.2, and the polyferric sulfate vanadium removal solution is added to react for 1-2 hours at a reaction temperature of 80-95° C., and the mixture is filtered and washed for 3-4 hours.

[0010] Preferably, in the step 2, the aluminum content in the sodium chromate solution is 15000-20000 mg / L in terms of Al2O3; the vanadium content in the sodium chromate solution is 500-1000 mg / L, and the amount of the polyferric sulfate vanadium removal solution added is n 铝铁偶合物 / n 钒 =35~45:1; n 铝铁偶合物 is the amount of γ-AlOOH and Fe(OH)3, n 钒 It is the amount of sodium vanadate in sodium chromate slurry.

[0011] Preferably, the method for removing vanadium impurities by coupling sodium chromate liquid according to claim 1 is characterized in that, in the step 1, modified polyferric sulfate can be prepared first, and then the vanadium removal liquid is prepared, and the method for preparing the modified polyferric sulfate is:

[0012] S1, dissolving ferrous sulfate heptahydrate in water, and then adding concentrated sulfuric acid thereto to obtain an acidified ferrous sulfate solution;

[0013] S2, adding potassium sodium tartrate and styrene to the acidified ferrous sulfate solution, stirring evenly to obtain a mixed solution;

[0014] S3, adding an oxidant to the mixed solution and heating the mixture for a period of time to obtain a polyferric sulfate solution;

[0015] S4. Adding the sodium silicate solution into sulfuric acid to generate a stable silicate sol, then adding the silicate sol into the polyferric sulfate solution, evaporating the solvent after the aging reaction, and obtaining the modified polyferric sulfate.

[0016] Preferably, in S1, the mass ratio of ferrous sulfate heptahydrate to water is 1:0.8-1, and the molar ratio of sulfate ions to ferrous ions in the solution after concentrated sulfuric acid is added is 1.5-1:1.

[0017] Preferably, in S2, the molar ratio of potassium sodium tartrate, styrene and ferrous ions in the ferrous sulfate solution prepared in S1 is 0.05-0.1:0.01-0.03:1.

[0018] Preferably, in S3, the oxidant is potassium permanganate, the molar ratio of potassium permanganate to the ferrous ions in the mixed solution prepared from S2 is 0.2-0.3:1, the reaction temperature is 30-80°C, and the reaction time is 1-4h.

[0019] Preferably, in S4, the content of SiO2 in the silicate sol is controlled to be 0.5-1wt%, and the pH value of the silicate sol is 1-5. When adding the silicate sol, the molar ratio of silicon ions in the silicate sol to iron ions in the polyferric sulfate solution is 0.01-0.05:1, and the aging reaction is carried out for 10-20 minutes.

[0020] The present invention includes at least the following beneficial effects: the present invention provides a method for coupling the removal of vanadium impurities by sodium chromate liquid, wherein the vanadium impurities are removed by coupling when sodium aluminate is neutralized with polyferric sulfate, and the generated ferric hydroxide enters the chromium slag system, and no new impurities are introduced for vanadium removal and quality improvement. In addition, the present invention is simple to operate, does not generate any new chromium-containing waste, and is beneficial to green industrial production. The present invention can also modify the polyferric sulfate before preparing the vanadium removal liquid, introduce phosphate, potassium sodium tartrate, and aluminum chloride that increase the complexing effect, so as to increase the stability of the polyferric sulfate after complexing with aluminum in the sodium chromate solution, and further form a network structure of the complex by introducing silicate sol, thereby increasing the reaction area, which is beneficial to further remove vanadium from the sodium chromate solution.

[0021] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in further detail below so that those skilled in the art can implement it according to the description.

[0023] Example 1

[0024] A method for removing vanadium impurities by coupling sodium chromate liquid, comprising the following steps:

[0025] Step 1, preparing a polyferric sulfate vanadium removal solution with a concentration of 4 g / L;

[0026] Step 2: 20m 3 Dilute sulfuric acid was added to the sodium chromate solution containing 15.02 g / L aluminum (in terms of Al2O3) and 547.68 mg / L vanadium to adjust the pH to 7. Then, 2 ml of chromate was added to the sodium chromate solution at 85°C. 3 The polyferric sulfate vanadium removal solution was reacted for 2 hours and then filtered and washed for 3 hours to obtain a sodium chromate solution with a vanadium content of 41.66 mg / L, which met the process requirements (process indicator V≤50 mg / L).

[0027] Example 2

[0028] A method for removing vanadium impurities by coupling sodium chromate liquid, comprising the following steps:

[0029] Step 1, preparing a polyferric sulfate vanadium removal solution with a concentration of 4 g / L;

[0030] Step 2: 20m 3 Dilute sulfuric acid was added to the sodium chromate solution containing 16.18 g / L aluminum (in terms of Al2O3) and 571.26 mg / L vanadium to adjust the pH to 7. Then, 2 ml of chromate was added to the sodium chromate solution at 85°C. 3 The polyferric sulfate vanadium removal solution was reacted for 2 hours and then filtered and washed for 3 hours to obtain a sodium chromate solution with a vanadium content of 38.22 mg / L, which met the process requirements (process indicator V≤50 mg / L).

[0031] Example 3

[0032] A method for removing vanadium impurities by coupling sodium chromate liquid, comprising the following steps:

[0033] Step 1, preparing a polyferric sulfate vanadium removal solution with a concentration of 6 g / L;

[0034] Step 2: 20m 3 Dilute sulfuric acid was added to the sodium chromate solution containing 19.88 g / L aluminum (in terms of Al2O3) and 724.33 mg / L vanadium to adjust the pH to 7. Then, 2 ml of chromate was added to the sodium chromate solution at 85°C. 3 The polyferric sulfate vanadium removal solution was reacted for 2 hours and then filtered and washed for 3 hours to obtain a sodium chromate solution with a vanadium content of 48.60 mg / L, which met the process requirements (process indicator V≤50 mg / L).

[0035] Example 4

[0036] A method for removing vanadium impurities by coupling sodium chromate liquid, comprising the following steps:

[0037] Step 1: First prepare modified polyferric sulfate, and then prepare vanadium removal liquid. The specific method is as follows:

[0038] S1, dissolving 278g of ferrous sulfate heptahydrate in 250g of water, and then slowly adding 20g of concentrated sulfuric acid thereto to obtain an acidified ferrous sulfate solution;

[0039] S2, add 10.6g of potassium sodium tartrate and 2g of styrene to the acidified ferrous sulfate solution, and stir to obtain a mixed solution;

[0040] S3, adding 32g potassium permanganate to the mixed solution, reacting at 40°C for 2.5h to obtain a polyferric sulfate solution;

[0041] S4, adding sulfuric acid to the sodium silicate solution to prepare a silicate sol with a SiO2 concentration of 1wt%, then adding 96g of the silicate sol to the polyferric sulfate solution, aging for 20min and then evaporating the solvent to obtain modified polyferric sulfate. Then prepare a modified polyferric sulfate vanadium removal liquid with a concentration of 4g / L;

[0042] Step 2 is consistent with Example 1, and finally a sodium chromate solution with a vanadium content of 11.21 mg / L is obtained (the process index is V≤50 mg / L).

[0043] Comparative Example 1

[0044] The method disclosed in CN101318701A for removing vanadium impurities in a neutral solution of sodium chromate produced by removing chromium salts with lime is adopted, and vanadium is removed from a sodium chromate solution having an aluminum content of 15.02 g / L (in terms of Al2O3) and a vanadium content of 547.68 mg / L. The vanadium content of the sodium chromate solution finally obtained is 105 mg / L. The vanadium content in the solution after vanadium removal by this method is higher than that in Example 1 of the present invention. In this method, lime and sodium chromate generate carcinogenic calcium chromate, and the calcium slag has high loss, which is difficult to be disposed of secondary, and there is a certain environmental risk. In addition, lime devanadiumization has a high pH requirement, and the front-end pretreatment needs to be stable.

[0045] Comparative Example 2

[0046] The difference between this comparative example and Example 4 is that S2 is to add 10.6g of water and 2g of styrene to the acidified ferrous sulfate solution, and stir evenly to obtain a mixed solution; the remaining steps are consistent with Example 4, and finally a sodium chromate solution with a vanadium content of 39.52mg / L is obtained (the process index is V≤50mg / L).

[0047] Comparative Example 3

[0048] The difference between this comparative example and Example 4 is that in S4, no silicate sol is added to the polyferric sulfate solution, but the polyferric sulfate solution is directly evaporated and dried, and the remaining steps are consistent with Example 4, and finally a sodium chromate solution with a vanadium content of 25.69 mg / L is obtained (the process indicator is V≤50 mg / L).

[0049] Comparative Example 4

[0050] The difference between this comparative example and Example 4 is that S2 is to add 10.6g of potassium sodium tartrate and 2g of water to the acidified ferrous sulfate solution, and stir evenly to obtain a mixed solution; the remaining steps are consistent with Example 4, and finally a sodium chromate solution with a vanadium content of 25.87mg / L is obtained (the process index is V≤50mg / L).

[0051] It can be seen from the results of Examples 1 to 4 and Comparative Examples 1 to 3 that the method for removing vanadium from sodium chromate solution of the present invention can not only effectively reduce the vanadium content in the solution, but also can avoid generating harmful wastes and introducing new impurities. At the same time, the present invention can also prepare modified polyferric sulfate to further enhance its vanadium removal capability. It can be seen from the results of Comparative Example 2 that the complexing ability of the modified polyferric sulfate for vanadium in the sodium chromate solution is reduced due to the lack of introduction of potassium sodium tartrate, thereby reducing the vanadium removal effect. It can be seen from the results of Comparative Example 3 that the reaction area is reduced due to the lack of introduction of silicate sol to form a network structure when preparing the modified polyferric sulfate, thereby reducing the vanadium removal effect. It can be seen from the results of Comparative Example 4 that styrene is not introduced when preparing the modified polyferric sulfate, thereby causing part of the trivalent iron in the polyferric sulfate solution to precipitate, thereby reducing the coupling amount with aluminum in the sodium chromate solution, thereby reducing the vanadium removal effect.

[0052] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for removing vanadium impurities by coupling sodium chromate liquid, characterized in that: The following steps are involved: Step 1, preparing polyferric sulfate vanadium removal liquid; Step 2: adjust the pH of the sodium chromate solution, then add the polyferric sulfate vanadium removal solution into the sodium chromate solution, filter and wash, and obtain a sodium chromate neutral solution.

2. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 1, characterized in that: In the step 1, the concentration of the polyferric sulfate vanadium removal solution is 4 to 6 g / L.

3. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 1, characterized in that: In the step 2, dilute sulfuric acid is added to adjust the pH to 6.8-7.2, and the polyferric sulfate vanadium removal solution is added to react for 1-2 hours at a reaction temperature of 80-95° C., and the filter is washed for 3-4 hours.

4. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 1, characterized in that: In the step 2, the aluminum content in the sodium chromate solution is 15000-20000 mg / L in terms of Al2O3; the vanadium content in the sodium chromate solution is 500-1000 mg / L, and the amount of the polyferric sulfate vanadium removal solution added is n 铝铁偶合物 / n 钒 =35~45:1; n 铝铁偶合物 is the amount of γ-AlOOH and Fe(OH)3, n 钒 It is the amount of sodium vanadate in sodium chromate slurry.

5. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 1, characterized in that: In the step 1, modified polyferric sulfate may be prepared first, and then the vanadium removal liquid may be prepared. The method for preparing the modified polyferric sulfate is: S1, dissolving ferrous sulfate heptahydrate in water, and then adding concentrated sulfuric acid thereto to obtain an acidified ferrous sulfate solution; S2, adding potassium sodium tartrate and styrene to the acidified ferrous sulfate solution, stirring evenly to obtain a mixed solution; S3, adding an oxidant to the mixed solution and heating the mixture for a period of time to obtain a polyferric sulfate solution; S4. Adding the sodium silicate solution into sulfuric acid to generate a stable silicate sol, then adding the silicate sol into the polyferric sulfate solution, evaporating the solvent after the aging reaction, and obtaining the modified polyferric sulfate.

6. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 5, characterized in that: In S1, the mass ratio of ferrous sulfate heptahydrate to water is 1:0.8-1, and concentrated sulfuric acid is added to the solution so that the molar ratio of sulfate ions to ferrous ions is 1.5-1:

1.

7. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 5, characterized in that: In S2, the molar ratio of potassium sodium tartrate, styrene and ferrous ions in the ferrous sulfate solution prepared in S1 is 0.05-0.1:0.01-0.03:

1.

8. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 5, characterized in that: In the S3, the oxidant is potassium permanganate, the molar ratio of potassium permanganate to the ferrous ions in the mixed solution prepared from S2 is 0.2-0.3:1, the reaction temperature is 30-80°C, and the reaction is carried out for 1-4 hours.

9. The method for removing vanadium impurities by coupling sodium chromate liquid according to claim 5, characterized in that: In S4, the content of SiO2 in the silicate sol is controlled to be 0.5-1wt%, and the pH value of the silicate sol is 1-5. When adding the silicate sol, the molar ratio of silicon ions in the silicate sol to iron ions in the polyferric sulfate solution is 0.01-0.05:1, and the aging reaction is carried out for 10-20 minutes.