Separation method of vanadium and chromium ions in vanadium slag water leaching solution

Abstract

The invention discloses a method for separating vanadium and chromium ions in vanadium slag water leaching liquid, and belongs to the technical field of metallurgical chemical engineering, the method comprises the following steps: by taking the water leaching liquid obtained after sodium salt roasting of vanadium slag as raw material liquid, removing silicon, adjusting pH, adding a reducing agent to selectively reduce hexavalent chromium into trivalent chromium, and then adsorbing chromium in the solution by using cation exchange resin, thereby obtaining the vanadium and chromium ions in the vanadium slag water leaching liquid. Vanadium in the solution is subjected to vanadium precipitation to obtain vanadium pentoxide, then chromium on the resin is desorbed with an acid solution, the pH of the desorption solution is adjusted to form chromium precipitate, and chromium trioxide is obtained after roasting. According to the method, through collaborative innovation of selective reduction, strong acid cation exchange directional adsorption and an organic solvent-free process, the problems of incomplete separation of vanadium and chromium, low recovery rate and high cost in a traditional method are solved, efficient recovery of high-purity vanadium and chromium products is realized, and the method has both environmental protection property and economical efficiency.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical and chemical technology, and specifically relates to a method for separating vanadium and chromium ions from vanadium slag water leaching solution. Background Technology

[0002] Vanadium, as an important strategic metal, is widely used in energy, chemical, and construction industries, making its resource recovery and utilization crucial. Vanadium slag, a significant byproduct of the metallurgical industry, has a high concentration of vanadium ions in its leachate. Furthermore, the presence of large amounts of chromium ions in the solution severely impacts the difficulty of vanadium extraction and the purity of subsequent vanadium products, and the emission of hexavalent chromium ions causes pollution. Therefore, the separation and recovery of vanadium and chromium ions during vanadium extraction from vanadium slag leachate is essential.

[0003] Vanadium (V) and chromium (VI) are highly similar in chemical properties, making their separation difficult. Current techniques for removing chromium ions from vanadium-containing solutions mainly employ chemical precipitation, ion exchange, and solvent extraction.

[0004] Chinese patent document CN105950865A discloses a method for separating and extracting vanadium and chromium from high-chromium vanadium leaching solution. It utilizes the difference in redox properties of vanadium and chromium at different temperatures in solution to achieve separation of vanadium and chromium through stepwise precipitation. However, while chromium is precipitated, vanadium ions are adsorbed onto the precipitate, resulting in a decrease in vanadium recovery rate and further reducing the purity of the sample.

[0005] Chinese patent documents with publication numbers CN107312942A and CN108823408A both employ ionic liquid extractants to first extract vanadium and chromium into the organic phase, followed by back-extraction of the metal ion-loaded organic phase using an ammonium salt back-extractant. Vanadium is precipitated as ammonium polyvanadate or ammonium polyvanadate, and chromium in the back-extraction solution is reduced and precipitated by adjusting the pH. While these two methods solve the emulsification and partial water miscibility problems of traditional organic extractants, they have drawbacks. Ionic liquids typically have high viscosity, making mixing between the two phases difficult and significantly reducing the extraction rate. Furthermore, ionic liquids are expensive, making them difficult to meet the economic requirements of industrial applications.

[0006] Chinese patent document CN107190155A discloses a method for extracting vanadium and chromium from a vanadium-chromium mixed solution. This method uses anion exchange resin to adsorb vanadium and chromium from the solution, and then elutes the vanadium and chromium sequentially to achieve vanadium-chromium separation. However, this method requires two desorption steps, resulting in a low vanadium recovery rate and difficulty in effectively controlling purity. Summary of the Invention

[0007] The purpose of this invention is to provide a method for separating vanadium and chromium ions from vanadium slag leaching solution. This method solves the problems of incomplete vanadium and chromium separation, low recovery rate, and high cost in traditional methods through the synergistic innovation of selective reduction, strong acid cation exchange directional adsorption, and organic solvent-free process. It achieves efficient recovery of high-purity vanadium and chromium products, and is both environmentally friendly and economical.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for separating vanadium and chromium ions from vanadium slag aqueous leachate, the specific steps of which are as follows: (1) Adjust the pH of the vanadium slag water leaching solution to 9~12, add aluminum sulfate solution at 50~70℃, the molar ratio of silicon in the vanadium slag water leaching solution to aluminum in aluminum sulfate is 1:1.3~1.6, the reaction time is 30~60min, filter, add ammonia water to the filtrate to maintain pH 4.5~5.0, filter off the aluminum precipitate after 60~90min, and obtain the desiliconized solution A; (2) Adjust the pH of the desilication solution A to 2-3, add a reducing agent with a molar ratio of 1-1.2:1 to chromium in the desilication solution A, and selectively reduce for 10-60 minutes to achieve Cr2O7 2- Reduced to Cr 3+ Vanadium as H2V 10 O 28 4- The form remains unchanged in the solution, resulting in solution B; (3) Solution B is passed through a strong acid cation exchange resin at a flow rate of 2~4 BV / h to adsorb and remove chromium ions, thus obtaining a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 2.5~3.5, heat it to 60~80℃ and add ammonium chloride. After reacting for 1~2 hours, filter to obtain ammonium polyvanadate precipitate, and calcine to obtain V2O5; (5) Use an eluent to desorb the chromium in the strong acid cation exchange resin in step (3) to obtain a chromium-containing solution. Add sodium hydroxide to adjust the pH to 8-9 to obtain chromium precipitate, and calcine to obtain Cr2O3.

[0009] Furthermore, in step (1), the pH adjustment is performed using concentrated sulfuric acid or concentrated hydrochloric acid.

[0010] Furthermore, in step (2), the pH is adjusted using concentrated sulfuric acid or concentrated hydrochloric acid, and the reducing agent is sodium nitrite.

[0011] Furthermore, in step (3), the strong acid cation exchange resin is D001 or 001×7.

[0012] The reaction equation for the adsorption process is shown below: 3(R-SO3H)+Cr 3+→(R-SO3)3Cr+3H + Furthermore, in step (4), the pH is adjusted using sodium hydroxide or ammonia, and the amount of ammonium chloride added is 2 to 2.5 times the vanadium content in the vanadium-containing solution.

[0013] Furthermore, in step (4), the calcination temperature is 500~600℃ and the time is 2~4h.

[0014] Furthermore, in step (5), the eluent used is hydrochloric acid or sulfuric acid with a concentration of 4-10%.

[0015] Furthermore, in step (5), the calcination temperature is 450~550℃ and the time is 2~4h.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention solves the problems of incomplete vanadium-chromium separation, low recovery rate, and high cost in traditional methods by combining selective reduction, strong acid cation exchange directional adsorption, and organic solvent-free processes. It achieves efficient recovery of high-purity vanadium-chromium products, and is both environmentally friendly and economical.

[0017] 2. This invention uses sodium nitrite as a selective reducing agent to remove Cr2O7 from the solution. 2- Reduced to Cr 3+ Vanadium as H2V 10 O 28 4- The anionic form remains in solution, resulting in a fast reaction rate and no organic byproducts, thus avoiding the burden of subsequent processing.

[0018] 3. This invention employs directional adsorption with a strongly acidic cation exchange resin. After impurity removal, trivalent chromium can be adsorbed at a relatively low pH (2-3), while vanadium remains in the solution as anion, achieving efficient separation and improving V₂O₅ purity. The vanadium-containing solution, after vanadium precipitation and calcination, yields V₂O₅ with a purity exceeding 99% and a vanadium recovery rate exceeding 98.3%. The chromium-containing resin only requires one desorption step to recover chromium ions, achieving a chromium recovery rate exceeding 96.7% and a Cr₂O₃ purity exceeding 95.8%. Compared to traditional precipitation methods, this avoids the introduction of impurity ions, improves the purity of ammonium polyvanadate during subsequent vanadium precipitation, and also avoids vanadium ion loss due to entrainment during solid-liquid separation.

[0019] 4. This invention does not involve any organic solvents throughout the process, and achieves separation only through aqueous phase reaction and ion exchange, eliminating the problems of high viscosity, high cost, and safety hazards caused by organic solvents. It is a low-cost, safe, and efficient method. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the separation process of vanadium and chromium ions in the vanadium slag leaching solution in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments. It is worth noting that the scope of protection of the present invention is not limited to the examples described herein; any modifications or improvements made in accordance with the concept of the present invention are all within the scope of protection claimed by the present invention.

[0022] In the following examples and comparative examples, the recovery rates of vanadium and chromium, as well as the impurity content of the vanadium precipitate, were calculated by dissolving the solid in sulfuric acid solution and then measuring ICP.

[0023] The vanadium slag water leaching solution used in this invention consists of vanadium (5650 mg / L), chromium (1815 mg / L) and silicon (1437 mg / L). Example 1

[0024] (1) Take 300 mL of vanadium slag water leaching solution, adjust the pH to 9.0 with ammonia water, add 5.4 mL of 2 mol / L aluminum sulfate solution at 50℃, react for 30 min and then filter. Add ammonia water to the filtrate to maintain the pH value at 4.5, react for 60 min and then filter to obtain solution A; (2) Adjust the pH of solution A to 2.0 with concentrated sulfuric acid, add 1.087g of sodium nitrite and react for 10min to obtain solution B; (3) Control the flow rate of solution B to pass through the strong acid cation exchange resin D001 at a flow rate of 2BV / h to adsorb and remove chromium ions, and obtain a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 2.5 with ammonia water and heat it to 60°C. Add ammonium chloride at a molar ratio of ammonium / vanadium of 2. After reacting for 1 hour, filter to obtain ammonium polyvanadate precipitate. Calcine at 500°C for 2 hours to obtain V2O5. (5) The chromium-containing resin was desorbed with 4% sulfuric acid to obtain a chromium-containing desorbent solution. The pH of the chromium-containing desorbent solution was adjusted to 8.0 with sodium hydroxide to obtain chromium precipitate. Cr2O3 was obtained by calcination at 450℃ for 2 hours.

[0025] The total recovery rate and purity of vanadium were measured to be 98.6% and 99.1%, respectively, and the total recovery rate and purity of chromium were 96.7% and 96.3%, respectively. Example 2

[0026] (1) Take 300 mL of vanadium slag water leaching solution, adjust the pH to 10.0 with ammonia water, add 5.0 mL of 2 mol / L aluminum sulfate solution at 60℃, react for 40 min and then filter. Add ammonia water to the filtrate to maintain the pH value at 4.5, react for 70 min and then filter to obtain solution A; (2) Adjust the pH of solution A to 2.2 with concentrated sulfuric acid, add 1.195g of sodium nitrite and react for 20min to obtain solution B; (3) Control the flow rate of solution B to pass through the strong acid cation exchange resin 001×7 at a flow rate of 3 BV / h to adsorb and remove chromium ions, and obtain a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 3.0 with concentrated sulfuric acid and ammonia and heat to 70°C. Add ammonium chloride at a molar ratio of ammonium / vanadium of 2.5 times. After reacting for 1 hour, filter to obtain ammonium polyvanadate precipitate. Calcine at 550°C for 3 hours to obtain V2O5. (5) The chromium-containing resin was desorbed with 6% sulfuric acid to obtain a chromium-containing desorbent solution. The pH of the chromium-containing desorbent solution was adjusted to 8.5 with sodium hydroxide to obtain chromium precipitate. The precipitate was then calcined at 450℃ for 2 hours to obtain Cr2O3.

[0027] The total recovery rate and purity of vanadium were measured to be 98.3% and 99.0%, respectively, and the total recovery rate and purity of chromium were 97.2% and 96.5%, respectively. Example 3

[0028] (1) Take 300 mL of vanadium slag water leaching solution, adjust the pH to 11.0 with ammonia water, add 5.8 mL of 2 mol / L aluminum sulfate solution at 70℃, react for 50 min and then filter. Add ammonia water to the filtrate to maintain the pH value at 4.8, react for 80 min and then filter to obtain solution A; (2) Adjust the pH of solution A to 2.4 with concentrated sulfuric acid, add 1.304g of sodium nitrite and react for 30min to obtain solution B; (3) Control the flow rate of solution B to pass through the strong acid cation exchange resin D001 at a flow rate of 2BV / h to adsorb and remove chromium ions, and obtain a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 3.0 with ammonia water and heat it to 60°C. Add ammonium chloride at an ammonium / vanadium molar ratio of 2.2. After reacting for 2 hours, filter to obtain ammonium polyvanadate precipitate. Calcine at 600°C for 3 hours to obtain V2O5. (5) Use 8% hydrochloric acid to desorb the chromium-containing resin to obtain a chromium-containing desorbent solution. Adjust the pH of the chromium-containing desorbent solution to 9.0 with sodium hydroxide to obtain chromium precipitate. Calcine at 500℃ for 3h to obtain Cr2O3.

[0029] The total recovery rate and purity of vanadium were measured to be 99.1% and 99.2%, respectively, and the total recovery rate and purity of chromium were 97.5% and 96.1%, respectively. Example 4

[0030] (1) Take 400 mL of vanadium slag water leaching solution, adjust the pH to 12.0 with ammonia water, add 5.5 mL of 3 mol / L aluminum sulfate solution at 60℃, react for 60 min and then filter. Add ammonia water to the filtrate to maintain the pH value at 5.0, react for 90 min and then filter to obtain solution A; (2) Adjust the pH of solution A to 2.8 with concentrated sulfuric acid, add 1.734g of sodium nitrite and react for 40min to obtain solution B; (3) Control the flow rate of solution B to pass through the strong acid cation exchange resin 001×7 at a flow rate of 4 BV / h to adsorb and remove chromium ions, and obtain a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 3.5 with sodium hydroxide and heat to 80°C. Add ammonium chloride at a molar ratio of ammonium / vanadium of 2.3 times. After reacting for 2 hours, filter to obtain ammonium polyvanadate precipitate. Calcine at 500°C for 4 hours to obtain V2O5. (5) The chromium-containing resin was desorbed with 10% sulfuric acid to obtain a chromium-containing desorbent solution. The pH of the chromium-containing desorbent solution was adjusted to 9.0 with sodium hydroxide to obtain chromium precipitate. Cr2O3 was obtained by calcination at 550℃ for 3h.

[0031] The total recovery rate and purity of vanadium were measured to be 99.3% and 99.4%, respectively, and the total recovery rate and purity of chromium were 98.2% and 95.8%, respectively. Example 5

[0032] (1) Take 1L of vanadium slag water leaching solution, adjust the pH to 10.0 with ammonia water, add 5.5mL of 3mol / L aluminum sulfate solution at 70℃, react for 30min and then filter. Add ammonia water to the filtrate to maintain the pH value at 4.6, react for 60min and then filter to obtain solution A; (2) Adjust the pH of solution A to 3.0 with concentrated sulfuric acid, add 4.335g of sodium nitrite and react for 60min to obtain solution B; (3) Control the flow rate of solution B to pass through the strong acid cation exchange resin D001 at 3BV / h to adsorb and remove chromium ions, and obtain a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 3.5 with sodium hydroxide and heat it to 60°C. Add ammonium chloride at a molar ratio of ammonium / vanadium of 2. After reacting for 2 hours, filter to obtain ammonium polyvanadate precipitate. Calcine at 550°C for 2 hours to obtain V2O5. (5) The chromium-containing resin was desorbed with 6% hydrochloric acid to obtain a chromium-containing desorbent solution. The pH of the chromium-containing desorbent solution was adjusted to 8.5 with sodium hydroxide to obtain chromium precipitate. Cr2O3 was obtained by calcination at 500℃ for 4h.

[0033] The total recovery rate and purity of vanadium were measured to be 98.7% and 99.1%, respectively, and the total recovery rate and purity of chromium were 98.0% and 96.2%, respectively.

[0034] Comparative Example 1 Take 1 L of vanadium slag aqueous leachate, remove silicon according to the method in Example 1, adjust the pH to 2.0 with concentrated sulfuric acid, add 1.985 g of sodium sulfite for reduction, and react at room temperature for 30 min. Adjust the pH to 6.0 with sodium hydroxide solution, maintain this pH at 6.0 for 60 min to allow the reaction to proceed fully, filter after the reaction, and obtain chromium precipitate and vanadium-containing filtrate. Obtain Cr2O3 and V2O5 according to the method in Example 1.

[0035] The total recovery rate and purity of vanadium were measured to be 75.8% and 85.6%, respectively, and the total recovery rate and purity of chromium were 80.4% and 79.4%, respectively.

[0036] Comparative Example 2 Take 300 mL of vanadium slag aqueous leachate, remove silicon according to the method in Example 1, adjust the pH to 0.9 with concentrated sulfuric acid, use N235 as the extractant and kerosene as the diluent for extraction, and obtain a vanadium-containing aqueous phase and a chromium-containing organic phase. Then, back-extract the organic phase with 1 mol / L sodium hydroxide solution to obtain a chromium-containing solution. Cr2O3 and V2O5 are obtained according to the method in Example 1.

[0037] The total recovery rate and purity of vanadium were measured to be 92.4% and 89.9%, respectively, and the total recovery rate and purity of chromium were 90.7% and 88.6%, respectively.

[0038] Comparative Example 3 Take 300 mL of vanadium slag aqueous leachate, remove silicon according to the method in Example 1, adjust the pH to 3.0 with concentrated sulfuric acid, adsorb vanadium and chromium in the solution with D201 resin, and then elute chromium and vanadium stepwise with sodium nitrite solution and sodium hydroxide solution respectively to obtain vanadium-containing solution and chromium-containing solution. Cr2O3 and V2O5 are obtained according to the method in Example 1.

[0039] The total recovery rate and purity of vanadium were measured to be 90.6% and 88.2%, respectively, and the total recovery rate and purity of chromium were 92.3% and 82.5%, respectively.

[0040] Comparative Example 4 The reducing agent used in this comparative example was a 10% ethanol solution, and all other procedures were the same as in Example 1.

[0041] The total recovery rate and purity of vanadium were measured to be 95.0% and 90.7%, respectively, and the total recovery rate and purity of chromium were 88.5% and 89.4%, respectively.

[0042] The recovery rates and purities of vanadium and chromium in Examples 1-5 and Comparative Examples 1-3 are shown in the table below.

[0043] The results showed that, compared with Comparative Examples 1-4, the recovery rates of vanadium and chromium and the purity of the samples were higher in Examples 1-5.

[0044] Compared with the precipitation method in Comparative Examples 1 and the extraction method in Comparative Examples 2, Examples 1-5 of this invention solve the problems of incomplete vanadium-chromium separation, low recovery rate, and high cost in traditional methods through the synergistic innovation of selective reduction, directional adsorption with strong acid cation exchange, and organic solvent-free processes. Simultaneously, it increases the recovery rate of vanadium and chromium, as well as the purity of the products. The recovery rate of vanadium can reach over 98.3%, the recovery rate of chromium can reach over 96.7%, the purity of V2O5 can reach over 99%, and the purity of Cr2O3 can reach over 95.8%. Compared with the anion exchange resin adsorption method in Comparative Example 3, this invention uses directional adsorption with strong acid cation exchange resin. Utilizing the difference in oxidizing properties of vanadium and chromium, selective reduction with sodium nitrite causes vanadium and chromium in the solution to present different valence states. Then, the cation exchange resin adsorbs the positively valenced chromium, which can completely separate vanadium in anionic form and chromium in cationic form, avoiding the reduction in separation efficiency of vanadium-chromium ions due to multi-step desorption, and significantly improving the purity of V2O5 and Cr2O3. Compared to Comparative Example 4, which used ethanol as a reducing agent, sodium nitrite exhibits a faster reaction rate. Sodium nitrite removes Cr₂O₇ from the solution. 2- Reduced to Cr 3+ Vanadium as H2V 10 O 28 4- The anionic form remains in the solution, completing the reduction of hexavalent chromium in a short time, improving the chromium recovery rate, and thus contributing to the improvement of V2O5 purity.

[0045] This invention has only been described with reference to preferred embodiments and does not constitute a limitation on other embodiments. Those skilled in the art can make adaptive adjustments or improvements based on the disclosed technical solutions to form similar embodiments with equivalent technical effects, all of which should be included within the scope of the patent rights of this invention.

Claims

1. A method for separating vanadium and chromium ions from vanadium slag aqueous leachate, characterized in that, Includes the following steps: (1) Adjust the pH of the vanadium slag water leaching solution to 9~12, add aluminum sulfate solution at 50~70℃, the molar ratio of silicon in the vanadium slag water leaching solution to aluminum in aluminum sulfate is 1:1.3~1.6, the reaction time is 30~60min, filter, add ammonia water to the filtrate to maintain pH 4.5~5.0, filter off the aluminum precipitate after 60~90min, and obtain the desiliconized solution A; (2) Adjust the pH of the desilication solution A to 2-3, add a reducing agent with a molar ratio of 1-1.2:1 to chromium in the desilication solution A, and selectively reduce for 10-60 minutes to achieve Cr2O7 2- Reduced to Cr 3+ Vanadium as H2V 10 O 28 4- The form remains unchanged in the solution, resulting in solution B; (3) Solution B is passed through a strong acid cation exchange resin at a flow rate of 2~4 BV / h to adsorb and remove chromium ions, thus obtaining a vanadium-containing solution; (4) Adjust the pH of the vanadium-containing solution to 2.5~3.5, heat it to 60~80℃ and add ammonium chloride. After reacting for 1~2 hours, filter to obtain ammonium polyvanadate precipitate, and calcine to obtain V2O5; (5) Use an eluent to desorb the chromium in the strong acid cation exchange resin in step (3) to obtain a chromium-containing solution. Add sodium hydroxide to adjust the pH to 8-9 to obtain chromium precipitate, and calcine to obtain Cr2O3.

2. The method for separating vanadium and chromium ions in vanadium slag aqueous leaching solution according to claim 1, characterized in that, In step (1), pH adjustment is performed using concentrated sulfuric acid or concentrated hydrochloric acid.

3. The method for separating vanadium and chromium ions in vanadium slag aqueous leachate according to claim 1, characterized in that, In step (2), concentrated sulfuric acid or concentrated hydrochloric acid is used for pH adjustment, and sodium nitrite is used as the reducing agent.

4. The method for separating vanadium and chromium ions in vanadium slag aqueous leachate according to claim 1, characterized in that, In step (3), the strong acid cation exchange resin is D001 or 001×7.

5. The method for separating vanadium and chromium ions in vanadium slag aqueous leaching solution according to claim 1, characterized in that, In step (4), the pH is adjusted using sodium hydroxide or ammonia, and the amount of ammonium chloride added is 2 to 2.5 times the vanadium content in the vanadium-containing solution.

6. The method for separating vanadium and chromium ions in vanadium slag aqueous leaching solution according to claim 1, characterized in that, In step (4), the roasting temperature is 500~600℃ and the time is 2~4h.

7. The method for separating vanadium and chromium ions in vanadium slag aqueous leaching solution according to claim 1, characterized in that, In step (5), the eluent used is hydrochloric acid or sulfuric acid with a concentration of 4-10%.

8. The method for separating vanadium and chromium ions in vanadium slag aqueous leaching solution according to claim 1, characterized in that, In step (5), the roasting temperature is 450~550℃ and the time is 2~4h.

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