Method for extracting vanadium from vanadium precipitation wastewater

Abstract

The invention discloses a method for extracting vanadium from vanadium precipitation wastewater, which belongs to the technical field of metallurgical chemical industry, and comprises the following steps: adding a reducing agent into the vanadium precipitation wastewater to carry out reduction reaction, and adjusting the pH value to be acidic to obtain an extraction stock solution; uniformly mixing dioctyl phosphate and sulfonated kerosene, then adding sodium hydroxide for saponification reaction to obtain an extraction agent, and mixing the extraction agent with the extraction stock solution for extraction to obtain a vanadium-containing organic phase; a sulfuric acid solution is used as a back extraction agent to be mixed with the vanadium-containing organic phase for back extraction, and vanadium-containing back extraction liquid is obtained; the method comprises the following steps: adding vanadium into a vanadium-containing strip liquor, adjusting the pH value of the vanadium-containing strip liquor, adding a precipitator for precipitation reaction to obtain turbid liquid, centrifuging, washing and drying to obtain vanadium precipitate, and the product obtained by the method is low-valence vanadium precipitate, is high in recovery rate and low in impurity content, and is more suitable for preparing electrolyte.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and chemical industry, and particularly relates to a method for extracting vanadium from vanadium precipitation wastewater. Background Art

[0002] In recent years, the all-vanadium liquid flow battery industry has developed rapidly, and the demand for vanadium resources has gradually increased. At present, most of the vanadium is extracted from vanadium slag, which requires roasting, acid leaching, purification and enrichment, and vanadium precipitation. Calcification roasting uses lime as a roasting additive to convert vanadium into calcium vanadate and other forms. After sulfuric acid leaching, a vanadium-containing leachate is obtained, and then vanadium precipitation and calcination are performed to obtain V2O5. However, a large amount of wastewater is generated during the production process, and it also contains a variety of metal elements. The general treatment method is to neutralize the vanadium precipitation wastewater with lime to reduce the content of heavy metal ions, and the neutralized supernatant is returned to the leaching process section. Although this can recycle wastewater, it causes a waste of vanadium resources during the neutralization process. Therefore, an effective method for extracting vanadium from vanadium precipitation wastewater is needed.

[0003] The Chinese patent document with the publication number CN107815549B discloses a method for utilizing vanadium precipitation wastewater, wherein a reducing agent is added to the vanadium precipitation wastewater, the pH of the solution is adjusted after the reaction, and then a first filter residue is obtained by filtering; manganese in the filter residue is leached with an acidic aqueous solution, filtered, and a second filter residue is collected, and then dried, crushed, and roasted, and the roasted clinker is leached to obtain a vanadium-containing leachate, vanadium is precipitated, and ammonium polyvanadate is obtained, which is melted to obtain vanadium pentoxide. This method realizes the recycling of vanadium in vanadium precipitation wastewater, but there are many processes, and two leachings are required, the acid consumption is large, and vanadium loss is easily caused during the leaching process, resulting in an unstable vanadium recovery rate, the lowest of which is 76%, and multiple high-temperature treatments are required during the process, which increases energy consumption.

[0004] A Chinese patent document with publication number CN105016520B discloses a method for recovering vanadium from vanadium precipitation wastewater, wherein the vanadium precipitation wastewater is first adjusted to acidic, then ethanol is added for reaction, a surfactant is then added to combine with vanadium to form a precipitate, and finally the obtained solid is separated from the liquid to achieve the purpose of vanadium precipitation. The method is simple to operate and has a high vanadium precipitation rate, but the surfactant is easily complexed with other impurity ions, resulting in an increase in the content of impurity ions in the generated precipitate.

[0005] The Chinese patent document with publication number CN107502747A discloses a method for extracting vanadium from vanadium precipitation wastewater using microemulsion, wherein the pH of the vanadium precipitation wastewater is adjusted to 6.0-7.0, and then the prepared saturated microemulsion is mixed with the vanadium precipitation wastewater to extract the vanadium. The method has a short process flow and is simple to operate, but the extraction rate is low, and the extracted vanadium appears in the organic phase and cannot be directly used. Summary of the invention

[0006] The purpose of the present invention is to provide a method for extracting vanadium from vanadium precipitation wastewater. In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for extracting vanadium from vanadium precipitation wastewater, the specific steps are as follows: (1) adding a reducing agent to the vanadium precipitation wastewater for reduction reaction, and adjusting the pH value to acidic to obtain an extract solution; (2) mixing dioctyl phosphate and sulfonated kerosene uniformly, adding sodium hydroxide to carry out saponification reaction to obtain an extractant, and mixing the extractant with the extraction stock solution to carry out extraction to obtain a vanadium-containing organic phase; (3) Using sulfuric acid solution as a stripping agent and mixing it with the vanadium-containing organic phase for stripping to obtain a vanadium-containing stripping solution; adjusting the pH value of the vanadium-containing stripping solution, and then adding a precipitant to carry out a precipitation reaction to obtain a suspension, which is then centrifuged, washed, and dried to obtain a vanadium precipitate.

[0007] Furthermore, in step (1), the reducing agent is at least one of sodium sulfite or sulfurous acid, the reduction reaction time is 2 to 6 hours, and the molar ratio of the reducing agent to the vanadium in the vanadium precipitation wastewater is 0.5 to 2:1.

[0008] Furthermore, in the step (2), the saponification rate of the saponification reaction is 20-70%.

[0009] Furthermore, in step (2), the ratio of the extractant to the original extract solution (O / A) is 3 to 0.5:1. Furthermore, in step (3), the concentration of sulfuric acid is 1-3 mol / L, the ratio of the vanadium-containing organic phase to sulfuric acid (O / A) is 1:0.5-3; the pH value is 3.0-6.0; the precipitant is at least one of hydrazine or sodium dithionite, the molar ratio of the precipitant to the vanadium in the vanadium-containing stripping solution is 0.8-1.5:1, and the precipitation reaction time is 3-8 hours.

[0010] Compared with the prior art, the present invention has the following beneficial effects: 1. The prior art requires that vanadium in vanadium precipitation wastewater be enriched and then roasted, and then leached, precipitated, and melted to obtain vanadium pentoxide. This method consumes a large amount of sulfuric acid, and multiple leaching easily causes vanadium loss, resulting in a low vanadium recovery rate. The present invention does not require a leaching stage, and directly precipitates vanadium at a specific pH, thereby reducing vanadium loss and obtaining vanadium solids without high-temperature treatment, thereby improving vanadium recovery rate, reducing sulfuric acid consumption, reducing energy consumption, and reducing costs.

[0011] 2. The surfactant added in the prior art for vanadium precipitation is also easy to complex with other impurity ions when complexing with vanadium, resulting in an increase in the impurity content of the product. The present invention can remove most of the impurity ions in the vanadium precipitation wastewater through the process of extraction-stripping, and finally through precipitation and washing, which can further reduce the impurity ions, thereby reducing impurities while ensuring the vanadium recovery rate.

[0012] 3. The valence state of vanadium after vanadium extraction in the prior art is pentavalent. The present invention utilizes the characteristic that low-valent vanadium is easier to precipitate from the solution than pentavalent vanadium at a specific pH value. Hydrazine or sodium dithionite is used to precipitate low-valent vanadium in the pH range of 3.0 to 6.0. The solubility of low-valent vanadium in sulfuric acid is higher than that of pentavalent vanadium, which is beneficial to improving the vanadium recovery rate.

[0013] 4. The product obtained by the present invention is a low-valent vanadium precipitate. Compared with pentavalent vanadium, in the process of preparing vanadium electrolyte, firstly, it is not necessary to adjust the valence state, and secondly, the solubility in sulfuric acid is higher, which is more conducive to the preparation of vanadium electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the process of extracting vanadium from vanadium precipitation wastewater in an embodiment of the present invention; DETAILED DESCRIPTION

[0015] The technical solution of the present invention is further described below in conjunction with specific embodiments. It is worth noting that the protection scope of the present invention is not limited to the examples involved, and modifications or improvements made according to the ideas of the present invention all fall within the scope of protection claimed by the present invention.

[0016] In the following examples and comparative examples, the recovery rate of vanadium and the impurity content of the vanadium precipitate were obtained by dissolving the solid in a sulfuric acid solution and then measuring the ICP.

[0017] Example 1

[0018] 0.65 g of sodium sulfite was added to 500 mL of vanadium precipitation wastewater, and the solution was stirred for reduction for 2 hours, and the pH of the solution was adjusted to 1.8 to obtain an extractant; dioctyl phosphate was mixed with sulfonated kerosene to prepare an extractant, the volume concentration of dioctyl phosphate was 10%, and it was saponified with sodium hydroxide for 10 minutes to obtain an extractant with a saponification rate of 20%, and then the extractant was extracted at a ratio (O / A) of 3:1 to obtain a vanadium-containing organic phase; the obtained vanadium-containing organic phase was stripped with 1 mol / L sulfuric acid, the ratio (O / A) was 1:0.5, and the stripping time was 10 minutes to obtain a vanadium-containing stripping solution; the pH of the vanadium-containing stripping solution was adjusted to 3.0 with sodium hydroxide and 0.25 g of hydrazine was added to react for 3 hours, and the solution pH was adjusted to 3.0 with sulfuric acid or sodium hydroxide during the reaction; after the reaction, the solid and liquid were separated by a centrifuge, and the obtained solid was washed 4 times with 2 mmol / L dilute sulfuric acid to obtain a vanadium precipitate, and then the vanadium precipitate was placed in a vacuum oven for drying and storage. The vanadium recovery rate was measured to be 94.2% and the impurity ion content was 0.7%. Example 2

[0019] 1.30 g of sodium sulfite was added to 500 mL of vanadium precipitation wastewater, and the solution was stirred for reduction for 3 hours, and the pH of the solution was adjusted to 2.0 to obtain an extractant; dioctyl phosphate was mixed with sulfonated kerosene to prepare an extractant, the volume concentration of dioctyl phosphate was 20%, and it was saponified with sodium hydroxide for 20 minutes to obtain an extractant with a saponification rate of 40%, and then the extractant was extracted at a ratio (O / A) of 2:1 to obtain a vanadium-containing organic phase; the obtained vanadium-containing organic phase was stripped with 2 mol / L sulfuric acid, the ratio (O / A) was 1:1, and the stripping time was 10 minutes to obtain a vanadium-containing stripping solution; the pH of the vanadium-containing stripping solution was adjusted to 4.0 with sodium hydroxide and 0.31 g of hydrazine was added to react for 4 hours, and the solution pH was adjusted to 4.0 with sulfuric acid or sodium hydroxide during the reaction; after the reaction, the solid and liquid were separated by a centrifuge, and the obtained solid was washed 3 times with 4 mmol / L dilute sulfuric acid to obtain a vanadium precipitate, and then the vanadium precipitate was placed in a vacuum oven for drying and storage. The vanadium recovery rate was measured to be 94.0%, and the impurity ion content was 0.7%. Example 3

[0020] 1.27 g of sulfurous acid was added to 500 mL of vanadium precipitation wastewater, and the pH of the solution was adjusted to 2.2 after stirring and reducing for 4 hours to obtain an extractant; dioctyl phosphate was mixed with sulfonated kerosene to prepare an extractant, the volume concentration of dioctyl phosphate was 30% (V / V), and it was saponified with sodium hydroxide for 30 minutes to obtain an extractant with a saponification rate of 50%, and then the extractant was extracted at a ratio of 1:1 to the extractant and the extractant solution (O / A) to obtain a vanadium-containing organic phase; the obtained vanadium-containing organic phase was treated with 3 mol / L sulfuric acid. The organic phase was stripped with a phase ratio (O / A) of 1:1 and a stripping time of 10 min to obtain a vanadium-containing stripping solution; the pH of the vanadium-containing stripping solution was adjusted to 5.0 with sodium hydroxide and 2.00 g of sodium dithionite was added to react for 6 h, and the pH of the solution was adjusted to 5.0 with sulfuric acid or sodium hydroxide during the reaction; after the reaction, the solid and liquid were separated by a centrifuge, and the obtained solid was washed 3 times with 7 mmol / L dilute sulfuric acid to obtain a vanadium precipitate, which was then placed in a vacuum oven for drying and storage. The vanadium recovery rate was measured to be 94.9%, and the impurity ion content was 0.5%. Example 4

[0021] 1.30 g of sodium sulfite and 0.85 g of sulfurous acid were added to 500 mL of vanadium precipitation wastewater, and the pH of the solution was adjusted to 2.4 after stirring for 5 hours to obtain an extractant; dioctyl phosphate was mixed with sulfonated kerosene to prepare an extractant, and the volume concentration of dioctyl phosphate was 30% (V / V) to prepare the extractant, and it was saponified with sodium hydroxide for 50 minutes to obtain an extractant with a saponification rate of 60%, and then the extractant was extracted at a ratio of 0.5:1 to the extractant and the extractant solution (O / A) to obtain a vanadium-containing organic phase; 3 mol / L The obtained vanadium-containing organic phase was stripped with 1000 L of sulfuric acid, the phase ratio (O / A) was 1:2, the stripping time was 10 min, and the vanadium-containing stripping solution was obtained; the pH of the vanadium-containing stripping solution was adjusted to 6.0 with sodium hydroxide and 2.03 g of sodium dithionite was added, and the reaction was performed for 8 hours. During the reaction, the solution pH was adjusted to 6.0 with sulfuric acid or sodium hydroxide; after the reaction, the solid and liquid were separated by a centrifuge, and the obtained solid was washed twice with 8 mmol / L of dilute sulfuric acid to obtain a vanadium precipitate, which was then placed in a vacuum oven for drying and storage. The vanadium recovery rate was measured to be 94.4%, and the impurity ion content was 0.6%. Example 5

[0022] 1.23 g of sulfurous acid was added to 500 mL of vanadium precipitation wastewater, and the solution was stirred for reduction for 6 hours, and the pH of the solution was adjusted to 2.2 to obtain an extractant; dioctyl phosphate was mixed with sulfonated kerosene to prepare an extractant, and the volume concentration of dioctyl phosphate was 20% (V / V) to prepare the extractant, and it was saponified with sodium hydroxide for 60 minutes to obtain an extractant with a saponification rate of 70%, and then the extractant was extracted at a ratio of 1:1 to the extractant and the extractant solution (O / A) to obtain a vanadium-containing organic phase; the obtained vanadium-containing organic phase was treated with 1.5 mol / L sulfuric acid. The organic phase was stripped with a phase ratio (O / A) of 1:3 and a stripping time of 10 min to obtain a vanadium-containing stripping solution; the pH of the vanadium-containing stripping solution was adjusted to 5.0 with sodium hydroxide and 0.31 g of hydrazine and 0.85 g of sodium dithionite were added to react for 8 h, and the pH of the solution was adjusted to 5.0 with sulfuric acid or sodium hydroxide during the reaction; after the reaction, the solid and liquid were separated by a centrifuge, and the obtained solid was washed twice with 10 mmol / L dilute sulfuric acid to obtain a vanadium precipitate, which was then placed in a vacuum oven for drying and storage. The vanadium recovery rate was measured to be 95.4%, and the impurity ion content was 0.4%. Comparative Example 1

[0023] Add 3.5g of anhydrous sodium sulfite to 2L of vanadium precipitation wastewater, react for 2h, add sodium hydroxide to adjust the solution pH to 8.0, and filter to obtain filter residue A; add 500mL of 15% sulfuric acid solution to filter residue A for leaching, and then filter to obtain filter residue B; dry filter residue B, add 1.0g of calcium oxide, mix and roast at 500℃, and leach the roasted solid with 10% sulfuric acid solution, with a solid-liquid ratio of 1:3 to obtain vanadium-containing leaching solution; add ammonium sulfate to the vanadium-containing leaching solution and adjust the solution pH to 2.0, precipitate vanadium at 95℃ for 60min, obtain ammonium polyvanadate, and then melt to obtain 3.17g of vanadium pentoxide product. The vanadium recovery rate was measured to be 83.6%, and the impurity content was 1.4% Comparative Example 2

[0024] 500mL of vanadium precipitation wastewater was measured and adjusted to pH 3.0, and the prepared 0.05mol / L dodecylamine ethanol solution was mixed with the vanadium precipitation wastewater at a volume ratio of 1:1; stirred at room temperature for 60min and then allowed to stand for 30min, the solid was filtered out, washed with ethanol 3 times and dried to obtain a vanadium-containing solid. The vanadium recovery rate was measured to be 85.1%, and the impurity content was 10.3%. The vanadium recovery rates and impurity contents of Examples 1 to 5 and Comparative Examples 1 to 2 are listed in Table 1.

[0025]

[0026] The results show that the vanadium recovery rate in Examples 1 to 5 is about 94%, and the impurity ion content is less than 1%, because before vanadium precipitation, most of the impurity ions in the vanadium precipitation wastewater are removed by the extraction-stripping process, reducing the adsorption of other impurity ions during the precipitation process and increasing the purity of the product; the vanadium is precipitated by utilizing the characteristic that low-valent vanadium is easily precipitated from the solution at a specific pH value, which is a spontaneous process, so the recovery rate is relatively high; finally, the vanadium precipitate is washed with dilute sulfuric acid to further reduce the impurity ion content. The solid obtained by the present invention is a low-valent vanadium precipitate. In the process of preparing the electrolyte, compared with pentavalent vanadium, it is not necessary to adjust the vanadium valence state, and it is more soluble in sulfuric acid, which is conducive to the preparation of vanadium electrolyte. Comparative Example 1 has lost a part of vanadium after multiple precipitation-leaching processes from vanadium precipitation wastewater to vanadium pentoxide. Although vanadium pentoxide solid is finally obtained, the vanadium recovery rate is not high, resulting in waste of resources and high cost. Comparative Example 2 uses a complexing agent to precipitate vanadium. This method improves the recovery rate of vanadium to a certain extent, but it also combines with other impurity ions while complexing the vanadium, resulting in an increase in the impurity ion content of the solid complex.

Claims

1. A method for extracting vanadium from vanadium precipitation wastewater, characterized in that: The following steps are involved: (1) adding a reducing agent to the vanadium precipitation wastewater for reduction reaction, and adjusting the pH value to acidic to obtain an extract solution; (2) mixing dioctyl phosphate and sulfonated kerosene uniformly, adding sodium hydroxide to carry out saponification reaction to obtain an extractant, and mixing the extractant with the extraction stock solution to carry out extraction to obtain a vanadium-containing organic phase; (3) using a sulfuric acid solution as a stripping agent and mixing it with the vanadium-containing organic phase for stripping to obtain a vanadium-containing stripping solution; The pH value of the vanadium-containing stripping solution is adjusted, and a precipitant is added to perform a precipitation reaction to obtain a suspension, which is then centrifuged, washed, and dried to obtain a vanadium precipitate.

2. The method for extracting vanadium from vanadium precipitation wastewater according to claim 1, characterized in that: In the step (1), the reducing agent is at least one of sodium sulfite or sulfurous acid, the reduction reaction time is 2 to 6 hours, and the molar ratio of the reducing agent to the vanadium in the vanadium precipitation wastewater is 0.5 to 2:

1.

3. The method for extracting vanadium from vanadium precipitation wastewater according to claim 1, characterized in that: In the step (2), the saponification rate of the saponification reaction is 20-70%.

4. The method for extracting vanadium from vanadium precipitation wastewater according to claim 1, characterized in that: In the step (2), the ratio of the extractant to the original extraction solution (O / A) is 3-0.5:

1.

5. The method for extracting vanadium from vanadium precipitation wastewater according to claim 1, characterized in that: In the step (3), the concentration of the sulfuric acid solution is 1-3 mol / L, the ratio of the vanadium-containing organic phase to the sulfuric acid solution (O / A) is 1:0.5-3; the pH value is 3.0-6.0; the precipitant is at least one of hydrazine or sodium dithionite, the molar ratio of the precipitant to the vanadium in the vanadium-containing stripping solution is 0.8-1.5:1, and the precipitation reaction time is 3-8 hours.

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