Method for recovering vanadium from waste catalyst and application thereof

Abstract

The invention relates to the technical field of waste catalyst treatment, and discloses a method for recovering vanadium from a waste catalyst and application of the method, the method comprises the following steps: (1) the waste catalyst is contacted with an organic acid solution for leaching, and a leaching solution is obtained; wherein in the waste catalyst, in terms of V2O5, the content of V is not less than 25 wt%; (2) adjusting the pH value of the leachate to be not higher than 4, and then adding an oxidizing agent for reaction to obtain a raw material solution; wherein the molar ratio of the oxidizing agent to the organic acid is (0.2-0.6): 1; (3) contacting the raw material liquid with an extracting agent, and extracting to obtain a V-containing extracting solution; (4) washing the extract liquor by adopting an acid solution, and then carrying out reverse extraction to obtain a V-rich solution; wherein the concentration of the acid solution is 0.1 mol / L to 2.5 mol / L. The method has the characteristics that the process flow is simple, and the recovered product V has high purity and high yield.

Description

Technical Field

[0001] This invention relates to the field of spent catalyst treatment technology, and specifically to a method for recovering vanadium from spent catalysts and its application. Background Technology

[0002] Vanadium is a rare metal characterized by its high melting point and low density. In steelmaking, trace amounts of vanadium can significantly improve the strength of steel; in the chemical industry, vanadium is widely used as a catalyst; and in the new energy field, vanadium redox flow batteries, as aqueous batteries, offer high safety and can be used in large-scale energy storage systems.

[0003] Waste catalysts used in petroleum processing, especially hydrodemetallization catalysts from waste residue oil, often have high levels of vanadium (V) deposits. Effective recovery and reuse of these metals from waste catalysts would facilitate the resource utilization of waste hydrotreating catalysts. From a petroleum processing perspective, while refining petroleum fully utilizes hydrocarbons, the deposition of vanadium on catalysts and its initial enrichment, followed by purification and recovery through solvent extraction, also improves the efficiency of petroleum resource utilization.

[0004] CN105274344A discloses a method for recovering molybdenum and vanadium from waste petroleum catalysts. The method includes: sequentially deoiling the waste catalyst by air burning, pulverizing, calcining after mixing with sodium carbonate, then leaching the resulting calcined material with water and adjusting the pH of the leaching solution to alkaline, adding ammonium chloride to the leaching solution to precipitate vanadium, and finally enriching the vanadium-precipitated solution using ion exchange to obtain an ammonium molybdate solution. While these processes can improve molybdenum recovery efficiency, their operation is complex, generates significant amounts of waste, and incurs high treatment costs. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of complex vanadium recovery processes, high extractant usage, and large amounts of waste emissions in existing technologies. This invention provides a method for recovering vanadium from waste catalysts and its application. This method features a simple process flow and a recovery product V with both high and low purity and yield.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for recovering vanadium from spent catalysts, the method comprising:

[0007] (1) The waste catalyst was leached by contacting an organic acid solution to obtain a leachate containing Mo and V;

[0008] The waste catalyst contains V, calculated as V2O5, at a content of not less than 25 wt%.

[0009] The leachate includes V and optionally at least one of Mo, Al, Fe, Co, and Ni;

[0010] (2) Adjust the pH of the leachate to be no higher than 4, and then add an oxidant to react and obtain a raw material solution; wherein the molar ratio of the oxidant to the organic acid is (0.2-0.6):1;

[0011] (3) The raw material liquid is contacted with the extractant to extract and obtain an extract containing V;

[0012] (4) The extract is washed with an acid solution and then back-extracted to obtain a V-rich solution; wherein the concentration of the acid solution is 0.1-2.5 mol / L.

[0013] The second aspect of the present invention provides the application of the above-described method for recovering vanadium from spent catalysts in the treatment of waste oil hydrotreating catalysts.

[0014] The complex composition of metal elements in industrial waste catalysts, especially the presence of molybdenum (Mo) in waste hydrogenation catalysts, can affect vanadium (V) recovery during extraction. This invention addresses this issue by using an organic acid solution to leach the waste catalyst, followed by an oxidant to break down the organic acid complexing agent. An extractant is then used to achieve one-step extraction of V from the solution. The extracted phase is washed with low acid and then back-extracted to obtain purified V components with a purity exceeding 99%. The method proposed in this invention can effectively and selectively extract vanadium from waste catalyst leachates containing organic acid complexing agents. The process is simple, the operating conditions are mild, and it is easily implemented industrially. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of the present invention provides a method for recovering vanadium from spent catalysts, the method comprising:

[0017] (1) The waste catalyst was leached by contacting an organic acid solution to obtain a leachate containing Mo and V;

[0018] The waste catalyst contains V, calculated as V2O5, at a content of not less than 25 wt%.

[0019] The leachate includes V and optionally at least one of Mo, Al, Fe, Co, and Ni;

[0020] (2) Adjust the pH of the leachate to be no higher than 4, and then add an oxidant to react and obtain a raw material solution; wherein the molar ratio of the oxidant to the organic acid is (0.2-0.6):1;

[0021] (3) The raw material liquid is contacted with the extractant to extract and obtain an extract containing V;

[0022] (4) The extract is washed with an acid solution and then back-extracted to obtain a V-rich solution; wherein the concentration of the acid solution is 0.1-2.5 mol / L.

[0023] In existing technologies, strong acid solutions are typically used to leach metal components from spent catalysts. However, when organic acids are used for leaching, the presence of complexing agents in the leachate makes it difficult to directly extract vanadium. In this invention, step (2) treats the leachate, which breaks down the organic acid complexing agents. Based on this, an extractant is then used to achieve one-step extraction of V from the solution, significantly reducing the difficulty of metal extraction. After washing with an acid solution and then back-extraction, other metal components such as Mo that may be present in the extractate can be removed, resulting in purified V with a purity higher than 99%.

[0024] This invention does not have special requirements regarding the source of the spent catalyst; any spent industrial catalyst containing a certain amount of V can be used in the method provided by this invention, wherein the V content, calculated as V₂O₅, is not less than 25 wt%. In particular, spent residue oil hydrotreating catalysts obtained during petroleum processing, especially spent residue oil hydrodemetallization catalysts, typically use Mo as the active metal component and exhibit high V deposition after long-term use. In existing technologies, the simultaneous presence of Mo and V may affect the selective extraction effect of V. The method provided by this invention is particularly suitable for recovering V from the aforementioned spent catalysts, overcoming the influence of Mo and achieving a high recovery and purification effect.

[0025] According to the present invention, preferably, the content of V in the spent catalyst, calculated as V2O5, is 25-50 wt%.

[0026] According to some preferred embodiments of the present invention, the method further includes: calcining the spent catalyst and then contacting it with an organic acid solution. The calcination can be carried out using conventional methods in the art to remove carbon deposits on the spent catalyst, which is beneficial for further improving the metal leaching rate.

[0027] Preferably, the calcination conditions include a temperature of 500-750℃, more preferably 550-650℃, and a time of 2-6 hours. Using the above-mentioned preferred embodiments is beneficial for the efficient removal of adsorbed sludge and carbon deposits from the waste catalyst, and for converting the active phase of metal sulfides into oxides, which is beneficial for improving the leaching rate of V.

[0028] In this invention, step (1) involves leaching the spent catalyst by contacting it with an organic acid solution. The organic acid acts as a complexing agent, which facilitates the selective leaching of V from the catalyst. After the leachate is treated as described in step (2), it is beneficial for the subsequent extraction step. The leachate may also contain other metal elements from the catalyst, such as Mo, Al, Fe, Co, Ni, etc. This invention does not have any particular limitations on this.

[0029] According to some preferred embodiments of the present invention, in step (1), the organic acid is selected from at least one of acetic acid, oxalic acid, citric acid, and ethylenediaminetetraacetic acid. Using the above-mentioned preferred organic acids is beneficial for further improving the leaching rate of V.

[0030] According to the present invention, preferably, the concentration of the organic acid solution is 0.5-4 mol / L, for example, it can be a specific but not limiting concentration value or any range between 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, etc., and preferably, the concentration of the organic acid solution is 1-3.5 mol / L.

[0031] Preferably, the solvent in the organic acid solution is water.

[0032] In this invention, the range of the amount of organic acid solution used is relatively wide, as long as it can fully leach V and Mo from the waste catalyst. Preferably, the ratio of the volume of the organic acid solution (mL) to the mass (g) of the waste catalyst is 10-50:1, and more preferably 15-40:1.

[0033] According to the present invention, preferably, the content of V in the leachate is 5000-20000 mg / kg, more preferably 10000-20000 mg / kg. When the leachate also contains other metal components such as Mo, Al, Fe, Co, and Ni, the total amount of other metals such as Mo, Al, Fe, Co, and Ni is 2000-10000 mg / kg, more preferably 2000-5000 mg / kg.

[0034] According to the present invention, by adjusting the pH of the leachate to be no higher than 4 in step (2), preferably 0.2-4, more preferably 0.5-1.5, for example, specific pH values ​​or any range between 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, etc., and then adding an oxidant to react, the complexation of organic acids in the leachate can be destroyed, thereby further improving the purity of vanadium.

[0035] According to the present invention, preferably, the method for adjusting the pH of the leachate includes: mixing the leachate with an acid.

[0036] The present invention does not particularly limit the type of acid, but preferably, the acid is selected from at least one of hydrochloric acid, sulfuric acid and nitric acid.

[0037] According to some preferred embodiments of the present invention, the molar ratio of the oxidant to the organic acid is (0.2-0.6):1, for example, it can be a specific but not limiting molar ratio or any range between two such ratios, such as 0.2:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.6:1, etc. Preferably, the molar ratio of the oxidant to the organic acid is (0.3-0.5):1. Using the above preferred embodiments is beneficial for further improving the yield of vanadium.

[0038] In this invention, the selection range of the oxidant is relatively wide, and any conventional oxidant in the art can be used. Preferably, the oxidant is selected from at least one of hydrogen peroxide, ferric sulfate, potassium perchlorate, potassium permanganate, and ozone.

[0039] According to the present invention, the reaction is carried out under stirring conditions, preferably at a temperature of 20-50°C, for example at room temperature, for a time of 0.1-3 hours.

[0040] According to some preferred embodiments of the present invention, step (3) further includes first adjusting the pH of the raw material solution to 1-3, preferably 1.5-2.2, and then contacting it with the extractant for extraction. The present invention does not particularly limit the method of pH adjustment; acid or alkali may be added appropriately according to the initial pH of the raw material solution to meet the above-mentioned pH range. The added acid may be, for example, sulfuric acid, and the alkali may be, for example, sodium hydroxide.

[0041] In this invention, the selection range of the extractant is relatively wide, and any conventional anionic extractant in the art can be used. Preferably, the anionic extractant is selected from at least one of P204, P507, TBP, N235, and A336.

[0042] Generally, the extractant is diluted with an organic solvent before extraction. Preferably, the extractant is provided by an extractant solution with a mass concentration of 10-30%.

[0043] Preferably, the solvent in the extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol.

[0044] According to the present invention, preferably, the volumetric flow rate ratio of the feed liquid to the extractant solution is 1-3:1, for example, it can be a specific but not limiting flow rate ratio such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, or any range between the two. Preferably, the volumetric flow rate ratio of the feed liquid to the extractant solution is 1.5-2.5:1. Using the above preferred embodiments is beneficial for further improving the extraction effect and increasing the purity and yield of V.

[0045] The present invention does not have any particular limitation on the specific operation method of the extraction. In order to further improve the recovery efficiency, preferably, the co-extraction in step (3) is a multi-stage countercurrent extraction, and the number of extraction stages is preferably 3-5 stages.

[0046] The present invention allows for a wide range of acid selection for the acid solution in step (4), which can be at least one of hydrochloric acid, sulfuric acid, and nitric acid. Preferably, the acid used in step (4) is the same type of acid used to adjust the pH in step (2). Under these preferred conditions, the introduction of more heteroatoms can be avoided, improving product purity while reducing waste emissions and enhancing the economic efficiency of the process. More preferably, the acid used in both steps (4) and (2) is sulfuric acid.

[0047] In the washing process described in step (4), by controlling the concentration of the acid solution, other metal components such as Mo in the extract can be selectively removed, thereby obtaining a V-rich solution through one-step back-extraction. Preferably, the concentration of the acid solution is 0.1-2.5 mol / L, for example, it can be a specific concentration or any range between 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.3 mol / L, or 2.5 mol / L. Preferably, the concentration of the acid solution is 0.3-0.8 mol / L. Using the above preferred embodiment is beneficial for achieving both high V purity and yield.

[0048] According to some preferred embodiments of the present invention, the volumetric flow rate ratio of the V-containing extract to the detergent is 0.5-1.5:1, for example, it can be a specific but not limiting ratio or any range between two such ratios, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, etc. Preferably, the volumetric flow rate ratio of the V-containing extract to the detergent is 0.6-1.2:1. In the above preferred cases, it is advantageous to achieve both high V purity and yield.

[0049] Preferably, the washing is a multi-stage washing process, and the number of washing stages is preferably 3-5 stages.

[0050] According to the present invention, preferably, in step (4), the back-extraction includes: mixing the washed feed liquid with the back-extraction agent.

[0051] This invention allows for a wide range of choices for the back-extraction agent, and conventional back-extraction agents in the art can be used to extract V from the organic phase to the aqueous phase. Preferably, the back-extraction agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%.

[0052] Preferably, the back-extraction is carried out in a multi-stage back-extraction manner, with the number of stages preferably being 3-6 stages.

[0053] Preferably, the volumetric flow rate ratio of the washed feed liquid to the stripping agent is 0.5-3:1, more preferably 0.7-1:1.

[0054] According to some preferred embodiments of the present invention, the method further includes: recovering the extractant after back-extraction in step (4). The recovered extractant can be reused in the extraction process of step (3). Adopting the above preferred embodiments helps to reduce emissions of waste gas, wastewater, and solid waste, and lower process costs.

[0055] The second aspect of the present invention provides the application of the above-described method for recovering vanadium from spent catalysts in the treatment of waste oil hydrotreating catalysts.

[0056] The present invention will be described in detail below through embodiments.

[0057] The waste catalyst used in the following examples is a waste residue oil hydrogenation catalyst, whose composition includes: V content of 40.6 wt% (based on V2O5), Mo content of 5.6 wt% (based on MoO3), Ni content of 9.8 wt% (based on NiO), Al content of 22.9 wt% (based on Al2O3), Fe content of 4.8 wt% (based on Fe2O3), Ca content of 1.2 wt% (based on CaO), Na content of 0.8 wt% (based on Na2O), and other elements such as Si and P.

[0058] Example 1

[0059] (1) The waste catalyst was calcined at 600℃ for 3h, and then mixed with 3mol / L oxalic acid solution at a ratio of solution volume (mL) to the mass (g) of the waste catalyst of 20:1 to obtain a metal leachate. The composition of the leachate includes: 10034mg / kg V, 1710mg / kg Mo, 3149mg / kg Al, 184mg / kg Fe and 23mg / kg Ni.

[0060] (2) Add sulfuric acid to the leachate to control the pH to 1.5, then add potassium permanganate and mix and stir at room temperature for 0.5 h. The molar ratio of potassium permanganate to oxalic acid is 0.4:1.

[0061] (3) Adjust the pH of the aqueous phase to 2.1. Dissolve A336 and TBP in hydrogenated kerosene, wherein the mass fraction of A336 is 10 wt% and the mass fraction of TBP is 10 wt%, as the extraction organic phase. The aqueous phase prepared in step (2) flows from stage 4 to stage 1 of the extraction tank, the extractant flows in from stage 1, and the washing agent is a 0.5 mol / L sulfuric acid solution, which flows in from stage 9. The extraction phase enters the back-extraction section and is back-extracted for 4 stages with a 20 wt% sodium carbonate solution to obtain product V. The flow ratio of the extraction process is A / O = 2, the flow ratio of the washing process is A / O = 1, and the flow ratio of the back-extraction stage is A / O = 0.8.

[0062] According to ICP testing, V / M in product V 总 =99.5wt%, based on the total amount of V in the leachate, the yield of V is 96wt%.

[0063] Example 2

[0064] (1) The waste catalyst was calcined at 600℃ for 3h, and then mixed with 3mol / L oxalic acid solution at a ratio of solution volume (mL) to the mass (g) of the waste catalyst of 20:1 to obtain a metal leachate. The composition of the leachate includes: 10034mg / kg V, 1710mg / kg Mo, 3149mg / kg Al, 184mg / kg Fe and 23mg / kg Ni.

[0065] (2) Add sulfuric acid to the leachate to control the pH to 1.2, then add potassium permanganate and mix and stir at room temperature for 0.5 h. The molar ratio of potassium permanganate to oxalic acid is 0.5:1.

[0066] (3) Adjust the pH of the aqueous phase to 1.8. Dissolve N235 and n-octanol in hydrogenated kerosene, wherein the mass fraction of N235 is 15 wt% and the mass fraction of n-octanol is 10 wt%, as the extraction organic phase. The aqueous phase prepared in step (2) flows from stage 3 to stage 1 of the extraction tank, the extractant flows in from stage 1, and the washing agent is a 0.3 mol / L sulfuric acid solution, which flows in from stage 9. The extraction phase enters the back-extraction section and is back-extracted for 4 stages with a 20 wt% sodium carbonate solution to obtain product V. The flow ratio of the extraction process is A / O = 2, the flow ratio of the washing process is A / O = 1, and the flow ratio of the back-extraction stage is A / O = 0.8.

[0067] According to ICP testing, V / M in product V 总 =99.9wt%, based on the total amount of V in the leachate, the yield of V is 92wt%.

[0068] Example 3

[0069] The method is the same as in Example 1, except that in step (2), the molar ratio of potassium permanganate to organic acid is 0.2:1.

[0070] Following step (3) of the method in Example 1, product V was obtained. ICP testing revealed that product V contained V / M... 总 = 99.4 wt%, based on the total amount of V in the leachate, the yield of V is 85 wt%.

[0071] Example 4

[0072] The method was followed as in Example 1, except that in step (3), the detergent was a 1 mol / L sulfuric acid solution. Product V was obtained. ICP testing showed that the V / M ratio in product V was... 总 =99.7wt%, based on the total amount of V in the leachate, the yield of V is 92wt%.

[0073] Example 5

[0074] The method is the same as in Example 1, except that the pH of the solution is controlled to be 2.5 in step (3).

[0075] Following step (3) of the method in Example 1, product V was obtained. ICP testing revealed that product V contained V / M... 总 = 98.3 wt%, based on the total amount of V in the leachate, the yield of V is 99 wt%.

[0076] Comparative Example 1

[0077] The method is the same as in Example 1, except that in step (2), sulfuric acid is added to the leachate, the pH is controlled to 1.5, and then the extraction in step (3) is carried out directly without adding potassium permanganate.

[0078] Following step (3) of the method in Example 1, product V was obtained. ICP testing revealed that product V contained V / M... 总 = 99.6 wt%, based on the total amount of V in the leachate, the yield of V is 15 wt%.

[0079] Comparative Example 2

[0080] The method of Example 1 is different except that in step (1), the calcined waste catalyst is mixed with 4 mol / L sulfuric acid solution at a ratio of solution volume (mL) to the mass (g) of the waste catalyst of 20:1 for leaching to obtain a metal leachate. The composition of the leachate includes: 6046 mg / kg V, 1652 mg / kg Mo, 4762 mg / kg Al, 657 mg / kg Fe and 168 mg / kg Ni.

[0081] Steps (2) and (3) were performed according to the method of Example 1, except that potassium permanganate was added to the feed solution, but sulfuric acid was not added. Product V was obtained. ICP testing showed that the V / M ratio in product V was... 总 = 99.7 wt%, based on the total amount of V in the leachate, the yield of V is 84 wt%.

[0082] The comparison of the above examples and comparative examples shows that the method for recovering vanadium from spent catalysts provided by the present invention can recover vanadium through one-step extraction in a metal leaching solution containing an organic acid complexing agent, with high vanadium purity and yield. The comparison of Example 1, Comparative Example 1, and Comparative Example 2 shows that leaching spent catalyst metals with organic acids can improve the leaching rate of vanadium. Further treatment with an oxidant allows for one-step extraction recovery of vanadium. Through the overall coordination of the leaching and extraction processes, a high extraction rate, yield, and purity of vanadium can be achieved.

[0083] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for recovering vanadium from spent catalysts, characterized in that, The method includes: (1) The waste catalyst is leached by contacting an organic acid solution to obtain a leachate; The waste catalyst contains V, calculated as V2O5, at a content of not less than 25 wt%. The leachate includes V and optionally at least one of Mo, Al, Fe, Co, and Ni; (2) Adjust the pH of the leachate to be no higher than 4, and then add an oxidant to react and obtain a raw material solution; wherein the molar ratio of the oxidant to the organic acid is (0.2-0.6):1; (3) The raw material liquid is contacted with the extractant to extract and obtain an extract containing V; (4) The extract is washed with an acid solution and then back-extracted to obtain a V-rich solution; wherein the concentration of the acid solution is 0.1-2.5 mol / L.

2. The method according to claim 1, wherein, The waste catalyst is a waste residue oil hydrogenation catalyst, preferably a waste residue oil hydrogenation demetallization catalyst; Preferably, the content of V in the spent catalyst, calculated as V2O5, is 25-50 wt%.

3. The method according to claim 1 or 2, wherein, The method further includes: calcining the waste catalyst and then contacting it with an organic acid solution; Preferably, the calcination conditions include: a temperature of 500-750℃ and a time of 2-6 hours.

4. The method according to any one of claims 1-3, wherein, In step (1), the organic acid is selected from at least one of acetic acid, oxalic acid, citric acid and ethylenediaminetetraacetic acid; Preferably, the concentration of the organic acid solution is 0.5-4 mol / L; Preferably, the ratio of the volume (mL) of the organic acid solution to the mass (g) of the spent catalyst is 10-50:

1.

5. The method according to any one of claims 1-4, wherein, In step (2), the pH of the leachate is adjusted to 0.2-4, preferably 0.5-1.5; Preferably, the method for adjusting the pH of the leachate includes: mixing the leachate with an acid; Preferably, the acid is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid.

6. The method according to any one of claims 1-5, wherein, The molar ratio of the oxidant to the organic acid is (0.3-0.5):1; Preferably, the oxidant is selected from at least one of hydrogen peroxide, ferric sulfate, potassium perchlorate, potassium permanganate, and ozone; Preferably, the reaction temperature is 20-50℃ and the time is 0.1-3h.

7. The method according to any one of claims 1-6, wherein, Step (3) includes: first adjusting the pH of the raw material solution to 1-3, preferably 1.5-2.2, and then contacting it with the extractant for extraction; Preferably, in step (3), the extractant is selected from at least one of P204, P507, TBP, N235 and A336; Preferably, the extractant is provided by an extractant solution, the extractant solution having a mass concentration of 10-30%; Preferably, the solvent in the extractant solution is selected from at least one of hydrogenated kerosene, n-dodecane, and n-octanol; Preferably, the volume flow ratio of the raw material solution to the extractant solution is 1-3:

1.

8. The method according to any one of claims 1-7, wherein, In step (4), the acid in the acid solution is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid; Preferably, the volumetric flow rate ratio of the V-containing extract to the detergent is 0.5-1.5:1; Preferably, the concentration of the acid solution is 0.1-2.5 mol / L; Preferably, the washing process has 3-5 stages.

9. The method according to any one of claims 1-8, wherein, In step (4), the back-extraction includes: mixing the washed feed solution with the back-extraction agent; Preferably, the stripping agent is a sodium carbonate solution, and the concentration of the sodium carbonate solution is preferably 10-20 wt%. Preferably, the number of back-extraction stages is 3-6. Preferably, the volumetric flow rate ratio of the washed feed liquid to the stripping agent is 0.5-3:

1.

10. The application of the method for recovering vanadium from spent catalysts according to any one of claims 1-9 in the treatment of waste oil hydrotreating catalysts.