Method for stepwise recovery of vanadium and chromium from solution by using amide extractant steric effect

Abstract

The application discloses an extraction solvent and an extraction method for stepwise recovery of vanadium and chromium in a solution by steric hindrance effect of an amide extractant, wherein the extraction solvent is composed of extraction solvent A and extraction solvent B; the extraction solvent A is composed of a large steric hindrance amide extractant and diluent A; the extraction solvent B is composed of a small steric hindrance amide extractant and diluent B; the large steric hindrance amide extractant and the small steric hindrance amide extractant are both alkyl-substituted amide extractants; and the diluent A and the diluent B are both inert organic solvents. The steric hindrance effect of the amide extractant in the extraction solvent is utilized to stepwise recover vanadium and chromium in the solution, and high-purity chromium-containing stripping liquid and vanadium-containing stripping liquid are obtained, which has the advantages of high extraction rate, high separation coefficient, high product purity, fast extraction kinetics, good regeneration of the extraction solvent and green harmlessness.

Description

Technical Field

[0001] This invention relates to the field of vanadium-chromium extraction technology. Specifically, it relates to an extraction solvent and extraction method for the stepwise recovery of vanadium-chromium from solution using the steric hindrance effect of amide extractants. Background Technology

[0002] Currently, the main raw materials used for producing vanadium and chromium are vanadium slag and chromite; vanadium and chromium have very similar properties and generally coexist in these minerals. Precipitation is a commonly used industrial method for purifying these minerals, but due to its inherent limitations, it cannot achieve high recovery rates, produces low product purity, and easily generates large amounts of mother liquor wastewater. Therefore, proposing a new recovery and separation method to replace precipitation has considerable potential.

[0003] To address the above issues, patent CN114703363A discloses a method for separating vanadium and chromium in a high-chromium system. Specifically, the method involves: adding a hydrolyzing agent to a high-vanadium, high-chromium solution, maintaining a temperature for aging, and then separating the solid and liquid components to obtain sodium polyvanadate and a chromium-containing solution; adding a purification agent to the obtained chromium-containing solution, maintaining a temperature for aging, and then separating the solid and liquid components again to obtain a pure chromium solution and a purified residue; evaporating and concentrating the obtained pure chromium solution, then cooling and crystallizing, followed by solid-liquid separation to obtain sodium dichromate crystals; adding water to the sodium polyvanadate to make a slurry, then adding sodium hydroxide solution to dissolve it, resulting in a high-vanadium solution; adding sulfuric acid to the obtained high-vanadium solution for pH adjustment, adding a highly efficient vanadium precipitating agent, and then separating the solid and liquid components after heating, stirring, and maintaining a temperature for aging to obtain pure hydrated vanadium pentoxide; and finally drying and calcining the hydrated vanadium pentoxide to obtain a qualified vanadium pentoxide product. This invention avoids the discharge of ammonia nitrogen wastewater, but the process involves many steps and the product structure is simple. Patent CN110642414A discloses a control method for the efficient separation of vanadium and chromium wastewater using modified chelating resin. The method involves adding a reducing agent to the vanadium and chromium wastewater for reduction treatment, controlling the pH of the effluent to 3-5; then oxidizing the wastewater to control the oxidation-reduction potential of the effluent to 400-600 mV; modifying the chelating resin through acid washing and water washing; adsorbing the treated effluent onto the modified chelating resin to separate vanadium and chromium; and finally eluting the adsorbed chelating resin. This invention converts vanadium and chromium to pentavalent and trivalent valences, respectively, and then uses the resin to adsorb vanadium without adsorbing chromium, thus achieving vanadium-chromium separation. However, this invention requires a large amount of reducing and oxidizing agents, and chromium needs to be recovered secondaryly, making the process cumbersome. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to provide an extraction solvent and extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant. The extraction method for extracting vanadium and chromium using this extraction solvent has the advantages of high extraction rate, high separation coefficient, high product purity, fast extraction kinetics, good regenerability of extraction solvent and being green and harmless.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0006] The extraction solvent for the stepwise recovery of vanadium and chromium from solution using amide extractants, comprising extraction solvent A and extraction solvent B, utilizes the steric hindrance effect of amide extractants. Extraction solvent A is a mixture of a highly sterically hindered amide extractant and diluent A; extraction solvent B is a mixture of a less sterically hindered amide extractant and diluent B. Both the highly sterically hindered and less sterically hindered amide extractants are alkyl-substituted amide extractants; diluent A and diluent B are inert organic solvents. In this invention, the highly sterically hindered amide extractant, due to its steric hindrance effect, can only extract and recover chromium from the solution but not vanadium; similarly, the less sterically hindered amide extractant, due to its steric hindrance effect, can only extract and recover vanadium from the solution but not chromium. Therefore, high-purity chromium and vanadium products can be obtained stepwise using these two extractants.

[0007] The extraction solvents used in the stepwise recovery of vanadium and chromium from solution by utilizing the steric hindrance effect of amide extractants are as follows: alkyl-substituted amide extractants are alkyl-substituted monodentate amide extractants, alkyl-substituted bidate amide extractants, or alkyl-substituted tridentate amide extractants; or alkyl-substituted amide extractants are any two or three of the following: alkyl-substituted monodentate amide extractants, alkyl-substituted bidate amide extractants, and alkyl-substituted tridentate amide extractants; alkyl-substituted monodentate amide extractants are a single alkyl-substituted monodentate amide extractant, or a mixture of two or more alkyl-substituted monodentate amide extractants; alkyl-substituted bidate amide extractants are a single alkyl-substituted bidate amide extractant, or a mixture of two or more alkyl-substituted bidate amide extractants; alkyl-substituted tridentate amide extractants are a single alkyl-substituted tridentate amide extractant, or a mixture of two or more alkyl-substituted tridentate amide extractants.

[0008] The above-mentioned extraction solvent for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractants is described above. The structural formula of the alkyl-substituted monodentate amide extractant is as follows:

[0009] (1);

[0010] The structural formula of the alkyl-substituted bidentate amide extractant is:

[0011] (2);

[0012] The structural formula of the alkyl-substituted tridentate amide extractant is:

[0013] (3);

[0014] R1 is an alkyl group with 1 to 30 carbon atoms; R2 is an alkyl group with 1 to 30 carbon atoms; R3 is an alkyl group with 1 to 30 carbon atoms; R4 is an alkyl group with 1 to 30 carbon atoms; R5 is an alkyl group with 1 to 30 carbon atoms; R6 is an alkyl group with 1 to 30 carbon atoms. For sterically hindered amide extractants, at least one alkyl group in the alkyl-substituted amide extractant has more than 8 carbon atoms. For sterically hindered amide extractants, all alkyl groups in the alkyl-substituted amide extractant have less than or equal to 8 carbon atoms.

[0015] The extraction solvent for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of the amide extractant described above is an inert organic solvent that is sulfonated kerosene, halogenated hydrocarbons, or aromatic compounds; or an inert organic solvent that is a mixture of any two or three of sulfonated kerosene, halogenated hydrocarbons, and aromatic compounds.

[0016] Halogenated hydrocarbons are single halogenated hydrocarbons or mixtures of two or more halogenated hydrocarbons; aromatic compounds are single aromatic compounds or mixtures of two or more aromatic compounds.

[0017] The extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant is sulfonated kerosene with 5 to 30 carbon atoms, and halogenated hydrocarbons are chlorinated, bromine, or iodinated hydrocarbons; aromatic compounds are monobenzene aromatics or polycyclic aromatics.

[0018] The extraction solvents for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractants are as follows: Extraction solvent A contains 1-99 parts by weight of sterically hindered amide extractant and 1-99 parts by weight of diluent A, and at least one component of sterically hindered amide extractant and diluent A is liquid at room temperature; Extraction solvent B contains 1-99 parts by weight of sterically hindered amide extractant and 1-99 parts by weight of diluent B, and at least one component of sterically hindered amide extractant and diluent B is liquid at room temperature.

[0019] An extraction method for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractants includes the following steps:

[0020] Step (1) Prepare extraction solvent A and extraction solvent B: Extraction solvent A is composed of a mixture of sterically hindered amide extractant and diluent A; extraction solvent B is composed of a mixture of sterically hindered amide extractant and diluent B; both sterically hindered amide extractants and sterically hindered amide extractants are alkyl-substituted amide extractants; diluent A and diluent B are both inert organic solvents;

[0021] Step (2) Extracting chromium using extraction solvent A: Extraction solvent A is mixed with a vanadium-chromium solution to extract chromium; after extraction, raffinate A and a chromium-supported organic phase are obtained;

[0022] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A to obtain washed organic phase A;

[0023] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A with alkaline solution A to obtain chromium-containing back-extraction solution and chromium-supported organic phase after back-extraction;

[0024] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; after extraction, raffinate B and vanadium-supported organic phase are obtained;

[0025] Step (6) Washing the vanadium-supported organic phase: Wash the vanadium-supported organic phase with acidic solution B to obtain washed organic phase B;

[0026] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B to obtain vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction;

[0027] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Since the back-extraction rate is less than 100% after back-extraction, residual chromium and vanadium in the supported organic phase occupy the coordination space of the extractant. This portion of chromium and vanadium can be removed using alkaline solution to achieve regeneration.

[0028] In the above extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant, in step (2), the pH of the vanadium and chromium-containing solution is adjusted to be less than or equal to 6, the extraction temperature is 5 to 95°C, the volume ratio of extraction solvent A to the vanadium and chromium-containing solution is 0.1 to 20:1, the extraction time is 1 to 80 min, the extraction method is countercurrent extraction, fractional distillation extraction or cross-current extraction, and the number of extraction stages is 1 to 30.

[0029] In step (3), the pH of acidic solution A is less than or equal to 6, the washing temperature is 5 to 95°C, the volume ratio of chromium-supported organic phase to acidic solution A is 0.1 to 20:1, the washing time is 1 to 80 min, the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1 to 15.

[0030] In step (4), the pH of alkaline solution A is greater than 7 and less than or equal to 13.5, and the back-extraction temperature is 5 to 95°C; the volume ratio of organic phase A to alkaline solution A after washing is 0.1 to 20:1; the back-extraction time is 1 to 80 min; the back-extraction method is countercurrent back-extraction, fractional back-extraction or cross-current back-extraction, and the number of back-extraction stages is 1 to 20.

[0031] In step (5), the pH of the raffinate B is adjusted to be less than or equal to 6, the extraction temperature is 5 to 95°C, the volume ratio of the extraction solvent B to the raffinate A is 0.1 to 20:1, the extraction time is 1 to 80 min, the extraction method is countercurrent extraction, fractional distillation extraction or cross-current extraction, and the number of extraction stages is 1 to 30.

[0032] In step (6), the pH of acidic solution B is less than or equal to 6, the washing temperature is 5 to 95°C, the volume ratio of vanadium-supported organic phase to acidic solution B is 0.1 to 20:1, the washing time is 1 to 80 min, the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1 to 15.

[0033] In step (7), the pH of alkaline solution B is greater than 7 and less than or equal to 13.5, and the back-extraction temperature is 5 to 95°C; the volume ratio of organic phase B to alkaline solution B after washing is 0.1 to 20:1; the back-extraction time is 1 to 80 min; the back-extraction method is countercurrent back-extraction, fractional back-extraction or cross-current back-extraction, and the number of back-extraction stages is 1 to 20.

[0034] In step (8), the mass concentration of the solute in alkaline solution C is 10–50 g / L, and the mass concentration of the solute in alkaline solution D is 15–40 g / L; the regeneration temperature of the organic phase after chromium back-extraction is 15–90 °C, and the regeneration temperature of the organic phase after vanadium back-extraction is 15–90 °C; the volume ratio of the organic phase after chromium back-extraction to alkaline solution C is 0.1–20:1, and the volume ratio of the organic phase after vanadium back-extraction to alkaline solution D is 0.1–20:1; the regeneration time is 1–80 min; the regeneration method is countercurrent regeneration, fractional regeneration, or cross-current regeneration, and the number of regeneration stages is 1–15.

[0035] In the above extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant, in step (3), acidic solution A is one or a mixture of two or more of sulfuric acid solution, hydrochloric acid solution, nitric acid solution and chromic acid solution;

[0036] In step (4), alkaline solution A is sodium hydroxide solution, potassium hydroxide solution, ammonia solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, or potassium bicarbonate solution and ammonium carbonate solution; or alkaline solution A is a solution of sodium chloride solution, potassium chloride solution, sodium sulfate solution, potassium sulfate solution, ammonium chloride solution, or ammonium sulfate solution adjusted to a pH greater than 7.

[0037] In step (6), acidic solution B is one or a mixture of two or more of sulfuric acid solution, hydrochloric acid solution, nitric acid solution and chromic acid solution;

[0038] In step (7), alkaline solution B is sodium hydroxide solution, potassium hydroxide solution, ammonia solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, or potassium bicarbonate solution and ammonium carbonate solution; or alkaline solution B is a solution of sodium chloride solution, potassium chloride solution, sodium sulfate solution, potassium sulfate solution, ammonium chloride solution, or ammonium sulfate solution adjusted to a pH greater than 7.

[0039] In step (8), the alkaline solution C is one or a mixture of two or more of the following: sodium chloride solution, ammonium chloride solution, potassium chloride solution, ammonium sulfate solution, potassium sulfate solution, sodium sulfate solution, ammonium carbonate solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution, and is adjusted to a pH greater than 7.

[0040] In step (8), the alkaline solution D is one or a mixture of two or more of the following: sodium chloride solution, ammonium chloride solution, potassium chloride solution, ammonium sulfate solution, potassium sulfate solution, sodium sulfate solution, ammonium carbonate solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution, and is adjusted to a pH greater than 7.

[0041] In the above extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant, in step (2), the vanadium and chromium-containing solution is one or a mixture of two or more of the following: sodium-roasted vanadium slag leachate, vanadium and chromium-containing acid leachate, and vanadium and chromium-containing wastewater.

[0042] The technical solution of the present invention achieves the following beneficial technical effects:

[0043] This invention utilizes the steric hindrance effect of amide extractants to recover vanadium and chromium from solution in a stepwise manner. Extraction solvents A and B are composed of a mixture of amide extractants with different steric hindrances and a diluent. The amide extractants with different steric hindrances are alkyl-substituted amide extractants. In extraction solvent A, the alkyl group has at least one carbon atom greater than 8, while in extraction solvent B, all alkyl groups have less than or equal to 8 carbon atoms. The diluent is an inert organic solvent. Chromium is extracted using extraction solvent A, the chromium-loaded organic phase is washed, and the chromium-loaded organic phase is back-extracted. Vanadium is extracted using extraction solvent B, the vanadium-loaded organic phase is washed, and the vanadium-loaded organic phase is back-extracted. Finally, extraction solvents A and B are regenerated to obtain high-purity chromium-containing and vanadium-containing back-extracting solutions, respectively. This method has advantages such as high extraction rate, high separation coefficient, high product purity, fast extraction kinetics, good solvent regenerability, and is environmentally friendly and harmless. Detailed Implementation

[0044] Example 1

[0045] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 30 wt% sterically hindered amide extractant and 70 wt% diluent A; diluent A is toluene, and the structural formula of the sterically hindered amide extractant is:

[0046] .

[0047] Extraction solvent B is composed of 50 wt% of a sterically hindered amide extractant and 50 wt% of diluent B; diluent B is sulfonated kerosene with 5–30 carbon atoms; the structural formula of the sterically hindered amide extractant is:

[0048] .

[0049] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0050] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0051] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this embodiment, the vanadium-chromium-containing solution is the leaching solution of sodium-roasted vanadium slag] to 2; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 45℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 6:1; the extraction time is 45 min; the extraction method is cross-flow extraction, and the number of extraction stages is 12; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0052] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is sulfuric acid solution with a pH of 4; the washing temperature is 25℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 10:1; the washing time is 25 min; the washing method is fractional washing with 8 washing stages; after washing, the washed organic phase A is obtained.

[0053] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is an ammonia solution with a pH of 11; back-extraction temperature of 45℃; volume ratio of washed organic phase A to alkaline solution A of 10:1; back-extraction time of 15 min; back-extraction method of cross-flow back-extraction, with 8 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0054] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 3, and extract at 45°C; the volume ratio of extraction solvent B to raffinate A is 2:1; the extraction time is 20 min; the extraction method is cross-flow extraction, and the number of extraction stages is 12; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0055] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is hydrochloric acid solution with pH 4, and the washing temperature is 35℃; the volume ratio of vanadium-supported organic phase to acidic solution B is 8:1; the washing time is 15min; the washing method is cross-flow washing, and the number of washing stages is 7.

[0056] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a potassium sulfate solution with a mass concentration of 20 g / L; the pH of alkaline solution B is adjusted to 11 with potassium hydroxide, and the back-extraction temperature is 25℃; the volume ratio of washed organic phase B to alkaline solution B is 9:1; the back-extraction time is 30 min; the back-extraction method is fractional back-extraction, and the number of back-extraction stages is 3.

[0057] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is an ammonia solution with a mass concentration of 10 g / L, and alkaline solution D is an ammonia solution with a mass concentration of 15 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 45℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 45℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 0.5:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 0.5:1; the regeneration time is 20 min; the regeneration method is fractional regeneration, and the number of regeneration stages is 12.

[0058] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 99.52%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.24%; the chromium recovery rate in the vanadium-chromium solution is 95.62%, and the vanadium recovery rate is 96.84%.

[0059] Example 2

[0060] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 25 wt% sterically hindered amide extractant and 75 wt% diluent A; diluent A is hexadecane bromide, and the structural formula of the sterically hindered amide extractant is:

[0061] .

[0062] Extraction solvent B is composed of 30 wt% of a sterically hindered amide extractant and 70 wt% of diluent B; diluent B is dodecyl chloride; the structural formula of the sterically hindered amide extractant is:

[0063] .

[0064] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0065] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0066] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this example, the vanadium-chromium-containing solution is vanadium-chromium-containing wastewater] to 3; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 15℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 8:1; the extraction time is 45 min; the extraction method is fractional extraction, and the number of extraction stages is 15; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0067] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is a chromic acid solution with a pH of 5; the washing temperature is 85℃; the volume ratio of the chromium-supported organic phase to the acidic solution A is 15:1; the washing time is 10 min; the washing method is cross-flow washing with 7 washing stages; after washing, the washed organic phase A is obtained.

[0068] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is sodium hydroxide solution with a pH of 11; back-extraction temperature of 20℃; volume ratio of organic phase A to alkaline solution A of 12:1; back-extraction time of 5 min; back-extraction method of countercurrent back-extraction, with 12 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0069] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 1, and extract at 25°C; the volume ratio of extraction solvent B to raffinate A is 6:1; the extraction time is 30 min; the extraction method is cross-flow extraction, and the number of extraction stages is 16; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0070] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is hydrochloric acid solution with pH 3, and the washing temperature is 25℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 12:1; the washing time is 25min; the washing method is cross-flow washing, and the washing stage is 10 stages.

[0071] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is potassium hydroxide solution with a pH of 12, and the back-extraction temperature is 15℃; the volume ratio of washed organic phase B to alkaline solution B is 8:1; the back-extraction time is 45 min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 12.

[0072] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is a 30 g / L ammonium chloride solution adjusted to pH 8, and alkaline solution D is a 30 g / L ammonium chloride solution adjusted to pH 8. The regeneration temperature of the organic phase supported after chromium back-extraction is 15℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 15℃. The volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 18:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 18:1. The regeneration time is 20 min. The regeneration method is cross-flow regeneration, and the number of regeneration stages is 6.

[0073] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 98.84%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.52%; the chromium recovery rate in the vanadium-chromium solution is 96.32%, and the vanadium recovery rate is 97.02%.

[0074] Example 3

[0075] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 50 wt% sterically hindered amide extractant and 50 wt% diluent A; diluent A is toluene, and the structural formula of the sterically hindered amide extractant is:

[0076] .

[0077] Extraction solvent B is composed of 20 wt% of a sterically hindered amide extractant and 80 wt% of diluent B; diluent B is xylene; the structural formula of the sterically hindered amide extractant is:

[0078] .

[0079] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0080] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0081] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this example, the vanadium-chromium-containing solution is vanadium-chromium-containing wastewater] to 2; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 20℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 14:1; the extraction time is 5 min; the extraction method is fractional extraction, and the number of extraction stages is 8; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0082] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is nitric acid solution with a pH of 1; the washing temperature is 15℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 6:1; the washing time is 40 min; the washing method is cross-flow washing with 10 washing stages; after washing, the washed organic phase A is obtained.

[0083] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is an ammonia solution with a pH of 11.5; back-extraction temperature of 25℃; volume ratio of washed organic phase A to alkaline solution A of 9:1; back-extraction time of 40 min; back-extraction method of cross-flow back-extraction, with 15 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0084] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 2, and extract at 25°C; the volume ratio of extraction solvent B to raffinate A is 9:1; the extraction time is 40 min; the extraction method is countercurrent extraction, and the number of extraction stages is 25; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0085] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a sulfuric acid solution with pH 2, and the washing temperature is 15℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 9:1; the washing time is 45 min; the washing method is cross-flow washing, and the number of washing stages is 9.

[0086] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-supported organic phase after back-extraction; alkaline solution B is an ammonium sulfate solution with a mass concentration of 28 g / L; the pH of alkaline solution B is adjusted to 10 with ammonia water, and the back-extraction temperature is 20℃; the volume ratio of washed organic phase B to alkaline solution B is 10:1; the back-extraction time is 20 min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 18.

[0087] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is a sodium carbonate solution with a mass concentration of 44 g / L, and alkaline solution D is a sodium carbonate solution with a mass concentration of 19 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 25℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 25℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 10:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 10:1; the regeneration time is 40 min; the regeneration method is cross-flow regeneration, and the number of regeneration stages is 10.

[0088] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 98.62%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.54%; the chromium recovery rate in the vanadium-chromium solution is 97.22%, and the vanadium recovery rate is 97.24%.

[0089] Example 4

[0090] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 15 wt% sterically hindered amide extractant and 85 wt% diluent A; diluent A is benzene, and the structural formula of the sterically hindered amide extractant is:

[0091] .

[0092] Extraction solvent B is composed of 45 wt% of a sterically hindered amide extractant and 55 wt% of diluent B; diluent B is iodooctane; the structural formula of the sterically hindered amide extractant is:

[0093] .

[0094] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0095] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0096] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium solution [in this example, the vanadium-chromium solution is a vanadium-chromium acid leaching solution] to 0.5; mix extraction solvent A with the vanadium-chromium solution to extract chromium; the extraction temperature is 30℃; the volume ratio of extraction solvent A to the vanadium-chromium solution is 7:1; the extraction time is 25 min; the extraction method is fractional extraction, and the number of extraction stages is 25; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0097] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is nitric acid solution with a pH of 2.5; the washing temperature is 45℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 10:1; the washing time is 45 min; the washing method is cross-flow washing with 12 washing stages; after washing, the washed organic phase A is obtained.

[0098] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is potassium carbonate solution with a mass concentration of 41 g / L and pH adjusted to 12; back-extraction temperature of 25℃; volume ratio of organic phase A to alkaline solution A of 8:1; back-extraction time of 40 min; back-extraction method of fractional back-extraction, with 15 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0099] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 2.5, and extract at 5°C; the volume ratio of extraction solvent B to raffinate A is 10:1; the extraction time is 20 min; the extraction method is cross-flow extraction, and the number of extraction stages is 15; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0100] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is hydrochloric acid solution with pH 1.5, and the washing temperature is 45℃; the volume ratio of vanadium-supported organic phase to acidic solution B is 14:1; the washing time is 30 min; the washing method is cross-flow washing, and the washing stage is 10 stages.

[0101] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a sodium chloride solution with a mass concentration of 21 g / L; the pH of alkaline solution B is adjusted to 12 with sodium hydroxide, and the back-extraction temperature is 15℃; the volume ratio of washed organic phase B to alkaline solution B is 15:1; the back-extraction time is 40 min; the back-extraction method is fractional back-extraction, and the number of back-extraction stages is 15.

[0102] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is a potassium chloride solution with a mass concentration of 17 g / L adjusted to pH 9 with potassium hydroxide, and alkaline solution D is a potassium chloride solution with a mass concentration of 24 g / L adjusted to pH 10 with potassium hydroxide; the regeneration temperature of the organic phase supported after chromium back-extraction is 25℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 25℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 15:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 15:1; the regeneration time is 40 min; the regeneration method is fractional regeneration, and the number of regeneration stages is 12.

[0103] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 99.28%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.36%; the chromium recovery rate in the vanadium-chromium solution is 96.88%, and the vanadium recovery rate is 98.03%.

[0104] Example 5

[0105] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 20 wt% sterically hindered amide extractant and 80 wt% diluent A; diluent A is chloro-n-octane, and the structural formula of the sterically hindered amide extractant is:

[0106] .

[0107] Extraction solvent B is composed of 45 wt% of a sterically hindered amide extractant and 55 wt% of diluent B; diluent B is sulfonated kerosene with 5–30 carbon atoms; the structural formula of the sterically hindered amide extractant is:

[0108] .

[0109] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0110] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0111] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this embodiment, the vanadium-chromium-containing solution is the leaching solution of sodium-roasted vanadium slag] to 5; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 85℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 10:1; the extraction time is 60 min; the extraction method is fractional extraction, and the number of extraction stages is 15; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0112] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is hydrochloric acid solution with a pH of 5; the washing temperature is 45℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 12:1; the washing time is 60 min; the washing method is cross-flow washing with 6 washing stages; after washing, the washed organic phase A is obtained.

[0113] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is potassium bicarbonate solution with a mass concentration of 20 g / L, and pH adjusted to 12 using potassium hydroxide; back-extraction temperature is 65℃; volume ratio of washed organic phase A to alkaline solution A is 10:1; back-extraction time is 20 min; back-extraction method is cross-flow back-extraction, with 12 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0114] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 1, and extract at 25°C; the volume ratio of extraction solvent B to raffinate A is 8:1; the extraction time is 12 min; the extraction method is cross-flow extraction, and the number of extraction stages is 18; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0115] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a sulfuric acid solution with pH 4, and the washing temperature is 25℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 18:1; the washing time is 40 min; the washing method is fractional washing, and the number of washing stages is 10.

[0116] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a potassium hydroxide solution with pH 11.5; back-extraction temperature is 85℃; the volume ratio of washed organic phase B to alkaline solution B is 14:1; the back-extraction time is 25min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 8.

[0117] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is an ammonia solution with a mass concentration of 22 g / L, and alkaline solution D is an ammonia solution with a mass concentration of 19 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 55℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 55℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 10:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 10:1; the regeneration time is 40 min; the regeneration method is cross-flow regeneration, and the number of regeneration stages is 10.

[0118] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 99.08%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 98.88%; the chromium recovery rate in the vanadium-chromium solution is 98.14%, and the vanadium recovery rate is 97.47%.

[0119] Example 6

[0120] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B. Extraction solvent A is a mixture of 50 wt% sterically hindered amide extractant and 50 wt% diluent A. Diluent A is tetradecane iodotetradecane, CAS number 19218-94-1. The structural formula of the sterically hindered amide extractant is:

[0121] .

[0122] Extraction solvent B is composed of 25 wt% of a sterically hindered amide extractant and 75 wt% of diluent B; diluent B is chloro-n-octane; the structural formula of the sterically hindered amide extractant is:

[0123] .

[0124] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0125] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0126] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium solution [in this example, the vanadium-chromium solution is a vanadium-chromium acid leaching solution] to 0.5; mix extraction solvent A with the vanadium-chromium solution to extract chromium; the extraction temperature is 15℃; the volume ratio of extraction solvent A to the vanadium-chromium solution is 14:1; the extraction time is 10 min; the extraction method is fractional extraction, and the number of extraction stages is 20; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0127] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is hydrochloric acid solution with a pH of 0.5; the washing temperature is 25℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 0.5:1; the washing time is 40 min; the washing method is cross-flow washing with 10 washing stages; after washing, the washed organic phase A is obtained.

[0128] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is sodium hydroxide solution with a pH of 10; back-extraction temperature of 90℃; volume ratio of organic phase A to alkaline solution A of 11:1; back-extraction time of 30 min; back-extraction method of fractional back-extraction, with 8 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0129] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 0.5, and extract at 35°C; the volume ratio of extraction solvent B to raffinate A is 14:1; the extraction time is 50 min; the extraction method is cross-flow extraction, and the number of extraction stages is 11; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0130] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a sulfuric acid solution with pH 2, and the washing temperature is 30℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 10:1; the washing time is 70 min; the washing method is cross-flow washing, and the number of washing stages is 12.

[0131] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a sodium hydroxide solution with pH 12; the back-extraction temperature is 15℃; the volume ratio of washed organic phase B to alkaline solution B is 14:1; the back-extraction time is 55 min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 12.

[0132] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is an ammonia solution with a mass concentration of 23 g / L, and alkaline solution D is an ammonia solution with a mass concentration of 20 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 25℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 25℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 1:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 1:1; the regeneration time is 5 min; the regeneration method is cross-flow regeneration, and the number of regeneration stages is 10.

[0133] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 98.99%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 98.87%; the chromium recovery rate in the vanadium-chromium solution is 97.02%, and the vanadium recovery rate is 98.92%.

[0134] Example 7

[0135] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 30 wt% sterically hindered amide extractant and 70 wt% diluent A; diluent A is sulfonated kerosene, which has 5 to 30 carbon atoms; the structural formula of the sterically hindered amide extractant is:

[0136] .

[0137] Extraction solvent B is composed of 50 wt% of a sterically hindered amide extractant and 50 wt% of diluent B; diluent B is iodododecane; the structural formula of the sterically hindered amide extractant is:

[0138] .

[0139] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0140] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0141] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium solution [in this example, the vanadium-chromium solution is a vanadium-chromium acid leaching solution] to 3; mix extraction solvent A with the vanadium-chromium solution to extract chromium; the extraction temperature is 25℃; the volume ratio of extraction solvent A to the vanadium-chromium solution is 4:1; the extraction time is 40 min; the extraction method is cross-flow extraction, and the number of extraction stages is 3; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0142] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is a chromic acid solution with a pH of 2; the washing temperature is 35℃; the volume ratio of the chromium-supported organic phase to the acidic solution A is 12:1; the washing time is 40 min; the washing method is fractional washing, and the number of washing stages is 11; after washing, the washed organic phase A is obtained.

[0143] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is ammonium sulfate solution with a mass concentration of 45 g / L, adjusted with ammonia water and its pH to 10; back-extraction temperature is 20℃; the volume ratio of washed organic phase A to alkaline solution A is 12:1; back-extraction time is 50 min; back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 12. After back-extraction, a chromium-containing back-extraction solution and a chromium-loaded organic phase are obtained.

[0144] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 0.5, and extract at 55°C; the volume ratio of extraction solvent B to raffinate A is 7:1; the extraction time is 50 min; the extraction method is cross-flow extraction, and the number of extraction stages is 12; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0145] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a nitric acid solution with pH 4, and the washing temperature is 25℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 19:1; the washing time is 45 min; the washing method is countercurrent washing, and the washing stage is 6 stages.

[0146] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a sodium sulfate solution with a mass concentration of 25 g / L; the pH of alkaline solution B is adjusted to 11.5 with sodium hydroxide, and the back-extraction temperature is 45℃; the volume ratio of washed organic phase B to alkaline solution B is 0.5:1; the back-extraction time is 75 min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 17.

[0147] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is an ammonia solution with a mass concentration of 18 g / L, and alkaline solution D is an ammonia solution with a mass concentration of 20 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 35℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 35℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 12:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 12:1; the regeneration time is 40 min; the regeneration method is cross-flow regeneration, and the number of regeneration stages is 11.

[0148] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 98.47%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 98.74%; the chromium recovery rate in the vanadium-chromium solution is 97.12%, and the vanadium recovery rate is 97.24%.

[0149] Example 8

[0150] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 55 wt% sterically hindered amide extractant and 45 wt% diluent A; diluent A is sulfonated kerosene, which has 5-30 carbon atoms; the structural formula of the sterically hindered amide extractant is:

[0151] .

[0152] Extraction solvent B is composed of 20 wt% sterically hindered amide extractant and 80 wt% diluent B; diluent B is chloro-n-octane; the structural formula of the sterically hindered amide extractant is:

[0153] .

[0154] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0155] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0156] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this embodiment, the vanadium-chromium-containing solution is the leaching solution of sodium-roasted vanadium slag] to 2; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 35℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 5:1; the extraction time is 50 min; the extraction method is cross-flow extraction, and the number of extraction stages is 5; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0157] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is hydrochloric acid solution with a pH of 2; the washing temperature is 45℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 8:1; the washing time is 55 min; the washing method is countercurrent washing, and the washing stage is 3 stages; after washing, the washed organic phase A is obtained.

[0158] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is ammonium sulfate solution with a mass concentration of 40 g / L and pH adjusted to 10 with ammonia water; back-extraction temperature of 55℃; volume ratio of organic phase A to alkaline solution A of 7:1; back-extraction time of 55 min; back-extraction method of cross-flow back-extraction, with 12 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0159] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 1.5, and extract at 65°C; the volume ratio of extraction solvent B to raffinate A is 11:1; the extraction time is 40 min; the extraction method is cross-flow extraction, and the number of extraction stages is 8; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0160] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a sulfuric acid solution with pH 0.5, and the washing temperature is 75℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 15:1; the washing time is 55 min; the washing method is cross-flow washing, and the number of washing stages is 11.

[0161] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is an ammonia solution with a pH of 11 and a back-extraction temperature of 35℃; the volume ratio of washed organic phase B to alkaline solution B is 8:1; the back-extraction time is 50 min; the back-extraction method is cross-flow back-extraction, and the number of back-extraction stages is 6.

[0162] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is a sodium hydroxide solution with a mass concentration of 15 g / L, and alkaline solution D is a sodium hydroxide solution with a mass concentration of 23 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 25℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 25℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 10:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 10:1; the regeneration time is 40 min; the regeneration method is fractional regeneration, and the number of regeneration stages is 5.

[0163] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 99.74%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.81%; the chromium recovery rate in the vanadium-chromium solution is 96.88%, and the vanadium recovery rate is 98.33%.

[0164] Example 9

[0165] In this embodiment, the extraction solvent for the stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of the amide extractant consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of 20 wt% sterically hindered amide extractant and 80 wt% diluent A; diluent A is toluene, and the structural formula of the sterically hindered amide extractant is:

[0166] .

[0167] Extraction solvent B is composed of 75 wt% of a sterically hindered amide extractant and 25 wt% of diluent B; diluent B is xylene; the structural formula of the sterically hindered amide extractant is:

[0168] .

[0169] In this embodiment, the extraction method for stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of amide extractant includes the following steps:

[0170] Step (1) Preparation of extraction solvent A and extraction solvent B: Prepare extraction solvent A and extraction solvent B respectively according to the component ratio of the extraction solvents for stepwise recovery of vanadium and chromium from the solution using the steric hindrance effect of amide extractant as described above.

[0171] Step (2) Extracting chromium using extraction solvent A: Adjust the pH of the vanadium-chromium-containing solution [in this example, the vanadium-chromium-containing solution is vanadium-chromium-containing wastewater] to 1; mix extraction solvent A with the vanadium-chromium-containing solution to extract chromium; the extraction temperature is 15℃; the volume ratio of extraction solvent A to the vanadium-chromium-containing solution is 4:1; the extraction time is 10 min; the extraction method is cross-flow extraction, and the number of extraction stages is 22; after extraction, raffinate A and chromium-loaded organic phase are obtained;

[0172] Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A, which is hydrochloric acid solution with a pH of 4; the washing temperature is 25℃; the volume ratio of the chromium-supported organic phase to acidic solution A is 6:1; the washing time is 40 min; the washing method is fractional washing with 7 washing stages; after washing, the washed organic phase A is obtained.

[0173] Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A using alkaline solution A, which is sodium hydroxide solution with a pH of 13.5; back-extraction temperature of 15℃; volume ratio of organic phase A to alkaline solution A of 4:1; back-extraction time of 60 min; back-extraction method of cross-flow back-extraction, with 12 back-extraction stages; after back-extraction, chromium-containing back-extraction solution and chromium-loaded organic phase are obtained.

[0174] Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; adjust raffinate A to pH 2, and extract at 5°C; the volume ratio of extraction solvent B to raffinate A is 0.2:1; the extraction time is 70 min; the extraction method is cross-flow extraction, and the number of extraction stages is 10; after extraction, raffinate B and vanadium-supported organic phase are obtained.

[0175] Step (6) Washing the vanadium-supported organic phase: The vanadium-supported organic phase is washed with acidic solution B to obtain washed organic phase B; acidic solution B is a nitric acid solution with pH 0.2, and the washing temperature is 55℃; the volume ratio of the vanadium-supported organic phase to acidic solution B is 11:1; the washing time is 65min; the washing method is cross-flow washing, and the number of washing stages is 10.

[0176] Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B yields vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; alkaline solution B is a potassium hydroxide solution with a pH of 12.5, and the back-extraction temperature is 35℃; the volume ratio of washed organic phase B to alkaline solution B is 10:1; the back-extraction time is 75 min; the back-extraction method is fractional back-extraction, and the number of back-extraction stages is 8.

[0177] Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling. Alkaline solution C is an ammonia solution with a mass concentration of 30 g / L, and alkaline solution D is an ammonia solution with a mass concentration of 35 g / L; the regeneration temperature of the organic phase supported after chromium back-extraction is 45℃, and the regeneration temperature of the organic phase supported after vanadium back-extraction is 45℃; the volume ratio of the organic phase supported after chromium back-extraction to alkaline solution C is 3:1, and the volume ratio of the organic phase supported after vanadium back-extraction to alkaline solution D is 3:1; the regeneration time is 70 min; the regeneration method is fractional regeneration, and the number of regeneration stages is 12.

[0178] In this embodiment, the purity of the chromium salt obtained by the chromium-containing back-extraction solution in step (4) after concentration and drying is 98.47%, and the purity of the vanadium salt obtained by the vanadium-containing back-extraction solution in step (7) after concentration and drying is 99.57%; the chromium recovery rate in the vanadium-chromium solution is 99.01%, and the vanadium recovery rate is 98.44%.

[0179] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. Solvent for fractional recovery of vanadium and chromium from solutions by means of steric effect of amide extractant, characterized in that, It consists of extraction solvent A and extraction solvent B; extraction solvent A is a mixture of sterically hindered amide extractant and diluent A; extraction solvent B is a mixture of sterically hindered amide extractant and diluent B; both sterically hindered amide extractants and sterically hindered amide extractants are alkyl-substituted amide extractants; diluent A and diluent B are both inert organic solvents; The alkyl-substituted amide extractant is an alkyl-substituted monodentate amide extractant, an alkyl-substituted bidentate amide extractant, or an alkyl-substituted tridentate amide extractant; or the alkyl-substituted amide extractant is any two or a mixture of three of the alkyl-substituted monodentate amide extractant, alkyl-substituted bidentate amide extractant, and alkyl-substituted tridentate amide extractant. The alkyl-substituted monodentate amide extractant is a single alkyl-substituted monodentate amide extractant, or a mixture of two or more alkyl-substituted monodentate amide extractants; the alkyl-substituted bidentate amide extractant is a single alkyl-substituted bidentate amide extractant, or a mixture of two or more alkyl-substituted bidentate amide extractants; the alkyl-substituted tridentate amide extractant is a single alkyl-substituted tridentate amide extractant, or a mixture of two or more alkyl-substituted tridentate amide extractants. The structural formula of the alkyl-substituted monodentate amide extractant is: （1）； The structural formula of the alkyl-substituted bidentate amide extractant is: （2）； The structural formula of the alkyl-substituted tridentate amide extractant is: （3）； R1 is an alkyl group with 1 to 30 carbon atoms; R2 is an alkyl group with 1 to 30 carbon atoms; R3 is an alkyl group with 1 to 30 carbon atoms; R4 is an alkyl group with 1 to 30 carbon atoms; R5 is an alkyl group with 1 to 30 carbon atoms; R6 is an alkyl group with 1 to 30 carbon atoms. For sterically hindered amide extractants, at least one alkyl group in the alkyl-substituted amide extractant has more than 8 carbon atoms. For sterically hindered amide extractants, all alkyl groups in the alkyl-substituted amide extractant have less than or equal to 8 carbon atoms.

2. The extraction solvent for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of the amide extractant according to claim 1, characterized in that, The inert organic solvent is sulfonated kerosene, halogenated hydrocarbons, or aromatic compounds; or the inert organic solvent is any two or three of sulfonated kerosene, halogenated hydrocarbons, and aromatic compounds. Halogenated hydrocarbons are single halogenated hydrocarbons or mixtures of two or more halogenated hydrocarbons; aromatic compounds are single aromatic compounds or mixtures of two or more aromatic compounds.

3. The extraction solvent for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of the amide extractant according to claim 2, characterized in that, Sulfonated kerosene has 5 to 30 carbon atoms, and its halogenated hydrocarbons are chlorinated, bromine, or iodinated hydrocarbons; its aromatic compounds are monobenzene aromatics or polycyclic aromatics.

4. The extraction solvent for the stepwise recovery of vanadium and chromium from solution using the steric hindrance effect of the amide extractant according to claim 1, characterized in that, In extraction solvent A: 1-99 parts by weight of sterically hindered amide extractant and 1-99 parts by weight of diluent A, and at least one component of sterically hindered amide extractant and diluent A is liquid at room temperature; In extraction solvent B: 1-99 parts by weight of sterically hindered amide extractant and 1-99 parts by weight of diluent B, and at least one component of sterically hindered amide extractant and diluent B is liquid at room temperature.

5. The extraction method for stepwise recovery of vanadium and chromium extraction solvent from solution using the steric hindrance effect of amide extractant as described in any one of claims 1-4, characterized in that, Includes the following steps: Step (1) Prepare extraction solvent A and extraction solvent B: Extraction solvent A is composed of a mixture of sterically hindered amide extractant and diluent A; extraction solvent B is composed of a mixture of sterically hindered amide extractant and diluent B; both sterically hindered amide extractants and sterically hindered amide extractants are alkyl-substituted amide extractants; diluent A and diluent B are both inert organic solvents; Step (2) Extracting chromium using extraction solvent A: Extraction solvent A is mixed with a vanadium-chromium solution to extract chromium; after extraction, raffinate A and a chromium-supported organic phase are obtained; Step (3) Washing the chromium-supported organic phase: The chromium-supported organic phase is washed with acidic solution A to obtain washed organic phase A; Step (4) Back-extraction and washing of organic phase A: Back-extraction and washing of organic phase A with alkaline solution A to obtain chromium-containing back-extraction solution and chromium-supported organic phase after back-extraction; Step (5) Extracting vanadium using extraction solvent B: Mix extraction solvent B with raffinate A to extract vanadium; after extraction, raffinate B and vanadium-supported organic phase are obtained; Step (6) Washing the vanadium-supported organic phase: Wash the vanadium-supported organic phase with acidic solution B to obtain washed organic phase B; Step (7) Back-extraction and washing of organic phase B: Back-extraction and washing of organic phase B with alkaline solution B to obtain vanadium-containing back-extraction solution and vanadium-loaded organic phase after back-extraction; Step (8) Regeneration of extraction solvent A and extraction solvent B: The organic phase supported after chromium back-extraction is regenerated using alkaline solution C to obtain regenerated organic phase A, which is then mixed with extraction solvent A for recycling; the organic phase supported after vanadium back-extraction is regenerated using alkaline solution D to obtain regenerated organic phase B, which is then mixed with extraction solvent B for recycling.

6. The extraction method according to claim 5, characterized in that, In step (2), the pH of the vanadium-chromium solution is adjusted to be less than or equal to 6, the extraction temperature is 5 to 95°C, the volume ratio of extraction solvent A to the vanadium-chromium solution is 0.1 to 20:1, the extraction time is 1 to 80 min, the extraction method is countercurrent extraction, fractional extraction or cross-current extraction, and the number of extraction stages is 1 to 30. In step (3), the pH of acidic solution A is less than or equal to 6, the washing temperature is 5 to 95°C, the volume ratio of chromium-supported organic phase to acidic solution A is 0.1 to 20:1, the washing time is 1 to 80 min, the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1 to 15. In step (4), the pH of alkaline solution A is greater than 7 and less than or equal to 13.5, and the back-extraction temperature is 5 to 95°C; the volume ratio of organic phase A to alkaline solution A after washing is 0.1 to 20:1; the back-extraction time is 1 to 80 min; the back-extraction method is countercurrent back-extraction, fractional back-extraction or cross-current back-extraction, and the number of back-extraction stages is 1 to 20. In step (5), the pH of the raffinate A is adjusted to be less than or equal to 6, the extraction temperature is 5 to 95°C, the volume ratio of the extraction solvent B to the raffinate A is 0.1 to 20:1, the extraction time is 1 to 80 min, the extraction method is countercurrent extraction, fractional distillation extraction or cross-current extraction, and the number of extraction stages is 1 to 30. In step (6), the pH of acidic solution B is less than or equal to 6, the washing temperature is 5 to 95°C, the volume ratio of vanadium-supported organic phase to acidic solution B is 0.1 to 20:1, the washing time is 1 to 80 min, the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1 to 15. In step (7), the pH of alkaline solution B is greater than 7 and less than or equal to 13.5, and the back-extraction temperature is 5 to 95°C; the volume ratio of organic phase B to alkaline solution B after washing is 0.1 to 20:1; the back-extraction time is 1 to 80 min; the back-extraction method is countercurrent back-extraction, fractional back-extraction or cross-current back-extraction, and the number of back-extraction stages is 1 to 20. In step (8), the mass concentration of the solute in alkaline solution C is 10–50 g / L, and the mass concentration of the solute in alkaline solution D is 15–40 g / L; the regeneration temperature of the organic phase after chromium back-extraction is 15–90 °C, and the regeneration temperature of the organic phase after vanadium back-extraction is 15–90 °C; the volume ratio of the organic phase after chromium back-extraction to alkaline solution C is 0.1–20:1, and the volume ratio of the organic phase after vanadium back-extraction to alkaline solution D is 0.1–20:1; the regeneration time is 1–80 min; the regeneration method is countercurrent regeneration, fractional regeneration, or cross-current regeneration, and the number of regeneration stages is 1–15.

7. The extraction method according to claim 5, characterized in that, In step (3), acidic solution A is one or a mixture of two or more of sulfuric acid solution, hydrochloric acid solution, nitric acid solution and chromic acid solution; In step (4), alkaline solution A is sodium hydroxide solution, potassium hydroxide solution, ammonia solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, or potassium bicarbonate solution and ammonium carbonate solution; Alternatively, alkaline solution A can be a solution of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, ammonium chloride, or ammonium sulfate, adjusted to a pH greater than 7. In step (6), acidic solution B is one or a mixture of two or more of sulfuric acid solution, hydrochloric acid solution, nitric acid solution and chromic acid solution; In step (7), alkaline solution B is sodium hydroxide solution, potassium hydroxide solution, ammonia solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, or potassium bicarbonate solution and ammonium carbonate solution; Alternatively, alkaline solution B can be a solution of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, ammonium chloride, or ammonium sulfate, adjusted to a pH greater than 7. In step (8), the alkaline solution C is one or more of the following: sodium chloride solution, ammonium chloride solution, potassium chloride solution, ammonium sulfate solution, potassium sulfate solution, sodium sulfate solution, ammonium carbonate solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution, and is adjusted to a solution with a pH greater than 7. In step (8), the alkaline solution D is one or more of the following: sodium chloride solution, ammonium chloride solution, potassium chloride solution, ammonium sulfate solution, potassium sulfate solution, sodium sulfate solution, ammonium carbonate solution, sodium carbonate solution, potassium carbonate solution, ammonium bicarbonate solution, sodium bicarbonate solution, and potassium bicarbonate solution, and is adjusted to a pH greater than 7.

8. The extraction method according to claim 5, characterized in that, In step (2), the vanadium-chromium-containing solution is one or a mixture of two or more of the following: sodium-roasted vanadium slag leachate, vanadium-chromium-containing acid leachate, and vanadium-chromium-containing wastewater.

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