Extraction solvent and extraction method for recovering hexavalent chromium in solution by using quaternary ammonium salt ionic liquid

Abstract

The invention discloses an extraction solvent and an extraction method for extracting and recovering hexavalent chromium in a solution by using a quaternary ammonium salt ionic liquid. The extraction solvent is composed of an ionic liquid and a diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent; the extraction method comprises the following steps: preparing the extraction solvent as an extraction organic phase; extracting the hexavalent chromium in a hexavalent chromium-containing solution by using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; washing the loaded organic phase by using a salt solution A, and obtaining a washed organic phase after the washing is completed; stripping the washed organic phase by using a salt solution B; obtaining a stripped chromium solution and a stripped organic phase after the stripping is completed; regenerating the stripped organic phase by using a salt solution C, and obtaining a regenerated organic phase, which is used as an extracted organic phase for recycling. The invention can solve the problems of low recovery rate of hexavalent chromium products and poor product purity.

Description

Technical Field

[0001] The invention relates to the technical field of hexavalent chromium extraction, and specifically to an extraction solvent and an extraction method for extracting and recovering hexavalent chromium in a solution by using quaternary ammonium salt ionic liquid. Background Art

[0002] Chromium salt products are closely related to human life and are widely used in all walks of life. They are an important support for the national economy. However, the current precipitation method is commonly used to produce chromium salts, which not only has low product purity but also low recovery rate. At the same time, a large amount of wastewater containing hexavalent chromium is also produced in other industrial production, which poses a great threat to the environment and human body. Therefore, efficient recovery of chromium from chromium-containing solutions is both environmentally friendly and avoids resource waste.

[0003] In response to the above problems, the patent with publication number CN113023858A discloses a simple and efficient method for treating chromium-containing waste liquid, which comprises adjusting the pH value of the chromium-containing waste liquid and adding oxalate to the chromium-containing waste liquid to obtain a first mixed liquid; reacting the first mixed liquid at 210°C to 250°C for 8h to 12h to obtain a solid-liquid mixture, centrifuging the mixture, and then drying the obtained chromium-containing precipitate to obtain a chromium-containing material; this method can efficiently and quickly treat hexavalent chromium in the solution and reduce toxicity, but the process does not achieve efficient recovery of chromium resources, and the purity of the obtained chromium-containing material is not high. The patent with publication number CN104787952A discloses a process for recovering chromium from wastewater containing hexavalent chromium. The process uses an extractant to extract the hexavalent chromium in the wastewater into an organic phase and then separates it from the aqueous phase to obtain an organic phase loaded with hexavalent chromium; then the loaded organic phase is reduced with an aqueous solution of an organic reducing agent to reduce the hexavalent chromium to trivalent chromium, which is then stripped into the aqueous phase. After the two phases are separated, a solution containing trivalent chromium and a regenerated organic phase are obtained. Then, the solution containing trivalent chromium is subjected to solvent evaporation and crystallization to recover the trivalent chromium. The final oxidation products of this process are carbon dioxide and water, which is relatively green and environmentally friendly, but the cost is high and it is not suitable for processes aimed at obtaining hexavalent chromium products. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to provide an extraction solvent and an extraction method for extracting and recovering hexavalent chromium in a solution using a quaternary ammonium salt ionic liquid, which has the advantages of high product purity, renewable extraction solvent, easy mechanization and green environmental protection, so as to solve the problems of low recovery rate of hexavalent chromium products and poor product purity.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The extraction solvent for recovering hexavalent chromium from a solution by using quaternary ammonium salt ionic liquid is composed of an ionic liquid and a diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. The ionic liquid has a strong anion exchange capacity and can exchange with the chromium ions in the solution, thereby achieving the purpose of extracting hexavalent chromium. The diluent can dilute the ionic liquid, adjust the viscosity of the ionic liquid, and reduce the water solubility of the ionic liquid, so that the extraction effect of the hexavalent chromium reaches an ideal state. In addition, the ionic liquid has a low vapor pressure, is not volatile, is not flammable, and is safe and environmentally friendly to use.

[0007] The above-mentioned extraction solvent using quaternary ammonium salt ionic liquid to extract and recover hexavalent chromium in the solution, the quaternary ammonium salt ionic liquid is a quaternary ammonium type quaternary ammonium salt ionic liquid, an imidazole type quaternary ammonium salt ionic liquid or a pyridine type quaternary ammonium salt ionic liquid; or the quaternary ammonium salt ionic liquid is a mixture of any two or three of a quaternary ammonium type quaternary ammonium salt ionic liquid, an imidazole type quaternary ammonium salt ionic liquid and a pyridine type quaternary ammonium salt ionic liquid;

[0008] The quaternary ammonium salt ionic liquid is a single quaternary ammonium salt ionic liquid, or a mixture of two or more quaternary ammonium salt ionic liquids; the imidazole salt ionic liquid is a single imidazole salt ionic liquid, or a mixture of two or more imidazole salt ionic liquids; the pyridine salt ionic liquid is a single pyridine salt ionic liquid, or a mixture of two or more pyridine salt ionic liquids.

[0009] The above-mentioned extraction solvent using quaternary ammonium salt ionic liquid to extract and recover hexavalent chromium in the solution, the structural formula of the quaternary ammonium type quaternary ammonium salt ionic liquid is:

[0010]

[0011] In the structural formula (1), the cation is a quaternary ammonium ion; the anion is an inorganic acid anion;

[0012] The structural formula of imidazole quaternary ammonium salt ionic liquid is:

[0013]

[0014] In the structural formula (2), the cation is an imidazolium ion or an imidazolium ion derivative; the anion is an inorganic acid anion;

[0015] The structural formula of pyridine quaternary ammonium salt ionic liquid is:

[0016]

[0017] In the structural formula (3), the cation is a pyridinium ion or a pyridinium ion derivative; and the anion is an inorganic acid anion.

[0018] The above-mentioned extraction solvent for extracting and recovering hexavalent chromium in the solution using quaternary ammonium salt ionic liquid, R1 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20, R2 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20, R3 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20, R4 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20, R5 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20, and R6 is a hydrogen ion or an alkyl group with a carbon number of 1 to 20; if R1 to R6 are alkyl groups with a carbon number greater than 20, the solubility of the ionic liquid in the diluent will decrease, and solids will easily precipitate, which is not conducive to the extraction of hexavalent chromium in the solution; the inorganic acid anion is a sulfate anion, a hydrochloride anion, a nitrate anion, a carbonate anion, a hydroiodate anion or a hydrobromide anion.

[0019] The extraction solvent for recovering hexavalent chromium from the solution by extracting quaternary ammonium salt ionic liquid is an inert organic solvent of sulfonated kerosene, halogenated hydrocarbon compounds or aromatic compounds; or the inert organic solvent is a mixture of any two or three of sulfonated kerosene, halogenated hydrocarbon compounds and aromatic compounds; wherein the halogenated hydrocarbon compound is used as a diluent for the ionic liquid, and the extraction solvent composed thereof has a better extraction effect.

[0020] The halogenated hydrocarbon compound is a single halogenated hydrocarbon compound, or a mixture of two or more halogenated hydrocarbon compounds; the aromatic compound is a single aromatic compound, or a mixture of two or more aromatic compounds.

[0021] The extraction solvent for recovering hexavalent chromium from the solution using quaternary ammonium salt ionic liquid is sulfonated kerosene with carbon atoms of 8 to 25, the halogenated hydrocarbon compound is chlorinated hydrocarbon, brominated hydrocarbon or iodinated hydrocarbon, and the aromatic compound is monophenyl aromatic hydrocarbon or polycyclic aromatic hydrocarbon.

[0022] In the above extraction solvent using quaternary ammonium salt ionic liquid to extract and recover hexavalent chromium in the solution, the ionic liquid and / or diluent is liquid at room temperature; the mass fraction of the ionic liquid is 2-98wt%.

[0023] The invention discloses a method for extracting and recovering hexavalent chromium in a solution by using quaternary ammonium salt ionic liquid, comprising the following steps:

[0024] Step (1) Preparation of the extracted organic phase: preparing the extraction solvent for extracting and recovering hexavalent chromium in the solution using the quaternary ammonium salt ionic liquid as the extracted organic phase;

[0025] Step (2) extraction: extracting the hexavalent chromium in the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed;

[0026] Step (3) washing: washing the loaded organic phase with salt solution A, and obtaining a washed organic phase after washing. The purpose of washing is to remove impurity ions entrained in the loaded organic phase, so as to obtain a chromium product with higher purity.

[0027] Step (4) back extraction: back extracting the washed organic phase with salt solution B; after the back extraction is completed, a back extraction chromium solution and a back extraction organic phase are obtained; the purpose of the back extraction is to transfer the chromium in the washed organic phase to the aqueous phase, and the mechanism of the back extraction is that the anions of the corresponding salt are exchanged with the chromium in the washed organic phase, thereby transferring the chromium to the back extraction solution.

[0028] Step (5) Regeneration: The stripping organic phase is regenerated using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase. The purpose of regeneration is to further remove the chromium and other impurities that have not been stripped clean in the stripping organic phase, and to recycle the obtained regenerated organic phase. The mechanism of regeneration is also based on anion exchange.

[0029] The above-mentioned extraction method for recovering hexavalent chromium in a solution by extracting quaternary ammonium salt ionic liquid, in step (2), the pH of the hexavalent chromium solution is 4-13, the extraction temperature is 5-95°C; the volume ratio of the extracted organic phase to the hexavalent chromium solution is 0.1-10.0:1; the extraction time is 0.5-60min; the extraction method is countercurrent extraction, fractional extraction or cross-current extraction, and the extraction stage is 1-30;

[0030] In step (3), the mass concentration of salt in salt solution A is 1-50 g / L; the pH of salt solution A is adjusted to 7-13 using the hydroxide corresponding to the salt in salt solution A [when the pH is in this range, the washing effect is better], and the washing temperature is 5-95° C.; the volume ratio of the loaded organic phase to the salt solution A is 0.1-10.0:1; the washing time is 0.5-60 min; the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1-10;

[0031] In step (4), the mass concentration of salt in salt solution B is 1 to 100 g / L; the pH of salt solution B is adjusted to 7 to 13 using the hydroxide corresponding to the salt in salt solution B [when the pH is in this range, the stripping effect is better], and the stripping temperature is 5 to 95° C.; the volume ratio of the washing organic phase to the salt solution B is 0.1 to 10.0:1; the stripping time is 0.5 to 60 min; the stripping method is countercurrent stripping, fractional stripping or cross-current stripping, and the stripping stage is 1 to 20;

[0032] In step (5), the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extracted organic phase, and the mass concentration of the salt solution C is 5 to 25 g / L; the regeneration temperature is 5 to 95° C.; the volume ratio of the stripping organic phase to the salt solution C is 0.1 to 10.0:1; the regeneration time is 0.5 to 60 min; the regeneration method is countercurrent regeneration, fractional distillation regeneration or cross-current regeneration, and the regeneration level is 1 to 10.

[0033] In the above-mentioned extraction method for recovering hexavalent chromium in a solution by extracting quaternary ammonium salt ionic liquid, the salt solution A is one or two of sodium carbonate solution, ammonium carbonate solution, potassium carbonate solution, sodium chloride solution, potassium chloride solution, ammonium chloride solution, sodium bromide solution, potassium bromide solution, ammonium bromide solution, sodium iodide solution, potassium iodide solution, ammonium iodide solution, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, sodium sulfate solution, potassium sulfate solution or ammonium sulfate solution, or a mixture of two or more thereof;

[0034] Salt solution B is one or a mixture of two or more of 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, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, ammonium bromide solution, sodium bromide solution, potassium bromide solution, sodium iodide solution, potassium iodide solution or ammonium iodide solution;

[0035] The salt solution C is one or a mixture of two or more of 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, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, ammonium bromide solution, sodium bromide solution, potassium bromide solution, sodium iodide solution, potassium iodide solution or ammonium iodide solution.

[0036] The above-mentioned method for extracting hexavalent chromium in the solution using quaternary ammonium salt ionic liquid for recovery includes the hexavalent chromium solution including sodium roasted chromite leaching solution, vanadium precipitation mother liquor, electroplating wastewater and leather chromium-containing wastewater.

[0037] The technical solution of the present invention achieves the following beneficial technical effects:

[0038] The extraction solvent of the invention is composed of a mixture of an ionic liquid and a diluent, wherein the ionic liquid is a quaternary ammonium salt ionic liquid, the diluent is an inert organic solvent, the ionic liquid is one or more of quaternary ammonium salt ionic liquids such as quaternary ammonium type ionic liquids, imidazole type ionic liquids and pyridine type ionic liquids, and the diluent is one or more of inert organic solvents such as sulfonated kerosene, halogenated hydrocarbon compounds and aromatic compounds. A high-purity chromium-containing solution is obtained through the process steps of preparing an extraction solvent, extraction, washing, stripping and regeneration. The invention has the advantages of high product purity, regenerable extraction solvent, easy mechanization and green environmental protection. DETAILED DESCRIPTION

[0039] Example 1

[0040] In this embodiment, the extraction solvent for extracting and recovering hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid is composed of 15wt% ionic liquid and 85wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a quaternary ammonium type quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0041]

[0042] The diluent is an inert organic solvent sulfonated kerosene, and the carbon number of the sulfonated kerosene is 8-25.

[0043] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0044] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0045] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is chromium-containing wastewater from leather, and its pH is 6; the extraction temperature is 45° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 5:1; the extraction time is 20 min; the extraction method is countercurrent extraction, and the extraction stage is 6;

[0046] Step (3) washing: washing the loaded organic phase with a salt solution A and a sodium carbonate solution, and obtaining a washed organic phase after washing; the mass concentration of the sodium carbonate solution is 15 g / L, the pH of the sodium carbonate solution is adjusted to 8, and the washing temperature is 40° C.; the volume ratio of the loaded organic phase to the salt solution A is 8:1; the washing time is 5 min; the washing method is countercurrent washing, and the washing stage number is 7;

[0047] Step (4) stripping: stripping the washed organic phase with a salt solution B and a sodium chloride solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium chloride solution is 40 g / L, the pH of the sodium chloride solution is adjusted to 10 with sodium hydroxide, and the stripping temperature is 65° C.; the volume ratio of the washed organic phase to the salt solution B is 0.5:1; the stripping time is 10 min; the stripping method is fractional stripping, and the stripping stage is 8;

[0048] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is an ammonium chloride solution, and the mass concentration of the ammonium chloride solution is 15g / L; the regeneration temperature is 85°C; the volume ratio of the stripping organic phase to the salt solution C is 6:1; the regeneration time is 30min; the regeneration mode is countercurrent regeneration, and the regeneration level is 2.

[0049] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 99.42%, and the total recovery rate of chromium is 98.24%.

[0050] Example 2

[0051] In this embodiment, the extraction solvent for extracting and recovering hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid is composed of 50wt% ionic liquid and 50wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is an imidazole quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0052]

[0053] The diluent is an inert organic solvent, dodecane bromide.

[0054] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0055] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0056] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using an extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a vanadium precipitation mother liquor, and its pH is 5; the extraction temperature is 65° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 4:1; the extraction time is 20 min; the extraction method is countercurrent extraction, and the extraction stage is 10;

[0057] Step (3) washing: washing the loaded organic phase with a salt solution A and an ammonium bromide solution, and obtaining a washed organic phase after washing; the mass concentration of ammonium bromide in the ammonium bromide solution is 15 g / L, the pH of the ammonium bromide solution is adjusted to 10 with ammonia water, and the washing temperature is 35° C.; the volume ratio of the loaded organic phase to the salt solution A is 8:1; the washing time is 40 min; the washing method is cross-current washing, and the washing stage number is 5;

[0058] Step (4) stripping: stripping the washed organic phase with a salt solution B and an ammonium bromide solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of ammonium bromide in the ammonium bromide solution is 60 g / L, the pH value of the ammonium bromide solution is adjusted to 7 with ammonia water, and the stripping temperature is 10° C.; the volume ratio of the washed organic phase to the salt solution B is 6:1; the stripping time is 15 min; the stripping method is cross-current stripping, and the stripping stage is 8;

[0059] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a sodium bromide solution, and the mass concentration of the sodium bromide solution is 10g / L; the regeneration temperature is 25°C; the volume ratio of the stripping organic phase to the salt solution C is 4:1; the regeneration time is 15min; the regeneration method is fractional regeneration, and the regeneration level is 3.

[0060] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 99.02%, and the total recovery rate of chromium is 98.61%.

[0061] Example 3

[0062] In this embodiment, the extraction solvent for extracting and recovering hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid is composed of 20wt% ionic liquid and 80wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a pyridine quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0063]

[0064] The diluent is an inert organic solvent octadecane chloride.

[0065] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0066] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0067] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a sodium roasted chromite leaching solution, and its pH is 10; the extraction temperature is 20° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 6:1; the extraction time is 30 min; the extraction method is fractional extraction, and the extraction stage is 15;

[0068] Step (3) washing: washing the loaded organic phase with salt solution A and potassium chloride solution, and obtaining a washed organic phase after washing; the mass concentration of the potassium chloride solution is 20 g / L, the pH of the potassium chloride solution is adjusted to 10 with potassium hydroxide, and the washing temperature is 25° C.; the volume ratio of the loaded organic phase to the salt solution A is 9:1; the washing time is 15 min; the washing method is fractional distillation washing, and the washing stage number is 8;

[0069] Step (4) stripping: stripping the washed organic phase with salt solution B and potassium chloride solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the potassium chloride solution is 35 g / L, the pH of the potassium chloride solution is adjusted to 12 with potassium hydroxide, and the stripping temperature is 5° C.; the volume ratio of the washed organic phase to the salt solution B is 1:1; the stripping time is 3 min; the stripping method is cross-current stripping, and the stripping stage is 5;

[0070] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a sodium chloride solution with a mass concentration of 8 g / L; the regeneration temperature is 15° C.; the volume ratio of the stripping organic phase to the salt solution C is 10:1; the regeneration time is 10 min; the regeneration method is fractional regeneration, and the regeneration stage is 8 stages.

[0071] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after the stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 97.83%, and a chromium recovery rate of 98.92%.

[0072] Example 4

[0073] In this embodiment, the extraction solvent for extracting and recovering hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid is composed of 25wt% ionic liquid and 75wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a quaternary ammonium type quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0074]

[0075] The diluent is an inert organic solvent, octane chloride.

[0076] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0077] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0078] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a sodium roasted chromite leaching solution, and its pH is 8; the extraction temperature is 45° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 2:1; the extraction time is 12 min; the extraction method is fractional extraction, and the extraction stage is 11;

[0079] Step (3) washing: washing the loaded organic phase with a salt solution A and an ammonium sulfate solution, and obtaining a washed organic phase after washing; the mass concentration of the ammonium sulfate solution is 18 g / L, the pH of the ammonium sulfate solution is adjusted to 10 with ammonia water, and the washing temperature is 25° C.; the volume ratio of the loaded organic phase to the salt solution A is 1:1; the washing time is 2 min; the washing method is fractional distillation washing, and the washing stage number is 3;

[0080] Step (4) stripping: stripping the washed organic phase with a sodium sulfate solution of a salt solution B; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium sulfate solution is 42 g / L, the pH of the sodium sulfate solution is adjusted to 10 with sodium hydroxide, and the stripping temperature is 40° C.; the volume ratio of the washed organic phase to the salt solution B is 8:1; the stripping time is 30 min; the stripping method is countercurrent stripping, and the stripping stage is 6;

[0081] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a sodium sulfate solution, and the mass concentration of the sodium sulfate solution is 12 g / L; the regeneration temperature is 20° C.; the volume ratio of the stripping organic phase to the salt solution C is 3:1; the regeneration time is 8 min; the regeneration method is fractional distillation regeneration, and the regeneration level is 5.

[0082] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after the stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 98.22%, and a chromium recovery rate of 98.54%.

[0083] Example 5

[0084] In this embodiment, the extraction solvent for recovering hexavalent chromium in the solution by extracting quaternary ammonium salt ionic liquid is composed of 60wt% ionic liquid and 40wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is an imidazole quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0085]

[0086] The diluent is an inert organic solvent iodooctane.

[0087] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0088] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0089] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using an extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is electroplating wastewater, and its pH is 5; the extraction temperature is 25° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 7:1; the extraction time is 30 min; the extraction method is countercurrent extraction, and the extraction stage is 8;

[0090] Step (3) washing: washing the loaded organic phase with a sodium bromide solution of salt solution A, and obtaining a washed organic phase after washing; the mass concentration of the sodium bromide solution is 20 g / L, the pH of the sodium bromide solution is adjusted to 12 with sodium hydroxide, and the washing temperature is 45° C.; the volume ratio of the loaded organic phase to the salt solution A is 6:1; the washing time is 8 min; the washing method is fractional washing, and the washing stage number is 6;

[0091] Step (4) stripping: stripping the washed organic phase with a sodium bromide solution of salt solution B; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium bromide solution is 48 g / L, the pH of the sodium bromide solution is adjusted to 10 with sodium hydroxide, and the stripping temperature is 45° C.; the volume ratio of the washed organic phase to the salt solution B is 9:1; the stripping time is 55 min; the stripping method is countercurrent stripping, and the stripping stage is 14;

[0092] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is an ammonium iodide solution, and the mass concentration of the ammonium iodide solution is 6 g / L; the regeneration temperature is 85° C.; the volume ratio of the stripping organic phase to the salt solution C is 9:1; the regeneration time is 15 min; the regeneration mode is countercurrent regeneration, and the regeneration level is 9.

[0093] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after the stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 99.08%, and the total recovery rate of chromium is 98.42%.

[0094] Example 6

[0095] In this embodiment, the extraction solvent for recovering hexavalent chromium in the solution by extracting quaternary ammonium salt ionic liquid is composed of 70wt% ionic liquid and 30wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a pyridine quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0096]

[0097] The diluent is an inert organic solvent sulfonated kerosene, and the carbon number of the sulfonated kerosene is 8-25.

[0098] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0099] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0100] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using an extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a sodium roasted chromite leaching solution, and its pH is 8; the extraction temperature is 25° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 8:1; the extraction time is 10 min; the extraction method is cross-current extraction, and the extraction stage is 25;

[0101] Step (3) washing: washing the loaded organic phase with a salt solution A and a sodium carbonate solution, and obtaining a washed organic phase after washing; the mass concentration of the sodium carbonate solution is 5 g / L, the pH of the sodium carbonate solution is adjusted to 10, and the washing temperature is 55° C.; the volume ratio of the loaded organic phase to the salt solution A is 8:1; the washing time is 55 min; the washing method is countercurrent washing, and the washing stage is 8;

[0102] Step (4) stripping: stripping the washed organic phase with a salt solution B and a sodium carbonate solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium carbonate solution is 15 g / L; the pH of the sodium carbonate solution is adjusted to 10 with sodium hydroxide, and the stripping temperature is 45° C.; the volume ratio of the washed organic phase to the salt solution B is 2:1; the stripping time is 30 min; the stripping method is countercurrent stripping, and the stripping stage is 15 stages;

[0103] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a potassium carbonate solution, and the mass concentration of the potassium carbonate solution is 14 g / L; the regeneration temperature is 25° C.; the volume ratio of the stripping organic phase to the salt solution C is 8:1; the regeneration time is 60 min; the regeneration method is fractional regeneration, and the regeneration stage is 8 stages.

[0104] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after the stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 98.46%, and the total recovery rate of chromium is 98.89%.

[0105] Example 7

[0106] In this embodiment, the extraction solvent for extracting and recovering hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid is composed of 10wt% ionic liquid and 90wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a quaternary ammonium type quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0107]

[0108] The diluent is the inert organic solvent p-xylene.

[0109] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0110] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0111] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using an extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is electroplating wastewater, and its pH is 4; the extraction temperature is 15° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 8:1; the extraction time is 45 min; the extraction method is cross-current extraction, and the extraction stage is 3;

[0112] Step (3) washing: washing the loaded organic phase with a salt solution A and a sodium carbonate solution, and obtaining a washed organic phase after washing; the mass concentration of the sodium carbonate solution is 30 g / L, the pH of the sodium carbonate solution is adjusted to 11, and the washing temperature is 85° C.; the volume ratio of the loaded organic phase to the salt solution A is 3:1; the washing time is 50 min; the washing method is cross-current washing, and the washing stage is 3;

[0113] Step (4) stripping: stripping the washed organic phase with a salt solution B and an ammonium carbonate solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the ammonium carbonate solution is 68 g / L; the pH of the ammonium carbonate solution is 10, and the stripping temperature is 15° C.; the volume ratio of the washed organic phase to the salt solution B is 0.5:1; the stripping time is 20 min; the stripping method is cross-current stripping, and the stripping stage is 5;

[0114] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a potassium carbonate solution, and the mass concentration of the potassium carbonate solution is 14g / L; the regeneration temperature is 20°C; the volume ratio of the stripping organic phase to the salt solution C is 3:1; the regeneration time is 55min; the regeneration method is fractional distillation regeneration, and the regeneration level is 2.

[0115] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 98.44%, and the total recovery rate of chromium is 99.01%.

[0116] Example 8

[0117] In this embodiment, the extraction solvent for recovering hexavalent chromium in the solution by extracting quaternary ammonium salt ionic liquid is composed of 75wt% ionic liquid and 25wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is an imidazole quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0118]

[0119] The diluent is the inert organic solvent toluene.

[0120] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0121] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0122] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a sodium roasted chromite leaching solution, and its pH is 9; the extraction temperature is 40° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 8:1; the extraction time is 45 min; the extraction method is cross-current extraction, and the extraction stage is 12;

[0123] Step (3) washing: washing the loaded organic phase with a sodium nitrate solution of salt solution A, and obtaining a washed organic phase after washing; the mass concentration of the sodium nitrate solution is 10 g / L, the pH of the sodium nitrate solution is adjusted to 7.5 with sodium hydroxide, and the washing temperature is 35° C.; the volume ratio of the loaded organic phase to the salt solution A is 7:1; the washing time is 20 min; the washing method is cross-current washing, and the number of washing stages is 8;

[0124] Step (4) stripping: stripping the washed organic phase with a salt solution B sodium nitrate solution; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium nitrate solution is 52 g / L; the pH of the sodium nitrate solution is adjusted to 13 with sodium hydroxide, and the stripping temperature is 45° C.; the volume ratio of the washed organic phase to the salt solution B is 6:1; the stripping time is 45 min; the stripping method is fractional stripping, and the stripping stage is 18;

[0125] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a sodium nitrate solution, and the mass concentration of the sodium nitrate solution is 25 g / L; the regeneration temperature is 15° C.; the volume ratio of the stripping organic phase to the salt solution C is 7:1; the regeneration time is 45 min; the regeneration mode is cross-flow regeneration, and the regeneration stage is 7 stages.

[0126] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 97.96%, and the total recovery rate of chromium is 98.43%.

[0127] Example 9

[0128] In this embodiment, the extraction solvent for recovering hexavalent chromium in the solution by extracting quaternary ammonium salt ionic liquid is composed of 10wt% ionic liquid and 90wt% diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent. In this embodiment, the quaternary ammonium salt ionic liquid is a pyridine quaternary ammonium salt ionic liquid, and its structural formula is as follows:

[0129]

[0130] The diluent is an inert organic solvent hexyl bromide.

[0131] In this embodiment, the method for extracting hexavalent chromium in the solution by using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium comprises the following steps:

[0132] Step (1) Preparation of the extracted organic phase: The extraction solvent for recovering hexavalent chromium in the solution by using the quaternary ammonium salt ionic liquid is used as the extracted organic phase of this embodiment;

[0133] Step (2) extraction: extracting hexavalent chromium from the hexavalent chromium-containing solution using an extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; in this embodiment, the hexavalent chromium-containing solution is a sodium roasted chromite leaching solution, and its pH is 13; the extraction temperature is 25° C., and the volume ratio of the extraction organic phase to the hexavalent chromium-containing solution is 9:1; the extraction time is 50 min; the extraction method is cross-current extraction, and the extraction stage is 20;

[0134] Step (3) washing: washing the loaded organic phase with salt solution A and potassium sulfate solution, and obtaining a washed organic phase after washing; the mass concentration of the potassium sulfate solution is 8 g / L, the pH of the potassium sulfate solution is adjusted to 8 with potassium hydroxide, and the washing temperature is 95° C.; the volume ratio of the loaded organic phase to the salt solution A is 10:1; the washing time is 20 min; the washing method is cross-current washing, and the washing stage is 2;

[0135] Step (4) stripping: stripping the washed organic phase with a sodium sulfate solution of a salt solution B; after stripping, a high-purity chromium-containing stripping chromium solution and a stripping organic phase are obtained; the mass concentration of the sodium sulfate solution is 26 g / L, and the pH of the sodium sulfate solution is adjusted to 9 with potassium hydroxide; the stripping temperature is 35° C.; the volume ratio of the washed organic phase to the salt solution B is 7:1; the stripping time is 1 min; the stripping method is cross-current stripping, and the stripping stage is 19;

[0136] Step (5) regeneration: the stripping organic phase is regenerated by using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase; the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extraction organic phase, and in this embodiment is a sodium sulfate solution, and the mass concentration of the sodium sulfate solution is 16 g / L; the regeneration temperature is 55° C.; the volume ratio of the stripping organic phase to the salt solution C is 9:1; the regeneration time is 55 min; the regeneration method is fractional distillation regeneration, and the regeneration level is 2.

[0137] In this embodiment, the high-purity chromium-containing stripping chromium solution obtained after the stripping in step (4) is concentrated and dried to obtain a chromium salt with a purity of 99.22%, and a chromium recovery rate of 98.34%.

[0138] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the claims of this patent application.

Claims

1. Using quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium in the solution as an extraction solvent, characterized in that: It is composed of an ionic liquid and a diluent; the ionic liquid is a quaternary ammonium salt ionic liquid, and the diluent is an inert organic solvent; The quaternary ammonium salt ionic liquid is a quaternary ammonium type quaternary ammonium salt ionic liquid, an imidazole type quaternary ammonium salt ionic liquid or a pyridinium type quaternary ammonium salt ionic liquid; or the quaternary ammonium salt ionic liquid is a mixture of any two or three of a quaternary ammonium type quaternary ammonium salt ionic liquid, an imidazole type quaternary ammonium salt ionic liquid and a pyridinium type quaternary ammonium salt ionic liquid; The quaternary ammonium salt ionic liquid is a single quaternary ammonium salt ionic liquid, or a mixture of two or more quaternary ammonium salt ionic liquids; the imidazole salt ionic liquid is a single imidazole salt ionic liquid, or a mixture of two or more imidazole salt ionic liquids; the pyridine salt ionic liquid is a single pyridine salt ionic liquid, or a mixture of two or more pyridine salt ionic liquids; The structural formula of quaternary ammonium salt ionic liquid is: （1）， In the structural formula (1), the cation is a quaternary ammonium ion; the anion is an inorganic acid anion; The structural formula of imidazole quaternary ammonium salt ionic liquid is: （2）， In the structural formula (2), the cation is an imidazolium ion or an imidazolium ion derivative; the anion is an inorganic acid anion; The structural formula of pyridine quaternary ammonium salt ionic liquid is: （3）， In the structural formula (3), the cation is a pyridinium ion or a pyridinium ion derivative; the anion is an inorganic acid anion; R1 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms, R2 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms, R3 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms, R4 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms, R5 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms, and R6 is a hydrogen ion or an alkyl group with 1 to 20 carbon atoms; the inorganic acid anion is a sulfate anion, a hydrochloride anion, a nitrate anion, a carbonate anion, a hydroiodide anion or a hydrobromide anion.

2. The method of claim 1, wherein the extraction solvent for recovering hexavalent chromium from a solution using a quaternary ammonium salt ionic liquid is characterized in that: The inert organic solvent is sulfonated kerosene, halogenated hydrocarbon compounds or aromatic compounds; or the inert organic solvent is a mixture of any two or three of sulfonated kerosene, halogenated hydrocarbon compounds and aromatic compounds; The halogenated hydrocarbon compound is a single halogenated hydrocarbon compound, or a mixture of two or more halogenated hydrocarbon compounds; the aromatic compound is a single aromatic compound, or a mixture of two or more aromatic compounds.

3. The method of claim 2, wherein the extraction solvent for recovering hexavalent chromium from a solution using a quaternary ammonium salt ionic liquid is characterized in that: The carbon number of sulfonated kerosene is 8 to 25, the halogenated hydrocarbon compounds are chlorinated hydrocarbons, brominated hydrocarbons or iodinated hydrocarbons; and the aromatic compounds are monophenyl aromatic hydrocarbons or polycyclic aromatic hydrocarbons.

4. The method of claim 1, wherein the extraction solvent for recovering hexavalent chromium from a solution using a quaternary ammonium salt ionic liquid is characterized in that: The ionic liquid and / or the diluent are in liquid state at room temperature; the mass fraction of the ionic liquid is 2 to 98 wt %.

5. A method for extracting and recovering hexavalent chromium in a solution using a quaternary ammonium salt ionic liquid, characterized in that: The steps include: Step (1) Preparation of the extracted organic phase: preparing the extraction solvent for extracting and recovering hexavalent chromium in the solution using the quaternary ammonium salt ionic liquid as claimed in claim 1 as the extracted organic phase; Step (2) extraction: extracting the hexavalent chromium in the hexavalent chromium-containing solution using the extraction organic phase, and obtaining a loaded organic phase after the extraction is completed; Step (3) washing: washing the loaded organic phase with salt solution A, and obtaining a washed organic phase after washing; Step (4) stripping: stripping the washed organic phase with salt solution B; after stripping, a stripping chromium solution and a stripping organic phase are obtained; Step (5) Regeneration: The stripping organic phase is regenerated using salt solution C to obtain a regenerated organic phase, which is returned to step (2) for recycling as the extraction organic phase.

6. The method for extracting hexavalent chromium from a solution by using a quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium according to claim 5, characterized in that: In step (2), the pH of the hexavalent chromium solution is 4 to 13, the extraction temperature is 5 to 95°C; the volume ratio of the extracted organic phase to the hexavalent chromium solution is 0.1 to 10.0:1; the extraction time is 0.5 to 60 minutes; the extraction method is countercurrent extraction, fractional extraction or cross-current extraction, and the extraction stage is 1 to 30; In step (3), the mass concentration of salt in salt solution A is 1 to 50 g / L; the pH of salt solution A is adjusted to 7 to 13 using the hydroxide corresponding to the salt in salt solution A, and the washing temperature is 5 to 95° C.; the volume ratio of the loaded organic phase to the salt solution A is 0.1 to 10.0:1; the washing time is 0.5 to 60 min; the washing method is countercurrent washing, fractional washing or cross-current washing, and the number of washing stages is 1 to 10; In step (4), the mass concentration of salt in salt solution B is 1 to 100 g / L; the pH of salt solution B is adjusted to 7 to 13 using the hydroxide corresponding to the salt in salt solution B, and the stripping temperature is 5 to 95° C.; the volume ratio of the washing organic phase to the salt solution B is 0.1 to 10.0:1; the stripping time is 0.5 to 60 min; the stripping method is countercurrent stripping, fractional stripping or cross-current stripping, and the stripping stage is 1 to 20; In step (5), the salt in the salt solution C is a soluble salt corresponding to the inorganic acid radical in the quaternary ammonium salt ionic liquid in the extracted organic phase, and the mass concentration of the salt solution C is 5 to 25 g / L; the regeneration temperature is 5 to 95°C; the volume ratio of the stripping organic phase to the salt solution C is 0.1 to 10.0:1; the regeneration time is 0.5 to 60 min; the regeneration method is countercurrent regeneration, fractional distillation regeneration or cross-current regeneration, and the regeneration stage is 1 to 10 stages.

7. The method for extracting hexavalent chromium from a solution by using a quaternary ammonium salt ionic liquid to extract and recover the hexavalent chromium according to claim 5, characterized in that: Salt solution A is one or a mixture of two or more of sodium carbonate solution, ammonium carbonate solution, potassium carbonate solution, sodium chloride solution, potassium chloride solution, ammonium chloride solution, sodium bromide solution, potassium bromide solution, ammonium bromide solution, sodium iodide solution, potassium iodide solution, ammonium iodide solution, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, sodium sulfate solution, potassium sulfate solution or ammonium sulfate solution; Salt solution B is one or a mixture of two or more of 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, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, ammonium bromide solution, sodium bromide solution, potassium bromide solution, sodium iodide solution, potassium iodide solution or ammonium iodide solution; The salt solution C is one or a mixture of two or more of 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, sodium nitrate solution, potassium nitrate solution, ammonium nitrate solution, ammonium bromide solution, sodium bromide solution, potassium bromide solution, sodium iodide solution, potassium iodide solution or ammonium iodide solution.

Images