阅读说明：本技术 一种从碱性含钒铬溶液中萃取分离铬的方法 (Method for extracting and separating chromium from alkaline vanadium-chromium-containing solution ) 是由 王少娜 冯曼 杜浩 刘彪 王欣然 郑诗礼 于 2018-06-25 设计创作，主要内容包括：本发明提供了一种从碱性含钒铬溶液中萃取分离铬的方法,所述方法包括以下步骤：将含有离子液体萃取剂的有机溶液与碱性含钒铬溶液混合进行萃取,得到上下两层液体共存的体系,上层为含铬有机相,下层为含钒水相；将得到的含铬有机相与反萃剂溶液混合进行反萃处理,得到下层含铬水相和上层有机相,所述上层有机相返回循环使用。本发明所述方法可实现强碱性含钒铬溶液中铬的高效萃取以及钒的零萃取,钒铬分离效果显著,无第三相生成,铬的萃取率接近100％,铬的反萃率可达到100％；所述方法工艺流程简短,操作方便,萃取剂可循环使用,成本低廉。(The invention provides a method for extracting and separating chromium from an alkaline vanadium-chromium-containing solution, which comprises the following steps: mixing an organic solution containing an ionic liquid extractant and an alkaline vanadium-chromium-containing solution for extraction to obtain a system with coexisting upper and lower layers of liquid, wherein the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing water phase; and mixing the obtained chromium-containing organic phase with a stripping agent solution for stripping treatment to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase for recycling. The method can realize the high-efficiency extraction of chromium and the zero extraction of vanadium in the strong-alkaline solution containing vanadium and chromium, has obvious vanadium and chromium separation effect, does not generate a third phase, has the extraction rate of chromium close to 100 percent and has the back extraction rate of chromium up to 100 percent; the method has the advantages of short process flow, convenient operation, recyclable extracting agent and low cost.)

1. A method for the extractive separation of chromium from an alkaline vanadium-chromium containing solution, the method comprising the steps of:

(1) mixing an organic solution containing an ionic liquid extractant and an alkaline vanadium-chromium-containing solution for extraction to obtain a system with coexisting upper and lower layers of liquid, wherein the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing water phase;

(2) and (2) mixing the chromium-containing organic phase obtained in the step (1) with a stripping agent solution for stripping treatment to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase to the step (1) for recycling.

2. The process of claim 1, wherein the ionic liquid extractant of step (1) comprises trihexyltetradecylphosphine chloride.

3. The process of claim 1 or 2, wherein the organic solution containing an ionic liquid extractant of step (1) further comprises a modifier;

preferably, the modifying agent comprises a basic compound containing a lewis base functional group;

preferably, the modifier comprises any one or a combination of at least two of an organic phosphine oxide, a sulfone, or a sulfoxide;

preferably, the organic phosphine oxide comprises any one or a combination of at least two of tributyl phosphate, dibutyl butyl phosphonate, butyl butylphosphinate, tributyl phosphine oxide, trioctyl phosphine oxide, tris (2-ethylhexyl) phosphate or bis (2-ethylhexyl) phosphate, preferably tributyl phosphate;

preferably, the sulfone comprises any one or a combination of at least two of diphenyl sulfone, sulfolene, 4' -dihydroxydiphenyl sulfone, 4' -diaminodiphenyl sulfone, or 3,3' -diaminodiphenyl sulfone, preferably diphenyl sulfone;

preferably, the sulfoxide comprises diphenyl sulfoxide.

4. The process of any one of claims 1 to 3, wherein the organic solution containing the ionic liquid extractant of step (1) further comprises a diluent;

preferably, the diluent comprises C₆～C₁₀Alkane, C₇～C₈Of aromatic hydrocarbons or C₈～C₁₀Any one or a combination of at least two of the fatty alcohols of (a);

preferably, said C₆～C₁₀The alkane comprises any one or the combination of at least two of n-hexane, n-octane and n-decane, and is preferably n-octane;

preferably, said C₇～C₈The aromatic hydrocarbon of (a) includes toluene and/or o-xylene, preferably toluene;

preferably, said C₈～C₁₀The fatty alcohol of (b) includes n-octanol and/or n-decanol, preferably n-octanol.

5. The process according to any one of claims 1 to 4, wherein the ionic liquid extractant of step (1) has a molar concentration in the organic solution of 0.05 to 1.0mol/L, preferably 0.05 to 0.2 mol/L;

preferably, when the modifier is in a liquid phase, the volume fraction of the modifier in the organic solution is 0-75%, preferably 5-50%;

preferably, when the modifier is in a solid phase, the molar concentration of the modifier in the organic solution is 0.05-1.0 mol/L, and preferably 0.05-0.2 mol/L.

6. The method according to any one of claims 1 to 5, wherein the concentration of chromium in the vanadium-chromium containing solution in the step (1) is 1 to 1000mg/L, preferably 10 to 300 mg/L;

preferably, the concentration of vanadium in the vanadium-chromium-containing solution in the step (1) is 0.03-30 g/L, and preferably 0.3-9 g/L;

preferably, the pH value of the vanadium-chromium-containing solution in the step (1) is 8-14, and preferably 11-14.

7. The method according to any one of claims 1 to 6, wherein the volume ratio of the vanadium-chromium containing solution to the organic solution in the step (1) is (1-50): (8-1), preferably (1-10): 1;

preferably, the extraction in the step (1) is at least one-stage countercurrent extraction, and preferably three-stage to eight-stage countercurrent extraction;

preferably, the back extraction in the step (2) is at least one stage of counter current back extraction, preferably two to five stages of counter current back extraction;

preferably, the time of the single-stage extraction in the step (1) and the single-stage extraction in the back extraction in the step (2) is independently at least 1min, preferably 5-60 min, and further preferably 20-40 min;

preferably, after the extraction in the step (1) and the back extraction in the step (2), the centrifugal and/or standing treatment is independently carried out, so as to obtain a layered system.

8. The process according to any one of claims 1 to 7, wherein the stripping agent of step (2) comprises any one of alkali metal hydroxide, hydrochloric acid, sulfuric acid or nitric acid;

preferably, the alkali metal hydroxide is sodium hydroxide.

9. The process according to any one of claims 1 to 8, wherein the concentration of the stripping agent solution in the step (2) is 0.1 to 6.0mol/L, preferably 0.5 to 5.0 mol/L;

preferably, the volume ratio of the stripping agent solution in the step (2) to the chromium-containing organic phase obtained in the step (1) is 1 (1-50), and preferably 1 (1-30).

10. Method according to any of claims 1-9, characterized in that the method comprises the steps of:

(1) mixing an organic solution containing an ionic liquid extractant, a modifier and a diluent with an alkaline vanadium-chromium-containing solution with a pH value of 8-14 according to a volume ratio of (1-8) to (50-1) for extraction, wherein the molar concentration of the extractant in the organic solution is 0.05-1.0 mol/L, the volume fraction of the modifier in the organic solution is 0-75% when the modifier is a liquid phase, the molar concentration of the modifier in the organic solution is 0.05-1.0 mol/L when the modifier is a solid phase, the single-stage extraction time is at least 1min, centrifuging and/or standing to obtain a system with coexisting upper and lower layers of liquid, the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing aqueous phase;

(2) and (2) mixing the chromium-containing organic phase obtained in the step (1) with a stripping agent solution with the concentration of 0.1-6.0 mol/L according to the volume ratio of (1-50) to 1, carrying out stripping treatment, wherein the single-stage stripping time is at least 1min, centrifuging and/or standing to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase to the step (1) for recycling.

Technical Field

The invention belongs to the technical field of hydrometallurgy, and relates to a method for extracting and separating chromium from an alkaline vanadium-chromium-containing solution.

Background

Vanadium and chromium are adjacent in position in the periodic table of elements and similar in properties, and often exist in vanadium titano-magnetite in a co-associated form in nature, and because the content of vanadium in the vanadium titano-magnetite is generally low, the extraction of vanadium in the vanadium titano-magnetite is often realized by processes of concentrate smelting, extraction of vanadium from molten iron, extraction of vanadium oxide from vanadium slag and the like. At present, the process for extracting vanadium from vanadium slag mainly comprises a pyrogenic process roasting process and a wet process liquid phase oxidation process, wherein the pyrogenic process roasting process comprises sodium salt roasting, calcification roasting, blank roasting and the like, and the wet process liquid phase oxidation process generally uses strong alkali as a medium.

At present, the method for separating vanadium and chromium from solution mainly comprises a precipitation method, a crystallization method, an ion exchange method, a solvent extraction method and the like. The precipitation method mainly utilizes the difference of precipitation conditions of vanadium and chromium in a solution, and precipitates the vanadium and the chromium in the solution step by controlling the pH value of the solution or adding a precipitator. The crystallization method is similar to the precipitation method, and usually adopts fractional crystallization, namely a method of firstly cooling and crystallizing to obtain vanadate, and then evaporating and crystallizing to obtain chromate to realize the primary separation of vanadium and chromium. The method is generally suitable for extracting vanadium from vanadium slag or extracting vanadium and chromium together by using alkali solutions such as NaOH and KOH, for example, CN 102127655A, CN 102534232A and CN101812588A realize the co-extraction of vanadium and chromium in vanadium slag. However, the fractional crystallization method is limited by separation efficiency and solution entrainment, and the obtained vanadate intermediate product can carry chromium, so that the subsequent conversion of the product is greatly influenced.

The ion exchange method is to separate vanadium and chromium in an aqueous solution by taking anion exchange resin as a separation medium, and the difference of the adsorption capacity of the ion exchange resin on the vanadium and chromium is regulated and controlled by controlling the pH value of the solution. Although the method has good effect of separating vanadium and chromium, the adsorption capacity of the resin is limited, the regeneration performance is not good, the problems of large resin consumption and high production cost can be caused, the operation is complex, and large-scale continuous production is not easy to realize. CN 107190155 a discloses a method for extracting vanadium and chromium from a mixed solution containing vanadium and chromium, which comprises adsorbing and separating vanadium in the solution by using exchange resin under acidic condition, desorbing vanadium and further precipitating vanadium to prepare vanadate, and precipitating chromium to obtain chromium product.

The solvent extraction method for separating vanadium and chromium has the advantages of good separation effect, large extraction capacity, easiness in continuous production and the like, but the existing vanadium and chromium separation method mostly focuses on the fact that a solution is acidic, neutral or weakly alkaline, and mainly extracts and separates vanadium. The pH value of the solution obtained after the vanadate is dissolved is more than 11-14, the concentration of vanadium in the solution is high, the concentration of chromium in the solution is low, the existing method is adopted, acid needs to be added firstly to adjust the pH value of the solution, the steps are complex, the vanadium-chromium separation efficiency is low, and efficient separation of chromium is difficult to achieve. CN 104694749 a discloses a method for extracting and separating vanadium and chromium from an alkaline aqueous solution, wherein an amine extractant is used to extract and separate vanadium and chromium from an alkaline aqueous solution, but the extraction saturation capacity of the extractant on vanadium is reduced by the impurities, and the impurities are precipitated together with vanadium in the subsequent vanadium precipitation operation to affect the purity of the product. In addition, one of the important ways to improve the separation effect is to find a novel extractant capable of realizing vanadium-chromium separation, and CN 107312942 a discloses a method for extracting and separating vanadium and chromium from a vanadium-chromium slag pickle liquor, wherein the method adopts ionic liquid of which the cation is alkyl-substituted imidazole as an extractant to extract vanadium and chromium, and then performs back extraction to obtain chromium-containing back raffinate and a precipitate of vanadium, but the method still treats an acidic solution, the extractant jointly extracts vanadium and chromium, and the vanadium and chromium need to be separated again, so that more steps are needed, and the separation is incomplete.

In summary, finding a simple and efficient method for separating vanadium and chromium in a solution under an alkaline condition is one of the problems to be solved urgently.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a method for extracting and separating chromium from an alkaline vanadium-chromium-containing solution, wherein the method adopts an ionic liquid extraction solution to extract chromium from the alkaline vanadium-chromium-containing solution, and the vanadium-chromium separation effect is obvious; the method has simple process flow, recyclable organic extraction solution and low cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a method for extracting and separating chromium from an alkaline vanadium-chromium-containing solution, which comprises the following steps:

(1) mixing an organic solution containing an ionic liquid extractant and an alkaline vanadium-chromium-containing solution for extraction to obtain a system with coexisting upper and lower layers of liquid, wherein the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing water phase;

(2) and (2) mixing the chromium-containing organic phase obtained in the step (1) with a stripping agent solution for stripping treatment to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase to the step (1) for recycling.

In the invention, the organic solution containing the ionic liquid extractant is adopted, so that the chromium with relatively low content in the alkaline vanadium-chromium-containing solution can be extracted and separated, and the principle of extracting the chromium is as follows: the ionic liquid has a three-dimensional cationic structure, can effectively combine chromate but not vanadate in an alkaline system to realize selective extraction and separation of vanadium and chromium, and has the advantages of high extraction rate, obvious separation effect, less extractant dosage, recyclability and low cost.

The following technical solutions are preferred but not limited to the technical solutions provided by the present invention, and the technical objects and advantages of the present invention can be better achieved and realized by the following technical solutions.

As a preferred technical scheme of the invention, the ionic liquid extracting agent in the step (1) comprises trihexyltetradecylphosphonium chloride.

In the invention, the adopted ionic liquid extractant trihexyltetradecyl phosphorus chloride is expressed by Cyphos IL 101, is an ionic liquid with a three-dimensional cationic structure, can react with oxoacid salt anions in an alkaline system, and realizes the high-efficiency extraction and separation of chromium.

As a preferable technical scheme of the invention, the organic solution containing the ionic liquid extractant in the step (1) further comprises a modifier.

Preferably, the modifier comprises a basic compound containing a lewis base functional group.

Preferably, the modifier comprises any one of, or a combination of at least two of, an organophosphine oxide, a sulfone, or a sulfoxide, typical but non-limiting examples of which are: combinations of organophosphine oxides and sulfones, sulfones and sulfoxides, combinations of organophosphine oxides, sulfones and sulfoxides, and the like.

Preferably, the organic phosphine oxide comprises any one of tributyl phosphate, dibutyl butyl phosphonate, butyl dibutylphosphinate, tributyl phosphine oxide, trioctyl phosphine oxide, tris (2-ethylhexyl) phosphate or bis (2-ethylhexyl) phosphate, or a combination of at least two of these, typical but non-limiting examples being: a combination of tributyl phosphate and dibutyl butyl phosphonate, a combination of tributyl phosphine oxide and trioctyl phosphine oxide, a combination of dibutyl butyl phosphonate, butyl dibutyl phosphinate and tris (2-ethylhexyl) phosphate, a combination of tributyl phosphate, dibutyl butyl phosphonate, tributyl phosphine oxide and bis (2-ethylhexyl) phosphate, and the like, with tributyl phosphate being preferred.

Preferably, the sulfone comprises any one or a combination of at least two of diphenyl sulfone, sulfolene, 4' -dihydroxydiphenyl sulfone, 4' -diaminodiphenyl sulfone or 3,3' -diaminodiphenyl sulfone, typical but non-limiting examples of which are: a combination of diphenyl sulfone and sulfolene, a combination of 4,4 '-dihydroxydiphenyl sulfone and 4,4' -diaminodiphenyl sulfone, a combination of sulfolene, 4,4 '-dihydroxydiphenyl sulfone and 3,3' -diaminodiphenyl sulfone, and the like, with diphenyl sulfone being preferred.

Preferably, the sulfoxide comprises diphenyl sulfoxide.

In the invention, the modifier is an alkaline compound with a stronger Lewis base functional group, and comprises organic phosphine oxide, sulfone or sulfoxide and the like, and can adjust the apparent alkalinity of an extraction system, so that the binding capacity of vanadate ions and the extraction agent is weakened, and the binding capacity of chromate ions and the extraction agent is strengthened, thereby better realizing the selective extraction of chromium.

As a preferable technical scheme of the invention, the organic solution containing the ionic liquid extractant in the step (1) further comprises a diluent.

In the invention, the ionic liquid extractant and the nonpolar diluent have good mixing effect and low solubility in an aqueous solution, and the diluent is added into the extractant, so that the concentration of the extract in an organic phase can be reduced, and the supersaturated extract is prevented from being accumulated on an oil-water two-phase interface, thereby preventing the extraction process from being carried out.

Preferably, the diluent comprises C₆～C₁₀Alkane, C₇～C₈Of aromatic hydrocarbons or C₈～C₁₀Of any one or a combination of at least two of the fatty alcohols of (a), typical but non-limiting examples being: c₆～C₁₀Alkane and C₇～C₈Combinations of aromatic hydrocarbons of (2), C₇～C₈And C is an aromatic hydrocarbon₈～C₁₀A combination of fatty alcohols of (C)₆～C₁₀Alkane, C₇～C₈And C is an aromatic hydrocarbon₈～C₁₀Combinations of the fatty alcohols of (a) and the like.

In the invention, when the type of the diluent is selected, the organic diluent with reducibility such as kerosene, sulfonated kerosene and the like is avoided, because chromium exists in hexavalent form in the alkaline vanadium-chromium-containing solution and is easy to generate redox reaction when being contacted with a solvent with reducibility for a long time, the diluent is selected from C which is insoluble in water and has strong oxidation resistance₆～C₁₀Alkane, C₇～C₈Of aromatic hydrocarbons or C₈～C₁₀The fatty alcohol of (1).

Preferably, said C₆～C₁₀The alkane of (a) includes any one of n-hexane, n-octane or n-decane, or a combination of at least two thereof, as typical but non-limiting examples: a combination of n-hexane and n-octane, a combination of n-octane and n-decane, a combination of n-hexane, n-octane, and n-decane, etc., with n-octane being preferred.

Preferably, said C₇～C₈The aromatic hydrocarbon of (a) includes toluene and/or o-xylene, preferably toluene.

Preferably, said C₈～C₁₀The fatty alcohol of (b) includes n-octanol and/or n-decanol, preferably n-octanol.

In a preferred embodiment of the present invention, the ionic liquid extractant in step (1) has a molar concentration in the organic solution of 0.05 to 1.0mol/L, for example, 0.05mol/L, 0.1mol/L, 0.15mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.8mol/L, or 1.0mol/L, but not limited to the above-mentioned values, and any values not listed in this range of values are also applicable, and preferably 0.05 to 0.2 mol/L.

Preferably, when the modifier in step (1) is in a liquid phase, the volume fraction of the organic solution is 0 to 75%, for example, 0, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, or 75%, but not limited to the recited values, and values not recited in this range are also applicable, preferably 5 to 50%.

Preferably, when the modifier in step (1) is in a solid phase, the molar concentration of the modifier in the organic solution is 0.05 to 1.0mol/L, such as 0.05mol/L, 0.1mol/L, 0.15mol/L, 0.2mol/L, 0.3mol/L, 0.4mol/L, 0.5mol/L, 0.6mol/L, 0.8mol/L, or 1.0mol/L, but not limited to the values listed, and values not listed in the range of the values are equally applicable, preferably 0.05 to 0.2 mol/L.

In the invention, the content of the diluent in the organic solution is adjusted according to the content of the extracting agent and the modifying agent so as to ensure the concentration of the extracting agent and the modifying agent.

In a preferred embodiment of the present invention, the concentration of chromium in the vanadium-chromium-containing solution in step (1) is 1 to 1000mg/L, for example, 1mg/L, 10mg/L, 50mg/L, 100mg/L, 200mg/L, 300mg/L, 400mg/L, 500mg/L, 600mg/L, 800mg/L, or 1000mg/L, but is not limited to the values listed above, and values not listed in this range are also applicable, preferably 10 to 300 mg/L.

Preferably, the concentration of vanadium in the vanadium-chromium containing solution of step (1) is 0.03-30 g/L, such as 0.03g/L, 0.1g/L, 0.3g/L, 0.5g/L, 1g/L, 3g/L, 5g/L, 9g/L, 15g/L, 20g/L, 25g/L or 30g/L, but not limited to the recited values, and values not recited in this range are equally applicable, preferably 0.3-9 g/L.

In the invention, the content of vanadium in the vanadium-chromium-containing solution is higher than that of chromium, so that when extraction is carried out, chromium is extracted by selecting a proper extracting agent, the using amount of the extracting agent can be greatly reduced, and the cost is reduced.

Preferably, the pH of the vanadium-chromium containing solution in step (1) is 8 to 14, such as 8, 9, 10, 11, 12, 13 or 14, but not limited to the recited values, and values not recited in this range are also applicable, preferably 11 to 14.

In a preferred embodiment of the present invention, the volume ratio of the vanadium-chromium-containing solution to the organic solution in step (1) is (1-50): 8-1, for example, 1:8, 1:4, 1:1, 2:1, 5:1, 10:1, 20:1, 30:1, 40:1 or 50:1, but the present invention is not limited to the above-mentioned values, and values not listed in the above-mentioned value range are also applicable, and (1-10): 1 is preferred.

Preferably, the extraction in step (1) is at least one stage of countercurrent extraction, such as one, two, three, four, five, six or eight stages, but not limited to the recited values, and values not recited in the range of values are equally applicable, preferably three to eight stages of countercurrent extraction.

Preferably, the stripping in step (2) is at least one stage of counter-current stripping, such as one stage, two stages, three stages, four stages, five stages or six stages, but not limited to the values listed, and the values not listed in the range of the values are also applicable, and preferably two to five stages of counter-current stripping are used.

Preferably, the time of the single-stage extraction in the step (1) and the back extraction in the step (2) is independently at least 1min, such as 1min, 5min, 10min, 20min, 25min, 30min, 35min, 40min, 50min, 60min or 80min, but not limited to the enumerated values, and the same applies to the non-enumerated values in the range of the enumerated values, preferably 5 to 60min, and more preferably 20 to 40 min.

Preferably, after the extraction in the step (1) and the back extraction in the step (2), the centrifugal and/or standing treatment is independently carried out, so as to obtain a layered system.

In the invention, the back extraction treatment is carried out to back extract chromium from the organic phase, so that the chromium is convenient to recycle, and the ionic liquid extractant is regenerated to realize the recycling of the extractant.

As a preferable technical scheme of the invention, the stripping agent in the step (2) comprises any one of alkali metal hydroxide, hydrochloric acid, sulfuric acid or nitric acid.

Preferably, the alkali metal hydroxide is sodium hydroxide.

As a preferred embodiment of the present invention, the concentration of the stripping solution in step (2) is 0.1 to 6.0mol/L, for example, 0.1mol/L, 0.5mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L, 2.5mol/L, 3.0mol/L, 3.5mol/L, 4.0mol/L, 5.0mol/L or 6.0mol/L, but not limited to the above-mentioned values, and the values not listed in the above-mentioned value range are also applicable, and preferably 0.5 to 5.0 mol/L.

Preferably, the volume ratio of the stripping agent solution in the step (2) to the chromium-containing organic phase obtained in the step (1) is 1 (1-50), such as 1:1, 1:3, 1:6, 1:10, 1:15, 1:20, 1:25, 1:30, 1:40 or 1:50, but not limited to the recited values, and the same applies to the values not recited in the range of the recited values, and preferably 1 (1-30).

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) mixing an organic solution containing an ionic liquid extractant, a modifier and a diluent with an alkaline vanadium-chromium-containing solution with a pH value of 8-14 according to a volume ratio of (1-8) to (50-1) for extraction, wherein the molar concentration of the extractant in the organic solution is 0.05-1.0 mol/L, the volume fraction of the modifier in the organic solution is 0-75% when the modifier is a liquid phase, the molar concentration of the modifier in the organic solution is 0.05-1.0 mol/L when the modifier is a solid phase, the single-stage extraction time is at least 1min, centrifuging and/or standing to obtain a system with coexisting upper and lower layers of liquid, the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing aqueous phase;

(2) and (2) mixing the chromium-containing organic phase obtained in the step (1) with a stripping agent solution with the concentration of 0.1-6.0 mol/L according to the volume ratio of (1-50) to 1, carrying out stripping treatment, wherein the single-stage stripping time is at least 1min, centrifuging and/or standing to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase to the step (1) for recycling.

Compared with the prior art, the invention has the following beneficial effects:

(1) the method adopts the ionic liquid extractant to realize the high-efficiency extraction of chromium and the zero extraction of vanadium in the alkaline vanadium-chromium-containing solution, the vanadium-chromium separation effect is obvious, no third phase is generated, the extraction rate of chromium is close to 100 percent, and the back extraction rate of chromium can reach 100 percent;

(2) the method has the advantages of short process flow, convenient operation, recyclable extracting agent and low cost.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

The invention provides, in part, a method for the extractive separation of chromium from an alkaline vanadium-chromium containing solution, the method comprising the steps of:

(1) mixing an organic solution containing an ionic liquid extractant and an alkaline vanadium-chromium-containing solution for extraction to obtain a system with coexisting upper and lower layers of liquid, wherein the upper layer is a chromium-containing organic phase, and the lower layer is a vanadium-containing water phase;

(2) and (2) mixing the chromium-containing organic phase obtained in the step (1) with a stripping agent solution for stripping treatment to obtain a lower chromium-containing aqueous phase and an upper organic phase, and returning the upper organic phase to the step (1) for recycling.

The following are typical but non-limiting examples of the invention: