Vanadium-containing tungstate separation and purification method

Abstract

The invention discloses a separation and purification method of vanadium-containing tungstate. The method comprises the following steps: providing a vanadium-containing tungstate aqueous solution; providing an extraction liquid, wherein the extraction liquid comprises a sulfuric acid type quaternary ammonium salt extraction agent, a modifier and an organic solvent; mixing the vanadium-containing tungstate aqueous solution with the extraction liquid, and performing first extraction to obtain a first extraction phase and a first raffinate phase; providing strip liquor, wherein the strip liquor comprises alkali metal sulfate and alkali metal hydroxide; mixing the first extraction phase with the strip liquor, and carrying out first reverse extraction to obtain an alkali metal vanadate solution; and carrying out the same extraction and reverse extraction method on the first raffinate phase to obtain an alkali metal tungstate radical solution, thereby realizing respective separation and purification of vanadate radicals and tungstate radicals.

Description

Technical Field

[0001] The invention relates to the technical field of recycling and reusing waste cemented carbide, and more specifically, to a method for separating and purifying vanadium-containing tungstate. Background Art

[0002] Tungstate is a salt whose anion contains tungstate or polytungstate. The crystal of tungstate contains WO4 2- The tetrahedral ion has excellent optical properties and chemical and physical stability, which makes it a component material for inorganic scintillators, fluorescent materials, Raman-active laser media, lithium-ion batteries and fuel cells. The vanadium content in tungsten products is strictly limited. For example, the mass ratio of V / WO3 in the production of 0-grade ammonium paratungstate (0-APT) should be less than 0.001%.

[0003] At present, the separation methods of vanadium in tungstate mainly include ammonium salt precipitation, iron salt precipitation and ion exchange resin. Among them, the separation of vanadium by ammonium salt precipitation is not thorough, and the iron salt precipitation will introduce iron ions and cause a large loss of tungsten, requiring tungsten to be extracted from the precipitate again. The ion exchange resin has a low working capacity and a long cycle time. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a novel method for separating and purifying vanadium-containing tungstate.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for separating and purifying vanadium-containing tungstate comprises the following steps:

[0007] Providing a vanadium-containing tungstate aqueous solution and adjusting its pH value to be alkaline, wherein the vanadium-containing tungstate aqueous solution comprises tungstate and vanadate;

[0008] Providing an extracting solution, the extracting solution comprising a sulfate-type quaternary ammonium salt extractant, a modifier and an organic solvent;

[0009] The vanadium-containing tungstate aqueous solution is mixed with the extract to perform a first extraction to obtain a first extraction phase and a first raffinate phase, wherein the vanadate enters the first extraction phase;

[0010] providing a stripping solution comprising an alkali metal sulfate and an alkali metal hydroxide;

[0011] The first extraction phase is mixed with the stripping solution to perform a first stripping to obtain the extraction solution and a first stripping raffinate phase, wherein the vanadate enters the first stripping raffinate phase to obtain an alkali metal vanadate solution;

[0012] The first raffinate phase is mixed with the extract, and a second extraction is performed to obtain a second extraction phase and a second raffinate phase, and the tungstate enters the second extraction phase;

[0013] The second extraction phase is mixed with the stripping liquid, and a second stripping is performed to obtain the extraction liquid and a second stripping raffinate phase, and the tungstate enters the second stripping raffinate phase to obtain an alkali metal tungstate solution.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects:

[0015] The embodiment of the present invention is based on the ion exchange method, and utilizes the different affinities between the existence forms of tungsten and vanadium and the sulfate-type quaternary ammonium salt to sequentially separate, purify and recover tungsten and vanadium; by adopting the sulfate-type quaternary ammonium salt extractant, sulfate and tungstate or vanadate are subjected to ion exchange, and the selectivity of ion exchange is higher; by adopting the stripping solution including alkali metal, the selectivity of stripping is also better, thereby achieving high purity, fast reaction, short cycle time and high production efficiency; by combining extraction and stripping, the extracting solution is recycled, and continuous operation can be achieved. DETAILED DESCRIPTION

[0016] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention discloses a method for separating and purifying vanadium-containing tungstate, comprising the following steps:

[0018] 1) providing a vanadium-containing tungstate aqueous solution, and adjusting its pH value to be alkaline, wherein the vanadium-containing tungstate aqueous solution comprises tungstate and vanadate.

[0019] In the above steps, the vanadium-containing tungstate aqueous solution includes not only tungstate and vanadate, but also other anions, and the cations may also include multiple types. Therefore, it is necessary to separate and purify the tungstate and vanadate in the vanadium-containing tungstate aqueous solution.

[0020] In the above steps, preferably, the pH of the vanadium-containing tungstate aqueous solution is 9-12, at which time the vanadium is mainly in the form of pentavalent vanadate HVO4 2- 、V2O7 4- 、V4O 12 4- etc.

[0021] 2) Providing an extracting solution, wherein the extracting solution comprises a sulfate-type quaternary ammonium salt extractant, a modifier and an organic solvent.

[0022] The present invention uses sulfate in the extractant to carry out ion exchange with vanadate or tungstate, which has higher selectivity, that is, the tungsten content in the final vanadate and the vanadium content in the tungstate are both low, and the separated product has high purity. Moreover, the ion exchange has high selectivity, so the extraction repetition times are small, the reaction is fast, and the production efficiency is high.

[0023] 3) Mixing the vanadium-containing tungstate aqueous solution with the extract, performing a first extraction, and obtaining a first extraction phase and a first raffinate phase, wherein the vanadate enters the first extraction phase and the tungstate remains in the first raffinate phase.

[0024] In the above steps, the different binding capacities of vanadate, tungstate and acidic quaternary ammonium salt are first utilized, and vanadate is first ion-exchanged with the sulfate of the extractant, and the vanadate enters the first extraction phase and combines with the quaternary ammonium salt, and the original sulfate of the quaternary ammonium salt enters the first raffinate phase, and tungstate and other ions of the vanadium-containing tungstate aqueous solution are all retained in the first raffinate phase.

[0025] In a specific embodiment, in the extract, the volume ratio of the sulfate-type quaternary ammonium salt extractant, the modifier and the organic solvent is 1:0.5-1.5:6-10.

[0026] The modifier includes a long-chain alcohol. Specifically, the long-chain alcohol includes one or more of 2-octanol, n-octanol, 2-hexanol, and n-hexanol.

[0027] The organic solvent includes one or more of sulfonated kerosene, sodium dodecylbenzene sulfonate, sodium hexadecylbenzene sulfonate and the like.

[0028] In a specific embodiment, during the first extraction process, the vanadium-containing tungstate aqueous solution and the extract are stirred and mixed at a stirring speed of 180-220 r / min and a stirring time of 3-8 min.

[0029] 4) Providing a stripping solution, wherein the stripping solution comprises an alkali metal sulfate and an alkali metal hydroxide.

[0030] The present invention combines alkali metal with vanadate or tungstate to strip vanadate or tungstate from the extraction phase with high selectivity, and adopts sulfate to allow the sulfate to enter the oil phase, regenerate the extractant of sulfate-type quaternary ammonium salt, reduce the extract, and make the extract recyclable.

[0031] Specifically, in a specific embodiment, the stripping solution includes 0.3-0.8 mol / L of alkali metal hydroxide and 0.8-1.2 mol / L of alkali metal sulfate.

[0032] 5) The first extraction phase is mixed with the stripping liquid, and a first stripping is performed to obtain an extraction liquid and a first stripping raffinate phase, wherein the vanadate enters the first stripping raffinate phase to obtain an alkali metal vanadate solution.

[0033] Preferably, the alkali metal is sodium, and sodium vanadate and sodium tungstate have high solubility in aqueous solution.

[0034] 6) The first raffinate phase is mixed with the extract, and a second extraction is performed to obtain a second extraction phase and a second raffinate phase, and the tungstate enters the second extraction phase. Other ions of the vanadium-containing tungstate aqueous solution are retained in the second raffinate phase, thereby achieving the purification and separation of the tungstate.

[0035] The tungstate in the first raffinate phase is further separated and purified by the same method as in the above step 3) and step 5).

[0036] Preferably, the extracting solution used in this step is the same as the extracting solution used in step 3), and the extracting solution of the present invention is selective for both tungstate and vanadate.

[0037] In a specific embodiment, during the second extraction process, the first raffinate phase and the extract are stirred and mixed at a stirring speed of 180-220 r / min and a stirring time of 3-8 min.

[0038] 7) The second extraction phase is mixed with the stripping liquid, and a second stripping is performed to obtain an extraction liquid phase and a second stripping raffinate phase, and the tungstate enters the second stripping raffinate phase to obtain an alkali metal tungstate solution.

[0039] The second stripping is carried out in the same manner as in step 5).

[0040] The method of the present invention further comprises the following steps:

[0041] 8) Evaporating and crystallizing the alkali metal vanadate solution to obtain a high-purity alkali metal vanadate product.

[0042] 9) Add ammonia water to the alkali metal tungstate solution for evaporation and crystallization to obtain high-purity ammonium paratungstate product.

[0043] The following are specific embodiments.

[0044] Example 1

[0045] 1) Take a certain amount of sodium tungstate (150 mg / L) solution with a vanadium concentration of 20 mg / L, and then adjust the solution pH to 9 with sulfuric acid. At this time, the vanadium is mainly in the form of HVO4 2- 、V2O7 4- 、V4O 12 4- etc.

[0046] 2) Selecting sulfate-type quaternary ammonium salt, 2-octanol and sulfonated kerosene in a volume ratio of 1:1:8 to prepare an extracting solution, mixing the extracting solution with the solution in step 1) in a volume ratio of 1:1, and then oscillating and stirring the extracting solution for 5 minutes at a speed of 200 r / min, so that vanadium enters the oil phase.

[0047] 3) The extracted vanadium solution is stripped, and the stripping agent is 0.5 mol / L NaOH and 1 mol / L Na2SO4 solution. The extractant is directly converted into a sulfate-type quaternary ammonium salt. The separated Na3VO4 solution is evaporated and crystallized to obtain a Na3VO4 product.

[0048] 4) After separation, the raffinate is extracted and stripped again through the above steps 2) and 3) to complete the enrichment of tungsten and obtain a sodium tungstate solution. Ammonia water is added to the obtained sodium tungstate solution for evaporation and crystallization to obtain a paratungstate amine product.

[0049] Comparative Example 1

[0050] The difference between Comparative Example 1 and Example 1 is that the components of the extractant and the stripping solution are different, the extractant is quaternary ammonium chloride, chloride ions are used instead of sulfate ions, and the stripping solution is sodium chloride instead of sodium sulfate. The rest are the same.

[0051] Comparative Example 2

[0052] The difference between Comparative Example 2 and Example 1 is that the composition of the extractant is different, and the extractant is alkylamine (N1923), and the rest are the same.

[0053] Test Case

[0054] The tungsten content in the sodium vanadate products obtained in Example 1 and Comparative Examples 1-2, and the vanadium content in the ammonium paratungstate products were tested respectively. The results are shown in Table 1.

[0055] Table 1: Test results of the test case

[0056] Tungsten content in sodium vanadate products Vanadium content in ammonium paratungstate products Example 1 Less than 0.1% Less than 0.1% Comparative Example 1 2.3％ 1.6％ Comparative Example 2 0.6％ 0.4％

[0057] It can be seen from Table 1 that the extraction agent and the stripping agent of the present invention can achieve higher purity purification. It should be noted that the extraction and stripping times in Example 1 and each comparative example are only once, and if the purity needs to be further improved, the extraction and stripping can be repeated.

[0058] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for separating and purifying vanadium-containing tungstate, characterized in that: The process includes: Providing a vanadium-containing tungstate aqueous solution and adjusting its pH value to be alkaline, wherein the vanadium-containing tungstate aqueous solution comprises tungstate and vanadate; Providing an extracting solution, the extracting solution comprising a sulfate-type quaternary ammonium salt extractant, a modifier and an organic solvent; The vanadium-containing tungstate aqueous solution is mixed with the extract to perform a first extraction to obtain a first extraction phase and a first raffinate phase, wherein the vanadate enters the first extraction phase; providing a stripping solution comprising an alkali metal sulfate and an alkali metal hydroxide; The first extraction phase is mixed with the stripping solution to perform a first stripping to obtain the extraction solution and a first stripping raffinate phase, wherein the vanadate enters the first stripping raffinate phase to obtain an alkali metal vanadate solution; The first raffinate phase is mixed with the extract, and a second extraction is performed to obtain a second extraction phase and a second raffinate phase, and the tungstate enters the second extraction phase; The second extraction phase is mixed with the stripping liquid, and a second stripping is performed to obtain the extraction liquid and a second stripping raffinate phase, and the tungstate enters the second stripping raffinate phase to obtain an alkali metal tungstate solution.

2. The method for separating and purifying vanadium-containing tungstate according to claim 1, characterized in that: The following processes are also included: The alkali metal vanadate solution is evaporated and crystallized to obtain an alkali metal vanadate product.

3. The method for separating and purifying vanadium-containing tungstate according to claim 1 or 2, characterized in that: The following processes are also included: Ammonia water is added to the alkali metal tungstate solution for evaporation and crystallization to obtain an ammonium paratungstate product.

4. The method for separating and purifying vanadium-containing tungstate according to claim 1, characterized in that: The pH of the vanadium-containing tungstate aqueous solution is 9-12.

5. The method for separating and purifying vanadium-containing tungstate according to claim 1, characterized in that: In the extract, the volume ratio of the sulfate-type quaternary ammonium salt extractant, the modifier and the organic solvent is 1:0.5-1.5:6-10; In the first extraction, the volume ratio of the vanadium-containing tungstate aqueous solution to the extract is 1:0.5-1.5; In the second extraction, the volume ratio of the first raffinate phase to the extract is 1:0.5-1.

5.

6. The method for separating and purifying vanadium-containing tungstate according to claim 5, characterized in that: The modifier includes a long-chain alcohol; The organic solvent includes one or more of sulfonated kerosene, sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate.

7. The method for separating and purifying vanadium-containing tungstate according to claim 6, characterized in that: The polarity improver long-chain alcohol includes one or more of 2-octanol, n-octanol, 2-hexanol and n-hexanol.

8. The method for separating and purifying vanadium-containing tungstate according to claim 1, characterized in that: During the first extraction process, the vanadium-containing tungstate aqueous solution and the extract are stirred and mixed, the stirring speed is 180-220 r / min, and the stirring time is 3-8 min; During the second extraction process, the first raffinate phase and the extract are stirred and mixed, the stirring speed is 180-220 r / min, and the stirring time is 3-8 min.

9. The method for separating and purifying vanadium-containing tungstate according to claim 1, characterized in that: The stripping solution includes 0.3-0.8 mol / L of alkali metal hydroxide and 0.8-1.2 mol / L of alkali metal sulfate.

10. The method for separating and purifying vanadium-containing tungstate according to claim 1 or 9, characterized in that: The alkali metal is sodium.