Vanadium electrolyte, preparation method and application thereof

Abstract

The application provides a vanadium electrolyte and a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing a compound containing pentavalent vanadium and a sulfuric acid solution to obtain a pentavalent vanadium solution; (2) performing electrolytic reduction on the pentavalent vanadium solution in step (1) to obtain a first vanadium ion solution; simultaneously with the electrolytic reduction, the pentavalent vanadium solution in the electrolytic reduction process is irradiated with first ultraviolet light, or after the electrolytic reduction is completed, the first vanadium ion solution is irradiated with second ultraviolet light to obtain a second vanadium ion solution; and (3) performing extraction and reverse extraction on the first vanadium ion solution or the second vanadium ion solution in step (2) to obtain the vanadium electrolyte. By using the above preparation method, the purity of the vanadium electrolyte and the recovery rate of vanadium are effectively improved, the content of vanadium ions in different valence states in the product can be flexibly controlled, and the vanadium electrolyte can be widely applied to a full vanadium redox flow battery and other industrial fields requiring trivalent and tetravalent vanadium solutions.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of all-vanadium redox flow batteries and preparation of electrolytes thereof, and relates to a vanadium electrolyte and a preparation method and application thereof. BACKGROUND

[0002] The all-vanadium redox flow battery (vanadium battery) has become the liquid flow battery with the highest commercialization degree and technical maturity at the present stage due to its high safety and long cycle life. The vanadium electrolyte, as the core material of the vanadium battery, has a large amount of use, and the cost usually accounts for 50% to 80% of the total initial installation cost of the battery, thus becoming one of the main bottlenecks restricting the industrialization development of the all-vanadium redox flow battery.

[0003] In the prior art, the traditional vanadium electrolyte preparation process mainly includes a physical dissolution method and a chemical reduction method. The physical dissolution method is to directly dissolve VOSO4, but due to the high price and limited yield of VOSO4, the production cost is high, and it is difficult to realize large-scale promotion. The chemical reduction method is to dissolve high-purity V2O5 in a sulfuric acid solution, and after cooling and dilution, an oxalic acid or sulfur dioxide is added as a reducing agent for reduction and filtration to obtain a tetravalent vanadium electrolyte. However, the reducing agent (such as sulfur dioxide gas) used in the above chemical reduction process not only has environmental pollution and operation risks, but also produces a large amount of waste salt by-products, resulting in further increase of subsequent treatment burden and cost.

[0004] For example, CN114772642A provides a preparation method of a high-purity vanadyl sulfate solution, which uses vanadium pentoxide as a raw material, and reacts by adding oxalic acid, dilute sulfuric acid, fuming sulfuric acid, hydrogen peroxide and other purifying agents to obtain a high-purity vanadyl sulfate solution; although this scheme can improve the purity of the product, the types of purifying agents added are more, the process is more complex, and the use amount of chemical reagents such as oxalic acid and fuming sulfuric acid is large, which is easy to produce more waste salt by-products, increase the difficulty and cost of subsequent treatment, and also has a certain risk of environmental pollution.

[0005] The electrochemical reduction process can reduce vanadium ions to the required valence level by adjusting process parameters such as current and voltage. In addition, under certain conditions, electrochemical reduction can also reduce the amount of chemical reducing agent, reduce the cost of raw materials and environmental risk, and show good industrial application prospect. However, the purity and low-valence vanadium content of the vanadium electrolyte prepared by the electrolysis method are still limited, and the production efficiency is low, which needs to be further improved.

[0006] Therefore, how to further improve the purity and low-valence vanadium content of the vanadium electrolyte prepared by the electrolysis method and improve the production efficiency is a technical problem to be solved. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application aims to provide a vanadium electrolyte and a preparation method and application thereof. The present application effectively inhibits the occurrence of intermediate side reactions and reduces the content of impurity ions by using a preparation method combining electrolytic reduction with ultraviolet light irradiation and extraction-back extraction, thereby ensuring high vanadium recovery rate and accurately regulating the content of vanadium ions of different valence states in the product; the preparation method of the present application effectively avoids the use of traditional reducing agents, simplifies the preparation process of the vanadium electrolyte, improves the production efficiency, reduces environmental pollution and raw material cost, and the obtained vanadium electrolyte has a high content of low-valence vanadium and exhibits good electrochemical performance, and can be widely applied to all-vanadium redox flow batteries and other industrial fields requiring vanadium solutions of valence 3 and 4.

[0008] To achieve the object of the present application, the present application adopts the following technical solutions:

[0009] In a first aspect, the present application provides a method for preparing a vanadium electrolyte, which comprises:

[0010] (1) mixing a compound containing pentavalent vanadium and a sulfuric acid solution to obtain a pentavalent vanadium solution;

[0011] (2) electrolytically reducing the pentavalent vanadium solution of step (1) to obtain a first vanadium ion solution;

[0012] At the same time of the electrolytic reduction, the pentavalent vanadium solution in the electrolytic reduction process is subjected to first ultraviolet light irradiation;

[0013] Or, after the completion of the electrolytic reduction, the first vanadium ion solution is subjected to second ultraviolet light irradiation to obtain a second vanadium ion solution;

[0014] (3) extracting and back-extracting the first vanadium ion solution of step (2) or the second vanadium ion solution to obtain the vanadium electrolyte.

[0015] In the present application, the introduction of ultraviolet light irradiation during or after the electrolysis process and the combination of extraction-back extraction can improve the purity and concentration of the vanadium ion solution and make the valence state of vanadium ions in the solution more stable. This is because ultraviolet light can initiate photochemical reactions to decompose impurities in the raw material or by-products generated during the electrolysis process, and can also change the chemical environment around the vanadium ions, thereby inhibiting the change of the valence state of the vanadium ions and improving the stability of the vanadium electrolyte; the extraction-back extraction process further improves the purity of vanadium by separating vanadium from impurities, and at the same time, the selectivity of different extractants for vanadium ions of different valence states can also regulate the content of vanadium ions of different valence states in the product to some extent; the present application, through the mutual cooperation of the three processes of electrolytic reduction, ultraviolet light irradiation and extraction-back extraction, avoids the use of reducing agents, and also makes the vanadium electrolyte have higher purity, higher content of low-valence vanadium and higher stability.

[0016] The following is a preferred technical solution of the present application, but not as a restriction on the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and implemented.

[0017] Preferably, the concentration of the sulfuric acid solution in step (1) is 1 mol / L to 5 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0018] In the present application, the concentration of sulfuric acid will affect the electron transfer rate in the subsequent electrolytic reduction process and the purity of the product; by controlling the concentration of the sulfuric acid solution in the range of 1 mol / L to 5 mol / L, the occurrence of side reactions can be effectively inhibited, and the electrolysis rate is faster.

[0019] The present application does not limit the type of pentavalent vanadium compound. Exemplarily, the pentavalent vanadium compound includes any one or a combination of at least two of pentavalent vanadium leaching solution, ammonium metavanadate, sodium metavanadate, ammonium polyvanadate, or di vanadium pentoxide.

[0020] Preferably, the mixing method of step (1) includes stirring.

[0021] Preferably, the temperature of the mixing of step (1) is 40℃ to 90℃, for example, 40℃, 50℃, 60℃, 70℃, 80℃, or 90℃, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0022] Preferably, the electrolytic reduction of step (2) is carried out in an electrolytic cell, which includes a cathode region, an anode region, and a diaphragm for separating the cathode region and the anode region.

[0023] Preferably, the cathode region includes the pentavalent vanadium solution of step (1), and the anode region includes a sulfuric acid solution.

[0024] Preferably, the diaphragm includes an organic high molecular cation diaphragm, which includes a perfluorosulfonic acid type exchange membrane or a polybenzimidazole type exchange membrane.

[0025] Preferably, the material of the electrolytic cell includes an acid and alkali corrosion resistant polymer material, which includes polypropylene, polyvinyl chloride, polyvinylidene fluoride, or polytetrafluoroethylene.

[0026] Preferably, the cathode of the electrolytic cell includes any one or a combination of at least two of a graphite electrode, a carbon felt electrode, a carbon paper electrode, or a coated titanium electrode.

[0027] Preferably, the anode of the electrolytic cell comprises any one of or a combination of at least two of a titanium electrode, an iridium tantalum oxide coated titanium electrode, a ruthenium iridium oxide coated titanium electrode or a titanium nitride surface modified titanium electrode.

[0028] Preferably, the current density of the electrolytic reduction in step (2) is 20 mA / cm 2 ~ 200 mA / cm 2 , for example 20 mA / cm 2 , 50 mA / cm 2 , 70 mA / cm 2 , 100 mA / cm 2 , 130 mA / cm 2 , 170 mA / cm 2 , or 200 mA / cm 2 , but not limited to the listed values, and other unlisted values within the range are also applicable.

[0029] In the present application, the current density during the electrolytic reduction process affects the reaction rate and the distribution of the valence state of the product. In practical applications, different current densities can be selected according to the content requirements of different valence state vanadium ions and energy consumption requirements; by controlling the current density of the electrolytic reduction within the range of 20 mA / cm 2 ~ 200 mA / cm 2 , the occurrence of side reactions can be effectively avoided.

[0030] Preferably, the temperature of the electrolytic reduction in step (2) is 40℃ ~ 90℃, for example 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃, but not limited to the listed values, and other unlisted values within the range are also applicable.

[0031] In the present application, during the electrolytic reduction of vanadium, the temperature affects the valence state of the product through both thermodynamic and kinetic mechanisms. When the temperature is controlled within the range of 40℃ ~ 90℃, the higher ion mobility and reaction activity can accelerate the reduction reaction rate.

[0032] Preferably, the time of the electrolytic reduction in step (2) is 3h ~ 5h.

[0033] Preferably, the electrolytic reduction in step (2) is carried out under stirring.

[0034] It should be noted that in the present application, whether it is the first ultraviolet light or the second ultraviolet light, the process of ultraviolet light is the same, and the parameter range of ultraviolet light is the same, but each is independent.

[0035] Preferably, the wavelength of the first ultraviolet irradiation in step (2) and the wavelength of the second ultraviolet irradiation in step (2) are each independently 100 nm to 280 nm, such as 100 nm, 130 nm, 160 nm, 180 nm, 200 nm, 230 nm, 260 nm, or 280 nm, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0036] Preferably, the time of the first ultraviolet irradiation in step (2) and the time of the second ultraviolet irradiation in step (2) are each independently 20 min to 60 min, such as 20 min, 30 min, 40 min, 50 min, or 60 min, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0037] In the present application, by adjusting the time of ultraviolet irradiation, the content of vanadium ions of different valence states can also be flexibly adjusted; by controlling the time of the first ultraviolet irradiation and the time of the second ultraviolet irradiation each independently in the range of 20 min to 60 min, it is more conducive to achieving uniform distribution of trivalent and tetravalent vanadium ions.

[0038] Preferably, the light source of the first ultraviolet irradiation in step (2) and the light source of the second ultraviolet irradiation in step (2) each independently include a UVC light source or a VUV light source.

[0039] Preferably, the UVC light source includes a low-pressure mercury lamp, and the VUV light source includes a vacuum ultraviolet lamp.

[0040] Preferably, the first ultraviolet irradiation in step (2) and the second ultraviolet irradiation in step (2) are each independently carried out in the cathode region of the electrolytic cell or a separate ultraviolet irradiation reactor.

[0041] Preferably, the extractant in the extraction liquid in step (3) includes an organic phosphate ester.

[0042] Preferably, the organic phosphate ester includes any one or a combination of at least two of P204, P507, or TBP.

[0043] Preferably, the volume fraction of the extractant in the extraction liquid is 5% to 20%, such as 5%, 7%, 10%, 12%, 14%, 16%, 18%, or 20%, etc., but not limited to the listed values, and other values not listed in this range are also applicable, based on the volume fraction of the extraction liquid being 100%.

[0044] It should be noted that in the present application, the extraction and stripping processes are the same for both the first vanadium ion solution and the second vanadium ion solution, and the parameter ranges for extraction are the same, but each is independent.

[0045] Preferably, the volume ratio of the extraction liquid to the first vanadium ion solution or the volume ratio of the extractant to the second vanadium ion solution is each independently (1-4):1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, or 4:1, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0046] In the present application, by controlling the volume ratio (O / A) of the extraction liquid to the first vanadium ion solution or the second vanadium ion solution within the range of (1-4):1, the separation efficiency of vanadium and impurity ions can be optimized. Within this range, sufficient organic phase volume ensures efficient loading of vanadium. Experiments show that when O / A>4, the marginal effect of vanadium recovery increases and emulsification may occur, so setting the upper limit of the volume ratio to 4:1 is more conducive to improving the recovery rate of vanadium.

[0047] Preferably, the extraction temperature of step (3) is 25-40℃, such as 25℃, 28℃, 30℃, 32℃, 34℃, 36℃, 38℃, or 40℃, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0048] In the present application, the extraction temperature will affect the extraction effect; by controlling the extraction temperature within the range of 25-40℃, it can be ensured that the extractant will not crystallize or volatilize, and has good solubility for the target extract.

[0049] Preferably, the extraction of step (3) is carried out under stirring.

[0050] Preferably, the stripping liquid for the stripping of step (3) comprises a sulfuric acid solution.

[0051] Preferably, the concentration of the sulfuric acid solution is 1.5-2.0 mol / L, such as 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2.0 mol / L, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0052] Preferably, the volume ratio of the organic liquid to the stripping liquid after the extraction of step (3) is (0.9-1.1):1, such as 0.9:1, 1:1, or 1.1:1, etc., but not limited to the listed values, and other values not listed in this range are also applicable.

[0053] As a preferred technical solution of the present application, the method comprises the following steps:

[0054] (1) mixing a compound containing pentavalent vanadium and a sulfuric acid solution with a concentration of 1 mol / L-5 mol / L at 40-90°C under stirring to obtain a pentavalent vanadium solution;

[0055] (2) separating the cathode zone and the anode zone of an electrolytic cell with a diaphragm, placing the pentavalent vanadium solution of step (1) in the cathode zone of the electrolytic cell and placing a sulfuric acid solution in the anode zone of the electrolytic cell, and then electrolytically reducing the pentavalent vanadium solution of step (1) under stirring at a current density of 20-200 mA / cm 2 2 2 and a temperature of 40-90°C to obtain a first vanadium ion solution; after the electrolytic reduction is completed, irradiating the first vanadium ion solution with ultraviolet light with a wavelength of 100-280 nm for 20-60 min to obtain a second vanadium ion solution;

[0056] (3) preparing an extraction liquid according to a volume ratio of an extraction agent in the extraction liquid of 5%-20%, and extracting the second vanadium ion solution according to a volume ratio of the extraction liquid to the first vanadium ion solution or the second vanadium ion solution (1-4):1 at 25-40°C and under stirring; then using a sulfuric acid solution with a concentration of 1.5-2.0 mol / L as a back-extraction agent and performing back-extraction according to a volume ratio of the organic liquid after the extraction to the back-extraction liquid (0.9-1.1):1 to obtain the vanadium electrolyte;

[0057] The extraction agent of the extraction includes an organic phosphate, and the organic phosphate includes any one or a combination of at least two of P204, P507 or TBP.

[0058] In a second aspect, the present application provides a vanadium electrolyte prepared by the method for preparing a vanadium electrolyte according to the first aspect.

[0059] Preferably, in the vanadium electrolyte, the total vanadium concentration of the vanadium electrolyte is 30-140 g / L, for example, 30 g / L, 40 g / L, 60 g / L, 80 g / L, 100 g / L, 120 g / L or 140 g / L, etc., but is not limited to the listed values, and other values not listed in the range are also applicable.

[0060] ​Preferably, the molar ratio of vanadium (III) to vanadium (IV) in the vanadium electrolyte is (0.8-1.2):1, such as 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0061] In a third aspect, the present application also provides a vanadium electrolyte as described in the second aspect, and the application includes the use of the vanadium electrolyte in a vanadium redox flow battery or other industrial fields requiring vanadium (III) and vanadium (IV) solutions.

[0062] Compared with the prior art, the present application has the following beneficial effects:

[0063] (1) The present application can reduce intermediate side reactions and increase the content of low-valence vanadium by combining ultraviolet light irradiation after or at the same time as electrolytic reduction, and can effectively remove impurity ions by combining extraction and stripping, thereby ensuring high recovery of vanadium.

[0064] (2) The preparation method of the present application reduces the use amount of traditional chemical reducing agents (such as sulfur dioxide or sulfites, etc.) or can be used moderately according to the need, and is more environmentally friendly; the preparation process produces less by-products, and the solvent and extractant can be recycled.

[0065] (3) The present application integrates mixing, electrolysis, ultraviolet light irradiation and extraction and stripping into the same preparation process, simplifies the complex operation of traditional multi-step chemical reduction and purification, and makes industrial continuous production more feasible.

[0066] (4) The present application can use various vanadium (V) compounds as raw materials, and the prepared vanadium electrolyte can be directly used in a vanadium redox flow battery or other industrial fields requiring low-valence vanadium electrolyte. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 is a schematic flow diagram of the preparation method of the vanadium electrolyte provided in Example 1. DETAILED DESCRIPTION

[0068] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the terms "include" and "have" and any variations thereof used in the specification and claims of the present application and the above description of drawings are intended to cover the non-exclusive inclusion.

[0070] Example 1

[0071] The present embodiment provides a preparation method of vanadium electrolyte, the final total vanadium concentration of which reaches 38.9 g / L, wherein the concentration of V 4+ is 27.5 g / L, and the concentration of V 3+ is 11.4 g / L. The preparation process is shown in the following, first, a compound containing pentavalent vanadium is mixed with a sulfuric acid solution, and then the mixed solution is subjected to electrolytic reduction, ultraviolet light irradiation and extraction-back extraction in sequence to obtain the vanadium electrolyte, specifically as follows: Figure 1

[0072] (1) 5 L of pentavalent vanadium leaching solution (V 5+ ) with a concentration of 20 g / L is mixed with 2 L of sulfuric acid solution with a concentration of 1.5 mol / L, so that the concentration of sulfuric acid in the system is about 1.0 mol / L, and the total volume of the liquid is 7 L. The pentavalent vanadium is fully and stably dissolved by stirring at 60°C and a stirring speed of 200 rpm for 2 h on an electromagnetic stirrer, to obtain a pentavalent vanadium solution with an initial vanadium concentration of 14 g / L to 15 g / L.

[0073] (2) A double-chamber electrolytic cell made of polypropylene (PP) is selected, the cathode zone and the anode zone are separated by a Nafion membrane, a carbon felt electrode with a thickness of 3 mm is selected as the cathode, and a titanium-based iridium tantalum oxide coating electrode is selected as the anode, the pentavalent vanadium solution obtained in step (1) is placed in the cathode zone and stirred at a stirring speed of 150 rpm, and a sulfuric acid solution with a concentration of 1.0 mol / L is placed in the anode zone, then the pentavalent vanadium solution obtained in step (1) is electrolyzed under the conditions of an electric current density of 80 mA / cm 2 and an electrolysis temperature of 50°C for 4 h to obtain a first vanadium ion solution.

[0074] After the electrolysis is completed, a low-pressure mercury lamp with a quartz sleeve with a power of 40 W and a main peak wavelength of 254 nm is used to continuously irradiate the vanadium solution at 50°C for 30 min above the cathode zone to obtain a second vanadium ion solution.

[0075] (3) P204 and kerosene are mixed in a volume ratio of 1:9 to serve as an extraction liquid, and the second vanadium ion solution obtained in step (2) is subjected to extraction for 10 min at 30°C and under stirring conditions according to a volume ratio of the extraction liquid to the second vanadium ion solution of 2:1; then the extracted organic material liquid is subjected to back extraction for 10 min at 30°C and under stirring conditions according to a volume ratio of the extracted organic material liquid to a 2.0 mol / L sulfuric acid solution of 1:1 to obtain the vanadium electrolyte.

[0076] Example 2

[0077] ​The embodiment provides a preparation method of a vanadium electrolyte, and the final total vanadium concentration of the vanadium electrolyte reaches 82.6 g / L, wherein the concentration of V 4+ is 74.3 g / L, and the concentration of V 3+ is 8.3 g / L. The preparation process comprises the following steps:

[0078] (1) 1.2 kg of sodium metavanadate (NaVO3) with a purity of 98% is slowly added into 4 L of a sulfuric acid solution with a concentration of 1.0 mol / L, and stirring is carried out at 40 ℃ and 300 rpm for 1 h, during which water or acid is appropriately supplemented, and the total volume of the solution is kept as 7.5 L.

[0079] (2) A double-chamber electrolytic cell made of polyvinylidene fluoride (PVDF) is selected, the cathode region and the anode region are separated by a Nafion membrane, a coated titanium electrode is selected as the cathode, and a titanium-based iridium tantalum oxide coated electrode is selected as the anode, the pentavalent vanadium solution obtained in the step (1) is placed in the cathode region and stirred at a rotating speed of 200 rpm, and a sulfuric acid solution with a concentration of 1.0 mol / L is placed in the anode region, then, the pentavalent vanadium solution obtained in the step (1) is electrolyzed for 3 h under the condition that the current density is 20 mA / cm 2 and the electrolysis temperature is 40 ℃, and a first vanadium ion solution is obtained.

[0080] After the electrolysis is completed, the first vanadium ion solution is introduced into a reactor equipped with an immersed ultraviolet lamp, a vacuum ultraviolet (VUV) lamp with a composite light output of wavelengths of 185 nm and 254 nm is selected, and the first vanadium ion solution is continuously irradiated for 20 min at 50 ℃, and a second vanadium ion solution is obtained.

[0081] (3) P507 and kerosene are mixed according to a volume ratio of 15:85 to serve as an extraction solution, and the second vanadium ion solution is extracted for 10 min under the condition that the solution is stirred at 25 ℃ according to a volume ratio of the extraction solution to the second vanadium ion solution of 0.9:1; then, the organic material liquid after extraction is back-extracted for 10 min under the condition that the solution is stirred at 25 ℃ according to a volume ratio of the organic material liquid after extraction to a 1.5 mol / L sulfuric acid solution of 1:1, and a vanadium electrolyte is obtained.

[0082] Embodiment 3

[0083] The embodiment provides a preparation method of a vanadium electrolyte, and the final total vanadium concentration of the vanadium electrolyte reaches 117.5 g / L, wherein the concentration of V 4+ is 105.7 g / L, and the concentration of V 3+ is 11.8 g / L. The preparation process comprises the following steps:

[0084] (1) Take 2.5 kg of ammonium metavanadate (NH4VO3) with a purity of 99%, slowly add the above NH4VO3 to 4 L of sulfuric acid solution with a concentration of 5.0 mol / L, and stir at a speed of 500 rpm at 90°C for 1 h, during which water or acid is appropriately added to maintain the total volume of the solution at 10 L.

[0085] (2) Select a double-chamber electrolytic cell made of polytetrafluoroethylene (PTFE), separate the cathode region from the anode region by a PBI-type cation membrane, use carbon paper as the cathode and a ruthenium-iridium oxide-coated titanium electrode as the anode, place the pentavalent vanadium solution obtained in step (1) in the cathode region and stir at a speed of 300 rpm, and place a sulfuric acid solution with a concentration of 1.0 mol / L in the anode region. Then, under the conditions of a current density of 200 mA / cm 2 , and an electrolysis temperature of 90°C, electrolyze the pentavalent vanadium solution obtained in step (1) for 5 h to obtain a first vanadium ion solution.

[0086] After the electrolysis is completed, introduce the first vanadium ion solution into a reactor equipped with an immersed low-pressure mercury lamp, select an immersed low-pressure mercury lamp with a wavelength of 254 nm, and continuously irradiate the first vanadium ion solution at 40°C for 60 min to obtain a second vanadium ion solution.

[0087] (3) Mix TBP, isooctanol, and kerosene in a volume ratio of 10:2:88 to obtain an extraction solution, and extract the second vanadium ion solution obtained in step (2) for 8 min at 40°C under stirring at a volume ratio of the extraction solution to the second vanadium ion solution of 4:1; then, back-extract the extracted organic solution for 10 min at 40°C under stirring at a volume ratio of the extracted organic solution to a 2.0 mol / L sulfuric acid solution of 1.1:1 to obtain a vanadium electrolyte.

[0088] Example 4

[0089] The difference between this example and Example 1 is that, in step (2) of this example, ultraviolet light irradiation is performed simultaneously with the electrolysis to obtain a first vanadium ion solution, and in step (3), the first vanadium ion solution is subjected to extraction-back extraction.

[0090] The remaining preparation methods and parameters are consistent with those of Example 1.

[0091] Example 5

[0092] The difference between this example and Example 1 is that, in step (2) of this example, the current density is 10 mA / cm 2 .

[0093] The remaining preparation methods and parameters are consistent with those of Example 1.

[0094] Example 6

[0095] The difference between this example and Example 1 is that in step (2) of this example, the current density is 300 mA / cm 2 ;

[0096] The rest of the preparation method and parameters are consistent with Example 1.

[0097] Example 7

[0098] The difference between this example and Example 1 is that in step (2) of this example, the temperature of electrolysis is 25℃;

[0099] The rest of the preparation method and parameters are consistent with Example 1.

[0100] Example 8

[0101] The difference between this example and Example 1 is that in step (2) of this example, the temperature of electrolysis is 95℃;

[0102] The rest of the preparation method and parameters are consistent with Example 1.

[0103] Example 9

[0104] The difference between this example and Example 1 is that in step (3) of this example, the volume ratio of the extraction solution to the second vanadium ion solution is 0.5:1;

[0105] The rest of the preparation method and parameters are consistent with Example 1.

[0106] Example 10

[0107] The difference between this example and Example 1 is that in step (3) of this example, the volume ratio of the extraction solution to the second vanadium ion solution is 5:1;

[0108] The rest of the preparation method and parameters are consistent with Example 1.

[0109] Comparative Example 1

[0110] The difference between this example and Example 1 is that in step (2) of this example, no ultraviolet light is applied after the electrolysis is completed;

[0111] The rest of the preparation method and parameters are consistent with Example 1.

[0112] Comparative Example 2

[0113] The difference between this example and Example 1 is that this example does not have step (3);

[0114] The rest of the preparation method and parameters are consistent with Example 1.

[0115] Performance test

[0116] The vanadium electrolyte prepared by examples 1-10 and comparative examples 1-2 was tested for total vanadium concentration and concentration of trivalent and tetravalent vanadium ions, and the results are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] As can be seen from the data of examples 1-4 and comparative examples 1-2 in Table 1, by using the preparation method of electrolytic reduction combined with ultraviolet irradiation and extraction-back extraction according to the present application, the content of vanadium ions in different valence states can be accurately controlled by adjusting the parameters in the electrolysis process only, the extraction-back extraction process significantly improves the recovery rate of vanadium, and the increase of ultraviolet irradiation can inhibit the change of valence state of vanadium ions and improve the stability of vanadium electrolyte; the synergistic effect of the three can not only avoid the use of traditional reducing agents and improve the production efficiency, but also effectively improve the recovery rate, purity and stability of the solution of vanadium, and realize the accurate control of the content of vanadium ions in different valence states, which can be widely applied to the industrial fields of all-vanadium redox flow batteries and other fields requiring trivalent and tetravalent vanadium solutions.

[0121] As can be seen from the comparison of the data of example 1 and examples 5-8 in Table 1, the current density and electrolysis temperature in the electrolytic reduction process will affect the total vanadium concentration and the content of vanadium ions in different valence states, when the current density is 20mA / cm 2 ~200mA / cm 2 and the electrolysis temperature is 40℃~90℃, it is not only more conducive to improving the recovery rate of vanadium, but also conducive to keeping the concentration of two kinds of valence state vanadium ions at a high level.

[0122] As can be seen from the comparison of the data of example 1 and examples 9-10 in Table 1, when the volume ratio of extractant to vanadium-containing solution is in the range of (1-4):1, it is more conducive to improving the separation efficiency of vanadium and impurity ions, thereby improving the recovery rate of vanadium.

[0123] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, which falls within the protection scope and disclosure scope of the present application.

Claims

1. A method of preparing a vanadium electrolyte, characterized in that, The method comprises: (1) mixing a compound containing pentavalent vanadium and a sulfuric acid solution to obtain a pentavalent vanadium solution; (2) electrolytic reduction of the pentavalent vanadium solution in step (1) to obtain a first vanadium ion solution; During the electrolytic reduction, the pentavalent vanadium solution in the electrolytic reduction process is subjected to first ultraviolet light irradiation; or, after the electrolytic reduction is completed, the first vanadium ion solution is subjected to second ultraviolet light irradiation to obtain a second vanadium ion solution; The current density of the electrolytic reduction is 20 mA / cm2~200 mA / cm2, and the temperature is 40℃~90℃; the wavelength of the first ultraviolet light irradiation and the wavelength of the second ultraviolet light irradiation are each independently 100 nm~280 nm; (3) extraction and back extraction of the first vanadium ion solution or the second vanadium ion solution in step (2) to obtain the vanadium electrolyte; The extraction liquid of the extraction comprises an extractant and a solvent, the extractant comprises an organic phosphate, the organic phosphate comprises any one or a combination of at least two of P204, P507 or TBP; the volume percentage of the extractant in the extraction liquid is 5%~20% based on 100% of the volume fraction of the extraction liquid; the volume ratio of the extraction liquid to the first vanadium ion solution or the volume ratio of the extraction liquid to the second vanadium ion solution is each independently (1~4):

1.

2. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and then adding the additive. The concentration of the sulfuric acid solution in step (1) is 1 mol / L~5 mol / L.

3. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and then adding the additive. The mixing method in step (1) comprises stirring.

4. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and then adding the additive. The temperature of the mixing in step (1) is 40℃~90℃.

5. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The electrolytic reduction in step (2) is carried out in an electrolytic cell, and the electrolytic cell comprises a cathode region, an anode region and a diaphragm for dividing the cathode region and the anode region.

6. The method of claim 5, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The cathode region comprises the pentavalent vanadium solution in step (1), and the anode region comprises a sulfuric acid solution.

7. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and then adding the additive. The time of the electrolytic reduction in step (2) is 3h~5h.

8. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The electrolytic reduction in step (2) is carried out under stirring.

9. The method of claim 1, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The time of the first ultraviolet light irradiation in step (2) and the time of the second ultraviolet light irradiation in step (2) are each independently 20min~60min.

10. The method of claim 5, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The first ultraviolet light irradiation in step (2) and the second ultraviolet light irradiation in step (2) are each independently carried out in the cathode region of the electrolytic cell or a separate ultraviolet irradiation reactor.

11. The method of claim 1, wherein the vanadium electrolyte is prepared by, The temperature of the extraction in step (3) is 25℃~40℃.

12. The method of claim 1, wherein the vanadium electrolyte is prepared by, The extraction in step (3) is carried out under stirring.

13. The method of claim 1, wherein the vanadium electrolyte is prepared by, The back extraction liquid of the back extraction in step (3) comprises a sulfuric acid solution.

14. The method of claim 13, wherein the vanadium electrolyte is prepared by adding the vanadium salt to the solvent and the additive. The concentration of the sulfuric acid solution is 1.5mol / L~2.0mol / L.

15. The method for preparing vanadium electrolyte according to claim 1, characterized in that, The volume ratio of the organic liquid to the back extraction liquid after the extraction in step (3) is (0.9~1.1):

1.

16. The method of claim 1, wherein the vanadium electrolyte is prepared by, The method comprises the following steps: (1) mixing a compound containing pentavalent vanadium and a sulfuric acid solution with a concentration of 1 mol / L~5 mol / L under stirring at 40℃~90℃ to obtain a pentavalent vanadium solution; (2) separating the cathode region and the anode region of the electrolytic cell by a diaphragm, placing the pentavalent vanadium solution of step (1) in the cathode region of the electrolytic cell and placing the sulfuric acid solution in the anode region of the electrolytic cell, and then electrolytically reducing the pentavalent vanadium solution of step (1) under stirring at a current density of 20 mA / cm2~200 mA / cm2and a temperature of 40℃~90℃ to obtain a first vanadium ion solution; after the electrolytic reduction is completed, the first vanadium ion solution is subjected to a second ultraviolet light irradiation for 20 min~60 min using ultraviolet light with a wavelength of 100 nm~280 nm to obtain a second vanadium ion solution; (3) preparing an extraction liquid according to a volume ratio of 5%~20% of an extractant in the extraction liquid, and extracting the second vanadium ion solution at 25℃~40℃ and under stirring according to a volume ratio of the extraction liquid to the second vanadium ion solution (1~4):1; then, using a sulfuric acid solution with a concentration of 1.5 mol / L~2.0 mol / L as a back-extraction liquid and performing back-extraction according to a volume ratio of the organic liquid after the extraction to the back-extraction liquid (0.9~1.1):1 to obtain the vanadium electrolyte; The extractant of the extraction includes an organophosphate, and the organophosphate includes any one or a combination of at least two of P204, P507 or TBP.

17. A vanadium electrolyte prepared by the method of any one of claims 1-16.

18. The vanadium electrolyte of claim 17, wherein, In the vanadium electrolyte, the total vanadium concentration of the vanadium electrolyte is 30 g / L~140 g / L.

19. The vanadium electrolyte of claim 17, wherein, In the vanadium electrolyte, the molar ratio of trivalent vanadium to tetravalent vanadium is (0.8~1.2):

1.

20. Use of a vanadium electrolyte as claimed in any one of claims 17-19, characterized in that The application includes a full vanadium liquid flow battery or other industrial fields requiring trivalent and tetravalent vanadium solutions.

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