Vanadium electrolyte based on acid vanadium-rich solution and preparation method thereof

Abstract

The present application relates to a kind of vanadium electrolyte based on acidic vanadium-rich liquid and its preparation method.The technical scheme is: in acidic vanadium-rich liquid, ammonium sulfate or ammonia is added, low-temperature ammonium alum crystallization is carried out to remove aluminum, and clear liquid is obtained after solid-liquid separation;After adding reducing agent to the clear liquid, the pH value is adjusted to 0.5-1.5, and the original liquid is obtained;The original liquid is extracted with saponified organic phosphonic acid extractant, and the loaded organic phase is washed with dilute acid and then back-extracted with sulfuric acid;The back-extracted liquid obtained by back-extraction is deoiled to obtain vanadium electrolyte.The present application has low preparation cost, is environment-friendly, has low extraction pH value and wide technical adaptability, the prepared vanadium electrolyte product has high concentration and high battery efficiency, effectively realizes the separation of impurities and the enrichment of vanadium in acidic vanadium-rich liquid.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of vanadium electrolyte, and particularly relates to a vanadium electrolyte based on an acid vanadium-rich solution and a preparation method thereof. BACKGROUND

[0002] As a large-scale energy storage technology with great potential, the all-vanadium redox flow battery has the advantages of cleanliness, high efficiency, safety, long service life, etc., and is increasingly applied. The vanadium electrolyte determines the energy density and battery performance of the vanadium battery, and the high purity requirement leads to a complex preparation process and high cost, which limits the promotion of the vanadium battery. At present, the mainstream process for preparing the vanadium electrolyte is to use high-purity solid vanadium pentoxide as a raw material, and to reduce V2O5 to be dissolved in sulfuric acid by using chemical reducing agents such as SO2, oxalic acid, V2O3 or by electrolysis, but the high-purity vanadium pentoxide leads to high preparation cost.

[0003] As an important vanadium source in China, the mainstream vanadium extraction process of vanadium shale directly leaches the acid vanadium-rich solution, which is mainly V(IV) and is accompanied by the leaching and enrichment of impurities such as iron and aluminum, and has the characteristics of high vanadium and many impurities, which brings the problems of deep impurity removal and enrichment for the subsequent preparation of the vanadium electrolyte. The preparation of high-purity V2O5 from the acid vanadium-rich solution needs to go through the steps of oxidation, vanadium precipitation, impurity removal by alkali dissolution, re-vanadium precipitation and calcination, and produces wastewater and waste gas during the process, which is not suitable for large-scale use of the vanadium battery due to the long production process.

[0004] The patent technology "Method for preparing vanadium oxide by low-concentration acid vanadium solution extraction" (CN112575207A) uses low-concentration acid vanadium solution (V2O5 content of 1-10 g / L) to obtain high-purity vanadium oxide product through the process of reduction-extraction-reverse extraction-vanadium precipitation-calcination. The patent technology "Method for extracting vanadium from stone coal vanadium ore leaching solution" (CN102560115A) uses stone coal vanadium ore oxidation leaching solution (vanadium content of 1.5-8.0 g / L) to obtain pure vanadium-containing solution through the process of reduction-extraction-reverse extraction. In summary, the current conventional extraction technology is only suitable for the extraction of low-concentration vanadium-containing solution, and has poor adaptability to raw materials, which is difficult to meet the efficient recovery and impurity separation of vanadium in the vanadium-rich solution.

[0005] The patent technology "Preparation method of electrolyte for all-vanadium redox flow battery" (CN112467185A) mixes vanadium pentoxide and vanadium trioxide, adds concentrated sulfuric acid, and calcines in a tube furnace to be dissolved in a sulfuric acid solution to prepare the vanadium electrolyte. Although this process has high purity and simple process, it has the problem of high preparation cost.

[0006] The patent technology "Preparation method of vanadyl sulfate electrolyte prepared from vanadium slag" (CN114156515A) uses vanadium slag as raw material. After the sulfuric acid leaching solution of vanadium slag is extracted by P204 and back-extracted by sulfuric acid, ammonium chloride is added to precipitate vanadium. After multiple dissolution and filtration, high-purity ammonium metavanadate is refined, and then dehydrated vanadium pentoxide is mixed with dilute sulfuric acid to prepare vanadyl sulfate electrolyte. This process basically conforms to the current traditional process of preparing vanadium electrolyte from vanadium-containing solution, which is long, requires multiple oxidation-reduction and vanadium precipitation, consumes a lot of energy and reagents, causes serious pollution, and has high preparation cost.

[0007] The patent technology "Method for preparing high-purity electrolyte for vanadium battery from stone coal" (CN101126124B) uses vanadium-containing solution obtained by alkaline roasting and water leaching of stone coal to obtain vanadium electrolyte through impurity removal, reduction, vanadium precipitation and sulfuric acid dissolution. This technology still needs multiple reduction and oxidation precipitation and dissolution, which is complex, consumes a lot of reagents and energy, causes serious pollution, and has high cost.

[0008] The patent technology "Method for directly preparing vanadium electrolyte from stone coal vanadium ore" (CN112843786A) uses stone coal vanadium ore as raw material, and after aging for 20-28h with concentrated sulfuric acid, leaching, adding calcium and aluminum salts for precipitation and impurity removal, and two-stage extraction process for deep impurity removal, the impurities in the leaching solution are removed through three impurity separation processes of one precipitation and two extractions to prepare high-purity vanadium electrolyte. This process has long aging time, and the pH required for two-stage extraction is high, at 2.2-2.8, which causes large alkali consumption and vanadium loss.

[0009] The patent technology "Method for producing vanadyl sulfate battery electrolyte from vanadium-containing acid leaching solution" (CN113998735A) uses stone coal acid leaching solution or vanadium-containing acidic waste liquid to separate impurities through reduction-extraction-back extraction-extraction-back extraction to prepare high-purity vanadyl sulfate electrolyte. This process realizes purification and enrichment of vanadium electrolyte through two-stage extraction-back extraction, which avoids the intermediate vanadium precipitation step and reduces cost, but the extraction pH is high at 1.5-4.0, which is only suitable for low vanadium concentration solution below 10g / L, and the impurity aluminum has a large impact, and the raw material adaptability is poor.

[0010] The patent technology "Method for preparing vanadium battery electrolyte from acid-rich vanadium solution" (CN105161746A) uses acid phosphorus extractant to extract V 5+ from acid-rich vanadium solution after oxygen-rich roasting, and then directly prepares electrolyte for vanadium battery through reduction. This technology uses acid phosphorus extractant, which has weaker selectivity for V 5+ than V 4+ , to reduce V extraction by extraction impurity removal, but requires high raw material requirements and still needs reduction.

[0011] The patent technology "A method for preparing high-purity vanadium battery electrolyte based on extraction-stripping system" (CN103151549A) uses vanadium slag sodiumized roasting water leaching vanadium-containing leaching solution as raw material, uses organic phosphonic acid extractant for extraction; the organic phase obtained by extraction is stripped with sulfuric acid; the sulfuric acid phase obtained by stripping is directly reduced by SO2 gas reducing agent to obtain vanadium battery electrolyte. This process avoids the intermediate process of vanadium precipitation, shortens the process and saves cost, but has problems of poor raw material adaptability, environmental pollution, and low concentration of electrolyte product.

[0012] Guo Yun (Guo Yun. Research on the method of preparing high-purity vanadium products by microemulsion extraction of vanadium[D]. Chongqing University, 2021) uses industrial calcium leaching solution as raw material, based on trioctylmethylammonium chloride microemulsion extraction, H2SO4+H2SO3 reduction and stripping process to prepare high-purity VOSO4 solution as vanadium electrolyte, but the cost of extractant is high, the preparation is complex, and the concentration of vanadium electrolyte product is low.

[0013] In summary, the existing vanadium electrolyte preparation process has problems of high preparation cost, environmental pollution, high pH required for extraction, complex process, poor raw material adaptability, etc.; the vanadium electrolyte product has the problem of low concentration. SUMMARY

[0014] The present application aims to overcome the defects of the prior art and provide a method for preparing vanadium electrolyte based on acid-rich vanadium liquid, which is low in cost, environmentally friendly, low in pH required for extraction, simple in process and strong in raw material adaptability; the vanadium electrolyte based on acid-rich vanadium liquid prepared by the method has high concentration and good performance, and can effectively realize the separation of impurities and the enrichment of vanadium in acid-rich vanadium liquid.

[0015] To achieve the purpose, the technical solution adopted by the present application has the following specific steps:

[0016] Step one, pretreatment

[0017] First, add ammonium sulfate or ammonia water to the acid-rich vanadium liquid according to the molar ratio of ammonium ion to aluminum ion of (1-5) : 1, mix well, and stand at 5-15℃ for 2-12h, then solid-liquid separation to obtain clear liquid and aluminum ammonium sulfate crystals.

[0018] The acid-rich vanadium liquid has a pH value of -0.5-0.5, a V(IV) concentration of 8-78g / L, an Al concentration of ≤40g / L, a Fe concentration of ≤5g / L, a Mg concentration of ≤5g / L, a K concentration of ≤2g / L, a Mn concentration of ≤2g / L, a Mo concentration of ≤2g / L, and a Cr concentration of ≤2g / L.

[0019] According to a molar ratio of sulfite ions to iron ions of (1.5-3):1, sodium sulfite is added to the supernatant, and stirring is performed at 50-80°C and a rotation speed of 2-10 r / min for 10-30 min to obtain a reduced liquid.

[0020] Then, calcium hydroxide or sodium hydroxide is added to the reduced liquid, and the pH is adjusted to 0.5-1.5, followed by solid-liquid separation to obtain a leaching liquid and a pH-adjusted residue.

[0021] Step two, extraction

[0022] According to a volume ratio of the organic phase to the leaching liquid of (1-4):1, the organic phase is mixed with the leaching liquid, and countercurrent normal extraction is performed at 10-30°C for 6-10 min, followed by phase separation to obtain a raffinate and a loaded organic phase.

[0023] The organic phase is a mixture obtained by mixing 15-30 vol% of a vanadium extractant and 70-85 vol% of sulfonated kerosene, and then saponifying the mixture with a saponifying agent, and the saponification degree is 40-80%.

[0024] Step three, washing

[0025] According to a volume ratio of the loaded organic phase to the washing agent of (1-5):1, the loaded organic phase is mixed with the washing agent, and stirring is performed at 10-30°C for 10-30 min, followed by phase separation to obtain washing water and a washed loaded organic phase.

[0026] Step four, stripping

[0027] According to a volume ratio of the washed loaded organic phase to the stripping agent of (4-10):1, the washed loaded organic phase is mixed with the stripping agent, and multistage countercurrent stripping is performed at 10-30°C for 20-60 min, followed by phase separation to obtain a stripping liquid and a lean organic phase.

[0028] Step five, oil removal

[0029] The stripping liquid is subjected to oil removal treatment to obtain a vanadium electrolyte.

[0030] The vanadium electrolyte has a V(IV) concentration of 76.50-153.00 g / L, a K concentration of ≤30 mg / L, a Mo concentration of ≤10 mg / L, and a Cr concentration of ≤10 mg / L.

[0031] The vanadium extractant is one or more of di(2-ethylhexyl) phosphonate and 2-ethylhexyl phosphonic acid mono(2-ethylhexyl) ester.

[0032] The saponifying agent is one of sodium hydroxide solution and ammonia water.

[0033] The washing agent is one of 0.01-0.2 mol / L dilute sulfuric acid and dilute hydrochloric acid.

[0034] The back-extracting agent is a 2.3-6 mol / L sulfuric acid solution.

[0035] The oil removal treatment is carried out by one or more than one of the following modes: clarification in a clarifier, adsorption in a resin floatation column and adsorption in activated carbon.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] 1. The process flow is short, clean and efficient, environmentally friendly, and the consumption of reagents and energy consumption are low, and the preparation cost is low

[0038] The present application uses vanadium-rich liquid as raw material, avoiding the complex process of the prior art "oxidation-vanadium precipitation-alkali dissolution-vanadium precipitation-calcination-reduction in sulfuric acid", and only through "pretreatment-extraction-washing-back extraction" to realize the preparation of vanadium electrolyte based on acid vanadium-rich liquid, and the preparation cost can be reduced by more than 30%. Therefore, the present application has short process, low preparation cost, less reagent consumption, small energy consumption, clean and efficient and environmentally friendly.

[0039] 2. The initial pH required for extraction is low, reducing the alkali consumption and vanadium loss caused by pH adjustment

[0040] The initial pH required for the existing extraction solution is 1.8-2.0, and even 2.6 for extraction of high-concentration vanadium solution, which not only causes a large amount of alkali consumption and vanadium loss, but also is not conducive to impurity separation; the present application uses organic phase saponification to reduce the initial pH to 0.5-1.5, reducing the pH adjustment range of the acid vanadium-rich liquid, reducing the alkali consumption and vanadium loss caused by pH adjustment, and the pH required for extraction is low.

[0041] 3. The present application has good impurity separation effect, high vanadium recovery rate and strong raw material adaptability

[0042] (1) The present application uses low-temperature ammonium alum crystallization for the acid vanadium-rich liquid before extraction, the reaction is shown in formula (1), which can remove more than 60% of aluminum ions in the vanadium-rich liquid, reducing the pressure of aluminum removal in subsequent extraction and the emulsification phenomenon caused by aluminum in the extraction process. Therefore, the present application can realize effective separation of impurity aluminum, and has good separation effect.

[0043] 12H2O+Al 3+ +2SO4 2- +NH4 + →(NH4)Al(SO4)2·12H2O (1)

[0044] (2)Fe 3+ , VO 2+ , Fe 2+Through cation exchange mechanism and the reaction of extractant, the reaction is shown as formula (2), (3), (4), and in the actual extraction process, VO 2+ Competes with Fe 2+ The reaction is shown as formula (5). In the intense stirring of extraction, Fe 2+ Is gradually oxidized to Fe 3+ And competes with VO 2+ And Fe 2+ The reaction is shown as formula (6) and (7), so that the impurity iron enters the organic phase in the form of Fe 3+ In large quantities, and further affects the purity of vanadium electrolyte product. And the addition of reducing agent sodium sulfite can effectively reduce the oxidation of Fe 2+ To Fe 3+ In the extraction process, and improve the separation effect of vanadium and iron. The main reaction of iron ion reduction of vanadium-rich liquid by using sulfurous acid is shown as formula (8). Therefore, the present application can realize the effective separation of impurity iron, and has high purity.

[0045] Fe 3+ (aq) +3(HA) 2(o) →FeA3·3HA (o) +3H + (aq) (2)

[0046] VO 2+ (aq) +2(H4) 2(o )→VOA2·2HA (o) +2H + (aq) (3)

[0047] Fe 2+ (aq) +2(HA) 2(o) →FeA2·2HA (o) +2H + (aq) (4)

[0048] VO 2+ (aq) +FeA2·2HA (o) →VOA2·2HA (o) +2Fe 2+ (aq) (5)

[0049] 2Fe 3+ (aq) +3VOA2·2HA (o) →2FeA3·3HA (o) +3VO 2+ (aq)(6)

[0050] 2Fe 3+ (aq) +3FeA2·2H4 (o) →2FeA3·3HA (o) +3Fe 2+ (aq (7)

[0051] Fe 3+ +SO3 2- +H₂O→SO₄ 2- +Fe 2+ +2OH - (8)

[0052] (3) The vanadium concentration in acidic vanadium-rich solutions is usually greater than 10 g / L, or even above 50 g / L; existing VO 2+ The extraction reaction is shown in formula (9). During the reaction, a large number of hydrogen ions are exchanged, and the pH of the solution drops sharply, making it difficult for the reaction to continue and resulting in a low vanadium extraction rate. Therefore, this invention uses saponification to convert the extractant into sodium (ammonium) salt. The extraction reaction is shown in formulas (10) and (11). The pH of the solution can be controlled during the extraction process, allowing the extraction reaction to proceed smoothly to the right and resulting in a high vanadium recovery rate. Therefore, this invention can be applied to raw materials with a vanadium concentration of 10 to 76.5 g / L, and has wide applicability.

[0053]

[0054]

[0055]

[0056] 4. The vanadium electrolyte prepared by this invention has high concentration, high purity, and good performance.

[0057] Existing chemical reduction processes are limited by the low solubility of vanadium pentoxide in sulfuric acid. High-temperature activation followed by the addition of a reducing agent converts it into tetravalent vanadium, resulting in a limited concentration of vanadium electrolyte products. In contrast, this invention adjusts the vanadium concentration of the electrolyte from 76.50 to 153.00 g / L by adjusting the loaded organic phase compared to the stripping agent. Therefore, the vanadium concentration range of the electrolyte is wide and easy to adjust, resulting in high product concentration and high charge / discharge capacity.

[0058] The impurities of this invention are removed through pretreatment and deeply separated through extraction, washing, and back-extraction. Furthermore, the use of sulfuric acid solution for back-extraction does not introduce impurities, effectively achieving impurity separation and vanadium enrichment in acidic vanadium-rich solutions. This reduces side reactions such as oxygen and hydrogen evolution in impurity redox reactions, resulting in good reversibility and high energy efficiency in vanadium battery operation.

[0059] The removal rate of aluminum in the low-temperature crystallization aluminum removal process is 69.44-81.4%; the vanadium extraction rate is 97.55-98.65%; and the total vanadium recovery rate is 96.86-98.45%.

[0060] The vanadium electrolyte based on the acid vanadium-rich liquid meets the requirements of the national standard (GB / T-37204-2018) and has high purity, wherein the V concentration is 81.91-150.87 g / L, the K concentration is ≤30 mg / L, the Mo concentration is ≤10 mg / L, and the Cr concentration is ≤10 mg / L, which is higher than the requirements of the national standard.

[0061] The vanadium electrolyte based on the acid vanadium-rich liquid is used for 50-cycle battery cycle charge-discharge test at a current density of 40 mA / cm 2 The average coulombic efficiency is 89.3-92.45%, the voltage efficiency is 92.41-93.44%, and the energy efficiency is 82.59-86.14%.

[0062] Therefore, the application has the characteristics of low cost, environmental friendliness, low pH required for extraction, simple process, and strong adaptability of raw materials, and the prepared vanadium electrolyte based on the acid vanadium-rich liquid has high concentration, high purity, and good performance, effectively realizing the separation of impurities and the enrichment of vanadium in the acid vanadium-rich liquid. DETAILED DESCRIPTION

[0063] The application will be further described below in conjunction with the specific embodiments, which are not limitations on the protection scope.

[0064] A vanadium electrolyte based on an acid vanadium-rich liquid and a preparation method thereof. The specific steps of the preparation method in the specific embodiment are as follows:

[0065] Step 1, pretreatment

[0066] First, ammonium sulfate or ammonia water is added to the acid vanadium-rich liquid according to the molar ratio of ammonium ions to aluminum ions of (1-5):1, and mixed uniformly, and then the mixture is statically placed at 5-15°C for 2-12 h, and then solid-liquid separation is performed to obtain a clear liquid and aluminum ammonium sulfate crystals.

[0067] The acid vanadium-rich liquid has a pH value of -0.5-0.5, a V(IV) concentration of 8-78 g / L, an Al concentration of ≤40 g / L, an Fe concentration of ≤5 g / L, a Mg concentration of ≤5 g / L, a K concentration of ≤2 g / L, a Mn concentration of ≤2 g / L, a Mo concentration of ≤2 g / L, and a Cr concentration of ≤2 g / L.

[0068] Then, sodium sulfite is added to the clear liquid according to the molar ratio of sulfite ions to iron ions of (1.5-3):1, and the mixture is stirred at 50-80°C and a rotation speed of 2-10 r / min for 10-30 min to obtain a reduced liquid.

[0069] Then, calcium hydroxide or sodium hydroxide is added to the reduced solution, the pH is adjusted to 0.5-1.5, and solid-liquid separation is performed to obtain a raffinate and a pH-adjusted residue.

[0070] Step two, extraction

[0071] The organic phase is mixed with the raffinate according to a volume ratio of the organic phase to the raffinate of (1-4) : 1, countercurrent normal extraction is performed at 10-30°C for 6-10 min, and phase separation is performed to obtain a raffinate and a loaded organic phase.

[0072] The organic phase is a mixture obtained by mixing 15-30 vol% of a vanadium extractant and 70-85 vol% of sulfonated kerosene, and then saponifying the mixture with a saponifying agent, and the saponification degree is 40-80%.

[0073] Step three, washing

[0074] The loaded organic phase is mixed with a washing agent according to a volume ratio of the loaded organic phase to the washing agent of (1-5) : 1, stirring is performed at 10-30°C for 10-30 min, and phase separation is performed to obtain washing water and a washed loaded organic phase.

[0075] Step four, stripping

[0076] The washed loaded organic phase is mixed with a stripping agent according to a volume ratio of the washed loaded organic phase to the stripping agent of (4-10) : 1, multistage countercurrent stripping is performed at 10-30°C for 20-60 min, and phase separation is performed to obtain a stripping solution and a lean organic phase.

[0077] Step five, oil removal

[0078] The stripping solution is subjected to oil removal treatment to obtain a vanadium electrolyte.

[0079] The vanadium electrolyte has a V(IV) concentration of 76.50-153.00 g / L, a K concentration of ≤30 mg / L, a Mo concentration of ≤10 mg / L, and a Cr concentration of ≤10 mg / L.

[0080] The vanadium extractant is one or more of di(2-ethylhexyl) phosphonate and 2-ethylhexyl phosphonic acid mono(2-ethylhexyl) ester.

[0081] The saponifying agent is one of sodium hydroxide solution and ammonia water.

[0082] The washing agent is one of 0.01-0.2 mol / L dilute sulfuric acid and dilute hydrochloric acid.

[0083] The stripping agent is a 2.3-6 mol / L sulfuric acid solution.

[0084] The oil removal treatment is carried out by one or more of the following methods: clarification tank clarification, resin flotation column adsorption, and activated carbon adsorption.

[0085] Example 1

[0086] A vanadium electrolyte based on an acid vanadium-rich solution and a preparation method thereof. The specific steps of the preparation method described in the embodiment are as follows:

[0087] Step one, pretreatment

[0088] First, ammonia water is added to the acid vanadium-rich solution according to a molar ratio of ammonium ions to aluminum ions of 1:1, mixed, and allowed to stand at 5°C for 12 hours, and then solid-liquid separation is performed to obtain a clear solution and aluminum ammonium sulfate crystals.

[0089] The acid vanadium-rich solution has a pH of -0.46, V(IV) of 8.32 g / L, Al of 3.80 g / L, Fe of 0.69 g / L, Mg of 1.78 g / L, K of 1.26 g / L, Mn of 0.87 g / L, Mo of 0.06 g / L, and Cr of 0.05 g / L.

[0090] Then, sodium sulfite is added to the clear solution according to a molar ratio of sulfite ions to iron ions of 1.5:1, and stirring is performed at 50°C and a rotation speed of 2 r / min for 10 minutes to obtain a reduced solution.

[0091] Then, calcium hydroxide is added to the reduced solution to adjust the pH to 0.5, and solid-liquid separation is performed to obtain a raw extraction solution and a pH adjustment residue.

[0092] Step two, extraction

[0093] The organic phase is mixed with the raw extraction solution according to a volume ratio of the organic phase to the raw extraction solution of 1:1, countercurrent normal extraction is performed at 10°C for 6 minutes, and phase separation is performed to obtain a raffinate and a loaded organic phase.

[0094] The organic phase is a mixture obtained by mixing 15 vol% of a vanadium extractant and 85 vol% of sulfonated kerosene, and then saponifying the mixture with a saponifying agent, and the saponification degree is 40%.

[0095] Step three, washing

[0096] The loaded organic phase is mixed with a washing agent according to a volume ratio of the loaded organic phase to the washing agent of 1:1, stirring is performed at 10°C for 10 minutes, and phase separation is performed to obtain wash water and a washed loaded organic phase.

[0097] Step four, stripping

[0098] The volume ratio of the loaded organic phase after washing to the stripping agent is 10:1, the loaded organic phase after washing is mixed with the stripping agent, multi-stage countercurrent stripping is carried out at 10°C, the multi-stage countercurrent stripping time is 20 min, and the phases are separated to obtain a stripping solution and a poor organic phase.

[0099] Step five, oil removal

[0100] The stripping solution is subjected to oil removal treatment to obtain a vanadium electrolyte. The oil removal treatment is carried out by using a clarifier.

[0101] In this embodiment:

[0102] The vanadium extractant is 2-ethylhexyl phosphonic acid mono(2-ethylhexyl) ester.

[0103] The saponifying agent is ammonia water.

[0104] The washing agent is 0.01 mol / L dilute sulfuric acid.

[0105] The stripping agent is a 2.3 mol / L sulfuric acid solution.

[0106] The relevant parameters and indicators in this embodiment are determined: the removal rate of aluminum in the low-temperature crystallization aluminum removal process is 75.46%; the vanadium extraction rate is 98.65%; the total vanadium recovery rate is 98.45%; and the pH value only needs to be adjusted to 0.5.

[0107] The vanadium electrolyte based on the acid-rich vanadium liquid prepared in this embodiment is determined to have: V(IV) of 81.91 g / L; Al of 23 mg / L; Fe of 29 mg / L; Mg of 26 mg / L; K of 12 mg / L; Mn of 2 mg / L; Mo of 2 mg / L; and Cr of 1 mg / L. The composition meets the requirements of the first-grade product of the 4-valence electrolyte in the national standard (GB / T-37204-2018).

[0108] The vanadium electrolyte based on the acid-rich vanadium liquid is used for 50 cycles of battery cycle charge-discharge test at a current density of 40 mA / cm 2 The average coulombic efficiency is 91.07%, the voltage efficiency is 93.44%, and the energy efficiency is 85.10%.

[0109] Example 2

[0110] A vanadium electrolyte based on an acid-rich vanadium liquid and a preparation method thereof. The specific steps of the preparation method in this embodiment are:

[0111] Step one, pretreatment

[0112] First, ammonium sulfate is added to the acid vanadium-rich solution in a molar ratio of 5:1 of ammonium ion to aluminum ion, mixed, and allowed to stand at 15℃ for 2h, and then solid-liquid separation is performed to obtain a clear solution and aluminum ammonium sulfate crystals.

[0113] The acid vanadium-rich solution has a pH of 0.42, V(IV) of 77.88g / L, Al of 34.5g / L, Fe of 4.97g / L, Mg of 3.78g / L, K of 1.26g / L, Mn of 1.07g / L, Mo of 0.64g / L, and Cr of 0.75g / L.

[0114] Sodium sulfite is added to the clear solution in a molar ratio of 3:1 of sulfite ion to iron ion, stirred at 80℃ and a rotation speed of 10r / min for 30min to obtain a reduced solution.

[0115] Then, sodium hydroxide is added to the reduced solution to adjust the pH to 1.5, and solid-liquid separation is performed to obtain a raffinate and a pH adjustment residue.

[0116] Step two, extraction

[0117] The organic phase is mixed with the raffinate in a volume ratio of 4:1 of the organic phase to the raffinate, and countercurrent forward extraction is performed at 30℃ for 10min, and then phase separation is performed to obtain a raffinate and a loaded organic phase.

[0118] The organic phase is a mixture obtained by mixing 30vol% of a vanadium extractant and 70vol% of sulfonated kerosene, and then saponifying the mixture with a saponifier to obtain a saponification degree of 80%.

[0119] Step three, washing

[0120] The loaded organic phase is mixed with a washing agent in a volume ratio of 5:1 of the loaded organic phase to the washing agent, stirred at 30℃ for 30min, and then phase separation is performed to obtain a washing water and a washed loaded organic phase.

[0121] Step four, stripping

[0122] The washed loaded organic phase is mixed with a stripping agent in a volume ratio of 8:1 of the washed loaded organic phase to the stripping agent, and multistage countercurrent stripping is performed at 30℃ for 60min, and then phase separation is performed to obtain a stripping solution and a lean organic phase.

[0123] Step five, oil removal

[0124] The stripping solution is subjected to oil removal treatment to obtain a vanadium electrolyte. The oil removal treatment is performed by using a resin flotation column for adsorption.

[0125] In this embodiment:

[0126] The vanadium extractant is di(2-ethylhexyl) phosphonate.

[0127] The saponifying agent is sodium hydroxide solution.

[0128] The washing agent is 0.2 mol / L dilute hydrochloric acid.

[0129] The stripping agent is 6 mol / L sulfuric acid solution.

[0130] The relevant parameters and indexes in this embodiment are determined: the removal rate of aluminum in the low-temperature crystallization aluminum removal process is 81.4%; the vanadium extraction rate is 97.55%; the total recovery rate of vanadium is 96.86%; and the pH value only needs to be adjusted to 1.5.

[0131] The vanadium electrolyte based on the acid-rich vanadium liquid prepared in this embodiment is determined: V(IV) is 150.87 g / L; Al is 42 mg / L; Fe is 35 mg / L; Mg is 19 mg / L; K is 28 mg / L; Mn is 6 mg / L; Mo is 4 mg / L; and Cr is 2 mg / L. The composition meets the requirements of the first-grade product of the 4-valence electrolyte in the national standard (GB / T-37204-2018).

[0132] The vanadium electrolyte based on the acid-rich vanadium liquid is used for 50-cycle battery cycle charge-discharge test at a current density of 40 mA / cm 2 The average coulombic efficiency is 89.37%; the voltage efficiency is 92.41%; and the energy efficiency is 82.59%.

[0133] Embodiment 3

[0134] A vanadium electrolyte based on an acid-rich vanadium liquid and a preparation method thereof. The specific steps of the method in this embodiment are:

[0135] Step 1, pretreatment

[0136] First, ammonium sulfate is added to the acid-rich vanadium liquid according to a molar ratio of ammonium ions to aluminum ions of 3:1, mixed uniformly, and then placed at 10°C for 8 hours, followed by solid-liquid separation to obtain a clear liquid and ammonium aluminum sulfate crystals.

[0137] The acid-rich vanadium liquid has a pH of 0.34, V(IV) of 53.90 g / L, Al of 21.2 g / L, Fe of 2.78 g / L, Mg of 0.30 g / L, K of 0.55 g / L, Mn of 0.04 g / L, Mo of 0.02 g / L, and Cr of 0.05 g / L.

[0138] Then, sodium sulfite is added to the clear liquid according to a molar ratio of sulfite ions to iron ions of 2:1, stirred at 60°C and a rotation speed of 5 r / min for 20 min, and a reduced liquid is obtained.

[0139] Then sodium hydroxide is added to the reduced solution, the pH is adjusted to 1.0, and solid-liquid separation is performed to obtain a raffinate and a pH-adjusted residue.

[0140] Step two, extraction

[0141] The organic phase and the raffinate are mixed according to a volume ratio of the organic phase to the raffinate of 2:1, countercurrent normal extraction is performed at 20°C for 8 min, and phase separation is performed to obtain a retentate and a loaded organic phase.

[0142] The organic phase is a mixture obtained by mixing 25 vol% of a vanadium extractant and 75 vol% of sulfonated kerosene, and then saponifying the mixture with a saponifying agent, with a saponification degree of 60%.

[0143] Step three, washing

[0144] The loaded organic phase and a washing agent are mixed according to a volume ratio of the loaded organic phase to the washing agent of 3:1, stirring is performed at 20°C for 20 min, and phase separation is performed to obtain a washing water and a washed loaded organic phase.

[0145] Step four, stripping

[0146] The washed loaded organic phase and a stripping agent are mixed according to a volume ratio of the washed loaded organic phase to the stripping agent of 4:1, multistage countercurrent stripping is performed at 20°C for 40 min, and phase separation is performed to obtain a stripping solution and a lean organic phase.

[0147] Step five, oil removal

[0148] The stripping solution is subjected to oil removal treatment to obtain a vanadium electrolyte. The oil removal treatment is performed by using activated carbon adsorption.

[0149] In this embodiment:

[0150] The vanadium extractant is a mixture of di(2-ethylhexyl) phosphonate and 2-ethylhexyl phosphonate mono(2-ethylhexyl) ester.

[0151] The saponifying agent is a sodium hydroxide solution.

[0152] The washing agent is dilute sulfuric acid with a concentration of 0.1 mol / L.

[0153] The stripping agent is a sulfuric acid solution with a concentration of 4 mol / L.

[0154] The relevant parameters and indexes in this embodiment are determined as follows: the removal rate of aluminum in the low-temperature crystallization aluminum removal process is 69.44%; the vanadium extraction rate is 98.06%; the total vanadium recovery rate is 97.48%; and the pH value only needs to be adjusted to 1.0.

[0155] The vanadium electrolyte prepared in this embodiment was measured to have V(IV) of 105.09 g / L; Al of 39 mg / L; Fe of 21 mg / L; Mg of 24 mg / L; K of 16 mg / L; Mn of 5 mg / L; Mo of 2 mg / L; and Cr of 2 mg / L. The components meet the requirements of the first-grade product of the 4-valence electrolyte in the national standard (GB / T-37204-2018).

[0156] The vanadium electrolyte was used to carry out 50 cycles of battery cycle charging and discharging tests at a current density of 40 mA / cm 2 Current density: The average coulombic efficiency was 92.45%; the voltage efficiency was 93.17%; and the energy efficiency was 86.14% in the 50 cycles of battery cycle charging and discharging tests.

[0157] Compared with the prior art, the specific embodiment has the following beneficial effects:

[0158] 1. The process flow is short, clean, efficient, environmentally friendly, and has low reagent consumption and energy consumption, and low preparation cost

[0159] The specific embodiment uses vanadium-rich liquid as raw material, avoids the complex process of the prior art “oxidation-vanadium precipitation-alkali dissolution-vanadium precipitation-calcination-reduction in sulfuric acid”, and only realizes the preparation of vanadium electrolyte based on acid vanadium-rich liquid through “pretreatment-extraction-washing-reverse extraction”, which can reduce the preparation cost by more than 30%. Therefore, the process flow is short, the preparation cost is low, the reagent consumption and energy consumption are low, it is clean and efficient, and it is environmentally friendly.

[0160] 2. The initial pH required for extraction is low, which reduces the alkali consumption and vanadium loss caused by pH adjustment

[0161] The initial pH required for the existing extraction solution is 1.8-2.0, and even 2.6 for extraction of high-concentration vanadium solution, which not only causes a large amount of alkali consumption and vanadium loss, but also is not conducive to impurity separation; the specific embodiment uses organic phase saponification to reduce the initial pH to 0.5-1.5, which reduces the pH adjustment range of the acid vanadium-rich liquid, reduces the alkali consumption and vanadium loss caused by pH adjustment, and reduces the pH required for extraction.

[0162] 3. The specific embodiment has good impurity separation effect, high vanadium recovery rate, and strong adaptability to raw materials

[0163] (1) The specific embodiment uses low-temperature ammonium alum crystallization before extraction of the acid vanadium-rich liquid, and the reaction is as shown in formula (1), which can remove more than 60% of aluminum ions in the vanadium-rich liquid, and reduce the subsequent extraction work of removing aluminum and the emulsification phenomenon caused by aluminum in the extraction process. Therefore, the specific embodiment can realize effective separation of impurities aluminum, and has good separation effect.

[0164] 12H2O + Al 3+ + 2SO4 2- + NH4+ → (NH4)Al(SO4)2·12H2O (1)

[0165] (2)Fe 3+ 、VO 2+ 、Fe 2+ Through the cation exchange mechanism and the reaction of extractant, the reaction is shown as formula (2), (3), (4), the actual extraction process VO 2+ and Fe 2+ compete extraction, the reaction is shown as formula (5). In the extraction of the intense stirring, Fe 2+ is gradually oxidized to Fe 3+ and competes with VO 2+ and Fe 2+ extraction, the reaction is shown as formula (6) and (7), so that the impurity iron in the form of Fe 3+ into the organic phase, and then affect the purity of vanadium electrolyte product. While using the addition of reducing agent sodium sulfite can effectively reduce the extraction process Fe 2+ oxidation to Fe 3+ , improve the separation effect of vanadium iron. Using sulfurous acid to reduce the iron ion of vanadium-rich liquid, the main reaction is shown as formula (8). Therefore, the embodiment can realize the effective separation of impurity iron, high purity.

[0166] Fe 3+ (aq) +3(HA) 2(o) →FeA3·3HA (o) +3H + (aq) (2)

[0167] VO 2+ (aq) +2(HA) 2(o) →VOA2·2HA (o) +2H + (aq) (3)

[0168] Fe 2+ (aq) +2(HA) 2(o) →FeA2·2HA (o) +2H + (aq) (4)

[0169] VO 2+ (aq) +FeA2·2HA (o) →VOA2·2HA (o) +2Fe 2+ (aq) (5)

[0170] 2Fe 3+ (aq) +3VOA2·2HA (o) →2FeA3·3HA (o) +3VO 2+ (aq) (6)

[0171] 2Fe 3+ (aq) +3FeA2·2HA (o) →2FeA3·3HA (o) +3Fe 2+ (aq) (7)

[0172] Fe 3+ +SO3 2- +H₂O→SO₄ 2- +Fe 2+ +2OH - (8)

[0173] (3) The vanadium concentration in acidic vanadium-rich solutions is usually greater than 10 g / L, or even above 50 g / L; existing VO 2+ The extraction reaction is shown in equation (9). During the reaction, a large number of hydrogen ions are exchanged, causing a sharp drop in the pH of the solution, making it difficult for the reaction to continue and resulting in a low vanadium extraction rate. Therefore, in this specific embodiment, saponification is used to convert the extractant into sodium (ammonium) salt. The extraction reaction is shown in equations (10) and (11). The pH of the solution is controllable during the extraction process, allowing the extraction reaction to proceed smoothly to the right, resulting in a high vanadium recovery rate. Therefore, this specific embodiment can be applied to raw materials with a vanadium concentration of 10–76.5 g / L, and has wide applicability.

[0174]

[0175]

[0176]

[0177] 4. The vanadium electrolyte prepared in this specific embodiment has high concentration, high purity, and good performance.

[0178] The existing chemical reduction method is limited by the low solubility of vanadium pentoxide in sulfuric acid. It requires high-temperature activation followed by the addition of a reducing agent to convert it into tetravalent vanadium, thus limiting the concentration of the vanadium electrolyte product. However, this specific embodiment adjusts the vanadium concentration of the electrolyte from 76.50 to 153.00 g / L by adjusting the loaded organic phase and the stripping agent. Therefore, the vanadium concentration range of the electrolyte is wide and easy to adjust, resulting in high product concentration and high charge / discharge capacity.

[0179] In this specific embodiment, impurities are removed through pretreatment and deeply separated through extraction, washing, and back-extraction. Furthermore, the use of sulfuric acid solution for back-extraction does not introduce impurities, effectively achieving impurity separation and vanadium enrichment in acidic vanadium-rich solutions. This reduces side reactions such as oxygen and hydrogen evolution in impurity redox reactions, resulting in good reversibility and high energy efficiency in vanadium battery operation.

[0180] The relevant parameters and indicators in this embodiment were measured as follows: the aluminum removal rate during the low-temperature crystallization process was 69.44-81.4%; the vanadium extraction rate was 97.55-98.65%; and the total vanadium recovery rate was 96.86-98.45%.

[0181] The vanadium electrolyte based on acidic vanadium-rich solution was tested and found to meet the requirements of the national standard (GB / T-37204-2018), exhibiting high purity. Specifically, the V concentration was 81.91–150.87 g / L, K concentration ≤30 mg / L, Mo concentration ≤10 mg / L, and Cr concentration ≤10 mg / L, exceeding the national standard requirements.

[0182] The vanadium electrolyte based on the acidic vanadium-rich solution was used at 40 mA / cm. 2 The battery was subjected to 50 cycles of charge-discharge testing at current density: the average coulombic efficiency was 89.3%–92.45%; the voltage efficiency was 92.41%–93.44%; and the energy efficiency was 82.59%–86.14%.

[0183] Therefore, this specific embodiment has the characteristics of low cost, environmental friendliness, low pH required for extraction, simple process and strong adaptability of raw materials. The prepared vanadium electrolyte based on acidic vanadium-rich solution has high concentration, high purity and good performance, effectively realizing the separation of impurities and enrichment of vanadium in acidic vanadium-rich solution.

Claims

1. A method for preparing a vanadium electrolyte based on an acidic vanadium-rich solution, characterized in that... The preparation method comprises the following steps: Step 1: Preprocessing First, add ammonium sulfate or ammonia water to the acidic vanadium-rich solution according to the molar ratio of ammonium ions to aluminum ions of (3~5):1, mix well, let stand for 2~12 hours at 5~15℃, and separate the solid and liquid to obtain clear liquid and ammonium aluminum sulfate crystals. The acidic vanadium-rich solution has the following characteristics: pH value -0.5~0.5, V(IV) concentration 53.90~78 g / L, Al concentration 21.2~40 g / L, Fe concentration 2.78~5 g / L, Mg concentration 0.30~5 g / L, K concentration 0.55~2 g / L, Mn concentration 0.04~2 g / L, Mo concentration 0.02~2 g / L, and Cr concentration 0.05~2 g / L. Sodium sulfite was added to the clear solution according to the molar ratio of sulfite ions to iron ions of (1.5~3):1, and the solution was stirred for 10~30 min at 50~80℃ and 2~10 r / min to obtain the reduced solution. Then, calcium hydroxide or sodium hydroxide is added to the reduced solution to adjust the pH to 1.0~1.5, and the solid and liquid are separated to obtain the original extraction solution and pH-adjusted residue. Step 2: Extraction According to the volume ratio of organic phase to the extraction solution of (1~4):1, the organic phase and the extraction solution are mixed and subjected to countercurrent extraction at 10~30℃ for 6~10 min. The phases are separated to obtain raffinate and loaded organic phase. The organic phase is a mixture obtained by mixing 15-30 vol% vanadium extractant and 70-85 vol% sulfonated kerosene and then saponifying it with a saponifying agent, with a saponification degree of 40-80%. Step 3: Washing According to the volume ratio of the supported organic phase to the detergent of (1~5):1, the supported organic phase is mixed with the detergent and stirred at 10~30℃ for 10~30min. The phases are separated to obtain washing water and the washed supported organic phase. Step 4: Back Extraction According to the volume ratio of the washed loaded organic phase to the stripping agent of (4~10):1, the washed loaded organic phase and the stripping agent are mixed and subjected to multi-stage countercurrent stripping at 10~30℃ for 20~60 min. The phases are separated to obtain stripping solution and lean organic phase. Step 5: Degreasing The back-extraction solution is subjected to degreasing treatment to obtain vanadium electrolyte; The vanadium electrolyte has the following characteristics: V(IV) concentration of 105.09~153.00 g / L, K concentration ≤30 mg / L, Mo concentration ≤10 mg / L, and Cr concentration ≤10 mg / L.

2. The method for preparing vanadium electrolyte based on acidic vanadium-rich solution according to claim 1, characterized in that... The vanadium extractant is one or more of di(2-ethylhexyl) phosphate and 2-ethylhexyl phosphate mono(2-ethylhexyl).

3. The method for preparing vanadium electrolyte based on acidic vanadium-rich solution according to claim 1, characterized in that... The saponifying agent is either sodium hydroxide solution or ammonia water.

4. The method for preparing vanadium electrolyte based on acidic vanadium-rich solution according to claim 1, characterized in that... The detergent is one of dilute sulfuric acid and dilute hydrochloric acid at a concentration of 0.01~0.2 mol / L.

5. The method for preparing vanadium electrolyte based on acidic vanadium-rich solution according to claim 1, characterized in that... The stripping agent is a sulfuric acid solution of 2.3~6 mol / L.

6. The method for preparing vanadium electrolyte based on acidic vanadium-rich solution according to claim 1, characterized in that... The oil removal process is carried out by one or more of the following methods: clarification in a clarification tank, adsorption by a resin flotation column, and adsorption by activated carbon.