Method for preparing ferrochromium leaching solution by one-step method and application

Abstract

The invention provides a one-step method for preparing ferrochromium leachate and application, and the method comprises the following steps: mixing a ferrochromium-containing material with a hydrochloric acid solution and a chromium-containing oxidizing agent to carry out leaching reaction, and after the reaction is finished, carrying out solid-liquid separation to obtain the ferrochromium leachate. According to the method provided by the invention, the chromium-containing oxidizing agent and the hydrochloric acid are used for synergistically leaching the ferrochromium metal raw material, so that the ferrochromium leaching rate is improved, no hydrogen is produced, the reaction safety is improved, the leachate with high chromium concentration is obtained, and the leachate can be directly used for preparing the ferrochromium flow battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow batteries, and particularly relates to a method for preparing chromic iron leaching solution by a one-step method and its application. Background Art

[0002] As an efficient and large-scale energy storage electrochemical device, the performance of the electrolyte of the iron-chromium flow battery directly affects the overall efficiency and stability of the battery. At present, the key material of the iron-chromium flow battery electrolyte is a mixed solution of chromium chloride-ferrous chloride, and its preparation mainly relies on chromium chloride hexahydrate (CrCl 3 ·6H 2 O) and ferrous chloride tetrahydrate (FeCl 2 ·4H 2 O) as raw materials. However, the preparation processes of chromium chloride hexahydrate and ferrous chloride tetrahydrate are complex, involving multiple processes such as oxidation, reduction, and separation, resulting in high production costs and large energy consumption. Taking chromium chloride hexahydrate as an example, its preparation usually uses chromite as the raw material, and after steps such as oxidative leaching and separation and conversion, hexavalent chromium salts are obtained, and then trivalent chromium salts are prepared through reduction reactions. During this process, iron and other associated components in the chromite are separated and finally remain in the slag containing hexavalent chromium, which not only causes waste of resources but also brings environmental pollution problems due to chromite slag being classified as hazardous waste.

[0003] The prior art provides some improved methods for preparing electrolytes.

[0004] CN116826127A discloses a method for preparing an iron-chromium flow battery electrolyte. Chromium-iron raw materials are mixed with hydrochloric acid to obtain a leaching solution. After the obtained leaching solution is successively concentrated and cooled and crystallized, a mixed crystal and a mother liquor are obtained. Then, after the obtained mixed crystal is dissolved, it is successively mixed with hydrochloric acid and a chloride salt to obtain an iron-chromium flow battery electrolyte. This method has high energy consumption and generates a large amount of hydrogen gas during the reaction, posing a safety hazard.

[0005] CN115832378A discloses a method for preparing key materials of an electrolyte and its application. Materials containing chromium metal and iron metal are mixed with water, and then hydrochloric acid solution is added for chlorination and acidolysis. After solid-liquid separation, the key materials of the electrolyte are obtained. This method adopts a multi-stage countercurrent leaching process to improve the leaching efficiency of chromium and iron, but this process increases the complexity of the process, and non-oxidizing gases (such as nitrogen, argon, etc.) need to be introduced to dilute hydrogen to reduce the explosion risk, further increasing the production cost.

[0006] CN116555592A discloses a method for leaching chromium and iron in ferrochrome alloy. The ferrochrome alloy is added to heated acid solution and leaching intensifier for leaching, and then solid-liquid separation is carried out to obtain the leaching solution. This method uses the leaching intensifier to assist in destroying the structure of the ferrochrome alloy, thereby improving the leaching efficiency. However, the effect of the leaching intensifier is relatively limited and the leaching rate is low.

[0007] Therefore, it is of great significance to develop a method for preparing the electrolyte of iron-chromium flow battery with simple process, low cost, safety and environmental protection. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method and application for preparing chromium-iron leaching solution by one-step method, which can improve the chromium-iron leaching rate, process safety and shorten the process flow.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] In the first aspect, the present invention provides a method for preparing chromium-iron leaching solution by one-step method, and the method includes:

[0011] Mix the chromium-iron-containing material with hydrochloric acid solution and chromium-containing oxidant for leaching reaction, and after the reaction is completed, carry out solid-liquid separation to obtain the chromium-iron leaching solution.

[0012] In the preparation method provided by the present invention, a chromium-containing oxidant is added during the acid leaching process of the chromium-iron raw material. The addition of the oxidant can promote the decomposition of chromium and iron combined in various forms in the chromium-iron raw material, including but not limited to the crystal structures such as body-centered cubic (BCC), face-centered cubic (FCC), orthorhombic and multiphase structures, and promote the cleavage of covalent bonds. At the same time, the oxidant can also react rapidly with the active hydrogen (H - ) generated during the reaction, converting hydrogen into hydrogen ions (H + ) and thus avoiding the generation of hydrogen. Therefore, by introducing a chromium-containing oxidant as a reaction additive: ① The efficiency of converting chromium and iron in the raw material into trivalent chromium and iron ions can be significantly improved, and the leaching rates of chromium and iron can be increased; ② The rapid conversion of active hydrogen is realized, the generation of hydrogen is avoided, and the safety is improved; ③ The chromium-containing oxidant itself is converted into trivalent chromium ions, which can be used as a chromium supplement in the leaching solution to realize component utilization, and it is beneficial to obtain a leaching solution with a high chromium concentration; ④ No other impurity components are introduced, and there is no need for secondary treatment of the additive. The preparation method provided by the present invention can directly achieve the efficient leaching of chromium and iron in one-step short process, shorten the process flow, improve the safety, and is easy to realize industrial production.

[0013] After the solid-liquid separation, the obtained solid is the leaching residue, and the main components of the leaching residue are silicon and carbon.

[0014] Preferably, the chromium-containing iron material includes any one or at least two combinations of ferrochrome, chromium-based alloy, chromium-containing cast iron, or chromium-containing iron slag. Typical but non-limiting combinations include the combination of ferrochrome and chromium-based alloy, the combination of chromium-containing cast iron and chromium-containing iron slag, the combination of ferrochrome, chromium-based alloy, and chromium-containing cast iron, the combination of chromium-based alloy, chromium-containing cast iron, and chromium-containing iron slag, or the combination of ferrochrome, chromium-based alloy, chromium-containing cast iron, and chromium-containing iron slag.

[0015] Preferably, the particle size of the chromium-containing iron material is 40 - 200 mesh. For example, it can be 40 mesh, 45 mesh, 50 mesh, 60 mesh, 90 mesh, 120 mesh, 150 mesh, 180 mesh, or 200 mesh, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the mass fraction of the hydrochloric acid solution is 8 - 37%. For example, it can be 8%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32%, or 35%, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the mass ratio of the hydrochloric acid solution to the chromium-containing iron material is (4 - 20):1. For example, it can be 4:1, 5:1, 8:1, 10:1, 12:1, 15:1, 18:1, or 20:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0018] Preferably, the chromium-containing oxidant includes any one or at least two combinations of chromic anhydride, sodium chromate, or potassium chromate. Typical but non-limiting combinations include the combination of chromic anhydride and sodium chromate, the combination of sodium chromate and potassium chromate, the combination of chromic anhydride and potassium chromate, or the combination of chromic anhydride, sodium chromate, and potassium chromate.

[0019] Preferably, the dosage of the chromium-containing oxidant is 0.1 - 2 times the theoretical dosage of Cr for reacting with chromium and iron in the chromium-containing iron material 6+ For example, it can be 0.1 times, 0.15 times, 0.3 times, 0.5 times, 0.8 times, 1 time, 1.2 times, 1.5 times, 1.8 times, or 2 times, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0020] In the present invention, the theoretical dosage is calculated according to the stoichiometric coefficients of the total reaction equation for the reaction of chromium and iron with Cr 6+ (Combining elementary reactions, only the total reaction is shown for the convenience of explaining the calculation of dosage).

[0021] The total reaction equation is as follows:

[0022] Cr + Cr 6+ → 2Cr 3+

[0023] Fe + Cr 6+ → Cr 3+ + Fe 3+

[0024] In the present invention, by precisely controlling the dosage of the chromium-containing oxidant, the leaching efficiency is maximized. When the dosage of the chromium-containing oxidant is too low, the oxidation effect is poor, resulting in incomplete leaching reaction, and the retention of chromium and iron in the slag causes waste of resources; when the dosage of the chromium-containing oxidant is too high, the oxidant cannot be completely reduced, and there is Cr 6+ residue in the obtained high-chromium leaching solution and slag, which is not friendly to the environment.

[0025] Preferably, the temperature of the leaching reaction is 50 - 150 °C, for example, it can be 50 °C, 55 °C, 75 °C, 90 °C, 100 °C, 120 °C, 145 °C or 150 °C, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the time of the leaching reaction is 0.5 - 8 h, for example, it can be 0.5 h, 0.8 h, 1 h, 2.5 h, 3 h, 4 h, 5 h, 6 h, 6.5 h, 7 h or 8 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the pressure of the leaching reaction is 10 - 500 kPa, for example, it can be 10 kPa, 50 kPa, 100 kPa, 150 kPa, 200 kPa, 250 kPa, 300 kPa, 350 kPa, 395 kPa, 400 kPa, 450 kPa, 475 kPa or 500 kPa, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the leaching reaction is carried out in a reactor.

[0029] Preferably, the chromium concentration in the chromium and iron leaching solution is 2 - 5 M, for example, it can be 2 M, 2.5 M, 2.8 M, 3 M, 3.5 M, 4 M, 4.6 M or 5 M, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] As a preferred technical solution of the method provided by the present invention, the method includes the following steps:

[0031] A material containing chromium iron with a particle size of 40 - 200 mesh, a hydrochloric acid solution with a mass fraction of 8 - 37%, and a chromium-containing oxidant are mixed and added to a reactor for leaching reaction. Among them, the mass ratio of the hydrochloric acid solution to the material containing chromium iron is (4 - 20):1. The chromium-containing oxidant includes any one or a combination of at least two of chromic anhydride, sodium chromate, or potassium chromate. The dosage of the chromium-containing oxidant is 0.1 - 2 times the theoretical dosage of Cr 6+ for reacting with chromium and iron in the material containing chromium iron. The temperature of the leaching reaction is 50 - 150 °C, the time of the leaching reaction is 0.5 - 8 h, and the pressure of the leaching reaction is 10 - 500 kPa. After the reaction ends, solid-liquid separation is carried out to obtain leaching residues and a chromium iron leaching solution, and the chromium concentration in the chromium iron leaching solution is 2 - 5 M.

[0032] In a second aspect, the present invention provides an application of the method for preparing a chromium iron leaching solution described in the first aspect. The method for preparing the chromium iron leaching solution is applied to the preparation of an iron-chromium flow battery;

[0033] The chromium iron leaching solution is used to prepare an electrolyte for an iron-chromium flow battery.

[0034] The chromium iron leaching solution prepared by the present invention is a mixed solution of chromium chloride and iron chloride, and has a high chromium concentration. In the application, reduction iron powder is directly added to supplement the iron content while reducing trivalent iron, and ferrous chloride is selectively added for further preparation according to the requirement of the electrolyte for the iron concentration, and then an electrolyte for an iron-chromium flow battery can be obtained.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The method provided by the present invention adds a chromium-containing oxidant during the leaching process, which realizes that some chromium- and iron-containing materials that are difficult to be acid-dissolved in the traditional leaching process are more easily dissolved, thereby improving the utilization rates of chromium and iron, increasing the chromium concentration in the leaching solution, shortening the process flow, and reducing the production cost; the addition of the oxidant avoids the generation of hydrogen, making the preparation process safer and conducive to industrial scale-up production; by controlling the addition amount of the oxidant, the oxidant is completely reduced, and there is no residual hexavalent chromium in the high-chromium leaching solution and the leaching residues. The residues can be directly used as building materials without further treatment, and the process flow is cleaner. Specific Embodiments

[0037] The technical solutions of the present invention will be further described below through specific embodiments.

[0038] To clearly illustrate the technical solutions of the present invention, in the specific embodiments, the composition of chromium iron includes: Cr 50 wt%, Fe 30 wt%, Si 3 wt%, C 7 wt%, and the balance is other impurities such as Al, V, Mg, Mn, etc.

[0039] The composition of the chromium-based alloy includes: Cr 50 wt%, Fe 5 wt%, Si 0.5 wt%, C 0.3 wt%, and the balance is other impurities such as Ni, Mo, Co, Al, etc.

[0040] The composition of the chromium-containing cast iron includes: Cr 30 wt%, Fe 60 wt%, Si 1 wt%, C 3 wt%, and the balance is other impurities such as Mo, Ni, Mn, etc.

[0041] Example 1

[0042] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. The method includes the following steps:

[0043] A hydrochloric acid solution with a mass fraction of 20% is mixed with 90-mesh ferrochrome in a mass ratio of 15:1 and added to a reactor. At the same time, chromium anhydride, a chromium-containing oxidant, is added. The addition amount of the chromium-containing oxidant is 1.8 times the theoretical amount of Cr 6+ for reacting with chromium and iron in the ferrochrome. Leaching reaction is carried out, controlling the leaching reaction temperature at 100 °C, the leaching reaction time at 2.5 h, and the leaching reaction pressure at 110 kPa. After the reaction ends, the chromium-iron leaching solution is filtered. The chromium concentration of the chromium-iron leaching solution is 2.5 M, and at the same time, leaching residues are obtained.

[0044] Example 2

[0045] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. The method includes the following steps:

[0046] A hydrochloric acid solution with a mass fraction of 8% is mixed with 200-mesh chromium-based alloy in a mass ratio of 20:1 and added to a reactor. At the same time, chromium anhydride, a chromium-containing oxidant, is added. The addition amount of the chromium-containing oxidant is 2 times the theoretical amount of Cr 6+ for reacting with chromium and iron in the chromium-based alloy. Leaching reaction is carried out, controlling the leaching reaction temperature at 120 °C, the leaching reaction time at 6.5 h, and the leaching reaction pressure at 200 kPa. After the reaction ends, the chromium-iron leaching solution is filtered. The chromium concentration of the chromium-iron leaching solution is 2.2 M, and at the same time, leaching residues are obtained.

[0047] Example 3

[0048] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. The method includes the following steps:

[0049] A hydrochloric acid solution with a mass fraction of 35% is mixed with 150-mesh ferrochrome in a mass ratio of 8:1 and added to a reactor. At the same time, sodium chromate, a chromium-containing oxidant, is added. The addition amount of the chromium-containing oxidant is the Cr 6+Perform the leaching reaction with 1.5 times the theoretical dosage. Control the leaching reaction temperature at 55 °C, the leaching reaction time at 8 h, and the leaching reaction pressure at 20 kPa. After the reaction ends, filter to obtain the ferrochrome leaching solution with a chromium concentration of 4.1 M, and at the same time obtain the leaching residue.

[0050] Example 4

[0051] This example provides a method for preparing a ferrochrome leaching solution by a one-step process. The method includes the following steps:

[0052] Mix a hydrochloric acid solution with a mass fraction of 25% and 120-mesh chromium-containing cast iron in a mass ratio of 10:1 and add them to the reactor. At the same time, add sodium chromate as a chromium-containing oxidant. The addition amount of the chromium-containing oxidant is 0.8 times the theoretical dosage of Cr for reacting with chromium and iron in the chromium-containing cast iron. 6+ Perform the leaching reaction with 0.8 times the theoretical dosage. Control the leaching reaction temperature at 140 °C, the leaching reaction time at 3 h, and the leaching reaction pressure at 360 kPa. After the reaction ends, filter to obtain the ferrochrome leaching solution with a chromium concentration of 2.0 M, and at the same time obtain the leaching residue.

[0053] Example 5

[0054] This example provides a method for preparing a ferrochrome leaching solution by a one-step process. The method includes the following steps:

[0055] Mix a hydrochloric acid solution with a mass fraction of 15% and 180-mesh ferrochrome in a mass ratio of 5:1 and add them to the reactor. At the same time, add potassium chromate as a chromium-containing oxidant. The addition amount of the chromium-containing oxidant is 0.3 times the theoretical dosage of Cr for reacting with chromium and iron in the ferrochrome. 6+ Perform the leaching reaction with 0.3 times the theoretical dosage. Control the leaching reaction temperature at 120 °C, the leaching reaction time at 4 h, and the leaching reaction pressure at 200 kPa. After the reaction ends, filter to obtain the ferrochrome leaching solution with a chromium concentration of 3 M, and at the same time obtain the leaching residue.

[0056] Example 6

[0057] This example provides a method for preparing a ferrochrome leaching solution by a one-step process. The method includes the following steps:

[0058] Mix a hydrochloric acid solution with a mass fraction of 37% and 40-mesh ferrochrome in a mass ratio of 6:1 and add them to the reactor. At the same time, add chromium anhydride as a chromium-containing oxidant. The addition amount of the chromium-containing oxidant is 1 times the theoretical dosage of Cr for reacting with chromium and iron in the ferrochrome. 6+ Perform the leaching reaction with 1 times the theoretical dosage. Control the leaching reaction temperature at 150 °C, the leaching reaction time at 2.5 h, and the leaching reaction pressure at 475 kPa. After the reaction ends, filter to obtain the ferrochrome leaching solution with a chromium concentration of 4.2 M, and at the same time obtain the leaching residue.

[0059] Example 7

[0060] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 1, the temperature of the leaching reaction is controlled at 25 °C, and the rest are the same as in Example 1.

[0061] Example 8

[0062] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 1, the temperature of the leaching reaction is controlled at 180 °C, and the rest are the same as in Example 1.

[0063] Example 9

[0064] This example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 1, the mass concentration of the hydrochloric acid solution is controlled at 4%, and the rest are the same as in Example 1.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 1, chromium anhydride, a chromium-containing oxidant, is not added, and the rest are the same as in Example 1.

[0067] Comparative Example 2

[0068] This comparative example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 3, sodium chromate, a chromium-containing oxidant, is not added, and the rest are the same as in Example 3.

[0069] Comparative Example 3

[0070] This comparative example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 5, potassium chromate, a chromium-containing oxidant, is not added, and the rest are the same as in Example 5.

[0071] Comparative Example 4

[0072] This comparative example provides a method for preparing a chromium-iron leaching solution by a one-step method. Compared with Example 1, the leaching reaction is carried out in a beaker, that is, the reaction is carried out in an open environment, the leaching reaction pressure is not controlled, and the pressure is 0 kPa. The rest are the same as in Example 1.

[0073] The chromium and iron contents of the leaching solutions and leaching residues obtained in the examples and comparative examples were measured, and the leaching rates of chromium and iron were calculated. The results are listed in Table 1. Among them, the chromium content in the leaching residue is calculated as Cr 2 O 3 counted.

[0074] The method for measuring the chromium and iron contents in the leaching solution is as follows: After diluting the solution to a suitable concentration, the chromium ion concentration and iron ion concentration in it are measured by inductively coupled plasma atomic emission spectrometry.

[0075] The method for determining the chromium and iron contents in the leaching residue is as follows: Accurately weigh 0.05 - 0.1 g of the residue sample into a platinum crucible, add a certain multiple of the flux (anhydrous sodium carbonate and sodium tetraborate with a mass ratio of 2:1), mix it with the sample, cover the surface of the mixed residue sample and flux with a layer of flux, place the platinum crucible containing the sample into a muffle furnace with a preset temperature, melt it at 950 °C for about 20 min, take it out and let it cool slightly, rinse the outside of the crucible with water, put it into a 100 ml beaker containing 50 ml of 20% hydrochloric acid, heat it on an electric furnace to dissolve, let it cool after complete dissolution, dilute the solution to an appropriate concentration, and then determine the chromium ion concentration and iron ion concentration therein by inductively coupled plasma atomic emission spectrometry, and calculate the chromium and iron contents in the residue.

[0076] Table 1

[0077]

[0078]

[0079] It can be seen from Table 1 that:

[0080] (1) For the one-step method for preparing chromium-iron leaching solution provided in Examples 1 - 6 of the present invention, by adding a chromium-containing oxidant, the conversion rates of chromium and iron can be significantly increased, the chromium concentration in the chromium-iron leaching solution can be increased, and the chromium content in the tailing slag can be reduced; among them, the conversion rate of chromium > 99.4%, and the chromium content in the tailing slag < 2.5%.

[0081] (2) By comprehensively comparing Example 1 and Examples 7 - 9, it can be known that when the reaction temperature is too low and the hydrochloric acid concentration is too low, it is not conducive to the leaching of chromium and iron, resulting in a low chromium concentration in the chromium-iron leaching solution, and a large amount of chromium remains in the slag, causing waste of resources. When the reaction temperature is too high, the leaching rates of chromium and iron are not further increased and basically tend to be stable, resulting in waste of energy.

[0082] (3) By comprehensively comparing Example 1, Examples 3, 5 and Comparative Examples 1 - 3, it can be known that when the chromium-containing oxidant is not added, the leaching rates of chromium and iron are significantly reduced, the concentration of the leaching solution is low, the residual chromium content in the leaching residue is high, and hydrogen is generated during the reaction, which has certain risks.

[0083] (4) By comprehensively comparing Example 1 and Comparative Example 4, it can be known that when the reaction pressure is not controlled and the reaction is carried out in an open environment, it is not conducive to the efficient leaching of chromium and iron, resulting in a decrease in the conversion rate of chromium and an increase in the chromium content in the tailing slag.

[0084] In summary, the method provided by the present invention adds a chromium-containing oxidant during the leaching process, enabling some chromium-containing iron materials that are difficult to dissolve in acid during the traditional leaching process to be more easily dissolved. This further improves the utilization rates of chromium and iron, increases the chromium concentration in the leaching solution, shortens the process flow, and reduces production costs. After adding the oxidant, the generation of hydrogen is avoided, making the preparation process safer and facilitating industrial scale-up production. By controlling the amount of oxidant added, the oxidant is completely reduced, and there is no residual hexavalent chromium in the high-chromium leaching solution and the leaching residue. The residue can be directly used as building materials without further treatment, making the process flow cleaner.

[0085] In the specific embodiments described above, the purpose, technical solutions, and beneficial effects of the present invention have been further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A one-step method for preparing ferrochrome leaching solution, characterized in that: The method comprises: The ferrochrome-containing material is mixed with a hydrochloric acid solution and a chromium-containing oxidant to carry out a leaching reaction. After the reaction is completed, the solid and liquid are separated to obtain a ferrochrome leaching solution.

2. The method according to claim 1, characterized in that The ferrochrome-containing material includes any one of ferrochrome, chromium-based alloy, chromium-containing cast iron or ferrochrome-containing slag, or a combination of at least two thereof; Preferably, the ferrochrome-containing material has a particle size of 40-200 mesh.

3. The method according to claim 1 or 2, characterized in that: The mass fraction of the hydrochloric acid solution is 8-37%; Preferably, the mass ratio of the hydrochloric acid solution to the ferrochromium-containing material is (4-20):

1.

4. The method according to any one of claims 1 to 3, characterized in that: The chromium-containing oxidant includes any one of chromic anhydride, sodium chromate or potassium chromate, or a combination of at least two thereof; Preferably, the amount of the chromium-containing oxidant is Cr 6+ 0.1-2 times of the theoretical dosage.

5. The method according to any one of claims 1 to 4, characterized in that: The temperature of the leaching reaction is 50-150°C.

6. The method according to any one of claims 1 to 5, characterized in that: The leaching reaction time is 0.5-8h.

7. The method according to any one of claims 1 to 6, characterized in that: The pressure of the leaching reaction is 10-500 kPa; Preferably, the leaching reaction is carried out in a reactor.

8. The method according to any one of claims 1 to 7, characterized in that: The chromium concentration in the ferrochrome leaching solution is 2-5M.

9. The method according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: A ferrochromium-containing material with a particle size of 40-200 mesh, a hydrochloric acid solution with a mass fraction of 8-37% and a chromium-containing oxidant are mixed and added to a reactor for leaching reaction, wherein the mass ratio of the hydrochloric acid solution to the ferrochromium-containing material is (4-20):1, the chromium-containing oxidant includes any one of chromic anhydride, sodium chromate or potassium chromate or a combination of at least two thereof, and the amount of the chromium-containing oxidant is Cr to react with chromium and iron in the ferrochromium-containing material. 6+ The leaching reaction temperature is 50-150°C, the leaching reaction time is 0.5-8h, the leaching reaction pressure is 10-500kPa, and after the reaction, solid-liquid separation is performed to obtain leaching residue and ferrochrome leaching solution, and the chromium concentration in the ferrochrome leaching solution is 2-5M.

10. An application of the method for preparing ferrochrome leaching solution by one step as claimed in any one of claims 1 to 9, characterized in that: The method for preparing ferrochromium leaching solution is applied to preparing iron-chromium flow battery; The ferrochromium leaching solution is used to prepare an electrolyte for an iron-chromium liquid flow battery.

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