Initial electrolyte and method for preparing high-purity iron through sacrificial anode electrolytic refining

Abstract

The invention relates to the field of iron group metal refining, and particularly discloses an initial electrolyte and method for preparing high-purity iron through sacrificial anode electrolytic refining, quaternary ammonium salt is adopted for regulating and controlling the solvation structure of the electrolyte, so that hydrogen evolution in the iron electrolytic refining process is remarkably inhibited, the pH tolerance range of the electrolyte is widened, and the high-purity iron is prepared. In the electrolytic refining process, acid does not need to be added into the electrolytic bath for pH regulation, and precipitation of a blocked diaphragm is avoided. Based on the advantages, according to the method for preparing the high-purity iron through electrolytic refining, the anolyte can enter the cathode tank only through simple precipitation, extraction and pH regulation, the electrolyte in the cathode tank can directly enter the anode tank, and the process is simple and easy to operate. The method is low in cost, the electrolyte can be recycled, and the method is a green and environment-friendly high-purity iron preparation method.

Description

Technical Field

[0001] This invention relates to the field of iron group metal refining, specifically to an initial electrolyte and method for preparing high-purity iron by sacrificial anode electrolytic refining. Background Technology

[0002] Currently, the aerospace, energy, and emerging semiconductor industries have increasingly stringent requirements for the heat resistance and corrosion resistance of materials used in their applications. High-purity and ultra-high-purity iron exhibits excellent performance in key properties such as ductility, corrosion resistance, thermal properties, soft magnetic properties, and electrical conductivity, significantly improving the performance and quality of materials such as steel, semiconductors, and amorphous materials, leading to their widespread application in these fields. Furthermore, the food industry also has a significant demand for high-purity iron.

[0003] There are two main methods for preparing high-purity iron: pyrometallurgical purification and hydrometallurgical purification. Electrolytic refining is a type of hydrometallurgical purification. As early as 2001, Japan's Nippon Minerals & Metals Co., Ltd. proposed a method for preparing high-purity iron using multiple electrolytic purification processes. The principle is very simple: after electricity is applied, the metallic iron at the anode is oxidized into ferrous ions, which migrate to the cathode under the influence of the electric field, gain electrons, and then revert to metallic iron. However, the production of high-purity iron through electrolytic refining has not yet been widely applied in my country. This is because, in actual production processes, ferrous ions in the solution are easily converted into ferric ions due to oxidation by oxygen in the air. In addition to increasing energy consumption and reducing current efficiency, ferric ions can also form precipitates at pH values ​​above 3.5, adhering to the cathode surface and affecting the quality of deposited iron. Furthermore, they can form flocculent precipitates that clog the diaphragm, leading to increased cell pressure. Therefore, much work has been dedicated to removing ferric iron (Fe3+) from electrolytes. For example, applying a paraffin layer to the electrolyte surface can effectively isolate the electrolyte from air, thus preventing ferrous iron (Fe2+) from being oxidized to ferric iron (Fe3+). However, due to difficulties in maintenance and replacement, high costs, and complex operation, this method cannot be truly applied in production. Chinese invention patent CN113308712A proposes adding a Buchner funnel containing iron powder to the front end of the electrolytic cell to reduce ferric iron (Fe3+) to ferrous iron (Fe2+). However, the iron powder itself is easily oxidized, and the disproportionation reaction between elemental iron and ferric iron is inefficient, with the iron powder prone to caking, making it unsuitable for practical production. Another example is Chinese invention patent CN116555835A, which mitigates the effects of ferric iron by adding ferric iron stabilizers and pH stabilizers. However, this method still faces problems such as continuously rising pH and ferric hydroxide precipitation during long-term electrolysis exceeding 24 hours.

[0004] In typical iron electrolytic refining processes, the initial pH of the solution is controlled at 2-3, which is insufficient to cause oxidized iron ions to precipitate. However, on the cathode side, hydrogen evolution and iron deposition compete with each other. Besides increasing system energy consumption, hydrogen evolution also causes the pH of the electrolyte to continuously rise, ultimately leading to the precipitation of ferric iron. Therefore, providing an electrolyte and electrolytic refining method that can effectively suppress hydrogen evolution during iron electrolytic refining is of great significance for achieving stable operation of the iron electrolytic refining process. Summary of the Invention

[0005] Based on the above reasons, this invention discloses an initial electrolyte and method for preparing high-purity iron by sacrificial anode electrolytic refining, which can effectively suppress the hydrogen evolution reaction that occurs at the cathode during electrolytic refining, enabling sustainable production, and eliminating the need for pH adjustment during electrolysis.

[0006] To address the aforementioned technical problems, the present invention is as follows:

[0007] An initial electrolyte for preparing high-purity iron by sacrificial anode electrolytic refining, the initial electrolyte comprising an aqueous solvent, an electrolyte salt, and additives, wherein the aqueous solvent is deionized water or ultrapure water, the electrolyte salt is one or both of ferrous chloride and ferrous sulfate, with a concentration of 0.5-3 mol / L, the additives are a hydrogen evolution inhibitor and a pH adjuster, the hydrogen evolution inhibitor is a quaternary ammonium salt with a concentration of 0.5-4 mol / L, and the pH adjuster comprises one or at least two of boric acid, hydrochloric acid, ascorbic acid, and citric acid, with a concentration of 0-0.2 mol / L, and the pH of the initial electrolyte is 1-5.

[0008] Preferably, the concentration of the electrolyte salt is 1-2 mol / L, the concentration of the quaternary ammonium salt is 1-3 mol / L, the concentration of the pH adjuster is 0.01-0.1 mol / L, and the pH range of the initial electrolyte is 1-3.

[0009] Preferably, the quaternary ammonium salt comprises, but is not limited to, one or at least two of choline chloride, tetrabutylammonium chloride, and urea.

[0010] Another aspect of the present invention provides a method for preparing high-purity iron by sacrificial anode electrolytic refining using the above-mentioned initial electrolyte, comprising the following steps:

[0011] S1. Preparation of initial electrolyte: Dissolve quaternary ammonium salt and electrolyte salt in an aqueous solvent, add pH adjuster to prepare initial electrolyte. The concentration of ferrous salt in the electrolyte is 1-2 mol / L, the concentration of quaternary ammonium salt is 1-3 mol / L, the concentration of pH adjuster is 0.01-0.1 mol / L, and the pH range of the initial electrolyte is 1-3.

[0012] Preferably, the quaternary ammonium salt is a hydrogen evolution inhibitor and a leveling agent, and the quaternary ammonium salt includes, but is not limited to, one or more of choline chloride, tetrabutylammonium chloride, and urea.

[0013] S2. Electrolysis Process: Using a soluble anode as the electrolytic refining anode, a hydrophilic substrate as the cathode, an ion-exchange membrane as the diaphragm, and the electrolyte described in S1 as the initial electrolyte, constant current electrolytic refining is carried out in an electrolytic cell with a current density of 100-1000 A / m. 2 The temperature is 20-80℃, the electrolysis time is 12-168h, and the electrolysis voltage is 0.5V-3V.

[0014] Preferably, the soluble anode material is one of carbon steel, industrial pure iron, or pig iron; the cathode material is one of copper plate, titanium plate, or graphite plate; the ion exchange membrane is an anion exchange membrane or a Nafion membrane; the electrolytic cell is made of polypropylene or titanium metal; the anode-cathode distance is 10-30 mm; the temperature is 30-70℃; and the current density ranges from 100-500 A / m. 2 The electrolysis time is 24-120 hours.

[0015] Preferably, the ferrous ions in the cathode electrolyte gradually decrease, while the ferrous ions in the anolyte gradually increase. There is no need to adjust the pH value in the electrolytic cell during the electrolysis process, and the cathode iron deposition current efficiency is higher than 99%.

[0016] S3. Impurity Removal Process: A peristaltic pump is used to pump the electrolyte from the cathode tank into the first storage tank at a flow rate of 0.1-1 L / h. A peristaltic pump is used to pump the electrolyte from the first storage tank into the anode tank at a flow rate of 0.1-1 L / h. A peristaltic pump is used to pump the electrolyte from the anode tank out at a flow rate of 0.1-1 L / h. After sequentially passing through precipitation impurity removal, solution extraction, and pH adjustment to 1-3, a peristaltic pump is used to pump the impurity-removed electrolyte into the second storage tank at a flow rate of 0.1-1 L / h. A peristaltic pump is used to pump the electrolyte from the second storage tank into the cathode tank at a flow rate of 0.1-1 L / h.

[0017] Preferably, the precipitation and impurity removal process in S3 involves adding an excess of 60%-100% sodium fluoride or potassium fluoride, stirring for 4 hours, and then filtering. The solution extraction process involves mixing the electrolyte with a kerosene solution of P204 or P507 extractant, stirring for 4 hours, and then allowing it to stand for separation. The pH adjustment process involves adding an appropriate amount of concentrated hydrochloric acid to adjust the pH to 1-3.

[0018] Preferably, the electrolyte is recycled between the cathode and anode tanks, and the metal ions removed during precipitation and solution extraction are all at the ppm level, with no large amount of waste generated.

[0019] S4. High-purity iron collection process: After electrolytic refining, the cathode surface is cleaned with boiling water, then ultrasonically cleaned in anhydrous ethanol, the electrode is vacuum dried, and high-purity iron is obtained by peeling off and sealed for storage.

[0020] Preferably, the iron content in high-purity iron is 99.9%-99.99%;

[0021] Preferably, the surface of the high-purity iron cathode obtained by electrolytic refining is mirror-bright.

[0022] By using quaternary ammonium salts as hydrogen evolution inhibitors and leveling agents to regulate the solvation structure of the electrolyte, hydrogen evolution during the electrolytic refining of iron is significantly suppressed, and the pH tolerance range of the electrolyte is improved. During the electrolytic refining process, there is no need to add acid to the electrolytic cell for pH control, and no precipitates are generated that clog the diaphragm.

[0023] This invention discloses a method for preparing high-purity iron through electrolytic refining. The anolyte only needs simple precipitation, extraction, and pH adjustment before entering the cathode tank, while the electrolyte in the cathode tank can enter the anode tank through a storage tank. The process is simple and easy to operate. This invention is low-cost, and the electrolyte can be recycled, making it a green and environmentally friendly method for preparing high-purity iron.

[0024] Beneficial effects of this invention:

[0025] (1) By regulating the solvation structure of the aqueous electrolyte, the present invention effectively suppresses the hydrogen evolution side reaction and improves the current efficiency, increasing the current efficiency from 95.2% to 99.7%.

[0026] (2) This invention can effectively suppress the hydrogen evolution side reaction without the use of organic solvents or ionic liquids, and greatly increases the concentration of ferrous ions in the solution. Compared with this type of electrolyte, the energy consumption is significantly reduced and the working voltage is reduced from 3.5V to 0.9V (compared to patent CN 118621372 A).

[0027] (3) The present invention does not require repeated adjustment of the pH value of the electrolyte during the electrolytic refining process, so the process operation is simple and the system is highly stable.

[0028] (4) The materials used in this invention are low in cost and readily available, the electrolyte can be recycled, and no large amount of waste is generated during the production process, making it environmentally friendly. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the electrolytic iron refining process;

[0030] Figure 2 This is a photograph of iron deposited at the cathode in Comparative Example 1;

[0031] Figure 3 This is a photograph of iron deposited at the cathode in Example 1;

[0032] Figure 4 This is a SEM image of cathode-deposited iron in Comparative Example 1;

[0033] Figure 5 This is a SEM image of iron deposited at the cathode in Example 1. Detailed Implementation

[0034] This invention discloses an initial electrolyte and method for preparing high-purity iron through sacrificial anode electrolytic refining. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. The method and application of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the method and application of this invention without departing from its content, spirit, and scope to realize and apply the technology of this invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention.

[0035] Example 1

[0036] An initial electrolyte and method for preparing high-purity iron by sacrificial anode electrolytic refining involves dissolving analytical grade tetrabutylammonium chloride and ferrous chloride tetrahydrate in boiling ultrapure water to prepare a 3M tetrabutylammonium chloride and 1M ferrous chloride aqueous solution. 0.01M ascorbic acid is added to adjust the pH to 2.0 to complete the preparation of the initial electrolyte.

[0037] like Figure 1 As shown, the electrolyte is transferred to a polypropylene electrolytic cell and two polytetrafluoroethylene storage tanks (the first storage tank and the second storage tank).

[0038] The copper sheet, after being sanded and polished, and the Q235 carbon steel were used as the cathode and anode, respectively.

[0039] Both the anode and cathode electrolytes are heated to 60°C using a water jacket, with a Nafion membrane as the diaphragm, at 100 A / m. 2 Electrolytic iron refining is carried out at a current density of 0.9V.

[0040] During the electrolytic refining process, under the action of the peristaltic pump, the cathode electrolyte flows into the first storage tank at a flow rate of 0.5L / h. The first storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0041] During the electrolytic refining process, under the action of the peristaltic pump, the electrolyte in the first storage tank flows into the anode electrolytic cell at a flow rate of 0.5 L / h.

[0042] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the anolyte flows into the settling tank at a flow rate of 0.5 L / h.

[0043] After 24 hours of continuous electrolysis, based on the ICP test results of the solution in the precipitation tank, an excess of 60% sodium fluoride was added, stirred for 4 hours, filtered, and the filtrate was transferred to the extraction tank.

[0044] Add a kerosene solution containing P204 extractant to the filtrate tank, stir for 4 hours, let stand and separate, and transfer the electrolyte to a pH control tank;

[0045] Add concentrated hydrochloric acid to the pH control tank to adjust the pH of the electrolyte to 2.0. Transfer the electrolyte to the second storage tank. The second storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0046] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the second storage tank flows into the cathode tank at a flow rate of 0.5 L / h.

[0047] After 96 hours of electrolytic refining, i.e., after the electrolyte has circulated four times, the DC power supply is turned off, the anode plate and cathode plate are removed, the surface of the anode plate is washed with boiling water to remove the electrolyte and carbon film, and then dried for later use.

[0048] The cathode plate surface was cleaned with boiling water to remove the electrolyte. The cathode plate was then transferred to anhydrous ethanol and ultrasonically cleaned for 30 minutes. After ultrasonic cleaning, the cathode plate was transferred to a vacuum oven and dried at 100℃ for 8 hours. The iron gain was measured, and the current efficiency was calculated to be 99.5%. High-purity iron was obtained by peeling and sealed for storage. The purity of the high-purity iron was 99.99%. A photograph of the deposited iron on the cathode is shown below. Figure 3 As shown, the SEM image of the cathode deposited iron is as follows: Figure 5 As shown. From Figure 3 and Figure 5 It can be seen that the surface of the cathode iron is mirror-like and shiny.

[0049] Example 2

[0050] An electrolyte and method for preparing high-purity iron by sacrificial anode electrolytic refining involves dissolving analytical grade choline chloride and ferrous chloride tetrahydrate in boiled ultrapure water to prepare a 2M choline chloride and 2M ferrous chloride aqueous solution. 0.01M boric acid is added as a buffer, and concentrated hydrochloric acid is added to adjust the pH value to 2.0 to complete the preparation of the initial electrolyte.

[0051] like Figure 1 As shown, the electrolyte is transferred to a titanium electrolytic cell and two titanium storage tanks (the first storage tank and the second storage tank).

[0052] The titanium plate and Q235 carbon steel, after being sanded and polished, were used as the cathode and anode, respectively.

[0053] Both the anode and cathode electrolytes are heated to 80°C using a water jacket, with an anion exchange membrane as the diaphragm, at 500 A / m. 2Electrolytic iron refining is carried out at a current density of 2.3V.

[0054] During the electrolytic refining process, under the action of a peristaltic pump, the cathode electrolyte flows into the first storage tank at a flow rate of 1L / h. The first storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen.

[0055] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the first storage tank flows into the anode electrolytic cell at a flow rate of 1L / h.

[0056] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the anolyte flows into the settling tank at a flow rate of 1L / h.

[0057] After 12 hours of continuous electrolysis, based on the ICP test results of the solution in the precipitation tank, 60% excess potassium fluoride was added, stirred for 4 hours, filtered, and the filtrate was transferred to the extraction tank.

[0058] Add a kerosene solution of P507 extractant to the filtrate tank, stir for 4 hours, let stand and separate, and transfer the electrolyte to the pH control tank.

[0059] Add concentrated hydrochloric acid to the pH control tank to adjust the pH of the electrolyte to 2.0. Transfer the electrolyte to the second storage tank. The second storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0060] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the second storage tank flows into the cathode tank at a flow rate of 1L / h.

[0061] After 96 hours of electrolytic refining, i.e., after eight electrolyte cycles, the DC power supply is turned off, the anode plate and cathode plate are removed, the surface of the anode plate is washed with boiling water to remove the electrolyte and carbon film, and then dried for later use.

[0062] The cathode plate surface was cleaned with boiling water to remove the electrolyte. The cathode plate was then transferred to anhydrous ethanol for ultrasonic cleaning for 30 minutes. After ultrasonic cleaning, the cathode plate was transferred to a vacuum oven and dried at 100°C for 8 hours. The iron weight gain was measured, and the current efficiency was calculated to be 99.7%. High-purity iron was obtained by peeling and sealed for storage. The purity of the high-purity iron was 99.99%, and the surface of the cathode iron was mirror-like.

[0063] Example 3

[0064] An initial electrolyte and method for preparing high-purity iron by sacrificial anode electrolytic refining involves dissolving analytical grade tetrabutylammonium chloride and ferrous chloride tetrahydrate in boiled ultrapure water to prepare a 1M urea and 1M ferrous sulfate aqueous solution. 0.01M citric acid is added to adjust the pH to 1.5 to complete the preparation of the initial electrolyte.

[0065] like Figure 1 As shown, the electrolyte is transferred to a polypropylene electrolytic cell and two polytetrafluoroethylene storage tanks (the first storage tank and the second storage tank).

[0066] The graphite sheet, after being sanded and polished, and Q235 carbon steel were used as the cathode and anode, respectively.

[0067] Both the anode and cathode electrolytes are heated to 70°C using a water jacket, with a Nafion membrane as the diaphragm, at 200 A / m. 2 Electrolytic iron refining is carried out at a current density of 1.2V.

[0068] During the electrolytic refining process, under the action of the peristaltic pump, the cathode electrolyte flows into the first storage tank at a flow rate of 0.1L / h. The first storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0069] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the first storage tank flows into the anode electrolytic cell at a flow rate of 0.1 L / h.

[0070] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the anolyte flows into the settling tank at a flow rate of 0.1 L / h.

[0071] After 18 hours of continuous electrolysis, based on the ICP test results of the solution in the precipitation tank, an excess of 60% sodium fluoride was added, stirred for 4 hours, filtered, and the filtrate was transferred to the extraction tank.

[0072] Add a kerosene solution containing P204 extractant to the filtrate tank, stir for 4 hours, let stand and separate, and transfer the electrolyte to a pH control tank;

[0073] Add concentrated hydrochloric acid to the pH control tank to adjust the pH of the electrolyte to 1.5. Transfer the electrolyte to the second storage tank, seal the second storage tank, leaving an air inlet and an air outlet, and purge it with nitrogen for protection.

[0074] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the second storage tank flows into the cathode tank at a flow rate of 0.1 L / h.

[0075] After 72 hours of electrolytic refining, i.e., after the electrolyte has circulated four times, the DC power supply is turned off, the anode plate and cathode plate are removed, the surface of the anode plate is washed with boiling water to remove the electrolyte and carbon film, and then dried for later use.

[0076] The cathode plate surface was cleaned with boiling water to remove the electrolyte. The cathode plate was then transferred to anhydrous ethanol and ultrasonically cleaned for 30 minutes. After ultrasonic cleaning, the cathode plate was transferred to a vacuum oven and dried at 100°C for 8 hours. The iron weight gain was measured, and the current efficiency was calculated to be 99.1%. High-purity iron was obtained by peeling and sealed for storage. The purity of the high-purity iron was 99.9%.

[0077] Comparative Example 1

[0078] Analytical grade ferrous chloride tetrahydrate was dissolved in boiled ultrapure water to prepare a 1M ferrous chloride aqueous solution. 0.01M boric acid was added as a buffer, and concentrated hydrochloric acid was added to adjust the pH to 2.0 to complete the preparation of the initial electrolyte.

[0079] The electrolyte was transferred to a polypropylene electrolytic cell and two polytetrafluoroethylene storage tanks.

[0080] The copper sheet, after being sanded and polished, and the Q235 carbon steel were used as the cathode and anode, respectively.

[0081] Both the anode and cathode electrolytes are heated to 60°C using a water jacket, with a polyester membrane as the diaphragm, at a pressure of 10 mA / cm². 2 Electrolytic iron refining was carried out at a current density of 0.4V, and hydrochloric acid was added to the cathode tank every 4 hours to adjust the pH to 2.0.

[0082] During the electrolytic refining process, under the action of the peristaltic pump, the cathode electrolyte flows into the first storage tank at a flow rate of 0.5L / h. The first storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0083] During the electrolytic refining process, under the action of the peristaltic pump, the electrolyte in the first storage tank flows into the anode electrolytic cell at a flow rate of 0.5 L / h.

[0084] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the anolyte flows into the settling tank at a flow rate of 0.5 L / h.

[0085] After 24 hours of continuous electrolysis, based on the ICP test results of the solution in the precipitation tank, an excess of 60% sodium fluoride was added, stirred for 4 hours, filtered, and the filtrate was transferred to the extraction tank.

[0086] Add a kerosene solution containing P204 extractant to the filtrate tank, stir for 4 hours, let stand and separate, and transfer the electrolyte to a pH control tank;

[0087] Add concentrated hydrochloric acid to the pH control tank to adjust the pH of the electrolyte to 2.0. Transfer the electrolyte to the second storage tank. The second storage tank is sealed, with an air inlet and an air outlet, and is protected by nitrogen gas.

[0088] During the electrolytic refining process, under the action of a peristaltic pump, the electrolyte in the second storage tank flows into the cathode tank at a flow rate of 0.5 L / h.

[0089] After 96 hours of electrolytic refining, the DC power supply was turned off, the anode plate and cathode plate were removed, the surface of the anode plate was washed with boiling water to remove the electrolyte and carbon film, and then dried for later use.

[0090] The cathode plate surface was cleaned with boiling water to remove the electrolyte. The cathode plate was then transferred to anhydrous ethanol and ultrasonically cleaned for 30 minutes. After ultrasonic cleaning, the cathode plate was transferred to a vacuum oven and dried at 100℃ for 8 hours. The iron gain was measured, and the current efficiency was calculated to be 95.2%. High-purity iron was obtained by peeling and sealed for storage; the purity of the iron was 99%. A photograph of the deposited iron on the cathode is shown below. Figure 2 As shown, the SEM image of the cathode deposited iron is as follows: Figure 4 As shown. From Figure 2 and Figure 4 It can be seen that the surface of the cathode iron is relatively rough and uneven.

[0091] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values ​​of the present invention can all achieve the method, and examples are not listed here.

[0092] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An initial electrolyte for preparing high-purity iron by sacrificial anode electrolytic refining, characterized in that, The initial electrolyte includes an aqueous solvent, an electrolyte salt, and additives; The aqueous solvent is deionized water or ultrapure water; The electrolyte salt is one or both of ferrous chloride and ferrous sulfate, with a concentration of 0.5-3 mol / L; The additives are hydrogen evolution inhibitors and pH adjusters, wherein the hydrogen evolution inhibitors are quaternary ammonium salts with a concentration of 0.5-4 mol / L; The pH adjuster includes one or more of boric acid, hydrochloric acid, ascorbic acid, and citric acid, with a concentration of 0-0.2 mol / L, and the initial electrolyte has a pH of 1-5.

2. The initial electrolyte according to claim 1, characterized in that, The quaternary ammonium salt includes, but is not limited to, one or at least two of choline chloride, tetrabutylammonium chloride, and urea.

3. The initial electrolyte according to claim 1, characterized in that, The concentration of the electrolyte salt is 1-2 mol / L, the concentration of the quaternary ammonium salt is 1-3 mol / L, the concentration of the pH adjuster is 0.01-0.1 mol / L, and the pH range of the initial electrolyte is 1-3.

4. A method for preparing high-purity iron by sacrificial anode electrolytic refining, the method comprising: S1. Preparation of the initial electrolyte according to any one of claims 1-3: The quaternary ammonium salt and electrolyte salt are dissolved in an aqueous solvent, and a pH adjuster is added to prepare an initial electrolyte solution. The initial electrolyte solution has a ferrous salt concentration of 1-3 mol / L, a quaternary ammonium salt concentration of 1-4 mol / L, a pH adjuster concentration of 0.01-0.1 mol / L, and a pH range of 1-3. S2, Electrolysis process: Using a soluble anode as the electrolytic refining anode, a hydrophilic substrate as the cathode, an ion-exchange membrane as the diaphragm, and the electrolyte described in S1 as the initial electrolyte, constant current electrolytic refining is performed in an electrolytic cell with a current density of 100-1000 A / m. 2 The temperature is 20-80℃, the electrolysis time is 12-168h, and the electrolysis voltage is 0.5V-3V. S3. Impurity removal process: The electrolyte in the cathode cell is pumped into the first storage tank at a flow rate of 0.1-1 L / h. The electrolyte in the first storage tank is pumped into the anode cell at a flow rate of 0.1-1 L / h. The electrolyte in the anode cell is pumped out at a flow rate of 0.1-1 L / h. After passing through precipitation and impurity removal, solution extraction, and pH adjustment to 1-3, the pH-adjusted electrolyte is pumped into the second storage tank at a flow rate of 0.1-1 L / h. The electrolyte in the second storage tank is pumped into the cathode cell at a flow rate of 0.1-1 L / h. S4. High-purity iron collection process: After electrolytic refining, the cathode surface is cleaned with boiling water, then ultrasonically cleaned in anhydrous ethanol, the electrode is vacuum dried, and high-purity iron is obtained by peeling and sealed storage.

5. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, The soluble anode in S2 is made of carbon steel, industrial pure iron, or pig iron; the cathode is made of copper plate, titanium plate, or graphite plate; the ion exchange membrane is an anion exchange membrane or a Nafion membrane; the electrolytic cell is made of polypropylene or titanium; the anode-cathode distance is 10-30 mm; the temperature is 30-70℃; and the current density range is 100-500 A / m. 2 The electrolysis time is 24-120 hours.

6. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, In the constant current electrolytic refining process described in S2, ferrous ions in the cathode electrolyte gradually become depleted, while ferrous ions in the anode electrolyte gradually become enriched. There is no need to adjust the pH value in the electrolytic cell during the electrolysis process, and the current efficiency of cathode iron deposition is higher than 99%.

7. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, In the constant current electrolytic refining process described in S2, transition metal cations will not diffuse from the anode tank to the cathode tank through the diaphragm, thus avoiding the deposition of transition metal cations generated in the soluble anode at the cathode during the constant current electrolytic refining process.

8. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, The precipitation and impurity removal process described in S3 involves adding an excess of 60%-100% sodium fluoride or potassium fluoride, stirring for 4 hours, and then filtering. The solution extraction process involves mixing the electrolyte with a kerosene solution of P204 or P507 extractant, stirring for 4 hours, and then allowing it to stand for separation. The pH adjustment process involves adding an appropriate amount of concentrated hydrochloric acid to adjust the pH to 1-3.

9. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, In S3, the electrolyte is recycled between the cathode and anode tanks. The metal ions removed by precipitation and solution extraction are all at the ppm level, and no large amount of waste is generated.

10. The method for preparing high-purity iron by sacrificial anode electrolytic refining according to claim 4, characterized in that, The high-purity iron obtained in S4 has an iron content of 99.9%-99.99%.

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