Preparation method of ultra-pure electrolytic iron

Abstract

The invention provides a preparation method of ultra-pure electrolytic iron, which comprises the following steps: (1) sequentially carrying out pH regulation and ion exchange on an iron electrolyte to obtain an iron electrolysis filtrate; (2) the iron electrolysis filtrate obtained in the step (1) is placed in a first electrolytic cell to be subjected to first electrolysis, and an electrolytic iron crude product is obtained; and (3) the iron electrolysis filtrate obtained in the step (1) is placed in a second electrolytic cell to be subjected to second electrolysis, and the ultra-pure electrolytic iron is obtained. A second anode in the second electrolytic cell is an electrolytic iron crude product obtained in the step (2). According to the preparation method, the ultra-pure electrolytic iron with the purity larger than or equal to 5N can be prepared, meanwhile, the production process is simple, convenient and efficient, and the production cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of metal purification and preparation, and relates to a method for preparing ultra-high-purity electrolytic iron. Background Art

[0002] Ultra-high purity iron, i.e. high purity iron with a purity greater than 5N (99.999%), has excellent ductility, corrosion resistance, excellent thermal conductivity, soft magnetism and high electrical conductivity. These characteristics make it widely used in aerospace, energy, chemical industry, marine engineering and semiconductor industries, such as for manufacturing high-performance engine parts, electromagnetic shielding materials, soft magnetic materials, integrated circuits and amorphous alloys, which can significantly improve the comprehensive performance of materials and the quality of products.

[0003] The application of ZrVFe alloy targets in the semiconductor field is mainly reflected in its use as a preparation material for the getter film required for semiconductor chip packaging. The film is formed during the manufacturing process of semiconductor devices through magnetron sputtering technology, and its high getter performance is used to absorb gas impurities inside the device, thereby improving the performance and reliability of semiconductor devices. CN115679274B discloses a ZrVFe alloy target material and a preparation method and application thereof, comprising the following preparation steps: (1) alloy suspension smelting: Zr and V are used to suspend and smelt a ZrV alloy under argon protection conditions, and then Fe is added for smelting, and the ZrVFe alloy ingot is cooled along with the furnace to obtain a ZrVFe alloy ingot; (2) suspension refining and casting cooling: the ZrVFe alloy ingot is subjected to suspension refining under argon protection conditions, cast and mold, and immediately cooled after molding to obtain an alloy target blank; (3) cutting and preliminary processing: the upper part of the alloy target blank is cut and preliminary processed to obtain a target blank; (4) hot isostatic pressing: the target blank is sheathed, degassed, and then hot isostatic pressing is performed; (5) target material machining: the target blank after hot isostatic pressing is grinded by a grinder to obtain a ZrVFe alloy target material.

[0004] However, with the continuous improvement of semiconductor manufacturing processes, higher requirements have been placed on the purity of ZrVFe alloy targets and the purity of high-purity metal raw materials. Conventional 4N high-purity iron cannot meet the requirements for the preparation of ZrVFe alloy targets.

[0005] In summary, providing a method for preparing ultra-high purity iron with a simple process is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing ultra-high purity electrolytic iron, which can produce ultra-high purity electrolytic iron with a purity of ≥5N, and the production process is simple, efficient and low in production cost.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing ultra-high purity electrolytic iron, the preparation method comprising the following steps:

[0009] (1) adjusting the pH value and performing ion exchange on the iron electrolyte in sequence to obtain an iron electrolyte filtrate;

[0010] (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product;

[0011] (3) placing the iron electrolysis filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain the ultra-high purity electrolytic iron;

[0012] The second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2).

[0013] In the present invention, the specific structures of the first electrolytic cell and the second electrolytic cell are not limited, as long as they can meet the requirements of iron electrolysis, and those skilled in the art can set them according to actual conditions. The obtained ultra-high purity electrolytic iron product can be used for the preparation of target materials.

[0014] The preparation method provided by the present invention helps to improve the electrolysis rate by adjusting the pH of the iron electrolyte. The subsequent ion exchange of the iron electrolyte can remove impurity elements in the electrolyte, which helps to further improve the purity of the electrolytic iron product. A refined iron anode is then obtained through a first electrolysis, and finally a second electrolysis is performed using a specific anode and an electrolyte, which can significantly improve the purity of the electrolytic iron product. The obtained ultra-high purity electrolytic iron has a smooth surface without holes and a silvery white metallic luster, which is beneficial to improving the performance of the ferroalloy target.

[0015] As a preferred technical solution of the present invention, the iron electrolyte in step (1) is Fe 2+ The concentration is 120-180g / L, for example, it can be 125g / L, 130g / L, 135g / L, 140g / L, 145g / L, 150g / L, 155g / L, 160g / L, 165g / L, 170g / L or 175g / L, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0016] In the present invention, the Fe in the iron electrolyte 2+ The concentration of Fe 2+ The mass concentration of the divalent iron ions in the iron electrolyte is obtained by dissolving ferric sulfate, or by dissolving iron in sulfuric acid.

[0017] Preferably, the iron electrolyte in step (1) also contains ammonium sulfate.

[0018] In the present invention, ammonium sulfate is added to the iron electrolyte, and its main function is to serve as a part of the electrolyte, which helps to improve the electrolysis efficiency and the performance of the electrolyte.

[0019] Preferably, the concentration of ammonium sulfate is 0.8-1.2 mol / L, for example, it can be 0.85 mol / L, 0.9 mol / L, 0.95 mol / L, 1 mol / L, 1.05 mol / L, 1.1 mol / L or 1.15 mol / L, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0020] In the present invention, the concentration of ammonium sulfate is the molar concentration of ammonium sulfate.

[0021] As a preferred technical solution of the present invention, the pH value in step (1) is adjusted to 3.5-4.5, for example, it can be 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3 or 4.4, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0022] In the present invention, sulfuric acid or ammonia water can be used to adjust the pH of the iron electrolyte.

[0023] In the present invention, the pH of the iron electrolyte is adjusted to 3.5-4.5, firstly to ensure the reaction rate of the electrolysis process, and secondly to make the iron deposition more uniform and dense, and also to maintain the stability of the electrolyte.

[0024] Preferably, the ion exchange in step (1) is carried out using a chelating resin.

[0025] Preferably, the chelating resin comprises CH90-Na chelating resin.

[0026] It is worth noting that the present invention uses ion exchange to remove impurities in the iron electrolyte and improve the purity of the iron electrolyte, preferably CH90-Na chelating resin.

[0027] As a preferred technical solution of the present invention, in step (2), a first anode and a first cathode are provided in the first electrolytic cell.

[0028] Preferably, the first anode is an iron plate.

[0029] Preferably, the purity of the iron plate is ≥99.9%, and the grade of the iron plate is YT3.

[0030] In the present invention, controlling the purity of the iron plate within a specific range helps to further improve the purity of electrolytic iron.

[0031] Preferably, the first cathode comprises a stainless steel plate.

[0032] Preferably, the distance between the first anode and the first cathode is 1-4 cm, for example, 1.5 cm, 2 cm, 2.5 cm, 3 cm or 3.5 cm, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0033] As a preferred technical solution of the present invention, the current density of the first electrolysis in step (2) is 280-320A / m 2 , for example, it can be 285A / m 2 、290A / m 2 、295A / m 2 、300A / m 2 、305A / m 2 、310A / m 2 or 315A / m 2 The above values ​​are not limited to the above values, and other values ​​within the above range are also applicable.

[0034] Preferably, the temperature of the first electrolysis in step (2) is 55-65°C, for example, it can be 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C or 64°C, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0035] In the present invention, the purity of the crude electrolytic iron can be further improved by controlling the current density and temperature of the first electrolysis within a specific range.

[0036] Preferably, the time of the first electrolysis in step (2) is 10-15 d, for example, 11 d, 12 d, 13 d or 14 d, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0037] As a preferred technical solution of the present invention, in step (3), a second anode and a second cathode are provided in the second electrolytic cell.

[0038] Preferably, the second cathode comprises a stainless steel plate.

[0039] Preferably, the distance between the second anode and the second cathode is 1-4 cm, for example, 1.5 cm, 2 cm, 2.5 cm, 3 cm or 3.5 cm, etc., but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0040] As a preferred technical solution of the present invention, the second electrolysis in step (3) is performed by circulating electrolysis.

[0041] In the present invention, the second electrolysis adopts the method of circulating electrolysis, which not only helps to improve the purity of iron, but also enables large-scale production and improves production efficiency.

[0042] Preferably, during the second electrolysis process in step (3), the iron electrolysis filtrate obtained in step (1) is added.

[0043] In the present invention, the rate of adding the iron electrolytic filtrate obtained in step (1) is 50-70 L / h, for example, it can be 52 L / h, 55 L / h, 58 L / h, 60 L / h, 62 L / h, 65 L / h or 68 L / h, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0044] As a preferred technical solution of the present invention, the current density of the second electrolysis in step (3) is 180-220A / m 2 , for example, it can be 185A / m 2 、190A / m 2 、195A / m 2 , 200A / m 2 , 205A / m 2 , 210A / m 2 or 215A / m 2 The above values ​​are not limited to the above values, and other values ​​within the above range are also applicable.

[0045] Preferably, the temperature of the second electrolysis in step (3) is 35-45°C, for example, it can be 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C or 44°C, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0046] In the present invention, the purity of the electrolytic iron product can be further improved by controlling the current density and temperature of the second electrolysis within a specific range.

[0047] As a preferred technical solution of the present invention, the purity of the ultra-high purity electrolytic iron is ≥5N, for example, it can be 5N1, 5N2, 5N3, 5N4, 5N5, 5N6, 5N7 or 5N9, but is not limited to the listed values, and other values ​​within the numerical range are also applicable.

[0048] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0049] (1) adjusting the pH of the iron electrolyte to 3.5-4.5, and then performing ion exchange with a chelating resin to obtain an iron electrolyte filtrate;

[0050] The iron electrolyte contains Fe 2+ The concentration is 120-180 g / L; the iron electrolyte also contains ammonium sulfate with a concentration of 0.8-1.2 mol / L;

[0051] (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product;

[0052] The first electrolytic cell is provided with a first anode and a first cathode; the first anode is an iron plate; the purity of the iron plate is ≥99.9%; the first cathode comprises a stainless steel plate;

[0053] The current density of the first electrolysis is 280-320A / m 2 , temperature is 55-65℃, time is 10-15d

[0054] (3) placing the iron electrolytic filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain ultra-high purity electrolytic iron with a purity of ≥5N;

[0055] The second electrolytic cell is provided with a second anode and a second cathode; the second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2); the second cathode comprises a stainless steel plate;

[0056] The second electrolysis method is cyclic electrolysis; during the second electrolysis, the iron electrolysis filtrate obtained in step (1) is added;

[0057] The current density of the second electrolysis is 180-220A / m 2 , the temperature is 35-45℃.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The preparation method provided by the present invention helps to improve the electrolysis rate by adjusting the pH of the iron electrolyte, and subsequently uses a chelating resin to perform ion exchange on the iron electrolyte, which can remove impurity elements in the electrolyte, and helps to further improve the purity of the electrolytic iron product. Then, a refined iron anode is obtained through a first electrolysis, and finally a specific anode and electrolyte are used for a second electrolysis. Combined with the regulation of the corresponding current density and temperature parameter range, the purity of the electrolytic iron product can be significantly improved. The purity of the obtained ultra-high purity electrolytic iron is ≥5N, and the surface of the ultra-high purity electrolytic iron is smooth and free of holes, with a silvery white metallic luster, which is beneficial to improving the performance of the ferroalloy target. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] In some of the following examples and comparative examples, the iron electrolyte is prepared using ferrous sulfate, ammonium sulfate and deionized water.

[0062] Example 1

[0063] This embodiment provides a method for preparing ultra-high purity electrolytic iron, the preparation method comprising the following steps:

[0064] (1) adjusting the pH of the iron electrolyte to 4, and then using CH90-Na chelating resin to perform ion exchange to obtain an iron electrolyte filtrate;

[0065] The iron electrolyte contains Fe 2+ The concentration is 150g / L; the iron electrolyte also contains ammonium sulfate with a concentration of 1mol / L;

[0066] (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product;

[0067] The first electrolytic cell is provided with a first anode and a first cathode; the first anode is an iron plate of grade YT3; the purity of the iron plate is 99.9%; the first cathode is a stainless steel plate;

[0068] The current density of the first electrolysis is 300A / m 2 , temperature is 60℃, time is 15d;

[0069] (3) placing the iron electrolytic filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain ultra-high purity electrolytic iron;

[0070] The second electrolytic cell is provided with a second anode and a second cathode; the second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2); the second cathode is a stainless steel plate;

[0071] The second electrolysis method is cyclic electrolysis; during the second electrolysis process, the iron electrolysis filtrate obtained in step (1) is added at a rate of 60 L / h;

[0072] The current density of the second electrolysis is 200A / m 2 , temperature is 40℃.

[0073] Example 2

[0074] This embodiment provides a method for preparing ultra-high purity electrolytic iron, the preparation method comprising the following steps:

[0075] (1) adjusting the pH of the iron electrolyte to 3.5, and then using CH90-Na chelating resin to perform ion exchange to obtain an iron electrolyte filtrate;

[0076] The iron electrolyte contains Fe 2+ The concentration is 130g / L; the iron electrolyte also contains ammonium sulfate with a concentration of 0.8mol / L;

[0077] (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product;

[0078] The first electrolytic cell is provided with a first anode and a first cathode; the first anode is an iron plate of grade YT3; the purity of the iron plate is 99.9%; the first cathode is a stainless steel plate;

[0079] The current density of the first electrolysis is 280A / m 2 , temperature is 65℃, time is 10d;

[0080] (3) placing the iron electrolytic filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain ultra-high purity electrolytic iron;

[0081] The second electrolytic cell is provided with a second anode and a second cathode; the second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2); the second cathode is a stainless steel plate;

[0082] The second electrolysis method is cyclic electrolysis; during the second electrolysis process, the iron electrolysis filtrate obtained in step (1) is added at a rate of 60 L / h;

[0083] The current density of the second electrolysis is 220A / m 2 , the temperature is 45℃.

[0084] Example 3

[0085] This embodiment provides a method for preparing ultra-high purity electrolytic iron, the preparation method comprising the following steps:

[0086] (1) adjusting the pH of the iron electrolyte to 4.5, and then using CH90-Na chelating resin to perform ion exchange to obtain an iron electrolyte filtrate;

[0087] The iron electrolyte contains Fe 2+ The concentration is 170g / L; the iron electrolyte also contains ammonium sulfate with a concentration of 1.2mol / L;

[0088] (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product;

[0089] The first electrolytic cell is provided with a first anode and a first cathode; the first anode is an iron plate of grade YT3; the purity of the iron plate is 99.9%; the first cathode is a stainless steel plate;

[0090] The current density of the first electrolysis is 320A / m 2 , temperature is 55℃, time is 12d;

[0091] (3) placing the iron electrolytic filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain ultra-high purity electrolytic iron;

[0092] The second electrolytic cell is provided with a second anode and a second cathode; the second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2); the second cathode is a stainless steel plate;

[0093] The second electrolysis method is cyclic electrolysis; during the second electrolysis process, the iron electrolysis filtrate obtained in step (1) is added at a rate of 60 L / h;

[0094] The current density of the second electrolysis is 180A / m 2 , temperature is 35℃.

[0095] Example 4

[0096] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the ion exchange in step (1) is performed using an anion exchange resin (such as a quaternary ammonium exchange resin), other conditions are the same as those in Example 1.

[0097] Example 5

[0098] This embodiment provides a method for preparing ultra-high purity electrolytic iron, except that the current density of the first electrolysis in step (2) is 250 A / m 2 Except for this, other conditions are the same as those in Example 1.

[0099] Example 6

[0100] This embodiment provides a method for preparing ultra-high purity electrolytic iron, except that the current density of the first electrolysis in step (2) is 360 A / m 2 Except for this, other conditions are the same as those in Example 1.

[0101] Example 7

[0102] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the temperature of the first electrolysis in step (2) is 40° C., other conditions are the same as those in Example 1.

[0103] Example 8

[0104] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the temperature of the first electrolysis in step (2) is 75° C., other conditions are the same as those in Example 1.

[0105] Example 9

[0106] This embodiment provides a method for preparing ultra-high purity electrolytic iron, except that the current density of the second electrolysis in step (3) is 130 A / m 2Except for this, other conditions are the same as those in Example 1.

[0107] Example 10

[0108] This embodiment provides a method for preparing ultra-high purity electrolytic iron, except that the current density of the second electrolysis in step (3) is 260 A / m 2 Except for this, other conditions are the same as those in Example 1.

[0109] Embodiment 11

[0110] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the temperature of the second electrolysis in step (3) is 25° C., other conditions are the same as those in Example 1.

[0111] Example 12

[0112] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the temperature of the second electrolysis in step (3) is 55° C., other conditions are the same as those in Example 1.

[0113] Example 13

[0114] This embodiment provides a method for preparing ultra-high purity electrolytic iron. Except that the second electrolysis in step (3) does not adopt the cyclic electrolysis method, other conditions are the same as those in Example 1.

[0115] Comparative Example 1

[0116] This comparative example provides a method for preparing electrolytic iron. Except that the ion exchange in step (1) is adjusted to use P204 extractant for extraction and purification, other conditions are the same as those in Example 1.

[0117] Comparative Example 2

[0118] This comparative example provides a method for preparing electrolytic iron. Except that the ion exchange in step (1) is adjusted to filter using a filter cloth with a precision of 5 μm, other conditions are the same as those in Example 1.

[0119] Comparative Example 3

[0120] This comparative example provides a method for preparing electrolytic iron. Except that the second electrolysis operation in step (3) is not performed, other conditions are the same as those in Example 1.

[0121] The purity of the electrolytic iron products obtained in the above examples and comparative examples was measured using a glow discharge mass spectrometer (GDMS). The results are shown in Table 1.

[0122] Table 1

[0123]

[0124]

[0125] From Table 1, we can see that:

[0126] (1) The preparation method provided in Examples 1-3 of the present invention, through the control of corresponding processes and parameter ranges, the purity of the obtained electrolytic iron product reaches more than 99.9995%, and the surface of the obtained electrolytic iron product is smooth without holes and has a silvery white metallic luster;

[0127] (2) From the comparison between Example 1 and Example 4 and Comparative Examples 1-2, it can be seen that when the iron electrolyte is extracted and purified by anion exchange resin or P204 extractant or filtered by a filter cloth with a precision of 5 μm, impurities in the electrolyte cannot be effectively removed, thereby resulting in a decrease in the purity of the electrolytic iron product;

[0128] (3) By comparing Example 1 with Examples 5-6 and Examples 9-10, it can be seen that when the current density of the first electrolysis and the second electrolysis is not within the preferred range, the purity of the crude electrolytic iron is poor, which in turn affects the purity of the electrolytic iron product, and the surface quality of the obtained electrolytic iron product is also poor;

[0129] (4) By comparing Example 1 with Examples 7-8 and Examples 11-12, it can be seen that when the temperature parameters of the first electrolysis and the second electrolysis are not within the preferred range, it is not conducive to improving the purity of the electrolytic iron product;

[0130] (5) By comparing Example 1 with Example 13, it can be seen that when the second electrolysis is a conventional electrolysis method, it is not only not conducive to improving the purity of the electrolytic iron product, but also leads to a decrease in the production rate of the electrolytic iron product;

[0131] (6) By comparing Example 1 with Comparative Example 3, it can be seen that when only conventional iron plates are used as anodes for electrolysis, the purity of the obtained crude electrolytic iron cannot meet the required requirements.

[0132] The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed structural features, that is, it does not mean that the present invention must rely on the above-mentioned detailed structural features to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the components selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing ultra-high purity electrolytic iron, characterized in that: The preparation method comprises the following steps: (1) adjusting the pH value and performing ion exchange on the iron electrolyte in sequence to obtain an iron electrolyte filtrate; (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product; (3) placing the iron electrolysis filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain the ultra-high purity electrolytic iron; The second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2).

2. The preparation method according to claim 1, characterized in that: Fe in the iron electrolyte of step (1) 2+ The concentration is 120-180g / L; Preferably, the iron electrolyte in step (1) further contains ammonium sulfate; Preferably, the concentration of ammonium sulfate is 0.8-1.2 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that: The step (1) wherein the pH is adjusted to a pH value of 3.5-4.5; Preferably, the ion exchange in step (1) is carried out using a chelating resin; Preferably, the chelating resin comprises CH90-Na chelating resin.

4. The preparation method according to any one of claims 1 to 3, characterized in that Step (2) The first electrolytic cell is provided with a first anode and a first cathode; Preferably, the first anode is an iron plate; Preferably, the purity of the iron plate is ≥99.9%; Preferably, the first cathode comprises a stainless steel plate; Preferably, the distance between the first anode and the first cathode is 1-4 cm.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Step (2) The current density of the first electrolysis is 280-320A / m 2 ; Preferably, the temperature of the first electrolysis in step (2) is 55-65° C.; Preferably, the time of the first electrolysis in step (2) is 10-15 days.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (3) The second electrolytic cell is provided with a second anode and a second cathode; Preferably, the second cathode comprises a stainless steel plate; Preferably, the distance between the second anode and the second cathode is 1-4 cm.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (3) the second electrolysis is performed by cyclic electrolysis; Preferably, during the second electrolysis process in step (3), the iron electrolysis filtrate obtained in step (1) is added.

8. The preparation method according to any one of claims 1 to 7, characterized in that: Step (3) The current density of the second electrolysis is 180-220A / m 2 ; Preferably, the temperature of the second electrolysis in step (3) is 35-45°C.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The purity of the ultra-high purity electrolytic iron is ≥5N.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) adjusting the pH of the iron electrolyte to 3.5-4.5, and then performing ion exchange with a chelating resin to obtain an iron electrolyte filtrate; The iron electrolyte contains Fe 2+ The concentration is 120-180 g / L; the iron electrolyte also contains ammonium sulfate with a concentration of 0.8-1.2 mol / L; (2) placing the iron electrolysis filtrate obtained in step (1) in a first electrolytic cell for first electrolysis to obtain a crude electrolytic iron product; The first electrolytic cell is provided with a first anode and a first cathode; the first anode is an iron plate; the purity of the iron plate is ≥99.9%; the first cathode comprises a stainless steel plate; The current density of the first electrolysis is 280-320A / m 2 , temperature is 55-65℃, time is 10-15d; (3) placing the iron electrolysis filtrate obtained in step (1) in a second electrolytic cell for a second electrolysis to obtain ultra-high purity electrolytic iron with a purity of ≥5N; The second electrolytic cell is provided with a second anode and a second cathode; the second anode in the second electrolytic cell is the crude electrolytic iron obtained in step (2); the second cathode comprises a stainless steel plate; The second electrolysis is carried out in a cyclic electrolysis mode; during the second electrolysis, the iron electrolysis filtrate obtained in step (1) is added; The current density of the second electrolysis is 180-220A / m 2 , the temperature is 35-45℃.

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