Method for preparing high-purity metallic iron through ultrasonic circulation electrodeposition method

Abstract

The invention provides a method for preparing high-purity metallic iron by an ultrasonic circulation electrodeposition method. The method comprises the following steps: (1) preparing a ferrous sulfate electrolyte; (2) purification: purifying the prepared electrolyte by an ion exchange method; and (3) ultrasonic electrodeposition: an ultrasonic generator, pig iron for an anode, a stainless steel plate for a cathode, a filter cloth bag sleeved on the anode, an anode area inside and a cathode area outside are arranged at the bottom of an electrodeposition cell, high-purity metal iron is prepared through ultrasonic electrodeposition, the content of low-melting-point metal and gas impurities is further reduced through high-temperature hydrogen reduction treatment of the prepared iron plate, and the high-purity metal iron with the purity larger than 99.999% is obtained. The metal iron with the purity larger than 99.999% is prepared through the ultrasonic electrodeposition method, the problems that according to a conventional electrolytic method, hydrogen evolution is serious, a cathode iron plate is poor in toughness and high in oxygen content, an anode filter cloth bag is prone to being blocked, and the current efficiency and the iron plate quality are affected are solved, and the prepared iron plate does not need follow-up treatment, can be stored for a long time and is not prone to rusting.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrometallurgical preparation of high-purity metallic iron, and particularly relates to a method for preparing high-purity metallic iron of 4N or above by ultrasonic circulation electrodeposition. BACKGROUND

[0002] Pure iron can be divided into pure iron (2N-3N), high-purity iron (4N) and ultra-pure iron (5N-6N) according to the content of impurity elements. High-purity iron and ultra-pure iron have high purity and excellent ductility, corrosion resistance, soft magnetism, electrical conductivity, thermal conductivity and other physical and chemical properties and special functions, and are widely used in high-end equipment manufacturing, national defense science and technology industry and high-tech fields such as aviation, aerospace, shipbuilding, nuclear power, medical equipment, electronics, new energy vehicles and ocean engineering. For example, the nuclear spent fuel storage and transportation container produced by using high-purity iron and ultra-high-purity iron has a dense organization, no casting defects and grain boundary segregation inclusions; the dynamic mechanical properties, fatigue properties and overheating capacity of military accessories such as axle gearboxes, gearboxes and large crankshafts produced by using high-purity iron and ultra-high-purity iron are good; the high-end castings such as ship diesel engine bodies, cylinder covers and cylinder sleeves produced by using high-purity iron and ultra-high-purity iron have high thermal fatigue resistance, hardness and wear resistance, which improves the service life of the engine.

[0003] In 1986, Professor An of Japan prepared high-purity iron with a purity of 99.995% by electrolysis. In 1987, F. Faudot, a French scholar, prepared ultra-pure iron with a purity of more than 99.999% by horizontal zone melting method. In the mid to late 1990s, Japan, France, Germany and the United States widely carried out research on the preparation technology of ultra-pure iron. At present, the preparation and production technology of high-purity iron and ultra-pure iron in the world is basically monopolized by Japan. Toyo Kohan Asia Lead Company in Japan produces industrial ultra-pure iron by electrolysis, and the highest purity is 99.999%, which can be commercially produced.

[0004] There are two routes for the production of high-purity iron at present, namely, fire refining and wet electrolysis. The fire refining generally uses low-purity electrolytic iron as raw material, and further purifies the high-purity pure iron product by vacuum melting, zone melting and other methods. The electrolytic wet method includes solution electrolysis and molten salt electrolysis, and the solution electrolysis is divided into soluble anode electrolysis and inert anode electrodeposition.

[0005] The extremely low element control of pyro-process high-purity iron production depends on special element control of high-purity ore or high-purity pig iron, complex special process equipment, etc. The patent CN114686691B of Hebei Longfengshan Foundry Co., Ltd. discloses a method and system for preparing 4N high-purity iron, which connects a cold-wall vacuum induction refining furnace and a hydrogen plasma arc melting refining furnace to the same vacuum system, heats and melts 2N or 3N electrolytic pure iron raw material, generates a vacuum refined iron bar in a directional pulling solidification mode, then gradually melts the vacuum refined iron bar into a droplet by a hydrogen plasma arc to generate a 4N high-purity iron bar (purity 99.99-99.999%) in a directional pulling solidification mode. The process flow is long, the energy consumption is large, and the cost is high.

[0006] For the soluble anode electrolysis method, the patent CN113481540A of Shanghai University discloses an electrolytic preparation method, the electrolyte mainly contains FeSO4·7H2O, a small amount of additives for maintaining the stability of the electrolyte, and a supporting electrolyte for improving the conductivity of the electrolyte solution. The purity of the prepared iron is 99.9676%, but the purity cannot meet the requirements of 4N high-purity iron.

[0007] For the inert anode electrodeposition method, the patent CN116555835A discloses a production process of high-purity iron, which includes electrolyte purification and impurity removal, pre-electrodeposition, and electrodeposition. The method first purifies and removes impurities from the iron electrolyte by precipitation method before electrodeposition, then pre-electrodeposits to further remove impurities, and finally electrodeposits to produce high-purity iron. At the same time, trivalent iron stabilizer and pH stabilizer are added during electrodeposition to realize stable production of high-purity iron. The method has multiple impurity removal and electrodeposition, the process flow is long, there are many process parameters to be controlled in the process, and the prepared high-purity iron has high content of interstitial element impurities such as carbon and oxygen.

[0008] The current inert anode electrodeposition method for preparing high-purity iron has the problems of easy clogging of the anode filter bag, oxidation of divalent iron to trivalent iron, and increase of pH value during electrolysis, which causes trivalent iron precipitation and further clogging of the filter bag, resulting in rough surface of the cathode iron plate, poor toughness of the cathode iron plate, high oxygen content, and other problems. There are also problems of hydrogen or a large amount of chlorine gas, poor quality of the iron plate caused by hydrogen evolution at the cathode, and peeling of the iron plate. SUMMARY

[0009] In order to overcome the problems and shortcomings of the high-purity metal iron preparation process, the present application provides a method for preparing 5N high-purity iron by ultrasonic electrodeposition, which comprises the following steps:

[0010] Step (1), preparation of electrolyte:

[0011] Dissolve the iron powder with a purity of 97% with high-purity sulfuric acid or directly dissolve the higher-purity ferrous sulfate heptahydrate crystal to prepare an electrolyte with an iron concentration of 60-80 g / L;

[0012] Step (2), electrolyte purification: the electrolyte in step (1) is purified by countercurrent through an ion exchange resin column at a speed of 3-5 BV / h, wherein the ion exchange resin is sequentially washed with 20-30% sulfuric acid solution and pure water before being packed into the column;

[0013] Step (3), ultrasonic circulation electrodeposition: an ultrasonic generating device is installed at the bottom of the electrodeposition tank, and an ultrasonic control device is connected outside the electrodeposition tank; the electrolytic anode is made of cast iron, and the anode is sleeved with a filter cloth bag; the cathode is made of stainless steel plate, an acidity detection probe is installed in the cathode area, and ultrasonic electrodeposition is carried out at a current density of 200-300 A / m2; the electrolyte is dynamically circulated at a circulation speed of 1-3 tanks / h; after a certain thickness of iron layer is deposited, electrodeposition is stopped, and the plate is stripped;

[0014] Step (4), hydrogen reduction purification: the iron plate prepared in step (3) is placed into a hydrogen reduction furnace, hydrogen is introduced for high-temperature treatment, and finally 5N-grade ultra-pure iron with a purity of ≥99.999% is obtained;

[0015] Preferably, the ion exchange resin in step (2) is a chelating resin for removing heavy metal impurity ions such as copper, nickel, cobalt and zinc in the solution; when the total amount of the solution purified by the resin reaches 1000 BV, the resin is sequentially washed with 50% sulfuric acid solution and pure water, and then returned to the purification link for circulation.

[0016] Preferably, the electrolysis temperature in step (3) is 50-70°C, the PH value of the electrolysis process is controlled to be 3-4, and the ultrasonic frequency is 500-1000 Hz; 3. After electrodeposition, the electrolyte after electrodeposition is returned to electrodeposition after acid adjustment.

[0017] Preferably, after high-temperature hydrogen reduction treatment of the iron sheet in step (4), the iron sheet needs to be vacuum packaged and stored.

[0018] Preferably, when the concentration of sodium and potassium ions in the electrolyte after electrodeposition in step (5) is higher than 0.1 g / L, the electrolyte after electrodeposition is not recycled, and new electrolyte is configured for electrodeposition.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1. Ultrasonic strengthening of the electrolyte is beneficial to the timely release of dissolved oxygen in the electrolyte, reduces the oxygen content in the electrolyte and the oxygen content in the solution near the plate, and reduces the oxygen content in the electrodeposited iron plate;

[0021] 2. It is beneficial to alleviate the polarization of iron ions near the cathode plate, accelerate the plate forming speed, and generate dense iron plate, thereby improving the plate forming quality, and reducing the oxygen content and other impurities such as other gases and part of metal impurities in the cathode iron plate;

[0022] 3. The ultrasonic reinforcement is beneficial to reduce the discharge opportunity of hydrogen ions, reduce the hydrogen evolution probability, improve the iron plate, improve the current efficiency, and reduce the power consumption;

[0023] 4. The ultrasonic reinforcement is beneficial to quickly discharge the hydrogen gas near the cathode plate from the cathode electrolyte, avoid hydrogen embrittlement of the electrodeposited iron plate, and avoid easy peeling;

[0024] 5. The ultrasonic reinforcement is beneficial to prevent the anode mud generated in the subsequent electrodeposition process from blocking the anode bag, cause the electrodeposition voltage to rise, reduce the energy consumption, and benefit the electrodeposited iron plate;

[0025] After the electrolyte is purified by ion exchange method, electrodeposition method and hydrogen reduction method, the high-purity metal iron with more than 99.999% can be prepared, the iron plate is dense, has good toughness, can be stored for a long time, is not easy to rust, and meets the needs of high-end users. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The process flowchart of the present application

[0027] Figure 2 The high-purity metal iron prepared in Example 1 of the present application

[0028] Figure 3 The high-purity metal iron prepared in Example 2 of the present application

[0029] Figure 4 The high-purity metal iron prepared in Example 3 of the present application DETAILED DESCRIPTION

[0030] Example 1

[0031] (1) Preparation of electrolyte: Dissolve the iron powder with a purity of 97% with high-purity sulfuric acid, and control the iron ion concentration to be about 60 g / L.

[0032] (2) Purification of electrolyte: The electrolyte is purified by countercurrent through the ion exchange resin column at a speed of 5 BV / h.

[0033] (3) Ultrasonic electrodeposition: a. Ultrasonic electrodeposition tank is equipped with an indirect heating circulation pipe, connected with a water bath pot to heat the electrolyte, an ultrasonic generating device is installed at the bottom of the electrodeposition tank, the ultrasonic control device is connected outside the electrodeposition tank, an anode and a cathode are installed, the anode is made of cast iron, the anode is sleeved with a filter cloth bag, the cathode is made of stainless steel plate, and an acidity detection probe is installed in the cathode area;

[0034] b. Add electrolyte into the ultrasonic electrodeposition tank, open the water bath pot and the indirect heating circulation valve between the electrolyte, connect the anode and cathode conductive rods and the direct current power supply, open the ultrasonic generating device when the electrolyte temperature rises to 70℃, control the ultrasonic frequency to be 500 Hz, and the electrodeposition current density is 300 A / m2 Catholyte circulation speed 1 tank / h; during the electrodeposition process, high-purity sulfuric acid is used to keep the pH value of the electrolyte at about 4.0, electrodeposition is performed for 120 h, electrodeposition is stopped, the plate is stripped, and a metal iron plate with a thickness of 3-5 mm is obtained. The electrolyte after electrodeposition is supplemented, the acid is adjusted, and then returned to the electrodeposition cycle.

[0035] (4) Hydrogen reduction purification: the prepared metal iron plate is placed in a hydrogen reduction furnace, hydrogen is introduced for high-temperature treatment, the reduction temperature is 1000°C, the temperature is kept for 6 h, the iron plate is taken out after cooling, and vacuum packaging is performed.

[0036] Example 2

[0037] (1) Preparation of electrolyte: iron powder with a purity of 97% is dissolved with high-purity sulfuric acid, and the iron ion concentration is controlled at about 70 g / L.

[0038] (2) Purification: the electrolyte is countercurrently purified through an ion exchange column at a speed of 4 BV / h.

[0039] (3) Ultrasonic electrodeposition: a, an indirect heating circulation pipe is installed in the ultrasonic electrodeposition tank, a water bath is connected to heat the electrolyte, an ultrasonic generating device is installed at the bottom of the electrodeposition tank, the ultrasonic control device is connected outside the electrodeposition tank, an anode and a cathode are installed, the anode is made of cast iron, the anode is sleeved with a filter cloth bag, the cathode is made of stainless steel, and an acidity detection probe is installed in the cathode area;

[0040] b, the electrolyte is added to the ultrasonic electrodeposition tank, the water bath and the indirect heating circulation valve of the electrolyte are opened, the anode and cathode conductive rods and the direct current source are connected, the ultrasonic generating device is started when the electrolyte temperature rises to 60°C, the ultrasonic frequency is controlled at 750 Hz, and the electrodeposition current density is 250 A / m 2 Catholyte circulation speed 2 tank / h; during the electrodeposition process, high-purity sulfuric acid is used to keep the pH value of the electrolyte at about 3.5, electrodeposition is performed for 96 h, electrodeposition is stopped, the plate is stripped, and a metal iron plate with a thickness of 3-5 mm is obtained; the electrolyte after electrodeposition is supplemented, the acid is adjusted, and then returned to the electrodeposition cycle.

[0041] (4) Hydrogen reduction purification: the prepared metal iron plate is placed in a hydrogen reduction furnace, hydrogen is introduced for high-temperature treatment, the reduction temperature is 1100°C, the temperature is kept for 5 h, the iron plate is taken out after cooling, and vacuum packaging is performed.

[0042] Example 3

[0043] (1) Preparation of electrolyte: high-purity ferrous sulfate heptahydrate crystals are dissolved with pure water, and the iron ion concentration is controlled at 80 g / L.

[0044] (2) Purification: the electrolyte is countercurrently purified through an ion exchange column at a speed of 3 BV / h.

[0045] (3) ultrasonic electrodeposition: a, the ultrasonic electrodeposition tank is equipped with an indirect heating circulating pipe connected to a water bath pot for heating electrolyte, an ultrasonic generator is installed at the bottom of the electrodeposition tank, and an ultrasonic control device is connected outside the electrodeposition tank; an anode and a cathode are installed; the anode is made of cast iron, the anode is sleeved with a filter cloth bag, and the cathode is made of stainless steel plate; an acidity detection probe is installed in the cathode area;

[0046] b, electrolyte is added to the ultrasonic electrodeposition tank, the water bath pot and the indirect heating circulating valve between the electrolyte are turned on, the anode and cathode conductive rods and the direct current power supply are connected, the ultrasonic generator is turned on when the electrolyte temperature rises to 50 DEG C, the ultrasonic frequency is controlled to be 1000 Hz, the electrodeposition current density is 200 A / m 2 , the cathode electrolyte circulation speed is 1 tank / h; during the electrodeposition process, high-purity sulfuric acid is used as an auxiliary to keep the pH value of the electrolyte at about 3.0; the electrodeposition is stopped after 96 h, the plate is stripped, and a metal iron plate with a thickness of 3-5 mm is obtained; wherein the electrolyte after electrodeposition is supplemented and adjusted in acidity before being returned to the electrodeposition cycle for recycling.

[0047] (4) hydrogen reduction and purification: the prepared metal iron plate is placed in a hydrogen reduction furnace, hydrogen is introduced for high-temperature treatment, the reduction temperature is 1200 DEG C, the temperature is kept for 4 h, the iron plate is taken out after cooling, and vacuum packaging is performed.

[0048] The GDMS impurity components of the high-purity metal iron prepared in each embodiment of the present application are shown in Table 1, and the total content of metal impurity components and the content of non-metal impurity components are both low, meeting the index requirements of 5N high-purity metal iron.

[0049] Table 1

[0050]

[0051]

[0052] The method of the present application uses ion-exchange purified ferrous sulfate solution as electrolyte, an ultrasonic generator is installed at the bottom of the electrodeposition tank, high-purity metal iron is prepared by ultrasonic electrodeposition method, the high-temperature hydrogen reduction treatment of the prepared iron plate further reduces the content of low-melting-point metal and gas impurities, and 5N high-purity metal iron with a purity of 99.999% is obtained. The method of the present application avoids the problems of conventional electrodeposition methods, such as serious hydrogen evolution, poor toughness of the cathode iron plate, high oxygen content, easy plugging of the anode filter cloth bag affecting current efficiency, etc., and the prepared iron plate does not need subsequent treatment and can be stored for a long time without rusting. The method has simple process, short flow, high product quality, and good economic and social benefits.

[0053] The above describes the preferred embodiments of the present application, and any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application all fall within the protection scope of the present application.

Claims

1. A method for preparing high-purity metallic iron by ultrasonic cyclic electrowinning, characterized in that: include: Step (1), preparing an electrolyte: dissolving 97% pure iron powder with high-purity sulfuric acid or directly dissolving high-purity ferrous sulfate heptahydrate crystals to prepare an electrolyte with an iron concentration of 60-80 g / L; Step (2), electrolyte purification: the electrolyte in step (1) is passed through an ion exchange resin column at a speed of 3 to 5 BV / h for purification, wherein the ion exchange resin is washed and pretreated with 20 to 30% sulfuric acid solution and pure water in sequence before being loaded into the column; Step (3), ultrasonic cycle electrolysis: install an ultrasonic generator at the bottom of the electrolysis tank, connect the ultrasonic control device to the outside of the electrolysis tank, use pig iron as the electrolytic anode, and use a filter bag as the anode; use stainless steel plate as the cathode, and install an acidity detection probe in the cathode area. The current density is 200-300A / m 2 Ultrasonic electrowinning is carried out, and the electrolyte is dynamically circulated at a circulation rate of 1-3 tanks / h. After a certain thickness of iron layer is deposited, the electrowinning is stopped and the plate is stripped; Step (4), hydrogen reduction purification: the iron plate obtained in step (3) is placed in a hydrogen reduction furnace, hydrogen is introduced for high-temperature treatment, and finally 5N grade high-purity metallic iron with a purity of ≥99.999% is obtained.

2. The method for preparing high-purity metallic iron by ultrasonic cyclic electrowinning according to claim 1, wherein: The ion exchange resin in step (2) is a chelating resin used to remove heavy metal impurity ions such as copper, nickel, cobalt, and zinc in the solution. When the total amount of solution purified by the resin reaches 1000 BV, the resin is washed with about 50% sulfuric acid solution and pure water in sequence, and then returned to the purification link for recycling.

3. The method for preparing high-purity metallic iron by ultrasonic cyclic electrowinning according to claim 1, wherein: The electrolysis temperature in step (3) is 50-70° C., the pH value of the electrolysis process is controlled to be 3-4, the ultrasonic frequency is 500-1000 Hz, and the electrolytic lean solution after electrolysis is supplemented with acid and then returned to electrolysis for recycling.

4. The method for preparing high-purity metallic iron by ultrasonic cyclic electrowinning according to claim 1, wherein: After the iron sheet is subjected to high-temperature hydrogen reduction treatment in step (4), the iron sheet needs to be vacuum-packed and stored.

5. The method for preparing high-purity metallic iron by ultrasonic cyclic electrowinning according to claim 1, wherein: When the concentration of sodium and potassium ions in the electrolytic lean solution in step (5) is higher than 0.1 g / L, it is no longer recycled and the electrolyte is reconfigured and replaced for electrolysis.

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