Method for preparing high-purity manganese metal through double-system electrolysis

Abstract

The invention relates to the technical field of electrolytic manganese, in particular to a method for preparing high-purity metal manganese through double-system electrolysis. The method comprises the following steps: preparing cathode and anode electrolytes; purification: purifying the prepared catholyte by using an ion exchange method; and double-system electrolysis: manufacturing a cylindrical rotational flow electrolytic bath, separating a cathode and an anode by using a bipolar membrane, forming an anode area inside and a cathode area outside, using a thin cylindrical titanium plate as the cathode, using a titanium iridium-plated rod or net as the anode, using a manganese chloride-ammonium chloride mixed solution as the catholyte, using an ammonium sulfate solution as the anolyte, and electrolyzing to prepare high-purity metal manganese. According to the method, the high-purity metal manganese with the purity larger than 99.999% is prepared through rotational flow low-temperature electrolysis, the problems that according to a conventional electrolytic method, hydrogen evolution is serious, low-temperature ionic conductivity is poor, plate forming is not prone to occurring or the plate forming quality is poor are solved, the hidden danger of nitrogen trichloride explosion is eliminated, the manganese recovery rate is high, and the product quality is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolytic manganese, in particular to a method for preparing high-purity metallic manganese by double-system electrolysis. BACKGROUND

[0002] In recent years, the electronic, semiconductor, communication and other industries in China have developed rapidly, and the process of integrated circuit chips is becoming smaller and smaller. The purity requirement of high-purity metallic manganese is becoming higher and higher, and the market demand for high-purity metallic manganese is gradually increasing.

[0003] At present, the preparation process of high-purity metallic manganese is generally electrolysis, and most of the high-purity metallic manganese prepared by sulfuric acid electrolysis has a purity of 3N5-4N. High-purity metallic manganese with a purity of 4N or more is generally prepared by single low-temperature chlorination system electrolysis.

[0004] Anode reaction: 2Cl - -2e→Cl2↑

[0005] Cathode reaction: Mn 2+ +2e→Mn; Mn 2+ +2H2O-2e→MnO2+4H + ; 2H2O+2e→H2↑+2OH -

[0006] The static electrolysis of the chlorination system has the following disadvantages: (1) When the low-temperature chlorination system is electrolyzed, ammonium chloride and manganese chloride mixed solution is used as the electrolyte. Chlorine gas is generated by the anode discharge of chloride ions at low temperature electrolysis, and hydrogen gas is generated at the cathode. The production environment is seriously polluted by chlorine gas, and the operating environment is poor; (2) The chlorine gas generated at the anode needs to be treated subsequently, which is high in cost; (3) The mixture of chlorine gas and hydrogen gas is dangerous; (4) The ammonium ion or free ammonia in the solution is oxidized to nitrogen tri-chloride by chlorine gas. When nitrogen tri-chloride accumulates to a certain extent in the electrolyte, it is easy to explode; (5) A large amount of manganese dioxide is generated during the anode electrolysis process, which reduces the current efficiency and affects the quality of high-purity manganese products; (6) The deposition potential of manganese is relatively negative, and it is not easy to grow plates in static state. The hydrogen evolution at the cathode during electrolysis is serious, which affects the plate formation and quality of manganese plates; (7) Hydrogen evolution causes the pH value of the cathode electrolyte to continuously rise, causing manganese in the solution to precipitate as manganese hydroxide. The precipitated particles can cause defects such as nodules on the manganese plates, and the cathode solution needs to be continuously acidified to adjust the pH value of the electrolyte to the appropriate range. SUMMARY

[0007] Therefore, the present application proposes a method for preparing high-purity metallic manganese by double-system electrolysis in view of the shortcomings of the prior art of electrolytic production of high-purity manganese, which is as follows:

[0008] A method for preparing high-purity metallic manganese by double-system electrolysis, comprising the following steps:

[0009] Step 1: Preparation of electrolyte: battery-grade manganese chloride and high-purity ammonium chloride are mixed and dissolved in pure water to prepare the cathode electrolyte; high-purity ammonium sulfate is mixed with pure water to prepare the anode electrolyte;

[0010] Step 2: Purification of the cathode electrolyte by ion exchange method;

[0011] Step 3: Preparation of a cyclone electrolytic cell: titanium iridium plating material is used as the anode and fixed in the middle of the cyclone electrolytic cell, and a bipolar membrane is used to separate the inner circle and the outer circle of the cyclone electrolytic cell: the inner circle space is the anode area, filled with anode electrolyte; the outer circle space is the cathode area, filled with purified cathode electrolyte; a rectangular titanium plate is rolled into a barrel shape around the anode as the cathode, and the interface of the titanium plate is clamped and fixed with a strip; a power circulation device is added to the cathode area to make the cathode electrolyte circulate and form a cyclone on the cathode; the cathode area and the anode area are separated above the liquid surface and are respectively connected to a gas extraction device to extract the gas generated in the anode and cathode areas respectively to prevent the mixing of the generated gas;

[0012] Step 4: Electrolysis: the cathode and anode are respectively connected to the negative and positive electrodes of the power supply, the current density is 200-300 A / m2, the electrolysis temperature is -10℃-10℃, the cathode electrolyte circulation speed is 3-5 h / cell, and the electrolysis process is assisted by high-purity hydrochloric acid to maintain the pH value of the cathode electrolyte at 6.0-8.0.

[0013] Further, in step 1, the concentration of manganese in the cathode electrolyte is 40-120 g / L, and the concentration of ammonium chloride is 1.5-2.5 mol / L; the concentration of ammonium sulfate in the anode electrolyte is 0.5-1.3 mol / L.

[0014] Further, in step 2, the ion exchange method uses chelating resin, and the cathode electrolyte is purified at a speed of 1-3 BV / h through the chelating resin to remove heavy metal impurity ions such as copper, iron, nickel, cobalt, and zinc in the cathode electrolyte; the used chelating resin is regenerated with hydrochloric acid and then washed with pure water.

[0015] Further, in the electrolysis process of step 4, when the concentration of manganese ions in the cathode area is less than 40 g / L, the cathode electrolyte is supplemented.

[0016] Further, in the electrolysis process of step 4, when the concentration of hydrogen ions in the anode area is greater than 1 mol / L, the anode electrolyte is replaced or ammonia water is added to the anode area.

[0017] Further, in the electrolysis process of step 4, when the concentration of sodium and / or potassium ions in the cathode area is higher than 0.1 g / L, the cathode electrolyte is replaced to prevent impurities from affecting the quality of the electrolytic manganese product.

[0018] The method for preparing manganese metal by double-system electrolysis of the application uses a cylindrical cyclone electrolytic cell, a bipolar membrane is arranged in the cell to separate the cathode and anode electrode solutions, and electrolysis processes of two systems are formed in the cathode and anode areas. The power is used to rotate the cathode area for cyclone electrolysis, and the anode area is static electrolysis.

[0019] (1) First, the bipolar membrane is a kind of anion-cation composite ion membrane. The bipolar membrane can only pass hydrogen ions and hydroxyl ions generated by electrolysis of water, and hardly pass other anions and cations. That is, the anions such as chloride ions and the cations such as ammonium and manganese ions in the cathode solution cannot reach the anode, and the sulfate and ammonium in the anode solution cannot reach the cathode. Therefore, a large amount of acid generated by the anode will not greatly affect the pH of the cathode, and the hydrogen ions and hydroxyl ions generated by water ionization in the bipolar membrane enter the cathode solution and the anode solution to neutralize the hydrogen ions generated by the anode and the hydroxyl ions generated by the cathode electrolysis, thereby reducing the amount and frequency of the use of acid and alkali for adjusting the pH of the electrolyte, and the electrolyte environment is more stable, the operation is simpler, the process conditions are easier to control, and the electrolysis system is stable.

[0020] (2) At the same time, the impurities in the anode solution will not affect the cathode product, and the manganese in the cathode solution will not enter the anode to reduce the concentration of manganese ions, thereby avoiding aggravation of polarization in the electrolysis process. Therefore, the anode solution does not need to be deeply purified and impurities removed, thereby reducing the solution treatment amount and the treatment cost. In the system, the anode does not produce manganese dioxide precipitation, does not consume high-purity manganese ions, and the precipitation particles do not affect the quality of the manganese plate.

[0021] (3) Second, in the double-system electrolysis process, the chloride ions in the cathode solution cannot enter the anode, nitrogen trichloride is not generated, and there is no danger of explosion in the electrolysis process, thereby greatly improving the safety factor, improving the operating environment, and eliminating the need for chlorine treatment.

[0022] (4) In the cyclone electrolysis in the cathode area, the rotation and flow of the cathode solution impact the cathode plate, which is beneficial to relieve the polarization of manganese ions near the cathode plate when the plate is formed, and is also beneficial to reduce the discharge opportunity of hydrogen and the probability of hydrogen evolution, thereby being beneficial to the formation of the manganese plate. In addition, the rotation and flow of the cathode solution impact the cathode plate, which can make the hydrogen gas quickly discharged from the cathode electrolyte, thereby avoiding hydrogen embrittlement of the electrolytic manganese plate and affecting the quality of the manganese plate. At the same time, since the cathode solution is circulated, a small amount of nitrogen trichloride generated can be immediately decomposed, thereby avoiding danger. The flow of the cathode solution also reduces the concentration polarization, which is beneficial to the plate formation.

[0023] The method of the present invention can prepare high-purity metallic manganese with a purity greater than 99.999% by low-temperature electrolysis, avoiding the problems of serious hydrogen evolution, difficulty in forming plates and poor plate quality in the preparation of high-purity metallic manganese by low-temperature electrolysis in a chlorination system. The process does not generate chlorine gas, thus avoiding the potential explosion hazard of nitrogen trichloride. No manganese dioxide is generated at the anode to consume manganese ions in the solution, thus reducing the amount of slag treatment and improving the utilization rate of manganese. The process is simple, the product quality is high, and the economic and social benefits are good. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

[0025] Figure 1 The process flow chart of preparing high-purity manganese metal in an embodiment of the present invention is shown;

[0026] Figure 2 It shows the reaction process of water molecules in the water layer of the bipolar membrane under the action of direct current. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] A method for preparing high-purity metallic manganese by dual-system electrolysis comprises the following steps:

[0029] Step 1: Prepare the electrolyte: Battery-grade manganese chloride and high-purity ammonium chloride are mixed and dissolved in pure water to prepare a cathode electrolyte (i.e., cathode liquid); high-purity ammonium sulfate is added to pure water to prepare an anolyte (i.e., anolyte); the manganese concentration in the cathode electrolyte is 40-120 g / L, the ammonium chloride concentration is 1.5-2.5 mol / L; and the ammonium sulfate concentration in the anolyte is 0.5-1.3 mol / L;

[0030] Step 2: The cathode electrolyte is purified by ion exchange method; the ion exchange method uses chelating resin-M resin, and the cathode electrolyte is purified by passing the chelating resin at a rate of 1-3BV / h. The used chelating resin is regenerated with hydrochloric acid and then washed with pure water;

[0031] Step 3: making a rotating flow electrolytic cell: a titanium plated iridium material is used as an anode and fixed in the middle of the rotating flow electrolytic cell, and a bipolar membrane is used to separate the inner circle and the outer circle of the rotating flow electrolytic cell: the inner circle space is an anode area, which is filled with an anode electrolyte; the outer circle space is a cathode area, which is filled with a purified cathode electrolyte; a rectangular titanium plate is wound into a barrel shape around the anode as a center and placed in the cathode area, the titanium plate is a cathode, and a side bar is added to the interface of the titanium plate to clamp and fix it, and a power circulation device, i.e. a circulating pump, is added to the cathode area to make the cathode electrolyte flow and form a rotating flow on the cathode; the cathode area and the anode area are separated above the liquid level and respectively connected with a gas extraction device;

[0032] Step 4: electrolysis: the cathode and the anode are respectively connected with the negative pole and the positive pole of a power supply, the current density is 200-300 A / m 2 , the electrolysis temperature is -10℃-10℃, the cathode electrolyte circulation speed is 3-5 h / tank, and a high-purity hydrochloric acid is used to assist the electrolysis process to keep the pH value of the cathode electrolyte at 6.0-8.0. When the concentration of manganese ions in the cathode area is lower than 40 g / L, the cathode electrolyte is supplemented; when the concentration of hydrogen ions in the anode area is greater than 1 mol / L, the anode electrolyte is replaced or ammonia water is added to the anode area; when the concentration of sodium and / or potassium ions in the cathode area is higher than 0.1 g / L, the cathode electrolyte is replaced.

[0033] The reaction principle is as follows:

[0034] Anode reaction: 2H2O-4e→4H + +O2↑;

[0035] Cathode reaction: Mn 2+ +2e→Mn;2H2O+2e→H2↑+2OH -

[0036] Example 1

[0037] (1) Preparation of electrolyte: 300 L of a mixed solution with a manganese ion concentration of 40 g / L and an ammonium chloride concentration of 1.5 mol / L is prepared by using battery-grade manganese chloride and ammonium chloride, and 30 L of a 0.5 mol / L ammonium sulfate solution is prepared by using high-purity ammonium sulfate and stirring uniformly for standby;

[0038] (2) Purification: the prepared cathode electrolyte is purified by M resin, the purified resin is regenerated by hydrochloric acid, and pure water is washed;

[0039] (3) Rotating flow electrolysis: the bipolar membrane is installed in the electrolytic cell, the anode and the cathode are fixed, a certain liquid level of the purified cathode electrolyte is added to the cathode, and the ammonium sulfate solution is added to the anode. The cathode electrolyte is cooled to a low temperature of about -10℃ for low-temperature electrolysis to prepare high-purity manganese; the cathode plate is a titanium plate, and the anode is a titanium plated iridium rod, and the current density is 300 A / m 2, the cathode electrolyte circulation speed is 5h / cell; the cathode liquid pH value is 7.5-8.0, the electrolysis time is 72h, and the high-purity manganese plate with the purity of more than 99.999% is obtained.

[0040] Example 2

[0041] (1) Preparation of electrolyte: 100L of mixed solution with a manganese ion concentration of 80g / L and an ammonium chloride concentration of 2.0mol / L is prepared by using battery-grade manganese chloride and ammonium chloride, and 10L of ammonium sulfate solution with a concentration of 1.3mol / L is prepared by using high-purity ammonium sulfate and is stirred uniformly for standby;

[0042] (2) Purification: the prepared cathode electrolyte is purified by M resin, the purified resin is regenerated by hydrochloric acid, and is washed by pure water;

[0043] (3) Cyclone electrolysis: the bipolar membrane is installed in the cyclone electrolytic cell, the purified cathode electrolyte is added to the cathode to a certain liquid level, and the prepared ammonium sulfate solution is added to the anode. The cathode electrolyte is cooled to a temperature of 0℃ for low-temperature electrolysis to prepare high-purity manganese; the cathode plate is made of titanium plate, the anode plate is made of titanium plated with ruthenium mesh, and the current density is 250A / m 2 ; the cathode electrolyte circulation speed is 4h / cell; the cathode liquid pH value is 6.5-7.0, the electrolysis time is 60h, and the high-purity manganese plate with the purity of more than 99.999% is obtained.

[0044] Example 3

[0045] (1) Preparation of electrolyte: 500L of mixed solution with a manganese ion concentration of 120g / L and an ammonium chloride concentration of 2.3mol / L is prepared by using battery-grade manganese chloride and ammonium chloride, and 50L of ammonium sulfate solution with a concentration of 1.0mol / L is prepared by using high-purity ammonium sulfate and is stirred uniformly for standby;

[0046] (2) Purification: the prepared cathode electrolyte is purified by M resin, the purified resin is regenerated by hydrochloric acid, and is washed by pure water;

[0047] (3) Cyclone electrolysis: the bipolar membrane is installed in the cyclone electrolytic cell, the purified cathode electrolyte is added to the cathode to a certain liquid level, and the prepared ammonium sulfate solution is added to the anode. The cathode electrolyte is cooled to a temperature of 5℃ for low-temperature electrolysis to prepare high-purity manganese; the cathode plate is made of titanium plate, the anode plate is made of titanium plated with ruthenium mesh, and the current density is 200A / m 2 ; the cathode electrolyte circulation speed is 3h / cell; the cathode liquid pH value is 6.0-6.5, the electrolysis time is 48h, and the high-purity manganese plate with the purity of more than 99.999% is obtained.

[0048] The above describes some exemplary embodiments of the present application, it can be understood that the above-described embodiments are only used to explain the present application, and do not constitute a limitation on the protection scope of the present application. The features in these embodiments can be recombined in a suitable manner, and the schemes obtained thereby are still within the protection scope required by the present application. Based on the above-described embodiments, all other embodiments obtained by those skilled in the art without making creative labor, i.e. all modifications, equivalent replacements and improvements, etc. made within the spirit and principles of the present application, are also within the protection scope required by the present application.

Claims

1. A method for preparing high-purity metallic manganese by dual-system electrolysis, characterized in that: The following steps are involved: Step 1: Prepare the electrolyte: Dissolve battery-grade manganese chloride and high-purity ammonium chloride in pure water to prepare the cathode electrolyte. High-purity ammonium sulfate and pure water are added to prepare the anolyte; Step 2: Purify the cathode electrolyte using ion exchange method; Step 3: Fabricate a cyclone electrolytic cell: Use titanium-plated iridium as the anode and fix it in the middle of the cyclone electrolytic cell. Use a bipolar membrane to separate the inner and outer circles in the cyclone electrolytic cell. The inner circle is the anode area, filled with anolyte; the outer circle is the cathode area, filled with purified catholyte. A rectangular titanium plate is rolled into a barrel shape with the anode as the center and placed in the cathode area. The titanium plate serves as the cathode. Edge strips are added to the interface of the titanium plate to clamp and secure it. A power circulation device is added to the cathode area to circulate the catholyte, forming a cyclone on the cathode. The cathode and anode areas are separated above the liquid surface and are each connected to an exhaust device. Step 4: Electrolysis: Connect the cathode and anode to the negative and positive poles of the power supply respectively, with a current density of 200-300A / m 2 The electrolysis temperature is -10°C to 10°C, the cathode electrolyte circulation speed is 3-5h / cell, and high-purity hydrochloric acid is used to assist in the electrolysis process so that the pH value of the cathode electrolyte is maintained at 6.0-8.

0. The purity of the prepared high-purity manganese metal is greater than 99.999%.

2. The method for preparing high-purity manganese metal by dual-system electrolysis according to claim 1, characterized in that: In step 1, the concentration of manganese in the cathode electrolyte is 40-120 g / L, the concentration of ammonium chloride is 1.5-2.5 mol / L; and the concentration of ammonium sulfate in the anode electrolyte is 0.5-1.3 mol / L.

3. The method for preparing high-purity manganese metal by dual-system electrolysis according to claim 1, characterized in that: In the step 2, the ion exchange method uses a chelating resin, and the cathode electrolyte is purified by passing the chelating resin at a speed of 1-3 BV / h. The used chelating resin is regenerated with hydrochloric acid and then washed with pure water.

4. The method for preparing high-purity manganese metal by dual-system electrolysis according to claim 1, characterized in that: During the electrolysis process of step 4, the cathode electrolyte is added when the manganese ion concentration in the cathode region is lower than 40 g / L.

5. The method for preparing high-purity metallic manganese by dual-system electrolysis according to claim 1, characterized in that: During the electrolysis process of step 4, when the hydrogen ion concentration in the anode region is greater than 1 mol / L, the anode electrolyte is replaced or ammonia water is added to the anode region.

6. The method for preparing high-purity metallic manganese by dual-system electrolysis according to claim 1, characterized in that: During the electrolysis process of step 4, when the concentration of sodium and / or potassium ions in the cathode region is higher than 0.1 g / L, the cathode electrolyte is replaced.

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