WO2016192648A1 - Method for preparing metal magnesium - Google Patents

Abstract

A method for preparing metal magnesium comprises the following steps: providing an ion membrane electrolysis system (10) the comprises a raw material chamber (111), an anode chamber (112), a cathode chamber (113), a cation exchange membrane (12), an anion exchange membrane (13), a cathode (15), and an iron-made anode (14), the anion exchange membrane (13) being located between the raw material chamber (111) and the anode chamber (112), the cation exchange membrane (12) being located between the raw material chamber (111) and the cathode chamber (113), and the iron-made anode (14) and the cathode (15) being respectively disposed in the anode chamber (112) and the cathode chamber (113); filling an anhydrous organic electrolyte, a magnesium chloride hexahydrate solution, and a ferrous chloride aqueous solution in the cathode chamber (113), the raw material chamber (111), and the anode chamber (112) of the ion membrane electrolysis system, respectively; and applying an electrolytic voltage between the iron-made anode (14) and the cathode (15), to obtain metal magnesium and a concentrated ferrous chloride aqueous solution. Therefore, the foregoing method for preparing metal magnesium has advantages of low consumption of energy and cost and environmental friendliness.

Description

Method for preparing magnesium metal Technical field

This invention relates to a wet metallurgy process, and more particularly to a process for the preparation of magnesium metal.

Background technique

Silver-white metallic magnesium is a lightweight structural material. It is often alloyed with aluminum, manganese, zinc, rare earth metals, etc., based on its light weight, high specific strength and easy recovery. Therefore, magnesium alloy can be widely used in automotive parts and housings of portable electronic products.

The prior art methods for preparing magnesium metal include molten salt electrolysis and ferrosilicon thermal reduction. The molten salt electrolysis method is to obtain molten magnesium and chlorine by electrolyzing molten anhydrous magnesium chloride at a reduction temperature of about 700 °C. The ferrosilicon thermal reduction method uses dolomite as a raw material in a vacuum reduction tank, and uses ferrosilicon as a reducing agent to reduce magnesium oxide in the dolomite to magnesium vapor at a reduction temperature of about 1200 ° C, and then passes through a condenser. Magnesium vapor is condensed to produce metallic magnesium.

However, the molten salt electrolysis method consumes about equivalent to 20 kilowatts (kW) of energy for preparing 1 kilogram of metallic magnesium, and the ferrosilicon thermal reduction method requires about 1 kilogram (kg) of magnesium metal to be consumed. It is effective for 24 kW, and the molten salt electrolysis method and the ferrosilicon thermal reduction method require a relatively high reduction temperature to produce magnesium metal. Therefore, the production of magnesium metal by molten salt electrolysis and ferrosilicon thermal reduction requires a large amount of consumption. Energy and cost.

Furthermore, the production of metallic magnesium by molten salt electrolysis produces a large amount of chlorine gas, and the production of metallic magnesium by the ferrosilicon thermal reduction method emits a large amount of carbon dioxide which is a greenhouse gas, so the prior art uses molten salt electrolysis. And the production of magnesium metal by the ferrosilicon thermal reduction method will cause environmental pollution.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, it is an object of the present invention to provide a method for preparing magnesium metal which has the advantages of low energy consumption and cost and environmental friendliness.

In order to achieve the foregoing object, the technical means adopted by the present invention is that the method for preparing magnesium metal comprises the following steps:

Providing an ion membrane electrolysis system comprising a raw material chamber, an anode chamber, a cathode chamber, a cation exchange membrane, an anion exchange membrane, an iron anode and a cathode, the anion exchange membrane being located between the raw material chamber and the anode chamber The cation exchange membrane is located between the raw material chamber and the cathode chamber, and the iron anode and the cathode are respectively provided In the anode chamber and the cathode chamber;

Injecting an anhydrous organic electrolyte, an aqueous solution of magnesium chloride hexahydrate and an aqueous solution of ferric chloride into the cathode chamber, the raw material chamber and the anode chamber, respectively;

An electrolytic voltage is applied between the iron anode and the cathode to obtain metallic magnesium and a concentrated aqueous solution of ferric chloride.

In the method for producing magnesium metal, the amount of ferric chloride contained in the concentrated aqueous solution of ferric chloride is more than the amount of ferric chloride contained in the aqueous solution of ferric chloride.

In the method of producing magnesium metal, the iron anode refers to an iron anode containing at least 99.95 weight percent (wt%) of iron. Preferably, the iron anode has an iron content of at least 99.98% by weight.

In the method for preparing magnesium metal, preferably, the iron anode contains carbon and iron, and the iron anode has a carbon content of 0.02 wt% to 0.05 based on the total weight of the iron anode. Between wt%.

In the method of producing magnesium metal, preferably, the cathode of the ion-exchange membrane electrolysis system is made of stainless steel, glassy carbon or carbon aerogel.

In the method for producing magnesium metal, preferably, the anhydrous organic electrolyte solution comprises a solvent, an organomagnesium electrolyte, and a supporting electrolyte, the solvent comprising selected from the group consisting of ethyl ether, tetrahydrofuran, and 2- An ether compound in the group consisting of 2-methyltetrahydrofuran and cyclopentyl methyl ether, the organomagnesium electrolyte comprising selected from the group consisting of methyl magnesium chloride, Magnesium organic compound in the group consisting of ethyl magnesium chloride, phenyl magnesium chloride, alkoxy magnesium bromide and alkoxy magnesium chloride The supporting electrolyte comprises aluminum chloride or lithium perchlorate.

More preferably, the organomagnesium electrolyte is 0.8 mol/L (mol/L) to 2.0 mole/L based on the total amount of the anhydrous organic electrolyte, and the supporting electrolyte is 0.10 mol/L to 0.20 mol/ L. Still preferably, the organomagnesium electrolyte is from 1.0 mol/L to 1.5 mol/L, and the supporting electrolyte is from 0.12 mol/L to 0.15 mol/L, based on the total amount of the anhydrous organic electrolyte.

In the method for producing magnesium metal, preferably, the ferric chloride contained in the aqueous solution of ferric chloride is from 0.3 mol/L to 0.5 mol/L based on the total amount of the aqueous solution of ferric chloride. . More preferably, the ferric chloride contained in the aqueous solution of ferric chloride is from 0.4 mol/L to 0.5 mol/L based on the total amount of the aqueous solution of ferric chloride.

In the method for producing magnesium metal, preferably, the magnesium chloride hexahydrate contained in the aqueous solution of magnesium chloride hexahydrate is from 0.3 mol/L to 0.5 mol/L, based on the total amount of the aqueous solution of magnesium chloride hexahydrate.

In the method of preparing magnesium metal, preferably, the cation exchange membrane may be a perfluorosulfonic acid cation exchange membrane, but is not limited thereto.

In the method of producing magnesium metal, preferably, at least one side of the cation exchange membrane is coated with a magnesium ion conductive solid polymer electrolyte.

In the method of producing magnesium metal, preferably, the anion exchange membrane is a homogeneous anion exchange membrane.

In the method for preparing magnesium metal, preferably, the step of applying the electrolysis voltage between the anode and the cathode of the iron to obtain the metal magnesium and the concentrated aqueous solution of ferric chloride comprises:

Applying a current density of 10 mA/cm ² to 25 mA/cm ^{2 and} an electrolytic voltage of 2 volts (V) to 5 V to the pure iron at a normal pressure, an operating temperature of 20 ° C to 25 ° C The step of obtaining the magnesium metal and the concentrated aqueous solution of ferric chloride is carried out between the anode and the cathode.

In the method of producing magnesium metal, the atmospheric pressure is 1 atm.

Based on the above, the method for preparing magnesium metal can obtain 1 kilogram of metal magnesium by using only 5.2 kilowatts or less of energy, thereby achieving the advantages of saving production energy and cost of metal magnesium. And the method for preparing magnesium metal is the same as producing the concentrated aqueous solution of ferric chloride while producing the magnesium metal, instead of producing a large amount of unfavorable environment such as chlorine gas or carbon dioxide, in addition to reducing the harm to the environment, The ferric chloride in the concentrated aqueous solution of ferric chloride can be further used as a flocculant for the treatment of sewage. Therefore, the method for preparing magnesium metal has the advantages of low energy and cost consumption and environmental friendliness.

DRAWINGS

Figure 1 is a flow chart of a method for preparing magnesium metal according to the present invention;

2 is a schematic view of an ion-exchange membrane electrolysis system used in the method for producing magnesium metal of the present invention.

Symbol Description:

S1, S2, S3 steps

10 ion membrane electrolysis system

11 cavity

111 raw material room

112 anode chamber

113 cathode chamber

12 cation exchange membrane

13 anion exchange membrane

14 iron anode

15 cathode.

detailed description

The technical solutions of the present invention are described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention includes but is not limited thereto.

Referring to FIG. 1, the method for preparing magnesium metal of the present embodiment is completed by the steps described below.

First, referring to FIG. 2, an ion-exchange membrane electrolysis system 10 is provided as described in step S1. The ionic membrane electrolysis system 10 comprises a chamber 11, a cation exchange membrane 12, an anion exchange membrane 13, an iron anode 14 and a cathode 15, the cation exchange membrane 12 being coated with at least one side of a solid polymer electrolyte capable of conducting magnesium ions. Further, the cation exchange membrane 12 is a perfluorosulfonic acid cation exchange membrane 12 of DuPont Chemical Company. The cation exchange membrane 12 and the anion exchange membrane 13 partition the interior of the chamber 11 into a raw material chamber 111, an anode chamber 112, and a cathode chamber 113. The anion exchange membrane 13 is located between the raw material chamber 111 and the anode chamber 112. The exchange membrane 12 is located between the raw material chamber 111 and the cathode chamber 113, and the anion exchange membrane 13 is a homogeneous anion exchange membrane of DuPont Chemical Co., Ltd., and the iron anode 14 and the cathode 15 are respectively disposed in the anode chamber 112 and the cathode chamber. 113. The iron anode 14 contains iron and carbon, and the iron anode 14 has a carbon content of 0.02% by weight based on the total weight of the iron anode 14, and the cathode 15 is made of stainless steel.

Next, as described in step S2, a non-aqueous organic electrolytic solution is injected into the cathode chamber 113, an aqueous solution of magnesium chloride hexahydrate is injected into the raw material chamber 111, and the aqueous solution of ferric chloride is injected into the anode chamber 112. The anhydrous organic electrolyte is composed of a solvent, an organomagnesium electrolyte and a supporting electrolyte, the solvent is tetrahydrofuran, the organomagnesium electrolyte is ethyl magnesium chloride, the supporting electrolyte is aluminum chloride, and the ethyl magnesium chloride is used in an amount of 1.5. The mole, the amount of aluminum chloride used is 0.15 mol, and the amount of the tetrahydrofuran is 1.0 liter (liter, L). The aqueous solution of ferric chloride contains ferric chloride and water, and the molar concentration of the aqueous solution of ferric chloride is 0.4 mol/L. The aqueous solution of magnesium chloride hexahydrate contains magnesium chloride hexahydrate and water, and the molar concentration of the aqueous solution of magnesium chloride hexahydrate is 0.5 mol/L.

Then, as described in step S3, the electrolysis voltage of the direct current power supply is adjusted at a normal pressure and an operating temperature of 25 ° C to achieve a current density of 10 mA/cm ² between the iron anode 14 and the cathode 15 for 1 hour, thereby Obtaining a non-aqueous organic electrolyte containing magnesium metal in the cathode chamber 113 and obtaining a concentrated aqueous solution of ferric chloride in the anode chamber 112; thereafter, separating the anhydrous organic electrolyte containing magnesium metal to obtain magnesium metal And the separated anhydrous organic electrolyte; wherein, under the condition of a membrane square (m ² ) membrane area, the yield of metallic magnesium is 38.54 g (gram, g), and the concentrated ferric chloride The difference between the content of ferric chloride in the aqueous solution and the ferric chloride in the aqueous solution of ferric chloride is 200.06 g, that is, the method for producing magnesium metal of the present embodiment can produce 200.06 g of ferric chloride.

When an electrolysis voltage is applied between the iron anode 14 and the cathode 15, the iron anode 14 is oxidized to generate iron ions (Fe ²⁺ ) in the aqueous solution of ferric chloride in the anode chamber, and chlorine in the aqueous solution of magnesium chloride hexahydrate The ions (Cl ^- ) migrate into the aqueous solution of ferric chloride in the anode chamber 112 via the anion exchange membrane 13; at the same time, the magnesium ions (Mg ²⁺ ) of the aqueous solution of magnesium chloride hexahydrate in the raw material chamber 111 migrate to the cation exchange membrane 12 to In the cathode chamber 113, two electrons are obtained by the cathode 15 in the anhydrous organic electrolyte to be reduced to magnesium metal, and the two electrons are released when the iron anode 14 is oxidized to iron ions (Fe ²⁺ ). Electronic. The reaction formula of the cathode 15 and the iron anode 14 is as follows:

Cathode: Mg ²⁺ _(aq) +2e ^- →Mg _(s)

Iron anode: Fe _(s) -2e ^- →Fe ²⁺ _(aq)

Fe ²⁺ _(aq) +2Cl ^- _(aq) → FeCl _{2 (aq)}

The actual amount of magnesium metal obtained by the method for producing magnesium metal was 38.54 g, and the method for producing magnesium metal produced iron dichloride (FeCl ₂ ) of 200.06 g. According to theoretical calculations, the theoretical amount of magnesium metal prepared by the above method is 24.5 volts, the current density of 10 mA/cm ² , the working time of 1 hour, and the membrane area of 1 square meter. The output of ferric chloride was 236 grams. From this, it can be inferred that the current efficiency of the method for preparing metallic magnesium is 85%.

Furthermore, the actual amount of metallic magnesium obtained by the method for preparing magnesium metal is 38.54 g and the electrolytic voltage is 2 volts, and it can be known that the method for preparing metallic magnesium produces 1 kg of magnesium metal per method. The power consumption is 5.19 kilowatts, and at the same time, 5.2 kilograms of ferric chloride is produced.

According to the method for preparing magnesium metal, the method for preparing magnesium metal can further make the concentrated aqueous solution of ferric chloride contain more than 5.2 kg of the aqueous solution of ferric chloride, each time 1 kg of metallic magnesium is obtained. Ferric chloride content.

As can be seen from the above, the use of the ion-exchange membrane electrolysis system 10 containing the iron anode 14 is carried out by applying the electrolysis voltage to the iron anode in combination with the use of the anhydrous organic electrolyte solution, the aqueous solution of magnesium chloride hexahydrate and the aqueous solution of ferric chloride. After the process between the 14 and the cathode 15, the method for preparing magnesium metal in the foregoing embodiment can obtain energy and cost by using only 1.19 kilowatts of energy to obtain 1 kilogram of metallic magnesium and the concentrated aqueous solution of ferric chloride. And the method for preparing magnesium metal produces the concentrated aqueous solution of ferric chloride while producing magnesium metal, and does not generate a large amount of gas such as chlorine gas or carbon dioxide, in addition to reducing environmental damage, the concentration The ferric chloride in the aqueous solution of ferric chloride can be further processed into ferric chloride for use as a flocculant for sewage treatment.

In addition, the method for preparing magnesium metal can be applied to a working pressure of normal pressure, an operating temperature of 20 ° C to 25 ° C, a current density of 10 mA / cm ² to 25 mA / cm ² and an electrolytic voltage of 2 volts to 5 volts. There is no need to additionally regulate the working pressure and the operating temperature, and therefore, the method of preparing magnesium metal has the advantage of saving energy.

Claims (12)

A method of preparing magnesium metal, the steps of which comprise: Providing an ion membrane electrolysis system comprising a raw material chamber, an anode chamber, a cathode chamber, a cation exchange membrane, an anion exchange membrane, an iron anode and a cathode, the anion exchange membrane being located between the raw material chamber and the anode chamber The cation exchange membrane is located between the raw material chamber and the cathode chamber, and the iron anode and the cathode are respectively disposed in the anode chamber and the cathode chamber; Injecting an anhydrous organic electrolyte, an aqueous solution of magnesium chloride hexahydrate and an aqueous solution of ferric chloride into the cathode chamber, the raw material chamber and the anode chamber, respectively; An electrolytic voltage is applied between the iron anode and the cathode to obtain metallic magnesium and a concentrated aqueous solution of ferric chloride. A method of producing magnesium metal according to claim 1, wherein the iron anode contains at least 99.95 wt% of iron based on the entirety of the iron anode of the ion membrane electrolysis system. A method of producing magnesium metal according to claim 1, wherein the cathode of the ion-exchange membrane electrolysis system is made of stainless steel, vitreous carbon or carbon aerogel. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the anhydrous organic electrolytic solution comprises a solvent, an organomagnesium compound electrolyte, and a supporting electrolyte, the solvent comprising selected from the group consisting of diethyl ether, An ether compound in the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, and cyclopentyl methyl ether, the organomagnesium compound electrolyte comprising selected from the group consisting of methyl magnesium chloride, ethyl magnesium chloride, phenyl magnesium chloride, and alkyl bromide A magnesium organic compound in the group consisting of magnesium and alkoxymagnesium chloride, the supporting electrolyte comprising aluminum chloride or lithium perchlorate. The method for producing magnesium metal according to claim 4, wherein the organomagnesium compound electrolyte is from 0.8 mol/L to 2.0 mol/L based on the total amount of the anhydrous organic electrolyte. The method of producing magnesium metal according to claim 5, wherein the supporting electrolyte is from 0.10 mol/L to 0.20 mol/L based on the total amount of the anhydrous organic electrolyte. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the ferric chloride contained in the aqueous solution of ferric chloride is based on the total amount of the aqueous solution of ferric chloride It is from 0.3 mol/L to 0.5 mol/L. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the magnesium chloride hexahydrate contained in the aqueous solution of magnesium chloride hexahydrate is 0.3 mol based on the total amount of the aqueous solution of magnesium chloride hexahydrate. /L to 0.5mol/L. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the cation exchange membrane is coated with a magnesium ion conductive solid polymer electrolyte. A method of producing magnesium metal according to claim 9, wherein the cation exchange membrane is a perfluorosulfonic acid cation exchange membrane. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the anion exchange membrane is a homogeneous anion exchange membrane. The method for producing magnesium metal according to any one of claims 1 to 3, wherein the electrolytic voltage is applied between the anode and the cathode of the pure iron to obtain the metallic magnesium and the concentrated ferric chloride. The steps of the aqueous solution include: Applying a current density of 10 mA/cm ² to 25 mA/cm ² and an electrolysis voltage of 2 volts to 5 volts between the anode and the cathode of the pure iron at an atmospheric pressure and an operating temperature of 20 ° C to 25 ° C to obtain the metal. Magnesium and the concentrated aqueous solution of ferric chloride.

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