阅读说明：本技术 一种制备高纯镁铝尖晶石前驱体的方法 (Method for preparing high-purity magnesia-alumina spinel precursor ) 是由 李亚琼 张立峰 于 2021-01-12 设计创作，主要内容包括：本发明公开了一种制备高纯镁铝尖晶石前驱体的方法,属于高纯镁铝尖晶石制备技术领域。本发明选用高纯铝镁合金作为阳极板,经过电辅助转化和外场作用,同时用多孔膜过滤阳极杂质,得到镁铝氢氧化物沉淀,再将其先后经过滤、洗涤和干燥处理得到高纯镁铝尖晶石前驱体；多孔膜可避免阳极杂质对电解产物镁铝氢氧化物的污染,外场不仅促进Al～(3+)、Mg～(2+)穿过多孔膜,提高电解速率和效率,还可以而控制镁铝氢氧化物从阴极脱落的时机,防止其长大,确保尺寸的均一性,实现对生成的镁铝尖晶石前驱体粉体粒度的控制；生产过程中产生的阳极泥可制备铝镁合金副产品,阴极产生氢气副产品,均可以增加技术的经济性。(The invention discloses a method for preparing a high-purity magnesia-alumina spinel precursor, belonging to the technical field of high-purity magnesia-alumina spinel preparation. The method comprises the steps of selecting high-purity aluminum-magnesium alloy as an anode plate, filtering impurities of the anode by a porous membrane under the action of electric auxiliary conversion and an external field to obtain magnesium-aluminum hydroxide precipitate, and filtering, washing and drying the magnesium-aluminum hydroxide precipitate to obtain a high-purity magnesium-aluminum spinel precursor; the porous membrane can avoid the pollution of anode impurities to the magnesium aluminum hydroxide serving as an electrolyte product, and the external field not only promotes Al 3+ 、Mg 2+ Through the porous membrane, the electrolysis speed and efficiency are improved, the falling time of the magnesium aluminum hydroxide from the cathode can be controlled, the growth of the magnesium aluminum hydroxide is prevented, and the uniformity and the practicability of the size are ensuredControlling the granularity of the generated magnesia-alumina spinel precursor powder; the anode mud generated in the production process can be used for preparing an aluminum magnesium alloy byproduct, and the cathode generates a hydrogen byproduct, so that the technical economy can be improved.)

1. A method for preparing high-purity magnesia-alumina spinel precursor is characterized by comprising the following steps: selecting high-purity aluminum-magnesium alloy as an anode plate (112), obtaining a magnesium-aluminum hydroxide precipitate product (121) under the action of electric auxiliary conversion and an external field (300), and filtering, washing and drying the magnesium-aluminum hydroxide precipitate product (121) to obtain a high-purity magnesium-aluminum spinel precursor.

2. The method for preparing high-purity magnesia-alumina spinel precursor of claim 1, which comprises the following steps:

step one, preparation of an anode plate (112)

Heating high-purity aluminum and high-purity magnesium to be molten, casting the molten high-purity aluminum and high-purity magnesium into a magnesium-aluminum alloy plate, and polishing and cleaning the surface of the magnesium-aluminum alloy plate to obtain an anode plate (112);

step two, electric auxiliary transformation

Constructing an electrolysis unit (100) by using the anode plate (112) obtained in the step one as an anode, using an inert material (123) as a cathode and using an acidic solution (130) as an electrolyte, and converting the anode plate (112) into a magnesium aluminum hydroxide precipitation product (121) in the electrolysis unit (100);

step three, reinforced stripping

Applying an external field (300) to the electrolysis unit (100) in the second step to promote the peeling of the magnesium aluminum hydroxide precipitation product (121) on the cathode;

the fourth step: separating and drying

And (4) filtering, separating, cleaning and drying the magnesium aluminum hydroxide precipitate product (121) obtained in the step three to obtain a high-purity magnesium aluminum spinel precursor.

3. The method for preparing high-purity magnesium aluminate spinel precursor according to claim 2, wherein the purity of the high-purity magnesium aluminate alloy in the first step is 99-99.999% and the molar ratio of magnesium to aluminum is 1: 2-1: 4. The anode plate (112) is prepared by the following specific steps: melting high-purity aluminum and high-purity magnesium, casting the molten high-purity aluminum and high-purity magnesium into a magnesium-aluminum alloy plate, polishing the surface of the magnesium-aluminum alloy plate, then carrying out ultrasonic cleaning, drying and then placing the magnesium-aluminum alloy plate in an inert gas environment for storage.

4. The method for preparing high-purity magnesia-alumina spinel precursor of claim 2, wherein: the electrolytic cell in the second step also comprises a porous membrane (200), the electrolytic cell is divided into an anode electrolytic cell (110) and a cathode electrolytic cell (120) by the porous membrane (200), and the pore diameter of the porous membrane (200) is 0.1-100 nm.

5. The method for preparing high-purity magnesia-alumina spinel precursor of claim 2, wherein: the acidic solution (130) in the second step is one or more of hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, the molar concentration is 0.1-18.4 mol/L, and the pH value is 0.1-6.9.

6. The method for preparing high-purity magnesia-alumina spinel precursor of claim 2, wherein: in the second step, the area ratio of the inert material (123) to the anode plate (112) is 1-2, the distance between the cathode and the anode is 10-100 mm, and the surface roughness of the inert material (123) is 1-10 mu m.

7. The method for preparing high-purity magnesia-alumina spinel precursor of claim 2, wherein: the electrolytic cell in the second step adopts a direct current power supply or a pulse power supply; the cell voltage of the direct current power supply electrolytic cell is 0.1-4.5V, and the cathode current density is 0.01-1A/cm²(ii) a The pulse frequency of the pulse power supply is 100-2000 Hz, and the duty ratio is 3% -97%.

8. The method for preparing high-purity magnesia-alumina spinel precursor of claim 7, wherein: the external field (300) is an electric field or an ultrasonic field, and the external field (300) is coupled with a power supply adopted by the electrolytic cell.

9. The method for preparing high-purity magnesia-alumina spinel precursor of claim 8, wherein: the voltage of the electric field is 0.1-4.5V; the ultrasonic frequency of the ultrasonic field is 20-3000 kHz, and the ultrasonic power is 0-4000W.

10. A method of preparing a high purity magnesia alumina spinel precursor of any of claims 8 or 9, wherein: the external field (300) is applied in a continuous or intermittent manner.

Technical Field

The invention relates to the technical field of high-purity magnesium aluminate spinel preparation, in particular to a method for preparing a high-purity magnesium aluminate spinel precursor.

Background

The transparent ceramic material belongs to a large category of advanced ceramics, has excellent high light transmittance, has the outstanding characteristics of high strength, high hardness, corrosion resistance, high temperature resistance and the like of structural ceramics, has wide application prospect on energy-saving, medical, laser, detection, exploration and other equipment for military and civil use, and is one of the top material hotspots of the current world science and technology front.

In order to ensure the transparence of the ceramic material, the first task is to use high-purity raw materials, which is one of the important reasons that related materials in China are almost all imported. The breakthrough of the neck problem can be realized only by stably preparing high-purity raw materials at low cost and then optimizing key parameters of sintering and other processes. Wherein the high-purity alumina is an important material for preparing transparent ceramics, sapphire, diaphragm coatings and the like, and becomes one of high-end new materials with high yield, high output value and wide application.

At present, the preparation method of the high-purity magnesia-alumina spinel mainly comprises the following steps:

the solid phase method includes a high temperature solid phase method and a combustion synthesis method, and the former method includes, for example, chinese patent application No.: 201210183801.7, filing date: 6.6.2012, the name of invention creation: the application discloses a method for preparing magnesia-alumina spinel powder by a low-temperature solid-phase reaction method, which specifically comprises the following steps: weighing raw materials containing aluminum and magnesium according to the stoichiometric ratio of the magnesium aluminate spinel, pretreating the weighed raw materials by one of dry pretreatment, wet pretreatment, salt hydrolysis pretreatment or salt precipitation pretreatment to obtain mixture powder called a precursor, and carrying out heat treatment or roasting on the precursor at 900-1200 ℃ to obtain pure-phase magnesium aluminate spinel powder with good dispersibility, wherein part of particles are in the shape of a regular octahedron. The synthesis method has a simple process, but the synthesis temperature of the magnesium aluminate spinel is often reduced by adding additives, and the purity of the product is influenced to a certain extent by the additives. Meanwhile, the materials after reaction are easy to agglomerateAnd the magnesium aluminate spinel needs to be further ball-milled and crushed into finer particles, so that defects can be introduced, and the purity and the particle size of the magnesium aluminate spinel product are influenced. The latter is synthesized of nanocrystalline magnesium aluminum (MgAl) as published in Materials Research Bulletin journal by Prabohakara K et al 2009₂O₄) The spine pole by the user-format polymer gel distribution route (volume 44, page 613-. The method comprises adding Mg (NO)₃)₂₆H₂O、Al(NO₃)₃·9H₂And carrying out combustion reaction on polymer gel formed by the O and the urea-formaldehyde to obtain a product, and roasting the product at 850 ℃ to obtain the magnesia-alumina spinel powder. The solid phase method has simple process and low cost, but the method is greatly influenced by the purity of raw materials, and the purity of the product needs to be strictly controlled if the high-purity magnesia-alumina spinel product is to be prepared. Meanwhile, the problems of growth and agglomeration of magnesia-alumina spinel particles caused by higher calcining (heat treatment) temperature need to be strictly controlled.

Liquid phase method: including sol-gel methods, thermal decomposition methods, chemical codeposition methods, hydrothermal synthesis methods, and the like. The methods generally comprise the steps of preparing a magnesium aluminate spinel precursor, calcining at high temperature, decomposing into a mixture of metal oxides, and carrying out high-temperature reaction to generate magnesium aluminate spinel powder. For example, upon search as in chinese patent application No.: CN201810037619.8, application date: 1, 15 days in 2018, the invention and creation name is: the application discloses a method for preparing nano magnesia-alumina spinel, which specifically comprises the following steps: firstly, preparing potassium sulfate particles with nanometer sizes, and carrying out surface modification on the potassium sulfate nanoparticles to ensure that the particles are uniformly dispersed in dimethylbenzene. The method comprises the steps of dispersing and isolating carbonate precursor particles of spinel in dimethylbenzene by using nano potassium sulfate, centrifugally precipitating, drying precipitate, calcining at high temperature, and washing with water to obtain the nano magnesia-alumina spinel. The liquid phase method can prepare the magnesia-alumina spinel powder with fine particles, has higher purity, and is the main preparation method of the magnesia-alumina spinel powder at present. However, in the liquid phase method preparation process, the smaller the particle size, the more likely the particle aggregation occurs, the organic surfactant is often required to be added to reduce the particle aggregation, and the use of the organic waste liquid is likely to cause certain environmental pollution, and is not suitable for the preparation of large-scale magnesia-alumina spinel powder, and meanwhile, the control of the particle size uniformity of the powder is difficult.

Disclosure of Invention

1. Technical problem to be solved by the invention

The invention aims to provide a method for preparing a high-purity magnesia-alumina spinel precursor aiming at the problems of agglomeration of powder, uncontrollable purity, strict requirements on process parameters, harsh raw material purity and the like in the process of purifying and preparing high-purity magnesia-alumina spinel in the prior art, the method comprises melting and casting high-purity aluminum and high-purity magnesium into alloy plate as anode, inert material as cathode, and acidic solution as electrolyte, and separating the electrolytic cell into anode electrolytic cell and cathode electrolytic cell with porous membrane, thereby forming an electrolytic cell, applying an external field to strengthen the shedding of the magnesium aluminum hydroxide powder on the cathode during electrolysis, avoiding concentration polarization of the anode, the method can efficiently and cleanly prepare the high-purity magnesia-alumina spinel precursor, and the process is regulated and controlled through electrochemical parameters, so that the process is controllable, the product purity is high, the granularity is controllable, the powder uniformity is controllable, the particle dispersion degree is good, and the efficiency is high.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the method for preparing the high-purity magnesia-alumina spinel precursor selects high-purity magnesia-alumina alloy as an anode plate, obtains a magnesia-alumina hydroxide precipitation product under the action of electric auxiliary conversion and an external field, and then obtains the high-purity magnesia-alumina spinel precursor by filtering, washing and drying the magnesia-alumina hydroxide precipitation product in sequence.

Preferably, the specific steps are as follows:

step one, preparing an anode plate

Heating high-purity aluminum and high-purity magnesium to be molten, casting the molten high-purity aluminum and high-purity magnesium into an aluminum-magnesium alloy plate, and polishing and cleaning the surface of the aluminum-magnesium alloy plate to obtain an anode plate;

step two, electric auxiliary transformation

Taking the anode plate obtained in the step one as an anode, taking an inert material as a cathode and taking an acidic solution as an electrolyte to construct an electrolytic unit, and converting the anode plate into a magnesium aluminate spinel precursor in the electrolytic unit;

step three, reinforced stripping

Applying an external field to the electrolysis unit in the second step to promote the peeling of the magnesium aluminum hydroxide precipitation product on the cathode;

the fourth step: separating and drying

And C, filtering, separating, cleaning and drying the magnesium aluminum hydroxide precipitate obtained in the step three to obtain a high-purity magnesium aluminum spinel precursor.

Preferably, in the first step, the purity of the high-purity aluminum and the high-purity magnesium is 99-99.999%, and the preparation of the anode plate comprises the following specific steps: melting high-purity aluminum and high-purity magnesium, and casting the molten high-purity aluminum and high-purity magnesium into a magnesium-aluminum alloy plate, wherein the molar ratio of magnesium to aluminum is 1: 2-1: 4; and the surface of the magnesium-aluminum alloy plate is polished, then ultrasonic cleaning is carried out, and the magnesium-aluminum alloy plate is dried and then placed in an inert gas environment for storage.

Preferably, the electrolytic cell in the second step further comprises a porous membrane, the porous membrane divides the electrolytic cell into an anode electrolytic cell and a cathode electrolytic cell, and the pore diameter of the porous membrane is 0.1-100 nm.

Preferably, the acidic solution in the second step is one or more of hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, the molar concentration is 0.1-18.4 mol/L, and the pH value is 0.1-6.9.

Preferably, the area ratio between the inert material and the anode plate in the second step is 1-2, the distance between the cathode and the anode is 10-100 m m, and the surface roughness of the inert material is 1-10 μm.

Preferably, the electrolytic cell in the second step adopts a direct current power supply or a pulse power supply, the cell voltage of the electrolytic cell is 0.1-4.5V, and the cathode current density is 0.01-1A/cm²(ii) a The pulse frequency of the pulse power supply is 100-2000 Hz, and the duty ratio is 3% -97%.

Preferably, the external field is an electric field or an ultrasonic field, and the external field is coupled with a power supply adopted by the electrolytic cell.

Preferably, the voltage of the electric field is 0.1-4.5V; the ultrasonic frequency of the ultrasonic field is 20-3000 kHz, and the ultrasonic power is 0-4000W.

Preferably, the external field application mode is a continuous type or a batch type.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:

(1) the method for preparing the high-purity magnesia-alumina spinel precursor selects high-purity magnesia-alumina alloy as an anode plate, obtains a magnesia-alumina hydroxide precipitation product under the action of electric auxiliary conversion and an external field, and then obtains the high-purity magnesia-alumina spinel precursor by filtering, washing and drying the magnesia-alumina hydroxide precipitation product in sequence; the dissolving speed of the anode aluminum and magnesium is regulated and controlled by regulating and controlling voltage and current density parameters, so that the size and the quantity of the precipitated magnesium aluminate spinel precursor are controllable;

(2) the invention relates to a method for preparing a high-purity magnesia-alumina spinel precursor, which is characterized in that an electrolytic cell is divided into an anode electrolytic cell and a cathode electrolytic cell by a porous membrane, wherein the pore diameter of the porous membrane is 0.1-100 nm; impurities such as Al falling off from the anode₂O₃MgO particles can not pass through the porous membrane to enter a cathode electrolytic cell, so that the pollution of anode impurities to an electrolytic product, namely the magnesium-aluminum hydroxide can be avoided; the cathode made of inert material generates cathodic hydrogen evolution under the action of electric field in the electrolytic cell, and the solution near the cathode generates OH^-OH produced^-With Al³⁺And Mg²⁺Combining to generate a magnesium aluminum hydroxide precipitate product; the high purity of the magnesium aluminate spinel precursor can be ensured;

(3) according to the method for preparing the high-purity magnesia-alumina spinel precursor, the acid solution adopted by the electrolytic cell is one or more of hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, the molar concentration is 0.1-18.4 mol/L, and the pH value is 0.1-6.9; inserting an acidimeter into the acidic solution in the electrolysis process, monitoring the pH value of the electrolyte in real time, and maintaining the pH value of the electrolyte by supplementing the acidic solution; the method is favorable for improving the stability of the electrolytic process, reducing the energy consumption of electrolysis, and is also favorable for stably producing the magnesium aluminum hydroxide precipitate product, and the granularity of the magnesium aluminum hydroxide precipitate product is kept stable; in addition, an acidic solution is adopted as an electrolyte instead of an alkali liquor, a byproduct generated at the cathode of the acidic solution is hydrogen, the product is not influenced, and a small amount of metals such as Na, K and the like are separated out from the cathode of the acidic solution as the electrolyte to pollute an electrolysis product, so that the high purity of the magnesium aluminate spinel precursor is ensured;

(4) according to the method for preparing the high-purity magnesia-alumina spinel precursor, an external field is applied to an electrolysis unit, the external field can be an electric field or an ultrasonic field, a power supply adopted by an electrolysis cell is coupled, the voltage of the electric field is 0.1-4.5V, and the electric field application mode is continuous or intermittent; firstly, Al dissolved out from anode can be accelerated by external field³⁺And Mg²⁺Diffusing out from the periphery of the anode to prevent concentration polarization from being generated, thereby accelerating the electrolysis speed; secondly, since the porous membrane is provided in the electrolytic cell, it blocks Al to some extent³⁺、Mg²⁺The speed of migration from the cathode to the anode results in a reduction in the rate and efficiency of electrolysis, which can be accelerated by the external field across the porous membrane, thereby increasing the rate and efficiency of electrolysis; thirdly, under the action of an external field, the magnesium-aluminum hydroxide precipitation product separated out from the cathode can be acted by force, so that the falling of magnesium-aluminum hydroxide precipitation product powder on the cathode is promoted, and the normal electrolysis is ensured; and fourthly, controlling the falling time of the magnesium aluminum hydroxide precipitation product from the cathode by controlling the size of the external field, preventing the magnesium aluminum hydroxide precipitation product from growing, and ensuring the uniformity of the size of the powder, thereby realizing the control of the granularity of the generated magnesium aluminum spinel precursor powder. The application of the external field avoids the use of a surfactant at the same time, and has the advantage of environmental protection;

(5) according to the method for preparing the high-purity magnesium aluminate spinel precursor, aluminum magnesium alloy byproducts can be prepared from anode mud generated in the production process, and hydrogen byproducts are generated at the cathode, so that the technical economy can be improved.

Drawings

FIG. 1 is a flow chart of a method of preparing a high purity magnesia alumina spinel precursor of the present invention;

FIG. 2 is an electrochemical schematic diagram of a method for preparing a high-purity magnesia-alumina spinel precursor according to the present invention;

FIG. 3 is an electrochemical schematic of example 2 of the present invention.

The reference numerals in the schematic drawings illustrate:

100. an electrolysis unit; 110. an anodic electrolytic cell; 111. anode mud; 112. an anode plate; 120. a cathodic electrolysis cell; 121. magnesium aluminum hydroxide precipitation product; 122. hydrogen gas; 123. an inert material; 130. an acidic solution;

200. a porous membrane;

300. an external field; 310. an anode ultrasonic generator; 320. a cathode ultrasound emitter.

Detailed Description

The detailed description and exemplary embodiments of the invention will be better understood when read in conjunction with the appended drawings, where the elements and features of the invention are identified by reference numerals.

Example 1

Referring to fig. 1, the method for preparing a high-purity magnesia-alumina spinel precursor according to the embodiment includes the following steps: selecting high-purity aluminum-magnesium alloy as an anode plate 112, obtaining a magnesium-aluminum hydroxide precipitate product 121 under the action of electric auxiliary conversion and an external field 300, and filtering, washing and drying the magnesium-aluminum hydroxide precipitate product 121 to obtain a high-purity magnesium-aluminum spinel precursor. The method comprises the following specific steps:

step one, preparation of anode plate 112

Heating high-purity aluminum with the purity of 99-99.999% and high-purity magnesium until the high-purity aluminum and the high-purity magnesium are molten, wherein the molar ratio of the magnesium to the aluminum is 1: 2-1: 4, then casting the high-purity aluminum and the high-purity magnesium into an aluminum-magnesium alloy plate, polishing and cleaning the surface of the aluminum-magnesium alloy plate to obtain an anode plate 112, drying the anode plate, and then placing the anode plate in an inert gas environment for storage for later use; the purpose is to remove impurities and oil stains on the surface of the anode plate 112 and prevent the impurities and oil stains from entering an electrolysis system to cause pollution.

Step two, electric auxiliary transformation

And (3) constructing the electrolysis unit 100 by taking the anode plate 112 obtained in the first step as an anode, taking the inert material 123 as a cathode and taking the acidic solution 130 as an electrolyte, wherein a direct current power supply or a pulse power supply is adopted for the electrolysis cell, the direct current power supply is adopted in the embodiment, the cell voltage of the direct current power supply electrolysis cell is 0.1-4V, and the cathode current density is 0.01～1A/cm²(ii) a In addition, the electrolytic cell is divided into an anode electrolytic cell 110 and a cathode electrolytic cell 120 by a porous membrane 200, and the pore diameter of the porous membrane 200 is 0.1-100 nm; during electrolysis, the anode plate 112 can be converted to magnesium aluminum hydroxide precipitation product 121 in the electrolysis cell 100;

it should be noted that, when the electrolytic cell is in operation, the anode plate 112 undergoes electrochemical dissolution reaction, and Al³⁺、Mg²⁺Enters the electrolyte and migrates to the vicinity of the cathode through the porous membrane 200 under the action of the electric field inside the electrolytic cell. In addition, since the porous film 200 has a pore diameter of 0.1 to 100nm, impurities such as Al falling off from the anode₂O₃The MgO particles cannot pass through the porous membrane 200 and enter the cathode electrolytic cell 120, so that the pollution of the anode impurities to the magnesium aluminum hydroxide serving as an electrolyte product can be avoided; the cathode made of the inert material 123 generates cathodic hydrogen evolution under the action of an electric field inside the electrolytic cell, and the solution near the cathode generates OH^-OH produced^-With Al³⁺、Mg²⁺Combining to form magnesium aluminum hydroxide precipitate product 121.

The acid solution 130 adopted by the electrolytic cell is one or more of hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, the molar concentration is 0.1-18.4 mol/L, and the pH value is 0.1-6.9. During the electrolysis process, an acidity meter is inserted into the acidic solution 130, the pH of the electrolyte is monitored in real time, and the pH of the electrolyte is maintained by replenishing the acidic solution 130. The method aims to improve the stability of the electrolytic process, reduce the energy consumption of electrolysis on one hand, and enable the anode to stably produce the magnesium aluminum hydroxide precipitate product 121 with stable granularity; in addition, an acidic solution is adopted as an electrolyte instead of an alkali liquor, a byproduct generated at the cathode is hydrogen 122, the product is not influenced, and a small amount of metals such as Na, K and the like are separated out from the cathode by using the alkali liquor as the electrolyte to pollute an electrolysis product.

Step three, reinforced stripping

Applying an external field 300 to the electrolysis unit 100 in the second step, wherein the external field 300 is an electric field or an ultrasonic field, the external field 300 is coupled with a power supply adopted by the electrolysis cell, the external field 300 in the embodiment is an electric field, the voltage of the electric field is 0.1-4V, and the electric field application mode is continuousThe continuous type or the batch type, and the continuous type is adopted in the present embodiment. The purpose of applying an external field to the electrolysis cell 100 is to: firstly, Al dissolved out from anode can be accelerated by external field³⁺、Mg²⁺Diffusing out from the periphery of the anode to prevent concentration polarization from being generated, thereby accelerating the electrolysis speed; secondly, since the porous film 200 is provided in the electrolytic cell, it blocks Al to some extent³⁺、Mg²⁺From the rate of migration to the cathode, resulting in a decrease in electrolysis rate and efficiency, the external field 300 can accelerate its passage through the porous membrane 200, thereby increasing electrolysis rate and efficiency; thirdly, as the magnesium-aluminum hydroxide precipitation product can be separated out from the cathode, but the magnesium-aluminum hydroxide precipitation product is a non-conductive substance, when a certain amount of magnesium-aluminum hydroxide precipitation product is accumulated on the cathode, the electrolytic efficiency is reduced, even the electrolytic cell cannot work, and under the action of an external field, the magnesium-aluminum hydroxide precipitation product separated out from the cathode can be acted by force, so that the falling of magnesium-aluminum hydroxide precipitation product powder on the cathode is promoted, and the normal operation of electrolysis is ensured; and fourthly, controlling the falling time of the magnesium aluminum hydroxide precipitation product from the cathode by controlling the size of the external field, preventing the magnesium aluminum hydroxide precipitation product from growing, and ensuring the uniformity of the size of the powder, thereby realizing the control of the granularity of the generated magnesium aluminum spinel precursor powder.

The fourth step: separating and drying

And C, filtering, separating, cleaning and drying the magnesium aluminum hydroxide precipitation product 121 obtained in the step three to obtain the high-purity alumina precursor.

The purity, maximum diameter and cell current efficiency of the electrolytically-obtained magnesia alumina spinel precursor product 121 are recorded in table 1.

Comparative example 1

The comparative example was carried out in the same manner as example 1 except that: the purity, maximum diameter and cell current efficiency of the electrolytically-obtained magnesia alumina spinel precursor product 121 are reported in table 1, without the addition of the porous membrane 200 to the cell.

Comparative example 2

The comparative example was carried out in the same manner as example 1 except that: the pH was not adjusted during electrolysis and the purity, maximum diameter and cell current efficiency of the electrolyzed magnesia alumina spinel precursor product 121 were recorded in table 1.

Comparative example 3

The comparative example was carried out in the same manner as example 1 except that: the enhanced stripping step is eliminated and finally the purity, maximum diameter and cell current efficiency of the electrolytically-obtained magnesia alumina spinel precursor product 121 are recorded in table 1.

Through comparison between the embodiment 1 and the comparative examples 1 to 3, the method for preparing the high-purity magnesia-alumina spinel precursor provided by the invention adopts the measures of isolating anode impurities by the porous membrane 200, strengthening and stripping an external field and the like, so that the purity of the obtained high-purity magnesia-alumina spinel precursor can reach 12N, the maximum diameter of the ultra-pure alumina precursor is only 0.35 mu m, and the electrolytic efficiency is as high as 90.5%. The reason for this may be:

(1) compared with the comparative example 1, the purity of the high-purity magnesia-alumina spinel precursor in the example 1 is obviously improved, which may be caused by: the porous membrane 200 prevents impurity-rich, non-uniform sized Al from falling off the anode₂O₃The MgO particles and anode slime product enter the cathode preventing them from contaminating the electrolysis products. In addition, the maximum diameter of the ultra-pure magnesia-alumina spinel precursor in the examples is significantly smaller than that in comparative example 1, probably due to: the porous film 200 blocks Al rich in impurities₂O₃The MgO particles and the anode mud product enter the cathode, and the impurities can become the nucleation core of the cathode product magnesium aluminum hydroxide precipitate 121 at the cathode, so that the separated magnesium aluminum hydroxide product is gathered around the impurities to grow, a large-particle magnesium aluminum spinel precursor is easy to form, and adverse effects are generated on links such as roasting for subsequently preparing the ultra-pure magnesium aluminum spinel.

(2) The current efficiency was significantly improved in example 1 compared to comparative example 2, probably due to: h of the electrolyte as the cathode continues to evolve hydrogen 122⁺The concentration is continuously reduced, thereby affecting the cathode reaction and reducing the electrolysis efficiency. Meanwhile, as the electrolytic efficiency is reduced, the nucleation work of magnesium aluminum hydroxide products separated out from the cathode is reduced, and a plurality of magnesium aluminum hydroxide products cannot be efficiently formed, so thatThe magnesium aluminum hydroxide can only be separated out from the surface of the powder of the original magnesium aluminum hydroxide product, so that the magnesium aluminum hydroxide product grows continuously and has large diameter, which is not beneficial to the subsequent roasting link.

(3) The maximum diameter of the high purity magnesia alumina spinel precursor of example 1 is significantly smaller than that of comparative example 3, probably due to: under the action of the external field 300, the magnesium-aluminum hydroxide product precipitated from the cathode falls off from the cathode under the action of the external field, so that an accumulation effect is avoided, and the growth of the magnesium-aluminum hydroxide product powder is inhibited. The current efficiency was significantly improved in example 1 compared to comparative example 3, probably due to: magnesium aluminum hydroxide products precipitated from the cathode can be gathered around the cathode inert material 123, and the magnesium aluminum hydroxide products have high resistance, so that the electrolysis efficiency is seriously influenced, and the current efficiency is sharply reduced.

Therefore, according to the method for preparing the high-purity magnesia-alumina spinel precursor, high-purity magnesia-alumina alloy is selected as the anode plate 112, anode impurities are filtered by the porous membrane 200 under the action of electric auxiliary conversion and an external field 300, so that the magnesia-alumina hydroxide product 121 is obtained, the purity of the obtained ultra-pure magnesia-alumina spinel precursor is up to 12N, the maximum diameter is only 0.35 mu m, the current efficiency is up to 90.5%, the high-purity magnesia-alumina spinel precursor can be efficiently prepared, and the process is controlled by electrochemical parameters, so that the process is controllable, the product purity is high, the granularity is controllable, the powder uniformity is good, and the efficiency is high.

As shown in fig. 2, the apparatus for preparing high-purity magnesia-alumina spinel precursor of the present invention comprises an electrolysis unit 100, a porous membrane 200 and an external field 300, wherein the electrolysis unit 100 comprises an anode electrolytic cell 110, a cathode electrolytic cell 120 and an acidic solution 130, the porous membrane 200 is disposed in the acidic solution 130, and the electrolysis unit 100 is divided into the anode electrolytic cell 110 and the cathode electrolytic cell 120; the pore diameter of the porous membrane 200 is 0.1-100 nm, the porous membrane 200 is selected as a strong acid corrosion resistant material, and the preferable material is one of polyamides, polysulfones, fluorine-containing materials, polycarbonates, polyesters, polyolefins and inorganic materials; the external field 300 applies an external force to the electrolysis unit 100. Further, the anode electrolytic tank 110 further comprises an anode plate 112, wherein the anode plate 112 is highA pure aluminum magnesium alloy plate; the cathode electrolytic cell 120 further comprises an inert cathode material 123, wherein the inert cathode material 123 is high-purity graphite, Pt, Pd; the area ratio between the inert material 123 and the anode plate 112 is 1-2, the distance between the cathode and the anode is 10-100 mm, and the surface roughness of the inert material 123 is 1-10 μm. The acidic solution 130 is one or more of hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, the molar concentration is 0.1-18.4 mol/L, and the pH value is 0.1-6.9. In addition, the electrolytic cell adopts a direct current power supply or a pulse power supply; the cell voltage of the direct current power supply electrolytic cell is 0.1-4.5V, and the cathode current density is 0.01-1A/cm²(ii) a The pulse frequency of the pulse power supply is 100-2000 Hz, and the duty ratio is 3% -97%. The external field 300 is an electric field or an ultrasonic field, the electric field is used as the external field 300 in the embodiment, the external field 300 is coupled with a power supply adopted by the electrolytic cell, and the voltage of the electric field is 0.1-4.5V; the ultrasonic frequency of the ultrasonic field is 20-3000 kHz, the ultrasonic power is 0-4000W, the application mode of the external field 300 is continuous or intermittent, and the continuous application is adopted in the embodiment.

Example 2

This example is substantially the same as example 1, except that: the external field 300 is an ultrasonic field, an anode ultrasonic emitter 310 and a cathode ultrasonic emitter 320 are respectively arranged on the anode electrolytic cell 110 and the cathode electrolytic cell 120, and the ultrasonic fields are respectively emitted to the anode electrolytic cell 110 and the cathode electrolytic cell 120; the ultrasonic frequency of the ultrasonic field is 20-3000 kHz, the ultrasonic power is 0-4000W, and the application mode of the ultrasonic external field is continuous application. The purity, maximum diameter and cell current efficiency of the magnesium aluminum hydroxide product 121 obtained by electrolysis are reported in table 1. It is seen that the maximum diameter of the ultra-pure alumina precursor obtained is further reduced to 0.11 μm compared to example 1, because it is possible to: the ultrasonic field directly acts on the acid solution, the acting force on the magnesium-aluminum hydroxide product precipitated from the cathode is more obvious, and the precipitated magnesium-aluminum hydroxide product is separated from the cathode and falls off under the action of the ultrasonic external field without growing in time.

Example 3

This example is substantially the same as example 1, except that: the electric field application was of the batch type and the purity of the magnesium aluminate spinel precursor product, the maximum diameter and the current efficiency of the cell were recorded in table 1.

Example 4

This example is substantially the same as example 1, except that the ultrasonic field application manner was a batch type, and the purity, maximum diameter, and current efficiency of the electrolytic cell of the obtained magnesia alumina spinel precursor product were recorded in table 1.

TABLE 1 purity of ultra-pure alumina precursor after electrolysis

The invention has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.