A method for preparing high-purity gallium oxide by acid electrolysis

Abstract

This invention discloses a method for preparing high-purity gallium oxide by acid electrolysis, comprising the following steps: (1) acid washing of crude gallium to obtain pretreated crude gallium; (2) placing the pretreated crude gallium obtained in step (1) as the anode into an electrolytic cell containing acidic electrolyte for electrochemical dissolution to obtain a gallium-containing solution; (3) replacing the gallium-containing solution obtained in step (2) with high-purity gallium to remove impurities, and then performing liquid-solid separation to obtain a gallium-containing purified solution; (4) neutralizing the gallium-containing purified solution obtained in step (3) with ammonia to precipitate gallium hydroxide to obtain gallium hydroxide precipitate; (5) drying and calcining the gallium hydroxide precipitate obtained in step (4) to obtain 6N high-purity gallium oxide. This invention can use 2N crude gallium as raw material and prepare high-purity gallium oxide by electrochemical dissolution under acidic electrolyte. The entire process has high production efficiency, few side reactions, low impurity ion content, and low production cost, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of metal compound preparation, and particularly relates to a method for producing gallium compounds. Background Technology

[0002] With the rapid development of emerging industries such as new energy, consumer electronics, communication systems, photovoltaic power generation, and integrated circuits, semiconductor technology has also undergone technological iteration and updates. Gallium oxide (GaO), as a fourth-generation semiconductor material, has achieved rapid development. GaO is an ultra-wide bandgap semiconductor material with a bandgap EG = 4.9 eV, far exceeding that of semiconductor materials such as silicon carbide (3.4 eV), gallium nitride (approximately 3.3 eV), and silicon (1.1 eV). GaO-based power devices feature high voltage withstand capability, low loss, high efficiency, and small size. Under the same voltage withstand capability, GaO-based devices have 86% lower losses than silicon carbide-based devices, and their size is only about 1 / 5 that of silicon carbide-based devices. Simultaneously, the high breakdown field strength of GaO ensures that the fabricated devices can be used at ultra-high voltages, which is beneficial for improving carrier collection efficiency. Currently, GaO semiconductor products have shown broad development prospects.

[0003] The mainstream production process for high-purity gallium oxide currently involves dissolving crude gallium, precipitating gallium to obtain gallium hydroxide, and then calcining to obtain gallium oxide. The gallium dissolution system for crude gallium includes strong acid dissolution and alkaline electrochemical dissolution systems. Strong acid dissolution often requires high concentrations of strong acid to effectively dissolve the metallic gallium, which results in a large amount of impurities entering the gallium-containing acid solution, hindering subsequent precipitation and calcination to produce high-purity gallium oxide. Alkaline electrochemical dissolution involves dissolving crude gallium in an electrochemical solution under alkaline conditions. For example, patent CN102978649A adds 99.99% industrial gallium to an electrolytic cell containing a 30% sodium hydroxide solution, performing a three-stage electrochemical dissolution to prepare a sodium gallate solution. The sodium gallate solution is then neutralized, washed, dried, and calcined to obtain high-purity gallium oxide. This method uses a large amount of alkali, requires a high current density during electrolysis, has high production costs, and is prone to gallium deposition at the cathode, resulting in severe side reactions.

[0004] Therefore, current methods for producing high-purity gallium oxide suffer from problems such as numerous impurity ions, high production costs, and numerous side reactions when dissolving crude gallium. Providing a high-purity gallium oxide production method with fewer impurity ions, lower production costs, and fewer side reactions is of great significance for the industrial production of gallium oxide. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a method for preparing high-purity gallium oxide by acidic electrolysis with low production cost, few side reactions, and product purity of 6N or higher. To solve the above technical problem, the technical solution proposed by this invention is as follows:

[0006] A method for preparing high-purity gallium oxide by acidic electrolysis includes the following steps:

[0007] (1) Pretreated crude gallium is obtained by acid washing of crude gallium; the crude gallium can be made from 2N crude gallium, which overcomes the limitations of raw materials and greatly reduces the raw material production cost;

[0008] (2) The pretreated crude gallium obtained in step (1) is placed into an electrolytic cell containing acidic electrolyte for electrochemical dissolution to obtain a gallium-containing solution;

[0009] (3) The gallium-containing solution obtained in step (2) is replaced with high-purity gallium to remove impurities, and the replaced liquid is subjected to liquid-solid separation to obtain gallium-containing purified solution;

[0010] (4) The gallium-containing purification solution obtained in step (3) is neutralized with ammonia water to precipitate gallium hydroxide;

[0011] (5) The gallium hydroxide precipitate obtained in step (4) is dried and calcined to obtain 6N high-purity gallium oxide.

[0012] In the above method for preparing high-purity gallium oxide by acidic electrolysis, preferably, the acidic electrolyte is an H2SO4 solution or an HCl solution, and the pH value of the acidic electrolyte is controlled to be 1.0-2.5.

[0013] In the above-mentioned method for preparing high-purity gallium oxide by acidic electrolysis, preferably, the current density is controlled at 500-1000 A / m during electrochemical dissolution. 2 .

[0014] During electrochemical dissolution, considering factors such as side reactions and the content of impurity ions, the pH value and current density of the electrolyte need to be strictly controlled. Maintaining a lower pH value is beneficial for impurity removal, reducing the concentration of impurities in the electrolyte. When the pH value is less than 1.0, the increased acidity allows more impurity metals to enter the electrolyte. When the pH value is greater than 2.5, the increased gallium concentration causes gallium deposition, resulting in gallium loss. Simultaneously, the current density should be controlled between 500-1000 A / m. 2 It is beneficial for the dissolution of gallium and the removal of impurities when the current density is below 500 A / m. 2 Gallium dissolves relatively slowly, especially when the current exceeds 1000 A / m. 2This can lead to excessively high cell voltage, causing impurity metal ions to dissolve in the electrolyte, which is detrimental to subsequent electrolyte purification. The main impurities in crude gallium are indium, copper, and lead. During electrochemical dissolution, impurities such as In, Fe, Cu, Pb, and Ag have more positive potentials than gallium and are insoluble in the anode, accumulating at the bottom of the anode region to form anode sludge. Impurities with more negative potentials than gallium, such as Ca, Na, and Al, dissolve in the anode first but do not precipitate at the cathode, remaining in the electrolyte. When the gallium concentration in the anode chamber exceeds 200 g / L, a portion of the anolyte is extracted for further purification, while fresh electrolyte is added to the cathode chamber. The main reactions occurring during electrolysis are:

[0015] Anode: Ga-3e - =Ga 3+ ;

[0016] Cathode: 2H₂O + 2e⁻ - =H2↑+2OH - ;

[0017] 2H + +2e - =H2↑.

[0018] In the above method for preparing high-purity gallium oxide via acidic electrolysis, preferably, 6N high-purity gallium is used for displacement purification of impurities. Displacement purification with high-purity gallium removes metals with lower activity than gallium, yielding a high-purity gallium solution. The displacement can use 6N high-purity gallium, and the solution before purification typically contains impurities such as indium at the ppm level. Since the standard electrode potential of gallium is -0.549V and that of indium is +0.33V, gallium's activity is much higher than indium's. Using high-purity gallium can effectively displace and remove indium and most of the impurity metals, thereby achieving the purpose of purifying the gallium-containing solution.

[0019] In the above method for preparing high-purity gallium oxide via acidic electrolysis, preferably, the final pH value of neutralization precipitation is controlled at 3.5-6, and the gallium hydroxide precipitate is washed with deionized water until neutral. The gallium hydroxide obtained from neutralization precipitation is washed multiple times to remove residual alkaline solution and soluble metal inclusions. The main impurities in the gallium-containing solution are alkali metals or alkaline earth metals such as Ca and Al. Ammonia water is used as the neutralizing agent instead of a strongly alkaline sodium hydroxide solution to avoid excessively high local alkalinity during the addition of a strongly alkaline neutralizing agent, which would cause alkaline earth metals to form microparticle precipitates and affect the quality of gallium hydroxide. Ammonia water is a weakly alkaline substance and produces OH- during hydrolysis. - It serves to neutralize gallium-containing solutions, and controlling the pH value of the solution helps ensure the quality of gallium hydroxide precipitation.

[0020] In the above-mentioned method for preparing high-purity gallium oxide via acid electrolysis, preferably, concentrated sulfuric acid or concentrated hydrochloric acid is used for acid washing of crude gallium, 2-3 times, each time for 20-30 minutes, at room temperature; after acid washing, deionized water is used for washing 3-5 times. Because crude gallium is exposed to humid air for a long time, it is easily oxidized into oxides, and oil stains also adhere to its surface. Washing with concentrated acid can remove oxides and oil stains from the surface of crude gallium, reducing the impact of impurities on subsequent purification; washing with deionized water 3-5 times after concentrated acid washing can remove residual acid and impurities from the surface.

[0021] In the above-described method for preparing high-purity gallium oxide via acidic electrolysis, preferably, during electrochemical dissolution, a pretreated crude gallium is coated with a polyethylene or polypropylene filter bag and used as the anode, a stainless steel plate is used as the cathode, and a diaphragm is used to divide the electrolytic cell into an anode chamber and a cathode chamber. Using crude gallium as the anode and coating it with a polyethylene or polypropylene filter bag can prevent anode sludge from entering the electrolyte and contaminating it.

[0022] In the above-described method for preparing high-purity gallium oxide via acidic electrolysis, preferably, the drying and calcination processes involve first drying and then calcining. The drying temperature is controlled at 80-120℃ for 2-6 hours, and the calcination temperature is controlled at 500-800℃ for 4-6 hours. The gallium oxide product obtained after calcination achieves a purity of 6N or higher. Calcination temperatures below 500℃ result in incomplete decomposition of gallium hydroxide, affecting the quality of the gallium oxide. Calcination temperatures above 800℃ cause severe agglomeration, resulting in inconsistent morphology and significantly impacting the quality of the gallium oxide.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] 1. The method for preparing high-purity gallium oxide by acidic electrolysis of the present invention involves electrochemical dissolution under acidic electrolyte conditions. During the electrochemical dissolution process, inert metal enters the anode mud, which plays a role in purification and impurity removal, resulting in a high-purity gallium salt solution. This avoids the problem of excessive impurity ions caused by dissolving crude gallium under strong acid conditions. Compared with alkaline electrochemical dissolution systems, this method increases the gallium dissolution rate and improves production efficiency. Furthermore, the process is simple to operate, avoids gallium deposition at the cathode under alkaline systems, and has fewer side reactions. In addition, it can greatly reduce the amount of alkali used, thereby reducing production costs.

[0025] 2. The present invention provides a method for preparing high-purity gallium oxide through acidic electrolysis. In the entire process, the neutralized gallium precipitation solution is returned to the system as the electrolyte, without producing wastewater or exhaust gas that pollutes the environment. The raw materials and auxiliary materials are readily available, making it suitable for industrial-scale production.

[0026] In summary, this invention can use 2N crude gallium as raw material and prepare high-purity gallium oxide by electrochemical dissolution in an acidic electrolyte. The entire process has high production efficiency, few side reactions, low impurity ion content, and low production cost, making it suitable for large-scale industrial production. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a process flow diagram of the method for preparing high-purity gallium oxide by acidic electrolysis according to the present invention. Detailed Implementation

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Example 1:

[0033] like Figure 1 As shown, a method for preparing high-purity gallium oxide by acidic electrolysis includes the following steps:

[0034] (1) The crude gallium with a gallium content of 99.52% was placed in a concentrated acid solution with a ratio of concentrated sulfuric acid and concentrated hydrochloric acid of 1:1 for chemical cleaning at room temperature. The cleaning was performed twice, each time for 20 minutes. After the crude gallium was cleaned, it was washed three times with deionized water in a countercurrent manner.

[0035] (2) Prepare an electrolyte solution with a pH of 1.0 by mixing concentrated sulfuric acid and water. Then, load the prepared electrolyte solution into the electrolytic cell. Place the crude gallium that has been chemically cleaned into the electrolytic cell using a polyethylene filter bag as the anode and perform electrolysis. Control the current density to be 900 A / m. 2 Electrochemical dissolution was performed to obtain a gallium solution containing 280 g / L of gallium; other valuable metals were recovered from the anode mud.

[0036] (3) The gallium-containing solution is replaced with high-purity gallium of 6N or higher to remove metal impurities with electrode potential higher than that of gallium. The reaction temperature is controlled at 60℃ and the reaction time is 2h. After the replacement is completed, liquid-solid separation is performed to obtain purified liquid and purified residue. The purified liquid is then neutralized in the next step, and other valuable metals are recovered from the purified residue.

[0037] (4) Add ammonia water as a neutralizing agent slowly to the purification solution to neutralize it, adjust the pH value of the solution to 6.0, stabilize the pH value and continue the reaction for 30 minutes. After liquid-solid separation, a white gallium hydroxide precipitate is obtained. The precipitate is washed multiple times with deionized water until the pH value of the washing solution is neutral, and high-purity gallium hydroxide is obtained.

[0038] (5) Gallium hydroxide was dried at 80°C and then calcined at 550°C for 5 hours to obtain high-purity gallium oxide with a purity of 6N or higher.

[0039] The total content of impurity elements In, Cu, Pb, Zn, Fe, Ni, Mg, Cr, Co, and Mn in the high-purity gallium oxide in this embodiment was measured to be 0.9 ppm. Specific details are shown in Table 1 below.

[0040] Table 1: Main impurities in crude gallium and high-purity gallium oxide in Example 1

[0041]

[0042] Example 2:

[0043] like Figure 1 As shown, a method for preparing high-purity gallium oxide by acidic electrolysis includes the following steps:

[0044] (1) Crude gallium with a gallium content of 99.53% was placed in concentrated sulfuric acid for room temperature chemical cleaning. The cleaning was performed 3 times, each time for 20 minutes. After the crude gallium was cleaned, it was washed 4 times with deionized water in a countercurrent manner.

[0045] (2) Prepare an electrolyte solution with a pH of 2.0 using concentrated sulfuric acid and water. Then, load the prepared electrolyte solution into the electrolytic cell. Place the crude gallium that has been chemically cleaned into the electrolytic cell using a polyethylene filter bag as the anode and perform electrolysis. Control the current density to be 600 A / m. 2 Electrochemical dissolution was performed to obtain a gallium solution containing 240 g / L of gallium; other valuable metals were recovered from the anode mud.

[0046] (3) The gallium-containing solution is replaced with high-purity gallium of 6N or higher. Metal impurities with electrode potential higher than gallium positive charge are removed by replacement. The reaction temperature is controlled at 50℃ and the reaction time is 3h. After replacement, liquid-solid separation is carried out to obtain purified liquid and purified residue. The liquid is then used for the next step of neutralization treatment, and other valuable metals are recovered from the purified residue.

[0047] (4) Neutralize the purified solution by slowly adding ammonia water to adjust the pH value to 5.5, stabilize the pH value and continue the reaction for 60 minutes. After liquid-solid separation, white gallium hydroxide precipitate is obtained. The precipitate is washed multiple times with deionized water until the pH value of the washing solution is neutral, and high-purity gallium hydroxide is obtained.

[0048] (5) Gallium hydroxide was dried at 100°C and then calcined at 600°C for 4 hours to obtain high-purity gallium oxide with a purity of 6N or higher.

[0049] In this embodiment, the total content of impurity elements In, Cu, Pb, Zn, Fe, Ni, Mg, Cr, Co, and Mn in the high-purity gallium oxide is 0.89 ppm. Specific details are shown in Table 2 below.

[0050] Table 2: Main impurities in crude gallium and high-purity gallium oxide in Example 2

[0051]

[0052] Example 3:

[0053] like Figure 1 As shown, a method for preparing high-purity gallium oxide by acidic electrolysis includes the following steps:

[0054] (1) Place crude gallium with a gallium content of 99.55% into concentrated hydrochloric acid for room temperature chemical cleaning, clean 3 times, each time for 30 minutes, and after cleaning the crude gallium, wash it 4 times with deionized water in a countercurrent manner.

[0055] (2) Prepare an electrolyte solution with a pH of 1.5 by mixing concentrated hydrochloric acid and water. Then, load the prepared electrolyte solution into the electrolytic cell. Place the crude gallium that has been chemically cleaned into the electrolytic cell using a polyethylene filter bag as the anode and perform electrolysis. Control the current density to be 800 A / m. 2 Electrochemical dissolution was performed to obtain a gallium solution containing 260 g / L of gallium; other valuable metals were recovered from the anode mud.

[0056] (3) The gallium-containing solution is replaced with high-purity gallium of 6N or higher. Metal impurities with electrode potential higher than gallium positive charge are removed by replacement. The reaction temperature is controlled at 55℃ and the reaction time is 3h. After replacement, liquid-solid separation is carried out to obtain purified liquid and purified residue. The liquid is then used for the next step of neutralization treatment, and other valuable metals are recovered from the purified residue.

[0057] (4) Neutralize the purified solution by slowly adding ammonia water, adjust the pH value of the solution to 5, stabilize the pH value and continue the reaction for 60 minutes. After liquid-solid separation, white gallium hydroxide precipitate is obtained. The precipitate is washed multiple times with deionized water until the pH value of the washing solution is neutral, and high-purity gallium hydroxide is obtained.

[0058] (5) Gallium hydroxide was dried at 90°C and then calcined at 800°C for 6 hours to obtain gallium oxide with a strength of 6N or higher.

[0059] In this embodiment, the total content of impurity elements In, Cu, Pb, Zn, Fe, Ni, Mg, Cr, Co, and Mn in the high-purity gallium oxide is 0.94 ppm. Specific details are shown in Table 3 below.

[0060] Table 3: Main impurities in crude gallium and high-purity gallium oxide in Example 3

[0061]

[0062] Comparative Example 1:

[0063] A method for producing high-purity gallium oxide includes the following steps:

[0064] (1) The crude gallium with a gallium content of 99.55% in Example 3 was placed in concentrated hydrochloric acid for room temperature chemical cleaning. The cleaning was performed 3 times, each time for 30 minutes. After the crude gallium was cleaned, it was washed 4 times with deionized water in a countercurrent manner.

[0065] (2) Add deionized water and a 30% NaOH solution to the electrolytic cell at a ratio of 1:1. Use crude gallium as the anode and stainless steel as the cathode, and control the current density to 800 A / m. 2 After electrolysis for a certain period of time, a gallium solution containing 260 g / L of gallium was obtained.

[0066] (3) The electrolyte is prepared, the scum and oxide film are filtered off, and the solution is neutralized with acid to control the pH value to 5, so as to obtain a white hydroxide precipitate gallium hydroxide.

[0067] (4) The white gallium hydroxide precipitate was repeatedly washed to remove the alkali. The washed gallium hydroxide was dried at 90°C and then calcined at 800°C for 6 hours to obtain gallium oxide with a strength of 5N or higher. The specific details are shown in Table 4 below.

[0068] Table 4: Main impurities in crude gallium and high-purity gallium oxide in Comparative Example 1

[0069]

[0070] As can be seen from Example 3 and Comparative Example 1, the effect of Example 3 is significantly better than that of the Comparative Example, indicating that, in terms of product quality, electrochemical dissolution under acidic electrolyte is better than electrochemical dissolution under alkaline electrolyte.

Claims

1. A method for preparing high-purity gallium oxide by acidic electrolysis, characterized in that, Includes the following steps: (1) Pretreated crude gallium is obtained by acid washing of crude gallium; (2) The pretreated crude gallium obtained in step (1) is placed into an electrolytic cell containing acidic electrolyte for electrochemical dissolution to obtain a gallium-containing solution; (3) The gallium-containing solution obtained in step (2) is replaced with high-purity gallium to remove impurities, and the replaced liquid is subjected to liquid-solid separation to obtain gallium-containing purified solution; (4) The gallium-containing purification solution obtained in step (3) is neutralized with ammonia water to precipitate gallium hydroxide; (5) The gallium hydroxide precipitate obtained in step (4) is dried and calcined to obtain 6N high-purity gallium oxide; The acidic electrolyte is an H2SO4 solution or an HCl solution, and the pH value of the acidic electrolyte is controlled to be 1.0-2.

5. During electrochemical dissolution, the current density is controlled at 500-1000 A / m. 2 .

2. The method for preparing high-purity gallium oxide by acidic electrolysis according to claim 1, characterized in that, The high-purity gallium used for impurity removal by displacement is 6N high-purity gallium.

3. The method for preparing high-purity gallium oxide by acidic electrolysis according to claim 1, characterized in that, During neutralization precipitation, the final pH value of the neutralization precipitation should be controlled to be 3.5-6.

4. The method for preparing high-purity gallium oxide by acidic electrolysis according to any one of claims 1-3, characterized in that, When acid-washing crude gallium, use concentrated sulfuric acid or concentrated hydrochloric acid for cleaning 2-3 times, each time for 20-30 minutes, at room temperature; after acid washing, rinse with deionized water 3-5 times.

5. The method for preparing high-purity gallium oxide by acidic electrolysis according to any one of claims 1-3, characterized in that, During electrochemical dissolution, pretreated crude gallium is coated with a polyethylene or polypropylene filter bag and used as the anode, while a stainless steel plate is used as the cathode. A diaphragm is used to divide the electrolytic cell into an anode chamber and a cathode chamber.

6. The method for preparing high-purity gallium oxide by acidic electrolysis according to any one of claims 1-3, characterized in that, During the drying and roasting process, the product is first dried and then roasted. The drying temperature is controlled at 80-120℃ and the drying time is 2-6 hours. The roasting temperature is controlled at 500-800℃ and the roasting time is 4-6 hours.

Images