A method for separating and recovering gallium arsenic from gallium arsenide waste

Abstract

The invention discloses a method for separating and recovering gallium arsenic from gallium arsenide waste, comprising the following steps: (1) adding alkali and oxidant to gallium arsenide waste to selectively leach gallium arsenide waste to neutralize arsenic and gallium, separating to obtain leaching residue and leaching solution after leaching is completed, and obtaining circulating leaching mother liquor after the leaching solution is leached for multiple cycles; (2) heating the circulating leaching mother liquor first, then standing at low temperature to cool and crystallize, separating and crystallizing after precipitation is complete, obtaining sodium arsenate crystals and a primary gallium-rich mother liquor; (3) adding arsenic precipitation agent to the primary gallium-rich mother liquor to precipitate arsenic for a second time, separating to obtain arsenic precipitation residue and a secondary gallium-rich mother liquor; (4) recovering gallium ions in the secondary gallium-rich mother liquor by cyclone electrowinning to obtain metallic gallium. The method for separating and recovering gallium arsenic from gallium arsenide waste of the invention can obtain a high-concentration gallium-arsenic enriched solution, and after the separation of gallium arsenic, the arsenic concentration in the gallium-rich mother liquor is low, which is conducive to the electrowinning recovery of gallium.

Description

Technical Field

[0001] The invention belongs to the field of waste recycling, and in particular relates to a method for recycling gallium arsenide waste. Background Art

[0002] Gallium is an important rare metal. Gallium and its compounds have excellent photoelectric and chemical properties. They are widely used in semiconductor materials, solar cells, alloys, chemicals, medical treatment and other fields. They are key raw materials for the development of modern high technology. The abundance of gallium in the earth's crust is only 17 mg / L. There are no independent deposits worth mining, so gallium is mainly recovered as a by-product of the smelting process. Gallium in nature is mainly associated with minerals such as bauxite, zinc ore and coal mines. Bayer mother liquor in the aluminum smelting process and leaching slag in the zinc smelting process are the main sources of gallium extraction. In addition, fly ash, electric furnace dust in phosphate plants, semiconductor processing waste, etc. are also important resources of gallium. At present, the recovery of gallium is mainly based on primary resources, but with the increasing global demand for gallium, the recovery of gallium from secondary resources has gradually attracted people's attention. The efficient and clean recovery of gallium secondary resources can be used to alleviate the contradiction between the supply and demand of gallium metal in the future.

[0003] Gallium arsenide is one of the most widely used products of gallium. Its gallium grade is much higher than that of general gallium minerals, and it is an important raw material for secondary gallium. The production process of gallium arsenide devices has many steps and a low yield rate, including grinding and polishing. The gallium arsenide waste generated in these processes accounts for 85% of the raw materials. The gallium grade in the above-mentioned gallium arsenide waste is about 2-3%, which is a high-quality secondary resource, but its composition is relatively complex, including corundum, silicon dioxide, zirconium dioxide, cerium oxide, iron oxide, etc. contained in the abrasive. Since the waste is difficult to recycle and contains arsenic, the current conventional disposal method of enterprises is to treat it as hazardous waste and then landfill it, which leads to the waste of gallium resources and the increase of processing costs. Therefore, recycled gallium has the dual significance of resource utilization and environmental protection. It is not only conducive to alleviating the contradiction between the supply and demand of metallic gallium, but also can turn waste into treasure and solve the environmental problems caused by arsenic-containing waste.

[0004] Patent CN110938742A discloses a method for recovering sodium arsenate and metallic gallium from gallium arsenide waste residue. The method first uses an alkaline solution and an oxidant to repeatedly leach gallium arsenide to obtain a gallium arsenic enriched solution, and then evaporates, crystallizes, and precipitates arsenic and performs cyclone electrolysis on the gallium arsenic enriched solution to obtain metallic gallium. In the above method, the concentration of gallium in the gallium arsenic enriched solution is low. Since the theoretical precipitation potential of gallium is relatively negative, there are serious concentration polarization and hydrogen evolution side reactions during the electrolysis process, resulting in a low current efficiency. If the number of leaching times is increased to increase the concentration of gallium in the gallium arsenic enriched solution, the concentration of arsenic will increase simultaneously. After the subsequent evaporation and crystallization of arsenic, the solution still contains a certain amount of arsenic, and the electrolysis process may produce arsenic and arsine.

[0005] Therefore, it is of great significance to develop a new gallium arsenide waste treatment process to facilitate gallium recovery. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a method for separating and recovering gallium arsenic from gallium arsenide waste, which can obtain a high-concentration gallium arsenic enriched solution. After the separation of gallium arsenic, the arsenic concentration in the gallium-rich mother liquor is low, which is conducive to the electrolytic recovery of gallium. In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for separating and recovering gallium arsenic from gallium arsenide waste comprises the following steps:

[0008] (1) adding alkali and oxidant to gallium arsenide waste to selectively leach gallium arsenide waste to neutralize arsenic and gallium, and separating to obtain leaching residue and leaching liquid after leaching is completed. After the leaching liquid is leached for multiple cycles, a circulating leaching mother liquor is obtained, and the concentrations of gallium ions and arsenic ions in the circulating leaching mother liquor are controlled to be 30-60 g / L;

[0009] (2) heating the circulating leaching mother liquor obtained in step (1), then cooling and crystallizing at low temperature, and separating and crystallizing after precipitation is complete to obtain sodium arsenate crystals and a primary gallium-rich mother liquor;

[0010] (3) adding an arsenic precipitating agent to the primary gallium-rich mother liquor obtained in step (2) to perform secondary arsenic precipitation, and separating to obtain arsenic precipitating slag and secondary gallium-rich mother liquor;

[0011] (4) The gallium ions in the secondary gallium-rich mother liquor obtained in step (3) are recovered by cyclonic electrowinning to obtain metallic gallium.

[0012] In the above method for separating and recovering gallium arsenic from gallium arsenide waste, preferably, the arsenic precipitating agent includes barium oxide, calcium oxide, magnesium oxide and cerium oxide, and the mass ratio of barium oxide, calcium oxide, magnesium oxide and cerium oxide is (3-8): (0.1-1): (0.1-1): (0.1-1).

[0013] In the above method for separating and recovering gallium arsenic from gallium arsenide waste, preferably, the arsenic precipitant is first dispersed using a hot alkaline solution (sodium hydroxide solution at 30-90°C) with a pH value >14 to obtain a dispersed suspension with a mass concentration of 30-50%, and then added to the gallium-rich mother liquor once more.

[0014] In the present invention, the reaction conditions of the secondary arsenic precipitation can be: temperature of 30-90°C, mass ratio of arsenic precipitation agent: arsenic of (3-5): 1, stirring reaction time of 30-60min, stirring speed of 200-300r / min, aging treatment after arsenic precipitation, aging temperature of 60-80°C, aging time of 60-90min, aging stirring speed of 50-100r / min. Increasing the temperature can accelerate the precipitation reaction, but too high a temperature will lead to an increase in the ion solubility product, resulting in incomplete precipitation and a decrease in the precipitation rate. In order to ensure the removal rate of arsenic, the amount of arsenic precipitation agent used needs to be higher than the theoretical amount, but the excess coefficient of the arsenic precipitation agent should be reduced as much as possible under the premise of ensuring the precipitation rate.

[0015] In the above-mentioned method for separating and recovering gallium arsenic from gallium arsenide waste, preferably, after the secondary arsenic precipitation, sulfate ions and / or carbonate ions (sodium sulfate and / or sodium carbonate) are added to the secondary gallium-rich mother liquor for impurity removal to remove excess arsenic precipitating agent. The reaction conditions when adding sulfate ions and / or carbonate ions for impurity removal can be: the mass ratio of the total amount of sodium sulfate and sodium carbonate to the excess arsenic precipitating agent is (1.5-2.5): 1, the stirring reaction time is 10-30min, the stirring speed is 200-300r / min, the aging temperature is 20-40°C, and then the aging treatment is performed, the aging time is 10-30min, and the aging stirring speed is 50-100r / min. In order to prevent the introduction of new impurity ions into the system and ensure the purity of gallium in the subsequent recovery process, sodium sulfate and sodium carbonate need to be added as precipitants to remove excess arsenic precipitating agent ions.

[0016] Since the effective components of the above-mentioned arsenic precipitating agent are slightly soluble or difficult to dissolve in alkali, directly adding the arsenic precipitating agent to the primary gallium-rich solution may cause flocculation and agglomeration, resulting in a smaller specific surface area, thereby reducing the arsenic removal efficiency. The present invention first uses a hot alkaline solution to prepare a dispersed suspension, so that the effective components of the arsenic precipitating agent can be dispersed more evenly in the primary gallium-rich solution in the form of a colloidal precipitate, have a larger specific surface area, and have a better arsenic removal effect. The dispersed solution for preparing the suspension can use the post-electrolysis liquid produced by cyclone electrolysis, which can be recycled.

[0017] The present invention adds barium oxide, calcium oxide, magnesium oxide and cerium oxide to a hot alkaline solution with a pH value of more than 14 to generate a colloidal precipitate, which has a large specific surface area and has a good adsorption and removal effect on arsenic. In addition, the present invention uses a mixed alkaline arsenic precipitator to remove arsenic, and by virtue of the property that arsenic can react with calcium, magnesium, barium and cerium ions to generate arsenate precipitates with a large solubility product, it has a good selective removal effect on arsenic. Barium oxide and calcium oxide, magnesium oxide and cerium oxide are mixed and used. The microstructure of the arsenate complex salt formed by the mixed use of these four substances is more stable. Therefore, the use of a mixed arsenic precipitator to remove arsenic has a better effect than that of a single component, and can make the precipitation of arsenic more complete.

[0018] The arsenic precipitation agent of the present invention has the advantages of good gallium-arsenic separation effect, high arsenic removal rate, less gallium loss in the process, and lower impurity ion content in the solution after purification.

[0019] In the above method for separating and recovering gallium arsenic from gallium arsenide waste, preferably, when adding alkali and oxidant for selective leaching, the alkali is sodium hydroxide and the oxidant is hydrogen peroxide; the concentration of the sodium hydroxide is 40-200g / L, the mass concentration of hydrogen peroxide is 20-40%, the amount of hydrogen peroxide is 1.2-1.8 times the amount required to oxidize the arsenic element in gallium arsenide from -3 valence to +5 valence, and the ratio of the volume of the sodium hydroxide solution to the mass of the gallium arsenide waste is controlled to be 2-6mL / g during leaching, the leaching temperature is 30-50°C, and the leaching time is 0.5-1h. The leaching process is carried out under strong alkaline conditions, which can effectively avoid the generation of hydrogen arsenide gas. If the alkali concentration is too low, gallium-containing precipitates are easily generated, while excessive alkali concentration or high temperature will lead to excessive decomposition of hydrogen peroxide.

[0020] In the above method for separating and recovering gallium arsenide from gallium arsenide waste, preferably, the hydrogen peroxide is added slowly drop by drop into the leaching solution by using a peristaltic pump to control the addition rate. Hydrogen peroxide is unstable and easily degraded, so it needs to be added drop by drop to ensure its utilization rate.

[0021] In the above method for separating and recovering gallium and arsenic from gallium arsenide waste, preferably, the number of cyclic leaching is 5-10 times. If the number of cycles is low, the concentration of gallium in the leaching solution is low, which is not conducive to the subsequent electrolytic process; if the number of cycles is high, the concentration of gallium and arsenic will reach saturation, reducing the leaching rate and forming precipitates.

[0022] In the above method for separating and recovering gallium arsenic from gallium arsenide waste, preferably, in step (2), the circulating leaching mother liquor is first heated to 60-90°C, and the temperature of low-temperature standing cooling crystallization is 10-20°C, and the cooling crystallization time is 3-4h.

[0023] In the above method for separating and recovering gallium and arsenic from gallium arsenide waste, preferably, in the primary gallium-rich mother liquor, the concentration of gallium ions is 30-60 g / L, and the concentration of arsenic ions is less than 5 g / L; in the secondary gallium-rich mother liquor, the concentration of gallium ions is 30-60 g / L, and the concentration of arsenic ions is less than 0.1 g / L. 1. In the secondary gallium-rich mother liquor, if the gallium ion concentration is low, concentration polarization is likely to occur, reducing the current efficiency; if the arsenic ion concentration is high, there is a risk of forming arsine gas, and the purity of cathode gallium will be reduced. After two gallium-arsenic separations, it is beneficial to minimize the concentration of arsenic ions in the secondary gallium-rich mother liquor of cyclonic electrowinning.

[0024] In the above method for separating and recovering gallium arsenide from waste gallium arsenide, preferably, when recovering gallium by cyclonic electrowinning, a titanium sheet is used as a cathode and a current density is controlled to be 500-800A / m 2 , the electrolyte circulation flow rate is 100-300L / h, and the concentration of gallium ions after electrolysis is less than 5g / L. Titanium cathode has good alkali corrosion resistance. The current density needs to be controlled within a certain range. If the current density is too low, the production efficiency will be reduced, and if the current density is too high, it is easy to produce concentration polarization and reduce the current efficiency.

[0025] Since the theoretical precipitation potential of gallium is relatively negative, there are serious concentration polarization and hydrogen evolution side reactions during the electrolysis process, resulting in low current efficiency. Increasing the gallium concentration in the electrolyte is beneficial to improving the theoretical precipitation potential of gallium and alleviating concentration polarization, thereby improving the current efficiency. The presence of arsenic will also affect the electrolysis process of gallium. Therefore, minimizing the concentration of arsenic in the electrolyte is also beneficial to the electrolysis process of gallium. The present invention uses multiple cycles of leaching of alkali + oxidant to achieve high enrichment of gallium and arsenic. After the gallium-arsenic enriched solution is cooled and crystallized to remove arsenic, the gallium concentration in the primary gallium-rich mother liquor is high and the arsenic concentration is low, but a certain amount of arsenic will still exist. After the primary gallium-rich mother liquor of the present invention is subjected to secondary arsenic precipitation by an arsenic precipitation agent, the arsenic concentration in the secondary gallium-rich mother liquor is lower, which is more conducive to the cyclone electrolysis process of gallium.

[0026] In the method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention, the main reactions occurring are:

[0027] GaAs+4OH - +4H2O2=AsO4 3- +GaO2 - +6H2O;

[0028] AsO4 3- +3Na + =Na3AsO4↓;

[0029] GaO2 - +2H2O+3e - →Ga+4OH - .

[0030] Compared with the prior art, the advantages of the present invention are:

[0031] 1. The method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention adopts alkaline system leaching, the operating conditions are relatively mild, the reagent cost is low, the corrosion of strong acid to equipment and the generation of highly toxic hydrogen arsenide gas are avoided, the leaching rate and leaching rate are both high, and efficient and clean leaching of gallium arsenide waste can be achieved.

[0032] 2. The method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention adopts a circulating leaching method to enrich gallium, so that the leachate can be recycled while ensuring the leaching rate, thereby reducing the consumption of leaching agent, lowering the consumption of alkali and industrial water, and reducing the amount of tail liquid to be processed. The concentration of gallium in the circulating leachate is high, which is beneficial to improving the current efficiency of the subsequent electrolytic process and reducing energy consumption.

[0033] 3. The method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention adopts cooling crystallization to remove arsenic, which is easy to operate, has a simple process, low cost, lower energy consumption, and shorter time required. It avoids the use of a large amount of neutralizing precipitant, and also avoids the use of extractants or resins. Under the premise of ensuring that gallium in the solution is not lost, it has a good selective removal effect on arsenic.

[0034] 4. The method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention uses an arsenic precipitator to perform secondary arsenic precipitation on the primary gallium-rich mother liquor, which can achieve deep removal of arsenic in the liquid after cooling and crystallization, thereby further improving the current efficiency in the electrolytic deposition process, avoiding the generation of arsenic and arsine in the electrolytic deposition process, and facilitating the subsequent treatment of the tail liquid.

[0035] 5. The method for separating and recovering gallium arsenic from gallium arsenide waste of the present invention adopts cyclonic electrowinning to recover gallium in the solution, which has a significant inhibitory effect on concentration polarization, can inhibit the occurrence of hydrogen evolution side reaction, improve current efficiency and reduce energy consumption, and at the same time reduce the influence of impurity ions on gallium recovery, thereby improving the purity of cathode gallium. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 The present invention is a process flow chart of the method for separating and recovering gallium arsenic from gallium arsenide waste. DETAILED DESCRIPTION

[0038] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments.

[0039] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0040] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0041] Embodiment 1:

[0042] The gallium arsenide waste used in this embodiment is derived from the gallium arsenide grinding and polishing process, and has a complex composition. The chemical composition, phase structure and microscopic analysis results show that the gallium and arsenic contents are 3.03% and 3.39% respectively, in the form of GaAs, and the impurity elements aluminum, zirconium and silicon contain 28.12%, 17.01% and 7.54% respectively, in the form of α-Al2O3 and ZrSiO4. Each phase is evenly distributed, and there is no encapsulated embedded structure. The particle size is distributed in the range of 1-10μm, and it is difficult to separate physically.

[0043] For the above materials, the method for separating and recovering gallium arsenide from gallium arsenide waste in this embodiment is as follows: Figure 1 As shown, the following steps are included:

[0044] (1) Alkaline oxidation leaching: Under the conditions of NaOH concentration of 80 g / L, hydrogen peroxide excess coefficient of 1.3, leaching temperature of 30 °C, liquid-to-solid ratio of 4, stirring speed of 150 rpm, and reaction time of 40 min, the leaching rates of gallium and arsenic can reach 98.74% and 98.88%, respectively, while the leaching rates of aluminum and silicon are only 0.09% and 0.43%, respectively, achieving efficient and selective leaching of gallium and arsenic. The concentrations of gallium and arsenic in the leachate can reach 8.19 g / L and 8.77 g / L, respectively, while the concentrations of aluminum, silicon, and zirconium are 54.3 mg / L, 55.1 mg / L, and 0.2 mg / L, respectively. After 5 cycles of leaching, the concentrations of gallium and arsenic in the leachate reach 40.02 g / L and 38.44 g / L, respectively.

[0045] (2) Cooling crystallization for arsenic removal: The circulating leaching solution obtained in step (1) is first heated to 60°C, then cooled at 20°C for 4h, and the crystallized sodium arsenate precipitate residue and the arsenic removal liquid are filtered and separated. Under this condition, the arsenic removal rate can reach 95.85%, the mass fraction of arsenic in the sodium arsenate precipitate residue is 31.24%, and the mass fraction of gallium is only 0.22%. The concentration of gallium in the arsenic removal liquid is 39.87g / L, and the concentration of arsenic is reduced to 2.51g / L, thereby achieving selective arsenic removal.

[0046] (3) Cyclone electrowinning to recover gallium: The dearsenicated solution obtained in step (2) is placed in a cyclone electrowinning device, with the cathode material being Ti sheet and the current density being 500 A / m 2Under the conditions of electrolysis time of 6h and circulation flow rate of 200L / h, the cathode current efficiency can reach 36.44%, the gallium recovery rate is 91.35%, the gallium concentration in the liquid after electrolysis is 4.02g / L, the average cell voltage is 3.89V, and the power consumption is 9862kWh / t.

[0047] In this embodiment, the total recovery rate of gallium in the whole process is 90.20%, and the purity of the obtained metallic gallium can reach 99.994%.

[0048] Embodiment 2:

[0049] The gallium arsenide waste raw material used in this embodiment is the same as that in Example 1.

[0050] like Figure 1 As shown, the method for separating and recovering gallium arsenic from gallium arsenide waste in this embodiment comprises the following steps:

[0051] Steps (1)-(2) are the same as steps (1)-(2) in Example 1.

[0052] (3) Deep arsenic removal with arsenic precipitator: add arsenic precipitator to the cooled crystallized liquid obtained in step (2) for deep arsenic removal, wherein the effective component of the arsenic precipitator is barium oxide, and the arsenic precipitator is first dispersed by hot sodium hydroxide solution with a pH value of more than 14 to obtain a dispersed suspension with a mass concentration of 40%, and then added to the gallium-rich mother liquor at a temperature of 60°C and a mass ratio of arsenic precipitator to arsenic of 4:1, and stirred for 30 minutes, and the stirring speed is controlled to be 300r / min, and then aged, and the aging temperature is controlled to be 60°C, the aging time is 60min, and the aging stirring speed is 50r / min. After aging, the arsenic residue and the primary gallium liquid are separated by filtration, and the primary gallium liquid is subjected to the removal of excess arsenic precipitator by the impurity remover to obtain the dearsenified liquid, and the gallium ion concentration does not change significantly during the impurity removal. In this step, the arsenic removal rate is 96.76%, the gallium loss rate is 2.76%, the gallium concentration in the dearsenified liquid is 38.16g / L, and the arsenic concentration is 0.09g / L.

[0053] (4) Cyclone electrowinning to recover gallium: The dearsenicated solution obtained in step (3) is placed in a cyclone electrowinning device, with the cathode material being Ti sheet and the current density being 500 A / m 2 Under the conditions of electrolysis time of 6h and circulation flow rate of 200L / h, the cathode current efficiency can reach 38.76%, the gallium recovery rate is 92.73%, the gallium concentration in the liquid after electrolysis is 3.71g / L, the average cell voltage is 3.78V, and the power consumption is 9591kWh / t.

[0054] In this embodiment, the total recovery rate of gallium in the whole process is 89.03%, and the purity of the obtained metallic gallium can reach 99.995%.

[0055] Embodiment 3:

[0056] The gallium arsenide waste raw material used in this embodiment is the same as that in Example 1.

[0057] like Figure 1 As shown, the method for separating and recovering gallium arsenic from gallium arsenide waste in this embodiment comprises the following steps:

[0058] Steps (1)-(2) are the same as steps (1)-(2) in Example 1.

[0059] (3) deep arsenic removal with an arsenic precipitator: an arsenic precipitator is added to the cooled crystallized liquid obtained in step (2) for deep arsenic removal, wherein the arsenic precipitator comprises barium oxide, calcium oxide, magnesium oxide and cerium oxide, wherein the mass ratio of barium oxide, calcium oxide, magnesium oxide and cerium oxide is 5:1:1:1, and the arsenic precipitator is first dispersed with a hot sodium hydroxide solution having a pH value greater than 14 to obtain a dispersed suspension having a mass concentration of 40%, and then added to the gallium-rich mother liquor at a temperature of 60° C. and a mass ratio of the arsenic precipitator to arsenic of 4:1, and stirred for reaction for 30 minutes, with the stirring speed controlled at 300 r / min, and then aged, with the aging temperature controlled at 60° C., the aging time controlled at 60 min, and the aging stirring speed controlled at 50 r / min. After aging, the arsenic residue and the primary gallium liquid are separated by filtration, and the primary gallium liquid is treated with an impurity remover (sodium sulfate and sodium carbonate) to remove excess arsenic precipitator to obtain the dearsenicated liquid, wherein the gallium ion concentration does not change significantly during the impurity removal. In this step, the arsenic removal rate is 98.24%, the gallium loss rate is 3.49%, and the gallium concentration in the liquid after arsenic removal is 37.76 g / L, and the arsenic concentration is 0.03 g / L.

[0060] (4) Cyclone electrowinning to recover gallium: The dearsenicated solution obtained in step (3) is placed in a cyclone electrowinning device, with the cathode material being Ti sheet and the current density being 500 A / m 2 Under the conditions of electrolysis time of 6h and circulation flow rate of 200L / h, the cathode current efficiency can reach 40.49%, the gallium recovery rate is 93.06%, the gallium concentration in the liquid after electrolysis is 2.62g / L, the average cell voltage is 3.76V, and the power consumption is 9316kWh / t.

[0061] In this embodiment, the total recovery rate of gallium in the whole process is 88.49%, and the purity of the obtained metallic gallium can reach 99.996%.

[0062] Embodiment 4:

[0063] The gallium arsenide waste raw material used in this embodiment is the same as that in Example 1.

[0064] like Figure 1 As shown, the method for separating and recovering gallium arsenic from gallium arsenide waste in this embodiment comprises the following steps:

[0065] (1) Alkaline oxidation leaching: Under the conditions of NaOH concentration of 120 g / L, hydrogen peroxide excess coefficient of 1.3, leaching temperature of 30 °C, liquid-to-solid ratio of 4, stirring speed of 200 rpm, and reaction time of 30 min, the leaching rates of gallium and arsenic can reach 97.65% and 96.95%, respectively, while the leaching rates of aluminum and silicon are only 0.10% and 0.39%, respectively, achieving efficient and selective leaching of gallium and arsenic. The concentrations of gallium and arsenic in the leachate can reach 8.06 g / L and 8.12 g / L, respectively, while the concentrations of aluminum, silicon, and zirconium are 62.1 mg / L, 53.5 mg / L, and 0.2 mg / L, respectively. After 7 cycles of leaching, the concentrations of gallium and arsenic in the leachate reached 55.32 g / L and 53.26 g / L, respectively.

[0066] (2) Dearsenicification by cooling crystallization: The circulating leaching solution obtained in step (1) is first heated to 70°C, then cooled at 15°C for 4h, and the crystallized sodium arsenate precipitate residue and the dearsenicized liquid are filtered and separated. Under this condition, the arsenic removal rate can reach 94.32%, the mass fraction of arsenic in the sodium arsenate precipitate residue is 32.65%, and the mass fraction of gallium is only 0.35%. The concentration of gallium in the dearsenicized liquid is 54.46g / L, and the concentration of arsenic is reduced to 3.12g / L, thereby achieving selective removal of arsenic.

[0067] (3) Deep arsenic removal with arsenic precipitant: an arsenic precipitant is added to the cooled crystallized liquid obtained in step (2) for deep arsenic removal, wherein the arsenic precipitant comprises barium oxide, calcium oxide, magnesium oxide and cerium oxide, wherein the mass ratio of barium oxide, calcium oxide, magnesium oxide and cerium oxide is 5:1:1:1, and the mixture is directly added to the gallium-rich mother liquor at a temperature of 60° C. and a mass ratio of the arsenic precipitant to arsenic of 4:1, and the mixture is stirred for reaction for 30 minutes at a stirring speed of 300 r / min, and then aged at a controlled aging temperature of 60° C., an aging time of 60 minutes, and an aging stirring speed of 50 r / min. After aging, the mixture is filtered and separated to obtain an arsenic residue and a primary gallium liquid. The primary gallium liquid is treated with a decontamination agent (sodium sulfate and sodium carbonate) to remove excess arsenic precipitant to obtain a de-arsenicated liquid, wherein the gallium ion concentration does not change significantly during the decontamination. In this step, the arsenic removal rate was 91.24%, the gallium loss rate was 1.89%, and the gallium concentration in the liquid after arsenic removal was 54.18 g / L, and the arsenic concentration was 0.28 g / L.

[0068] (4) Gallium recovery by cyclone electrowinning: The dearsenicated solution obtained in step (3) is placed in a cyclone electrowinning device, with the cathode material being Ti sheet and the current density being 750 A / m 2 Under the conditions of electrolysis time of 4h and circulation flow rate of 300L / h, the cathode current efficiency can reach 41.94%, the gallium recovery rate is 90.46%, the gallium concentration in the liquid after electrolysis is 4.95g / L, the average cell voltage is 3.81V, and the power consumption is 9561kWh / t.

[0069] The total recovery rate of gallium in the whole process of this embodiment is 88.33%, and the purity of the obtained metallic gallium can reach 99.995%.

[0070] Embodiment 5:

[0071] The gallium arsenide waste raw material used in this embodiment is the same as that in Example 1.

[0072] like Figure 1 As shown, the method for separating and recovering gallium arsenic from gallium arsenide waste in this embodiment comprises the following steps:

[0073] Steps (1)-(2) are the same as steps (1)-(2) in Example 4.

[0074] (3) deep arsenic removal with an arsenic precipitator: an arsenic precipitator is added to the cooled crystallized liquid obtained in step (2) for deep arsenic removal, wherein the arsenic precipitator comprises barium oxide, calcium oxide, magnesium oxide and cerium oxide, wherein the mass ratio of barium oxide, calcium oxide, magnesium oxide and cerium oxide is 5:1:1:1, and the arsenic precipitator is first dispersed with a hot sodium hydroxide solution having a pH value greater than 14 to obtain a dispersed suspension having a mass concentration of 40%, and then added to the gallium-rich mother liquor at a temperature of 60° C. and a mass ratio of the arsenic precipitator to arsenic of 4:1, and stirred for reaction for 30 minutes, with the stirring speed controlled at 300 r / min, and then aged, with the aging temperature controlled at 60° C., the aging time controlled at 60 min, and the aging stirring speed controlled at 50 r / min. After aging, the arsenic residue and the primary gallium liquid are separated by filtration, and the primary gallium liquid is treated with an impurity remover (sodium sulfate and sodium carbonate) to remove excess arsenic precipitator to obtain the dearsenicated liquid, wherein the gallium ion concentration does not change significantly during the impurity removal. In this step, the arsenic removal rate is 99.24%, the gallium loss rate is 3.44%, and the gallium concentration in the liquid after arsenic removal is 53.53 g / L, and the arsenic concentration is 0.03 g / L.

[0075] (4) Gallium recovery by cyclone electrowinning: The dearsenicated solution obtained in step (3) is placed in a cyclone electrowinning device, with the cathode material being Ti sheet and the current density being 750 A / m 2 Under the conditions of electrolysis time of 4h and circulation flow rate of 300L / h, the cathode current efficiency can reach 45.81%, the gallium recovery rate is 92.37%, the gallium concentration in the liquid after electrolysis is 4.08g / L, the average cell voltage is 3.71V, and the power consumption is 9197kWh / t.

[0076] The total recovery rate of gallium in the whole process of this embodiment is 87.10%, and the purity of the obtained metallic gallium can reach 99.996%.

Claims

1. A method for separating and recovering gallium arsenic from gallium arsenide waste, characterized in that: The following steps are involved: (1) adding alkali and oxidant to gallium arsenide waste to selectively leach gallium arsenide waste to neutralize arsenic and gallium, and separating the leaching residue and the leaching liquid after the leaching is completed. After the leaching liquid is leached for multiple cycles, a circulating leaching mother liquor is obtained, and the concentrations of gallium ions and arsenic ions in the circulating leaching mother liquor are controlled to be 30-60 g / L; (2) heating the circulating leaching mother liquor obtained in step (1), and then cooling and crystallizing at low temperature, and separating and crystallizing after precipitation is complete to obtain sodium arsenate crystals and a primary gallium-rich mother liquor; (3) adding an arsenic precipitating agent to the primary gallium-rich mother liquor obtained in step (2) to perform secondary arsenic precipitation, and separating to obtain arsenic precipitation slag and secondary gallium-rich mother liquor; (4) recovering gallium ions from the secondary gallium-rich mother liquor obtained in step (3) by cyclonic electrowinning to obtain metallic gallium; The arsenic precipitation agent comprises barium oxide, calcium oxide, magnesium oxide and cerium oxide, and the mass ratio of barium oxide, calcium oxide, magnesium oxide and cerium oxide is (3-8): (0.1-1): (0.1-1): (0.1-1); The arsenic precipitating agent is first dispersed using a hot alkaline solution with a pH value of more than 14 to obtain a dispersed suspension with a mass concentration of 30-50%, and then added into the gallium-rich mother liquor once more.

2. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1, characterized in that: After the secondary arsenic precipitation, sulfate ions and / or carbonate ions are added to the secondary gallium-rich mother liquor for impurity removal to remove excess arsenic precipitation agent.

3. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1 or 2, characterized in that: When an alkali and an oxidant are added for selective leaching, the alkali is sodium hydroxide and the oxidant is hydrogen peroxide; the concentration of the sodium hydroxide is 40-200 g / L, the mass concentration of the hydrogen peroxide is 20-40%, the amount of hydrogen peroxide used is 1.2-1.8 times the amount required to oxidize the arsenic element in the gallium arsenide from -3 valence to +5 valence, and during leaching, the ratio of the volume of the sodium hydroxide solution to the mass of the gallium arsenide waste is controlled to be 2-6 mL / g, the leaching temperature is 30-50° C., and the leaching time is 0.5-1 h.

4. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 3, characterized in that: The hydrogen peroxide is added slowly drop by drop into the leaching solution by controlling the adding rate of the hydrogen peroxide using a peristaltic pump.

5. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1 or 2, characterized in that: The number of leaching cycles is 5-10 times.

6. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1 or 2, characterized in that: In step (2), the circulating leaching mother liquor is first heated to 60-90°C, and the temperature of the low-temperature cooling crystallization is 10-20°C, and the cooling crystallization time is 3-4h.

7. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1 or 2, characterized in that: In the primary gallium-rich mother liquor, the concentration of gallium ions is 30-60 g / L, and the concentration of arsenic ions is less than 5 g / L; in the secondary gallium-rich mother liquor, the concentration of gallium ions is 30-60 g / L, and the concentration of arsenic ions is less than 0.1 g / L.

8. The method for separating and recovering gallium arsenic from gallium arsenide waste according to claim 1 or 2, characterized in that: When recovering gallium by cyclonic electrowinning, titanium sheet is used as cathode and the current density is controlled at 500-800A / m 2 , the electrolyte circulation flow rate is 100-300L / h, and the concentration of gallium ions after electrolysis is less than 5g / L.

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