Method for extracting gallium from high-fluorine high-arsenic gallium-containing waste liquid

Abstract

The invention provides a method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid, and belongs to the technical field of metallurgy. The method comprises the following steps: adding potassium salt into the high-fluorine and high-arsenic gallium-containing waste liquid to carry out fluorine removal treatment, and filtering to obtain potassium fluosilicate and fluorine-removed filtrate; adding calcium salt into the defluorination filtrate to carry out arsenic removal treatment, and filtering to obtain calcium arsenate and arsenic-removed filtrate; and sequentially carrying out gallium deposition, alkali dissolution and electro-deposition treatment on the arsenic-removed filtrate to obtain metal gallium. According to the method, the processes of removing fluorine, arsenic and other trace impurities and extracting gallium are combined with the process of washing and recovering gallium, so that the loss of gallium is reduced, the recovery rate of gallium metal is improved, and the operation cost in industrial production is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid. Background Art

[0002] Gallium is one of the most important rare earth metals, prized for its unique physical and chemical properties. Since the 1980s, with the continuous advancement of science and technology, the applications of gallium have gradually expanded. In particular, compound semiconductor materials and special alloys composed of high-purity gallium and certain metals have become new technological support materials required by modern communications, electronic computers, space exploration, energy, and health sectors. Significant progress has been made in the military industry, with applications such as night vision devices, thermal imagers, large-scale integrated circuits, and fiber-optic communications.

[0003] Years of development have resulted in the generation of large quantities of gallium-containing semiconductor waste. Currently, gallium arsenide (GaAs) waste is the largest category of gallium-containing electronic waste recycled, primarily consisting of GaAs thin-film solar cell waste and wastewater generated during the manufacture of GaAs chips in the semiconductor industry. The presence of As in GaAs poses a threat to the environment and is difficult to separate, making direct recycling difficult. Currently, the main recycling processes are hydrometallurgy, pyrometallurgy, and bioleaching. Pyrometallurgy is limited by its high equipment and energy costs, while bioleaching has not been a mainstream process due to its low leaching efficiency. Hydrometallurgy has become the mainstream process for gallium extraction due to its low cost, low waste gas emissions, high gallium recovery rate, and strong selectivity.

[0004] Currently, there are few reports on methods for extracting gallium from high-fluorine, high-arsenic gallium-containing wastewater. Fluoride ions in the wastewater combine with gallium ions, hindering the formation of gallium hydroxide precipitates. Furthermore, this also affects arsenic removal, resulting in low gallium recovery rates. Therefore, developing a method for extracting gallium from high-fluorine, high-arsenic gallium-containing wastewater is of great significance. Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides a method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid, aiming to solve the technical problem of low gallium recovery rate in high-fluorine and high-arsenic gallium-containing waste liquid.

[0006] In a first aspect, the present application provides a method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid, comprising the following steps: Adding potassium salt to the high-fluorine, high-arsenic gallium-containing wastewater for defluorination treatment, and obtaining potassium fluorosilicate and defluorination filtrate after filtration; adding calcium salt to the defluorination filtrate to remove arsenic, and obtaining calcium arsenate and the defluorination filtrate after filtration; The arsenic removal filtrate is sequentially treated with neutralization, alkali dissolution and electrodeposition to obtain metallic gallium.

[0007] Preferably, the molar ratio of potassium element in potassium salt to fluorine element in high-fluorine, high-arsenic, gallium-containing waste liquid is (0.5~5):1.

[0008] Preferably, the potassium salt includes at least one of KCl, K2CO3, K2SO4, K2SO3, KClO, KClO3, K3PO4, and KNO3.

[0009] Preferably, the molar ratio of calcium in the calcium salt to arsenic in the defluorination filtrate is (2-10):1.

[0010] Preferably, the calcium salt includes at least one of calcium chloride, calcium oxide, calcium hydroxide and calcium carbonate.

[0011] Preferably, potassium fluorosilicate is washed with dilute acid to obtain an acid washing liquid, and the acid washing liquid is refluxed into the high-fluorine, high-arsenic, gallium-containing waste liquid.

[0012] Preferably, the concentration of the dilute acid is 0.1-1 mol / L; the dilute acid includes any one of hydrochloric acid, sulfuric acid, and nitric acid; and the solid-liquid ratio of potassium fluorosilicate to the dilute acid is 1:(1-6).

[0013] Preferably, the calcium arsenate is washed with a liquid alkali solution to obtain an alkaline washing liquid, and the alkaline washing liquid is refluxed into the defluorination filtrate.

[0014] Preferably, the concentration of the liquid alkali solution is 10wt%~32wt%, and the solid-liquid ratio of calcium arsenate to the liquid alkali solution is 1:(1~6).

[0015] Preferably, the conditions for gallium precipitation treatment are: adjusting the pH to 5-6; the conditions for alkali dissolution treatment are: adjusting the pH to 11-13; the conditions for electrodeposition treatment are: adjusting the voltage to 2-5V, the water bath temperature to 20-40°C, and the electrolysis time to 24-72h.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention addresses the impact of high fluorine and high arsenic content in gallium-containing waste liquid on gallium extraction. The present invention utilizes a process for removing fluorine, arsenic, and other trace impurities, extracting gallium, and combining it with a process for washing and recovering gallium. This reduces gallium loss (gallium loss throughout the entire process is controlled within 5%), improves the recovery rate of gallium metal, and significantly reduces operating costs in industrial production. Furthermore, potassium fluorosilicate obtained in the fluorine removal process is also a product that can be sold as a by-product in the gallium extraction process, thereby increasing revenue and reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a process flow chart of the method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater; Figure 2The present invention is a process flow chart of one embodiment of the method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater. DETAILED DESCRIPTION

[0018] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0019] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0020] See also Figure 1 and Figure 2 The present invention provides a method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater, comprising the following steps: S1, defluorination: adding potassium salt to the high-fluorine, high-arsenic gallium-containing waste liquid for defluorination treatment, filtering to obtain potassium fluorosilicate and defluorination filtrate; washing the potassium fluorosilicate with dilute acid to obtain an acid washing liquid, and returning the acid washing liquid to the high-fluorine, high-arsenic gallium-containing waste liquid; S2, arsenic removal: adding calcium salt to the defluorination filtrate to remove arsenic, filtering to obtain calcium arsenate and the arsenic removal filtrate; washing the calcium arsenate with a liquid alkali solution to obtain an alkaline washing solution, and returning the alkaline washing solution to the defluorination filtrate; S3, gallium precipitation: adding dilute acid to the arsenic removal filtrate to adjust the pH to 5-6 for gallium precipitation to obtain gallium hydroxide precipitate; S4, alkali dissolution: adding liquid alkali solution to the gallium hydroxide precipitate to adjust the pH to 11-13, dissolving the gallium hydroxide, and filtering to obtain a gallium-rich solution; S5. Electrodeposition: Electrodepositing the gallium-rich solution to obtain metallic gallium.

[0021] The present invention does not specifically limit the source of high-fluorine, high-arsenic gallium-containing wastewater. Semiconductor material production, particularly the manufacture of gallium arsenide (GaAs), generates a large amount of gallium-containing wastewater. These wastewaters typically contain high concentrations of arsenic and fluorine, primarily from the following sources: Arsenic-containing wastewater is generated during the manufacture of GaAs wafers, and large amounts of acidic solutions containing fluorine and arsenic are used during the etching and cleaning of semiconductor wafers.

[0022] In some embodiments of the present invention, in step S1, the molar ratio of potassium in the potassium salt to fluorine in the high-fluorine, high-arsenic gallium-containing wastewater is (0.5-5):1; the potassium salt includes at least one of KCl, K2CO3, K2SO4, K2SO3, KClO, KClO3, K3PO4, and KNO3. Fluoride ions in the high-fluorine, high-arsenic gallium-containing wastewater will combine with gallium ions, hindering the formation of gallium hydroxide precipitates from gallium ions to a certain extent. In addition, it will also affect the removal of arsenic. Therefore, potassium salt is added first to remove the interference of fluorosilicate ions with subsequent processes. The reaction equation is: H2SiF6 + 2K - →K2SiF6↓+ 2H - . The present invention has no special restrictions on the filtering process, and the filtering technical scheme familiar to those skilled in the art can be adopted. The present invention obtains potassium fluorosilicate and defluoridated filtrate after filtration. Potassium fluorosilicate can be sold as a by-product in the gallium extraction process to increase income and reduce production costs. There is a small amount of gallium physically included in the potassium fluorosilicate filter residue and attached to the surface. By washing the potassium fluorosilicate with dilute acid to further recover gallium, the loss of gallium can be guaranteed to be <0.5%. The concentration of the dilute acid is 0.1~1 mol / L; the dilute acid includes any one of hydrochloric acid, sulfuric acid, and nitric acid; the solid-liquid ratio of potassium fluorosilicate to dilute acid is 1: (1~6). The washing liquid obtained after washing potassium fluorosilicate with dilute acid will also contain physically doped fluorine elements. In order to prevent the impact on the subsequent process, the washing liquid needs to be returned to the high-fluorine, high-arsenic gallium-containing waste liquid in the previous stage to continue defluoridation.

[0023] In some embodiments of the present invention, in step S2, the molar ratio of calcium in the calcium salt to arsenic in the defluorination filtrate is (2-10):1; the calcium salt comprises at least one of calcium chloride, calcium oxide, calcium hydroxide, and calcium carbonate. The calcium salt and arsenic form an insoluble precipitate, calcium arsenate, thereby removing arsenic. The reaction equation is: 2H3AsO4 + 3Ca 2+ = Ca3(AsO4)2↓ + 6H + Small amounts of gallium are physically included in and attached to the surface of calcium arsenate slag. By washing the calcium arsenate with liquid caustic soda to further recover gallium, gallium loss can be maintained at less than 2%. The concentration of the liquid caustic soda ranges from 10wt% to 32wt%, and the solid-to-liquid ratio of calcium arsenate to liquid caustic soda is 1:(1-6). The washing liquid obtained after washing the calcium arsenate with liquid caustic soda also contains physically doped arsenic. To prevent this from impacting subsequent processes, the washing liquid must be returned to the defluorination filtrate for continued arsenic removal.

[0024] In some embodiments of the present invention, in step S3, the concentration of the dilute acid is 0.1-1 mol / L; the dilute acid includes any one of hydrochloric acid, sulfuric acid, and nitric acid. The acid acts on the gallate solution to generate Ga(OH)3. The reaction equation is: Ga 3+ + 3H2O = Ga(OH)3↓ +3H+ .

[0025] In some embodiments of the present invention, in step S4, the concentration of the liquid caustic soda solution is 10 wt% to 32 wt%. The precipitated gallium is dissolved in the liquid caustic soda, which can remove other impurities such as iron. After filtration and separation, a high-purity gallium-rich liquid is obtained. Gallium hydroxide is an amphoteric hydroxide that is more acidic than alkaline and is insoluble in water, but easily soluble in alkali metal hydroxide solutions. When the precipitated gallium (i.e., gallium hydroxide) is added to the liquid caustic soda, the following reaction occurs: Ga(OH)3+OH - →[Ga(OH)4] - .

[0026] In some embodiments of the present invention, in step S5, the electrodeposition is specifically as follows: using a stainless steel plate as an electrode, electrolyzing for 24 to 72 hours at a voltage of 2 to 5 V and a water bath temperature of 20 to 40°C, and depositing gallium ions in the gallium-rich solution onto the cathode to obtain gallium metal. The reaction equation of gallium ions in the gallium-rich solution at the cathode is: GaO2 - + 2H2O + 3e - = Ga↓ + 4OH - . In order to further illustrate the present invention, the following examples are given below to provide a detailed description.

[0027] Example 1 The imported gallium-containing waste liquid is used as the raw material, and its composition is shown in Table 1. The gallium-containing waste liquid mainly contains a large amount of F, Si, and As.

[0028] A method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid comprises the following steps: (1) 120 g of potassium chloride was added to 650 mL of gallium-containing wastewater (the molar ratio of potassium in potassium salt to fluorine in high-fluorine and high-arsenic gallium-containing wastewater was 0.54:1), and the reaction was carried out in a greenhouse for 2 h to remove fluorine. After filtration, potassium fluorosilicate precipitate and defluorine filtrate were obtained. The sampling test results are shown in Table 1. The fluorine removal rate was 96.66%, but the gallium loss was 6.8%; 102.46 g of the above potassium fluorosilicate was washed with 400 ml of 1 mol / L sulfuric acid at room temperature for 2 h. The resulting pickling solution was returned to the high-fluorine, high-arsenic gallium-containing waste liquid, and the washed potassium fluorosilicate was sold as a by-product. The sampling and test results are shown in Table 2. The gallium recovery rate was 99.59%, and the gallium loss was controlled below <0.5%.

[0029] Table 1

[0030] Table 2

[0031] (2) 46.3 g of lime was added to the defluorination filtrate to precipitate arsenic, wherein the molar ratio of calcium in the lime to arsenic in the defluorination filtrate was 4.1:1. After filtration, calcium arsenate precipitate and defluorination filtrate were obtained. The sampling test results are shown in Table 3. The arsenic removal rate was 99.16%, and the gallium loss was 3.8%. Calcium arsenate was washed with 32% liquid caustic soda at a solid-liquid ratio of 1:5 at room temperature for 2 h. The alkaline washing liquid was obtained after filtration. The alkaline washing liquid was returned to the defluorination filtrate, and the calcium arsenate slag was stored. The sampling and test results are shown in Table 4. The gallium recovery rate was 98.42%, and the gallium loss was controlled below <2%.

[0032] Table 3

[0033] Table 4

[0034] (3) 2M sulfuric acid was added to the upstream arsenic removal filtrate to adjust the pH to 5.6 for gallium precipitation, and the gallium hydroxide precipitate and waste liquid were obtained by filtration. The waste liquid was discharged after treatment; 12% liquid caustic soda was added to the gallium hydroxide precipitate to adjust the pH to 13 for dissolution to obtain a high-purity gallium-rich liquid. The sampling and test results are shown in Table 5. The gallium precipitation rate was 99.9%, the gallium dissolution rate was 99.87%, and the arsenic and iron dissolution rates were very low, only 1.13% and 0.3% respectively. After filtration and separation, a high-purity gallium-rich liquid was obtained. The gallium loss in this process was controlled below <0.5%.

[0035] Table 5

[0036] (4) The high-purity gallium-rich liquid was electrolytically deposited onto the cathode using a stainless steel plate as an electrode at a voltage of 5 V and a temperature of 40°C in a water bath to obtain gallium metal. The test results are shown in Table 6. After electrolysis at 40°C for 28 hours, 12.8 g of pure gallium was obtained from the gallium-rich liquid, with an electrolysis rate of 99.99%.

[0037] Table 6

[0038] In this embodiment, the method for extracting gallium from high-fluorine and high-arsenic gallium-containing waste liquid has a final gallium extraction rate of 89.5%. The gallium recovery rate through fluorine and arsenic removal slag pickling is 9.81% (this part of gallium can be returned to the previous stage to avoid loss). The total gallium loss in this process is maintained at about 1%.

[0039] Comparative Example 1 Using external gallium-containing waste liquid as raw material, the composition of which is shown in Table 7, lime was added to 400 mL of the gallium-containing waste liquid for precipitation reaction for 2 hours to remove arsenic. The molar ratio of calcium in the lime to arsenic in the gallium-containing waste liquid was 15.23:1. After filtration, arsenic-removed filtrate and calcium arsenate were obtained. The sampling and test results are shown in Table 7. The arsenic removal rate of the gallium-containing waste liquid after lime arsenic removal reached 99.88%, but it also resulted in a loss of 99.89% of Ga.

[0040] Liquid caustic soda with a solid-liquid ratio of 1:5 and a mass concentration of 32% was used to dissolve the calcium arsenate slag. The reaction was carried out at room temperature for 2 hours. The sampling and test results are shown in Table 7. When the liquid caustic soda was used to dissolve the calcium arsenate slag, only 38.16% of gallium was recovered, and 15.93% of arsenic was introduced.

[0041] Table 7

[0042] In the presence of excess hydrofluoric acid, arsenic and gallium exist in the form of fluoroarsenic acid and fluorogallic acid, respectively. Excess calcium hydroxide is added to react with fluoroarsenic acid and fluorogallic acid, respectively, to generate calcium fluoroarsenate and calcium fluorogallic acid precipitate, resulting in gallium loss. The reaction equation is as follows: 2HAsF6+3Ca(OH)2=Ca3(AsF6)2+6H2O; 2H3GaF6+3Ca(OH)2=Ca3(GaF6)2+ 6H2O.

[0043] However, calcium fluoroarsenate and calcium fluorogallate precipitates are almost insoluble in liquid caustic soda, so gallium cannot be recovered to reduce losses. - Reducing the impact of hydrofluoric acid and the influence of F on arsenic removal by calcium hydroxide and gallium recovery by pickling can significantly improve the impurity removal rate and gallium recovery rate.

[0044] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater, characterized in that: The following steps are involved: Adding potassium salt to the high-fluorine, high-arsenic gallium-containing wastewater for defluorination treatment, and obtaining potassium fluorosilicate and defluorination filtrate after filtration; adding calcium salt to the defluorination filtrate to remove arsenic, and filtering to obtain calcium arsenate and the defluorination filtrate; The arsenic removal filtrate is sequentially treated with gallium precipitation, alkali dissolution and electrodeposition to obtain metallic gallium.

2. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The molar ratio of the potassium element in the potassium salt to the fluorine element in the high-fluorine, high-arsenic, gallium-containing waste liquid is (0.5~5):

1.

3. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The potassium salt includes at least one of KCl, K2CO3, K2SO4, K2SO3, KClO, KClO3, K3PO4, and KNO3.

4. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The molar ratio of calcium in the calcium salt to arsenic in the defluorination filtrate is (2-10):

1.

5. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The calcium salt includes at least one of calcium chloride, calcium oxide, calcium hydroxide and calcium carbonate.

6. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The potassium fluorosilicate is washed with dilute acid to obtain an acid washing liquid, which is refluxed into the high-fluorine, high-arsenic, gallium-containing waste liquid.

7. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 6, characterized in that: The concentration of the dilute acid is 0.1-1 mol / L, and the dilute acid includes any one of hydrochloric acid, sulfuric acid, and nitric acid; the solid-liquid ratio of the potassium fluorosilicate to the dilute acid is 1:(1-6).

8. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The calcium arsenate is washed with a liquid alkali solution to obtain an alkali washing solution, and the alkali washing solution is refluxed into the defluorination filtrate.

9. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 8, characterized in that: The concentration of the liquid alkali solution is 10wt%~32wt%, and the solid-liquid ratio of the calcium arsenate to the liquid alkali solution is 1:(1~6).

10. The method for extracting gallium from high-fluorine and high-arsenic gallium-containing wastewater according to claim 1, characterized in that: The conditions for the gallium precipitation treatment are: adjusting the pH to 5-6; the conditions for the alkali dissolution treatment are: adjusting the pH to 11-13; the conditions for the electrodeposition treatment are: adjusting the voltage to 2-5V, the water bath temperature to 20-40°C, and the electrolysis time to 24-72h.

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