Method for comprehensively recovering indium, gallium and phosphorus from oily cutting mixed waste

Abstract

The invention relates to the field of metal recovery, and particularly discloses a method for comprehensively recovering indium, gallium and phosphorus from oily cutting mixed waste, which comprises the following steps: oxidizing and calcining the oily cutting mixed waste to obtain a mixed oxide; grinding and pulping the mixed oxide by adopting dilute sulphuric acid to obtain a pulpified mixed solution; the pulpified mixed solution is subjected to an ore pulp diaphragm electrolytic leaching method, a sulfuric acid electrolytic leaching solution containing In2 (SO4) 3, Ga2 (SO4) 3 and H3PO4 is obtained in a cathode area, electrodeposited metal indium is obtained on a cathode, and anode mud sediment containing silicon dioxide and aluminum oxide is obtained on an anode area and an anode; extracting indium from the sulfuric acid electrolytic leaching solution, neutralizing the indium extraction raffinate, hydrolyzing and precipitating gallium, and continuously neutralizing and precipitating by using lime water or calcium oxide to obtain calcium phosphate or calcium superphosphate; the method has the advantages of being efficient, low in cost and free of pollution and comprehensively recovering indium, gallium and phosphorus from the waste containing silicon dioxide, aluminum oxide, grease, indium phosphide and gallium phosphide.

Description

Technical Field

[0001] This application relates to the field of metal recycling, and more specifically, it relates to a method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting mixed waste. Background Technology

[0002] With the development of modern industry, especially the rapid rise of high-tech and new energy industries, the demand for rare metals is increasing. Indium and gallium, as rare metals, have wide applications in many high-tech fields such as medicine and health, national defense, aerospace, and electronics and information industries. For example, indium is mainly used to manufacture ITO thin film materials, low-melting-point alloys and solders, semiconductor compound materials, and indium alloys; while gallium, due to its unique physical and chemical properties, plays an important role in solar cells, LEDs, integrated circuits, and other fields.

[0003] However, indium and gallium are rare and dispersed metals without independent deposits. Their abundance in nature is extremely limited, mainly occurring as an associated mineral in lead-zinc mines, bauxite, and copper mines. Their geological reserves are small, but their applications are wide-ranging, making it difficult to meet the industry's growing demand for these rare metals. Recovering indium and gallium from secondary resources is an important supplement to their resources, making the recovery and processing of these metal raw materials particularly important.

[0004] Indium phosphide (IPS) and gallium phosphide (GaP) crystals with silicon dioxide (SiO2) or aluminum oxide (ACO) as substrates are mainly used in photovoltaic power generation and LED energy-saving lamps. Although these crystals are not very hard, they are brittle and require cutting or grinding with lubricating oil. This process produces a certain amount of oily cutting and grinding waste, which contains grease. In addition, since silicon dioxide and aluminum oxide are used as substrate materials and are introduced during the production of IPS and GaP, the waste also contains a certain amount of silicon dioxide and aluminum oxide. This results in a mixed waste of silicon dioxide, aluminum oxide, IPS, and GaP. Furthermore, the cleaning of quartz boats used when pulling IPS or GaP single crystals also produces a certain amount of waste containing IPS or GaP. The above mixed waste contains silicon dioxide, aluminum oxide, IPS, and GaP, making it difficult to comprehensively recover the indium, gallium, and phosphorus components.

[0005] Currently, there are some studies and literature documenting the recovery of rare metal elements such as indium and gallium. One method involves vacuum heating decomposition, where InP is first decomposed at 800-1200℃, metallic indium and phosphorus vapor are condensed at 400-500℃, and then cooled to 250-300℃ to recover red phosphorus and cast indium ingots. Another method uses a binary crystalline salt melt of MClxNCly at 450-700℃ under inert gas protection to melt indium phosphide, decomposing it to obtain metallic indium liquid and phosphorus vapor. The crystalline salt melt and metallic indium are then solidified at 50-100℃, and the phosphorus vapor is discharged with the inert gas and condensed for recovery of elemental phosphorus. Current research also employs a sulfation roasting method, roasting indium phosphide, dissolving it in water to obtain In2(SO4)3 and H3PO4 solutions, then electrolyzing the refined indium, and oxidizing the resulting phosphorus vapor with air to P2O5 for recovery. Some technologies also employ atmospheric pressure hydrochloric acid or sulfuric acid oxidation leaching, followed by replacement of sponge indium with metallic zinc or aluminum, and then neutralization with ammonia water followed by precipitation to recover zinc or aluminum phosphates and ammonium phosphates.

[0006] However, the materials used in the above methods are all single pure indium phosphide waste containing 79% indium and 21% phosphorus. This is significantly different from the mixed waste containing silicon, aluminum, indium, gallium, phosphorus, and lubricating oil in this application, not only in composition but also in the content of indium phosphide and gallium phosphide. When vacuum high-temperature decomposition is used, the obtained metallic indium will be mixed with silicon dioxide and aluminum oxide, and the indium and gallium will form an alloy, requiring further separation. If the crystal salt melt method is used, the mixed waste contains a large amount of high-melting-point silicon dioxide and aluminum oxide that cannot be melted, resulting in low decomposition efficiency of indium phosphide and gallium phosphide. When the sulfation roasting method is used, the water-dissolved indium sulfate and gallium sulfate solution will also contain a considerable amount of silica gel, affecting solid-liquid separation. The hydrochloric acid or sulfuric acid oxidation leaching method cannot rule out the influence of silica gel or aluminum colloid on the extraction of indium and gallium.

[0007] New recycling methods need to be studied for waste containing silicon dioxide, aluminum oxide, grease, indium phosphide, and gallium phosphide to recover indium, gallium, and phosphorus. Summary of the Invention

[0008] In order to comprehensively recover indium, gallium and phosphorus from waste containing silicon dioxide, aluminum oxide, grease and indium phosphide and gallium phosphide, this application provides a method for comprehensively recovering indium, gallium and phosphorus from oily cutting mixed waste.

[0009] This application provides a method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting mixed waste, employing the following technical solution: A method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting waste includes the following steps: S1. Oxidize and calcine the oily cutting waste to obtain a non-oily mixed oxide containing silicon, aluminum, indium, gallium, and phosphorus; S2. Grind the mixed oxides from step S1 into a slurry using dilute sulfuric acid to obtain a slurry mixture. S3. The slurry mixture in step S2 is subjected to slurry membrane electrolytic leaching to obtain sulfuric acid electrolytic leaching solution containing In2(SO4)3, Ga2(SO4)3 and H3PO4 in the cathode area, indium is electrolyzed on the cathode, and anode mud deposit containing silicon dioxide and aluminum oxide is obtained in the anode area and on the anode. S4. Extract indium from the sulfuric acid electrolytic leaching solution obtained in the cathode region in step S3, and then neutralize and hydrolyze the obtained indium extraction residue to precipitate gallium. Filter to obtain gallium hydroxide precipitate and phosphorus-containing filtrate. Add lime water or calcium oxide alkali to the filtrate to precipitate calcium phosphate or superphosphate.

[0010] By adopting the above technical solution, the mixed waste is first oxidized and calcined to convert indium phosphide and gallium phosphide into indium oxide, gallium oxide and phosphorus pentoxide. This is beneficial for subsequent electrolytic leaching of sulfuric acid slurry. Moreover, the oil in the mixed waste is burned as completely as possible, and even if there is any residue, it is only a small amount of carbon black. Then, dilute sulfuric acid is used to make slurry so that indium, gallium and phosphorus form the corresponding sulfates. Then, the membrane electrolytic leaching treatment in step S3 is carried out to obtain sulfuric acid electrolytic leaching solution containing In2(SO4)3, Ga2(SO4)3 and H3PO4 in the cathode area. At the same time, some indium is electrodeposited on the cathode, while most of silicon dioxide and aluminum oxide are deposited in the anode area. Then, after extracting indium from the sulfuric acid electrolytic leaching solution, gallium is precipitated in the residual liquid. Subsequently, phosphorus is precipitated again, and finally, the comprehensive recovery of indium, gallium and phosphorus in silicon and aluminum-containing waste is achieved.

[0011] Moreover, by using the method in this application, some indium is obtained by electrodeposition on the cathode in diaphragm electrolysis, and then extracted again in the subsequent sulfuric acid electrolysis leaching solution to obtain indium, and then gallium is precipitated. At the same time, most of the anode region contains silicon dioxide and aluminum oxide, thus achieving comprehensive recovery of the above substances with high recovery efficiency.

[0012] Optionally, step S1 specifically involves oxidizing and calcining the oily cutting waste at a temperature of 400±50℃. After the calcination time continues until the grease in the oily cutting waste no longer burns, the oxidation and calcination time is extended by 30-40 minutes to obtain a mixed oxide.

[0013] Optionally, in step S1, calcination is carried out under normal pressure air, oxygen-enriched air, or a mixture of hydrogen peroxide, with the amount of hydrogen peroxide added being 5-10% of the amount of oily cutting waste. More preferably, the oxidation and calcination are carried out under oxygen-enriched air conditions with an oxygen volume content of 32-36% or under conditions mixed with hydrogen peroxide.

[0014] By adopting the above technical solution, high-temperature oxidation and calcination can not only completely burn off the grease in the mixed waste, but also convert indium phosphide and gallium phosphide into indium oxide, gallium oxide, and phosphorus pentoxide, thus facilitating subsequent electrolytic leaching of sulfuric acid slurry. Especially under oxygen-enriched air or hydrogen peroxide conditions, the phosphorus vapor generated by the decomposition of indium phosphide and gallium phosphide is rapidly oxidized to phosphorus pentoxide, avoiding the generation of phosphorus vapor and H3P gas, reducing environmental pollution, and making it more environmentally friendly.

[0015] Optionally, in step S2, the solid-liquid ratio of dilute sulfuric acid to mixed oxides is 1:(2-3); and the pH of the prepared slurry mixture is 1-2.

[0016] Optionally, during the diaphragm electrolytic leaching treatment of the slurry in step S3, the electrolytic leaching temperature is 30±10℃, and the anode current density is 300-400A / m. 2 The cathode current density is 100-200 A / m 2 .

[0017] By adopting the above technical solution, compared with the commonly used sulfuric acid or hydrochloric acid leaching, which results in a higher content of colloidal silicon or colloidal aluminum in the leaching solution, making the leaching solution difficult to filter and affecting the extraction and separation of indium, this application uses a diaphragm electrolytic leaching method, which allows the silica gel and aluminum colloidal negative ions (SiO3) to be present. 2- (AlO2) - The discharge neutralizes the anolyte in the anode region and on the anode, as well as oxidize it with the generated oxygen, depositing it as anode mud at the bottom of the anode region. 3+ Ga 3+ The indium passes through the diaphragm and enters the cathode region. Under the low current density electrolysis conditions of indium, some of the indium... 3+ At the cathode, gallium is electrolytically dissolved as metallic indium, while gallium cannot be electrolytically dissolved or is difficult to dissolve and remains in the electrolytic leaching solution in the cathode region, separating from indium. Sulfuric acid and phosphoric acid in the electrolytic leaching solution are both present in the anode and cathode regions.

[0018] Optionally, in step S3, the slurry diaphragm electrolytic leaching method is implemented by a diaphragm electrolysis device. The cathode of the diaphragm electrolysis device is a stainless steel plate, and an electrolyte overflow port is provided at the top of the cathode area. The anode is a graphite or titanium alloy plate, and a stirring device is provided in the anode area. A bottom flow outlet controlled by a valve is provided at the bottom. During the slurry diaphragm electrolytic leaching process, the obtained slurry mixture is continuously added above the anode zone for stirring and electrolytic leaching. The sediment at the bottom of the anode zone is discharged through the underflow outlet and returned to step S2 for grinding and pulping until the indium and gallium contents in the discharged underflow sediment are both less than 0.03 wt%. The valve at the underflow outlet of the anode zone is then closed to stop the backflow. The underflow sediment in the anode zone is filtered, and the filtrate is returned for grinding and pulping in step S2. The sulfuric acid electrolytic leaching solution continuously overflows from the cathode area and returns to step S2 for grinding and pulping until the indium content of the overflowing sulfuric acid electrolytic leaching solution is ≥500mg / L. Then, the return process stops, and step S3 is performed.

[0019] By adopting the above technical solution, the continuously returning electrolytic leaching process ensures that the mixed waste in the pulping solution is thoroughly and repeatedly leached, increasing the leaching rate of indium, gallium, and phosphorus. Simultaneously, it continuously enriches indium, gallium, and phosphorus components, facilitating subsequent recovery processes. The final electrodeposited material in the anode region has a small filtration volume, is easy to filter, and, more importantly, contains low-valence components, resulting in a high overall electrolytic leaching rate. Meanwhile, some metallic indium can be directly obtained at the cathode, and the overflow electrolyte contains low levels of silicon and aluminum, facilitating indium extraction and recovery, as well as the filtration of hydrolyzed gallium and superphosphate.

[0020] Optionally, in step S4, after filtering the obtained sulfuric acid electrolytic leachate, indium is extracted using P204 kerosene extractant, and then back-extracted with hydrochloric acid to obtain indium-containing hydrochloric acid back-extraction solution, which is then returned for back-extraction until indium in the indium-containing hydrochloric acid back-extraction solution is ≥10g / L, after which it is removed and replaced with a metal displacement agent to obtain metallic indium.

[0021] By adopting the above technical solution, the obtained sulfuric acid electrolytic leaching solution is first extracted with P204 kerosene extractant to extract indium, and the indium ions in the leaching solution are transferred from the aqueous phase to the organic phase, so as to achieve the separation and recovery of indium from gallium and other elements.

[0022] Optionally, in step S4, the pH of the indium extraction residue is first adjusted to 5.2-5.4 to hydrolyze gallium and precipitate it as gallium hydroxide. After filtration, lime water or calcium oxide is added to the filtrate to continue neutralizing until the pH is 6-7, and calcium phosphate or superphosphate is precipitated.

[0023] Optionally, in step S4, sodium hydroxide, sodium carbonate, or sodium bicarbonate may be added to the indium extraction residue to adjust the pH to 5.2-5.4.

[0024] By employing the above technical solution, the indium extraction residue is first neutralized with sodium alkali to precipitate gallium hydroxide. Phosphoric acid in the residue remains in the solution as sodium phosphate, separating it from gallium. Then, neutralization with lime water or calcium oxide yields calcium phosphate precipitate, achieving separate precipitation and recovery of gallium and calcium phosphate. This prevents the simultaneous precipitation of gallium hydroxide and superphosphate when the indium extraction residue is directly neutralized with lime water or calcium oxide, thus ensuring effective separation and recovery.

[0025] Optionally, after dissolving the gallium hydroxide precipitate in step S4 with hydrochloric acid, if the gallium content after dissolution is less than 1 g / L, it is extracted with tributyl phosphate kerosene extractant, back-extracted with ammonium sulfate solution to enrich the gallium, and then replaced with a metal replacement agent to obtain metallic gallium. When the gallium content of the gallium hydroxide precipitate after dissolving it in hydrochloric acid in step S4 is ≥1g / L, gallium is directly replaced by a metal displacement agent to obtain metallic gallium.

[0026] Optionally, the metal displacement agent may be zinc or aluminum.

[0027] Optionally, in step S4, the sulfuric acid electrolytic leaching solution contains SiO2 ≤ 300 mg / L and Al2O3 ≤ 300 mg / L.

[0028] In summary, this application has the following beneficial effects: This application employs an oxidation calcination, dilute sulfuric acid pulping, and continuous circulating electrolytic leaching of the diaphragm slurry. This ensures that the indium, gallium, and phosphorus in the mixed waste after oxidation calcination are in oxide form, making them easy to electrochemically leach with sulfuric acid. Then, diaphragm electrolytic leaching is performed. In addition to obtaining some metallic indium at the cathode, the electrolytic overflow containing a certain concentration of indium, gallium, and phosphorus sulfate is first extracted and recovered with P204 kerosene extractant. The extraction residue is then neutralized and hydrolyzed with sodium alkali to precipitate gallium. After filtration, it is neutralized and precipitated with lime water or calcium oxide to precipitate superphosphate. Due to electrochemical oxidation in the anode area and on the anode, silicon and aluminum are electrodeposited as silicon dioxide and aluminum oxide anode mud and discharged from the bottom flow. This method can achieve low-cost, low-pollution, and high-efficiency comprehensive recovery of indium, gallium, and phosphorus from mixed waste. Detailed Implementation

[0029] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0030] Example 1

[0031] When processing and manufacturing indium phosphide and gallium phosphide semiconductor electronic devices, lubrication cutting is used, followed by fine grinding of the devices, resulting in oily cutting mixed waste. This mixed waste contains 10 wt% lubricating oil, 44.5 wt% silicon dioxide, 8.2 wt% aluminum oxide, 4.5 wt% indium, 0.8 wt% gallium, and 6.2 wt% phosphorus.

[0032] A method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting waste includes the following steps: S1. Take the above-mentioned oily cutting mixed waste and place it in a calcining furnace. Under air conditions, oxidize and calcine at a temperature of 400℃. After observing that the lubricating oil no longer burns during the calcination process, extend the oxidation and calcination time by 30 minutes. Calcinate for a total of 2.5 hours to ensure that all greases are completely decomposed. After cooling to room temperature, take it out and grind it to a mesh size of 60 or higher to obtain a non-oily mixed oxide containing silicon, aluminum, indium, gallium, and phosphorus. Monitor the exhaust gas generated during the calcination process. The exhaust gas of oxidation and calcination contains mainly carbon dioxide and 1.1% by volume of phosphorus vapor and H3P gas. S2. Grind the mixed oxides from step S1 into a slurry using dilute sulfuric acid. The solid-liquid ratio of the mixed oxides to dilute sulfuric acid is 1:2, resulting in a slurry mixture with a pH of 1. S3. The slurry mixture from step S2 is added to the anode region of a 1L diaphragm electrolyzer. The diaphragm of the diaphragm electrolyzer is a double-layered plastic screen with a Φ0.1mm aperture. The anode in the anode region is a graphite electrode, and the cathode in the cathode region is a stainless steel electrode. The volume ratio of the anode region to the cathode region is 3:2, and the area ratio of the anode-graphite electrode to the cathode-stainless steel electrode is 1:3. The anode current density is controlled at 300A / m. 2 At this time, the cathode current density is 100 A / m 2 The electrolytic cell voltage is 1V. The upper part of the cathode area of ​​the diaphragm electrolytic cell is provided with an electrolyte overflow port, the anode area is provided with a stirring device, and the bottom of the anode area is provided with a valve-controlled underflow outlet.

[0033] The stirring device is turned on in the anode area, the stirring speed is 200 r / min, the electrolytic leaching temperature is 30℃, and after electrolytic leaching for 1 hour, the pulping mixture is continuously added to the anode area at 5-10 mL / min for electrolytic leaching. The sulfuric acid electrolytic leaching liquid continuously overflows from the cathode area as overflow liquid. The overflow liquid is returned to step S2 for grinding and pulping treatment. At the same time, the sediment discharged from the bottom of the anode area is returned to step S2 for grinding and pulping. The flow continues until the indium and gallium content in the underflow sediment discharged from the bottom of the anode zone is less than 0.03 wt%. At this point, the valve at the underflow outlet of the anode zone is closed to stop the backflow. The underflow sediment in the anode zone is filtered, and the filtrate is returned for grinding and slurry preparation in step S2. The filter residue is sent to the rotary kiln for treatment. Simultaneously, the backflow in the cathode zone continues until the indium content in the overflow liquid is ≥500 mg / L. Then, the backflow stops, and step S3 is performed. During the electrolytic leaching process, the overflow liquid from the cathode area was tested after 2 hours of electrolytic leaching. It contained 70.5 g / L sulfuric acid, 265.4 mg / L In, 85.6 mg / L Ga, 30.3 mg / L SiO2, and 9.5 mg / L Al2O3. After 4 hours of electrolytic leaching, the overflow liquid from the cathode area was analyzed and found to contain 85.2 g / L sulfuric acid, 385.5 mg / L In, 186.3 mg / L Ga, 38.5 mg / L SiO2, and 13.2 mg / L Al2O3. After 8 hours of electrolytic leaching, the overflow liquid from the cathode area was analyzed and found to contain 105 g / L sulfuric acid, 528.6 mg / L In, 250.3 mg / L Ga, 50.8 mg / L (SiO2), and 24.7 mg / L (Al2O3). Analysis of the underflow sediment discharged from the anode area showed that it contained 47.8% (SiO2), 10.6% (Al2O3), 0.035% In, 0.023% Ga, and 0.83% P. Furthermore, it was found that metallic indium had been electrolyzed on the cathode plate, with an indium electrolytic leaching rate of 99.2% and a gallium electrolytic leaching rate of 97.1%.

[0034] S4. The sulfuric acid electrolytic leaching solution obtained from the cathode overflow in step S3 is used to extract In three times with P204 kerosene extractant to obtain an indium-containing extract and a residual extract. The residual extract contains 6.8 mg / L of In and 248.7 mg / L of Ga. The three-stage extraction rate of indium is 98.7%. The indium-containing extract is first back-extracted with hydrochloric acid, and then the back-extract is returned for back-extraction until the indium content in the back-extract reaches 32.5 g / L. Then, aluminum is used as a metal displacement agent to displace and obtain metallic indium. Then, sodium hydroxide was added to the residue to neutralize it to pH 5.2, and gallium hydroxide was formed by hydrolysis precipitation. The gallium hydroxide precipitate and filtrate were obtained by filtration. The Ga content in the filtrate was 2.3 mg / L and the hydrolysis precipitation rate was 99.1%. The gallium hydroxide precipitate was then dissolved with hydrochloric acid (the amount of hydrochloric acid added was enough to completely dissolve the gallium hydroxide, and the gallium content after dissolution was ≥1 g / L). Then, aluminum sheet was used as a metal displacement agent to displace gallium to obtain metallic gallium. The filtrate obtained after hydrolysis precipitation was neutralized to pH 7 with lime water to form calcium phosphate or superphosphate precipitate. After filtration, the filtrate was tested and found to contain 0.015 g / L of phosphorus, and the precipitation rate of superphosphate or calcium phosphate precipitate was 97.2%.

[0035] Example 2

[0036] The oily cutting waste, formed from the cleaning of quartz boats used for pulling single crystals of indium phosphide and gallium phosphide and the cutting and grinding of electronic devices containing indium phosphide and gallium phosphide, is taken as the treatment object. The mixed waste contains 5.6 wt% lubricating oil, 62.3 wt% silicon dioxide, 10.1 wt% aluminum oxide, 2.7 wt% indium, 2.1 wt% gallium, and 4.4 wt% phosphorus.

[0037] A method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting waste is carried out according to the method in Example 1, except that: In step S1, hydrogen peroxide is mixed during oxidation and calcination, and the amount of hydrogen peroxide added is 10 wt% of the oily cutting waste to be treated. The mixture is calcined at 450°C under normal pressure for 3 hours. After cooling to room temperature, it is ground to 60 mesh. The exhaust gas generated during the calcination process is monitored. The exhaust gas of oxidation and calcination contains mainly carbon dioxide and less than 0.05% phosphorus vapor and H3P gas. In step S2, the solid-liquid ratio of the mixed oxides to dilute sulfuric acid is 1:3, resulting in a pH of 2 for the slurry mixture. Step S3 involves electrolytic leaching in a diaphragm electrolytic cell according to the method described in Example 1, with an anode current density of 400 A / m. 2 The cathode current density is 150 A / m 2 The electrolytic cell voltage is 1.2V, and the anode to cathode area ratio is 3:8. After 8 hours of cyclic electrolytic leaching, the overflow liquid from the cathode area was analyzed and found to contain 121.0 g / L sulfuric acid, 585.3 mg / L In, 785.6 mg / L Ga, 80.5 mg / L SiO2, and 51.2 mg / L Al2O3. Analysis of the underflow sediment in the anode region revealed the following components: 82.5% SiO2, 16.2% Al2O3, 0.08% In, 0.12% Ga, and 0.45% P. The electrolytic leaching rates were 95.3% for indium and 94.2% for gallium. As can be seen, when the mixed waste is oxidized and calcined, it is better to calcine it in air at 450℃ after mixing with hydrogen peroxide. At the same time, the current density and cell pressure are increased, and the electrochemical leaching rates of indium, gallium and phosphorus are improved. Moreover, the tail gas after oxidation and calcination is basically free of phosphorus vapor and H3P gas.

[0038] The overflow liquid in the cathode area was operated according to the method in Example 1. The three-stage extraction rate of indium was 99.3%, the hydrolysis precipitation rate of gallium was 92.5%, and the precipitation rate of superphosphate or calcium phosphate precipitate was 97.5%.

[0039] Example 3

[0040] A method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste is disclosed. The same batch of mixed waste to be treated as in Example 2 is used as the treatment object, and the method in Example 2 is followed. The difference is that the calcination temperature in step S1 is 350°C, and the calcination is carried out under oxygen-enriched conditions with an oxygen volume content of 36%. After observing that the grease in the oily cutting mixed waste no longer burns, the oxidation calcination time is extended by 40 minutes to obtain mixed oxides. The exhaust gas generated during the calcination process is monitored. The oxidation calcination exhaust gas contains mainly carbon dioxide and 0.1% by volume of phosphorus vapor and H3P gas. The electrolytic leaching temperature in step S3 is 25°C.

[0041] In step S3, the indium electrolytic leaching rate was 94.8% and the gallium electrolytic leaching rate was 93.5%, which is lower than the electrochemical leaching rates of indium and gallium in Example 2. The overflow liquid in the cathode area was operated according to the method in Example 2. The three-stage extraction rate of indium was 99.2%, the hydrolytic precipitation rate of gallium was 96.5%, and the precipitation rate of superphosphate or calcium phosphate precipitate was 97.1%.

[0042] Example 4

[0043] A method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste is disclosed. The same batch of mixed waste to be treated as in Example 2 is used as the treatment object, and the method in Example 2 is followed. The difference is that in step S1, after the calcination time is extended until the grease in the oily cutting mixed waste no longer burns, the oxidation calcination time is not extended, and the material is directly cooled and ground. The exhaust gas generated during the calcination process is monitored. The oxidation calcination exhaust gas contains mainly carbon dioxide and 0.6% by volume of phosphorus vapor and H3P gas.

[0044] Comparative Example 1 A method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting mixed waste is disclosed. The same batch of mixed waste to be treated as in Example 2 is used as the treatment object, and the method in Example 2 is followed. The difference is that in step S3, the diaphragm electrolytic leaching operation is not performed. Instead, a bone glue flocculant is added to the slurry mixture obtained in step S2. The amount of bone glue flocculant added is 0.05 wt% of the slurry mixture. Then, the mixture is filtered, and the filtrate is subjected to the operation in step S4.

[0045] Performance testing The recovery rates of indium and gallium in the methods of the embodiments and comparative examples of this application were statistically analyzed, and the statistical results are shown in Table 1 below.

[0046] Table 1:

[0047] Referring to the statistical results in Table 1 above, the method provided in this application achieves efficient and high-recovery-rate recycling of indium and gallium. Combining the detection results in Example 1 and Comparative Example 1, for mixed waste containing silicon dioxide and aluminum oxide, as well as indium phosphide and gallium phosphide, when indium phosphide and gallium phosphide are converted to sulfate by sulfuric acid, the addition of flocculants to remove silicon dioxide and aluminum oxide will simultaneously encapsulate the target metals of indium and gallium, resulting in losses and a low yield. Moreover, some silicon dioxide and aluminum oxide will enter the slurry, affecting the subsequent extraction and separation effect, ultimately significantly reducing the yield.

[0048] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for the comprehensive recovery of indium, gallium, and phosphorus from oily cutting mixed waste, characterized in that, Includes the following steps: S1. Oxidize and calcine the oily cutting waste to obtain a non-oily mixed oxide containing silicon, aluminum, indium, gallium, and phosphorus; S2. Grind the mixed oxides from step S1 into a slurry using dilute sulfuric acid to obtain a slurry mixture. S3. The slurry mixture in step S2 is subjected to slurry membrane electrolytic leaching to obtain sulfuric acid electrolytic leaching solution containing In2(SO4)3, Ga2(SO4)3 and H3PO4 in the cathode area, indium is electrolyzed on the cathode, and anode mud deposit containing silicon dioxide and aluminum oxide is obtained in the anode area and on the anode. S4. Extract indium from the sulfuric acid electrolytic leaching solution obtained in the cathode region in step S3, and then neutralize and hydrolyze the obtained indium extraction residue to precipitate gallium. Filter to obtain gallium hydroxide precipitate and phosphorus-containing filtrate. Add lime water or calcium oxide to the filtrate to precipitate calcium phosphate or superphosphate.

2. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: Step S1 is specifically performed as follows: the oily cutting mixed waste is oxidized and calcined at a temperature of 400±50℃. After the oil in the oily cutting mixed waste no longer burns, the oxidation and calcination time is extended by 30-40 minutes to obtain mixed oxides.

3. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 2, characterized in that: In step S1, calcination is carried out under normal pressure air, oxygen-enriched air, or mixed with hydrogen peroxide. The amount of hydrogen peroxide added is 5-10% of the amount of oily cutting waste.

4. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S2, the pH of the slurry mixture is 1-2, and the solid-liquid ratio of dilute sulfuric acid to mixed oxides is 1:(2-3).

5. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S3, during the diaphragm electrolytic leaching treatment of the slurry, the electrolytic leaching temperature is 30±10℃, and the anode current density is 300-400A / m. 2 The cathode current density is 100-200 A / m 2 .

6. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S3, the slurry diaphragm electrolytic leaching method is achieved through a diaphragm electrolysis device. The cathode of the diaphragm electrolysis device is a stainless steel plate, and an electrolyte overflow port is provided at the top of the cathode area. The anode is a graphite or titanium alloy plate, and a stirring device is provided in the anode area. A bottom flow outlet controlled by a valve is provided at the bottom. During the slurry diaphragm electrolytic leaching process, the obtained slurry mixture is continuously added above the anode zone for stirring and electrolytic leaching. The sediment at the bottom of the anode zone is discharged through the underflow outlet and returned to step S2 for grinding and pulping until the indium and gallium contents in the discharged underflow sediment are both less than 0.03 wt%. The valve at the underflow outlet of the anode zone is then closed to stop the backflow. The underflow sediment in the anode zone is filtered, and the filtrate is returned for grinding and pulping in step S2. The sulfuric acid electrolytic leaching solution continuously overflows from the cathode area and returns to step S2 for grinding and pulping until the indium content of the overflowing sulfuric acid electrolytic leaching solution is ≥500mg / L. Then, the return process stops, and step S3 is performed.

7. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S4, the obtained sulfuric acid electrolytic leachate is filtered and indium is extracted with P204 kerosene extractant. Then, hydrochloric acid is used for back-extraction to obtain indium-containing hydrochloric acid back-extraction solution, which is then returned for back-extraction until indium in the indium-containing hydrochloric acid back-extraction solution is ≥10g / L. After that, it is removed and replaced with a metal displacement agent to obtain metallic indium.

8. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S4, the pH of the indium extraction residue is first adjusted to 5.2-5.4 to hydrolyze gallium and precipitate it as gallium hydroxide. After filtration, lime water or calcium oxide is added to the filtrate to continue neutralizing until the pH is 6-7, and calcium phosphate or superphosphate is precipitated.

9. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: After dissolving the gallium hydroxide precipitate in step S4 with hydrochloric acid, when the gallium content after dissolution is less than 1 g / L, it is extracted with tributyl phosphate kerosene extractant, back-extracted with ammonium sulfate solution to enrich gallium, and then gallium is replaced with a metal replacement agent to obtain metallic gallium. When the gallium content of the gallium hydroxide precipitate after dissolving it in hydrochloric acid in step S4 is ≥1g / L, gallium is directly replaced by a metal displacement agent to obtain metallic gallium.

10. The method for comprehensively recovering indium, gallium, and phosphorus from oily cutting mixed waste according to claim 1, characterized in that: In step S4, the sulfuric acid electrolytic leaching solution contains SiO2 ≤ 300 mg / L and Al2O3 ≤ 300 mg / L.

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