Method for recovering gallium gadolinium from gadolinium gallium garnet waste

Abstract

A method for recovering gallium-gadolinium from gadolinium-gadolinium garnet waste includes the following steps: crushing and screening the gadolinium-gadolinium garnet waste to obtain gadolinium-gadolinium garnet waste particles; mixing the gadolinium-gadolinium garnet waste particles with alkali and oxidant, loading them into a crucible, and calcining them to form alkali-fused slag; after the slag cools to room temperature, immersing it along with the crucible in a container of water, peeling off all the slag from the crucible into the water for immersion, removing the crucible, and heating and stirring; after immersion in water, the alkali-fused slag is filtered and washed with water to obtain water-leached slag and water-leached liquid; the water-leached slag... Place the mixture in a container, add water and acid, heat and stir; after acid washing of the water-leached residue, filter and wash with water to obtain acid-washed residue and acid-washed solution; pour the acid-washed solution into a container, add alkaline solution to adjust the pH, filter to obtain gallium-precipitated residue and gallium-precipitated liquid; place the gallium-precipitated residue in a container, add alkali and water, heat and stir; after alkaline leaching of the gallium-precipitated residue, filter and wash with water to obtain alkaline leaching residue and alkaline leaching solution; electrolyze the water-leaching solution and alkaline leaching solution; place the gallium-precipitated liquid in a container, add alkaline solution to adjust the pH, stir and react; filter to obtain gadolinium-precipitated liquid and gadolinium hydroxide.

Description

Technical Field

[0001] This disclosure relates to the field of rare earth element and rare metal recycling, and more specifically to a method for recovering gallium gadolinium from gadolinium gallium garnet waste. Background Technology

[0002] Gallium is a rare metal, with a low content in nature. It is crucial for industrial development and is widely used in photovoltaics, magnetic materials, medical devices, wireless communications, LEDs, and other fields.

[0003] Gadolinium is a rare earth element with many uses but low quantity. It plays an important role in improving product structure, increasing technological content, and promoting technological progress in industries. It is widely used in metallurgy, military, petrochemical, glass and ceramics, agriculture and new materials.

[0004] The traditional method for gallium recovery is to leach gallium-containing materials with acid or alkali, remove impurities, and then recover gallium through electrolysis. Patent document CN105567982A discloses a method for recovering gallium from gallium nitride materials: dissolving the material with a strong alkali and an oxidant, and then obtaining metallic gallium through electrolytic deposition.

[0005] The method for recovering rare earth elements involves using a reducing agent or extractant and ion exchange resin to remove most of the iron ions from rare earth-containing materials, and then recovering the rare earth elements through precipitation. Patent document CN104603303A discloses a method for recovering rare earth elements and rare metals, which involves using a reducing agent or extractant and ion exchange resin to remove most of the iron ions, and then reacting with a precipitant to co-precipitate and recover the rare earth elements and rare metals.

[0006] Gadolinium gallium garnet is a garnet spatial configuration. Garnet structures make it difficult to separate and recover gallium and gadolinium using traditional recycling methods. The leaching and separation effects of gallium and gadolinium are poor, resulting in low recovery rates and high costs.

[0007] Therefore, there is a need to develop methods for recovering gallium gadolinium from gadolinium gallium garnet. Summary of the Invention

[0008] In view of the problems existing in the background art, one object of this disclosure is to provide a method for recovering gallium gadolinium from gadolinium gallium garnet waste, which is capable of separating and recovering gadolinium gallium from gadolinium gallium garnet waste.

[0009] Another object of this disclosure is to provide a method for recovering gallium gadolinium from gadolinium gallium garnet waste, which can recover gallium gadolinium with a high recovery rate.

[0010] Therefore, a method for recovering gallium-gadolinium from gadolinium-gadolinium garnet waste includes the following steps: S1, crushing and sieving the gadolinium-gadolinium garnet waste to obtain gadolinium-gadolinium garnet waste particles; S2, alkali fusion, mixing the gadolinium-gadolinium garnet waste particles with alkali and oxidant, loading the mixture into a crucible, and placing the crucible in a calcination device to form alkali-fused slag inside the crucible; S3, water immersion, after the alkali-fused slag cools to room temperature, immersing it along with the crucible in a container of water, peeling off all the slag from the crucible into the water in the container for water immersion, removing the crucible after peeling off the slag, and heating and stirring the container to react; S4, filtering and washing with water, after the alkali-fused slag has been water-immersed, filtering to obtain filter residue, and washing the filter residue with water as a washing liquid to obtain water-leached residue, mixing the filtrate and the washing liquid to form a water-leached solution; S5, acid washing, placing the water-leached residue into a container, adding water and acid to the container, and heating and stirring the container to react; S6 S4. After washing with filtered water and acid washing of the water-leached residue, filter to obtain filter residue and wash the filter residue with water as washing solution to obtain acid-washed residue. Mix the filtered filtrate with the washing solution to form an acid washing solution; S7. Gallium precipitation: Pour the acid washing solution into a container, add an alkaline solution to the container to adjust the pH to precipitate gallium, and filter after gallium precipitation for a certain period of time to obtain gallium precipitated residue and gallium precipitated liquid; S8. Alkaline leaching: Place the gallium precipitated residue in a container, add alkali and water to the container, and heat and stir the container to react; S9. After alkaline leaching of the gallium precipitated residue, filter to obtain filter residue and wash the filter residue with water as washing solution to obtain alkaline leaching residue. Mix the filtered filtrate with the washing solution to form an alkaline leaching solution; S10. Electrolysis: Electrolyze the water leaching solution from step S4 and the alkaline leaching solution from step S9 to recover metallic gallium; S11. Gadolinium precipitation: Place the gallium precipitated liquid in a container, add an alkaline solution to the container to adjust the pH, and stir the reaction; S12. Filter to obtain gadolinium precipitated liquid and gadolinium hydroxide.

[0011] The beneficial effects of this disclosure are as follows: through steps S1 to S12, the recovery rate of gallium can reach 95.5-97.6% (i.e., more than 95%), and the recovery rate of gadolinium can reach 95.6-98.2% (i.e., more than 95%). It can not only separate and recover gadolinium from the insoluble gadolinium gallium garnet waste, but also recover gallium and gadolinium with a high recovery rate. Attached Figure Description

[0012] Figure 1 This is a flowchart of a method for recovering gallium gadolinium from gadolinium gallium garnet waste according to this disclosure. Detailed Implementation

[0013] It will be understood that the disclosed embodiments are merely examples of this disclosure, which can be implemented in various forms. Therefore, the specific details disclosed herein should not be construed as limiting, but are intended only as the basis for the claims and as an illustrative basis to teach those skilled in the art how to implement this disclosure in various ways.

[0014] [Methods for recovering gallium gadolinium from gadolinium gallium garnet waste]

[0015] Reference Figure 1 The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to this disclosure includes the following steps:

[0016] S1, crush and screen the gadolinium gallium garnet waste to obtain gadolinium gallium garnet waste particles;

[0017] S2, Alkali fusion: After uniformly mixing gadolinium gallium garnet waste particles with alkali and oxidant, the mixture is placed into a crucible and then placed in a calcining device for calcination to form slag after alkali fusion inside the crucible.

[0018] S3, water immersion: After the slag from alkali melting has cooled to room temperature, place it together with the crucible into a container of water for immersion. Peel off all the slag from the crucible into the water in the container for immersion. After peeling off the slag, remove the crucible and heat the container to stir the reaction.

[0019] S4, after filtration and washing with water, the residue after alkali melting is soaked in water, filtered to obtain filter residue, and water is used as washing solution to wash the filter residue to obtain water-soaked residue. The filtrate and washing solution are mixed to form water-soaked solution.

[0020] S5, acid washing: put the water-leached residue into a container, add water and acid to the container, and heat and stir the container to react;

[0021] S6, after filtration and washing with water, the filter residue is filtered and washed with water as washing solution to obtain pickled residue. The filtrate and washing solution are mixed to form pickling solution.

[0022] S7, gallium precipitation: Pour the pickling solution into a container, add an alkaline solution to the container to adjust the pH to precipitate gallium, and filter after gallium precipitation for a certain period of time to obtain gallium precipitate residue and gallium precipitation liquid.

[0023] S8, alkaline leaching: Place the gallium precipitate in a container, add alkali and water to the container, and heat and stir the container to react;

[0024] S9, after washing with filtered water and alkali leaching of gallium sludge, filter to obtain filter residue and wash the filter residue with water as washing solution to obtain alkali leaching residue. Mix the filtered filtrate with the washing solution to form alkali leaching solution.

[0025] S10, Electrolysis: Electrolyze the aqueous leaching solution from step S4 and the alkaline leaching solution from step S9 to recover metallic gallium.

[0026] S11, gadolinium precipitation, after gallium precipitation, the liquid is placed in a container, an alkaline solution is added to the container to adjust the pH, and the reaction is stirred;

[0027] S12, filtered, yielding gadolinium precipitate and gadolinium hydroxide.

[0028] In the method for recovering gallium and gadolinium from gadolinium gallium garnet waste according to this disclosure, through steps S1 to S12, as verified by the subsequent testing process, the recovery rate of gallium can reach 95.5-97.6% (i.e., more than 95%), and the recovery rate of gadolinium can reach 95.6-98.2% (i.e., more than 95%). It can not only separate and recover gadolinium from the insoluble gadolinium gallium garnet waste, but also recover gallium and gadolinium with a high recovery rate.

[0029] In step S1, for example, the gadolinium gallium garnet waste is SGGG, with a Ga content of 27.83% and a Gd content of 44.99%. In one example, in step S1, the gadolinium gallium garnet waste is crushed to below 100 mesh, for example, 100 mesh and 200 mesh.

[0030] In one example, in step S2, the amount of alkali added is 2-4 times the mass of the gadolinium gallium garnet waste particles, and the amount of oxidant added is 0.2-0.6 times the mass of the gadolinium gallium garnet waste particles. In one example, in step S2, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide, and the oxidant is selected from one or more of sodium peroxide and sodium chlorate. In one example, in step S2, the calcination temperature is controlled at 500-700°C, and the calcination time is 2-8 hours. In one example, in step S2, the crucible is a nickel crucible or a graphite crucible, and the calcination equipment is a muffle furnace.

[0031] In one example, in step S3, the water soaking time is 2-8 hours, the liquid-to-solid ratio of water to gadolinium gallium garnet waste is 10-30, the water soaking temperature is controlled at 70-90°C, and the soaking time is 1-4 hours. In one example, in step S3, heating and stirring are performed using a magnetic stirrer, and the container is a beaker.

[0032] In one example, in step S5, the liquid-to-solid ratio of water to water-leached residue is 10-20, the acid concentration is controlled at 100-300 g / L, the pickling temperature is controlled at 70-90°C, and the pickling time is 1-4 hours. In another example, in step S5, the acid is selected from one or more of nitric acid, hydrochloric acid, phosphoric acid, and sulfuric acid. Further, the nitric acid, hydrochloric acid, phosphoric acid, and sulfuric acid are industrial grade, specifically 68% nitric acid, 36% hydrochloric acid, 85% phosphoric acid, and 98% sulfuric acid. In another example, in step S5, heating and stirring are performed using a magnetic stirrer, and the container is a beaker.

[0033] In one example, in step S7, the alkali in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide. In one example, in step S7, the mass fraction of the alkali used for pH is 5-50%, the pH for gallium precipitation is controlled at 5-8, and the precipitation time is controlled at 0.5-4 hours. In one example, in step S7, the container is a beaker, and stirring is performed during gallium precipitation using a magnetic stirrer.

[0034] In one example, in step S8, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide. In step S8, during alkali leaching, the alkali concentration is 10-100 g / L, the liquid-to-solid ratio of water to gallium precipitate is 6-20, the alkali leaching temperature is controlled at 60-80°C, and the leaching time is 0.5-4 h. In one example, in step S8, heating and stirring are performed using a magnetic stirrer, and the container is a beaker.

[0035] In one example, in step S10, electrolysis uses a graphite or platinum plate as the anode and a stainless steel, titanium, or platinum plate as the cathode, controlling the current density to be 10-100 A / m. 2 The aqueous leaching solution from step S4 or the alkaline leaching solution from step S8 is used as the electrolyte. The temperature of the electrolyte is 20-80°C, so that gallium is reduced and deposited at the cathode. The cathode product is washed with pure water until the pH of the attached solution is 6-8 to obtain 4N gallium.

[0036] In one example, in step S11, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide. In step S11, in one example, the mass fraction of the alkali solution is 5-50%, the pH of the solution after gallium precipitation is adjusted to above 11 to precipitate gadolinium, and the stirring time is 0.5-4 hours. In step S11, a magnetic stirrer is used for stirring, and the container is a beaker.

[0037] In addition, the pickling residue in step S6 and the alkaline leaching residue in step S9 are recovered. The pickling residue in step S6 is gadolinium oxide, and the alkaline leaching residue in step S9 is gadolinium hydroxide.

[0038] Furthermore, the water used in steps S3, S4, S5, S6, S8, and S9 can be pure water. In an alternative example, the water used in steps S3, S4, S5, S6, S8, and S9 is tap water.

[0039] [test]

[0040] Example 1

[0041] Example 1 uses the following steps:

[0042] S1, crush and screen the gadolinium gallium garnet waste to obtain gadolinium gallium garnet waste particles, wherein the gadolinium gallium garnet waste is SGGG, the Ga content is 27.83%, the Gd content is 44.99%, and the crushed gadolinium gallium garnet waste is screened through a 200-mesh sieve.

[0043] S2, Alkali fusion: 20g of gadolinium gallium garnet waste particles are mixed evenly with 40g of alkali selected from sodium hydroxide and 4g of oxidant selected from sodium peroxide (i.e., the amount of alkali added is twice the mass of gadolinium gallium garnet waste particles, and the amount of oxidant added is 0.2 times the mass of gadolinium gallium garnet waste particles). The mixture is then placed into a crucible selected from nickel crucibles. The crucible is placed in a calcination device using a muffle furnace to calcine, so that slag after alkali fusion is formed in the crucible. The calcination temperature is controlled at 600°C and the calcination time is 4h.

[0044] S3, water immersion: After the alkali-fused slag cools to room temperature, place it along with the crucible into a beaker containing 200ml of pure water for immersion for 3 hours. Then, peel all the slag off the crucible into the water in the container (i.e., the water to gadolinium gallium garnet waste liquid-solid ratio is 10) for immersion. After peeling off the slag, remove the crucible and heat and stir the container for reaction. Heating and stirring are done using a magnetic stirrer. The heating provided by the magnetic stirrer is used to control the water immersion temperature at 80°C for 2 hours.

[0045] S4. After alkali fusion and leaching, the slag is filtered to obtain filter residue, which is then washed with pure water to obtain water-leached residue. The filtrate and washing solution are mixed to form a water-leached solution. A sample of the water-leached residue is taken and the elemental content is determined by ICP spectrometry. The water-leached residue contains 3.42% Ga, 59.81% Gd, and has a gallium leaching rate of 90%.

[0046] S5, pickling: Place the water-leached residue into a beaker-shaped container, add 10 times the mass of pure water (i.e., the liquid-to-solid ratio of water to water-leached residue is 10) and 1.5 times the mass of industrial-grade 98% sulfuric acid (i.e., the acid concentration is controlled at 150 g / L). Heat and stir the container to react. Use a magnetic stirrer for heating and stirring. The heating provided by the magnetic stirrer controls the pickling temperature at 80°C, and the pickling time is 2 hours.

[0047] S6. After filtration and washing with water, the leached residue is filtered to obtain filter residue. The filter residue is then washed with pure water as the washing solution to obtain pickled residue. The filtrate and washing solution are mixed to form pickling solution. The pickled residue is sampled and the elemental content is detected by ICP spectrometer. The pickled residue contains 2.08% Ga, 40.41% Gd, and the total gallium leaching rate is 97%.

[0048] S7, Gallium precipitation: Pour the pickling solution into a beaker-shaped container, add an alkaline solution of 32% sodium hydroxide to adjust the pH to 5, and stir to precipitate gallium. After a certain precipitation time, filter to obtain gallium precipitate residue and gallium precipitation liquid. The stirring is done with a magnetic stirrer, and the gallium precipitation time is controlled at 0.5 hours. The gallium precipitation liquid is sampled and the elemental content is detected by ICP spectrometer. The gallium content in the gallium precipitation liquid is <1 ppm, and the Gd content is 7200 ppm.

[0049] S8, Alkali leaching: Place the gallium slag in a beaker-like container, add 0.1 times the mass of the gallium slag (using sodium hydroxide) and 10 times the mass of the gallium slag (using pure water) to the container (i.e., the liquid-to-solid ratio of water to gallium slag is 10, and the alkali concentration is 10 g / L). Heat and stir the container to react. Use a magnetic stirrer for heating and stirring. The heating provided by the magnetic stirrer controls the alkali leaching temperature at 60°C, and the alkali leaching time is 1 hour.

[0050] S9, after washing with filtered water and alkali leaching of gallium sludge, the filter residue is washed with pure water to obtain alkali leached residue. The filtrate and washing solution are mixed to form alkali leaching solution. The alkali leached residue is sampled and the elemental content is detected by ICP spectrometer. The alkali leached residue has a Ga content of 1200 ppm, a Gd content of 22%, and a gallium leaching rate of 98.5%.

[0051] S10, Electrolysis: The aqueous leaching solution from step S4 and the alkaline leaching solution from step S9 are electrolyzed to recover metallic gallium. A platinum plate is used as both the anode and cathode in the electrolysis, and the current density is controlled at 60 A / m. 2 The aqueous leaching solution from step S4 or the alkaline leaching solution from step S8 is used as the electrolyte. The temperature of the electrolyte is 50°C, which allows gallium to be reduced and deposited at the cathode. The cathode product is washed with pure water until the pH of the attached solution is 7 to obtain 4N gallium. The gallium loss rate is 3%. Based on the gallium leaching rate in step S9, the total gallium recovery rate after electrolysis is 95.5%.

[0052] S11, after gadolinium and gallium precipitation, the solution was placed in a beaker container, and a 32% sodium hydroxide alkaline solution was added to adjust the pH to 11.32. The reaction was stirred using a magnetic stirrer for 0.5 hours.

[0053] S12, filtration, to obtain gadolinium-precipitated liquid and gadolinium hydroxide. The gadolinium-precipitated liquid was sampled and the elemental content was detected by ICP spectrometry. The Ga content in the gadolinium-precipitated liquid was <1ppm, the Gd content was <1ppm, and the gadolinium precipitation rate was over 99%. Since most of the gallium in the gadolinium gallium garnet waste has been separated and recovered, most of the remaining waste contains gadolinium. Based on the fact that the acid washing residue in step S6 is gadolinium oxide, the alkaline leaching residue in step S9 is gadolinium hydroxide, and the gadolinium hydroxide in step S12, the gadolinium recovery rate is over 95.6%.

[0054] Example 2

[0055] Example 2 uses the following steps:

[0056] S1, crush and screen the gadolinium gallium garnet waste to obtain gadolinium gallium garnet waste particles, wherein the gadolinium gallium garnet waste is SGGG, the Ga content is 27.83%, the Gd content is 44.99%, and the crushed gadolinium gallium garnet waste is screened through a 100-mesh sieve.

[0057] S2, Alkali fusion: 20g of gadolinium gallium garnet waste particles are mixed evenly with 60g of alkali selected from potassium hydroxide and 6g of oxidant selected from sodium chlorate (i.e., the amount of alkali added is 3 times the mass of gadolinium gallium garnet waste particles, and the amount of oxidant added is 0.3 times the mass of gadolinium gallium garnet waste particles). The mixture is then placed into a crucible selected from nickel crucibles. The crucible is placed in a calcination device using a muffle furnace to calcine, so that slag after alkali fusion is formed in the crucible. The calcination temperature is controlled at 700°C and the calcination time is 3h.

[0058] S3, water immersion: After the alkali-melted slag cools to room temperature, place it along with the crucible into a beaker containing 200ml of pure water for immersion for 2 hours. Then, peel all the slag off the crucible into the water in the container (i.e., the water to gadolinium gallium garnet waste liquid-solid ratio is 10) for immersion. After peeling off the slag, remove the crucible and heat and stir the container for reaction. Heating and stirring are done using a magnetic stirrer. The heating provided by the magnetic stirrer is used to control the water immersion temperature at 90°C for 1 hour.

[0059] S4. After alkali fusion and water washing, the slag is filtered and washed with pure water to obtain water-leached residue. The filtrate and washing liquid are mixed to form a water-leached solution. The water-leached residue is sampled and its elemental content is detected by ICP spectrometry. The Ga content of the water-leached residue is 3.12%, the Gd content is 62.34%, and the gallium leaching rate is 92.6%.

[0060] S5, pickling: Place the water-leached residue into a beaker-shaped container, add 20 times the mass of pure water (i.e., the liquid-to-solid ratio of water to water-leached residue is 20) and 2 times the mass of acid selected from industrial-grade 68% nitric acid (i.e., the acid concentration is controlled at 100g / L). Heat and stir the container to react. Heating and stirring are done using a magnetic stirrer. The heating provided by the magnetic stirrer controls the pickling temperature at 70°C, and the pickling time is 2.5h.

[0061] S6. After filtration and washing with water, the leached residue is filtered to obtain filter residue. The filter residue is then washed with pure water as the washing solution to obtain pickled residue. The filtrate and washing solution are mixed to form pickling solution. The pickled residue is sampled and the elemental content is detected by ICP spectrometer. The pickled residue contains 2% Ga, 43.32% Gd, and the total gallium leaching rate is 96.5%.

[0062] S7, Gallium precipitation: Pour the pickling solution into a beaker-shaped container, add an alkaline solution of 16% potassium hydroxide to adjust the pH to 6.5, stir to precipitate gallium, and filter after a certain precipitation time to obtain gallium precipitate residue and gallium precipitation liquid. The stirring is done with a magnetic stirrer, and the gallium precipitation time is controlled at 1 hour. The gallium precipitation liquid is sampled and the elemental content is detected by ICP spectrometry. The gallium content in the gallium precipitation liquid is <1 ppm, and the Gd content is 6892 ppm.

[0063] S8, Alkali leaching: Place the gallium slag in a beaker-type container, add 0.2 times the mass of the gallium slag (using potassium hydroxide) and 8 times the mass of the gallium slag (using pure water) to the container (i.e., the liquid-to-solid ratio of water to gallium slag is 8, and the alkali concentration is 25 g / L). Heat and stir the container to react. Use a magnetic stirrer for heating and stirring. The heating provided by the magnetic stirrer controls the alkali leaching temperature at 70°C, and the alkali leaching time is 1.5 h.

[0064] S9, after washing with filtered water and alkali leaching of gallium sludge, the filter residue is washed with pure water as the washing solution to obtain alkali leached residue. The filtrate and washing solution are mixed to form alkali leaching solution. The alkali leached residue is sampled and the elemental content is detected by ICP spectrometer. The alkali leached residue has a Ga content of 1800 ppm, a Gd content of 36%, and a gallium leaching rate of 98.65%.

[0065] S10, Electrolysis: The aqueous leaching solution from step S4 and the alkaline leaching solution from step S9 are electrolyzed to recover metallic gallium. A platinum plate is used as both the anode and cathode in the electrolysis, and the current density is controlled at 60 A / m. 2 The aqueous leaching solution from step S4 or the alkaline leaching solution from step S8 is used as the electrolyte. The temperature of the electrolyte is 50°C, which allows gallium to be reduced and deposited at the cathode. The cathode product is washed with pure water until the pH of the attached solution is 7 to obtain 4N gallium. The gallium loss rate is 2%. Based on the gallium leaching rate in step S9, the total gallium recovery rate after electrolysis is 96.7%.

[0066] S11, after gadolinium and gallium precipitation, the solution was placed in a beaker container. A 16% potassium hydroxide alkaline solution was added to the container to adjust the pH to 12. The reaction was stirred using a magnetic stirrer for 1 hour.

[0067] S12, filtration, to obtain gadolinium-precipitated liquid and gadolinium hydroxide. The gadolinium-precipitated liquid was sampled and the elemental content was detected by ICP spectrometry. The Ga content in the gadolinium-precipitated liquid was <1ppm, the Gd content was <1ppm, and the gadolinium precipitation rate was over 99%. Since most of the gallium in the gadolinium gallium garnet waste has been separated and recovered, most of the gadolinium in the waste remains. Based on the fact that the acid washing residue in step S6 is gadolinium oxide, the alkaline leaching residue in step S9 is gadolinium hydroxide, and the gadolinium hydroxide in step S12, the gadolinium recovery rate reaches over 97.8%.

[0068] Example 3

[0069] Example 3 uses the following steps:

[0070] S1, crush and screen the gadolinium gallium garnet waste to obtain gadolinium gallium garnet waste particles, wherein the gadolinium gallium garnet waste is SGGG, the Ga content is 27.83%, the Gd content is 44.99%, and the crushed gadolinium gallium garnet waste is screened through a 100-mesh sieve.

[0071] S2, Alkali fusion: 20g of gadolinium gallium garnet waste particles are mixed evenly with 40g of alkali selected from calcium hydroxide and 8g of oxidant selected from sodium chlorate (i.e., the amount of alkali added is twice the mass of gadolinium gallium garnet waste particles, and the amount of oxidant added is 0.4 times the mass of gadolinium gallium garnet waste particles). The mixture is then placed into a crucible selected from nickel crucibles. The crucible is placed in a calcination device using a muffle furnace to calcine, so that slag after alkali fusion is formed in the crucible. The calcination temperature is controlled at 600°C and the calcination time is 4h.

[0072] S3, water immersion: After the slag from the alkali fusion has cooled to room temperature, it is placed together with the crucible into a beaker containing 400 ml of pure water for immersion for 3 hours. All the slag on the crucible is then peeled off into the water in the container (i.e., the water to gadolinium gallium garnet waste liquid-solid ratio is 20) for immersion. After the slag is peeled off, the crucible is removed, and the container is heated and stirred for reaction. Heating and stirring are carried out using a magnetic stirrer. The heating provided by the magnetic stirrer is used to control the water immersion temperature at 70°C for 2 hours.

[0073] S4. After alkali fusion and water washing, the slag is filtered and washed with pure water to obtain water-leached residue. The filtrate and washing liquid are mixed to form a water-leached solution. The water-leached residue is sampled and its elemental content is detected by ICP spectrometry. The Ga content of the water-leached residue is 2.96%, the Gd content is 60.21%, and the gallium leaching rate is 95.6%.

[0074] S5, pickling: Place the water-leached residue into a beaker-shaped container, add 10 times the mass of pure water (i.e., the liquid-to-solid ratio of water to water-leached residue is 10) and 2 times the mass of industrial-grade 36% hydrochloric acid (i.e., the acid concentration is controlled at 200g / L). Heat and stir the container to react. Heating and stirring are done using a magnetic stirrer. The heating provided by the magnetic stirrer is used to control the pickling temperature at 80°C, and the pickling time is 2 hours.

[0075] S6. After filtration and washing with water, the leached residue is filtered to obtain filter residue. The filter residue is then washed with pure water as the washing solution to obtain pickled residue. The filtrate and washing solution are mixed to form pickling solution. The pickled residue is sampled and its elemental content is detected by ICP spectrometer. The pickled residue contains 1.86% Ga, 39.6% Gd, and the total gallium leaching rate is 98.7%.

[0076] S7, Gallium precipitation: Pour the pickling solution into a beaker-shaped container, add an alkaline solution of 32% sodium bicarbonate to adjust the pH to 8, and stir to precipitate gallium. After a certain precipitation time, filter to obtain gallium precipitate residue and gallium precipitation liquid. The stirring is done with a magnetic stirrer, and the gallium precipitation time is controlled at 1.5 hours. The gallium precipitation liquid is sampled and the elemental content is detected by ICP spectrometry. The gallium content in the gallium precipitation liquid is <1 ppm, and the Gd content is 6980 ppm.

[0077] S8, Alkali leaching: Place the gallium slag in a beaker-type container, add 0.2 times the mass of the gallium slag (alkaline selected from potassium hydroxide) and 10 times the mass of the gallium slag (pure water) to the container (i.e., the liquid-to-solid ratio of water to gallium slag is 10, and the alkali concentration is 20 g / L). Heat and stir the container to react. Heating and stirring are done using a magnetic stirrer. The heating provided by the magnetic stirrer controls the alkali leaching temperature at 70°C, and the alkali leaching time is 1 hour.

[0078] S9. After washing with filtered water and alkali leaching of gallium slag, the filter residue is obtained and washed with pure water as the washing solution to obtain alkali leached residue. The filtrate and washing solution are mixed to form alkali leaching solution. The alkali leached residue is sampled and the elemental content is detected by ICP spectrometer. The alkali leached residue has a Ga content of 1102 ppm, a Gd content of 21.36%, and a gallium leaching rate of 99.32%.

[0079] S10, Electrolysis: The aqueous leaching solution from step S4 and the alkaline leaching solution from step S9 are electrolyzed to recover metallic gallium. A platinum plate is used as both the anode and cathode in the electrolysis, and the current density is controlled at 60 A / m. 2The aqueous leaching solution from step S4 or the alkaline leaching solution from step S8 is used as the electrolyte. The temperature of the electrolyte is 50°C, and gallium is reduced and deposited at the cathode. The cathode product is washed with pure water until the pH of the attached solution is 7 to obtain 4N gallium. The gallium loss rate is 1.7%. Based on the gallium leaching rate in step S9, the total gallium recovery rate after electrolysis is 97.6%.

[0080] S11, after gadolinium and gallium precipitation, the solution was placed in a beaker container. A 16% sodium bicarbonate alkaline solution was added to the container to adjust the pH to 12. The reaction was stirred using a magnetic stirrer for 1.5 hours.

[0081] S12, filtration, yielding gadolinium-precipitated liquid and gadolinium hydroxide. The gadolinium-precipitated liquid was sampled and its elemental content was detected by ICP spectrometry. The Ga content in the gadolinium-precipitated liquid was <1ppm, the Gd content was <1ppm, and the gadolinium precipitation rate was over 99%. Since most of the gallium in the gadolinium gallium garnet waste has been separated and recovered, and most of the remaining waste contains gadolinium, based on the fact that the acid washing residue in step S6 is gadolinium oxide, the alkaline leaching residue in step S9 is gadolinium hydroxide, and the gadolinium hydroxide in step S12, the gadolinium recovery rate is over 99.82%.

[0082] Several exemplary embodiments have been described in detail above, but this document is not intended to limit itself to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined to form several other combinations, which are not shown for simplicity.

Claims

1. A method for recovering gallium gadolinium from gadolinium gallium garnet waste, characterized in that, Including the following steps: S1, crush and screen the gadolinium gallium garnet waste to obtain gadolinium gallium garnet waste particles; S2, Alkali fusion: Gadolinium gallium garnet waste particles are mixed evenly with alkali and oxidant and then placed into a crucible. The crucible is placed in a calcining device for calcination to form slag after alkali fusion. The alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide. The oxidant is selected from one or more of sodium peroxide and sodium chlorate. The calcination temperature is controlled at 500-700°C. S3, water immersion: After the slag from alkali melting has cooled to room temperature, place it together with the crucible into a container of water for immersion. Peel off all the slag from the crucible into the water in the container for immersion. After peeling off the slag, remove the crucible and heat the container to stir the reaction. S4, after filtration and washing with water, the residue after alkali melting is soaked in water, filtered to obtain filter residue, and water is used as washing solution to wash the filter residue to obtain water-soaked residue. The filtrate and washing solution are mixed to form water-soaked solution. S5, acid washing: put the water-leached residue into a container, add water and acid to the container, and heat and stir the container to react; S6, after filtration and washing with water, the filter residue is filtered and washed with water as washing solution to obtain pickled residue. The filtrate and washing solution are mixed to form pickling solution. S7, gallium precipitation: Pour the pickling solution into a container, add an alkaline solution to the container to adjust the pH to precipitate gallium. The pH of gallium precipitation is controlled at 5-8. After gallium precipitation for a certain period of time, filter to obtain gallium precipitate residue and gallium precipitation liquid. S8, alkaline leaching: Place the gallium precipitate in a container, add alkali and water to the container, and heat and stir the container to react; S9, after washing with filtered water and alkali leaching of gallium sludge, filter to obtain filter residue and wash the filter residue with water as washing solution to obtain alkali leaching residue. Mix the filtered filtrate with the washing solution to form alkali leaching solution. S10, Electrolysis: Electrolyze the aqueous leaching solution from step S4 and the alkaline leaching solution from step S9 to recover metallic gallium. S11, gadolinium precipitation, after gallium precipitation, place the solution in a container, add alkaline solution to the container to adjust the pH, adjust the pH of the solution after gallium precipitation to above 11 to precipitate gadolinium, and stir the reaction; S12, filtered, yielding gadolinium precipitate and gadolinium hydroxide.

2. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S1, the gadolinium gallium garnet waste is SGGG, with a Ga content of 27.83% and a Gd content of 44.99%.

3. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S2, The amount of alkali added is 2-4 times the mass of the gadolinium gallium garnet waste particles. The amount of oxidant added is 0.2-0.6 times the mass of the gadolinium gallium garnet waste particles; The calcination time is 2-8 hours.

4. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S3, the water soaking time is 2-8 hours. During water soaking, the liquid-solid ratio of water to gadolinium gallium garnet waste is 10-30. The water soaking temperature is controlled at 70-90°C, and the water soaking time is 1-4 hours.

5. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S5, The liquid-to-solid ratio of water to water-leached residue is 10-20, the acid concentration is controlled at 100-300 g / L, the pickling temperature is controlled at 70-90°C, and the pickling time is 1-4 h. The acid is selected from one or more of nitric acid, hydrochloric acid, phosphoric acid, and sulfuric acid.

6. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 5, characterized in that, Nitric acid, hydrochloric acid, phosphoric acid, and sulfuric acid are industrial grade.

7. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S7, The base in the alkaline solution is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide; The alkali mass fraction used for pH is 5-50%, and the gallium precipitation time is controlled between 0.5-4 hours.

8. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S8, The alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide; During alkaline leaching, the alkaline concentration is 10-100 g / L, the liquid-to-solid ratio of water to gallium precipitate is 6-20, the alkaline leaching temperature is controlled at 60-80°C, and the alkaline leaching time is 0.5-4 h.

9. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S10, Electrolysis uses graphite or platinum plates as the anode and stainless steel, titanium, or platinum plates as the cathode. Control current density to 10-100 A / m 2 The aqueous leaching solution from step S4 or the alkaline leaching solution from step S8 is used as the electrolyte. The temperature is 20-80°C, and gallium is reduced and deposited at the cathode. The cathode product is washed with pure water until the pH of the attached solution is 6-8 to obtain 4N gallium.

10. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, In step S11, The alkali is selected from one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and calcium hydroxide; The alkaline solution has a mass fraction of 5-50%, and the stirring time is 0.5-4 hours.

11. The method for recovering gallium gadolinium from gadolinium gallium garnet waste according to claim 1, characterized in that, The pickling residue in step S6 and the alkaline leaching residue in step S9 are recovered. The pickling residue in step S6 is gadolinium oxide, and the alkaline leaching residue in step S9 is gadolinium hydroxide.

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