Method for recovering scandium and zirconium in scandia-stabilized zirconia ceramics

Abstract

The application discloses a method for recovering scandium and zirconium in scandia-stabilized zirconia ceramics, and belongs to the technical field of ceramic waste resource recovery. The method comprises the following steps: performing alkali leaching pretreatment on scandia-stabilized zirconia ceramic powder to obtain mixed slurry, introducing the mixed slurry into carbon dioxide to perform carbonation selective leaching of scandium, and performing liquid-solid separation to obtain a scandium-containing leaching solution and leaching residue; performing alkali leaching of the leaching residue to extract zirconium, and performing liquid-solid separation to obtain a zirconium-containing leaching solution and tailings. The method realizes separate leaching and extraction of scandium and zirconium in ceramics by performing carbonation after alkali leaching pretreatment to leach scandium, and leaving zirconium in the residue and extracting zirconium components through secondary alkali leaching, so that the recovery rate of scandium and zirconium can be improved, and the product purity can be improved.

Description

Technical Field

[0001] This invention relates to the field of ceramic waste resource recycling technology, and in particular to a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramics. Background Technology

[0002] Scandium-containing zirconia ceramic materials, such as scandium-stabilized zirconia ceramic materials, are widely used in ceramics, metallurgy, electronics, machinery, aerospace, and daily chemical industries. They are key raw materials for oxygen sensors, various piezoelectric ceramic components, high-temperature heating elements, and high-temperature solid-state batteries. During the production and use of ceramic materials, a large amount of scrap and defective ceramic sheets are generated. To avoid resource waste, the recovery of secondary scandium and zirconium resources from scandium-stabilized zirconia ceramics has received widespread attention.

[0003] Currently, the main method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics is the high-temperature alkali fusion method. This method involves calcination temperatures as high as 700-1200℃, resulting in high energy and alkali consumption. Scandium and zirconium undergo simultaneous acid leaching and stepwise precipitation, leading to incomplete separation of scandium and zirconium products.

[0004] Chinese invention patent CN 103950977A discloses a method for extracting zirconium oxide from zirconium-containing solid solution. The method involves mixing zirconium-containing solid solution powder and caustic soda at a mass ratio of 1:(0.8-0.95), sintering at 700-850℃ for 2.5-4 hours, followed by dilute acid leaching, hot acid leaching, crystallization of zirconium oxychloride, and finally calcination to obtain zirconium oxide. Chinese invention patent CN 102628104A discloses a production process for extracting high-purity rare earth and zirconium compounds from solid waste. The process involves reacting waste powder, calcium hydroxide, and CC additive solution at a mass ratio of 100:(70-100):(1-15) at 800-1250℃ for 1-12 hours. The calcined product is then purified by dilute hydrochloric acid, dissolved by concentrated hydrochloric acid, and concentrated under reduced pressure to obtain ZrOCl2·8H2O and a rare earth chloride solution. Finally, ZrOCl2·8H2O is washed and calcined to obtain a high-purity ZrO2 product, and the rare earth is enriched to prepare a single rare earth compound.

[0005] To avoid the high energy consumption problem of the high-temperature alkali fusion method, the low-temperature acid process is currently the most studied. However, the simultaneous leaching and step-by-step separation of scandium and zirconium still have problems, which can easily lead to the mutual entrainment of scandium and zirconium products.

[0006] Chinese invention patent CN 114262806A discloses a method for recovering scandium and zirconium from waste solid oxide fuel cells. This method involves crushing and grinding the waste scandium-zirconium oxide fuel cell into powder, digesting it with sulfuric acid at 220-300℃ for 4-5 hours, and then leaching it in water to obtain a scandium-zirconium mixed solution. Subsequently, zirconium sulfate is recovered through evaporation and crystallization, and scandium oxide is recovered through extraction, precipitation, and calcination. Chinese invention patent CN 104651619A discloses a method for separating and recovering scandium from zirconium oxide ceramic waste containing scandium and rare earth-stabilized zirconium oxide. This method involves leaching the ceramic waste powder with 10-40% hydrofluoric acid or a mixture of hydrofluoric acid and sulfuric acid to obtain a mixed leachate containing scandium and zirconium, adding potassium chloride to precipitate and crystallize potassium fluorozirconate, and then extracting, precipitating, and calcining to recover scandium oxide.

[0007] In summary, the high-temperature alkali fusion method for recovering scandium and zirconium from scandium-containing zirconium oxide ceramics generally involves calcining the ceramic with alkali at high temperature to obtain clinker, followed by acid washing, acid leaching, crystallization, and calcination to obtain the zirconium oxide product. Scandium is recovered from the crystallization mother liquor. The calcination temperature exceeds 700℃, resulting in high energy consumption. Furthermore, the alkali fusion clinker typically uses dilute hydrochloric acid to neutralize excess alkali and soluble impurities, while concentrated hydrochloric acid is used for dissolution and leaching. This acid-base neutralization process wastes acid and alkali reagents and generates large amounts of sodium chloride wastewater. Additionally, scandium and zirconium leach out simultaneously during acid leaching, leading to easy entrainment during subsequent scandium-zirconium separation, affecting product purity. While the acid process solves the problem of high energy consumption at high temperatures, the simultaneous leaching of scandium and zirconium still presents the challenge of separation.

[0008] Therefore, it is necessary to develop a scandium-zirconium recovery method to reduce energy consumption and improve scandium-zirconium recovery rate and product purity. Summary of the Invention

[0009] According to one embodiment of the present invention, the purpose is to provide a method for recovering scandium and zirconium in scandium oxide stabilized zirconia ceramics, so as to solve the problems of the existing high-temperature alkaline fusion method and the problem of simultaneous leaching of scandium and zirconium.

[0010] The above objective can be achieved through the following technical solutions: According to one aspect of the present invention, a method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics is provided, comprising: Step S1: The scandium oxide stabilized zirconia ceramic powder is subjected to alkaline leaching pretreatment to obtain a mixed slurry; Step S2: Carbon dioxide is passed through the mixed slurry to selectively leach scandium by carbonation, followed by liquid-solid separation to obtain scandium-containing leaching solution and zirconium-containing leaching residue. Step S3: Alkali leaching is performed on the leaching residue to extract zirconium, followed by liquid-solid separation to obtain zirconium-containing leaching solution and tailings.

[0011] Preferably, in step S1, the concentration of the added alkali solution is 3-12%. More preferably, it is 5%-10%.

[0012] Preferably, in step S1, the alkali leaching temperature is 60-180°C. More preferably, it is 80-120°C.

[0013] Preferably, in step S1, the molar ratio of scandium in the material to alkali in the added alkaline solution is 1:(2.5-8).

[0014] Preferably, in step S1, the added alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0015] Preferably, in step S2, the endpoint pH of the selective leaching of scandium by carbonation is 5-11. More preferably, the endpoint pH is 7.5-9.5.

[0016] Preferably, in step S2, the temperature for selective leaching of scandium by carbonation is 25-45°C.

[0017] Preferably, in step S2, the carbon dioxide gas pressure is 0.05-1.5 MPa. More preferably, it is 0.07-1.25 MPa.

[0018] Preferably, in step S3, the concentration of the added alkali solution is 10-40%. More preferably, it is 15-30%.

[0019] Preferably, in step S3, the alkaline leaching temperature is 100-260°C. More preferably, it is 120-180°C.

[0020] Preferably, in step S3, the molar ratio of zirconium in the material to alkali in the added alkaline solution is 1:(3-10).

[0021] Preferably, in step S3, the added alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0022] Preferably, the method further includes: step S4, passing carbon dioxide through the zirconium-containing immersion solution for carbonization treatment, followed by liquid-solid separation to obtain zirconium precipitate and zirconium mother liquor.

[0023] Preferably, in step S4, the carbonization endpoint pH is 10-14.

[0024] Preferably, in step S4, the carbonization temperature is 50-95℃.

[0025] Preferably, in step S4, the carbon dioxide gas pressure is 0.01-1 MPa. More preferably, it is 0.05-0.5 MPa.

[0026] Preferably, the method further includes drying, calcining, and washing the zirconium precipitate to obtain zirconium oxide.

[0027] Preferably, in the steps of drying, calcining, and washing the zirconium precipitate, the calcination temperature is 700-1200℃ and the calcination time is 2-4h.

[0028] Preferably, in the steps of drying, calcining, and washing the zirconium precipitate, the washing is a hydrothermal slurry washing. Preferably, the temperature during hydrothermal slurry washing is 100-250℃, and the washing time is 0.25-3 hours.

[0029] Preferably, the method further includes: removing impurities from the scandium-containing leaching solution, pyrolyzing it, and separating the liquid and solid phases to obtain scandium precipitate and scandium mother liquor; drying, calcining, and washing the scandium precipitate to obtain scandium oxide.

[0030] Preferably, the pyrolysis temperature is 90-120℃ and the pyrolysis time is 0.25-3h.

[0031] Preferably, in the steps of drying, calcining, and washing the scandium precipitate, the calcination temperature is 600-1100℃ and the calcination time is 2-4 hours; Preferably, in the steps of drying, calcining, and washing the scandium precipitate, the washing is a hydrothermal pulping washing at a temperature of 100-250°C.

[0032] Preferably, the method further includes: evaporating and crystallizing the mother liquor obtained after separating the precipitate to recover sodium carbonate. The mother liquor is either a zirconium precipitation mother liquor or a scandium precipitation mother liquor.

[0033] Preferably, the method further includes: reusing the steam condensate and crystallization mother liquor generated during evaporation and crystallization into the preparation of the alkali solution.

[0034] Preferably, the particle size of the powder is not greater than 150 μm.

[0035] Preferably, in the scandium oxide stabilized zirconia ceramic, the scandium oxide content is 5-15% and the zirconia content is 82-95%.

[0036] Beneficial effects: According to one embodiment of the present invention, after alkali leaching and activation of scandium oxide-stabilized zirconia ceramic powder, carbonation treatment is performed by introducing carbon dioxide, allowing scandium to be selectively leached while zirconium remains in the residue without leaching, thus achieving the separation of scandium and zirconium and realizing the extraction of the scandium component. The zirconium component is then extracted by alkali leaching of the leaching residue after scandium extraction, thereby achieving the separation of the zirconium component from impurities. The present invention achieves the separate leaching and extraction of scandium and zirconium, overcoming the problems existing in the simultaneous leaching of scandium and zirconium. Using the present invention can improve the recovery rate of scandium and zirconium, and the scandium and zirconium products obtained by the present invention have high purity. Furthermore, the alkali leaching and carbonation of the present invention can be carried out at relatively low temperatures, overcoming the high energy consumption problem of existing high-temperature alkali fusion methods. Attached Figure Description

[0037] Figure 1 This is a schematic diagram illustrating the process of recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics in this invention, enabling the separate extraction of scandium-containing and zirconium-containing leachates.

[0038] Figure 2 This is a schematic diagram of the process for recovering scandium oxide and zirconium oxide in scandium oxide-stabilized zirconium oxide ceramics according to an embodiment of the present invention. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0040] To address the problems of existing high-temperature alkaline fusion methods and simultaneous scandium-zirconium leaching, this invention pre-treats scandium oxide-stabilized zirconium oxide ceramic powder with alkaline leaching. This enhances the chemical reactivity of scandium oxide-stabilized zirconium oxide, facilitating selective leaching of scandium under suitable conditions via carbonation. Carbonation is achieved by introducing carbon dioxide into the activated material. Utilizing the principle that scandium oxide reacts with carbonate ions to form easily soluble scandium carbonate complexes, scandium is selectively leached, while zirconium does not participate in the reaction and remains in the residue, thus achieving the initial leaching extraction of the scandium component. Then, the leaching residue (containing zirconium) after scandium extraction is subjected to a second alkaline leaching, causing the zirconium component to dissolve into the liquid phase, while impurities remain in the solid phase, achieving zirconium component extraction and separation from impurities. This invention achieves separate leaching extraction of scandium and zirconium components, overcoming the difficulties in separation inherent in simultaneous scandium-zirconium leaching.

[0041] In some embodiments of the present invention, the method further includes: introducing carbon dioxide into the zirconium-containing leaching solution for carbonization treatment, followed by liquid-solid separation to obtain zirconium precipitate and zirconium mother liquor. By carbonizing the zirconium-containing leaching solution, the zirconium component can be hydrolyzed to form zirconium hydroxide precipitate, thereby further removing impurities such as sodium from the zirconium-containing leaching solution and further improving product purity.

[0042] In some embodiments of the present invention, the method further includes: removing impurities from the scandium-containing leachate obtained by selective leaching of scandium by carbonation, followed by pyrolysis and liquid-solid separation to obtain scandium precipitate and scandium mother liquor. Existing impurity removal methods can remove some leached alkali-soluble impurities from the scandium-containing leachate. After impurity removal, pyrolysis can hydrolyze the scandium carbonate complex in the aqueous solution into scandium hydroxide precipitate, further removing impurities such as sodium salts.

[0043] In some embodiments of the present invention, the method further includes drying, calcining, and washing the precipitate to obtain the oxide product. Calcination can effectively decompose the small amounts of carbonates, basic carbonates, and other mixtures contained in the zirconium / scandium precipitate, thereby further improving the purity of the product and obtaining a high-purity zirconium oxide / scandium oxide product.

[0044] In some embodiments of the present invention, such as Figure 1 As shown, a two-stage alkaline leaching and a one-stage carbonization process is adopted. By performing an alkaline leaching followed by a carbonization on the crushed and ground ceramic powder, scandium is leached out while zirconium does not participate in the reaction and remains in the residue. The zirconium component is then extracted by a second alkaline leaching of the residue after scandium extraction. This achieves the separate extraction of scandium and zirconium, resulting in scandium-containing and zirconium-containing leaching solutions, respectively. This solves the problem of difficulty in separating scandium and zirconium during simultaneous leaching in existing technologies.

[0045] In some embodiments of the present invention, reference is made to Figure 2 As shown, a two-stage alkaline leaching and two-stage carbonization process was used to separately extract scandium and zirconium from ceramics and recover their oxides, achieving the advantages of high scandium-zirconium recovery rate and high product purity. The specific steps include: (1) Scandium oxide stabilized zirconia ceramic powder is leached with alkaline solution once to obtain a mixed slurry.

[0046] Pretreatment with alkali solution can improve the chemical reactivity of the material, thus facilitating scandium extraction. Further control of the alkali solution concentration and temperature is beneficial for subsequent selective leaching of scandium via carbonation.

[0047] (2) Carbon dioxide is introduced into the mixed slurry for primary carbonization, followed by liquid-solid separation to obtain scandium-containing leaching solution and leaching residue.

[0048] The carbonation step is a carbonation leaching process for scandium extraction. It utilizes the principle that scandium oxide reacts with carbonate ions to form easily soluble scandium carbonate complexes. Under specific pH and temperature conditions, scandium can be selectively and efficiently leached, while zirconium does not participate in the reaction and remains in the residue, thus achieving effective separation of scandium and zirconium.

[0049] (3) After removing impurities from the scandium-containing leaching solution, it is subjected to pyrolysis and liquid-solid separation to obtain scandium precipitate and scandium mother liquor.

[0050] In this step, the scandium carbonate complex in the aqueous solution undergoes hydrolysis after pyrolysis, transforming into scandium hydroxide precipitate, thus completing further impurity removal. Since alkali-soluble impurities can enter the scandium leachate, it is preferable to remove impurities from the scandium-containing leachate before pyrolysis. The impurity removal method for the scandium-containing leachate can be any one of the existing chemical methods, extraction methods, or adsorption methods, preferably extraction or adsorption methods. After impurity removal, the ratio of scandium oxide to impurities in the solution meets the relevant grade requirements of "Scandium Oxide" (GB / T 13219-2018) (except for sodium oxide).

[0051] (4) The leaching residue is subjected to a second alkaline leaching with alkaline solution, and the liquid and solid are separated to obtain zirconium-containing leaching solution and tailings.

[0052] This step involves alkaline leaching of the scandium-removed residue to extract zirconium. Alkaline leaching causes zirconium oxide to dissolve into the liquid phase, while impurities that are insoluble in alkaline conditions remain in the solid phase, thus achieving the separation of zirconium components from impurities.

[0053] (5) The zirconium-containing immersion solution is passed through carbon dioxide for secondary carbonization, and liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor.

[0054] By performing secondary carbonization on the zirconium-containing immersion solution, the zirconium component is hydrolyzed to generate zirconium hydroxide, thereby further removing impurities.

[0055] (6) The scandium precipitate from step (3) and the zirconium precipitate from step (5) are dried, calcined and washed to obtain scandium oxide and zirconium oxide.

[0056] Since both scandium and zirconium precipitates contain small amounts of carbonates and basic carbonates, calcination can effectively decompose the carbonates and basic carbonates, removing impurities and recovering the product in the form of oxides with higher purity.

[0057] In some preferred embodiments, during the first alkaline leaching pretreatment in step (1), the concentration of the added alkaline solution is 3-12%, more preferably 5%-10%. The temperature of the first alkaline leaching is 60-180°C, more preferably 80-120°C.

[0058] By performing an alkaline leaching pretreatment under the specified alkaline concentration and reaction temperature conditions, the alkaline solution can better penetrate and encapsulate the scandium oxide-stabilized zirconia lattice, disrupting its structure and further enhancing its chemical reactivity, thus promoting the subsequent selective scandium extraction. Excessively high alkaline concentration and / or reaction temperature will cause a large amount of ceramic powder to dissolve, making selective scandium extraction difficult; conversely, excessively low alkaline concentration and / or reaction temperature will prevent effective disruption of the scandium oxide-stabilized zirconia lattice structure, resulting in low chemical reactivity and a reduced scandium leaching rate.

[0059] In the scandium oxide stabilized zirconia ceramic, the scandium oxide content is 5-15%, and the zirconia content is 82-95%. The alkali leaching effect can be further improved by crushing and grinding the scandium oxide stabilized zirconia ceramic sheets into powder. Preferably, the powder particle size is no greater than 150 μm. The alkali solution added in the first alkali leaching is a sodium hydroxide or potassium hydroxide solution. Furthermore, to further improve the selective leaching effect of scandium in subsequent steps, in step (1) the first alkali leaching, the molar ratio of scandium oxide in the powder to alkali in the alkali solution is preferably 1:(2.5-8), more preferably 1:(3-5). The first alkali leaching time is preferably 0.5-3 h.

[0060] In some preferred embodiments, during the selective scandium impregnation in step (2), the final pH of the primary carbonation is 5-11, more preferably 7.5-9.5. The primary carbonation reaction temperature is 25-45°C. The carbon dioxide gas pressure introduced during the primary carbonation is 0.05-1.5 MPa, more preferably 0.07-1.25 MPa.

[0061] In the selective scandium leaching step, firstly, based on the alkaline leaching pretreatment in step (1), highly reactive scandium oxide stabilized zirconia ceramic sheet powder has been obtained. Secondly, under the alkaline concentration conditions in step (1), and by controlling the carbonation endpoint pH, carbonation temperature, and carbon dioxide partial pressure conditions in step (2), the carbon dioxide reacts with the alkaline solution to generate sodium carbonate, sodium bicarbonate, carbonate, and other carbonate ions with more suitable content and composition for selective scandium extraction. Based on these conditions, selective leaching of scandium is carried out. During this process, zirconia does not participate in the reaction, thereby achieving efficient and selective extraction of scandium components from scandium oxide stabilized zirconia ceramic sheet powder. If the carbonation endpoint pH is too high, the carbonation temperature is too high, or the carbon dioxide partial pressure is too low, the leaching effect of scandium will be significantly reduced. Therefore, by using the above-mentioned pH, temperature, and gas pressure conditions, scandium can be leached more efficiently, and zirconium leaching under strong alkaline and high-temperature conditions can be avoided.

[0062] In addition, in order to further improve the selective leaching efficiency of scandium extraction, the carbonization reaction time is preferably 0.25-3h, more preferably 0.5-2h.

[0063] In some preferred embodiments, the pyrolysis temperature in step (3) is preferably 90-120°C. Furthermore, the pyrolysis time is preferably 0.25-3 h, more preferably 0.5-2 h.

[0064] Pyrolysis under the above conditions can further improve the purity of the product. However, at temperatures below or above the pyrolysis temperature, the amount of mixed sodium salt impurities in the product will increase.

[0065] In some preferred embodiments, during the secondary alkaline leaching of zirconium in step (4), the concentration of the added alkali solution is preferably 10-40%, more preferably 15-30%. Preferably, the temperature of the secondary alkaline leaching is 100-260°C, for example 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, 220°C, 240°C, 260°C, etc., more preferably 120-180°C.

[0066] By leaching zirconium at the specified alkaline concentration and / or leaching temperature, almost all zirconium oxide can dissolve into the liquid phase, while impurities insoluble in alkali remain in the solid phase, achieving more efficient separation of zirconium components from impurities. If the alkaline concentration and reaction temperature are too low during the secondary alkaline leaching, the leaching effect of zirconium oxide will be significantly reduced; if the alkaline concentration and reaction temperature are too high, energy consumption costs will increase.

[0067] The secondary alkaline leaching can be performed using a sodium hydroxide or potassium hydroxide solution. Furthermore, to further improve the zirconium extraction effect, the molar ratio of zirconium oxide in the leaching residue to alkali in the solution is preferably 1:(3-10), more preferably 1:(4-6). The secondary alkaline leaching time is preferably 1-5 hours.

[0068] In some preferred embodiments, during the secondary carbonization process in step (5), the endpoint pH of the secondary carbonization is preferably 10-14, for example, the endpoint pH is 10, 11, 12, 13, 14, etc. The secondary carbonization reaction temperature is preferably 50-95℃, for example, 50℃, 60℃, 70℃, 80℃, 90℃, etc. The pressure of the carbon dioxide gas introduced during the secondary carbonization is 0.01-1 MPa, more preferably 0.05-0.5 MPa.

[0069] By applying the specified conditions of pH / carbonization temperature / carbon dioxide partial pressure at the carbonization endpoint, the purity of zirconium hydroxide and the efficiency of zirconium component hydrolysis precipitation can be significantly improved.

[0070] In addition, in order to further improve the efficiency of secondary carbonization, the carbonization reaction time is preferably 0.25-3h, more preferably 0.5-2h.

[0071] In some preferred embodiments, during calcination in step (6), the calcination temperature of the scandium precipitate is preferably 600-1100℃, more preferably 700-900℃. The calcination temperature of the zirconium precipitate is preferably 700-1200℃, more preferably 800-1000℃. The calcination time of the scandium and zirconium precipitates is preferably 2-4 hours.

[0072] By controlling the calcination temperature and time of the precipitate, carbonates and basic carbonates can be decomposed more efficiently, further improving the impurity removal efficiency.

[0073] In some preferred embodiments, hydrothermal slurry washing is employed during step (6). Hydrothermal slurry washing can more effectively remove residual alkali metals, further improving the purity of scandium oxide and zirconium oxide. To further improve washing efficiency, preferably, the hydrothermal slurry washing temperature is 100-250℃, more preferably 130-200℃; the hydrothermal slurry washing time is 0.25-3h, more preferably 0.5-2h.

[0074] like Figure 2 As shown, in some embodiments of the present invention, based on the extraction of scandium and zirconium from ceramics through two-stage alkaline leaching and two-stage carbonization processes, high-purity scandium oxide and zirconium oxide are prepared through pyrolysis and calcination processes. Sodium carbonate is recovered through evaporation and crystallization, and the media (such as steam condensate and crystallization mother liquor) are also recycled. Specifically, the following steps are included: (1) Scandium oxide stabilized zirconia ceramic sheets with a scandium content of 5-15% are crushed and ground into ceramic sheet powder with a particle size of no more than 150μm. The ceramic sheet powder is alkali-impregnated with an alkaline solution with a concentration of 3-12% at 60-180℃ for 0.5-3h to obtain a mixed slurry. The alkaline solution is sodium hydroxide or potassium hydroxide solution, and the molar ratio of scandium oxide in the ceramic sheet powder to alkali in the alkaline solution is 1:(2.5-8). (2) Introduce carbon dioxide at a pressure of 0.05-1.5 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 25-45℃, a reaction time of 0.25-3h, and an endpoint pH of 5-11. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 90-120℃ for 0.25-3h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 100-260℃ for 1-5 hours with 10-40% alkaline solution, and the liquid and solid are separated to obtain zirconium-containing leaching solution and tailings; wherein the alkaline solution is sodium hydroxide or potassium hydroxide solution, and the molar ratio of zirconium oxide in the leaching residue to alkali in the alkaline solution is 1:(3-10). (5) Pass the zirconium-containing immersion solution from step (4) through a gas pressure of 0.01-1 MPa carbon dioxide, and perform secondary carbonization at a reaction temperature of 50-95℃, a reaction time of 0.25-3h, and an endpoint pH of 10-14. Separate the liquid and solid to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) and the zirconium precipitate from step (5) are dried, calcined for 2-4 hours, and hydrothermally washed at 100-250℃ for 0.25-3 hours to obtain scandium oxide and zirconium oxide, respectively; wherein the calcination temperature of the scandium precipitate is 600-1100℃ and the calcination temperature of the zirconium precipitate is 700-1200℃; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor for alkaline solution preparation in step (1), and reuse the steam condensate for alkaline solution preparation in step (4).

[0075] The technical solution and effects of the present invention will be described below with reference to specific embodiments and accompanying drawings: Example 1: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are: Sc2O3 6.82wt% and ZrO2 89.34wt%.

[0076] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 125 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 110°C for 1 hour with a 10% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:5 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.75 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 35℃, a reaction time of 1h, and an endpoint pH of 8.5. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 110°C for 0.75 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 150°C for 3 hours with a 20% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:5. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.05 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 90°C, a reaction time of 2 h, and an endpoint pH of 12. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 750°C for 2 hours, and washed by hydrothermal slurry at 200°C for 0.7 hours to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 900°C for 3 hours, and washed by hydrothermal slurry at 250°C for 2 hours to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0077] Example 2: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets, wherein the main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 1.

[0078] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 125 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 150°C for 0.5 h with an 8% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:2.5 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.05 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 25℃, a reaction time of 0.25h, and an endpoint pH of 9.5. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 100°C for 1 hour to separate the liquid and solid, and scandium precipitate and scandium mother liquor are obtained. (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 200°C for 2 hours with a 15% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:4. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.075 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 60°C, a reaction time of 1 h, and an endpoint pH of 11. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 900°C for 2.5 h, and then hydrothermally washed at 250°C for 2 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 1000°C for 2 h, and then hydrothermally washed at 100°C for 0.7 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0079] Example 3: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets, wherein the main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 1.

[0080] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 150 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 60°C for 2 hours with a 12% potassium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to potassium hydroxide in the potassium hydroxide solution is 1:3 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 1.5 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 45℃, a reaction time of 0.75h, and an endpoint pH of 6. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 120°C for 3 hours to separate the liquid and solid, and scandium precipitate and scandium mother liquor are obtained. (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 260°C for 4 hours with a 10% potassium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to potassium hydroxide in the potassium hydroxide solution is 1:3. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.15 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 70°C, a reaction time of 1.5 h, and an endpoint pH of 14. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 1100℃ for 2 hours, and then hydrothermally washed at 150℃ for 1 hour to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 850℃ for 3.5 hours, and then hydrothermally washed at 190℃ for 0.25 hours to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0081] Example 4: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are: Sc2O3 12.27wt% and ZrO2 83.93wt%.

[0082] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 75 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 120°C for 2 hours with a 5% potassium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to potassium hydroxide in the potassium hydroxide solution is 1:8 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.1 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 20℃, a reaction time of 3h, and an endpoint pH of 8. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution described in step (2) using existing processes, the solution is pyrolyzed at 95°C for 2 hours to separate the liquid and solid, thereby obtaining scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 180°C for 2 hours with a 30% potassium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to potassium hydroxide in the potassium hydroxide solution is 1:5. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.4 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 80°C, a reaction time of 3 h, and an endpoint pH of 13. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 850°C for 3.5 h, and washed by hydrothermal slurry at 195°C for 1.5 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 920°C for 3 h, and washed by hydrothermal slurry at 175°C for 1.5 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0083] Example 5: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 4.

[0084] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 100 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 80°C for 3 hours with a 3% potassium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to potassium hydroxide in the potassium hydroxide solution is 1:6 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 1.25 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 40℃, a reaction time of 2h, and an endpoint pH of 7.5. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 115°C for 0.5 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 120°C for 3.5 hours with a 40% potassium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to potassium hydroxide in the potassium hydroxide solution is 1:6. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.075 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 50°C, a reaction time of 0.75 h, and an endpoint pH of 12.5. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 600°C for 4 hours, and then hydrothermally washed at 100°C for 3 hours to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 870°C for 2.7 hours, and then hydrothermally washed at 140°C for 2 hours to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0085] Example 6: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 4.

[0086] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 75 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 180°C for 0.5 h with a 7.5% potassium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to potassium hydroxide in the potassium hydroxide solution is 1:3 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.07 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 25°C, a reaction time of 0.5 h, and an endpoint pH of 5. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 100°C for 0.9 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 220°C for 1 hour with a 25% potassium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to potassium hydroxide in the potassium hydroxide solution is 1:4.5. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.5 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 65°C, a reaction time of 0.25 h, and an endpoint pH of 13. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 800°C for 3.2 h, and washed by hydrothermal pulping at 140°C for 0.8 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 700°C for 3.5 h, and washed by hydrothermal pulping at 160°C for 1.75 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0087] Example 7: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are: Sc2O3 14.35wt% and ZrO2 82.68wt%.

[0088] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 60 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 100°C for 3 hours with a 6% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:4 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.15 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 45℃, a reaction time of 1.5h, and an endpoint pH of 11. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 110°C for 3 hours to separate the liquid and solid, and scandium precipitate and scandium mother liquor are obtained. (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 125°C for 4 hours with a 20% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:8. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.4 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 75°C, a reaction time of 3 h, and an endpoint pH of 11.5. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 750°C for 3.9 h, and hydrothermally washed at 190°C for 0.25 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 1000°C for 2.3 h, and hydrothermally washed at 145°C for 3 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0089] Example 8: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 7.

[0090] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 120 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 120°C for 0.75 h with an 8% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:3.5 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.25 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 30°C, a reaction time of 1 h, and an endpoint pH of 9. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 120°C for 0.25 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 100°C for 5 hours with a 15% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:10. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 1 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 65°C, a reaction time of 0.8 h, and an endpoint pH of 10. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 800°C for 3.4 h, and washed by hydrothermal slurry at 130°C for 2 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 1200°C for 2.2 h, and washed by hydrothermal slurry at 130°C for 0.75 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0091] Example 9: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 7.

[0092] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 135 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 90°C for 2 hours with a 10% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:5 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.5 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 45℃, a reaction time of 1.75h, and an endpoint pH of 7.5. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution described in step (2) according to existing processes, it is pyrolyzed at 115°C for 1 hour to separate the liquid and solid, thereby obtaining scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 160°C for 2.5 hours with a 27% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:5.5. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.01 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 95°C, a reaction time of 0.9 h, and an endpoint pH of 13. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 700°C for 3.8 h, and washed by hydrothermal pulping at 175°C for 1.75 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 800°C for 3.5 h, and washed by hydrothermal pulping at 195°C for 2 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0093] Example 10: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets. The main components and contents of the scandium oxide stabilized zirconia ceramic sheets are: Sc2O3 9.93wt% and ZrO2 85.19wt%.

[0094] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 150 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 95°C for 1.5 h with a 7.5% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:4.5 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.9 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out once with a reaction temperature of 25℃, a reaction time of 0.9 h, and an endpoint pH of 8.5. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 120°C for 1.25 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 130°C for 2 hours with a 17.5% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:5. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.25 MPa carbon dioxide, and a second carbonization is carried out at a reaction temperature of 70°C, a reaction time of 1.5 h, and an endpoint pH of 14. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 870°C for 3.5 h, and hydrothermally washed at 145°C for 2 h to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 975°C for 2.5 h, and hydrothermally washed at 200°C for 1 h to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0095] Example 11: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets, wherein the main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 10.

[0096] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 75 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 115°C for 1.5 h with a 7% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:5 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.3 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 30°C, a reaction time of 0.8 h, and an endpoint pH of 8. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 90°C for 1.75 h to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 150°C for 4.5 hours with a 15% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:6. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.4 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 55°C, a reaction time of 1.75 h, and an endpoint pH of 12.5. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 725°C for 4 hours, and then hydrothermally washed at 160°C for 0.75 hours to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 950°C for 3 hours, and then hydrothermally washed at 150°C for 0.8 hours to obtain zirconium oxide; (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0097] Example 12: This embodiment provides a method for recovering scandium and zirconium from scandium oxide stabilized zirconia ceramic sheets, wherein the main components and contents of the scandium oxide stabilized zirconia ceramic sheets are the same as those in Example 10.

[0098] The method includes the following steps: (1) Scandium oxide stabilized zirconia ceramic sheets are crushed and ground into ceramic sheet powder with a particle size of no more than 125 μm. The ceramic sheet powder is then subjected to an alkaline leaching at 100°C for 2.5 h with a 10% sodium hydroxide solution. The molar ratio of scandium oxide in the ceramic sheet powder to sodium hydroxide in the sodium hydroxide solution is 1:4 to obtain a mixed slurry. (2) Introduce carbon dioxide at a pressure of 0.7 MPa into the mixed slurry of step (1), and perform carbonization once at a reaction temperature of 40℃, a reaction time of 1 h, and an endpoint pH of 8.5. Separate the liquid and solid to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution in step (2) according to the existing process, it is pyrolyzed at 100°C for 1.5 hours to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The leaching residue from step (2) is subjected to a second alkaline leaching at 175°C for 3 hours with a 20% sodium hydroxide solution, wherein the molar ratio of zirconium oxide in the leaching residue to sodium hydroxide in the sodium hydroxide solution is 1:6. Liquid-solid separation is performed to obtain zirconium-containing leaching solution and tailings. (5) The zirconium-containing immersion solution described in step (4) is introduced into a gas pressure of 0.35 MPa carbon dioxide, and secondary carbonization is carried out at a reaction temperature of 65°C, a reaction time of 1 h, and an endpoint pH of 13. Liquid-solid separation is performed to obtain zirconium precipitate and zirconium mother liquor. (6) The scandium precipitate from step (3) is dried, calcined at 845°C for 2 hours, and washed by hydrothermal slurry at 150°C for 1 hour to obtain scandium oxide; the zirconium precipitate from step (5) is dried, calcined at 900°C for 3 hours, and washed by hydrothermal slurry at 150°C for 1 hour to obtain zirconium oxide. (7) Mix the scandium precipitation mother liquor from step (3) with the zirconium precipitation mother liquor from step (5), evaporate and crystallize to recover sodium carbonate, reuse the crystallization mother liquor to prepare alkali solution in step (1), and reuse the steam condensate to prepare alkali solution in step (4).

[0099]

[0100] As can be seen from the above embodiments, by adopting a two-stage alkaline leaching and two-stage carbonization process, not only were scandium and zirconium extracted separately, but scandium oxide and zirconium oxide products were also recovered through pyrolysis and calcination processes. The recovery rates of scandium and zirconium reached over 98.6% and 98.3%, respectively, and the purities of scandium oxide and zirconium oxide products reached over 99.9% and 98.5%, respectively.

[0101] It should be noted that the two stages of alkaline leaching and carbonization have different effects, and each step in the entire process plays its respective role. The two-stage alkaline leaching and two-stage carbonization techniques, individually or in combination, are innovative aspects of this invention. For example, by employing a single alkaline leaching and a single carbonization, and controlling pH and temperature, scandium is selectively leached while zirconium remains in the residue, achieving separation of scandium and zirconium. Further alkaline leaching of the residue after scandium extraction further separates the zirconium component from other impurities, achieving zirconium extraction. By combining two-stage alkaline leaching and two-stage carbonization with pyrolysis and calcination processes, higher purity scandium oxide and zirconium oxide products can be recovered.

[0102] The method of this invention has a low reaction temperature and belongs to a low-energy wet process, which can separate scandium and zirconium; can extract scandium and zirconium separately; and can also recover scandium oxide and zirconium oxide products separately. In addition, the process water is regenerated and reused and sodium carbonate is produced as a by-product. The process is clean and pollution-free and has broad application prospects.

[0103] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics, characterized in that, include: Step S1: The scandium oxide stabilized zirconia ceramic powder is subjected to alkaline leaching pretreatment to obtain a mixed slurry; Step S2: Carbon dioxide is passed through the mixed slurry to selectively leach scandium by carbonation, followed by liquid-solid separation to obtain scandium-containing leaching solution and zirconium-containing leaching residue. Step S3: Alkali leaching is performed on the leaching residue to extract zirconium, followed by liquid-solid separation to obtain zirconium-containing leaching solution and tailings.

2. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 1, characterized in that, In step S1, the concentration of the added alkali solution is 3-12%, preferably 5%-10%; the alkali leaching temperature is 60-180℃, preferably 80-120℃. In step S2, the endpoint pH of selective leaching of scandium by carbonation is 5-11, preferably 7.5-9.5; the temperature of selective leaching of scandium by carbonation is 25-45℃.

3. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 2, characterized in that, In step S1, the molar ratio of scandium in the material to alkali in the added alkaline solution is 1:(2.5-8); wherein the added alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution. In step S2, the carbon dioxide gas pressure is 0.05-1.5 MPa, preferably 0.07-1.25 MPa.

4. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 1, characterized in that, In step S3, the concentration of the added alkali solution is 10-40%, preferably 15-30%; the alkali leaching temperature is 100-260℃, preferably 120-180℃.

5. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 4, characterized in that, In step S3, the molar ratio of zirconium in the material to alkali in the added alkaline solution is 1:(3-10); wherein the added alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

6. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 4, characterized in that, Also includes: Step S4: Carbon dioxide is passed through the zirconium-containing immersion solution for carbonization treatment, followed by liquid-solid separation to obtain zirconium precipitate and zirconium mother liquor. The carbonization endpoint pH was 10-14; the carbonization temperature was 50-95℃.

7. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 6, characterized in that, In step S4, the carbon dioxide gas pressure is 0.01-1 MPa, preferably 0.05-0.5 MPa.

8. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 6, characterized in that, Also includes: The zirconium precipitate was dried, calcined, and washed to obtain zirconium oxide.

9. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 8, characterized in that, The calcination temperature is 700-1200℃, and the calcination time is 2-4 hours; The washing process is a hydrothermal pulping washing process, with a temperature of 100-250℃ and a washing time of 0.25-3 hours.

10. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 1, characterized in that, Also includes: The scandium-containing leaching solution is purified, pyrolyzed, and subjected to liquid-solid separation to obtain scandium precipitate and scandium mother liquor; The scandium precipitate was dried, calcined, and washed to obtain scandium oxide.

11. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 10, characterized in that, The pyrolysis temperature is 90-120℃, and the pyrolysis time is 0.25-3h; The calcination temperature is 600-1100℃, and the calcination time is 2-4 hours; The washing process is a hydrothermal pulping washing process with a temperature of 100-250℃.

12. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 6 or 10, characterized in that, Also includes: The mother liquor obtained after separating the precipitate is evaporated and crystallized to recover sodium carbonate. The steam condensate and crystallization mother liquor generated during evaporation and crystallization are reused in the preparation of alkali solution.

13. The method for recovering scandium and zirconium from scandium oxide-stabilized zirconia ceramics according to claim 1, characterized in that, The particle size of the powder is no greater than 150 μm; In the scandium oxide stabilized zirconia ceramic, the scandium oxide content is 5-15%, and the zirconia content is 82-95%.

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