Process for the treatment of scandium-containing materials by alkaline leaching and carbonization

Abstract

This invention discloses an alkaline leaching and carbonization treatment method for scandium-containing materials, belonging to the technical field of wet processing of scandium-containing materials. The method includes: alkali leaching the scandium-containing material to obtain a mixed slurry; passing carbon dioxide through the mixed slurry for selective scandium leaching via carbonation; and performing liquid-solid separation to obtain a scandium-containing leaching solution and a leaching residue. This invention, through alkaline leaching followed by carbonization, selectively leaches scandium from the scandium-containing material, while zirconium and components with similar properties, as well as other impurities, remain in the residue without leaching. Based on the scandium-containing leaching solution obtained after liquid-solid separation, scandium recovery rate and purity can be improved.

Description

Technical Field

[0001] This invention relates to the field of wet treatment of scandium-containing materials, and in particular to an alkaline leaching and carbonization treatment method for scandium-containing materials. Background Technology

[0002] Scandium extraction is the process of separating scandium from impurities in scandium-containing materials and recovering scandium oxide products. Scandium-containing materials typically contain elements such as zirconium, titanium, and hafnium.

[0003] Some relevant literature describes the use of a high-temperature alkali fusion method to recover scandium. The general process involves first adding alkali and calcining at high temperature to obtain clinker. The clinker is then acid-washed to neutralize the alkali and soluble impurities, dissolved and leached with concentrated hydrochloric acid, crystallized, and scandium is recovered from the mother liquor. This high-temperature alkali fusion method involves calcination temperatures as high as 700-1200℃, resulting in high energy consumption and large quantities of acid and alkali reagents. Furthermore, the simultaneous leaching of scandium and zirconium during acid leaching leads to incomplete subsequent separation and easy entrainment, affecting product purity.

[0004] In some related literature, a low-temperature acid process has been adopted to address the high energy consumption problem of the high-temperature alkali leaching method. For example, Chinese invention patent CN 104651619A discloses a method for separating and recovering scandium. This method involves leaching the raw material powder with 10-40% hydrofluoric acid or a mixture of hydrofluoric acid and sulfuric acid to obtain a mixed leachate containing scandium and zirconium. Potassium chloride is then added to precipitate and crystallize potassium fluorozirconate, and an extraction, precipitation, and calcination process is used to recover scandium oxide. Although this method reduces the processing temperature and solves the high energy consumption problem, it still suffers from the problem of simultaneous leaching of scandium with other elements, and the separation process is prone to product entrainment, affecting the purity of the final product.

[0005] Therefore, there is an urgent need to develop a process for extracting scandium from scandium-containing materials in order to reduce energy consumption and improve scandium recovery rate and product purity. Summary of the Invention

[0006] According to one embodiment of the present invention, the purpose is to provide an alkaline leaching and carbonization treatment method for scandium-containing materials, so as to solve the problems of low scandium recovery rate and product purity, and high energy consumption in the prior art.

[0007] The above objective can be achieved through the following technical solutions: According to one aspect of the present invention, an alkaline leaching carbonization treatment method for scandium-containing materials is provided, comprising: Step S1: Alkali leaching is performed on the scandium-containing material to obtain a mixed slurry; Step S2: Carbon dioxide is passed through the mixed slurry to perform carbonation selective scandium impregnation, followed by liquid-solid separation to obtain scandium-containing impregnation solution and impregnation residue.

[0008] Preferably, in step S1, the concentration of the alkali solution added for the alkali leaching treatment is 3-12%. More preferably, the concentration of the alkali solution added for the alkali leaching treatment is 5%-10%.

[0009] Preferably, in step S1, the alkaline leaching temperature is 60-180°C. More preferably, the alkaline leaching temperature is 80-120°C.

[0010] Preferably, in step S1, during the alkali leaching treatment, the molar ratio of scandium in the scandium-containing material to alkali in the alkali solution is 1:(2.5-8).

[0011] Preferably, in step S1, the alkaline solution added during the alkaline leaching treatment is a sodium hydroxide solution or a potassium hydroxide solution.

[0012] Preferably, before step S1, the method further includes: crushing and grinding the scandium-containing material to obtain scandium-containing material with a particle size of no more than 150 μm.

[0013] Preferably, in step S2, the final pH of the selective scandium immersion in carbonation is 5-11. More preferably, the final pH of the selective scandium immersion in carbonation is 7.5-9.5.

[0014] Preferably, in step S2, the temperature is 25-45℃.

[0015] Preferably, in step S2, the pressure of the introduced carbon dioxide gas is 0.05-1.5 MPa. More preferably, the pressure of the introduced carbon dioxide gas is 0.07-1.25 MPa.

[0016] Preferably, the alkaline leaching and carbonization treatment method for the scandium-containing material further includes: step S3, removing impurities from the scandium-containing leaching solution and then subjecting it to pyrolysis and liquid-solid separation to obtain scandium precipitate and scandium mother liquor.

[0017] Preferably, in step S3, the pyrolysis temperature is 90-120℃ and the pyrolysis time is 0.25-3h.

[0018] Preferably, the alkaline leaching and carbonization treatment method for the scandium-containing material further includes: step S4, drying, calcining, and washing the scandium precipitate to obtain scandium oxide.

[0019] Preferably, in step S4, the calcination temperature is 600-1100℃ and the calcination time is 2-4h.

[0020] Preferably, in step S4, the washing is a hydrothermal pulping washing process.

[0021] Preferably, the hydrothermal pulping washing temperature is 100-250℃.

[0022] Preferably, the alkaline leaching and carbonization treatment method for scandium-containing materials further includes: step S5, evaporating and crystallizing the scandium precipitation mother liquor to recover sodium carbonate; and reusing the generated steam condensate and crystallization mother liquor to prepare the alkaline solution used in step S1 alkaline leaching treatment.

[0023] Preferably, the scandium content in the scandium-containing material is 1-95%.

[0024] Preferably, the other elements in the scandium-containing material include one or more of zirconium, hafnium, and titanium.

[0025] Preferably, the scandium-containing material is a solid oxide fuel cell.

[0026] Preferably, the scandium oxide content is 5-15%.

[0027] Beneficial effects: According to one embodiment of the present invention, by subjecting scandium-containing materials to alkaline leaching, the alkaline solution enters and coats the crystal lattice, disrupting the crystal structure of the scandium-containing materials and increasing their chemical reactivity, thus promoting the selective extraction of scandium in the next step. By introducing carbon dioxide into the mixed slurry for carbonation treatment, scandium oxide reacts with carbonate ions to form easily soluble scandium carbonate complexes, enabling selective leaching of scandium. Elements such as zirconium do not participate in the reaction and remain in the residue without leaching. A scandium-containing leaching solution is obtained through liquid-solid separation. Subsequent scandium recovery based on this solution can improve the scandium recovery rate and product purity. Furthermore, both alkaline leaching and selective carbonation leaching of scandium can be carried out at relatively low temperatures, thereby overcoming the high energy consumption problem of the high-temperature alkaline fusion method. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process for obtaining scandium-containing leaching solution by alkaline leaching and carbonization treatment of scandium-containing materials in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the process of obtaining scandium-containing leaching solution and recovering scandium to obtain scandium oxide by alkaline leaching and carbonization treatment of scandium-containing materials in an embodiment of the present invention. Detailed Implementation

[0030] 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.

[0031] To address the issues of low scandium recovery rate and low purity in scandium-containing materials, this invention involves alkaline leaching and carbonization of scandium-containing materials under specific pH and temperature conditions. This allows for the selective leaching of scandium, while elements such as zirconium and similar elements like hafnium-titanium, as well as other impurities, remain in the residue without leaching. A scandium-containing leachate is obtained through liquid-solid separation. Subsequent scandium recovery based on this leachate can improve the scandium recovery rate and product purity.

[0032] like Figure 1 As shown, the alkaline leaching and carbonization treatment method for scandium-containing materials provided in some embodiments of the present invention includes: (1) Add alkali solution to scandium-containing materials for alkali leaching to obtain mixed slurry.

[0033] Furthermore, the concentration of the alkaline solution is 3-12%, more preferably 5%-10%. The temperature of the alkaline leaching is 60-180℃, more preferably 80-120℃.

[0034] Alkali leaching under the specified alkali concentration and reaction temperature conditions promotes the alkali solution to enter and encapsulate the crystal lattice, disrupting the crystal structure of the scandium-containing material, increasing its chemical reactivity, and facilitating selective leaching of scandium via carbonation under suitable conditions. Excessively high alkali concentration and / or reaction temperature will lead to significant powder dissolution, making subsequent selective scandium extraction difficult; conversely, excessively low alkali concentration and / or reaction temperature will result in ineffective disruption of the crystal lattice structure, low chemical reactivity, and reduced scandium leaching rate.

[0035] Furthermore, to further improve the alkaline leaching activation effect and more efficiently carry out subsequent selective leaching of scandium via carbonation, in step S1, the molar ratio of scandium in the scandium-containing material to alkali in the alkaline solution is preferably 1:(2.5-8). The alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

[0036] (2) Carbon dioxide is introduced into the mixed slurry for carbonization, and after liquid-solid separation, scandium-containing leaching solution and zirconium-containing leaching residue are obtained.

[0037] By introducing carbon dioxide into the activated scandium-containing material and carbonating it under specific pH and temperature conditions, scandium is selectively leached by utilizing the principle that scandium oxide reacts with carbonate to form a readily soluble scandium carbonate complex. Other elements such as zirconium, hafnium titanium, and other impurities do not participate in the reaction and remain in the residue without leaching. This achieves efficient scandium leaching and separation of scandium from other elements.

[0038] Furthermore, the endpoint pH of carbonization is 5-11, more preferably 7.5-9.5. The carbonization reaction temperature is preferably 25-45°C. The pressure of the carbon dioxide gas introduced during carbonization is 0.05-1.5 MPa, more preferably 0.07-1.25 MPa.

[0039] The selective leaching process for scandium extraction via carbonation involves several steps. First, based on the highly reactive scandium-containing material obtained through alkaline leaching in step (1), the process proceeds under the alkaline concentration conditions of step (1). Then, by further 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 a system of sodium carbonate, sodium bicarbonate, and carbonic acid, which are more suitable for selective scandium extraction. Based on this system, selective leaching of scandium is carried out. During this process, zirconium and similar elements such as hafnium and titanium do not participate in the reaction and remain in the residue. Other impurities also remain in the residue, thereby achieving selective extraction of scandium components from the scandium-containing material. Excessively high carbonation endpoint pH, excessively high carbonation temperature, and excessively low carbon dioxide partial pressure will significantly reduce the leaching effect of scandium. Therefore, by applying the specific pH, temperature, and gas pressure conditions mentioned above, scandium can be leached more efficiently, while avoiding the leaching of elements such as zirconium under strong alkaline and high-temperature conditions.

[0040] In some embodiments of the present invention, during scandium recovery, based on the scandium-containing leaching solution obtained from alkaline leaching and carbonization, a pyrolysis-calcination process is used to recover scandium, resulting in a high-purity scandium oxide product. Specifically, this includes: (3) Remove impurities from the scandium-containing leaching solution, pyrolyze it, and separate the liquid and solid to obtain scandium precipitate and scandium mother liquor.

[0041] During the selective leaching of scandium using alkali leaching and carbonation, alkali-soluble impurities enter the scandium leaching solution. In step (3), these alkali-soluble impurities are removed by purifying the scandium-containing leaching solution before pyrolysis. The purification method for the scandium-containing leaching solution is an existing process, which can be any one of chemical method, extraction method, or adsorption method, preferably extraction method or adsorption method. After purification, 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). After purification, the scandium-containing leaching solution is pyrolyzed. The scandium carbonate complex in the aqueous solution undergoes hydrolysis through pyrolysis and is converted into scandium hydroxide precipitate, thereby completing further purification and removing impurities such as sodium salt.

[0042] To further improve the efficiency of thermal depurification, preferably, in step (3), the pyrolysis temperature is 90-120℃. At temperatures below or above this pyrolysis temperature, the amount of mixed sodium salt impurities in the product will increase. In addition, the pyrolysis time is preferably 0.25-3h.

[0043] (4) The scandium precipitate is dried, calcined, and washed to obtain scandium oxide.

[0044] Since scandium oxide precipitate also contains a small amount of carbonates, basic carbonates and other mixtures, in step (4), calcination can effectively decompose carbonates and basic carbonates, thereby removing impurities.

[0045] In order to decompose carbonates, basic carbonates, etc. more efficiently, and to further control the calcination temperature and time of the precipitate, preferably, the calcination temperature is 600-1100℃ and the calcination time is 2-4h.

[0046] To more effectively remove residual alkali metals after calcination, a hydrothermal slurry washing method is preferably employed. More preferably, the hydrothermal slurry washing temperature is 100-250℃, more preferably 130-200℃. The hydrothermal slurry washing time is preferably 0.25-3 hours, more preferably 0.5-2 hours.

[0047] Scandium oxide was obtained by recovering scandium using a pyrolysis-calcination process based on the scandium-containing leachate, which improved the scandium recovery rate and the purity of the scandium oxide product.

[0048] In some optional embodiments, zirconium can also be recovered from the leaching residue after scandium extraction. The zirconium recovery method is not limited. More preferably, an alkaline leaching and carbonization process is used to obtain zirconium precipitate. The zirconium precipitate can also be dried, calcined, and washed to obtain zirconium oxide. This includes the following steps: (1) Add alkaline solution to the leaching residue after scandium extraction for alkaline leaching, and separate the liquid and solid to obtain zirconium-containing leaching solution and tailings.

[0049] By using specific alkaline solution concentrations and reaction temperatures, zirconium oxide is almost completely dissolved into the liquid phase, while insoluble impurities remain in the solid phase, thus separating the zirconium component from the impurities. The alkaline solution concentration is 10-40%, more preferably 15-30%. The alkaline leaching temperature is 100-260℃, more preferably 120-180℃. Too low an alkaline solution concentration or too low a reaction temperature will significantly reduce the zirconium oxide leaching effect, while too high an alkaline solution concentration or too high a reaction temperature will increase energy consumption costs. Furthermore, to further improve the zirconium extraction effect, the molar ratio of zirconium oxide in the leaching residue to alkali in the alkaline solution is 1:(3-10). The alkaline leaching time is 1-5 hours. The alkaline solution is preferably a sodium hydroxide or potassium hydroxide solution.

[0050] (2) Carbon dioxide is passed through the zirconium-containing immersion solution for carbonization, and liquid-solid separation is performed to obtain zirconium precipitate.

[0051] Carbonization hydrolyzes the zirconium component to form zirconium hydroxide. Under specific conditions, including the endpoint pH, carbonization temperature, and carbon dioxide partial pressure, zirconium hydroxide can be effectively obtained. Deviating from these conditions will significantly reduce the purity of the zirconium hydroxide or the hydrolysis precipitation efficiency. Specifically, the endpoint pH is 10-14. The carbon dioxide gas pressure is 0.01-1 MPa, more preferably 0.05-0.5 MPa. The carbonization reaction temperature is 50-95°C.

[0052] (3) The zirconium precipitate is dried, calcined, and hydrothermally washed to obtain zirconium oxide product.

[0053] A mixture of small amounts of carbonates and basic carbonates is removed through calcination and hydrothermal slurry washing, effectively removing residual alkali metals. The calcination temperature is 700-1200℃, and the time is 2-4 hours. The hydrothermal slurry washing temperature is 100-250℃, and the time is 0.25-3 hours.

[0054] like Figure 2 As shown in some embodiments of the present invention, the alkaline leaching and carbonization treatment method for scandium-containing materials first crushes and grinds the scandium-containing material, then activates it by alkaline leaching with alkaline solution, followed by selective leaching of scandium by carbonation, and finally obtains high-purity scandium oxide product through impurity removal, pyrolysis, drying, calcination and washing. Sodium carbonate is obtained by evaporating and crystallizing the scandium precipitation mother liquor, and the reuse of the medium is also realized.

[0055] Specifically, the following steps are included: (1) The scandium-containing material is crushed and ground to obtain a scandium-containing material with a particle size of no more than 150 μm. An alkaline solution with a concentration of 3-12% is added to the crushed and ground scandium-containing material, and the material is alkali-soaked at 60-180℃ for 0.5-3 hours to obtain a mixed slurry.

[0056] The scandium-containing material contains 1-95% scandium oxide; other elements include one or more of zirconium, hafnium, and titanium. Further, scandium extraction can be performed on scandium-containing materials produced in the field of solid oxide fuel cells, wherein the scandium oxide content is 5-15%. The alkaline solution is a sodium hydroxide or potassium hydroxide solution, and the molar ratio of scandium oxide in the scandium-containing material to alkali in the alkaline solution is 1:(2.5-8).

[0057] (2) Carbon dioxide with a gas pressure of 0.05-1.5 MPa is introduced into the mixed slurry, and carbonization is carried out at a reaction temperature of 25-45℃, a reaction time of 0.25-3h, and an endpoint pH of 5-11. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue containing elements such as zirconium.

[0058] (3) After removing impurities from the scandium-containing leaching solution using existing processes, it is pyrolyzed at 90-120℃ for 0.25-3h to separate the liquid and solid, thereby obtaining scandium precipitate and scandium mother liquor; (4) The scandium precipitate is dried, calcined at 600-1100℃ for 2-4 hours, and washed by hydrothermal slurry washing at 100-250℃ for 0.25-3 hours to obtain scandium oxide.

[0059] (5) Evaporate and crystallize the scandium precipitation mother liquor from step (3) to recover sodium carbonate. The steam condensate and crystallization mother liquor generated during evaporation and crystallization are then reused to prepare the alkaline solution in step S1.

[0060] By inducing the alkali solution to enter and encapsulate the scandium oxide-stabilized zirconia lattice under the conditions of alkali concentration and reaction temperature, the lattice structure of the scandium-containing material is destroyed, thereby increasing its chemical reactivity and promoting the effect of selective scandium extraction in the next step. In addition, the effect of alkali leaching and carbonation leaching can be further improved by crushing.

[0061] Scandium is extracted by selective leaching using carbonation, based on the principle that scandium oxide reacts with carbonate to form a readily soluble scandium carbonate complex. Furthermore, the process involves: based on the obtained highly reactive scandium-containing powder material, and under the conditions of alkali concentration after alkali leaching, as well as the conditions of pH at the carbonation endpoint, carbonation temperature, and partial pressure of carbon dioxide, a system of sodium carbonate, sodium bicarbonate, and carbonic acid, which is more suitable for selective scandium extraction, is generated by the reaction of carbon dioxide with alkali. Under these conditions of carbonate, bicarbonate, and carbonic acid content and composition, efficient carbon dioxide extraction by carbonation is carried out, allowing the scandium component in the scandium-containing powder material to be extracted, while zirconium and other elements do not participate in the reaction (avoiding the simultaneous leaching of zirconium and other elements under strong alkali and high temperature), thus achieving effective separation of scandium from other elements and overcoming the problem of product cross-contamination caused by simultaneous leaching in existing technologies. Moreover, the above-mentioned alkali leaching and carbonation extraction processes are both carried out at relatively low temperatures (alkali leaching not exceeding 180℃, and carbonation extraction not exceeding 45℃), thereby also overcoming the high energy consumption problem of the high-temperature alkali fusion method.

[0062] Based on the scandium-containing leaching solution obtained through alkaline leaching and carbonization, a pyrolysis-calcination process was used to recover scandium. Further optimization of process parameters further improved the recovery rate and purity of scandium oxide. Specifically, the scandium recovery rate was ≥98%, such as 98%, 99%, or 99.5%. The purity of the scandium oxide product was ≥99%.

[0063] 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 alkaline leaching and carbonization treatment of scandium-containing materials, and recovers scandium to obtain scandium oxide product. The scandium-containing material has an Sc2O3 content of 11 wt% and a total impurity content of 5% for zirconium, hafnium, and titanium.

[0064] The processing method includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 125 μm. The powder is then alkali-leached with a 10% sodium hydroxide solution at 100°C for 2.5 h. The molar ratio of scandium oxide in the powder to sodium hydroxide in the sodium hydroxide solution is 1:4, resulting in a mixed slurry.

[0065] (2) Carbon dioxide gas with a pressure of 0.7 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out at a reaction temperature of 40℃, 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.

[0066] (3) After removing impurities from the scandium-containing leaching solution in step (2) using existing processes, pyrolyze it at 100°C for 1.5 hours to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor.

[0067] (4) The scandium precipitate from step (3) is dried, calcined at 845°C for 2 hours, and washed with hydrothermal pulping at 150°C for 1 hour to obtain scandium oxide.

[0068] (5) After evaporating and crystallizing the scandium precipitation mother liquor from step (3), sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution in step (1).

[0069] Calculation results: Scandium recovery rate 99.29%, scandium oxide purity 99.95%.

[0070] Example 2

[0071] This embodiment provides a method for alkaline leaching and carbonization treatment of scandium-containing materials, and recovers scandium to obtain scandium oxide product. The scandium-containing material contains 1.2 wt% Sc2O3 and 3% total zirconium and titanium impurities.

[0072] The processing method includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 125 μm. The powder is then alkali-leached with an 8% sodium hydroxide solution at 150°C for 0.5 h. The molar ratio of scandium oxide in the scandium-containing material to sodium hydroxide in the sodium hydroxide solution is 1:2.5, resulting in a mixed slurry.

[0073] (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 at 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 scandium precipitate was dried, calcined at 900℃ for 2.5h, and washed with hydrothermal pulping at 250℃ for 2h to obtain scandium oxide; (5) After evaporating and crystallizing the scandium precipitation mother liquor, sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution.

[0074] Calculation results: Scandium recovery rate 99.22%, scandium oxide purity 99.98%.

[0075] Example 3

[0076] This embodiment provides a method for alkaline leaching and carbonization treatment of scandium-containing materials, and recovers scandium to obtain scandium oxide product. The scandium-containing material contains 48 wt% Sc2O3 and 3% total zirconium and hafnium impurities.

[0077] The processing method includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 135 μm. The powder is then alkali-leached with a 10% sodium hydroxide solution at 90°C for 2 hours. The molar ratio of scandium oxide in the scandium-containing material to sodium hydroxide in the sodium hydroxide solution is 1:5 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.5 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out at a reaction temperature of 45℃, a reaction time of 1.75h, 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 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 scandium precipitate was dried, calcined at 700℃ for 3.8h, and washed by hydrothermal pulping at 175℃ for 1.75h to obtain scandium oxide; (5) After evaporating and crystallizing the scandium precipitation mother liquor, sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution.

[0078] Calculation results: Scandium recovery rate 98.84%, scandium oxide purity 99.94%.

[0079] Example 4

[0080] This embodiment provides an alkaline leaching and carbonization treatment method for scandium-containing materials, and recovers scandium to obtain scandium oxide product. The scandium-containing material contains 95 wt% Sc2O3 and 2% total hafnium and titanium impurities.

[0081] The processing method includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 75 μm. The powder is then alkali-leached with a 7% sodium hydroxide solution at 115°C for 1.5 h. The molar ratio of scandium oxide in the scandium-containing material to sodium hydroxide in the sodium hydroxide solution is 1:5 to obtain a mixed slurry. (2) Carbon dioxide gas with a pressure of 0.3 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out according to the reaction temperature of 30℃, the reaction time of 0.8h, and the endpoint pH=8. Liquid-solid separation is performed to obtain scandium-containing leaching solution and leaching residue. (3) After removing impurities from the scandium-containing leaching solution 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 scandium precipitate was dried, calcined at 725°C for 4 hours, and washed with hydrothermal pulping at 160°C for 0.75 hours to obtain scandium oxide; (5) After evaporating and crystallizing the scandium precipitation mother liquor, sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution.

[0082] Calculation results: Scandium recovery rate 99.26%, scandium oxide purity 99.96%.

[0083] Example 5

[0084] This embodiment provides an alkaline leaching and carbonization treatment method for scandium-containing materials, recovers scandium to obtain scandium oxide product, and recovers zirconium from the leaching residue after scandium extraction to obtain zirconium oxide product.

[0085] The scandium-containing material contains 6.82 wt% Sc2O3, 89.34 wt% ZrO2, and a total of 2% hafnium and titanium.

[0086] The processing method includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 60 μm. The powder is then alkali-leached with a 6% sodium hydroxide solution at 100°C for 3 hours. The molar ratio of scandium oxide in the 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 at 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 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 scandium precipitate was dried, calcined at 750°C for 3.9 h, and washed with hydrothermal pulping at 190°C for 0.25 h to obtain scandium oxide.

[0087] (5) The leaching residue from step (2) was leached with 20% sodium hydroxide solution at 125°C for 4 hours. The molar ratio of zirconium oxide to sodium hydroxide solution was 1:8. The liquid-solid separation yielded a zirconium-containing leaching solution (containing hafnium titanium). The zirconium-containing leaching solution was then introduced with carbon dioxide at a pressure of 0.4 MPa and carbonized at a reaction temperature of 75°C, a reaction time of 3 hours, and an endpoint pH of 11.5. The liquid-solid separation yielded a zirconium precipitate. The zirconium precipitate was dried, calcined at 1000°C for 2.3 hours, and then hydrothermally washed at 145°C for 3 hours to obtain zirconium oxide.

[0088] Calculation results: Scandium recovery rate 98.98%, scandium oxide purity 99.94%.

[0089] Zirconium recovery rate was 98.67%, and zirconium oxide purity was 94.52%.

[0090] This embodiment achieves zirconium component extraction by alkaline leaching and carbonization treatment of the leaching residue after scandium extraction. The zirconium recovery rate is high. However, since hafnium and titanium impurities have similar properties to zirconium, they will leach out simultaneously with zirconium during the leaching process, thus affecting the purity of the final zirconium oxide product.

[0091] Comparative Example 1

[0092] In this comparative example, the scandium-containing material is the same as in Example 1.

[0093] Includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 125 μm. The powder is then alkali-leached with a 15% sodium hydroxide solution at 150°C for 2.5 h. The molar ratio of scandium oxide in the 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 0.7 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out at a reaction temperature of 40℃, 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 100°C for 1.5 hours to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The scandium precipitate obtained in step (3) is dried, calcined at 845°C for 2 hours, and then hydrothermally washed at 150°C for 1 hour to obtain scandium oxide; (5) After evaporating and crystallizing the scandium mother liquor mentioned in step (3), sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution in step (1).

[0094] Calculation results: Scandium recovery rate 99.29%, scandium oxide purity 94.80%.

[0095] Comparative Example 2

[0096] In this comparative example, the scandium-containing material is the same as in Example 1.

[0097] Includes the following steps: (1) The scandium-containing material is crushed and ground into powder with a particle size of no more than 125 μm. The powder is then alkali-leached with a 10% sodium hydroxide solution at 100°C for 2.5 h. The molar ratio of scandium oxide in the 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 0.04 MPa is introduced into the mixed slurry of step (1), and carbonization is carried out at a reaction temperature of 60℃, a reaction time of 1h, and an endpoint pH of 12. 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 1.5 hours to separate the liquid and solid, and obtain scandium precipitate and scandium mother liquor; (4) The scandium precipitate obtained in step (3) is dried, calcined at 845°C for 2 hours, and then hydrothermally washed at 150°C for 1 hour to obtain scandium oxide; (5) After evaporating and crystallizing the scandium mother liquor mentioned in step (3), sodium carbonate is recovered. The crystallization mother liquor and steam condensate are reused to prepare alkali solution in step (1).

[0098] Calculation results: Scandium recovery rate 94.25%, scandium oxide purity 99.92%.

[0099] This invention employs an alkaline leaching and carbonization process to obtain a scandium-containing leaching solution. Based on this solution, scandium is recovered to obtain a high-purity scandium oxide product; the scandium recovery rate is ≥98%, and the purity of the scandium oxide product is ≥99%. Furthermore, the method of this invention utilizes low-temperature alkaline leaching and carbonization reactions, reducing energy consumption. The process water can be recycled and reused, and sodium carbonate is produced as a byproduct. The process is clean and pollution-free, and has broad application prospects.

[0100] As can be seen from Example 1 and Comparative Example 1, if the alkali leaching concentration is too high, zirconium and impurities with similar properties will also be activated, affecting the selective scandium extraction effect and resulting in a decrease in the purity of the scandium product.

[0101] As can be seen from Example 1 and Comparative Example 2, when carbonation is used to extract scandium, if the pH at the carbonation endpoint is too high, the carbonation temperature is too high, or the partial pressure of carbon dioxide is too low, the carbonation leaching effect will be poor, resulting in a decrease in the scandium recovery rate.

[0102] 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 alkaline leaching and carbonization treatment of scandium-containing materials, characterized in that, include: Step S1: Alkali leaching is performed on the scandium-containing material to obtain a mixed slurry; Step S2: Carbon dioxide is passed through the mixed slurry to perform carbonation selective scandium impregnation, followed by liquid-solid separation to obtain scandium-containing impregnation solution and impregnation residue.

2. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 1, characterized in that, In step S1, the concentration of the alkali solution added for the alkali leaching treatment is 3-12%, preferably 5%-10%; the alkali leaching treatment temperature is 60-180℃, preferably 80-120℃. In step S2, the endpoint pH of selective scandium immersion in carbonation is 5-11, preferably 7.5-9.5; the temperature is 25-45℃.

3. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 2, characterized in that, In step S1, during the alkali leaching treatment, the molar ratio of scandium in the scandium-containing material to alkali in the alkali solution is 1:(2.5-8). The added alkaline solution is either sodium hydroxide solution or potassium hydroxide solution.

4. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 3, characterized in that, In step S2, the pressure of the carbon dioxide gas introduced is 0.05-1.5 MPa, preferably 0.07-1.25 MPa.

5. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 1, characterized in that, Also includes: Step S3: After removing impurities from the scandium-containing leaching solution, pyrolyze it and separate the liquid and solid to obtain scandium precipitate and scandium mother liquor; Step S4: The scandium precipitate is dried, calcined, and washed to obtain scandium oxide.

6. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 5, characterized in that, In step S3, the pyrolysis temperature is 90-120℃ and the pyrolysis time is 0.25-3h; In step S4, the calcination temperature is 600-1100℃ and the calcination time is 2-4h.

7. The alkaline leaching and carbonization treatment method for scandium-containing materials according to claim 5, characterized in that, In step S4, the washing is a hydrothermal slurry washing, and the hydrothermal slurry washing temperature is 100-250℃.

8. The method for alkaline leaching and carbonization treatment of scandium-containing materials according to claim 5, characterized in that, Also includes: Step S5: Evaporate and crystallize the scandium precipitation mother liquor to recover sodium carbonate; and reuse the generated steam condensate and crystallization mother liquor to prepare the alkaline solution used in step S1 alkaline leaching treatment.

9. The method for alkaline leaching and carbonization treatment of scandium-containing materials according to claim 1, characterized in that, Before step S1, the following is also included: The scandium-containing material is crushed and ground to obtain scandium-containing material with a particle size of no more than 150 μm.

10. The method for alkaline leaching and carbonization treatment of scandium-containing materials according to claim 1, characterized in that, The scandium-containing material contains 1-95% scandium oxide. Other elements in the scandium-containing material include one or more of zirconium, hafnium, and titanium.

11. The method for alkaline leaching and carbonization treatment of scandium-containing materials according to claim 10, characterized in that, The scandium-containing material is preferably a solid oxide fuel cell, with a scandium oxide content of 5-15%.

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