Method for preparing scandium oxide from laterite-nickel ore

Abstract

The invention provides a method for preparing scandium oxide from laterite-nickel ore, which comprises the following steps: slurrying and leaching iron-removed aluminum slag of laterite-nickel ore to obtain scandium leachate; ammonium sulfate is added into the scandium leachate for a precipitation reaction, and ammonium scandium sulfate is obtained; re-dissolving ammonium scandium sulfate in water and precipitating again, and then roasting and leaching the re-dissolved and re-precipitated ammonium scandium sulfate to obtain a scandium sulfate solution; after Fe < 3 + > in the scandium sulfate solution is reduced into Fe < 2 + >, scandium reduction extraction is carried out, a loaded organic phase obtained after scandium extraction is washed and reversely extracted, and a purified scandium sulfate solution is obtained; and carrying out precipitation treatment on the purified scandium sulfate solution to obtain a precipitate, and carrying out post-treatment on the precipitate to obtain scandium oxide. According to the process, the high-purity scandium oxide is prepared through the procedures of high-pressure leaching, ammonium scandium sulfate re-dissolution and re-precipitation, Fe < 3 + > reduction, reduction extraction and the like, meanwhile, alkali reverse extraction is not needed in the extraction procedure, and reverse extraction can be achieved through common sulfuric acid.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology of laterite nickel ore, and relates to a method for preparing scandium oxide from laterite nickel ore. Background Technology

[0002] Scandium is an extremely scarce resource. Even trace amounts of scandium and its oxides can significantly improve the high-temperature resistance, weldability, and corrosion resistance of materials. Therefore, it has very attractive development prospects in aviation, aerospace, shipbuilding, nuclear reactors, and automobiles.

[0003] As is well known, lateritic nickel ore has a complex composition, with a scandium content of approximately 10-50 ppm. Since the first successful preparation of scandium oxide from lateritic nickel ore using existing technologies, such as the method for extracting scandium from lateritic nickel ore disclosed in CN 103468980A, existing technologies have also utilized P204, P507, and C272 extractants to extract and prepare scandium oxide from lateritic nickel ore and industrialize it. However, the extractants used in currently industrialized scandium oxide production all require back-extraction with alkali or oxalic acid to form insoluble scandium precipitates. This severely affects the phase separation process during extraction, clogs the pipeline structure of the extraction tank, and damages the performance of the extractant, thus hindering the operation of the extraction process. Furthermore, the purity of the scandium oxide currently prepared is generally at the 3N level, which cannot meet the requirements for use in the aerospace field.

[0004] Based on the above research, there is a need to provide a method for preparing scandium oxide from laterite nickel ore. This method can achieve the preparation of high-purity scandium oxide, and the extraction process does not require alkaline reaction; ordinary sulfuric acid can be used for back-extraction. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing scandium oxide from laterite nickel ore, wherein the method involves high-pressure leaching, scandium ammonium sulfate re-dissolution and re-precipitation, and Fe... 3+ The reduction and reduction extraction processes enable the preparation of high-purity scandium oxide. Meanwhile, the extraction process does not require alkaline reaction and can be achieved using ordinary sulfuric acid.

[0006] To achieve this objective, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing scandium oxide from laterite nickel ore, the method comprising the following steps:

[0008] (1) The iron and aluminum slag of laterite nickel ore is pulped and then leached to obtain scandium leachate;

[0009] (2) Add ammonium sulfate to the scandium leachate obtained in step (1) to carry out a precipitation reaction to obtain scandium ammonium sulfate;

[0010] (3) Add water to the scandium sulfate in step (2) to slurry it, so that the scandium sulfate is re-dissolved in water. Then add sulfuric acid and ammonium sulfate to precipitate the scandium sulfate again, and obtain the scandium sulfate after re-dissolution and re-precipitation.

[0011] (4) The scandium sulfate that has been dissolved and precipitated in step (3) is roasted and leached in water to obtain a scandium sulfate solution;

[0012] (5) Remove the Fe from the scandium sulfate solution described in step (4). 3+ Reduced to Fe 2+ Then, scandium reduction extraction was performed. The loaded organic phase after scandium extraction was washed and back-extracted in sequence to obtain a purified scandium sulfate solution.

[0013] (6) The purified scandium sulfate solution described in step (5) is subjected to precipitation treatment to obtain a precipitate, and the precipitate is then subjected to post-treatment to obtain scandium oxide.

[0014] This invention first employs high-pressure leaching to leach Sc from iron-aluminum removal slag in laterite nickel ore, while simultaneously pressing Fe, Al, and Cr into the slag to reduce acid consumption during Sc leaching and the pressure required for subsequent purification. Then, ammonium sulfate precipitation is performed. In this process, the poor solubility of the double salt Sc2(SO4)3·(NH4)2SO4 is utilized to separate Sc from Ni, Co, Mn, Zn, Cu, Ca, Mg, Fe, Al, V, Ti, and Cr in the leachate. Further purification of Si and these impurities in the ammonium sulfate is achieved through ammonium sulfate re-dissolution and re-precipitation. The calcination of ammonium sulfate utilizes the differences in decomposition temperatures of different metal sulfates and the poor solubility of silica to separate Sc from Fe, Al, Ti, Fe, Cr, Th, V, and Si. The subsequent water leaching stage utilizes the differences in the pH hydrolysis properties of different metals to separate Sc from Fe and Al from Th. The D366 extractant exhibits significantly higher selectivity for Sc than for Fe. 2+ , Al, Ni, Co, Mn, Cr, Ca, Mg, Na, for Fe 3+ Due to its high extraction rate, the scandium sulfate solution obtained by calcining and leaching scandium sulfate in water needs to be treated with a reducing agent before extraction to remove Fe from the Sc solution. 3+ Reduced to Fe 2+ Furthermore, reduction is required during extraction to fully preserve Fe. 3+ The scandium oxide is not extracted; sulfuric acid can be used as the extractant for back-extraction, eliminating the need for alkaline back-extraction. Finally, the scandium sulfate solution obtained from back-extraction undergoes precipitation and post-treatment to obtain scandium oxide. Ammonium oxalate precipitation can separate Sc from Fe, Al, Ti, Ca, Mg, and some Th. To ensure the purity of scandium oxide, the pH of the system and the calcination temperature and time of scandium oxalate during precipitation should be carefully controlled.

[0015] Preferably, the leaching method in step (1) includes high-pressure acid leaching.

[0016] Preferably, the leaching temperature in step (1) is 180-260℃, for example, it can be 180℃, 185℃, 190℃, 195℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃ or 260℃, and the time is 0.5-2h, for example, it can be 0.5h, 0.75h, 1h, 1.25h, 1.5h, 1.75h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Preferably, the scandium leachate in step (1) is evaporated and concentrated by 2-4 times (e.g., 2 times, 3 times or 4 times) to increase the Sc concentration, so as to reduce the cost of the subsequent ammonium salt precipitation process by several times.

[0018] Preferably, the temperature for the precipitation reaction of adding ammonium sulfate in step (2) is 40-60℃, for example, 40℃, 45℃, 50℃, 55℃ or 60℃, and the time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h or 3h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] Preferably, in step (2), the pH of the ammonium precipitation system is controlled by adding acid at 0.5 to 2, for example, it can be 0.5, 1, 1.5 or 2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the amount of ammonium sulfate added in step (2) is 1.1 to 1.5 times the theoretical amount, for example, it can be 1.1 times, 1.2 times, 1.3 times, 1.4 times or 1.5 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, after adding ammonium sulfate in step (2) to carry out the precipitation reaction, the sample is subjected to a concentrated filtration process to obtain the scandium sulfate.

[0022] Preferably, after the reprecipitation in step (3), a thick filtration process is performed to obtain the scandium sulfate after re-dissolution and reprecipitation.

[0023] Preferably, the temperature for calcining the scandium sulfate after re-dissolution and re-precipitation in step (4) is 500-650℃, for example, 500℃, 550℃, 600℃ or 650℃, and the time is 1-4h, for example, 1h, 2h, 3h or 4h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the pH of the water immersion in step (4) is ≤2.5, for example, it can be 2.5, 2.4, 2.3, 2.2, 2.1, 2.0 or 1.9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] In step (4) of this invention, the pH of the water immersion is ≤2.5, which promotes the full leaching of scandium.

[0026] Preferably, a reducing agent is used to remove the Fe in the scandium sulfate solution described in step (4). 3+ Reduced to Fe 2+ .

[0027] Preferably, the reducing agent includes sodium sulfite (Na2SO3), sodium metabisulfite (Na2S2O5), sodium bisulfite (NaHSO3), sodium sulfide (Na2S), or SO2 gas, preferably SO2 waste gas generated during the production of acid from laterite nickel ore.

[0028] Preferably, SO2 is introduced during scandium reduction extraction in step (5).

[0029] Preferably, during the scandium reduction extraction in step (5), SO2 is introduced into the extraction tanks of the extraction section and the washing section.

[0030] In the scandium reduction extraction described in this invention, SO2 is preferably introduced into the extraction tank of the extraction section to maintain the reducing properties during extraction.

[0031] Preferably, the scandium reduction extraction in step (5) uses DY366 produced by Deyuan Fine Chemicals Co., Ltd. as the extractant.

[0032] Preferably, the precipitant used in step (6) includes oxalic acid.

[0033] During precipitation, the pH needs to be maintained at 1-2.5. The pH adjuster used is sodium carbonate / ammonium or sodium bicarbonate / ammonium, preferably an ammonium salt.

[0034] Preferably, the post-processing step (6) includes calcining, washing and drying the precipitate in sequence.

[0035] Preferably, the scandium oxide is of the 4N grade with a purity ≥ 99.99%, for example, it can be 99.99%, 99.991%, 99.995%, or 99.999%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0036] Preferably, the scandium recovery rate of the method is >95%, for example, it can be 95.5%, 96%, 96.5%, 97%, 97.5% or 98%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] The method described in this invention involves high-pressure leaching, scandium sulfate re-dissolution and re-precipitation, and Fe... 3+ The reduction and reduction extraction processes enable the preparation of high-purity scandium oxide. Meanwhile, the extraction process does not require alkaline reaction and can be achieved using ordinary sulfuric acid. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be considered as specific limitations thereof. The composition of the iron-aluminum slag from laterite nickel ore is shown in Table 1.

[0039] Table 1, the units in Table 1 are wt%.

[0040]

[0041] Example 1

[0042] This embodiment provides a method for preparing scandium oxide from laterite nickel ore, the method comprising the following steps:

[0043] Step (1) High-pressure leaching: The iron and aluminum slag of laterite nickel ore is pulped, and then sulfuric acid is added for high-pressure leaching to obtain scandium leaching solution. The leaching reaction temperature is 190℃, the acid-slag ratio is 0.35, and the leaching time is 1h.

[0044] Step (2) Ammonium salt precipitation: After the scandium leaching solution in step (1) is evaporated and concentrated three times, ammonium sulfate is added to carry out a precipitation reaction. The amount of ammonium sulfate used is 1.4 times the theoretical amount. The precipitation reaction temperature is 50℃ and the reaction time is 2h. Sulfuric acid is added to control the pH of the ammonium precipitation system to 1.8. After the reaction is completed, scandium ammonium sulfate (NH4Sc(SO4)2) is obtained by dense filtration.

[0045] Step (3) Scandium sulfate re-dissolution and re-precipitation: The scandium sulfate obtained in step (2) is slurried and re-dissolved in water with a liquid-to-solid ratio of 8:1. Then sulfuric acid and ammonium sulfate are added, and the sample is precipitated again to obtain scandium sulfate. The parameters are the same as in step (2). After the reaction is completed, the sample is filtered to obtain scandium sulfate filter cake.

[0046] Step (4) Scandium sulfate roasting and water leaching: The scandium sulfate filter cake obtained in step (3) is roasted to obtain scandium sulfate. The roasting temperature is 550℃ and the roasting time is 2h. Then, the scandium sulfate solid obtained by roasting is directly leached in water to obtain scandium sulfate solution. The water leaching temperature is 50℃, the time is 2h, and the pH is 1.5.

[0047] Step (5) Fe 3+Reduction: The SO2 tail gas generated during acid production at the laterite nickel ore enterprise is passed into the scandium sulfate solution described in step (4) to reduce Fe. 3+ Reduced to Fe 2+ ;

[0048] Step (6) Sc reduction extraction: The DY366 extract organic phase with a dilution rate of 50% and a saponification rate of 40% is mixed with the scandium sulfate solution obtained in step (5) at an O / A ratio of 1:1. At the same time, SO2 is introduced into the extraction tanks of the extraction and washing sections to prevent Fe 2+ Oxidation, then with H + Fe, Al, Ni, Co, Mn, Cr, Ca, and Mg impurities in the supported organic phase after scandium extraction were washed with a 0.2 mol / L sulfuric acid solution at an O / A ratio of 15:1. The washings were then returned to the extraction section for further recovery of Sc. Finally, the solution was treated with H₂O. + A 4.5 mol / L sulfuric acid solution was back-extracted at an O / A ratio of 5:1 to obtain a purified scandium sulfate solution. This extraction process consisted of 4 extraction stages, 3 washing stages, 5 back-extraction stages, 1 organic washing stage, and 1 organic clarification stage. The back-extracted organic material was washed with water, saponified, and recycled back to the extraction stage for continued use.

[0049] Step (7) Scandium precipitation: The purified scandium sulfate solution described in step (6) is subjected to precipitation treatment to obtain scandium precipitate. The precipitant used is oxalic acid, the amount of oxalic acid used is 1.1 times the theoretical amount, the precipitation reaction temperature is 45℃, the reaction time is 1 h, and the pH of the precipitation system is adjusted to 1.6 by ammonium bicarbonate.

[0050] Step (8) Post-treatment of scandium precipitate: The scandium precipitate obtained in step (7) is washed, calcined at 850°C for 2 hours, and then the calcined product is washed and dried to obtain scandium oxide.

[0051] Example 2

[0052] This embodiment provides a method for preparing scandium oxide from laterite nickel ore. The leaching reaction temperature in step (1) of the method is adjusted from 200°C to 250°C, and other conditions are exactly the same as in Example 1.

[0053] Example 3

[0054] This embodiment provides a method for preparing scandium oxide from laterite nickel ore. In step (2) of the method, the amount of ammonium sulfate is adjusted from 1.4 times to 1.2 times the theoretical amount, and other conditions are exactly the same as in Example 1.

[0055] Example 4

[0056] This embodiment provides a method for preparing scandium oxide from laterite nickel ore. In step (4) of the method, the roasting temperature is adjusted from 550°C to 630°C, and other conditions are exactly the same as in Example 1.

[0057] Example 5

[0058] This embodiment provides a method for preparing scandium oxide from laterite nickel ore. In step (5), the SO2 tail gas generated during acid production at a laterite nickel ore enterprise is introduced into the scandium sulfate solution described in step (4) to react with Fe. 3+ Reduced to Fe 2+ The method was adjusted to add Na2S, with the amount being 1.2 times the theoretical amount, while other conditions remained exactly the same as in Example 1.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing scandium oxide from laterite nickel ore. The method is the same as in Example 1 except that step (3) of re-dissolving and re-precipitating scandium sulfate is not performed, and the scandium sulfate obtained by precipitating ammonium salt in step (2) is directly roasted and leached in water in step (4).

[0061] Comparative Example 2

[0062] This comparative example provides a method for preparing scandium oxide from laterite nickel ore, except that step (5) Fe is not performed. 3+ Except for the reduction, which involves directly performing the scandium sulfate solution described in step (4) on the Sc reduction extraction in step (6), the process is the same as in Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a method for preparing scandium oxide from laterite nickel ore. The method is the same as in Example 1 except that SO2 is not introduced during the extraction of scandium in step (6) and the extraction is not carried out in a reducing system in step (6).

[0065] The purity of the scandium oxide obtained in the above examples and comparative examples was determined by ICP, and the scandium content in the original laterite nickel ore iron-aluminum slag phase was determined by ICP. The scandium recovery rate was calculated. The purity and specific composition of the obtained scandium oxide, as well as the overall scandium recovery rate, are shown in Table 2. All units are %:

[0066] Table 2

[0067]

[0068] As can be seen from the table above:

[0069] As can be seen from the table, the purity and composition of Sc2O3 prepared by the process of the present invention meet the standard of Sc2O3-4N in GB / T 13219-2018, and the recovery rate of Sc in the whole process is >95%.

[0070] Comparing Examples 1 and 2, it can be seen that in the high-pressure leaching process of iron and aluminum removal slag from laterite nickel ore, increasing the leaching temperature not only significantly reduces the Fe and Al content in the final Sc2O3 product and improves the purity of Sc2O3, but also increases the overall recovery rate of Sc. This is because increasing the high-pressure leaching temperature helps to retain Fe, Al, and Cr in the slag. In the high-pressure leaching stage, the acid-to-ore ratio also has a significant impact. Increasing the acid-to-ore ratio is beneficial for increasing the leaching rate of Sc, but more Fe, Al, and Cr will also be leached. If the acid-to-ore ratio is too low, the leaching rate of Sc will be too low; therefore, the acid-to-ore ratio should not be too high or too low. Furthermore, appropriately extending the high-pressure leaching time is beneficial for the Sc leaching reaction, but excessively long times will be detrimental to production efficiency; a balance should be maintained.

[0071] Comparing Examples 1 and 3, it can be seen that in the ammonium sulfate precipitation stage, appropriately reducing the amount of ammonium sulfate helps separate Sc from impurities such as Fe, Al, Ca, Mg, Cu, V, and Ni, significantly improving the purity of Sc2O3. However, the overall recovery rate of Sc shows a decreasing trend. Generally, insufficient ammonium sulfate reduces the recovery rate of Sc without affecting purity, while excessive ammonium sulfate causes Sc to form complex salts with more Fe and Al impurities, along with some Ca and Mg sulfates, leading to co-precipitation of impurities, which is detrimental to the purity of Sc2O3. Therefore, while considering the recovery rate, the amount of ammonium sulfate should be controlled according to product requirements. In addition, the pH control, reaction temperature, and time of the system during ammonium precipitation are also important. Regarding pH control, the lower the pH, the higher the purity of Sc2O3, but this is detrimental to production cost control. If the pH is too high (pH>3), Fe and Al will hydrolyze, thereby reducing the purity of Sc2O3. Temperature generally significantly affects the particle size and purity of scandium ammonium sulfate by influencing the ion diffusion rate and crystal growth kinetics. Too low a temperature results in a slow crystallization rate and small particle size of the formed scandium sulfate double salt, which easily adsorbs various impurities in the system, negatively impacting Sc2O3 purity control. Too high a temperature leads to the decomposition of ammonium sulfate. Generally, 50℃ is better, balancing crystallization efficiency and energy consumption. Reaction time directly affects the integrity of the scandium sulfate double salt crystals and the adsorption / desorption of impurities during the precipitation reaction. Insufficient reaction time leads to incomplete formation of scandium sulfate double salt nuclei, resulting in a loose crystal structure and increased surface adsorption of impurities, which is detrimental to Sc2O3 purity control. Excessive reaction time causes excessive crystal growth, leading to encapsulation of the mother liquor, and some double salts may dehydrate and decompose, causing Sc2O3 purity to decrease rather than increase.

[0072] Comparing Examples 1 and 4, it can be seen that in the scandium sulfate roasting and water leaching process, increasing the roasting temperature of scandium sulfate significantly reduces the content of impurities such as Fe, Al, V, Si, Ti, and Th in Sc2O3, improving the purity of Sc2O3 and simultaneously increasing the recovery rate of Sc. This is because, with increased roasting temperature, the sulfates of impurities such as Fe, Al, V, Ti, and Th in the scandium sulfate double salt, as well as silicic acid, will transform into oxide forms, making them difficult to leach out with water. Simultaneously, the higher the roasting temperature, the more fully scandium sulfate will decompose into scandium sulfate, thereby increasing the recovery rate of Sc. However, excessively high roasting temperatures will cause scandium sulfate to transform into insoluble scandium oxide, leading to a significant decrease in the recovery rate of Sc. The roasting time also affects the separation of Sc from impurities and the subsequent recovery rate of Sc during water leaching by influencing the decomposition reaction of metal sulfates. In conclusion, roasting temperature and time are key factors determining product purity and yield. In the scandium sulfate leaching stage, the liquid-to-solid ratio, temperature, and time should be carefully controlled. Increasing the leaching temperature promotes the dissolution of Sc, but excessively high temperatures can also cause some Fe and Al to leach out in the weakly acidic environment. If the liquid-to-solid ratio is too low, the system viscosity will be too high during leaching, Sc will easily precipitate, and filtration will be hindered during solid-liquid separation. If the liquid-to-solid ratio is too high, the Sc leaching rate will be high, but production efficiency will be reduced, and some impurities such as Fe, Al, Ca, and Mg may also be leached out.

[0073] Comparing Examples 1 and 5, it can be seen that in the reduction of Fe 3+ If the reducing agent is changed from SO2 to Na2S, the Na content in Sc2O3 increases significantly, and there is a risk of exceeding the standard. Therefore, the type and amount of reducing agent added are crucial.

[0074] Comparing Examples 1-5 with Comparative Example 1, it can be seen that if the scandium sulfate re-dissolution and re-precipitation in step (3) of the present invention is not carried out, and the scandium sulfate obtained by the ammonium salt precipitation in step (2) is directly subjected to the scandium sulfate roasting and water leaching in step (4), the Fe, Al, Cu, Ni, Ca and Mg in the obtained Sc2O3 exceed the standard, and its purity and impurity content do not meet the requirements of the national standard for Sc2O3-4N.

[0075] Comparing Examples 1-5 and Comparative Examples 2-3, it can be seen that no reducing agent is added before or during extraction to reduce Fe. 3+ Fully transformed Fe 2+ The Fe content in Sc2O3 will be severely exceeded.

[0076] Therefore, the method of the present invention first uses the high-pressure leaching described in step (1) to leach Sc, pressing Fe, Al, and Cr into the residue to reduce acid consumption during Sc leaching and the pressure of subsequent purification. Then, scandium sulfate is precipitated, and the scandium sulfate obtained in step (2) is re-dissolved and re-precipitated, which helps to remove impurities and improve the purity of scandium sulfate. Then, the re-dissolved and re-precipitated scandium sulfate is first roasted to remove impurities by utilizing the difference in decomposition temperature of different metal sulfates, and then water leaching is performed to remove impurities. Finally, a reducing agent is added to the scandium sulfate solution before extraction to remove Fe. 3+ Reduced to Fe 2+ Simultaneously, reduction is carried out during extraction to fully preserve Fe. 3+ It is not extracted; finally, the scandium sulfate solution obtained by back-extraction is selectively precipitated with oxalic acid and calcined to obtain high-purity scandium oxide.

[0077] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing scandium oxide from laterite nickel ore, characterized in that, The method includes the following steps: (1) The iron and aluminum slag of laterite nickel ore is pulped and then leached to obtain scandium leachate; (2) Add ammonium sulfate to the scandium leachate obtained in step (1) to carry out a precipitation reaction to obtain scandium ammonium sulfate; (3) Add water to the scandium sulfate in step (2) to slurry it, so that the scandium sulfate is re-dissolved in water. Then add sulfuric acid and ammonium sulfate to precipitate the scandium sulfate again, and obtain the scandium sulfate after re-dissolution and re-precipitation. (4) The scandium sulfate that has been dissolved and precipitated in step (3) is roasted and leached in water to obtain a scandium sulfate solution; (5) Remove the Fe from the scandium sulfate solution described in step (4). 3+ Reduced to Fe 2+ Then, scandium reduction extraction was performed, and the loaded organic phase after scandium extraction was washed and back-extracted in sequence to obtain a purified scandium sulfate solution. (6) The purified scandium sulfate solution described in step (5) is subjected to precipitation treatment to obtain a precipitate, and the precipitate is then subjected to post-treatment to obtain scandium oxide.

2. The method according to claim 1, characterized in that, The leaching method in step (1) includes high-pressure acid leaching; Preferably, the leaching temperature in step (1) is 180-260℃ and the leaching time is 0.5-2h; Preferably, the scandium leachate in step (1) is evaporated and concentrated by 2-4 times to increase the Sc concentration.

3. The method according to claim 1 or 2, characterized in that, The temperature for adding ammonium sulfate to carry out the precipitation reaction in step (2) is 40-60℃, and the time is 1-3h; Preferably, in step (2), acid is added to control the pH of the ammonium precipitation system to be between 0.5 and 2; Preferably, in step (2), the amount of ammonium sulfate added is 1.1 to 1.5 times the theoretical amount; Preferably, after adding ammonium sulfate in step (2) to carry out the precipitation reaction, the sample is subjected to a concentrated filtration process to obtain the scandium sulfate.

4. The method according to any one of claims 1-3, characterized in that, After the re-precipitation in step (3), a concentrated filtration process is performed to obtain the scandium sulfate after re-dissolution and re-precipitation.

5. The method according to any one of claims 1-4, characterized in that, In step (4), the scandium sulfate after re-dissolution and re-precipitation is calcined at a temperature of 500-650℃ for 1-4 hours. Preferably, the pH of the water immersion in step (4) is ≤2.

5.

6. The method according to any one of claims 1-5, characterized in that, The Fe in the scandium sulfate solution described in step (4) is removed by a reducing agent. 3+ Reduced to Fe 2+ ; Preferably, the reducing agent includes Na2SO3, Na2S2O5, NaHSO3, Na2S or SO2 gas, and more preferably SO2 waste gas generated during the production of acid from laterite nickel ore; Preferably, SO2 is introduced during the scandium reduction extraction in step (5); Preferably, during the scandium reduction extraction in step (5), SO2 is introduced into the extraction tanks of the extraction section and the washing section; Preferably, the scandium reduction extraction in step (5) uses DY366 as the extractant.

7. The method according to any one of claims 1-6, characterized in that, The precipitant used in step (6) is oxalic acid.

8. The method according to any one of claims 1-7, characterized in that, The post-processing steps in step (6) include calcining, washing and drying the precipitate in sequence.

9. The method according to any one of claims 1-8, characterized in that, The scandium oxide is of the 4N grade with a purity ≥99.99%.

10. The method according to any one of claims 1-9, characterized in that, The scandium recovery rate of the method is >95%.

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