Scandium recovery method based on organic scandium sulfonate double salt precipitation

Abstract

The present application relates to a kind of based on organic sulfonic acid scandium double salt precipitation scandium recovery method, comprising: using sulfuric acid to the scandium concentrate is treated by acid immersion to obtain the scandium-containing leaching solution;Scandium-containing leaching solution is adjusted to alkaline pH, and precipitate to obtain coarse scandium hydroxide;Coarse scandium hydroxide is reacted with organic sulfonic acid to obtain organic sulfonic acid scandium salt;Organic sulfonic acid scandium salt is mixed with saturated sulfate solution and carries out double salt precipitation, and separation is obtained containing scandium double salt;Scandium double salt is washed, precipitated by ammonia, acid dissolution, oxalate precipitation and high temperature calcination, and high-purity scandium oxide is obtained.The present application combines organic sulfonic acid scandium salt and sulfate for the first time to construct a new double salt precipitation system, which can realize efficient and high-selectivity separation of scandium, various rare earth elements and conventional metal impurities in a single precipitation, and obtain scandium oxide with purity higher than 99.9%.The total recovery rate of scandium is more than 85%.The process is simple, without complex saponification process, reducing the generation of salt-containing and ammonia-containing wastewater, and reducing equipment investment and operating cost.

Description

Technical Field

[0001] This application belongs to the field of hydrometallurgy and rare metal recovery technology, specifically relating to a scandium recovery method based on the precipitation of scandium complex salts of organic sulfonic acid. Background Technology

[0002] Scandium (Sc) is a rare metallic element of strategic importance. Due to its unique physicochemical properties, it is widely used in high-performance aluminum-scandium alloys, solid oxide fuel cells, laser crystals, and other high-end new materials. Because scandium is dispersed in nature and rarely forms independent deposits, it usually exists as a by-product in resources such as laterite nickel ore, rare earth ores, red mud, tungsten slag, and titanium dioxide waste acid. Therefore, its efficient recovery and purification has always been a research focus in related fields. Laterite nickel ore is an important raw material for modern nickel smelting. During its hydrometallurgical extraction of nickel and cobalt, scandium-rich intermediates, namely scandium concentrates, are produced. In addition to scandium, these intermediates typically contain rare earth elements such as yttrium, ytterbium, erbium, and lutetium, as well as conventional metallic impurities such as iron, aluminum, nickel, and manganese, making the highly selective separation and purification of scandium extremely challenging.

[0003] In existing technologies, methods for recovering scandium from complex solutions mainly include solvent extraction, ion exchange, and chemical precipitation. Although solvent extraction has high separation efficiency, it has a long process, requires sophisticated equipment, and easily generates high-salt organic waste liquid. Ion exchange is easily affected by the adsorption efficiency of trace scandium in high-impurity and high-acidity systems. Conventional precipitation methods such as oxalate precipitation and hydroxide precipitation are simple to operate, but they usually have poor selectivity for rare earth elements with similar chemical properties, making it difficult to achieve effective separation of scandium from coexisting rare earth elements.

[0004] Double salt precipitation is a classic rare earth separation technique, based on the difference in the ability of rare earth elements to form insoluble double salts with alkali metals or ammonium ions. Early research mainly focused on the separation of lanthanides. In recent years, although studies have reported various double salt crystal structures formed by scandium with ammonium or alkali metals (such as NH4Sc(SO4)2, (NH4)3Sc(SO4)3, Na3Sc(SO4)3, etc.), its application as a highly efficient and selective process for the separation of scandium, especially from scandium concentrates from laterite nickel ore hydrometallurgical processes, still lacks systematic and in-depth research.

[0005] Therefore, developing a new scandium separation and recovery technology based on complex salt precipitation, which features a simple process, high selectivity, and environmental friendliness, is of great significance for realizing the high-value utilization of this strategic resource. Summary of the Invention

[0006] The purpose of this application is to overcome the shortcomings of the prior art and provide a scandium recovery method based on the precipitation of scandium complex salts of organic sulfonic acid, so as to achieve efficient and selective separation and recovery of scandium from scandium concentrates containing various rare earth elements and conventional metal impurities.

[0007] The technical problem solved by this application is achieved through the following technical solution: A scandium recovery method based on scandium double salt precipitation of organic sulfonic acid, the method comprising the following steps: S1. The scandium concentrate is subjected to acid leaching with sulfuric acid to obtain a scandium-containing leachate; S2. Adjust the pH of the scandium-containing leachate to alkaline to precipitate crude scandium hydroxide (Sc(OH)3). S3. Crude scandium hydroxide is reacted with organic sulfonic acid to prepare scandium salts of organic sulfonic acid; S4. The scandium sulfonate salt and saturated sulfate solution are mixed in a certain proportion to carry out double salt precipitation, and the scandium-containing double salt is obtained by separation. S5. The scandium-containing complex salt is washed, precipitated with ammonia, dissolved in acid, precipitated with oxalate, and calcined at high temperature to obtain high-purity scandium oxide.

[0008] Furthermore, the concentration of the S1 sulfuric acid is 5% to 30%; the acid leaching temperature is 80 to 120°C; the leaching time is 2 to 4 hours; and the solid-liquid ratio of the scandium concentrate to the sulfuric acid is 1:10 to 1:30 (g / mL).

[0009] Furthermore, in step S2, the pH of the scandium-containing leachate is adjusted to 7-9 using a sodium hydroxide solution.

[0010] Furthermore, the organic sulfonic acid in S3 is any one of (S)-(+)-camphor-10-sulfonic acid, (R)-(-)-camphor-10-sulfonic acid, naphthalene-2-sulfonic acid, trifluoromethanesulfonic acid, or p-toluenesulfonic acid.

[0011] Furthermore, the saturated sulfate of S4 is any one of sodium sulfate (Na2SO4), potassium sulfate (K2SO4), ammonium sulfate ((NH4)2SO4), lithium sulfate (Li2SO4), magnesium sulfate (MgSO4), or calcium sulfate (CaSO4).

[0012] Furthermore, the solid-liquid ratio of the S4 organic scandium sulfonate salt to the saturated sulfate solution is 1:3 to 1:15 (g / mL).

[0013] Furthermore, in S5, the concentration of ammonia used for ammonia treatment is 5% to 15%, and the water used for washing is ultrapure water; the concentration of oxalic acid used for oxalate precipitation is 0.5 to 2 mol / L; the calcination temperature is 800 to 900℃, and the calcination time is 1 to 2 h.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention is the first to combine scandium organic sulfonate salts with sulfates to construct a novel double salt precipitation system, which can achieve efficient and highly selective separation of scandium from various rare earth elements (Y, Yb, Er, Lu, etc.) and conventional metal impurities (Fe, Al, Ni, Mn, etc.) in a single precipitation step. Under preferred conditions, the separation factors (β) of scandium from the main impurities Y and Yb can reach 834.4 and 834.6, respectively, and the removal rates of elements such as iron, aluminum, nickel, and manganese all exceed 90%.

[0015] 2. Compared with the traditional multi-stage solvent extraction process, the method of the present invention has a much shorter process flow, is simple to operate, does not require a complicated saponification process, reduces the generation of salt and ammonia-containing wastewater, and lowers equipment investment and operating costs.

[0016] 3. This invention reveals the key influence of the spatial structure and hydrophobicity of organic sulfonic acid anions on the formation of complex salts, and proposes and verifies the separation mechanism that "organic sulfonic acid anions promote the local enrichment of scandium ions, thereby inducing the selective precipitation of insoluble complex salts", providing new ideas for the development of novel rare earth separation technologies.

[0017] 4. By processing scandium concentrate from laterite nickel ore using the method of this invention, scandium oxide products with a purity higher than 99.9% can be obtained, and the total scandium recovery rate can reach 91.9%, thus achieving efficient and high-value recovery of the strategic metal scandium from this secondary resource. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0019] The present application will be further described in detail below through specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present application.

[0020] In this invention, the metal element content in the leachate, intermediate products and final products is determined by inductively coupled plasma mass spectrometry (ICP-MS); the composition of raw materials, leaching residue and solid products is analyzed by X-ray fluorescence spectrometry (XRF).

[0021] Scandium recovery (R, %): used to represent the completeness of scandium entering the solid phase during the double salt precipitation step, calculated according to the following formula: in: The concentration of scandium in the solution before precipitation is mg / L; The value represents the scandium concentration in the supernatant after precipitation, in mg / L.

[0022] Impurity removal rate (Q, %): This indicates the completeness to which impurity elements remain in the liquid phase during precipitation, and is calculated using the following formula: in: The concentration of impurity M in the organic sulfonate before precipitation is mg / g; The concentration of impurity M in the double salt after precipitation is in mg / g.

[0023] Separation factor (β): This measures the ease with which scandium is separated from impurity elements through precipitation. A higher value indicates easier separation. It is calculated using the following formula: Where and represent the contents of Sc and element M in the original sample (mg / g), respectively, and and represent the contents of Sc and element M in the double-salt product (mg / g), respectively. Example 1 An innovative method for scandium recovery based on the precipitation of scandium double salts from organic sulfonic acids is described in the following steps: (1) Take 10 g of scandium concentrate, add 200 mL of 10% sulfuric acid solution, and leach at 100℃ with stirring for 3 h. The solid-liquid ratio is 1:20 (g / mL). After leaching, filter to obtain scandium-containing leachate and leachate residue. The scandium leaching rate was found to be 98.50%.

[0024] (2) Slowly add 10 mol / L sodium hydroxide solution to the above scandium-containing leachate, adjust the pH of the solution to 8, let it stand and age, then centrifuge to separate the precipitate, and dry the precipitate to obtain crude scandium hydroxide Sc(OH)3.

[0025] (3) The crude Sc(OH)3, sulfuric acid and (S)-(+)-camphor-10-sulfonic acid were added to water according to the reaction stoichiometry and reacted at 120℃ for 3 h. After the reaction was completed, the reaction solution was evaporated, concentrated and dried to obtain solid scandium sulfonate Sc[(S)-CSA]3.

[0026] (4) Weigh 1.00 g Sc[(S)-CSA]3, add 6.0 mL of saturated Na2SO4 solution to make the solid-liquid ratio 1:6 (g / mL), mix evenly with magnetic stirring at room temperature, let stand until precipitation is complete, filter and dry to obtain a white scandium-containing double salt precipitate.

[0027] (5) Repeat the preparation and combine the obtained double salt precipitates under the above conditions. Take 20 g of double salt precipitate and dissolve it in an appropriate amount of water. Add 10% ammonia water to adjust the pH to 8 so that scandium is redeprecipitated in the form of Sc(OH)3. Wash the obtained Sc(OH)3 three times with ultrapure water and dry it. Then dissolve it with sulfuric acid, add 1.0 mol / L oxalic acid solution and control the pH to 1.5-3.0 to generate scandium oxalate precipitate. Calcine the scandium oxalate precipitate at 900℃ for 1 h to obtain high-purity Sc2O3 product.

[0028] In this embodiment, the scandium recovery rate of the double salt precipitation step was 91.85%; the purity of the final obtained Sc2O3 was 99.9%, and the total recovery rate from scandium concentrate to scandium oxide product was 85.51%.

[0029] Example 2 An innovative method for scandium recovery based on scandium double salt precipitation of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that in step (3), (R)-(-)-camphor-10-sulfonic acid is used instead of (S)-(+)-camphor-10-sulfonic acid to prepare Sc[(R)-CSA]3; in step (4), the solid-liquid ratio used for double salt precipitation is adjusted to 1:3 (g / mL).

[0030] Specifically, 1.00 g of Sc[(R)-CSA]3 was weighed, added to 3.0 mL of saturated Na2SO4 solution, stirred and mixed, and allowed to stand until precipitation was complete. After filtration and drying, a scandium-containing double salt precipitate was obtained.

[0031] In this embodiment, the scandium recovery rate in the double salt precipitation step was 91.32%; the removal rates of the main rare earth impurities Y and Yb were 96.29% and 96.34%, respectively; and the separation factors of scandium from Y and Yb were both greater than 800, indicating that (R)-CSA can also achieve effective separation of scandium from other rare earth elements.

[0032] Example 3 An innovative method for scandium recovery based on the precipitation of scandium complex salts of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that naphthalene-2-sulfonic acid is used to prepare Sc(2-NSA)3 in step (3); saturated K2SO4 solution is used instead of saturated Na2SO4 solution in step (4), and the solid-liquid ratio is 1:15 (g / mL).

[0033] Specifically, 1.00 g of Sc(2-NSA)3 was weighed, added to 15.0 mL of saturated K2SO4 solution, stirred and mixed, and allowed to stand until precipitation was complete. The mixture was then filtered and dried to obtain a double salt precipitate.

[0034] In this embodiment, the scandium recovery rate of the double salt precipitation step was 96.98%, but the removal rates of major rare earth impurities such as Y and Yb were all below 50%, indicating that although the system is beneficial to improving the precipitation recovery rate of scandium, it has poor selective separation effect on coexisting rare earth impurities.

[0035] Example 4 An innovative method for scandium recovery based on the precipitation of scandium complex salts of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that in step (3), different types of saturated sulfate solutions are used instead of saturated Na2SO4 solution, while the other conditions remain unchanged. The sulfates are Li2SO4, K2SO4, (NH4)2SO4, MgSO4 and CaSO4, and the solid-liquid ratio is 1:6 (g / mL).

[0036] Specifically, 1.00 g of Sc[(S)-CSA]3 was weighed and added to 6.0 mL of the corresponding saturated sulfate solution. The mixture was stirred, allowed to stand to precipitate, filtered, and dried to obtain double salt precipitates in different systems.

[0037] The results showed that Na₂SO₄ achieved the highest scandium recovery rate (91.85%) and the best selectivity for rare earth impurities. Using (NH₄)₂SO₄ and K₂SO₄, the scandium recovery rates were 73.17% and 66.74%, respectively. Using Li₂SO₄, MgSO₄, and CaSO₄ significantly increased scandium loss, hindering efficient scandium recovery. Therefore, Na₂SO₄ is the preferred double salt precipitant in this invention.

[0038] Example 5 An innovative method for scandium recovery based on the precipitation of scandium complex salts of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that in step (4), the solid-liquid ratio of Sc[(S)-CSA]3 to saturated Na2SO4 solution is changed to 1:3, 1:9, 1:12 and 1:15 (g / mL), respectively, while the other conditions are the same as in Example 1.

[0039] In each group of experiments, 1.00 g of Sc[(S)-CSA]3 was weighed and added to 3.0 mL, 9.0 mL, 12.0 mL and 15.0 mL of saturated Na2SO4 solution, respectively. The mixture was stirred, allowed to stand, filtered and dried to investigate the effect of solid-liquid ratio on the recovery efficiency and selectivity of the double salt precipitation.

[0040] The results showed that when the solid-liquid ratio was 1:6 (Example 1), the removal effect of rare earth impurities was most balanced while maintaining a high scandium recovery rate. When the solid-liquid ratio was 1:3, the scandium recovery rate increased slightly, but the removal rate of some light rare earth impurities decreased. As the solid-liquid ratio further increased to 1:9, 1:12, and 1:15, the scandium recovery rate gradually decreased. Therefore, a solid-liquid ratio of 1:6 is the preferred condition.

[0041] Example 6 An innovative method for scandium recovery based on scandium double salt precipitation with organic sulfonic acid is described in the following steps: This embodiment is used to examine the separation effect of major heavy rare earth impurities under the preferred conditions of Example 1. Sc[(S)-CSA]3 is prepared according to the method of Example 1, and double salt precipitation is performed using saturated Na2SO4 solution at a solid-liquid ratio of 1:6 (g / mL).

[0042] The changes in the content of major rare earth impurities before and after precipitation were as follows: Y decreased from 1.127 mg / g to 0.015 mg / g, Yb decreased from 1.088 mg / g to 0.015 mg / g, Er decreased from 0.135 mg / g to 0.0025 mg / g, and Lu decreased from 0.242 mg / g to 0.0035 mg / g.

[0043] According to the formula, the removal rates of Y, Yb, Er, and Lu are 98.67%, 98.67%, 98.14%, and 98.54%, respectively; the separation factors of scandium with Y, Yb, Er, and Lu are 834.4, 834.6, 593.0, and 761.0, respectively. The results show that the method of the present invention has excellent separation effect on heavy rare earth impurities under preferred conditions.

[0044] Example 7 An innovative method for scandium recovery based on scandium double salt precipitation of organic sulfonic acid is described in the following steps: This embodiment is used to examine the separation effect on conventional metal impurities under the preferred conditions of Example 1. Sc[(S)-CSA]3 is prepared according to the method of Example 1, and double salt precipitation is carried out using saturated Na2SO4 solution at a solid-liquid ratio of 1:6 (g / mL).

[0045] Analysis of the precipitate and liquid phase showed that the system has a good repulsion effect on common metal impurities such as Fe, Al, Ni and Mn. The removal rates of Fe and Al both exceeded 90%, and the removal rates of Ni and Mn both exceeded 95%.

[0046] According to the formula, the separation factors of scandium from Fe, Al, Ni, and Mn are 98.76, 99.97, 876.92, and 786.04, respectively. The results show that the complex salt precipitation system of this invention can not only efficiently separate rare earth impurities but also effectively remove various conventional metal impurities.

[0047] Example 8 An innovative method for scandium recovery based on scandium double salt precipitation of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that in step (3), Sc(OTf)3 is prepared by trifluoromethanesulfonic acid; in step (4), saturated Na2SO4 solution is used for double salt precipitation, and the solid-liquid ratio is 1:3 (g / mL).

[0048] Specifically, 1.00 g of Sc(OTf)3 was weighed, added to 3.0 mL of saturated Na2SO4 solution, stirred and mixed, and allowed to stand until precipitation was complete. The mixture was then filtered and dried to obtain a double salt precipitate.

[0049] In this embodiment, the scandium recovery rate in the double salt precipitation step was 83.55%. The results show that scandium trifluoromethanesulfonate can form scandium-containing double salt precipitate with Na2SO4, but its scandium recovery rate and separation performance are lower than those of the Sc[(S)-CSA]3 / Na2SO4 system in Example 1.

[0050] Example 9 An innovative method for scandium recovery based on scandium double salt precipitation of organic sulfonic acid is as follows: The steps of the method are as follows: The difference between this embodiment and Example 1 is that p-toluenesulfonic acid is used to prepare Sc(OTs)3 in step (3); and saturated Na2SO4 solution is used for double salt precipitation in step (4), with a solid-liquid ratio of 1:3 (g / mL).

[0051] Specifically, 1.00 g of Sc(OTs)3 was weighed, added to 3.0 mL of saturated Na2SO4 solution, stirred and mixed, and allowed to stand until precipitation was complete. The mixture was then filtered and dried to obtain a double salt precipitate.

[0052] In this embodiment, the scandium recovery rate in the double salt precipitation step was 54.47%. The results indicate that although scandium p-toluenesulfonate can form a precipitate with Na2SO4, the proportion of scandium entering the solid phase is low, and the overall effect is significantly weaker than that of the camphorsulfonate scandium system. Example 10 An innovative method for scandium recovery based on scandium sulfonate double salt precipitation is described below. The method comprises the following steps: This embodiment is used to further verify the effect of different double salt precipitants on the camphor sulfonate scandium salt system. Sc[(S)-CSA]3 was prepared according to the method in Example 1. Under a solid-liquid ratio of 1:6 (g / mL), a saturated K2SO4 solution was used instead of a saturated Na2SO4 solution for double salt precipitation.

[0053] Specifically, 1.00 g of Sc[(S)-CSA]3 was weighed, added to 6.0 mL of saturated K2SO4 solution, stirred and mixed, and allowed to stand until precipitation was complete. The mixture was then filtered and dried to obtain a scandium-containing double salt precipitate.

[0054] In this embodiment, the scandium recovery rate of the double salt precipitation step was 66.74%, and the removal effect on some rare earth impurities was significantly lower than that when Na2SO4 was used. This indicates that in the organic sulfonate scandium salt system of the present invention, Na2SO4 is more conducive to the formation of scandium-containing double salt precipitates with stronger selectivity and higher recovery rate than K2SO4.

[0055] This invention is the first to combine organic sulfonic acid scandium salts with sulfates to construct a novel double salt precipitation system. The mechanism involves the combination of organic sulfonic acid (such as camphor sulfonic acid) and Scandium (Sc)... 3+ Coordination forms insoluble scandium organic sulfonate salts; upon addition of saturated sulfate, insoluble scandium-containing complex salt precipitates are formed, while rare earth and conventional metal impurities remain in the liquid phase, achieving efficient separation in one step.

[0056] Although embodiments and drawings of the present invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for scandium recovery based on the precipitation of scandium double salts of organic sulfonic acids, characterized in that: The steps of the method are as follows: S1. The scandium concentrate is subjected to acid leaching with sulfuric acid to obtain a scandium-containing leachate; S2. Adjust the pH of the scandium-containing leachate to alkaline, and precipitate crude scandium hydroxide (Sc(OH)3). S3. Crude scandium hydroxide is reacted with organic sulfonic acid to prepare scandium salts of organic sulfonic acid; S4. The scandium salt of organic sulfonate is mixed with a saturated sulfate solution in a certain proportion to carry out double salt precipitation, and the scandium-containing double salt is obtained by separation. S5. The scandium-containing complex salt is washed, precipitated with ammonia, dissolved in acid, precipitated with oxalate, and calcined at high temperature to obtain high-purity scandium oxide.

2. The method for recovering scandium based on the precipitation of scandium complex salts with organic sulfonates according to claim 1, characterized in that: The concentration of the S1 sulfuric acid is 5% to 30%; the acid leaching temperature is 80 to 120°C; the leaching time is 2 to 4 hours; and the solid-liquid ratio of the scandium concentrate to the sulfuric acid is 1:10 to 1:30 (g / mL).

3. The method for recovering scandium based on the precipitation of scandium complex salts with organic sulfonates according to claim 1, characterized in that: In step S2, the pH of the scandium-containing leachate is adjusted to 7-9 using a sodium hydroxide solution.

4. The method for recovering scandium based on the precipitation of scandium complex salts with organic sulfonates according to claim 1, characterized in that: The organic sulfonic acid in S3 is any one of (S)-(+)-camphor-10-sulfonic acid, (R)-(-)-camphor-10-sulfonic acid, naphthalene-2-sulfonic acid, trifluoromethanesulfonic acid, or p-toluenesulfonic acid.

5. The method for recovering scandium based on the precipitation of scandium complex salts of organic sulfonates according to claim 1, characterized in that: The saturated sulfate of S4 is any one of sodium sulfate (Na2SO4), potassium sulfate (K2SO4), ammonium sulfate ((NH4)2SO4), lithium sulfate (Li2SO4), magnesium sulfate (MgSO4), or calcium sulfate (CaSO4).

6. The method for recovering scandium based on the precipitation of scandium complex salts of organic sulfonates according to claim 1, characterized in that: The solid-liquid ratio of the S4 organic scandium sulfonate salt to the saturated sulfate solution is 1:3 to 1:15 (g / mL).

7. The method for recovering scandium based on the precipitation of scandium complex salts of organic sulfonates according to claim 1, characterized in that: The ammonia concentration used in the S5 ammonia treatment is 5%–15%, and the washing water is ultrapure water; the oxalic acid concentration used for oxalate precipitation is 0.5–2 mol / L; the calcination temperature is 800–900℃, and the calcination time is 1–2 h.

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