Method for selective separation of scandium and rare earths in a sulphuric acid leach

Abstract

The present application belongs to the field of hydrometallurgy, and specifically designs a method for selective separation of scandium and rare earth in sulfuric acid leaching solution. A certain amount of sodium / potassium-based regulator is added to the sulfuric acid leaching solution containing scandium and other rare earth ions, and the solution is pretreated and kept at 35-55 DEG C for at least 10 minutes. Then, a certain amount of sodium / potassium-based regulator is added or not added, and the solution is heated to 70-90 DEG C and controlled at pH 0-1. Subsequently, solid-liquid separation is performed to obtain a scandium-containing solution and a difficultly soluble sodium / potassium rare earth sulfate double salt. Then, the scandium is purified by using extraction method in a strong acid environment. In the present application, under the action of the sodium / potassium-based regulator, the temperature and pH can realize efficient synergistic effect, so as to achieve the purpose of sodium / potassium of rare earth, effectively realize the fine separation and distribution recovery of scandium and rare earth in the sulfuric acid leaching solution, improve the purity of scandium product and rare earth product, reduce the production cost, and reduce the environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to the selective separation of scandium and rare earth elements in sulfuric acid leaching solutions. Background Technology

[0002] Scandium (Sc), as a typical rare earth element, is valued for its unique electronic configuration ([Ar]3d). 1 4s 2 Rare earth elements (La, Ce, Pr, Nd, etc.) possess excellent high-temperature stability, electrical conductivity, and catalytic activity, making them widely used in aerospace high-temperature alloys, high-end semiconductor materials, new energy battery electrode materials, and laser devices. These rare earth elements are also widely used in permanent magnet materials, catalytic hydrogenation, optical glass, and rare earth polishing powders, resulting in a huge market demand.

[0003] Currently, scandium is typically extracted as a byproduct in metallurgical processes involving minerals such as red mud (a byproduct of smelting ilmenite, laterite, bauxite), and rare earth minerals. The scandium content in these minerals is usually low and closely associated with other rare earth elements, with scandium content ranging from only 0.001% to 0.01%. At the same time, it is accompanied by a large number of impurity ions such as iron, aluminum, and magnesium. The impurity content can be hundreds to thousands of times higher than that of scandium and rare earth elements (the impurities are at the g / L level, while scandium and rare earth elements are only at the mg / L level). This makes it extremely difficult to separate and purify scandium from other rare earth elements in wet leaching systems. Laterite nickel ore, a globally important carrier of nickel resources, contains not only scandium and rare earth elements in its sulfuric acid leaching solution, but also large amounts of magnesium and iron ions, further complicating separation. Red mud, a major byproduct of bauxite smelting, has extremely high aluminum content in its sulfuric acid leaching solution, easily forming co-precipitates with scandium and other rare earth elements. Fly ash, a waste product from coal-fired power generation, while containing relatively low levels of scandium and other rare earth elements, is tightly mixed with them and has complex impurities, also hindering separation. In minerals such as ilmenite and monazite, scandium is more firmly bonded to other rare earth elements, making it difficult to break this bond using conventional separation methods, resulting in ineffective resource recovery. In these common scandium- and rare earth-containing minerals, scandium often substitutes for rare earth ions such as La and Ce in an isomorphous manner, embedding itself in the ore lattice; the ionic radii of the two are similar (Sc). 3+ Radius 0.0745 nm, La 3+ (Radius 0.1032 nm) and have highly similar chemical properties, they will dissolve simultaneously into the leachate during sulfuric acid leaching.

[0004] In the current hydrometallurgical industry, the separation process of scandium from other rare earth elements in sulfuric acid leaching solutions mostly adopts traditional precipitation or solvent extraction methods. These methods cannot effectively break the doping state of scandium with other rare earth ions, and generally suffer from insufficient technical targeting, resulting in low separation efficiency and low resource recovery rate, which makes it difficult to meet the needs of industrial-scale production and high-end product applications.

[0005] Based on the aforementioned pain points in the hydrometallurgical industry, and considering the differences in the occurrence forms and thermodynamic properties of scandium and rare earth elements in the sulfuric acid leaching system, it is necessary to develop an efficient, environmentally friendly, and industrially suitable selective separation method to achieve efficient separation and high-value recovery of scandium from other rare earth elements. The patent application CN202610336796.0, entitled "A Method for Selective Leaching of Scandium from Rare Earth Iron-Rich Minerals," adds sodium salt before roasting, thereby activating scandium to dissolve in acid during the leaching process, inhibiting the dissolution of other rare earth elements, and forming an active precursor of rare earth complex salts. This achieves efficient leaching of scandium (leaching rate > 90%) and effective inhibition of other rare earth elements (leaching rate < 5%). However, due to limited control during the leaching process, the separation of scandium from other rare earth elements is not complete, and a certain concentration of rare earth ions still remains in the leachate, requiring further separation from scandium. Summary of the Invention

[0006] Based on the patent "A Method for Selective Leaching of Scandium from Rare Earth Iron-Rich Minerals", this invention transforms the approach by using the above-mentioned sulfuric acid leaching solutions containing scandium and rare earth elements as raw materials. It further introduces M-based regulators into the liquid phase environment to retain Sc in the solution as much as possible and to precipitate other elements as much as possible. This achieves efficient and precise separation of Sc and other rare earth elements and simultaneously purifies the Sc-containing liquid.

[0007] The present invention discloses a method for selectively separating scandium and rare earth elements in a sulfuric acid leaching solution, comprising: adding an M-based regulator to a sulfuric acid leaching solution containing scandium and other rare earth elements, pre-treating at 35-55 °C for at least 10 min, then raising the temperature to 70-90 °C and controlling the pH to 0-2, reacting, and then separating the solid and liquid components to obtain a scandium-containing solution and other rare earth precipitates;

[0008] Alternatively, a first part of M-based regulator is added to a sulfuric acid leaching solution containing scandium and other rare earth elements, and the solution is pretreated at 35-55 °C for at least 10 min. Then, the temperature is raised to 70-90 °C and the pH is controlled at 0-2 before adding a second part of M-based regulator. The reaction is carried out, followed by solid-liquid separation to obtain a scandium-containing solution and other rare earth precipitates. The M-ion content in the first part of the M-based regulator is 0.1-0.7 times, preferably 0.3-0.5 times, and more preferably 0.3-0.4 times, of the total M-ion content in the added M-based regulator.

[0009] The M-based regulator provides sodium and / or potassium ions; the total amount of M-based regulator added is 1.2 to 1.5 times the total molar amount of other rare earth elements.

[0010] In the sulfuric acid leachate, the scandium content is greater than or equal to 30 mg / L, preferably greater than or equal to 50 mg / L, and the total content of other rare earth elements is greater than the scandium content, preferably greater than or equal to 0.1 g / L, and more preferably greater than or equal to 0.2 g / L.

[0011] In the sulfuric acid leachate, the content of other metal ions is greater than 10 times, preferably greater than 100 times, the content of scandium. The other metals are selected from at least two of Fe, Al, Mg, Ti, and Ca.

[0012] This invention discloses a method for the selective separation of scandium and rare earth elements in sulfuric acid leachate, wherein the M-based regulator is selected from at least one of sodium sulfate, sodium bisulfate, sodium carbonate, sodium bicarbonate, sodium chloride, sodium nitrate, sodium sulfite, sodium pyrosulfate, sodium acetate, sodium formate, sodium citrate, potassium sulfate, potassium bisulfate, potassium chloride, potassium nitrate, potassium pyrosulfate, potassium acetate, potassium formate, and potassium citrate.

[0013] The present invention discloses a method for selectively separating scandium and rare earth elements in a sulfuric acid leachate, wherein the sulfuric acid leachate containing scandium and other rare earth elements also contains Q ions, wherein the Q ions include at least one of ferric ions, ferrous ions, aluminum ions, magnesium ions, titanium ions, and calcium ions.

[0014] Preferably, the concentration of Q ions in the sulfuric acid leachate containing scandium and other rare earth elements is greater than the concentration of Sc ions. More preferably, the concentration of Q ions is more than 10 times the concentration of Sc ions.

[0015] This invention discloses a method for the selective separation of scandium and rare earth elements in sulfuric acid leaching solution, wherein an M-based regulator is added to the sulfuric acid leaching solution at a molar ratio of M / rare earth = 1.2~1.3.

[0016] In this invention, the stepwise addition of the M-based regulator is a preferred embodiment. In this preferred embodiment, a portion of the M-based regulator is first added and reacted at a lower temperature to obtain fine particles of other rare earth precipitates with a large specific surface area. This allows for the adsorption of as many other metal ions, such as Q ions, as possible. Since the concentration of Q ions is much greater than that of Sc ions, the adsorption competitiveness of Q ions is much greater than that of Sc during the adsorption process, thus ensuring that as much Sc remains in the liquid as possible. Then, the temperature is raised to 70-90 °C and the pH is controlled at 0-2 before adding the second portion of the M-based regulator. At this point, the appropriately higher temperature combined with a suitable amount of the second portion of the M-based regulator enables a dynamic precipitation-dissolution process, resulting in highly active newly formed precipitates. This not only increases the aggregation of the precipitates but also ensures their adsorption of other metal ions. Furthermore, the final precipitate exhibits a loose state, which facilitates the subsequent separation of the adsorbed other metal ions from the other rare earth precipitates through simple operations (such as water washing or drying, crushing, and washing).

[0017] Preferably, the pretreatment is carried out at 35~55 ℃ for 10 min~60 min, more preferably 10 min~40 min, which of course includes 10 min~30 min.

[0018] Preferably, the temperature is raised to 70-90°C and the pH is controlled at 0-1; and the temperature is maintained at this temperature for at least 5 min, more preferably 5-180 min, and even more preferably 30-120 min.

[0019] The scandium-containing solution obtained in this invention is purified by extraction.

[0020] This invention utilizes the separation properties of scandium and rare earth elements. By adding an M-based regulator to the leachate containing scandium and rare earth elements, the separation of scandium and rare earth elements is further enhanced, achieving excellent results in retaining activated scandium in the liquid phase and converting precipitated rare earth elements into insoluble rare earth complex salts. Furthermore, regardless of whether the minerals have undergone a roasting stage, the method described in this invention can achieve highly efficient and precise separation of scandium and rare earth ions (scandium retention rate > 99%, rare earth precipitation rate > 99%) by adding the M-based regulator to almost all liquids containing scandium and rare earth elements, and can also improve the purity of Sc-containing solutions.

[0021] This invention has found that the separation of scandium and rare earth elements in sulfuric acid leaching solutions is difficult and requires coordinated control of reaction temperature, pH, and reaction time. This can facilitate the sodium or potassium formation of rare earth elements, such as forming sodium rare earth sulfate double salts (NaRE(SO4)2·xH2O, x=0~4) with sodium ions. This enables highly efficient and selective separation of scandium and rare earth elements, improves resource recovery rate and product purity, reduces production costs, and reduces environmental pollution.

[0022] This invention utilizes the difference in reaction behavior between scandium and rare earth elements in sulfuric acid leaching solutions. Under normal temperature and pressure, an M-based regulator is introduced into the sulfuric acid leaching solution containing scandium and rare earth elements. Due to the high radius matching and strong lattice compatibility between M ions and rare earth ions in the system, they can spontaneously construct thermodynamically stable rare earth sulfate M double salt lattices with sulfate ions and preferentially precipitate out. This promotes the combination of rare earth elements with M-based regulators and sulfate ions to form insoluble M rare earth sulfate double salts (RE2(SO4)3·M2SO4·xH2O), resulting in precipitation.

[0023] This invention selects ambient temperature and pressure conditions for controlled separation. Under these conditions, rare earth ions in the leachate can spontaneously form rare earth sulfate complex anions with sulfate ions. Sodium / potassium ions in the system further match the charge and lattice of these complex anions, spontaneously forming rare earth sodium sulfate double salt with extremely low solubility and precipitating out as a precipitate. This process is spontaneously driven by ion coordination and lattice thermodynamics, without the need for high temperature and high pressure to provide reaction activation energy. On the contrary, under high temperature and high pressure, the lattice thermal stability of the rare earth double salt decreases and its solubility increases sharply, and the originally precipitated rare earth will redissolve into the liquid.

[0024] In the preferred embodiment of this invention, the formed rare earth sulfate double salt crystal structure is complete. By performing solid-liquid separation on the obtained system, only conventional filtration is required to collect the scandium-containing solution and the sodium rare earth sulfate double salt precipitate separately. No complex parameter control is needed; it is only necessary to ensure that there is no obvious slag entrainment in the liquid, thus simplifying the process and reducing operational difficulty. Subsequently, scandium products and rare earth products are prepared using extraction, precipitation, and other methods.

[0025] Beneficial effects

[0026] 1. This invention innovatively adds a sodium / potassium-based regulator to the sulfuric acid leaching solution at room temperature and pressure, thereby sodium / potassium-ionizing other rare earth ions and promoting their transformation into insoluble sodium / potassium rare earth sulfate double salts, achieving the effect of selective separation of scandium and rare earths.

[0027] 2. In this invention, the sulfuric acid leachate and sodium / potassium-based regulator are first pretreated at a lower temperature; then the temperature is raised to a higher temperature for reaction, so that scandium is retained in the scandium-containing solution as much as possible, and other rare earth elements are precipitated out as much as possible in the form of sparingly soluble sodium / potassium rare earth sulfate double salts.

[0028] 3. The sodium / potassium-based regulator of the present invention is added in two stages: a suitable amount of sodium / potassium-based regulator is added during the low-temperature pretreatment stage, and then a suitable amount of sodium / potassium-based regulator is added to react at a higher temperature. This ensures that as much scandium as possible remains in the scandium-containing solution and that as much of the other rare earth elements as possible precipitates out in the form of insoluble sodium / potassium rare earth sulfate double salts, while reducing the content of impurity elements in the scandium-containing solution.

[0029] 4. The reaction in this invention is carried out in a strong acid environment, and the scandium-containing solution can be purified and separated by extraction. Attached Figure Description

[0030] Figure 1 To explore the XRD pattern of the sparingly soluble sodium rare earth sulfate double salt obtained in Example 1.

[0031] Figure 2 Scanning electron microscope image of the sparingly soluble sodium rare earth sulfate double salt obtained in Example 1.

[0032] from Figure 1 , Figure 2 As can be seen from this, except for scandium, rare earth Ce is sodium-treated to form insoluble rare earth complex salts. Detailed Implementation

[0033] To further clarify and fully illustrate the technical solution of the present invention, the present invention will be further described in detail below with reference to specific embodiments and exploratory examples. The following embodiments and exploratory examples are only used to exemplify the technical principles, implementation methods and technical effects of the present invention, and are not intended to limit the scope of protection of the present invention; the application scenarios, implementation scale and process parameters of the present invention are not limited by the experimental scale and specific data disclosed in the following embodiments and exploratory examples.

[0034] Exploration Example 1

[0035] A binary simulated leaching solution (Sc 80 mg / L, Ce 240 mg / L) was prepared, and a sodium-based regulator (sodium sulfate) was added at a sodium / rare earth (cerium) molar ratio of 1.2. The solution was first pretreated at 40 °C for 30 min, followed by stirring at 90 °C and pH 0.5 for 60 min to obtain a scandium-containing solution and a sparingly soluble sodium rare earth sulfate complex salt (NaRE(SO4)2·xH2O). The mixture was then subjected to solid-liquid separation, and the scandium-containing solution and the sparingly soluble sodium rare earth sulfate complex salt were collected separately.

[0036] The results showed that the scandium retention rate in the scandium-containing solution was 98.25%~98.75%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was about 98%, achieving efficient pre-separation of scandium and cerium.

[0037] Exploration Example 2

[0038] Compared to Exploratory Example 1, the only difference is that this Exploratory Example adds a sodium-based regulator (sodium sulfate) at a sodium / rare earth molar ratio of 2; the remaining steps are completely identical to Exploratory Example 1. After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98.5%–99%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was approximately 98%, achieving efficient pre-separation of scandium and cerium.

[0039] Exploration Example 3

[0040] Compared to Exploratory Example 1, the only difference is that the temperature of the two-stage reaction is controlled in this Exploratory Example as follows:

[0041] Group A experiment: The temperature of the two-stage reaction was controlled at 70 ℃. The scandium retention rate in the scandium-containing solution obtained after the experiment was 95%~96%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was about 96%, which basically achieved the separation of scandium and cerium.

[0042] Group B experiment: The temperature of the two-stage reaction was controlled at 80 ℃. The scandium retention rate in the scandium-containing solution obtained after the experiment was 97%~97.5%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was about 95%, which basically achieved the separation of scandium and cerium.

[0043] Group C experiment: The two-stage reaction temperature was controlled at 100 ℃. The scandium retention rate in the obtained scandium-containing solution was 98%~98.5%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was approximately 96%.

[0044] Exploration Example 4

[0045] Compared to Exploratory Example 1, the only difference is that this exploratory example used a binary simulated leachate (Sc 80 mg / L, Nd 200 mg / L) as the raw material, while other conditions were the same as in Exploratory Example 1. After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98%–99%, and the neodymium precipitation rate in the sparingly soluble sodium-neodymium sulfate double salt was approximately 97%.

[0046] Exploration Example 5

[0047] Compared to Exploratory Example 1, the only difference is that this exploratory example used a binary simulated leachate (Sc 80 mg / L, La 200 mg / L) as the raw material, while other conditions were the same as in Exploratory Example 1. After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98.5%~99.5%, and the lanthanum precipitation rate in the sparingly soluble sodium lanthanum sulfate double salt was approximately 97%.

[0048] Exploration Example 6

[0049] Compared to Exploratory Example 1, the only difference is that this exploratory example used a binary simulated leachate (Sc 80 mg / L, Y 160 mg / L) as the raw material, while other conditions were the same as in Exploratory Example 1. After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98.5%–99%, and the yttrium precipitation rate in the sparingly soluble sodium yttrium sulfate double salt was approximately 96%.

[0050] Exploration Example 7

[0051] Compared to Exploratory Example 1, the only difference is that this exploratory example used a ternary simulated leachate (Sc 80 mg / L, La 200 mg / L, Ce 240 mg / L) as the raw material; all other conditions were the same as in Exploratory Example 1. After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98%–98.5%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 96%.

[0052] Exploration Example 8

[0053] Compared to Exploratory Example 1, the only difference in this Exploratory Example is that the sulfuric acid leaching solution of ilmenite was used (the concentrations of the main components in the leaching solution were: Sc 80 mg / L, total iron 12.6 g / L, Al...). 3+ 4.8 g / L, Mg 2+ 2.1 g / L, Na + 0.3 g / L, Ca 2+(0.5 g / L, total rare earth element concentration of 1.2 g / L). After the experiment, the scandium retention rate in the scandium-containing solution was measured to be 98%–99%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 98%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 79.0 mg / L, total iron 1.2 g / L, and Al... 3+ 0.7 g / L, Mg 2+ 0.2g / L, Na + 0.05g / L, Ca 2+ 0.05 g / L, and the total amount of other rare earth elements is 0.022 g / L.

[0054] Example 1

[0055] The other conditions are the same as in Example 8, except that:

[0056] Sodium-based regulator (sodium sulfate) was prepared according to a sodium / rare earth molar ratio of 1.2 and divided into two portions with a molar ratio of 1 to 1. The first portion of sodium sulfate was added first, and the mixture was pretreated at 40 °C for 30 min. Then, the second portion of sodium sulfate was added, the temperature was raised to 90 °C, and the pH of the system was controlled at 0.5. The mixture was stirred at 90 °C for 60 min to obtain a scandium-containing solution and a sparingly soluble sodium rare earth sulfate complex salt (NaRE(SO4)2·xH2O). The mixture was then subjected to solid-liquid separation, and the scandium-containing solution and the sparingly soluble sodium rare earth sulfate complex salt were collected separately. The results showed that the scandium retention rate in the scandium-containing solution was 99%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate complex salt was approximately 98%, achieving efficient pre-separation of rare earth elements and scandium. The obtained scandium-containing solution contained 79.2 mg / L Sc, 0.5 g / L total iron, and Al... 3+ 0.06 g / L, Mg 2+ 0.01 g / L, Na + 0.006 g / L, Ca 2+ 0.008 g / L. By comparing Example 1 and Exploratory Example 8, it was found that the content of impurity elements in the obtained scandium-containing solution had decreased significantly. This provides the necessary conditions for the efficient extraction of the scandium-containing solution and the recycling of the extractant, and also provides the necessary conditions for obtaining high-purity or ultra-high-purity Sc.

[0057] Example 2

[0058] All other conditions are the same as in Example 1, except that:

[0059] The molar ratio of the first portion to the second portion is 0.5.

[0060] The experiment showed that the scandium retention rate in the scandium-containing solution was 99%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 99%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 79.2 mg / L, total iron 0.02 g / L, and Al... 3+ 0.01g / L, Mg 2+ 0.005 g / L, Na + 0.003 g / L, Ca 2+ 0.004 g / L.

[0061] Example 3

[0062] All other conditions are the same as in Example 1, except that:

[0063] The molar ratio of the first portion to the second portion is 2.

[0064] The experiment showed that the scandium retention rate in the scandium-containing solution was 98%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 98%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 78.9 mg / L, total iron 0.7 g / L, and Al... 3+ 0.06 g / L, Mg 2+ 0.01 g / L, Na + 0.01 g / L, Ca 2+ 0.009 g / L.

[0065] Example 4

[0066] All other conditions are the same as in Example 1, except that:

[0067] After adding the first portion of sodium sulfate, pre-treat at a constant temperature for 10 minutes.

[0068] The experiment showed that the scandium retention rate in the scandium-containing solution was 98%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 95%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 78.9 mg / L, total iron 0.7 g / L, and Al... 3+ 0.1 g / L, Mg 2+ 0.08 g / L, Na + 0.03 g / L, Ca 2+ 0.01 g / L.

[0069] Example 5

[0070] All other conditions are the same as in Example 1, except that:

[0071] After adding the second portion of sodium sulfate, stir the reaction mixture for 30 minutes.

[0072] The experiment showed that the scandium retention rate in the scandium-containing solution was 98%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 97%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 78.9 mg / L, total iron 0.6 g / L, and Al... 3+ 0.1 g / L, Mg 2+ 0.05 g / L, Na + 0.01 g / L, Ca 2+ 0.008 g / L.

[0073] Example 6

[0074] All other conditions are the same as in Example 1, except that:

[0075] After adding the second portion of sodium sulfate, stir the reaction for 90 minutes.

[0076] The experiment showed that the scandium retention rate in the scandium-containing solution was 97%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 97%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 77.7 mg / L, total iron 0.5 g / L, and Al... 3+ 0.08 g / L, Mg 2+ 0.05 g / L, Na + 0.005 g / L, Ca 2+ 0.008 g / L.

[0077] Example 7

[0078] All other conditions are the same as in Example 1, except that:

[0079] After adding the second portion of sodium sulfate, the mixture was stirred at 80 °C to react.

[0080] The experiment showed that the scandium retention rate in the scandium-containing solution was 98%, and the rare earth precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was approximately 97%, achieving efficient pre-separation of rare earth elements and scandium. The resulting scandium-containing solution contained Sc 78.8 mg / L, total iron 0.6 g / L, and Al... 3+ 0.2 g / L, Mg 2+ 0.1 g / L, Na + 0.05 g / L, Ca 2+ 0.009 g / L.

[0081] Comparative Example 1

[0082] The only difference from Exploratory Example 1 is that no sodium-based regulator mediated pre-separation was performed, and extraction separation was carried out directly. Because no sodium-based regulator was used, cerium could not form a complex salt precipitate and entered the leachate simultaneously with scandium, significantly increasing the load on the subsequent extraction system. Furthermore, rare earth elements could not be recovered simultaneously, resulting in low resource utilization.

[0083] Comparative Example 2

[0084] Compared to Exploratory Example 1, the only difference is that a sodium-based regulator (sodium sulfate) is added at a sodium / rare earth molar ratio of 0.8; the remaining steps are completely identical to Exploratory Example 1. Due to insufficient addition of the sodium-based regulator, it is impossible to fully provide Na. + The scandium-containing solution could not completely form a sparingly soluble sodium rare earth sulfate complex salt. The scandium retention rate in the scandium-containing solution was approximately 98%, while the cerium precipitation rate was 86%. Cerium did not completely enter the sparingly soluble complex salt, and the separation effect between scandium and cerium was not satisfactory.

[0085] Comparative Example 3

[0086] The only difference from Exploratory Example 1 is that the 30-minute pretreatment at 40 °C was omitted. Instead, the sodium-based regulator (sodium sulfate) was directly added to the leachate, and the mixture was stirred for 60 minutes at a reaction temperature of 80 °C and a pH of 0.5. The results showed that the scandium retention rate in the scandium-containing solution was approximately 94%, while the cerium precipitation rate in the sparingly soluble sodium rare earth sulfate double salt was only 78%. Because the 40 °C pretreatment was not performed, the coordination reaction between the sodium salt and cerium was insufficient, resulting in a slow double salt formation rate, incomplete crystallization, and some unprecipitated cerium remaining in the scandium-containing solution.

[0087] Comparative Example 4

[0088] The only difference from Exploratory Example 1 was that the temperature of the subsequent two-stage reaction was adjusted to 60 °C. The results showed that the scandium retention rate in the scandium-containing solution was approximately 95.5%, and the cerium precipitation rate in the sparingly soluble sodium-cerium sulfate double salt was 85%. The reaction temperature was too low, which led to a significant decrease in the reaction rate of cerium with sodium salt and sulfate to form a double salt, an increase in the solubility of the double salt, and the inability of some cerium to precipitate. Moreover, the precipitate crystals were not dense and contained a small amount of scandium ions.

[0089] Comparative Example 5

[0090] The only difference from Exploratory Example 1 was that the reaction pH was adjusted to 2.5. The experimental results showed that the scandium retention rate in the scandium-containing solution was approximately 93%, and the cerium precipitation rate in the sparingly soluble sodium cerium sulfate double salt was 75%. The reaction pH was too high, leading to an increase in H+ in the solution. + The concentration decreases, disrupting the acidic environment for the formation of double salts.

Claims

1. A method for the selective separation of scandium and rare earth elements in sulfuric acid leachate, characterized in that: M-based regulator was added to the sulfuric acid leachate containing scandium and other rare earth elements, and the solution was pretreated at 35-55 °C for at least 10 min. Then the temperature was raised to 70-90 °C and the pH was controlled at 0-2. The reaction was carried out, followed by solid-liquid separation to obtain the scandium-containing solution and other rare earth precipitates. Alternatively, a first part of the M-based regulator can be added to a sulfuric acid leachate containing scandium and other rare earth elements, and the solution can be pretreated at 35-55 °C for at least 10 min. Then, the temperature can be raised to 70-90 °C and the pH can be controlled at 0-2. The second part of the M-based regulator can then be added, and the reaction can be carried out. Subsequently, solid-liquid separation is performed to obtain a scandium-containing solution and other rare earth precipitates. The M ions in the first part of the M-based regulator account for 0.1-0.7 times the M ions in the added M-based regulator. The M-based regulator provides sodium and / or potassium ions; the total amount of M-based regulator added is 1.2 to 1.5 times the total molar amount of other rare earth elements.

2. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 1, characterized in that: The sulfuric acid leachate contains scandium content greater than or equal to 30 mg / L, and the total content of other rare earth elements is greater than the scandium content.

3. The method for selective separation of scandium and rare earth elements in sulfuric acid leaching solution according to claim 1, characterized in that: The sulfuric acid leachate contains other metal ions at a concentration greater than 10 times that of scandium, and the other metals include at least two of Fe, Al, Mg, Ti, and Ca.

4. The method for selective separation of scandium and rare earth elements in sulfuric acid leaching solution according to claim 1, characterized in that: The M-based regulator is selected from at least one of sodium sulfate, sodium bisulfate, sodium carbonate, sodium bicarbonate, sodium chloride, sodium nitrate, sodium sulfite, sodium pyrosulfate, sodium acetate, sodium formate, sodium citrate, potassium sulfate, potassium bisulfate, potassium chloride, potassium nitrate, potassium pyrosulfate, potassium acetate, potassium formate, and potassium citrate.

5. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 1, characterized in that: The sulfuric acid leachate containing scandium and other rare earth elements also contains at least two of the following ions: ferrous ions, ferrous ions, aluminum ions, magnesium ions, and calcium ions.

6. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 1, characterized in that: M-based regulators were added to the sulfuric acid leachate at a sodium / rare earth molar ratio of 1.2 to 1.

3.

7. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 1, characterized in that: Heat to 70-90℃ and control the pH to 0-1; and keep at this temperature for at least 5 minutes.

8. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 7, characterized in that: The heat preservation time is 5~180 minutes.

9. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 8, characterized in that: The heat preservation time is 30~120 minutes.

10. The method for selective separation of scandium and rare earth elements in sulfuric acid leachate according to claim 8, characterized in that: Scandium-containing solutions are purified through extraction.

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