Method for producing high-purity scandium oxide from interphase dirt generated by P204 extraction in nickel-cobalt metallurgy

Abstract

The invention belongs to the technical field of scandium extraction, and particularly relates to a method for producing high-purity scandium oxide from interphase dirt generated by P204 extraction in nickel-cobalt metallurgy, which comprises the steps of pretreatment of interphase dirt, impurity washing, scandium and zirconium reverse extraction, scandium oxalate production and scandium oxide production. The scandium oxide with high purity and high yield can be prepared by the method provided by the invention.

Description

Technical Field

[0001] The present invention belongs to the technical field of scandium extraction, and particularly relates to a method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy. Background Art

[0002] Scandium and its compounds have many excellent properties and are widely used in energy materials, superconductivity, electronic products, etc. The purity of scandium oxide has an important impact on the fields where it can be applied. At present, most of the scandium oxide produced in China has a low purity and cannot be directly applied to high-precision fields such as lasers and electric light sources, and needs to be further purified. However, in the existing technology, the scandium-containing raw materials are few (for example: smelting waste residue red mud, chlorination soot, industrial waste liquid titanium white waste acid, zirconium oxychloride crystallization mother liquor, etc.), the scandium content in the raw materials is low, the types of impurities are many, the separation and purification of scandium oxide are difficult, and the process is complex. These are the important reasons why the grade of the produced scandium oxide cannot meet the application requirements of high-end fields.

[0003] With the rapid development of new energy vehicles, nickel and cobalt at the raw material end have become important strategic resources. In the hydrometallurgy of nickel and cobalt, extraction technology is widely used due to its advantages such as high separation efficiency, good separation effect, low reagent consumption, and easy automation and continuousization in the production process. As a common extractant for impurity removal in the hydrometallurgy of nickel and cobalt, P204 is prone to generate interfacial dirt after long-term cyclic use. It is unevenly distributed between the aqueous phase and the organic phase, and its main components are usually: high-valent metal ion extraction complexes, inorganic silicates, colloidal iron hydroxide, colloidal aluminum hydroxide, suspended particles, etc. The main reason for its formation is that the extractant simultaneously extracts trace high-valent (+3 and above valence states) metal ions during the extraction process. It is difficult to completely separate these ions from the extractant through conventional acid-base washing or stripping processes after they are loaded into the organic phase. As a result, trace high-valent ions continuously accumulate in the organic phase until the high-valent metal ion extraction complexes in the organic phase reach supersaturation and precipitate, and then form flocculent or paste-like interfacial dirt with solid suspended substances, colloidal iron hydroxide, aluminum hydroxide, inorganic silicates, etc. in the solution. The existence of interfacial dirt will cause serious emulsification phenomena in the extraction process, resulting in entrainment loss of the extractant, difficulty in phase separation after extraction, decline in the extraction performance of the extractant, etc. In severe cases, production needs to be stopped for cleaning, which is not conducive to improving production efficiency.

[0004] In the prior art, although the generation rate of the interfacial dirt can be reduced through various means, it cannot be completely eliminated. Therefore, it is still necessary to regularly clean or treat the interfacial dirt, and its treatment method also varies depending on the specific composition of the interfacial dirt. For example, Patent No. CN202110575703.7 proposes a treatment method for interfacial dirt, which realizes the reuse of P204 by collecting and pre-treating the interfacial dirt, ethanol dispersion, alkali precipitation, and separating the mixed organic matter from the dispersant ethanol. It can be seen from the composition of the precipitate after calcination in the examples that there is a high content of scandium in the precipitate. However, there is no relevant literature in the prior art on how to extract high-purity and high-yield scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy.

[0005] Therefore, it is very necessary to research and develop a method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy. Summary of the Invention

[0006] The present invention aims to solve the above technical problems and provides a method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy. The scandium oxide obtained by this method has high purity and yield, and the content of impurities in the treated organic phase is low.

[0007] The technical solution of the present invention is as follows:

[0008] A method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy, comprising the following steps:

[0009] (1) Pretreatment: Add an active agent and a dispersant to the interfacial dirt in sequence, heat, stir and slurry, then heat up, keep warm and separate the solid and liquid to obtain iron-aluminum slag and dispersed interfacial dirt;

[0010] (2) Impurity washing: Add a detergent to the dispersed interfacial dirt for washing, separate the phases, wash with water, and separate the phases to obtain the organic phase after impurity washing and the washing solution;

[0011] (3) Scandium-zirconium back-extraction: Add a sodium carbonate solution to the organic phase after impurity washing for scandium-zirconium back-extraction, separate the phases to obtain a scandium-zirconium basic carbonate slurry and a P204 organic phase. The P204 organic phase is balanced with an inorganic acid and then returned to nickel-cobalt metallurgy extraction for use;

[0012] (4) Production of scandium oxalate: Add an ammonium carbonate solution to the scandium-zirconium basic carbonate slurry, stir and slurry, separate the solid and liquid to obtain a scandium-containing solution. Add oxalic acid to the scandium-containing solution for the first scandium precipitation, separate the solid and liquid to obtain scandium oxalate precipitate I and the solution after scandium precipitation I. Add an inorganic acid to the solution after scandium precipitation I for complexing dissociation, and then add oxalic acid for the second scandium precipitation, separate the solid and liquid to obtain scandium oxalate precipitate II and the solution after scandium precipitation II;

[0013] (5) Production of scandium oxide: Scandium oxalate precipitate I and scandium oxalate precipitate II are slurried with water, washed, dried, and calcined to obtain high-purity scandium oxide.

[0014] In order to disperse the interfacial contaminants and form a homogeneous single phase, during pretreatment, an active agent and a dispersant are added. Through the synergistic effect of the two, the interfacial contaminants are dispersed to form a homogeneous single phase. Preferably, in step (1) of the present invention, the active agent is a mixture of kerosene and sodium sulfate, and the dispersant is isopropyl alcohol. Among them, the mass ratio of sodium sulfate to kerosene in the active agent is 1-5:95-99, the volume concentration of the dispersant is 30-60%, the dosage of the active agent is 0.5-1.5 times the volume of the interfacial contaminants; the dosage of the dispersant is 3-6 times the volume of the interfacial contaminants. When the proportion of sodium sulfate in the active agent is too low / the dosage of the active agent is too small / the dosage of the dispersant is too small, the dispersion effect is poor, and a homogeneous single phase cannot be formed, but a heterogeneous paste is formed. The viscosity of the dispersed system is relatively large, which is not conducive to the subsequent impurity washing and the smooth progress of the scandium-zirconium stripping process. The impurity washing effect is poor, the scandium-zirconium stripping rate is low, and it is difficult to separate the aqueous phase and the organic phase by conventional phase separation methods after washing and after stripping scandium and zirconium. In addition, when the dosage of the active agent is too large or the proportion of sodium sulfate is too high, in order to achieve the same impurity washing effect, the washing process needs to be strengthened, otherwise the impurity washing effect is poor, so the production cost is easily increased. When the proportion of sodium sulfate is too high, the viscosity of the system is easily increased, which is not conducive to rapid phase separation.

[0015] During pretreatment, selecting an appropriate temperature can promote the synergistic effect of the activator and the dispersant, which is beneficial to the full dispersion of the interfacial dirt, and is also conducive to the smooth progress of subsequent washing of impurities and the stripping process of scandium and zirconium. When the temperature is too low, the dispersion effect of the interfacial dirt is poor, the viscosity of the dispersed system is relatively high, the subsequent impurity washing effect is poor, the stripping rates of scandium and zirconium are low, and it is difficult to separate the aqueous phase and the organic phase by conventional phase separation methods after washing and after stripping scandium. When the temperature is too high, it causes an increase in energy consumption and a poor working environment. In addition, some calcium sulfate crystals are wrapped in the interfacial dirt after dispersion to form stable droplets, which together with other dispersoids form a stable and homogeneous single phase. By heating up and combining with the common ion effect of sodium sulfate in the activator, the stability of calcium sulfate can be destroyed and it can be precipitated out in the form of a precipitate. When the temperature is too high after reheating, it is easy to cause the volatilization of the dispersant and a poor working environment. When the temperature is too low, calcium sulfate cannot be precipitated out. Under the conditions of appropriate temperature and appropriate dosage of sodium sulfate, the iron hydroxide colloid and aluminum hydroxide colloid in the original interfacial dirt are also precipitated together with the calcium sulfate precipitate. Through solid-liquid separation, the separation of impurities such as calcium, iron, and aluminum from the organic phase can be achieved. The obtained organic phase has a lower viscosity and a lower impurity content, which is beneficial to reducing the dosage of the detergent during subsequent impurity washing and is beneficial to the reuse of the organic phase in the extraction system (when iron, aluminum, etc. impurities are not removed in advance, calcium is not easily precipitated out during the washing process with hydrochloric acid and hydrogen peroxide, and the iron-aluminum colloid reacts with inorganic acids to consume acids, increasing the production cost). Preferably, in step (1) of the present invention, the temperature is raised to 55-65 °C and maintained for 0.5-2 h.

[0016] The concentration of hydrochloric acid in the detergent should not be too low, otherwise the washing effect of iron and aluminum will be poor. Nor should it be too high, otherwise some scandium will also be washed into the washing solution, reducing the recovery rate of scandium. The dosage of hydrogen peroxide should not be too low, otherwise the washing effect of titanium and chromium will be poor. If the dosage of hydrogen peroxide is too high, the production cost will be high. By washing impurities with a detergent of appropriate concentration, the iron, aluminum, titanium, and chromium loaded in the organic phase can be converted into their corresponding hydrochlorides and removed by phase separation. Then, the impurity ion hydrochlorides entrained are washed with water, and the impurities can be removed after phase separation. The loss of scandium during the washing process is small. After the treatment in step (2), the metal ions loaded in the organic phase are only scandium and zirconium, which is beneficial to improving the purity of the final scandium oxide product. In addition, reasonable temperature, time, number of stages, and phase ratio should be controlled during washing. When the temperature is too low, the phase separation after washing is slow, the contact between the detergent and the organic phase is insufficient, and the washing effect is poor. When the temperature is too high, the energy consumption is high. When the washing time is too short / the number of washing stages is too small / the phase ratio is too large, the washing effect of impurities is poor and the purity of the scandium oxide product is low. When the washing time is too long, it is not conducive to improving production efficiency. When the number of washing stages is too many / the phase ratio is too small, the amount of wastewater generated is large, which is not conducive to reducing the production cost. Preferably, in step (2) of the present invention, the detergent is a mixture of a 2-6N hydrochloric acid solution with a volume ratio of 90-95:5-10 and hydrogen peroxide with a mass concentration of 10-25%. The control conditions during washing are: temperature 40-60°C, time 10-30 min, the number of washing stages is 1-3, and the phase ratio is 1-3:1.

[0017] For the organic phase after washing impurities, by reacting with a sodium carbonate solution, the scandium and zirconium ion complexes in the organic phase can be converted into basic scandium carbonate precipitate and zirconium carbonate precipitate, which precipitate into the aqueous phase. The separation of the scandium and zirconium precipitate from the organic phase is achieved through phase separation. Since the filtration performance of the precipitate slurry is poor, after the scandium and zirconium back-extraction, phase separation is directly carried out without pressure filtration. The P204 organic phase obtained by phase separation is added with an inorganic acid (such as hydrochloric acid, sulfuric acid, with a mass concentration of 10-20% is sufficient) to balance the hydrogen ion concentration to reach 0.6-0.8 mol / L, and it can be returned to the extraction system for use. Preferably, in step (3) of the present invention, the concentration of the sodium carbonate solution is 10-30%, and the back-extraction conditions are: temperature 45-75°C, time 15-60 min, the number of back-extraction stages is 1-3, and the phase ratio is (1-2):1.

[0018] An appropriate dosage and concentration of ammonium carbonate can fully dissolve scandium basic carbonate, while zirconium carbonate is insoluble in ammonium carbonate solution. Therefore, scandium can be dissolved first and then separated from the solid and liquid, so as to achieve the separation of scandium and zirconium carbonates. Adding oxalic acid to the scandium-containing solution can convert scandium ions into scandium oxalate that is insoluble in water. The precipitation temperature should not be too high or too low. When the temperature is too low, the precipitation time is too short, or the dosage of oxalic acid is too small, the precipitation rate and recovery rate of scandium are low. When the temperature is too high, the energy consumption is high. When the precipitation time is too long, it is not conducive to improving production efficiency. When the dosage of oxalic acid is too large, the production cost increases. During the process of adding oxalic acid to precipitate scandium, impurity removal can also be achieved, that is, the remaining small amounts of iron and aluminum ions are completely separated from scandium. Since the ammonium carbonate solution introduces ammonium ions, some ammonium ions complex with scandium ions to form water-soluble complexes. Therefore, there are still small amounts of scandium complexes remaining in the solution after scandium precipitation. Therefore, an inorganic acid solution (such as hydrochloric acid or sulfuric acid, with a mass concentration of 10-20% is sufficient) needs to be added to the solution after scandium precipitation for complex dissociation, and then the precipitant oxalic acid is added for secondary precipitation. After solid-liquid separation, scandium oxalate precipitation is obtained to achieve the full recovery of scandium in the scandium-containing solution and improve the scandium recovery rate. Preferably, in step (4) of the present invention, the mass concentration of the ammonium carbonate solution is 10-15%, and the dosage of the ammonium carbonate solution is 1-3 times the volume of the scandium basic carbonate-zirconium slurry.

[0019] The scandium oxalate precipitate is slurried and washed with water to remove the impurity ions adsorbed and entrained on the surface of the precipitate, thereby improving the purity of the final scandium oxide product. Scandium oxalate can be decomposed into scandium oxide after drying and calcination. In step (4), the dosage of oxalic acid during the first scandium precipitation is 1.2-1.5 times the theoretical dosage, the precipitation temperature is 50-80°C, the time is 0.5-2 h, the pH is maintained at 1.5-3.0 during the precipitation process. The inorganic acid added during the second scandium precipitation is hydrochloric acid or sulfuric acid, the dosage of oxalic acid is 5-20% of the dosage during the first scandium precipitation, and the pH is maintained at 0.5-1.0 during the precipitation process.

[0020] In order to obtain ultra-high-purity scandium oxide, preferably, in the present invention, the scandium oxide obtained in step (5) is redissolved, impurity-removed and scandium-precipitated, washed, dried, and calcined to obtain ultra-high-purity scandium oxide. The inorganic acid used during redissolution is hydrochloric acid or sulfuric acid, the end-point pH is controlled at 0.5-1.5 during redissolution, oxalic acid is used as the precipitant during impurity-removing and scandium-precipitating, and the washing, drying, and calcination conditions are the same as those in step (5).

[0021] Due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0022] 1. The method of the present invention solves the problems in the prior art that scandium in the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy has not been effectively recovered and the impurities in the interfacial dirt have not been separated from scandium.

[0023] 2. By using the method of the present invention, scandium in the interphase contaminants can be separated from other impurities, and the purity of the produced scandium oxide product can reach 99.9%. After purification, ultra-high purity scandium oxide can be produced, with a purity of up to 99.99%.

[0024] 3. By using the method of the present invention, the recovery rate of scandium is high, reaching over 90%.

[0025] 4. By using the method of the present invention, the organic phase in the P204 interphase contaminants can be recovered. The produced organic phase can be continuously returned to the system for extraction use. The content of loaded impurities in the treated organic phase is low, and the period for generating interphase contaminants is extended when it is returned to the extraction system for use (for the P204 organic phase without treatment by the present invention or the organic phase returned for use after conventional treatment, the interphase contaminants generally need to be treated once every 1 - 2 months. After the organic phase is treated by the present invention and returned for use again, the interphase contaminants only need to be treated once every 6 months to ensure the efficient operation of the extraction system). Compared with the ordinary treatment method, when the organic phase treated by the present invention is returned for use again, the period for treating the interphase contaminants is extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the process flow chart of the method of the present invention.

[0027] Figure 2 is the high-purity scandium oxide prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1

[0030] (1) Pretreatment: Kerosene, sodium sulfate, and isopropanol are sequentially added to the interphase contaminants, heated to 45°C, stirred and slurried for 15 min, then heated to 60°C, held for 1 h, and then solid-liquid separated to obtain iron-aluminum slag and dispersed interphase contaminants; the mass ratio of sodium sulfate to kerosene is 1:99, and the total amount used is 0.5 times the volume of the interphase contaminants; the volume concentration of isopropanol is 40%, and the amount used is 5 times the volume of the interphase contaminants;

[0031] (2) Impurity washing: Add a detergent to the dirt between phases after dispersion, and wash the dirt between phases after dispersion. The control conditions during washing are: temperature 40°C, time 30 min, washing stage 1, phase ratio 3:1. After washing, phase separation is carried out. The washed dirt between phases is then washed with water and phase separation is carried out to obtain the organic phase and washing solution after impurity washing; the detergent is prepared using 2N hydrochloric acid solution and hydrogen peroxide with a mass concentration of 15%, and the volume ratio of hydrogen peroxide to hydrochloric acid solution is 8:92;

[0032] (3) Scandium and zirconium stripping: Add a 10% sodium carbonate solution to the organic phase after impurity washing (the dosage ratio of the two can be determined by the phase ratio and extraction stage. In this example, 2L of 10% sodium carbonate solution is added to 1L of the organic phase after impurity washing, and stripping is carried out 2 times, with a total dosage of 1L:4L, the same below) for scandium and zirconium stripping. The control conditions during stripping are: temperature 45°C, time 60 min, stripping stage 2, phase ratio 2:1. After stripping, phase separation is carried out to obtain scandium zirconium basic carbonate slurry and P204 organic phase. The P204 organic phase is washed once with a 10% hydrochloric acid solution according to a phase ratio of 1:1, and phase separation is carried out to obtain the balanced organic phase, which can be returned for use in nickel and cobalt metallurgy extraction;

[0033] (4) Production of scandium oxalate: Add an ammonium carbonate solution with a mass concentration of 10% three times the volume of the scandium zirconium basic carbonate slurry, stir and slurry, and carry out solid-liquid separation to obtain a scandium-containing solution. Add oxalic acid 1.2 times the theoretical dosage to the scandium-containing solution for the first scandium precipitation. The precipitation temperature is 50°C, the time is 1 h, and the pH is maintained at 3.0 during the precipitation process. Solid-liquid separation is carried out to obtain scandium oxalate precipitate I and post-precipitation solution I; add a 10% hydrochloric acid solution to post-precipitation solution I for complexing dissociation, and then add oxalic acid for the second scandium precipitation. The dosage of oxalic acid is 5 wt.% of the dosage during the first scandium precipitation. The pH is maintained at 1.0 during the precipitation process, and solid-liquid separation is carried out to obtain scandium oxalate precipitate II and post-precipitation solution II;

[0034] (5) Production of scandium oxide: Slurry and wash scandium oxalate precipitate I and scandium oxalate precipitate II with water. The liquid-solid mass ratio during washing is 2:1, the washing time is 1 h, dry, and calcine at 800°C to obtain high-purity scandium oxide (as Figure 1 shown), with a purity of 99.93%;

[0035] (6) Purification: Redissolve the high-purity scandium oxide obtained in step (5). The inorganic acid used during redissolution is hydrochloric acid, and the end-point pH is controlled at 1.5 during redissolution. Oxalic acid is used as a precipitant during impurity removal and scandium precipitation (belonging to secondary purification, which can remove trace impurities such as iron and aluminum, the same below). Dry, and calcine at 800°C to obtain ultra-high-purity scandium oxide, with a purity of 99.995%.

[0036] Calculated based on high-purity scandium oxide, the recovery rate of scandium in this example is 90.07%.

[0037] The content of impurities loaded in the treated organic phase is extremely low, and the period of generating interfacial dirt when it is returned to the extraction system for use is extended. Compared with the ordinary treatment method, when the organic phase treated by the present invention is returned for reuse, the treatment period of interfacial dirt is extended. Specifically, the treatment frequency of interfacial dirt is related to the content of high-valent ions in the extracted original solution. The higher the content of high-valent metal ions (such as iron, aluminum, scandium, zirconium, titanium, chromium, etc.), the higher the treatment frequency of interfacial dirt. For the P204 organic phase not treated by the present invention or the organic phase returned for use after conventional treatment, the interfacial dirt generally needs to be treated once every 1-2 months. When the organic phase treated by the present invention is returned for reuse, the interfacial dirt only needs to be treated once every 6 months to ensure the efficient operation of the extraction system.

[0038] Example 2

[0039] (1) Pretreatment: Kerosene, sodium sulfate, and isopropanol were sequentially added to the interfacial dirt, heated to 40 °C, stirred and slurried for 10 min, then heated to 55 °C, held for 2 h, and then solid-liquid separated to obtain iron-aluminum slag and dispersed interfacial dirt; the mass ratio of sodium sulfate to kerosene was 5:95, and the total amount used was 1 times the volume of the interfacial dirt; the volume concentration of isopropanol was 60%, and the amount used was 3 times the volume of the interfacial dirt;

[0040] (2) Impurity washing: A detergent was added to the dispersed interfacial dirt to wash the dispersed interfacial dirt. The conditions during washing were: temperature 60 °C, time 15 min, washing stage 2, and phase ratio 2:1. After washing, phase separation was carried out. The washed interfacial dirt was then washed with water and phase separation was carried out to obtain the organic phase after impurity washing and the washing solution; the detergent was prepared using 6N hydrochloric acid solution and hydrogen peroxide with a mass concentration of 10%, and the volume ratio of hydrogen peroxide to hydrochloric acid solution was 1:9;

[0041] (3) Scandium-zirconium stripping: 30% sodium carbonate solution was added to the organic phase after impurity washing for scandium-zirconium stripping. The conditions during stripping were: temperature 60 °C, time 30 min, stripping stage 1, and phase ratio 1.5:1. After stripping, phase separation was carried out to obtain scandium-zirconium basic carbonate slurry and P204 organic phase. The P204 organic phase was washed once with 10% sulfuric acid solution according to a phase ratio of 1:1, and phase separation was carried out to obtain the balanced organic phase, which could be returned to nickel-cobalt metallurgy extraction for use;

[0042] (4) Production of scandium oxalate: Add ammonium carbonate solution with a mass concentration of 15% and a volume 1 time that of the scandium zirconium basic carbonate slurry, stir to form a slurry, perform solid-liquid separation to obtain a scandium-containing solution. Add oxalic acid with a dosage 1.5 times the theoretical amount to the scandium-containing solution for the first scandium precipitation. The precipitation temperature is 60 °C, the time is 0.5 h, and the pH is maintained at 2.0 during the precipitation process. Perform solid-liquid separation to obtain scandium oxalate precipitate I and post-scandium precipitation solution I; Add a 10% sulfuric acid solution to post-scandium precipitation solution I for complex dissociation, and then add oxalic acid for the second scandium precipitation. The dosage of oxalic acid is 10 wt.% of that used in the first scandium precipitation. The pH is maintained at 0.8 during the precipitation process and solid-liquid separation is performed to obtain scandium oxalate precipitate II and post-scandium precipitation solution II;

[0043] (5) Production of scandium oxide: Slurry and wash scandium oxalate precipitate I and scandium oxalate precipitate II with water. The liquid-solid mass ratio during washing is 3:1, the washing time is 0.7 h, dry, and calcine at 700 °C to obtain high-purity scandium oxide with a purity of up to 99.92%;

[0044] (6) Purification: Redissolve the high-purity scandium oxide obtained in step (5). Hydrochloric acid is used as the inorganic acid during redissolution, and the end-point pH is controlled at 0.5 during redissolution. Oxalic acid is used as the precipitating agent during impurity removal and scandium precipitation. Dry and calcine at 800 °C to obtain ultra-high-purity scandium oxide with a purity of up to 99.996%.

[0045] Calculated based on high-purity scandium oxide, the recovery rate of scandium in this example is 90.36%.

[0046] The impurity content in the treated organic phase is extremely low, and the period for generating interfacial dirt is extended when it is returned to the extraction system for use. Compared with the ordinary treatment method, when the organic phase treated by the present invention is returned for use again, the period for treating interfacial dirt is extended. Specifically, the frequency of treating interfacial dirt is related to the content of high-valent ions in the extracted raw liquid. The higher the content of high-valent metal ions (such as iron, aluminum, scandium, zirconium, titanium, chromium, etc.), the higher the frequency of treating interfacial dirt. For the P204 organic phase not treated by the present invention or the organic phase returned for use after conventional treatment, the interfacial dirt generally needs to be treated once every 1-2 months. When the organic phase treated by the present invention is returned for use again, the interfacial dirt only needs to be treated once every 6 months to ensure the efficient operation of the extraction system.

[0047] Example 3

[0048] (1) Pretreatment: Sequentially add kerosene, sodium sulfate, and isopropanol to the interfacial dirt, heat to 50 °C, stir to form a slurry for 20 min, then heat up to 65 °C, keep warm for 0.5 h, and perform solid-liquid separation to obtain iron-aluminum slag and dispersed interfacial dirt; The mass ratio of sodium sulfate to kerosene is 3:97, and the total dosage is 1.5 times the volume of the interfacial dirt; The volume concentration of isopropanol is 30%, and the dosage is 6 times the volume of the interfacial dirt;

[0049] (2) Impurity washing: Add a detergent to the dirt between phases after dispersion, and wash the dirt between phases after dispersion. The control conditions during washing are: temperature 50 °C, time 10 min, washing stage number 3, phase ratio 1:1. After washing, phase separation is carried out. The washed dirt between phases is then washed with water and phase separation is carried out to obtain the organic phase and washing solution after impurity washing; the detergent is prepared using a 4N hydrochloric acid solution and hydrogen peroxide with a mass concentration of 25%, where the volume ratio of hydrogen peroxide to hydrochloric acid solution is 5:95;

[0050] (3) Scandium and zirconium stripping: Add a sodium carbonate solution with a mass concentration of 20% to the organic phase after impurity washing for scandium and zirconium stripping. The control conditions during stripping are: temperature 75 °C, time 15 min, stripping stage number 3, phase ratio 1:1. After stripping, phase separation is carried out to obtain a scandium zirconium basic carbonate slurry and a P204 organic phase. The P204 organic phase is washed once with a 15% sulfuric acid solution according to a phase ratio of 1:1, and phase separation is carried out to obtain the balanced organic phase, which can be returned for nickel and cobalt metallurgy extraction;

[0051] (4) Production of scandium oxalate: Add an ammonium carbonate solution with a mass concentration of 12% that is twice its volume to the scandium zirconium basic carbonate slurry, stir and slurry, and carry out solid-liquid separation to obtain a scandium-containing solution. Add oxalic acid that is 1.4 times the theoretical amount to the scandium-containing solution for the first scandium precipitation. The precipitation temperature is 80 °C, the time is 2 h, and the pH is maintained at 1.5 during the precipitation process. Solid-liquid separation is carried out to obtain scandium oxalate precipitate I and post-scandium precipitation solution I; Add a 15% sulfuric acid solution to post-scandium precipitation solution I for complex dissociation, and then add oxalic acid for the second scandium precipitation. The oxalic acid dosage is 20 wt.% of the dosage during the first scandium precipitation. The pH is maintained at 0.5 during the precipitation process and solid-liquid separation is carried out to obtain scandium oxalate precipitate II and post-scandium precipitation solution II;

[0052] (5) Production of scandium oxide: Slurry and wash scandium oxalate precipitate I and scandium oxalate precipitate II with water. The liquid-solid mass ratio during washing is 5:1, the washing time is 0.5 h, dry, and calcine at 1300 °C to obtain high-purity scandium oxide with a purity of up to 99.95%;

[0053] (6) Purification: Redissolve the high-purity scandium oxide obtained in step (5). The inorganic acid used during redissolution is hydrochloric acid. Control the end point pH to be 1.0 during redissolution. Use oxalic acid as the precipitant during impurity removal and scandium precipitation. Dry and calcine at 800 °C to obtain ultra-high-purity scandium oxide with a purity of up to 99.996%.

[0054] Calculated based on high-purity scandium oxide, the recovery rate of scandium in this example is 91.09%.

[0055] The impurity content in the treated organic phase is extremely low, and the period of generating interfacial dirt when it is returned to the extraction system for use is extended. Compared with the ordinary treatment method, when the organic phase treated by the present invention is returned for reuse, the period of treating interfacial dirt is extended. Specifically, the frequency of treating interfacial dirt is related to the content of high-valent ions in the extracted stock solution. The higher the content of high-valent metal ions (such as iron, aluminum, scandium, zirconium, titanium, chromium, etc.), the higher the frequency of treating interfacial dirt. For the P204 organic phase not treated by the present invention or the organic phase returned for use after conventional treatment, the interfacial dirt generally needs to be treated once every 1-2 months. When the organic phase treated by the present invention is returned for reuse, the interfacial dirt only needs to be treated once every 6 months to ensure the efficient operation of the extraction system.

[0056] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications made under the technical spirit disclosed by the present invention shall fall within the scope of the patent covered by the present invention.

Claims

1. A method for producing high-purity scandium oxide from the interfacial dirt generated in the P204 extraction in nickel-cobalt metallurgy, characterized in that, It includes the following steps: (1) Pretreatment: Add an active agent and a dispersant to the interphase contaminants in sequence, heat, stir and pulp, then heat up, keep warm and perform solid-liquid separation to obtain iron-aluminum slag and the dispersed interphase contaminants; (2) Impurity washing: Add a detergent to the dispersed interphase contaminants for washing, separate phases, wash with water, and separate phases again to obtain the organic phase after impurity washing and the washing solution; (3) Scandium and zirconium stripping: Add a sodium carbonate solution to the organic phase after impurity washing for scandium and zirconium stripping, separate phases to obtain the scandium zirconium basic carbonate slurry and the P204 organic phase. The P204 organic phase is balanced with inorganic acid and then returned to be used in nickel-cobalt metallurgy extraction; (4) Production of scandium oxalate: Add an ammonium carbonate solution to the scandium zirconium basic carbonate slurry, stir and pulp, perform solid-liquid separation to obtain a scandium-containing solution. Add oxalic acid to the scandium-containing solution for the first scandium precipitation, perform solid-liquid separation to obtain scandium oxalate precipitate I and the solution after scandium precipitation I; Add inorganic acid to the solution after scandium precipitation I for complex dissociation, and then add oxalic acid for the second scandium precipitation, perform solid-liquid separation to obtain scandium oxalate precipitate II and the solution after scandium precipitation II; (5) Production of scandium oxide: Pulp, wash, dry and calcine scandium oxalate precipitate I and scandium oxalate precipitate II with water to obtain high-purity scandium oxide.

2. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (1), the active agent is a mixture of kerosene and sodium sulfate, and the dispersant is isopropyl alcohol.

3. The method for producing high-purity scandium oxide from the interfacial dirt generated during P204 extraction in nickel-cobalt metallurgy as described in claim 2, characterized in that: In the active agent, the mass ratio of sodium sulfate to kerosene is 1-5:95-99, and the volume concentration of the dispersant is 30-60%.

4. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (1), the dosage of the active agent is 0.5-1.5 times the volume of the interphase contaminants; the dosage of the dispersant is 3-6 times the volume of the interphase contaminants.

5. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (1), heat up to 55-65 °C and keep for 0.5-2 h.

6. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (2), the detergent is a mixture of a 2-6N hydrochloric acid solution with a volume ratio of 90-95:5-10 and hydrogen peroxide with a mass concentration of 10-25%. The control conditions during washing are: temperature 40-60 °C, time 10-30 min, washing stage number 1-3, and phase ratio 1-3:

1.

7. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (3), the concentration of the sodium carbonate solution is 10-30%, and the stripping conditions are: temperature 45-75 °C, time 15-60 min, stripping stage number 1-3, and phase ratio (1-2):

1.

8. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (4), the mass concentration of the ammonium carbonate solution is 10-15%, and the dosage of the ammonium carbonate solution is 1-3 times the volume of the scandium zirconium basic carbonate slurry.

9. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: In the step (4), the dosage of oxalic acid during the first scandium precipitation is 1.2-1.5 times the theoretical dosage, the precipitation temperature is 50-80 °C, the time is 0.5-2 h, and the pH is maintained at 1.5-3.0 during the precipitation process. The inorganic acid added during the second scandium precipitation is hydrochloric acid or sulfuric acid, the dosage of oxalic acid is 5-20% of the dosage during the first scandium precipitation, and the pH is maintained at 0.5-1.0 during the precipitation process.

10. The method for producing high-purity scandium oxide from the interfacial dirt generated by P204 extraction in nickel-cobalt metallurgy as described in claim 1, characterized in that: Redissolve the scandium oxide obtained in the step (5), remove impurities and precipitate scandium, wash, dry and calcine to obtain ultra-high-purity scandium oxide. The inorganic acid used during redissolution is hydrochloric acid or sulfuric acid, the end-point pH is controlled at 0.5-1.5 during redissolution, oxalic acid is used as the precipitating agent during impurity removal and scandium precipitation, and the washing, drying and calcination conditions are the same as those in the step (5).

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