Method for promoting recovery of scandium element

Abstract

The invention discloses a method for promoting scandium element recovery, which comprises the following steps of: adding iron salt into a scandium-containing aluminum solution to obtain an aqueous phase solution, extracting by using an organic phase, separating liquid to obtain an Sc-Fe-organic phase, adding liquid caustic soda to carry out reverse extraction scandium precipitation, separating liquid again to obtain high-scandium slag and a liquid caustic soda water phase, dissolving out the high-scandium slag and the liquid caustic soda water phase, and recycling the scandium element. And sequentially filtering, diluting and separating to obtain high-purity Sc (OH) 3 and lower-concentration caustic soda liquid. According to the method, the co-precipitation characteristic of Sc (OH) 3 and Fe (OH) 3 is utilized, so that the scandium element is efficiently separated from the iron saponification oil residue in the liquid alkali environment, the production difficulty is remarkably reduced, the high purity of the scandium product is ensured, no newly added impurity is added in the whole process, and efficient and clean recovery of the scandium element is realized.

Description

Technical Field

[0001] The invention relates to a method for promoting the recovery of scandium elements, and in particular to a method for improving the properties of scandium slag and promoting the recovery of scandium elements by adding iron for modification during the extraction process, and belongs to the field of hydrometallurgy. Background Art

[0002] Scandium has a low abundance in the earth's crust, but has important industrial applications. Scandium is mainly used as an alloying element or catalyst in aerospace materials, solid oxide fuel cells, LED lighting, laser equipment and other fields.

[0003] Scandium is complex and expensive to extract, mainly because of its low concentration and presence in a variety of ores. Scandium is usually found as a byproduct of bauxite mining, and these deposits are mainly distributed in Australia, Guinea, Brazil, India and other tropical regions. Scandium is sometimes found together with rare earth elements in some rare earth deposits. Rare earth mines are mainly concentrated in China (especially the Bayan Obo mining area in Inner Mongolia), the United States (such as the Madero mine in California), Australia and other countries. The content of scandium in these deposits is generally low, but it is still one of the sources of byproducts in rare earth mining.

[0004] At present, the main method for extracting scandium from ore is extraction. Although the extraction method can effectively extract the scandium element into an organic solvent, it is difficult to separate it from the organic phase. If a specially purified organic solvent is used, the production investment is too high, and the system is complex and difficult to control. If conventional extractants such as P204 and P507 are used, it is difficult to smoothly produce in the stage of stripping and precipitation of scandium. The main reason for this situation is that the scandium in conventional extractants such as P204 and P507 cannot be returned to the aqueous phase by acid washing. At the same time, as the amount of scandium in the organic solvent increases, the organic ratio increases in gravity, and the phase separation process becomes more difficult. In the current technical means, a high concentration of liquid alkali (NaOH) is used to strip and precipitate scandium containing organic matter, and a precipitate is produced in the form of Sc(OH)3 when the organic phase contacts the aqueous phase, thereby realizing the separation of scandium from the organic system. It is inevitable that the contact between the organic solvent and the high concentration of liquid alkali (NaOH) will inevitably produce saponification and generate saponified oil residue. During this process, the newly generated Sc(OH)3 particles are too small to be evenly dispersed in the stripping system again during stirring. Even under centrifugal conditions, the tiny Sc(OH)3 particles cannot cross the organic-water phase boundary. The newly generated saponified oil residue will encapsulate the Sc(OH)3 particles, causing a small amount of scandium product obtained by centrifugation to contain a large amount of soap tissue, affecting its performance and subsequent processing. In addition, the saponified oil residue will also clog the filter holes of filter paper and filter cloth, causing the solid-liquid separation methods such as suction filtration and filter press to fail.

[0005] In summary, affected by many factors in the stripping process, the recovery and extraction of scandium has always been a recognized problem in the industry, which directly leads to the high extraction cost of scandium and also directly leads to the obstruction of the application of scandium element. Therefore, finding a way to improve this phenomenon is of great significance to the utilization of scandium resources. Summary of the invention

[0006] In view of the technical defects in the existing process of separating and extracting scandium and aluminum elements by extraction means, the scandium product is wrapped by saponified oil residue in the stage of stripping and precipitation of scandium, making it difficult to collect, etc., the purpose of the present invention is to provide a method for promoting the recovery of scandium elements, by adding iron to modify the scandium residue during the extraction process, and improving the properties of the scandium residue to promote the recovery of the scandium element. The present invention utilizes the co-precipitation characteristics of Sc(OH)3 and Fe(OH)3 and the amphoteric characteristics of scandium to achieve efficient separation of the scandium element from the iron saponified oil residue in a liquid alkali environment, which not only significantly reduces the difficulty of production, but also ensures the high purity of the scandium product, and there are no new impurities in the whole process, so that the efficient and clean recovery of the scandium element is achieved.

[0007] In order to achieve the above technical objectives, the present invention provides a method for promoting the recovery of scandium elements, comprising adding an iron salt to a scandium-aluminum-containing solution to obtain an aqueous solution; adding an organic phase to the aqueous solution for extraction in an acidic environment, and separating the liquids to obtain a Sc-Fe-organic phase; adding liquid alkali to the Sc-Fe-organic phase for stripping and precipitation of scandium, and separating the liquids again to obtain a high-scandium slag, a liquid alkali aqueous phase and an organic phase, with a small amount of saponified oil residue remaining in the liquid alkali aqueous phase; heating the high-scandium slag and the liquid alkali aqueous phase for dissolution and filtration to obtain a sodium scandate liquid phase and iron-containing solid impurities; cooling and diluting the sodium scandate liquid phase to obtain high-purity Sc(OH)3 and liquid alkali of relatively low concentration; and the organic phase comprises at least one extractant selected from P204, P507, scandium-containing P204 and scandium-containing P507.

[0008] The scandium recovery method provided by the present invention solves the problem that the scandium element is wrapped by saponified oil residue during the stripping process by adding iron at the initial stage of extraction and using Fe(OH)3 as a carrier to form a coprecipitation with Sc(OH)3. The principle is that when using liquid alkali to precipitate scandium, the Fe element is precipitated in the form of Fe(OH)3 and its hydrate; at the same time, the scandium element is precipitated in the form of Sc(OH)3 and attached to Fe(OH)3 and its hydrate to form a coprecipitation; at this stage, Fe(OH)3 plays a role similar to that of a water purifier, and after adsorbing Sc(OH)3, larger yellow particles of Sc(OH)3-Fe(OH)3 composite are generated. The scandium slag has large particles and a hard texture, and is easier to pass through the phase interface and enter the water phase, avoiding the wrapping of the organic solvent saponification product; during the dissolution process, since scandium is amphoteric, the scandium slag can react with the liquid alkali water phase by heating, converting Sc(OH)3 into sodium scandate soluble in the water phase, and the saponified oil residue melts to the upper part of the system as the temperature rises, thereby achieving efficient separation of scandium from Fe(OH)3 and other impurities; after dissolution, the saponified oil residue is re-formed on the surface of the system when the temperature drops, and can be easily removed by low-flow multi-layer gauze filtration to avoid clogging; the sodium scandate solution is diluted with cold water, and the resulting scandium precipitate can be directly washed and dried to obtain a pure scandium product.

[0009] The inventors found that since Sc and Al have similar chemical properties, the main purpose of the extraction of the present invention is to enrich and recover Sc and separate it from Al. 3+ As one of the elements that are easily extracted at low pH, P204 (chemical formula: C 16 H 35 O4P) and / or P507 (chemical formula is C 16 H 35 O3P) can ensure that only Fe 3+ and Sc 3+ Dissolved in the organic phase, Sc element is separated from other impurity elements while ensuring the purity of the system; at the same time, in the subsequent liquid alkali precipitation process of scandium, it can also form yellow particle Sc(OH)3-Fe(OH)3 complex with Sc(OH)3 to avoid being wrapped by saponification products. If other metal salts are used, the pH of the solution must be increased to extract the metal salt into the organic phase, but at the same time, Al element and other impurity elements will also enter the organic phase, greatly reducing the extraction effect.

[0010] As a preferred solution, the organic phase obtained by the stripping and precipitation of the scandium fraction can be reused in the extraction step after acid washing; the iron-containing solid impurities are saponified oil residue and Fe(OH)3.

[0011] As a preferred solution, the iron salt is ferric sulfate.

[0012] As a preferred solution, the content of iron in the aqueous solution is 2-5 g / L, the pH value of the aqueous solution is 0.8-1.2, the Sc:Fe concentration ratio is 1:(3-5), and the volume ratio of the organic phase to the aqueous solution is 2:(5-6). In the present invention, the pH value and the Sc:Fe concentration ratio have an important influence on the effect of extraction and stripping. At pH 0.8-1.2, other metal impurities except Sc will not be extracted into the organic phase, and Fe 3+ Extraction into the organic phase with a distribution coefficient of 0.6 to 0.8 satisfies the conditions for sedimentation modification without conflicting with production. It can also be well separated from Sc during the autoclave dissolution process without affecting the purity and quality of the scandium product. At the same time, the volume ratio of the organic phase and the aqueous phase solution also has a certain influence. If the amount of the aqueous phase is too much, the iron content in the Sc-Fe-organic phase will be too high, resulting in a high specific gravity and difficulty in phase separation.

[0013] As a preferred solution, the scandium concentration in the Sc-Fe-organic phase is not higher than 2 g / L, and the iron concentration is 6-8 g / L.

[0014] As a preferred solution, the organic phase is washed with acid before use to remove impure metal ions in the organic phase.

[0015] As a preferred solution, the extraction conditions are: 50-80°C, and the time is 5-20 min. More preferably, the extraction temperature is 60-70°C, and the time is 10-15 min.

[0016] As a preferred solution, the conditions for the stripping and precipitation of scandium are: temperature of 70-80°C and time of 15-20 minutes. When the temperature is too low, the fluidity of the extractant is poor, and part of the high-scandium residue and the saponified oil residue are suspended in the organic phase, making phase separation difficult; when the temperature is too high, the high temperature during the stripping process is more likely to cause emulsification of the organic phase. At the same time, the volatilization rate of the organic component increases, which is easy to cause environmental pollution in the production workshop.

[0017] As a preferred solution, the amount of the liquid alkali is 1 to 2 times the amount of the Sc-Fe-organic phase, and the liquid alkali is a NaOH solution with a mass concentration of 15% to 25%. The addition of liquid alkali in the present invention is mainly to promote the Sc element in the extractant to be removed in the form of Sc(OH)3 through the NaOH solution, that is, to strip and precipitate scandium; when the concentration of the liquid alkali is too small, the Sc(OH)3 generation rate is significantly reduced, and the required stripping time is increased, which leads to long-term contact between the extractant and the liquid alkali, and emulsification will also occur. Since the stripping process must maintain a certain temperature, when the concentration of the liquid alkali is greater than 25%, the amount of saponified oil residue produced is significantly increased, the system emulsifies in a short time, and the torque of the stirring motor increases rapidly. The amount of liquid alkali directly affects the volume of the reaction tank. If the amount is too small, the concentration of the liquid alkali decreases too much, affecting the precipitation rate of scandium. It is further preferred that the amount of the liquid alkali is 1.5 to 2 times the amount of the Sc-Fe-organic phase.

[0018] As a preferred solution, the dissolution conditions are: temperature of 120-160°C, time of 30-60 min, and pressure of 0.16-0.46 MPa. By controlling the dissolution conditions, the speed of converting Sc(OH)3 into sodium scandate and the efficient separation from Fe(OH)3 and other impurities can be comprehensively regulated.

[0019] As a preferred solution, the filtering method is filtering through multiple layers of gauze at a low flow rate. Since the saponified oil residue after the stripping and precipitation of scandium is co-precipitated with the scandium residue and sent to the autoclave for dissolution, a small amount of oil film also exists on the surface of the liquid phase after filtering through the multiple layers of gauze. After dilution by passing water to the bottom of the liquid, sodium scandate decomposes into flocculent Sc(OH)3, which is then extracted from the bottom to avoid contamination of the scandium product, and the resulting scandium product is pure.

[0020] The present invention provides a method for promoting the recovery of scandium elements, which specifically comprises the following steps:

[0021] 1) preparing a pure iron salt solution or adding a corresponding iron salt to a scandium-aluminum-containing aqueous phase to obtain an aqueous phase solution;

[0022] 2) adding an organic phase to the aqueous solution obtained in step 1) to perform extraction under an acidic environment;

[0023] 3) separating the extraction system obtained in step 2) to obtain a Sc-Fe-organic phase;

[0024] 4) adding liquid alkali (NaOH) to the Sc-Fe-organic phase obtained in step 3) to perform stripping and precipitation of scandium, and obtaining a high-scandium residue, a liquid alkali aqueous phase and an organic phase after separation, with a small amount of saponified oil residue remaining in the liquid alkali aqueous phase;

[0025] 5) heating the high-scandium slag and the aqueous caustic soda phase obtained in step 4) to dissolve the Sc(OH)3 therein;

[0026] 6) filtering the dissolution system obtained in step 5) to remove insoluble Fe(OH)3 and saponified oil residue to obtain a sodium scandate liquid phase;

[0027] 7) diluting and separating the sodium scandate liquid phase obtained in step 6) to obtain pure Sc(OH)3 and liquid alkali (NaOH) of lower concentration.

[0028] Compared with the prior art, the technical solution of the present invention brings about the following innovative and beneficial technical effects:

[0029] 1) In traditional scandium recovery, the organic system precipitation process is complicated and inefficient. The present invention introduces iron element modification in the early stage of extraction, uses Fe(OH)3 as a carrier, and forms a stable co-precipitation with Sc(OH)3, which greatly improves the precipitation efficiency of scandium and simplifies the production process. The co-precipitated scandium residue has large particles and hard texture, which effectively enhances its penetration ability in the system and avoids being wrapped by the saponified oil residue of the organic solvent, thereby directly solving the problem of scandium precipitation difficulty, greatly reducing the production difficulty, and improving the recovery rate and production efficiency of scandium.

[0030] 2) In the traditional process of scandium recovery, Sc(OH)3 is easily wrapped by saponified oil residue, resulting in low product purity. The present invention forms a Sc(OH)3-Fe(OH)3 complex through the co-precipitation of scandium and iron elements, and utilizes the characteristics of scandium residue to achieve natural separation from saponified oil residue even during the autoclave dissolution process. Sc(OH)3 is converted into soluble sodium scandate under alkaline conditions, effectively getting rid of the constraints of saponified oil residue. Through subsequent dissolution and filtration steps, a pure scandium product is finally obtained, which significantly improves the purity and quality of the scandium product.

[0031] 3) The scandium recovery method of the present invention directly uses alkali dissolution to separate scandium from Fe-saponified oil residue when the high-scandium slag remains in a liquid alkali environment, avoiding new impurities that may be introduced by using other chemical reagents. During the dissolution process, sodium scandate and Fe(OH)3 are effectively separated, and a pure scandium product can be obtained without additional treatment, ensuring the purity and environmental protection of the entire scandium recovery process, not only improving the purity of the scandium product, but also reducing the negative impact on the environment, achieving the dual goals of efficient and pure recovery of scandium elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart of Example 1 of the present invention, in which the organic solvent refers to the organic phase. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be further described below in conjunction with specific embodiments of the present invention. It should be noted that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments; these embodiments are only for a better understanding of the present invention, rather than limiting the scope of protection of the present invention.

[0034] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0035] Example 1

[0036] This embodiment is a method for promoting the recovery of scandium elements. See the process flow chart. Figure 1 , the specific steps are as follows:

[0037] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0038] (2) Take 5 L of scandium-aluminum solution, add 55 g of Fe2(SO4)3 solid powder (dry weight) thereto, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0039] (3) The aqueous phase solution was extracted with P204 at a temperature of 60°C for 5 min. After separation, an Sc-Fe-P204 organic phase (wherein the scandium concentration was less than 2 g / L and the iron concentration was approximately 7 g / L) was obtained.

[0040] (4) The Sc-Fe-P204 organic phase is stripped by adding 1.5 times the volume of the Sc-Fe-P204 organic phase, wherein the liquid alkali is a 20% mass concentration NaOH solution (about 6 mol / L); the stripping temperature is 75°C and the stripping time is 15 min.

[0041] (5) The stripping system is separated, and the aqueous phase, precipitate, and saponified oil residue are sent to an autoclave for dissolution.

[0042] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0043] (7) After the reaction is completed, the system is filtered through gauze, and the soap tissue adheres to the gauze during the filtering process.

[0044] (8) The liquid phase is allowed to stand, during which cold water is passed from the bottom of the liquid phase to cool it down. A small amount of soap tissue is observed to solidify on the surface of the liquid phase and a large amount of flocculent precipitate is formed at the bottom of the liquid phase. The flocculent precipitate is extracted from the bottom of the liquid phase, washed, and filtered to obtain the scandium product.

[0045] The compositions of the scandium-containing aluminum solution and the scandium product after the iron modification in step (2) are shown in Table 1.

[0046] Table 1

[0047]

[0048] It can be seen that in the scandium stripping and precipitation stage of the process, the scandium element precipitates in the form of Sc(OH)3 and attaches to Fe(OH)3 and its hydrate to form a scandium slag co-precipitation. The scandium slag has large particles and a hard texture, making it easier to pass through the phase interface and enter the water phase. Since the rate of scandium slag co-precipitation is much faster than the rate of soapization of the organic phase during this period, Sc(OH)3 preferentially combines with Fe(OH)3 and has a larger surface area to avoid being wrapped by saponified oil residue.

[0049] When the scandium residue enters the water phase, the system is separated, the organic phase is removed and recycled, and the saponified oil residue does not need to be separated in this process. During the autoclave dissolution process, the saponified oil residue melts to the upper part of the system as the temperature rises; Sc(OH)3 can be separated from it because it is not coated by the saponified oil residue. At the same time, in an alkaline environment, Sc(OH)3 in the scandium residue co-precipitation reacts with NaOH to form sodium scandate due to its own amphoteric properties and dissolves in the liquid phase, thereby achieving separation from Fe(OH)3.

[0050] After the autoclave dissolution is completed, the soapy oil residue re-forms soap tissue on the surface of the system, which is easy to block the filter pores. Filtering through multiple layers of gauze at a low flow rate can effectively avoid this problem. After the filtration is completed, cold water is added from the bottom to dilute the obtained sodium scandate solution, and a large amount of flocculent precipitation can be observed. After the precipitate is extracted, it is washed and dried to obtain the scandium product.

[0051] Example 2

[0052] This embodiment is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0053] (1) Take 2L of P507 and wash it with 2mol / L H2SO4 for later use.

[0054] (2) Take 5 L of scandium-aluminum solution, add 55 g of Fe2(SO4)3 solid powder (dry weight) to it, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0055] (3) The aqueous phase solution was extracted with P507 at a temperature of 60°C for 5 min. After separation, an Sc-Fe-P507 organic phase (wherein the scandium content was less than 2 g / L and the iron concentration was about 7 g / L) was obtained.

[0056] (4) The Sc-Fe-P507 organic phase was stripped by adding 1.6 times the volume of the Sc-Fe-P507 organic phase, wherein the liquid alkali was a 18% mass concentration NaOH solution (about 5.5 mol / L); the stripping temperature was 80°C and the stripping time was 15 min.

[0057] (5) The stripping system is separated, and the aqueous phase, precipitate, and saponified oil residue are dissolved in an autoclave.

[0058] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0059] (7) After the reaction is completed, the system is filtered through gauze; during the filtering process, the soap tissue adheres to the gauze.

[0060] (8) The liquid phase is allowed to stand, during which cold water is passed from the bottom of the liquid phase to cool it down. A small amount of soap tissue is observed to solidify on the surface of the liquid phase and a large amount of flocculent precipitate is formed at the bottom of the liquid phase. The flocculent precipitate is extracted from the bottom of the liquid phase, washed, and filtered to obtain the scandium product.

[0061] The compositions of the scandium-aluminum solution and the scandium product after the iron modification in step (2) are shown in Table 2.

[0062] Table 2

[0063]

[0064]

[0065] It can be seen that the process is also very adaptable to the organic solvent P507. After the experiment, there is no obvious difference in the composition of the scandium product. The scandium content in the scandium product reaches 38.46%.

[0066] Example 3

[0067] This embodiment is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0068] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0069] (2) Take 5 L of scandium-aluminum solution, add 55 g of Fe2(SO4)3 solid powder into it, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 0.8.

[0070] (3) The aqueous phase solution was extracted with P204 at a temperature of 70°C for 5 min. After separation, an Sc-Fe-P204 organic phase (wherein the scandium concentration was less than 2 g / L and the iron concentration was approximately 7 g / L) was obtained.

[0071] (4) The Sc-Fe-P204 organic phase is stripped by adding liquid caustic soda in an amount twice the volume of the Sc-Fe-P204 organic phase, wherein the liquid caustic soda is a 18% mass concentration NaOH solution (about 5.5 mol / L); the stripping temperature is 80°C and the stripping time is 15 min.

[0072] (5) The stripping system is separated, and the aqueous phase, precipitate, and saponified oil residue are sent to an autoclave for dissolution.

[0073] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0074] (7) After the reaction is completed, the system is filtered through gauze, and the soap tissue adheres to the gauze during the filtering process.

[0075] (8) The liquid phase is allowed to stand, during which cold water is passed from the bottom of the liquid phase to cool it down. A small amount of soap tissue is observed to solidify on the surface of the liquid phase and a large amount of flocculent precipitate is formed at the bottom of the liquid phase. The flocculent precipitate is extracted from the bottom of the liquid phase, washed, and filtered to obtain the scandium product.

[0076] The compositions of the scandium-containing aluminum solution and the scandium product after the iron modification in step (2) are shown in Table 3.

[0077] Table 3

[0078]

[0079] Comparative Example 1

[0080] This embodiment is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0081] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0082] (2) Take 7 L of scandium-aluminum solution, add 80 g of Fe2(SO4)3 solid powder (dry weight) thereto, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0083] (3) The aqueous phase solution was extracted with P204 at a temperature of 60°C for 5 min. After separation, an Sc-Fe-P204 organic phase was obtained.

[0084] (4) The Sc-Fe-P204 organic phase is stripped by adding 1.8 times the volume of the Sc-Fe-P204 organic phase, wherein the liquid alkali is a 18% mass concentration NaOH solution (about 5.5 mol / L); the stripping temperature is 80°C and the stripping time is 15 min.

[0085] (5) Separate the stripping system and send the aqueous phase, precipitate and saponified oil residue to an autoclave for dissolution.

[0086] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0087] (7) After the reaction is completed, the system is filtered through gauze; during the filtering process, the soap tissue adheres to the gauze.

[0088] (8) The liquid phase is allowed to stand, during which cold water is passed from the bottom of the liquid phase to cool it down. A small amount of soap tissue is observed to solidify on the surface of the liquid phase and a large amount of flocculent precipitate is formed at the bottom of the liquid phase. The flocculent precipitate is extracted from the bottom of the liquid phase, washed, and filtered to obtain the scandium product.

[0089] The compositions of the scandium-aluminum solution and the scandium product after the iron modification in step (2) are shown in Table 4.

[0090] Table 4

[0091]

[0092] It can be seen that increasing the oil-water ratio (O / A) in the extraction stage cannot increase the Sc concentration in the scandium-containing organic phase to further improve production efficiency. Although the scandium content in the scandium product is slightly reduced, the scandium processing capacity per equivalent organic phase is increased by about 40%. Under this condition, the Sc content in the organic phase after extraction is about 2.6g / L; because sufficient Fe(OH)3 needs to be produced in the process of stripping and precipitation of scandium to adsorb Sc(OH)3, the Fe content in the organic solvent reaches 10g / L.

[0093] The direct impact of this situation is that during the extraction process of step (4), the organic phase gravity increases, making phase separation difficult; during steps (4) and (5), there is too much precipitate and the system is turbid, making it difficult to define the organic-liquid phase interface and separate the extractant from the organic phase.

[0094] Therefore, it is not recommended that the Sc concentration in the scandium-containing organic matter exceed 2 g / L in this process.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is that no iron salt is added during the extraction stage. The specific steps are as follows:

[0097] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0098] (2) Take 5 L of scandium solution, adjust the pH to 1.2, and do no other treatment.

[0099] (3) Use P204 to extract the scandium-containing solution at a temperature of 60°C for 5 minutes; after separation, a Sc-P204 organic phase is obtained.

[0100] (4) The Sc-P204 organic phase is stripped by adding 1.5 times the volume of the Sc-P204 organic phase liquid alkali, wherein the liquid alkali is a 20% mass concentration NaOH solution (about 6 mol / L); the stripping temperature is 75°C and the stripping time is 15 min.

[0101] (5) The stripping system is separated, and the aqueous phase, precipitate, and saponified oil residue are sent to an autoclave for dissolution.

[0102] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0103] (7) After the reaction is completed, the system is filtered through gauze, and the soap tissue adheres to the gauze during the filtering process.

[0104] (8) The liquid phase is allowed to stand, during which time cold water is introduced from the bottom of the liquid phase to cool it down.

[0105] The Sc(OH)3 generated in step (4) is coated with saponified oil residue, which makes it extremely difficult to filter and wash or to dissolve in an autoclave. Since the filtration system includes a solid phase saponified oil residue, an organic phase extractant, and an aqueous phase NaOH solution, the saponified oil residue deforms under pressure and blocks the filter pores of the filter cloth and filter paper. While the Sc(OH)3 is coated more thoroughly, the contact time between the organic phase and the NaOH solution is greatly prolonged, and the system will gradually turn into a gel state, making it impossible to filter; during the autoclave dissolution process, the saponified oil residue is redissolved at high temperature into an organic layer floating on the surface of the system. In this process, the coated Sc(OH)3 cannot contact the NaOH solution to generate soluble sodium scandate, so there is no obvious phenomenon in step (8).

[0106] Comparative Example 3

[0107] This comparative example is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0108] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0109] (2) Take 5 L of scandium-aluminum solution, add 55 g of Fe2(SO4)3 solid powder (dry weight) to it, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0110] (3) The watermark camera solution was extracted using P204 at a temperature of 60°C for 5 min. After separation, an Sc-Fe-P204 organic phase (wherein the scandium concentration was less than 2 g / L and the iron concentration was approximately 7 g / L) was obtained.

[0111] (4) The Sc-Fe-P204 organic phase is stripped by adding 1.5 times the volume of the Sc-Fe-P204 organic phase, wherein the liquid alkali is a 20% mass concentration NaOH solution (about 6 mol / L); the stripping temperature is 60°C and the stripping time is 15 min.

[0112] In this comparative example 3 and example 1, only the stripping temperature is reduced from 75°C to 60°C. In the stripping stage, due to the lower temperature, the fluidity of the organic phase is extremely poor. The macroscopic manifestation is that the extractant is coated with a large amount of NaOH solution, and the emulsification phenomenon is obvious inside the organic phase, and no obvious phase boundary can be observed. The saponified oil residue and high-scandium residue generated during the period cannot be separated from the stripping system with the water phase, and the experiment is terminated.

[0113] In other related single-factor comparison experiments of stripping temperature, the following conclusions can be drawn: when the temperature is less than 70°C, the fluidity of the extractant is poor, and part of the high-scandium residue and saponified oil residue are suspended in the organic phase, making phase separation difficult; when the temperature is higher than 80°C, the high temperature during the stripping process is more likely to cause emulsification of the organic phase. At the same time, the volatilization rate of the organic component increases, which is easy to cause environmental pollution in the production workshop. In summary, the stripping temperature should be controlled at 70-80°C, and more preferably 75-80°C.

[0114] Comparative Example 4

[0115] This embodiment is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0116] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0117] (2) Take 5 L of scandium-aluminum solution, add 32 g of Fe2(SO4)3 solid powder (dry weight) to it, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0118] (3) Extracting the aqueous solution with P204 at a temperature of 60°C for 5 min; after separation, an Sc-Fe-P204 organic phase (wherein the scandium concentration is less than 2 g / L and the iron concentration is approximately 4 g / L) is obtained.

[0119] (4) The Sc-Fe-P204 organic phase is stripped by adding 1.5 times the volume of the Sc-Fe-P204 organic phase, wherein the liquid alkali is a 20% mass concentration NaOH solution (about 6 mol / L); the stripping temperature is 75°C and the stripping time is 15 min.

[0120] (5) The stripping system is separated, and the aqueous phase, precipitate, and saponified oil residue are sent to an autoclave for dissolution.

[0121] (6) The dissolution temperature of the autoclave is 120°C, the reaction time is 45 min, and the pressure is 0.18 MPa.

[0122] (7) After the reaction is completed, the system is filtered through gauze, and the soap tissue adheres to the gauze during the filtering process.

[0123] (8) The liquid phase is allowed to stand, during which time cold water is introduced from the bottom of the liquid phase to cool it down.

[0124] The only difference between this comparative example 4 and Example 1 is the mass of the Fe2(SO4)3 solid powder added to the scandium-containing solution. The actual impact is that the iron concentration in the obtained Sc-Fe-P204 organic phase is about 5 g / L. In the scandium stripping and precipitation stage, there is no obvious difference from Example 1. The scandium residue and saponified oil residue are normally enriched in the water phase without emulsification. In the dilution and recovery stage of step (8), only slight turbidity of the solution is observed, and no flocculent precipitation is produced, that is, the scandium element is not dissolved in the autoclave.

[0125] Due to the reduction of Fe content in the scandium-containing solution, the generated high-scandium slag is not sufficient to avoid being completely covered by the saponified oil residue, resulting in the high-scandium slag being unable to contact the NaOH solution in the autoclave, no sodium scandate is generated, and no scandium product can be obtained.

[0126] In summary, when the scandium concentration in the organic phase is lower than 2g / L and the iron concentration is about 4g / L, it can only meet the effective enrichment of high-scandium slag and saponified oil residue in the scandium stripping and precipitation stage, so that it can be separated with the water phase, and it is impossible to avoid the high-scandium slag being coated by the saponified oil residue; if with the development of technology, only the high-scandium slag is required to be removed from the organic phase, then the iron concentration in the organic phase can be reduced to 4g / L. In the present invention, the scandium concentration in the organic phase is not higher than 2g / L, and the iron concentration is 6-8g / L.

[0127] Comparative Example 5

[0128] This comparative example is a method for promoting the recovery of scandium elements, and the specific steps are as follows:

[0129] (1) Take 2L of P204 and wash it with 2mol / L H2SO4 for later use.

[0130] (2) Take 5 L of scandium-aluminum solution, add 55 g of Fe2(SO4)3 solid powder (dry weight) to it, wait for it to fully dissolve to obtain an aqueous phase solution, and adjust the pH to 1.2.

[0131] (3) The aqueous phase solution was extracted with P204 at a temperature of 60°C for 5 min. After separation, an Sc-Fe-P204 organic phase (wherein the scandium concentration was less than 2 g / L and the iron concentration was approximately 7 g / L) was obtained.

[0132] (4) The Sc-Fe-P204 organic phase is stripped by adding 1.5 times the volume of the Sc-Fe-P204 organic phase, wherein the liquid alkali is a 30% mass concentration NaOH solution (about 10 mol / L); the stripping temperature is 75°C and the time is 5 min.

[0133] The only difference between this comparative example 5 and Example 1 is the concentration of NaOH solution and the stripping time in the stripping stage. In the stripping stage, the excessively high alkali concentration reacts with the organic phase to cause saponification, causing the system to quickly become turbid and the torque of the stirring motor to increase abnormally. After 5 minutes, the system is completely emulsified and the experiment is terminated.

[0134] In fact, in the exploratory experiments of other NaOH solution concentrations and stripping times, in order to ensure the effective precipitation of Sc elements and the absence of emulsification in the stripping system, the following conclusions were obtained: when the concentration of liquid alkali is less than 15%, the generation rate of Sc(OH)3 decreases significantly, and the required stripping time increases, which leads to long-term contact between the extractant and the liquid alkali, and emulsification will also occur. Since the stripping process must maintain a certain temperature, when the concentration of liquid alkali is greater than 25%, the amount of saponified oil residue produced increases significantly, the system emulsifies in a short period of time, and the torque of the stirring motor increases rapidly. In summary, the concentration of NaOH solution in the stripping and precipitation stage of scandium is controlled at 15% to 25% (mass fraction), and the stripping time is controlled at 15 to 20 minutes.

[0135] The above embodiments are only for better explanation of the principles and practical applications of the present invention, so that those skilled in the relevant technical field can better understand and utilize the present invention, but they are not intended to limit the patent scope of the present invention. All equivalent changes made using the contents of the present invention are within the patent protection scope of the present invention.

Claims

1. A method for promoting the recovery of scandium, characterized in that: Add iron salt to a solution containing scandium and aluminum to obtain an aqueous solution; add an organic phase to the aqueous solution and extract it in an acidic environment, and separate the liquids to obtain a Sc-Fe-organic phase; add liquid alkali to the Sc-Fe-organic phase to reversely extract and precipitate scandium, and separate the liquids again to obtain a high-scandium slag, a liquid alkali aqueous phase and an organic phase, with a small amount of saponified oil residue remaining in the liquid alkali aqueous phase; heat the high-scandium slag and the liquid alkali aqueous phase for dissolution and filtration to obtain a sodium scandate liquid phase and iron-containing solid impurities; cool and dilute the sodium scandate liquid phase to obtain high-purity Sc(OH)3 and liquid alkali with a relatively low concentration; The organic phase comprises at least one extractant selected from the group consisting of P204, P507, P204 containing scandium, and P507 containing scandium.

2. A method for promoting the recovery of scandium according to claim 1, characterized in that: The iron salt is ferric sulfate.

3. A method for promoting the recovery of scandium according to claim 2, characterized in that: The content of iron in the aqueous solution is 2-5 g / L, the pH value of the aqueous solution is 0.8-1.2, the Sc:Fe concentration ratio is 1:(3-5), and the volume ratio of the organic phase to the aqueous solution is 2:(5-6).

4. A method for promoting the recovery of scandium according to claim 2, characterized in that: The scandium concentration in the Sc-Fe-organic phase is not higher than 2 g / L, and the iron concentration is 6-8 g / L.

5. A method for promoting the recovery of scandium according to claim 4, characterized in that: The extraction conditions are as follows: temperature of 50-80° C. and time of 5-20 min.

6. A method for promoting the recovery of scandium according to claim 5, characterized in that: The conditions for the stripping and precipitation of scandium are: temperature of 70-80° C. and time of 15-20 min.

7. A method for promoting the recovery of scandium according to claim 1 or 4, characterized in that: The amount of the liquid alkali used is 1 to 2 times the volume of the Sc-Fe-organic phase; the liquid alkali is a NaOH solution with a mass concentration of 15% to 25%.

8. The method for promoting the recovery of scandium according to claim 1, characterized in that: The dissolution conditions are: temperature of 120-160° C., time of 30-60 min, and pressure of 0.16-0.46 MPa.

9. A method for promoting the recovery of scandium according to claim 8, characterized in that: The filtering method is filtering through multiple layers of gauze at a low flow rate.

Images