Method for extracting scandium in red mud

Abstract

Disclosed is a method for extracting scandium from red mud, comprising: obtaining a scandium-rich product from red mud; and using an alkaline buffer solution to leach the scandium-rich product to obtain a scandium-containing mixed solution, wherein the alkaline buffer solution is a mixed solution of carbonate and bicarbonate.

Description

A method for extracting scandium from red mud

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202311025736.X filed on August 15, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of comprehensive utilization of solid waste, and in particular to a method for extracting scandium from red mud. Background Art

[0004] Red mud is a solid waste generated during alumina production. With the development of the aluminum industry and the decline in bauxite ore grades in recent years, red mud production and reserves have increased annually, reaching over 105 million tons in 2022. Currently, alumina companies typically handle red mud by stockpiling it, with a comprehensive utilization rate of less than 8%. This not only wastes resources but also occupies significant land resources, poses environmental pollution, and poses various safety risks. During the Bayer process for alumina production, elements such as iron, calcium, titanium, zirconium, and scandium, which are present in the bauxite, become insoluble during alkaline solution dissolution and remain in the red mud, where they are concentrated. The Sc2O3 content in bauxite ranges from 40 to 150 μg / g. Over 98% of this Sc2O3 is concentrated in the red mud, bringing the Sc2O3 content to 0.02%. Therefore, red mud is a high-quality raw material for the industrial extraction of scandium.

[0005] Currently, scandium is typically recovered from red mud through wet acid leaching and pyrometallurgy. Wet acid leaching typically involves red mud pretreatment, acid leaching, solvent extraction, precipitation, and calcination. However, due to the high alkalinity of red mud, the treatment process not only requires a large amount of acid but also suffers from drawbacks such as co-leaching of impurities, interference with subsequent separation, and difficulty in handling waste acid. Pyrometallurgy, with its high energy consumption, complex process, and the generation of large amounts of waste gas, which creates secondary pollution, is not in line with the concept of green environmental protection.

[0006] Summary of the Invention

[0007] By utilizing one or more embodiments of the present disclosure, the technical problem of high difficulty in recovering scandium from red mud by wet acid leaching is solved.

[0008] According to some embodiments of the present disclosure, a method for extracting scandium from red mud includes: obtaining a scandium-rich product from red mud; and leaching the scandium-rich product with an alkaline buffer solution to obtain a scandium-containing mixed solution; wherein the alkaline buffer solution is a mixed solution of carbonate and bicarbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0011] FIG1 shows a schematic flow chart of a method for extracting scandium from red mud according to some embodiments of the present disclosure.

[0012] FIG2 shows a schematic flow chart of a method for extracting scandium from red mud according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0014] Various embodiments of the present disclosure may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the present disclosure; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0015] In the present disclosure, unless otherwise specified, the directional words used, such as "upper" and "lower", specifically refer to the directions of the drawings in the accompanying drawings. In addition, in the description of the present disclosure, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0016] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased from the market or prepared by existing methods.

[0017] According to some embodiments of the present disclosure, a method for extracting scandium from red mud is provided, as shown in Figures 1 and 2 , the method comprising:

[0018] S1. obtaining a scandium-rich product from red mud; and

[0019] S2, leaching the scandium-rich product with an alkaline buffer solution to obtain a scandium-containing mixed solution;

[0020] Wherein, the alkaline buffer solution is a mixed solution of carbonate and bicarbonate.

[0021] In some embodiments, step S1 of obtaining a scandium-rich product from red mud may include: performing graded screening and magnetic separation on the red mud to obtain the scandium-rich product.

[0022] Red mud can be treated by graded screening and magnetic separation technology to achieve the enrichment of scandium in the red mud, and the subsequent red mud processing volume can be reduced by more than 20%.

[0023] In some embodiments, the particle size of the graded screening may be 23 μm to 74 μm.

[0024] The grading equipment used for the grading and screening can be a high-frequency vibrating screen. The particle size of the red mud grading and screening is controlled to be 23μm to 74μm. This is because the content of scandium in red mud varies in different particle sizes. As the red mud particle size decreases, the scandium content gradually increases. If the red mud particle size is too large, it will be detrimental to subsequent magnetic separation. If the red mud particle size is too small, the enrichment effect is not obvious. In some embodiments, the particle size of the grading and screening can be 23μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 74μm, etc.

[0025] In some embodiments, the magnetic field strength of the magnetic separation is 0.3T to 1.5T.

[0026] The magnetic separation equipment used can be a SLON high-gradient magnetic separator. The magnetic field strength for red mud magnetic separation is controlled to be 0.3T to 1.5T. This is because scandium is primarily present in non-magnetic minerals after magnetic separation of red mud. If the magnetic separation strength is too low, fewer magnetic minerals are obtained, making it impossible to enrich scandium. If the magnetic separation strength is too high, magnetic minerals may be mixed with non-magnetic minerals, thereby reducing scandium enrichment. In some embodiments, the magnetic field strength for magnetic separation can be 0.3T, 0.5T, 0.7T, 0.9T, 1.1T, 1.3T, 1.5T, etc.

[0027] In some embodiments, in step S2, an alkaline buffer solution is used to leach the scandium-rich product to obtain a scandium-containing mixed solution; wherein the alkaline buffer solution can be a mixed solution of carbonate and bicarbonate.

[0028] In some embodiments, the scandium-containing mixed solution after leaching can be filtered to remove the filter residue to obtain a scandium-containing mixed solution with higher purity.

[0029] In some embodiments, the molar ratio of carbonate to bicarbonate is 1:1 to 1:5.

[0030] The molar ratio of carbonate to bicarbonate is controlled to be 1:1 to 1:5. The reason is that the alkaline environment required for leaching scandium from the scandium-rich product is mainly provided by the alkaline buffer solution. If the alkaline content of the alkaline buffer solution is too low, the alkaline substance content in the alkaline buffer solution will be insufficient, and a sufficient alkaline environment cannot be formed, thereby affecting the dissolution of scandium and reducing the leaching efficiency of scandium. If the alkaline content of the alkaline buffer solution is too high, the alkaline substance content in the alkaline buffer solution will be too high, forming an overly alkaline environment, thereby slowing down the dissolution rate of scandium and even causing scandium precipitation, resulting in reduced leaching efficiency. Therefore, it is necessary to control the molar ratio of carbonate to bicarbonate in the alkaline buffer solution to ensure that the alkalinity of the alkaline buffer solution is moderate (pH = 8 to 10) to promote the dissolution of scandium in the scandium-rich product. In some embodiments, the molar ratio of carbonate to bicarbonate can be 1:1, 1:2, 1:3, 1:4, 1:5, etc.

[0031] In some embodiments, the alkaline buffer solution is a mixed solution of Na2CO3 and NaHCO3 or a mixed solution of K2CO3 and KHCO3.

[0032] The reason for using carbonate-bicarbonate alkaline buffer solution as the alkaline leaching agent for scandium is that scandium exists in the form of compounds in red mud, such as Sc(OH)3, ScO(OH), etc. In the relatively mild carbonate-bicarbonate alkaline buffer solution, the scandium compounds can be completely or partially decomposed and leached. By making the alkaline buffer solution a mixed solution of Na2CO3 and NaHCO3 or a mixed solution of K2CO3 and KHCO3, the alkaline buffer solution can be made milder, thereby ensuring that the scandium compounds can be completely or partially decomposed and leached, thereby ensuring the leaching rate of scandium. The method for extracting scandium from red mud disclosed in the present invention can avoid the problems of using a large amount of acidic leaching agent to leach scandium, such as the co-leaching of impurity elements, interference with subsequent separation, and difficulty in handling waste acid. In addition, the method for extracting scandium from red mud disclosed in the present invention has the advantages of using a small amount of alkaline buffer solution and low cost.

[0033] In some embodiments, the leaching process parameters include: a weight ratio of the alkaline buffer solution to the red mud, a leaching temperature, and a leaching time.

[0034] In some embodiments, the weight ratio of the alkaline buffer solution to the red mud is 5-10.

[0035] By controlling the weight ratio of the alkaline buffer solution to the red mud to be 5 to 10, the leaching rate of scandium and the subsequent extraction operation can be improved. If the weight ratio of the buffer solution to the red mud is relatively low, the leaching of scandium in the red mud is incomplete and the leaching rate of scandium is low. If the weight ratio of the buffer solution to the red mud is relatively large, the scandium concentration in the obtained scandium-containing mixed solution is low, which is not conducive to the subsequent extraction operation.

[0036] In some embodiments, the leaching temperature is 30° C. to 90° C., and / or the leaching time is 30 min to 180 min.

[0037] By controlling the leaching temperature between 30°C and 90°C, the leaching efficiency of scandium from red mud can be ensured to be high. This is because the leaching temperature has a significant impact on the leaching rate of scandium from red mud. If the leaching temperature is low, the activity of the chemical substances in the red mud is low, and the reaction progresses slowly. As the leaching temperature increases, the reaction progresses faster. However, if the leaching temperature is too high, the physical volatilization rate of the alkaline buffer solution will be accelerated, which will accelerate the hydrolysis of scandium and reduce the scandium content in the leachate.

[0038] By controlling the leaching time to 30 to 180 minutes, a high leaching rate of scandium from red mud can be ensured. This is because leaching time has a significant impact on the leaching rate of scandium from red mud. If the leaching time is too short, the leaching reaction is incomplete, resulting in a low leaching rate of scandium from the red mud. If the leaching time is too long, when the scandium concentration in the alkaline buffer solution reaches a certain level, the scandium in the alkaline buffer solution will precipitate.

[0039] In some embodiments, the leaching process parameters include: a weight ratio of the alkaline buffer solution to the scandium-rich product, a leaching temperature, and a leaching time.

[0040] In some embodiments, the weight ratio of the alkaline buffer solution to the scandium-rich product is 5-10.

[0041] By controlling the weight ratio of the alkaline buffer solution to the scandium-rich product to 5 to 10, the leaching rate of scandium and subsequent extraction operations can be improved. If the weight ratio of the buffer solution to the scandium-rich product is relatively low, the leaching of scandium in the scandium-rich product is incomplete and the leaching rate of scandium is low. If the weight ratio of the buffer solution to the scandium-rich product is relatively large, the scandium concentration in the obtained scandium-containing mixed solution is low, which is not conducive to subsequent extraction operations.

[0042] By controlling the leaching temperature between 30°C and 90°C, a high leaching efficiency of scandium in the scandium-rich product can be ensured. This is because the leaching temperature has a significant impact on the leaching rate of scandium in the scandium-rich product. If the leaching temperature is low, the chemical activity in the scandium-rich product is low, and the reaction progresses slowly. As the leaching temperature increases, the reaction progresses faster. However, if the leaching temperature is too high, the physical volatilization rate of the alkaline buffer solution is accelerated, the hydrolysis of scandium is accelerated, and the scandium content in the leachate is reduced.

[0043] By controlling the leaching time to 30 to 180 minutes, a high leaching rate of scandium in the scandium-rich product can be ensured. This is because the leaching time has a significant impact on the leaching rate of scandium in the scandium-rich product. If the leaching time is too short, the leaching reaction is incomplete, resulting in a low leaching rate of scandium in the scandium-rich product. If the leaching time is too long, when the scandium concentration in the alkaline buffer solution reaches a certain level, the scandium in the alkaline buffer solution will precipitate.

[0044] In some embodiments, the leaching temperature can be 30°C, 50°C, 70°C, 90°C, etc.; the leaching time can be 30min, 60min, 90min, 120min, 150min, 180min, etc.; the weight ratio of the alkaline buffer solution to the scandium-rich product can be 5, 7, 9, 10, etc.

[0045] In some embodiments, as shown in FIG2 , after the step of leaching the scandium-rich product with an alkaline buffer solution to obtain a scandium-containing mixed solution, the method further includes:

[0046] S3, extracting the scandium-containing mixed solution with an organic solvent to obtain a scandium-containing organic phase;

[0047] S4, stripping the scandium-containing organic phase to obtain a scandium-containing rich solution and a recyclable organic phase; and

[0048] S5. Returning the recyclable organic phase to the organic solvent used for extraction for recycling.

[0049] In some embodiments, the volume ratio of the organic solvent to the scandium-containing mixed solution may be 0.5-5.

[0050] In some embodiments, the organic solvent may include an extractant and a diluent, wherein the extractant may be trioctyl tertiary amine and the diluent may be sulfonated kerosene.

[0051] In some embodiments, the volume fraction of the extractant in the organic solvent can be 1.00% to 5.00%. By controlling the volume fraction of the extractant in the organic solvent to be 1.00% to 5.00%, the extraction effect of scandium can be ensured. If the concentration of the extractant is too low, the extraction amount is limited, and the scandium in the scandium-containing mixed solution cannot be extracted into the organic phase to the greatest extent. If the concentration of the extractant is too high, the viscosity of the organic solvent is too high, the phase separation speed is slower, and emulsification occurs, affecting the efficiency of extraction and separation.

[0052] In some embodiments, the reagent used for stripping the scandium-containing organic phase is a hydrochloric acid solution, optionally with a concentration of 0.1 mol / L. In some embodiments, the recyclable organic phase is returned to the organic solvent used for extraction for recycling, thereby improving the utilization rate of the organic solvent and reducing costs.

[0053] The present disclosure will be further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the present disclosure only and are not intended to limit the scope of the present disclosure. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national standards. If no corresponding national standards are available, the methods were performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0054] Example 1

[0055] The main components and scandium content of the red mud used in this example are shown in Table 1.

[0056] Table 1 Test results of main components and scandium content of red mud

[0057] Iron minerals are removed from red mud through grading and magnetic separation, allowing scandium to be concentrated in the non-magnetic product, resulting in a scandium-rich product. The grading and screening equipment is a high-frequency vibrating screen with a mesh size of 74μm, and the magnetic separation equipment is a SLON high-gradient magnetic separator with a magnetic field strength of 0.3T.

[0058] The scandium-rich product obtained from red mud is leached using an alkaline buffer solution, allowing the scandium to enter the alkaline buffer solution. After filtration, a scandium-containing mixed solution is obtained. The alkaline buffer solution is a K2CO3 / KHCO3 buffer solution with a K2CO3:KHCO3 molar ratio of 1:5, a pH of 10, a weight ratio of the alkaline buffer solution to the scandium-rich product of 9, a leaching temperature of 30°C, and a leaching time of 180 minutes.

[0059] The elements in the scandium-containing mixed solution were tested, and the results are shown in Table 2.

[0060] Table 2 Test results of the scandium-containing mixed solution in Example 1

[0061] The resulting scandium-containing mixed solution is subjected to organic solvent extraction to obtain a scandium-containing organic phase. The scandium-containing organic phase is then stripped to obtain a scandium-containing rich solution and a recyclable organic phase. The recyclable organic phase is then returned to the organic solvent used for extraction for recycling. The extractant in the organic solvent is trioctyl tertiary amine, the diluent is sulfonated kerosene, the volume concentration of the extractant is 2%, and the volume ratio of the organic solvent to the scandium-containing mixed solution is 1:1. The stripping agent used for the scandium-containing organic phase is hydrochloric acid solution.

[0062] Example 2

[0063] Iron minerals are removed from red mud through grading and magnetic separation, concentrating scandium in the non-magnetic product to produce a scandium-enriched product. The grading and screening equipment uses a high-frequency vibrating screen with a mesh size of 62μm, while the magnetic separation equipment uses a SLON high-gradient magnetic separator with a magnetic field strength of 0.6T.

[0064] The scandium-rich product obtained from red mud is leached using an alkaline buffer solution, allowing the scandium to enter the alkaline buffer solution. After filtration, a scandium-containing mixed solution is obtained. The alkaline buffer solution is a Na2CO3 / NaHCO3 buffer solution with a Na2CO3:NaHCO3 molar ratio of 1:4, a pH of 9.5, a weight ratio of the alkaline buffer solution to the scandium-rich product of 10, a leaching temperature of 45°C, and a leaching time of 150 minutes.

[0065] The elements in the scandium-containing mixed solution were tested, and the results are shown in Table 3.

[0066] Table 3 Test results of the scandium-containing mixed solution in Example 2

[0067] The resulting scandium-containing mixed solution is subjected to organic solvent extraction to obtain a scandium-containing organic phase. The scandium-containing organic phase is then stripped to obtain a scandium-containing rich solution and a recyclable organic phase. The recyclable organic phase is then returned to the organic solvent used for extraction for recycling. The extractant in the organic solvent is trioctyl tertiary amine, the diluent is sulfonated kerosene, the volume concentration of the extractant is 2%, and the volume ratio of the organic solvent to the scandium-containing mixed solution is 1:1. The stripping agent used for the scandium-containing organic phase is hydrochloric acid solution.

[0068] Example 3

[0069] Iron minerals are removed from red mud through grading and magnetic separation, allowing scandium to be concentrated in the non-magnetic product, resulting in a scandium-enriched product. The grading and screening equipment is a high-frequency vibrating screen with a mesh size of 53μm, and the magnetic separation equipment is a SLON high-gradient magnetic separator with a magnetic field strength of 0.9T.

[0070] The scandium-rich product obtained from red mud is leached using an alkaline buffer solution, allowing the scandium to enter the alkaline buffer solution. After filtration, a scandium-containing mixed solution is obtained. The alkaline buffer solution is a Na2CO3 / NaHCO3 buffer solution with a Na2CO3:NaHCO3 molar ratio of 1:3, a pH of 9, a weight ratio of the alkaline buffer solution to the scandium-rich product of 5, a leaching temperature of 60°C, and a leaching time of 110 minutes.

[0071] The elements in the scandium-containing mixed solution were tested, and the results are shown in Table 4.

[0072] Table 4 Test results of the scandium-containing mixed solution in Example 3

[0073] The resulting scandium-containing mixed solution is subjected to organic solvent extraction to obtain a scandium-containing organic phase. The scandium-containing organic phase is then stripped to obtain a scandium-containing rich solution and a recyclable organic phase. The recyclable organic phase is then returned to the organic solvent used for extraction for recycling. The extractant in the organic solvent is trioctyl tertiary amine, the diluent is sulfonated kerosene, the volume concentration of the extractant is 2%, and the volume ratio of the organic solvent to the scandium-containing mixed solution is 1:1. The stripping agent used for the scandium-containing organic phase is hydrochloric acid solution.

[0074] Example 4

[0075] Iron minerals are removed from red mud through grading and magnetic separation, allowing scandium to be concentrated in the non-magnetic product, resulting in a scandium-enriched product. The grading and screening equipment is a high-frequency vibrating screen with a mesh size of 38μm, and the magnetic separation equipment is a SLON high-gradient magnetic separator with a magnetic field strength of 1.2T.

[0076] The scandium-rich product obtained from red mud is leached using an alkaline buffer solution, allowing the scandium to enter the alkaline buffer solution. After filtration, a scandium-containing mixed solution is obtained. The alkaline buffer solution is a Na2CO3 / NaHCO3 buffer solution with a Na2CO3:NaHCO3 molar ratio of 1:2, a pH of 8.5, a weight ratio of the alkaline buffer solution to the scandium-rich product of 7, a leaching temperature of 75°C, and a leaching time of 60 minutes.

[0077] The elements in the scandium-containing mixed solution were tested, and the results are shown in Table 5.

[0078] Table 5 Test results of the scandium-containing mixed solution in Example 4

[0079] The resulting scandium-containing mixed solution is subjected to organic solvent extraction to obtain a scandium-containing organic phase. The scandium-containing organic phase is then stripped to obtain a scandium-containing rich solution and a recyclable organic phase. The recyclable organic phase is then returned to the organic solvent used for extraction for recycling. The extractant in the organic solvent is trioctyl tertiary amine, the diluent is sulfonated kerosene, the volume concentration of the extractant is 2%, and the volume ratio of the organic solvent to the scandium-containing mixed solution is 1:1. The stripping agent used for the scandium-containing organic phase is hydrochloric acid solution.

[0080] Example 5

[0081] Iron minerals are removed from red mud through grading and magnetic separation, concentrating scandium in the non-magnetic product to produce a scandium-enriched product. The grading and screening equipment is a high-frequency vibrating screen with a mesh size of 23μm, and the magnetic separation equipment is a SLON high-gradient magnetic separator with a magnetic field strength of 1.5T.

[0082] The scandium-rich product obtained from red mud is leached using an alkaline buffer solution, allowing the scandium to enter the alkaline buffer solution. After filtration, a scandium-containing mixed solution is obtained. The alkaline buffer solution is a Na2CO3 / NaHCO3 buffer solution with a Na2CO3:NaHCO3 molar ratio of 1:1, a pH of 8, a weight ratio of the alkaline buffer solution to the scandium-rich product of 8, a leaching temperature of 95°C, and a leaching time of 30 minutes.

[0083] The elements in the scandium-containing mixed solution were tested, and the results are shown in Table 6.

[0084] Table 6 Test results of the scandium-containing mixed solution in Example 5

[0085] The resulting scandium-containing mixed solution is subjected to organic solvent extraction to obtain a scandium-containing organic phase. The scandium-containing organic phase is then stripped to obtain a scandium-containing rich solution and a recyclable organic phase. The recyclable organic phase is then returned to the organic solvent used for extraction for recycling. The extractant in the organic solvent is trioctyl tertiary amine, the diluent is sulfonated kerosene, the volume concentration of the extractant is 2%, and the volume ratio of the organic solvent to the scandium-containing mixed solution is 1:1. The stripping agent used for the scandium-containing organic phase is hydrochloric acid solution.

[0086] Comparative Example 1

[0087] The red mud used in this comparative example is the same as the red mud used in Example 1. The red mud was treated using a method disclosed in Chinese invention patent CN113716597A, which utilizes ammonia water from a coking plant to recover scandium from red mud. The elements in the obtained scandium oxide material were tested, and the results are shown in Table 7.

[0088] Table 7 Test results of comparative example 1

[0089] It can be seen that the test results of Example 1 are better than those of Comparative Example 1.

[0090] Comparative Example 2

[0091] The red mud used in this comparative example is the same as the red mud used in Example 2. The red mud is treated using a method for extracting and separating scandium disclosed in Chinese invention patent CN111961849A. The elements in the obtained scandium oxide are tested, and the results are shown in Table 8.

[0092] Table 8 Test results of comparative example 2

[0093] It can be seen that the test results of Example 2 are better than those of Comparative Example 2.

[0094] Comparative Example 3

[0095] The red mud used in this comparative example is the same as the red mud used in Example 3. The red mud was treated using a method disclosed in Chinese invention patent CN106480322A for extracting scandium from scandium-rich slag obtained by pretreatment of red mud. The elements in the obtained scandium-containing solution were tested, and the results are shown in Table 9.

[0096] Table 9 Test results of comparative example 3

[0097] It can be seen that the test results of Example 3 are better than those of Comparative Example 3.

[0098] Comparative Example 4

[0099] The red mud used in this comparative example is the same as the red mud used in Example 4. The red mud is treated using a red mud and titanium dioxide waste liquid treatment process disclosed in Chinese invention patent CN106756046A. The elements in the obtained scandium oxide product are tested, and the results are shown in Table 10.

[0100] Table 10 Test results of comparative example 4

[0101] It can be seen that the test results of Example 4 are better than those of Comparative Example 4.

[0102] Comparative Example 5

[0103] The red mud used in this comparative example is the same as the red mud used in Example 5. The red mud was treated using a method for enriching scandium from red mud disclosed in Chinese invention patent CN105331837A. The elements in the obtained scandium-containing filter residue were tested, and the results are shown in Table 11.

[0104] Table 11 Test results of comparative example 5

[0105] It can be seen that the test results of Example 5 are better than those of Comparative Example 5.

[0106] The comparison results of the test data obtained from Examples 1-5 and Comparative Examples 1-5 are shown in Table 12 below.

[0107] Table 12 Comparison of test data obtained from Examples 1-5 and Comparative Examples 1-5

[0108] As can be seen from Table 12 above, after treating the red mud in Examples 1-5 of the present disclosure, the scandium / iron leaching rate ratio, the scandium / aluminum leaching rate ratio, and the scandium / titanium leaching rate ratio are all better than those in the comparative example. In particular, the scandium / iron leaching rate ratio is much higher than that in the comparative example, making the subsequent separation of scandium and iron impurities easier. In addition, the examples can also remove more than 20% of the red mud through early pretreatment, reducing the subsequent red mud leaching process volume and saving costs.

[0109] The above technical solution provided by the embodiments of the present disclosure has the following advantages compared with the related art:

[0110] The method for extracting scandium from red mud provided in the disclosed embodiments uses a carbonate-bicarbonate buffer solution as an alkaline leaching agent. Scandium exists in red mud in the form of compounds, such as Sc(OH)3 and ScO(OH). In the milder alkaline carbonate / bicarbonate system, these compounds can be completely or partially decomposed and leached. This method avoids the problems of traditional acidic leaching agents, such as large dosages, co-leaching of impurities, interference with subsequent separation, and difficulty in handling waste acid. It also offers advantages such as low dosage and low cost.

[0111] The foregoing description is intended only to provide specific embodiments of the present disclosure, which will enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments shown herein, but rather to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A method for extracting scandium from red mud, comprising: Scandium-rich products are obtained from red mud; and, Leaching the scandium-rich product with an alkaline buffer solution to obtain a scandium-containing mixed solution; Wherein, the alkaline buffer solution is a mixed solution of carbonate and bicarbonate.

2. The method according to claim 1, wherein: The molar ratio of the carbonate to the bicarbonate is 1:1 to 1:

5.

3. The method according to claim 1 or 2, wherein: The alkaline buffer solution is a mixed solution of Na2CO3 and NaHCO3 or a mixed solution of K2CO3 and KHCO3.

4. The method according to claim 1, wherein: The leaching process parameters include: the weight ratio of the alkaline buffer solution to the red mud, the leaching temperature and the leaching time.

5. The method according to claim 4, wherein: The weight ratio of the alkaline buffer solution to the red mud is 5-10.

6. The method according to claim 1, wherein: The leaching process parameters include: the weight ratio of the alkaline buffer solution to the scandium-rich product, the leaching temperature and the leaching time.

7. The method according to claim 6, wherein: The weight ratio of the alkaline buffer solution to the scandium-rich product is 5-10.

8. The method according to any one of claims 4 to 7, wherein: The leaching temperature is 30° C. to 90° C., and / or the leaching time is 30 min to 180 min.

9. The method according to claim 1, wherein: The method of obtaining a scandium-rich product from red mud comprises: The red mud is graded, screened and magnetically separated to obtain scandium-rich products.

10. The method according to claim 9, wherein: The particle size of the graded screening is 23 μm to 74 μm.

11. The method according to claim 9, wherein: The magnetic field strength of the magnetic separation is 0.3T to 1.5T.

12. The method according to claim 1, wherein: After the step of leaching the scandium-rich product with an alkaline buffer solution to obtain a scandium-containing mixed solution, the method further includes: extracting the scandium-containing mixed solution with an organic solvent to obtain a scandium-containing organic phase; Stripping the scandium-containing organic phase to obtain a scandium-containing rich solution and a recoverable organic phase; The recyclable organic phase is returned to the organic solvent used in the extraction for recycling.

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