Method for selectively leaching scandium from red mud

Abstract

Disclosed in the present disclosure is a method for selectively leaching scandium from red mud. The red mud contains scandium, and the method comprises: using an inorganic acid solution to pretreat red mud to obtain pretreated red mud slurry; and using a leaching agent to carry out selective leaching on the pretreated red mud slurry to obtain leached slurry, the leaching agent containing organic acid and metal inorganic salt, and the mass ratio of the organic acid to the metal inorganic salt being 0.00015-0.0500.

Description

A method for selectively leaching scandium from red mud Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202410419029.7, filed on April 9, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of solid waste resource recycling, and in particular to a method for selectively leaching scandium from red mud. BACKGROUND

[0003] Red mud is a solid waste generated in the production process of alumina, and 1 ton to 2 tons of red mud will be generated for every 1 ton of alumina produced in the existing alumina production process. However, the comprehensive utilization rate of red mud at the present stage is less than 10%, and the cumulative stockpile of red mud in China has reached 1.7 billion tons. Scandium is a typical rare earth element, which is widely distributed in bauxite used for alumina production. Scandium has wide application in the fields of luminescent materials, aerospace industry, alloys, and batteries. Existing research shows that, depending on the properties of bauxite and the processing technology, the content of scandium in red mud generated in the production process of alumina is between 0.004% and 0.01%. Due to the scarcity of scandium, if the content of scandium in the ore is between 0.002% and 0.005%, the ore is considered an important scandium resource. Therefore, if scandium resources can be extracted from red mud, not only the utilization rate of red mud can be improved, but also high economic benefits can be generated, thereby practicing the concept of turning waste into treasure.

[0004] However, the current method for extracting scandium elements from red mud is prone to doping impurity metal elements, so it is generally necessary to remove these impurity metal elements to improve the extraction rate of scandium. Although the specific treatment of these impurity metal elements can improve the purity of scandium, it is easy to cause loss of scandium and increase the operation process, thereby reducing the extraction rate of scandium. SUMMARY

[0005] The problem of how to improve the extraction rate of scandium elements in red mud is solved by using one or more embodiments of the present disclosure.

[0006] In a first aspect, a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure, the red mud containing scandium elements, can include: pretreating the red mud using an inorganic acid solution to obtain a pretreated red mud slurry; and selectively leaching the pretreated red mud slurry using a leaching agent to obtain a leaching slurry; wherein the leaching agent includes an organic acid and a metal inorganic salt, and the mass ratio of the organic acid to the metal inorganic salt is 0.00015 to 0.0500. BRIEF DESCRIPTION OF DRAWINGS

[0007] The accompanying drawings, which are incorporated herein and constitute part of the specification, illustrate embodiments consistent with the present disclosure and serve to explain the principles of the present disclosure together with the specification.

[0008] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or the related art, the accompanying drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings according to these drawings without any creative effort.

[0009] FIG. 1 shows a flowchart of a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure;

[0010] FIG. 2 shows a detailed flowchart of a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure;

[0011] FIG. 3 shows an actual flowchart of a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0012] In order to make the objects, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely below with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without any creative effort fall within the scope of the present disclosure.

[0013] Various embodiments of the present disclosure can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limit on the scope of the present disclosure; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has 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 described range, such as 1, 2, 3, 4, 5 and 6, which applies to any range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0014] In addition, in the description of the present disclosure, the terms "comprise", "contain" and the like mean "comprise but not limited to". In this paper, the association relationship of the associated objects is described, which means that there can be three kinds of relationships, for example, A and / or B can represent the following cases: A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. In this paper, "at least one" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0015] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased or prepared by existing methods. It should be noted that the current methods for extracting scandium elements from red mud include:

[0016] (1) First, use acid leaching to extract anti elements from red mud, and then remove iron in the acid leaching filtrate by sodium hydroxide to complete the extraction of scandium from red mud; However, this method uses acid leaching and adds sodium hydroxide at the same time, which causes the problems of low leaching rate of scandium and large loss of scandium in the extraction process of scandium.

[0017] (2) Use acid solution and composite scandium precipitating agent to leach, precipitate and separate scandium from red mud to complete the extraction of scandium from red mud; However, the amount of acid solution and the amount of composite scandium precipitating agent used in this method are too large, and the final scandium recovery rate is not high.

[0018] (3) Use a combination of pyrometallurgical and hydrometallurgical methods to enrich scandium from red mud to complete the extraction of scandium from red mud; The energy consumption of this method is high and the process is complex.

[0019] Therefore, how to provide a method for selectively leaching scandium from red mud to solve the technical problem of low extraction rate of scandium in extracting scandium from red mud.

[0020] Figure 1 shows a method flow diagram for selectively leaching scandium from red mud according to some embodiments of the present disclosure;

[0021] As shown in Figure 1, the method for selectively leaching scandium from red mud according to some embodiments of the present disclosure, the red mud contains scandium elements, the method comprises:

[0022] S1. Pre-treating the red mud with an inorganic acid solution to obtain a pre-treated red mud slurry; and,

[0023] S2. Selectively leaching the pre-treated red mud slurry with a leaching agent to obtain a leaching slurry;

[0024] The leaching agent comprises an organic acid and a metallic inorganic salt, and the mass ratio of the organic acid to the metallic inorganic salt is 0.00015-0.0500.

[0025] In some embodiments, the mass ratio of the organic acid to the metallic inorganic salt can be 0.00015-0.0500, which can facilitate the organic acid of the leaching agent to sufficiently combine with the scandium element in the red mud slurry to generate a scandium compound, and also can facilitate the metallic inorganic salt of the leaching agent to sufficiently combine with the impurity elements such as Fe and Al in the red mud slurry to avoid chemical reactions between the impurity elements such as Fe and Al and the scandium element, so that the leaching slurry contains sufficient scandium element.

[0026] In some embodiments, the mass ratio of the organic acid to the metallic inorganic salt can be 0.00015, 0.00030, 0.00050, 0.00100, 0.00200, 0.00300, 0.00400, 0.00500, 0.01000, 0.02000, 0.03000, 0.0400 or 0.0500.

[0027] It should be noted that the red mud can be a red mud filter cake or dry red mud powder.

[0028] In some optional embodiments, the mass ratio of the amount of the organic acid to the dry base weight of the red mud is 0.002%-0.0500%, and the mass ratio of the amount of the metallic inorganic salt to the dry base weight of the red mud is 1%-15%.

[0029] In some embodiments, the mass ratio of the amount of the organic acid to the dry base weight of the red mud can be 0.002%-0.0500%, which is to facilitate the organic acid of the leaching agent to sufficiently combine with the scandium element in the pre-treated red mud slurry to generate a scandium compound that is easy to dissolve; and the mass ratio of the amount of the metallic inorganic salt to the dry base weight of the red mud can be 1%-15%, which is to facilitate the metallic inorganic salt of the leaching agent to sufficiently combine with the impurity elements such as Fe and Al in the pre-treated red mud slurry to avoid chemical reactions between the impurity elements such as Fe and Al and the scandium element, so that the leaching slurry contains sufficient scandium element.

[0030] In some embodiments, the amount of the organic acid used can be 0.002%, 0.004%, 0.006%, 0.008%, 0.010%, 0.012%, 0.014%, 0.016%, 0.018%, 0.020%, 0.022%, 0.024%, 0.026%, 0.028%, 0.030%, 0.032%, 0.034%, 0.036%, 0.038%, 0.040%, 0.042%, 0.044%, 0.046%, 0.048%, or 0.05000% of the dry basis weight of the red mud.

[0031] In some embodiments, the amount of the metal inorganic salt used can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 3%, 4%, 5% of the dry basis weight of the red mud.

[0032] It should be noted that the mass ratio of the amount of the organic acid used to the dry basis weight of the red mud can be 0.005% to 0.02%, and the mass ratio of the amount of the metal inorganic salt used to the dry basis weight of the red mud can be 2.5% to 7.5%.

[0033] In some alternative embodiments, the organic acid comprises at least one of:

[0034] oxalic acid, citric acid, and succinic acid.

[0035] The metal inorganic salt comprises at least one of:

[0036] iron sulfate, magnesium sulfate, iron chloride, magnesium chloride, and ferrous sulfate.

[0037] In some embodiments, the organic acid can comprise at least one of oxalic acid, citric acid, and succinic acid, so as to promote chemical reaction between the organic acid of the leaching agent and scandium elements in the pretreated red mud slurry to generate a soluble scandium-containing compound; and the metal inorganic salt can comprise at least one of iron sulfate, magnesium sulfate, iron chloride, magnesium chloride, and ferrous sulfate, so as to promote chemical reaction between the metal inorganic salt of the leaching agent and impurity elements such as Fe and Al in the pretreated red mud slurry, so as to avoid chemical reaction between the impurity elements such as Fe and Al and the scandium elements, thereby making the leaching slurry contain sufficient scandium elements.

[0038] In some alternative embodiments, the temperature of the selective leaching is 50°C to 120°C, and the time of the selective leaching is 15 min to 90 min.

[0039] In some embodiments, the temperature of the selective leaching can be 50-120°C, and the time of the selective leaching can be 15-90 min, so as to promote the organic acid of the leaching agent to sufficiently combine with the scandium element in the pretreated red mud slurry, and the metal inorganic salt of the leaching agent to sufficiently combine with the impurity elements such as Fe and Al in the pretreated red mud slurry, so as to avoid chemical reaction between the impurity elements such as Fe and Al and the scandium element, thereby making the leaching slurry contain sufficient scandium element.

[0040] In some embodiments, the temperature of the selective leaching can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C.

[0041] In some embodiments, the time of the selective leaching can be 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min or 90 min.

[0042] It should be noted that, in some embodiments, the temperature of the selective leaching can be 60-90°C, and the time of the selective leaching can be 30-45 min.

[0043] FIG. 2 exemplarily shows a detailed flowchart of a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure;

[0044] As shown in FIG. 2, in some optional embodiments, the pretreatment of the red mud using the inorganic acid solution to obtain the pretreated red mud slurry comprises the following steps:

[0045] S101. mechanically activating the red mud to obtain activated red mud;

[0046] S102. using the inorganic acid solution to perform slurry treatment on the activated red mud to obtain the pretreated red mud slurry.

[0047] In some embodiments, the pretreatment can comprise mechanical activation of the red mud, and the mechanical activation is used in the pretreatment to convert the large-particle red mud into fine-particle red mud, and the chemical elements of the red mud can be activated in the mechanical activation process to obtain the activated red mud; the pretreatment can also comprise using the inorganic acid solution to perform slurry treatment on the activated red mud, so as to acidify the activated red mud using the inorganic acid solution, thereby obtaining the pretreated red mud slurry which is sufficiently acidified.

[0048] In some optional embodiments, the liquid-solid ratio of the inorganic acid solution to the activated red mud is (4-20):1.

[0049] In some embodiments, the liquid to solid ratio of the inorganic acid solution to the activated red mud can be (4-20): 1, in order to acidify the activated red mud using the inorganic acid solution to obtain a pre- treated red mud slurry that is sufficiently acidified.

[0050] In some embodiments, the liquid to solid ratio of the inorganic acid solution to the activated red mud can be 4: 1, 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, 10: 1, 11: 1, 12: 1, 13: 1, 14: 1 or 15: 1.

[0051] In some alternative embodiments, the particle size of the activated red mud is < 178 μm.

[0052] In some embodiments, the particle size of the activated red mud can be < 178 μm, in order to facilitate the particles of the activated red mud to have a sufficiently large specific surface area, which can enable the inorganic acid solution to mix the activated red mud sufficiently to obtain a pre-treated red mud slurry that is sufficiently acidified.

[0053] It is to be noted that in some embodiments, the red mud can be ground using a ball mill or pulverized using a pulverizer to facilitate the particle size of the activated red mud to be < 178 μm.

[0054] In some alternative embodiments, the temperature of the slurrying treatment is 50°C to 120°C, the time of the slurrying treatment is 5 min to 60 min, and the target pH of the slurrying treatment is 0.5 to 3.5.

[0055] In some embodiments, the temperature of the slurrying treatment can be 50°C to 120°C, the time of the slurrying treatment can be 5 min to 60 min, and the target pH of the slurrying treatment can be 0.5 to 3.5, in order to enable the inorganic acid solution to mix the activated red mud sufficiently to obtain a pre-treated red mud slurry that is sufficiently acidified.

[0056] In some embodiments, the temperature of the slurrying treatment can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C.

[0057] In some embodiments, the time of the slurrying treatment can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min.

[0058] In some embodiments, the target pH of the slurrying treatment can be 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5.

[0059] It should be noted that in some embodiments, the temperature of the sizing treatment can be 50-120°C, the time of the sizing treatment can be 5-60 minutes, and the target pH of the sizing treatment can be 0.5-3.5.

[0060] In some alternative embodiments, the inorganic acid solution comprises a sulfuric acid solution and / or a hydrochloric acid solution.

[0061] In some embodiments, the inorganic acid solution can comprise a sulfuric acid solution and / or a hydrochloric acid solution, so as to use the inorganic acid solution to sufficiently mix with the activated red mud, so that a pre-processed red mud slurry that is sufficiently acidified can be obtained.

[0062] FIG. 3 exemplarily shows a practical flowchart of a method for selectively leaching scandium from red mud according to some embodiments of the present disclosure.

[0063] As shown in FIG. 3, in some alternative embodiments, after the step of using a leaching agent to selectively leach the pre-processed red mud slurry to obtain a leaching slurry, the method further comprises the following steps:

[0064] S3. performing solid-liquid separation on the leaching slurry to obtain a scandium-rich leaching solution and a scandium-extracted red mud residue, respectively;

[0065] S4. performing scandium separation on the scandium-rich leaching solution to obtain a scandium-lean solution and a scandium product, respectively;

[0066] S5. washing the scandium-extracted red mud residue, and then filtering the scandium-extracted red mud residue to obtain a harmless red mud and a washing solution, respectively;

[0067] The scandium-lean solution and the washing solution are returned to the step of using an inorganic acid solution to pre-treat the red mud, so as to pre-treat the red mud.

[0068] In some embodiments, the method can comprise returning the scandium-lean solution and the washing solution to the step of using an inorganic acid solution to pre-treat the red mud, i.e., mixing the scandium-lean solution and the washing solution with the inorganic acid or the inorganic acid solution to pre-treat the red mud, so as to realize recycling of water resources, thereby reducing water resource consumption of the method.

[0069] The present disclosure will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present disclosure and are not used to limit the scope of the present disclosure. The experimental methods in the following examples, if no specific conditions are indicated, are generally determined according to industry standards. If there is no corresponding industry standard, the general international standards, conventional conditions, or the conditions suggested by the manufacturers are used.

[0070] Example 1

[0071] As shown in Figure 3, a method for selectively leaching scandium from red mud containing scandium elements, comprising:

[0072] S101. mechanically activating the red mud to obtain activated red mud;

[0073] S102. performing slurry treatment on the activated red mud using an inorganic acid solution to obtain a pretreated red mud slurry;

[0074] S2. performing selective leaching on the pretreated red mud slurry using a leaching agent to obtain a leaching slurry;

[0075] S3. performing solid-liquid separation on the leaching slurry to obtain a scandium-rich leaching liquid and a scandium-extracted red mud residue, respectively;

[0076] S4. performing scandium separation on the scandium-rich leaching liquid to obtain a scandium-lean liquid and a scandium product, respectively;

[0077] S5. performing washing on the scandium-extracted red mud residue, and then performing filtration on the scandium-extracted red mud residue to obtain a harmless red mud and a washing liquid, respectively;

[0078] wherein the scandium-lean liquid and the washing liquid are returned to the pretreatment of the red mud using the inorganic acid solution. The mass ratio of the amount of the organic acid to the dry base weight of the red mud is 0.005%, and the mass ratio of the amount of the metal inorganic salt to the dry base weight of the red mud is 2.5%. The chemical composition of the red mud is shown in Table 1.

[0079] Table 1 Chemical composition of red mud

[0080] The organic acid is oxalic acid.

[0081] The metal inorganic salt is magnesium sulfate.

[0082] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 min.

[0083] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 6:1.

[0084] The particle size of the activated red mud is < 178 μm.

[0085] The temperature of the slurry treatment is 60°C, the time of the slurry treatment is 10 min, and the target pH of the slurry treatment is 3.0.

[0086] The inorganic acid solution is a hydrochloric acid solution.

[0087] Example 2

[0088] The content disclosed in Example 1 is modified as follows:

[0089] The amount of the organic acid and the mass ratio of the dry base weight of the red mud are 0.005%, and the amount of the metal inorganic salt and the mass ratio of the dry base weight of the red mud are 2.5%.

[0090] The organic acid is oxalic acid.

[0091] The metal inorganic salt is magnesium sulfate.

[0092] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 min.

[0093] The liquid-solid ratio of the inorganic acid solution and the activated red mud is 8:1.

[0094] The temperature of the slurry treatment is 60°C, the time of the slurry treatment is 15 min, and the target pH of the slurry treatment is 2.5.

[0095] The inorganic acid solution is a sulfuric acid solution.

[0096] Example 3

[0097] The following changes are made to the disclosure of Example 1:

[0098] The amount of the organic acid and the mass ratio of the dry base weight of the red mud are 0.005%, and the amount of the metal inorganic salt and the mass ratio of the dry base weight of the red mud are 2.5%.

[0099] The organic acid is oxalic acid.

[0100] The metal inorganic salt is magnesium sulfate.

[0101] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 min.

[0102] The liquid-solid ratio of the inorganic acid solution and the activated red mud is 8:1.

[0103] The temperature of the slurry treatment is 60°C, the time of the slurry treatment is 30 min, and the target pH of the slurry treatment is 2.5.

[0104] The inorganic acid solution is a sulfuric acid solution.

[0105] Example 4

[0106] The following changes are made to the disclosure of Example 1:

[0107] The amount of the organic acid and the mass ratio of the dry base weight of the red mud are 0.01%, and the amount of the metal inorganic salt and the mass ratio of the dry base weight of the red mud are 2.5%.

[0108] The organic acid is citric acid.

[0109] The metal inorganic salt is iron sulfate.

[0110] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 minutes.

[0111] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 8:1.

[0112] The temperature of the slurry treatment is 80°C, the time of the slurry treatment is 15 minutes, and the target pH of the slurry treatment is 2.5.

[0113] The inorganic acid solution is a sulfuric acid solution.

[0114] Example 5

[0115] The content disclosed in Example 1 is modified as follows:

[0116] The mass ratio of the amount of the organic acid to the dry basis weight of the red mud is 0.01%, and the mass ratio of the amount of the metal inorganic salt to the dry basis weight of the red mud is 5.0%.

[0117] The organic acid is succinic acid.

[0118] The metal inorganic salt is a mixture of ferric chloride and magnesium chloride, and the mass ratio of the ferric chloride to the magnesium chloride is 1:1.

[0119] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 minutes.

[0120] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 8:1.

[0121] The temperature of the slurry treatment is 80°C, the time of the slurry treatment is 15 minutes, and the target pH of the slurry treatment is 2.0.

[0122] The inorganic acid solution is a sulfuric acid solution.

[0123] Example 6

[0124] The content disclosed in Example 1 is modified as follows:

[0125] The mass ratio of the amount of the organic acid to the dry basis weight of the red mud is 0.015%, and the mass ratio of the amount of the metal inorganic salt to the dry basis weight of the red mud is 7.5%.

[0126] The organic acid is oxalic acid.

[0127] The metal inorganic salt is a mixture of ferric sulfate and ferrous sulfate, and the mass ratio of the ferric sulfate to the ferrous sulfate is 1:2.

[0128] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 minutes.

[0129] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 8:1.

[0130] The temperature of the slurry adjustment treatment is 80°C, the time of the slurry adjustment treatment is 15 minutes, and the target pH of the slurry adjustment treatment is 2.2.

[0131] The inorganic acid solution is a sulfuric acid solution.

[0132] Example 7

[0133] The following modifications are made to the disclosure of Example 1:

[0134] The mass ratio of the amount of the organic acid to the dry basis weight of the red mud is 0.015%, and the mass ratio of the amount of the metal inorganic salt to the dry basis weight of the red mud is 7.5%.

[0135] The organic acid includes oxalic acid.

[0136] The metal inorganic salt is iron sulfate and ferrous sulfate, and the mass ratio of the iron sulfate to the ferrous sulfate is 1:2.

[0137] The temperature of the selective leaching is 75°C, and the time of the selective leaching is 45 minutes.

[0138] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 8:1.

[0139] The temperature of the slurry adjustment treatment is 80°C, the time of the slurry adjustment treatment is 15 minutes, and the target pH of the slurry adjustment treatment is 2.5.

[0140] The inorganic acid solution is a sulfuric acid solution.

[0141] Example 8

[0142] The following modifications are made to the disclosure of Example 1:

[0143] The mass ratio of the amount of the organic acid to the dry basis weight of the red mud is 0.015%, and the mass ratio of the amount of the metal inorganic salt to the dry basis weight of the red mud is 7.5%.

[0144] The organic acid is oxalic acid.

[0145] The metal inorganic salt is iron sulfate and ferrous sulfate, and the mass ratio of the iron sulfate to the ferrous sulfate is 1:2.

[0146] The temperature of the selective leaching is 85°C, and the time of the selective leaching is 60 minutes.

[0147] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 8:1.

[0148] The temperature of the slurry adjustment treatment is 80°C, the time of the slurry adjustment treatment is 15 minutes, and the target pH of the slurry adjustment treatment is 2.5.

[0149] The inorganic acid solution is a sulfuric acid solution.

[0150] Example 9

[0151] The content disclosed in Example 1 was modified as follows:

[0152] The mass ratio of the amount of the organic acid to the dry base weight of the red mud was 0.015%, and the mass ratio of the amount of the metal inorganic salt to the dry base weight of the red mud was 5%.

[0153] The organic acid was oxalic acid.

[0154] The metal inorganic salt was ferrous sulfate.

[0155] The temperature of the selective leaching was 90°C, and the time of the selective leaching was 60 min.

[0156] The liquid-solid ratio of the inorganic acid solution to the activated red mud was 8:1.

[0157] The temperature of the slurry treatment was 80°C, the time of the slurry treatment was 15 min, and the target pH of the slurry treatment was 2.5.

[0158] The inorganic acid solution was a sulfuric acid solution.

[0159] Example 10

[0160] The content disclosed in Example 1 was modified as follows:

[0161] The mass ratio of the amount of the organic acid to the dry base weight of the red mud was 0.010%, and the mass ratio of the amount of the metal inorganic salt to the dry base weight of the red mud was 7.5%.

[0162] The organic acid was a mixture of oxalic acid and citric acid, and the mass ratio of the oxalic acid to the citric acid was 1:1.

[0163] The metal inorganic salt was a mixture of iron sulfate and magnesium sulfate, and the mass ratio of the iron sulfate to the magnesium sulfate was 1:2.

[0164] The temperature of the selective leaching was 85°C, and the time of the selective leaching was 60 min.

[0165] The liquid-solid ratio of the inorganic acid solution to the activated red mud was 8:1.

[0166] The temperature of the slurry treatment was 80°C, the time of the slurry treatment was 20 min, and the target pH of the slurry treatment was 2.5.

[0167] The inorganic acid solution was a sulfuric acid solution.

[0168] Example 11

[0169] The content disclosed in Example 1 was modified as follows:

[0170] The mass ratio of the amount of the organic acid to the dry base weight of the red mud is 0.02%, and the mass ratio of the amount of the metal inorganic salt to the dry base weight of the red mud is 7.5%.

[0171] The organic acid is a mixture of oxalic acid and citric acid, and the mass ratio of the oxalic acid to the citric acid is 1:1.

[0172] The metal inorganic salt is a mixture of iron sulfate and magnesium sulfate, and the mass ratio of the iron sulfate to the magnesium sulfate is 1:2.

[0173] The temperature of the selective leaching is 85°C, and the time of the selective leaching is 60 min.

[0174] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 12:1.

[0175] The temperature of the slurry treatment is 80°C, the time of the slurry treatment is 20 min, and the target pH of the slurry treatment is 2.5.

[0176] The inorganic acid solution is a sulfuric acid solution.

[0177] Comparative Example 1

[0178] The following changes are made to the disclosure of Example 1:

[0179] The leaching agent is not used.

[0180] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 min.

[0181] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 6:1.

[0182] The temperature of the slurry treatment is 60°C, the time of the slurry treatment is 10 min, and the target pH of the slurry treatment is 3.0.

[0183] The inorganic acid solution is a sulfuric acid solution.

[0184] Comparative Example 2

[0185] The following changes are made to the disclosure of Example 1:

[0186] The leaching agent only uses the organic acid.

[0187] The mass ratio of the amount of the organic acid to the dry base weight of the red mud is 0.005%.

[0188] The organic acid is oxalic acid.

[0189] The temperature of the selective leaching is 60°C, and the time of the selective leaching is 30 min.

[0190] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 6:1.

[0191] The temperature of the slurry conditioning treatment is 60℃, the time of the slurry conditioning treatment is 10min, and the target pH of the slurry conditioning treatment is 3.0.

[0192] The inorganic acid solution is a sulfuric acid solution.

[0193] Comparative Example 3

[0194] The following modifications are made to the disclosure of Example 1:

[0195] The leaching agent only uses a metal inorganic salt.

[0196] The mass ratio of the amount of the metal inorganic salt to the dry weight of the red mud is 2.5%.

[0197] The metal inorganic salt is magnesium sulfate.

[0198] The temperature of the selective leaching is 60℃, and the time of the selective leaching is 30min.

[0199] The liquid-solid ratio of the inorganic acid solution to the activated red mud is 6:1.

[0200] The temperature of the slurry conditioning treatment is 60℃, the time of the slurry conditioning treatment is 10min, and the target pH of the slurry conditioning treatment is 3.0.

[0201] The inorganic acid solution is a sulfuric acid solution.

[0202] Related experiments and effect data:

[0203] The concentrations of scandium ions and iron ions in the leaching slurry obtained in each example and comparative example are detected, and the leaching rates of scandium ions and iron ions are calculated, and the results are shown in Table 2.

[0204] The calculation formula of the leaching rate is:

[0205]

[0206] In the formula, μ1 is the leaching rate of scandium ions, S0 is the scandium ion content in the dry basis of the red mud, and S is the scandium ion content in the harmless red mud.

[0207]

[0208] In the formula, μ2 is the leaching rate of iron ions, F0 is the iron ion content in the dry basis of the red mud, and S is the iron ion content in the harmless red mud.

[0209] Table 2: Leaching rates of scandium ions and iron ions in each example and comparative example

[0210] As shown in Table 2, according to the method for selectively leaching scandium from the red mud according to some embodiments of the present disclosure, the leaching agent contains the organic acid and the metal inorganic salt, the organic acid can chemically react with the scandium element in the pretreated red mud slurry to generate a soluble scandium-containing compound, at the same time, the metal inorganic salt can chemically react with the impurity elements such as Fe and Al in the red mud slurry to avoid the chemical reaction between the impurity elements such as Fe and Al and the scandium element, so that the leaching slurry contains sufficient scandium element; the mass ratio of the organic acid and the metal inorganic salt is 0.00015-0.0500, which can promote the sufficient chemical reaction between the organic acid and the scandium element, and also promote the chemical reaction between the metal inorganic salt and the impurity elements such as Fe and Al in the red mud slurry, so as to further dissolve the scandium element in the leaching slurry; the method can selectively leach the scandium element in the red mud based on the synergistic effect of the organic acid and the metal inorganic salt in the leaching agent, so as to finally promote the leaching rate of the scandium in the red mud to be above 85%, and the leaching rate of the iron in the red mud is below 1.5%, and therefore the method can improve the extraction rate of the scandium in the red mud.

[0211] According to the method for selectively leaching scandium from the red mud according to some embodiments of the present disclosure, the method selectively leaches the scandium element in the pretreated red mud slurry by using the leaching agent, so as to improve the extraction rate of the scandium in the red mud, thereby improving the recycling value and considerable additional value of the red mud, and at the same time, the method also realizes the harmless utilization of the red mud and reduces the environmental risk caused by the stockpiled red mud.

[0212] According to the method for selectively leaching scandium from the red mud according to some embodiments of the present disclosure, the scandium-lean liquid and the washing liquid are returned to the pretreatment of the red mud by using the inorganic acid solution, so as to recycle the scandium-lean liquid and the washing liquid, to realize the recycling of the water resources in the scandium-lean liquid and the washing liquid; at the same time, compared with the scandium extraction process of the red mud in the related art, the method only uses the steps of pretreatment, selective leaching, solid-liquid separation and scandium separation, so as to improve the leaching rate of the scandium in the red mud and improve the simplicity of the scandium extraction process of the red mud.

[0213] According to the method for selectively leaching scandium from the red mud according to some embodiments of the present disclosure, compared with the related art, the method has the following advantages:

[0214] The method for selectively leaching scandium from red mud containing scandium elements according to some embodiments of the present disclosure comprises: pre-treating the red mud using an inorganic acid solution to obtain a pre-treated red mud slurry; and selectively leaching the pre-treated red mud slurry using a leaching agent to obtain a leaching slurry; wherein the leaching agent comprises an organic acid and a metal inorganic salt, and the mass ratio of the organic acid to the metal inorganic salt is 0.00015-0.0500. The inorganic acid solution can be used to acidize the pre-treatment of the red mud, which can remove impurities such as alkaline substances on the one hand, and adjust the pH of the red mud on the other hand; the leaching agent contains the organic acid and the metal inorganic salt, the organic acid can chemically react with the scandium elements in the pre-treated red mud slurry to generate a soluble scandium-containing compound; at the same time, the metal inorganic salt can chemically react with impurity elements such as Fe and Al in the red mud slurry to avoid chemical reactions between the impurity elements such as Fe and Al and the scandium elements, so that the leaching slurry contains sufficient scandium elements; the mass ratio of the organic acid to the metal inorganic salt is 0.00015-0.0500, which can promote the organic acid to fully chemically react with the scandium elements; at the same time, it can also promote the metal inorganic salt to chemically react with the impurity elements such as Fe and Al in the red mud slurry to further dissolve the scandium elements in the leaching slurry, thereby solving the technical problem of low extraction rate of scandium elements in the related art.

[0215] The above description is merely that of the specific embodiments of the present disclosure, which enables a person skilled in the art to understand or 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 can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for selectively leaching scandium from red mud, wherein the red mud contains scandium, the method comprising: pretreating the red mud with an inorganic acid solution to obtain a pretreated red mud slurry; and, selectively leaching the pretreated red mud slurry using a leaching agent to obtain a leached slurry; Wherein, the leaching agent includes an organic acid and a metal inorganic salt, and the mass ratio of the organic acid to the metal inorganic salt is 0.00015 to 0.0500.

2. The method according to claim 1, wherein The mass ratio of the amount of the organic acid to the dry weight of the red mud is 0.002% to 0.0500%, and the mass ratio of the amount of the metal inorganic salt to the dry weight of the red mud is 1% to 15%.

3. The method according to claim 1 or 2, wherein: The organic acid comprises at least one of the following: oxalic acid, citric acid, and succinic acid; The metal inorganic salt comprises at least one of the following: Ferric sulfate, magnesium sulfate, ferric chloride, magnesium chloride and ferrous sulfate.

4. The method according to claim 1, wherein The temperature of the selective leaching is 50° C. to 120° C., and the time of the selective leaching is 15 min to 90 min.

5. The method according to claim 1, wherein The method of pretreating the red mud with an inorganic acid solution to obtain a pretreated red mud slurry comprises the following steps: Mechanically activating the red mud to obtain activated red mud; The activated red mud is subjected to slurry conditioning treatment using an inorganic acid solution to obtain a pretreated red mud slurry.

6. The method according to claim 5, wherein: The liquid-to-solid ratio of the inorganic acid solution to the activated red mud is (4-20):

1.

7. The method according to claim 5, wherein: The particle size of the activated red mud is less than 178 μm.

8. The method according to claim 5, wherein The temperature of the slurry adjustment treatment is 50° C. to 120° C., the time of the slurry adjustment treatment is 5 min to 60 min, and the target pH value of the slurry adjustment treatment is 0.5 to 3.

5.

9. The method according to claim 5, wherein: The inorganic acid solution includes a sulfuric acid solution and / or a hydrochloric acid solution.

10. The method according to claim 1, wherein After the step of selectively leaching the pretreated red mud slurry using a leaching agent to obtain a leached slurry, the method further includes the following steps: performing solid-liquid separation on the leaching slurry to obtain scandium-rich leaching solution and scandium-extracted red mud residue respectively; Separating scandium from the scandium-rich leachate to obtain a scandium-depleted solution and a scandium product; Washing the scandium-extracted red mud residue, and then filtering the scandium-extracted red mud residue to obtain harmless red mud and washing liquid respectively; The scandium-depleted solution and the washing solution are returned to the process of pretreating the red mud with an inorganic acid solution, so as to pretreat the red mud.

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