A method for recovering scandium from red mud

Abstract

The present invention discloses a method for recovering scandium from red mud, and relates to the technical field of non-ferrous metal smelting. The method for recovering scandium from red mud of the present invention comprises the processes of ball milling activation, acid leaching, extraction and stripping; firstly, a high-energy ball mill is used to mechanically activate the red mud, which can promote the full grinding of each component and improve the activity of the scandium element; the acid controls the pH so that the scandium element is selectively leached, while a small amount or very little leaching of elements such as iron, aluminum, and silicon in the activated red mud; and then, extraction and stripping are used to obtain recovered scandium with good purity and yield. The present invention realizes the high-selective leaching of scandium in red mud, and provides a good foundation for the subsequent deep purification and purification of scandium.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal smelting, and in particular to a method for recovering scandium from red mud. Background Art

[0002] At present, the processes for extracting scandium from red mud are mainly divided into hydrometallurgy and pyrometallurgy. Hydrometallurgy mainly uses high-concentration hydrochloric acid, sulfuric acid, and nitric acid to leach the scandium element in red mud. However, direct high-concentration acid leaching of red mud results in high acid consumption and poor treatment environment. In addition, the composition of the acid leaching solution is complex, and the subsequent separation of scandium from other metal ions will also become a major problem. The main principle of pyrometallurgy is to first roast and reduce the red mud to remove iron, and then extract alumina from the slag. The metal elements with higher content in the red mud, such as iron and aluminum, are separated and recovered, so that scandium is further enriched in the slag, and then the scandium in the residue is transferred to the solution by acid leaching. This method has the problems of long processing flow, high energy consumption and large equipment investment. In addition, it is inevitable to lose a part of scandium, resulting in a low comprehensive recovery rate of scandium and the generation of a large amount of waste gas causing secondary pollution.

[0003] The invention patent with the announcement number CN109642269B discloses a method for recovering scandium from red mud left over from alumina production, which includes re-slurrying the red mud, using an ion exchange adsorbent to absorb and leach scandium from the red mud slurry to obtain a scandium-rich ion exchanger and a scandium-poor slurry, desorbing the scandium with a sodium carbonate solution to obtain a desorbed ion exchanger and an industrially recovered scandium solution, returning the desorbed ion exchanger to the scandium adsorption and leaching stage, and transferring the industrially recovered scandium solution through sedimentation to obtain concentrated scandium. The invention can improve the recovery rate of scandium from red mud and improve the quality of industrially recovered scandium. The invention patent with announcement number CN110331289B discloses a method for recovering scandium and sodium sulfate from Bayer red mud, which includes the following steps: crushing and grinding the red mud, adding ammonium sulfate and mixing thoroughly; low-temperature first-stage roasting to salt the red mud with ammonium sulfate, followed by high-temperature second-stage roasting; activating the roasted product and subjecting it to multi-stage water leaching and water washing; selectively adsorbing scandium in the leachate and washing liquid with a porous silicon-based carrier adsorbent; evaporating and crystallizing the leachate after adsorption of scandium to obtain sodium sulfate; passing NH3 and SO3 gases generated during the roasting process into dilute sulfuric acid, evaporating and crystallizing to obtain ammonium sulfate for recycling; the residual heat of roasting is used for evaporation and crystallization of sodium sulfate and ammonium sulfate, and the water vapor during the evaporation process is returned to the leaching process for recycling. The method has high leaching rate and selectivity of scandium, and ammonium sulfate and water can be recycled. The invention patent with announcement number CN116024443B discloses a method for recovering metal scandium, comprising the following steps: leaching red mud after pretreatment to obtain a scandium-containing leaching solution; then extracting the scandium-containing leaching solution after mixing it with an extractant to obtain an extract; stripping the extract to obtain a stripping product. The present invention also extracts the scandium-containing leaching solution by selecting a composite extractant, and extracts the scandium ions by utilizing the strong binding force of P204 to the scandium ions; and P227 has good selectivity for the scandium ions, thereby separating the scandium ions from other metal ions, thereby further improving the extraction effect of the scandium ions; finally, the present invention further reduces the hydrophilicity of the scandium ions by using trioctyl tertiary amine, thereby further improving the extraction rate of the scandium ions; thereby ultimately improving the recovery rate of the scandium element.

[0004] In summary, the existing methods for recovering scandium from red mud still have technical problems such as long processing flow, high energy consumption, and large equipment investment, resulting in a low comprehensive recovery rate of scandium and the generation of a large amount of waste gas causing secondary pollution. Summary of the invention

[0005] The purpose of the present invention is to provide a method for recovering scandium from red mud, so as to solve the technical problems in the prior art of long processing flow, high energy consumption, large equipment investment, low comprehensive recovery rate of scandium, and generation of a large amount of waste gas causing secondary pollution.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for recovering scandium from red mud comprises the following steps:

[0008] S1, adding red mud into a high-energy ball mill for ball milling activation to obtain activated red mud;

[0009] S2, adding acid solution to the activated red mud, adjusting the pH to 1-6, leaching, and solid-liquid separation to obtain a scandium-containing leachate;

[0010] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract;

[0011] S4, stripping the extract to obtain recovered scandium.

[0012] Furthermore, the content of scandium oxide in the components of the red mud is greater than 0.004%.

[0013] Furthermore, in step S1, the rotation speed of the ball mill is 50-500 r / min, the ball-to-material ratio is 1:1-20:1, and the activation time is 0.5-24 h.

[0014] Furthermore, the acid solution in step S2 is a combination of one or more of hydrochloric acid, sulfuric acid, nitric acid, and oxalic acid, and the concentration of the acid solution is 5-20wt%.

[0015] Furthermore, the leaching temperature of step S2 is 25-100° C., the leaching stirring speed is 200-600 r / min, and the leaching time is 5-240 min.

[0016] Furthermore, the extractant in step S3 is composed of the following components in mass percentage: 0.6-0.9% P204, 1.2-1.8% P227, 0.3-0.5% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:3-5; the temperature of the mixed extraction is 20-30°C, and the time of the mixed extraction is 5-20min.

[0017] Furthermore, the extractant for stripping in step S4 is a sodium hydroxide solution with a concentration of 2-3 mol / L, the volume ratio of the extractant to the extract is 1:2-3, the stripping temperature is 20-30° C., and the stripping time is 5-20 min.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] 1. The method of recovering scandium from red mud of the present invention includes the process of ball milling activation, acid leaching, extraction and stripping; firstly, a high-energy ball mill is used to mechanically activate the red mud, which can promote the full grinding of each component and improve the activity of the scandium element; the acid controls the pH so that the scandium element is selectively leached, and a small amount or very little of the iron, aluminum, silicon and other elements in the activated red mud are leached; then, the scandium with good purity and yield is recovered by extraction and stripping. The present invention realizes the high-selective leaching of scandium in red mud, providing a good foundation for the subsequent deep purification and purification of scandium.

[0020] 2. During the acid leaching process, dilute acid is selected and the temperature is reasonably controlled, which is beneficial to the destruction of the mineral crystal structure, promotes the decomposition of scandium-bearing minerals, and significantly improves the leaching rate of scandium.

[0021] 3. Select the composite extraction of P204, P227 and 2-ethylhexyl diphenyl phosphate. P204 has a strong binding force to scandium ions, P227 has good selectivity to scandium ions, and 2-ethylhexyl diphenyl phosphate also has good selectivity to scandium ions, which further improves the extraction effect of scandium ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 The flowchart of the method for recovering scandium from red mud according to the present invention is shown. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1

[0026] See also Figure 1 As shown, a method for recovering scandium from red mud in this embodiment comprises the following steps:

[0027] S1. Add red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; the content of scandium oxide in the red mud is 0.1%; the speed of the ball mill is 200r / min, the ball-to-material ratio is 10:1, and the activation time is 5h;

[0028] S2. Add 10 wt% dilute hydrochloric acid to the activated red mud, adjust the pH to 3, leaching, and solid-liquid separation to obtain a scandium-containing leachate; the leaching temperature is 50° C., the leaching stirring speed is 400 r / min, and the leaching time is 60 min;

[0029] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract; the extractant is composed of the following components in mass percentage: 0.8% P204, 1.5% P227, 0.36% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:3.8; the temperature of the mixed extraction is 26°C, and the time of the mixed extraction is 15 minutes;

[0030] S4. The extract is stripped to obtain recovered scandium; the stripping agent is a sodium hydroxide solution with a concentration of 2.5 mol / L, the volume ratio of the stripping agent to the extract is 1:2.6, the stripping temperature is 30° C., and the stripping time is 16 min.

[0031] Example 2

[0032] See also Figure 1 As shown, a method for recovering scandium from red mud in this embodiment comprises the following steps:

[0033] S1. Add red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; the content of scandium oxide in the red mud is 0.08%; the speed of the ball mill is 400r / min, the ball-to-material ratio is 15:1, and the activation time is 12h;

[0034] S2. Add 8 wt% nitric acid to the activated red mud, adjust the pH to 4, leaching, and solid-liquid separation to obtain a scandium-containing leachate; the leaching temperature is 75° C., the leaching stirring speed is 500 r / min, and the leaching time is 100 min;

[0035] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract; the extractant is composed of the following components in mass percentage: 0.8% P204, 1.6% P227, 0.42% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:4.5; the temperature of the mixed extraction is 30°C, and the time of the mixed extraction is 16 minutes;

[0036] S4. The extract is stripped to obtain recovered scandium; the stripping agent is a sodium hydroxide solution with a concentration of 2.6 mol / L, the volume ratio of the stripping agent to the extract is 1:2.8, the stripping temperature is 30° C., and the stripping time is 12 min.

[0037] Example 3

[0038] See also Figure 1 As shown, a method for recovering scandium from red mud in this embodiment comprises the following steps:

[0039] S1. Add red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; the content of scandium oxide in the red mud is 0.07%; the speed of the ball mill is 160r / min, the ball-to-material ratio is 15:1, and the activation time is 3h;

[0040] S2. Add 12 wt% sulfuric acid to the activated red mud, adjust the pH to 5, leaching, and solid-liquid separation to obtain a scandium-containing leachate; the leaching temperature is 90° C., the leaching stirring speed is 350 r / min, and the leaching time is 160 min;

[0041] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract; the extractant is composed of the following components in mass percentage: 0.8% P204, 1.7% P227, 0.42% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:3.8; the temperature of the mixed extraction is 26°C, and the time of the mixed extraction is 18 minutes;

[0042] S4. The extract is stripped to obtain recovered scandium; the stripping agent is a 3 mol / L sodium hydroxide solution, the volume ratio of the stripping agent to the extract is 1:2.8, the stripping temperature is 22° C., and the stripping time is 16 min.

[0043] Example 4

[0044] See also Figure 1 As shown, a method for recovering scandium from red mud in this embodiment comprises the following steps:

[0045] S1. Add red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; the content of scandium oxide in the red mud is 0.13%; the speed of the ball mill is 300r / min, the ball-to-material ratio is 16:1, and the activation time is 20h;

[0046] S2. Add 20 wt% oxalic acid to the activated red mud, adjust the pH to 5, leaching, and solid-liquid separation to obtain a scandium-containing leachate; the leaching temperature is 45° C., the leaching stirring speed is 500 r / min, and the leaching time is 150 min;

[0047] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract; the extractant is composed of the following components in mass percentage: 0.82% P204, 1.7% P227, 0.46% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:4.5; the temperature of the mixed extraction is 30°C, and the time of the mixed extraction is 18 minutes;

[0048] S4. The extract is stripped to obtain recovered scandium; the stripping agent is a 3 mol / L sodium hydroxide solution, the volume ratio of the stripping agent to the extract is 1:2.8, the stripping temperature is 30°C, and the stripping time is 20 min.

[0049] Example 5

[0050] See also Figure 1 As shown, a method for recovering scandium from red mud in this embodiment comprises the following steps:

[0051] S1. Add red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; the content of scandium oxide in the red mud is 0.15%; the speed of the ball mill is 500r / min, the ball-to-material ratio is 18:1, and the activation time is 3h;

[0052] S2. Add 15 wt% oxalic acid to the activated red mud, adjust the pH to 6, and perform leaching and solid-liquid separation to obtain a scandium-containing leachate; the leaching temperature is 90° C., the leaching stirring speed is 600 r / min, and the leaching time is 200 min;

[0053] S3, adding an extractant to the scandium-containing leaching solution for mixed extraction to obtain an extract; the extractant is composed of the following components in mass percentage: 0.9% P204, 1.6% P227, 0.4% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leaching solution is 1:5; the temperature of the mixed extraction is 30°C, and the time of the mixed extraction is 12 minutes;

[0054] S4. The extract is stripped to obtain recovered scandium; the stripping agent is a sodium hydroxide solution with a concentration of 2.6 mol / L, the volume ratio of the stripping agent to the extract is 1:3, the stripping temperature is 26° C., and the stripping time is 18 min.

[0055] Comparative Example 1

[0056] The method for recovering scandium from red mud in this comparative example is different from that in Example 1 in that step S1 uses a hammer mill for pulverization and activation, and the activation time is 2 hours.

[0057] Comparative Example 2

[0058] The method for recovering scandium from red mud in this comparative example is different from that in Example 1 in that the extractant in step S3 is composed of the following components in percentage by mass: 0.8% P204, 1.5% P227, and the remainder is solvent kerosene.

[0059] Comparative Example 3

[0060] The method for recovering scandium from red mud in this comparative example is different from that in Example 1 in that the extractant for stripping in step S4 is a 2.5 mol / L potassium hydroxide solution.

[0061] Experimental example

[0062] The leaching rate of scandium in the scandium-containing leaching solution in step S2 in Examples 1-5 and Comparative Examples 1-3 and the recovery rate of scandium recovered in step S4 were tested. The specific test results are shown in the following table:

[0063]

[0064] It can be seen from the test results in the above table that the leaching rate of scandium and the recovery rate of scandium in the embodiments of the present invention are higher than those in the comparative examples, indicating that the process of ball milling activation, acid leaching, extraction, and stripping of the present invention can promote the highly selective leaching of scandium and achieve a good recovery effect. Since comparative example 1 changes the ball milling activation method, it is not conducive to the full grinding of each component and the improvement of the activity of scandium, and the leaching rate and recovery rate of scandium are significantly reduced. Since 2-ethylhexyl diphenyl phosphate is not added to the extractant component of comparative example 2, the selectivity and extraction effect of the extractant for scandium ions are reduced, and the leaching rate and recovery rate are reduced. Since the stripping extractant of comparative example 3 is replaced with potassium hydroxide, the stripping effect is not as good as that of sodium hydroxide solution.

[0065] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0066] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for recovering scandium from red mud, characterized in that: The following steps are involved: S1, adding red mud into a high-energy ball mill for ball milling activation to obtain activated red mud; S2, adding acid solution to the activated red mud, adjusting the pH to 1-6, leaching, and solid-liquid separation to obtain a scandium-containing leachate; S3, adding an extractant to the scandium-containing leachate for mixed extraction to obtain an extract; the extractant in step S3 is composed of the following components in mass percentage: 0.6-0.9% P204, 1.2-1.8% P227, 0.3-0.5% 2-ethylhexyl diphenyl phosphate, and the remainder is solvent kerosene; the volume ratio of the extractant to the scandium-containing leachate is 1:3-5; the temperature of the mixed extraction is 20-30°C, and the time of the mixed extraction is 5-20min; S4, stripping the extract to obtain recovered scandium.

2. A method for recovering scandium from red mud according to claim 1, characterized in that: Among the components of the red mud, the content of scandium oxide is greater than 0.004%.

3. The method for recovering scandium from red mud according to claim 1, characterized in that: In step S1, the rotation speed of the ball mill is 50-500 r / min, the ball-to-material ratio is 1:1-20:1, and the activation time is 0.5-24 h.

4. The method for recovering scandium from red mud according to claim 1, characterized in that: The acid solution in step S2 is a combination of one or more of hydrochloric acid, sulfuric acid, nitric acid, and oxalic acid, and the concentration of the acid solution is 5-20wt%.

5. The method for recovering scandium from red mud according to claim 1, characterized in that: The leaching temperature of step S2 is 25-100° C., the leaching stirring speed is 200-600 r / min, and the leaching time is 5-240 min.

6. The method for recovering scandium from red mud according to claim 1, characterized in that: The extractant for stripping in step S4 is a sodium hydroxide solution with a concentration of 2-3 mol / L, the volume ratio of the extractant to the extract is 1:2-3, the stripping temperature is 20-30° C., and the stripping time is 5-20 min.

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