Method for recovering scandium and titanium from Bayer process red mud

Abstract

The invention discloses a method for recovering scandium and titanium from Bayer process red mud. The method comprises the following steps: (1) drying the red mud; (2) mixing the dried red mud and phosphoric acid, performing acid leaching reaction, and then filtering and drying to obtain pretreated red mud; (3) carrying out acid leaching on the pretreated red mud by adopting a phosphoric acid-hydrogen peroxide system, and carrying out solid-liquid separation to obtain red mud leachate containing scandium and titanium and iron-rich leaching residues; (4) mixing the red mud lixivium containing scandium and titanium with a P204 extracting agent, stirring, oscillating and carrying out oil-water separation to obtain a scandium-loaded organic phase and a titanium-containing lixivium, and carrying out acid pickling on the organic phase for multiple times; and (5) adding ammonia water into the titanium leachate to adjust the pH value, heating and stirring, standing and precipitating to obtain amorphous titanium phosphate, and carrying out acid pickling after solid-liquid separation. According to the method, scandium and titanium in the red mud are separated and recycled in a two-stage acid leaching-extraction-precipitation combined mode. The selectivity of scandium and titanium is improved. And technical support is provided for recovery of scandium and titanium and comprehensive utilization of red mud.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource recycling, and in particular to a method for recovering scandium and titanium from Bayer process red mud. Background Art

[0002] Red mud is a solid waste generated during the refining process of alumina. At present, the comprehensive utilization rate of red mud in my country is low, and it is mainly disposed of in the form of stockpiling. Red mud contains impurities, is highly alkaline, and contains a certain amount of heavy metals and radioactive substances. Large-scale stockpiling of red mud occupies a large area of ​​land and is prone to cause a series of environmental problems such as soil salinization, groundwater pollution, dust, and dam leakage and dam collapse crises. Red mud is rich in elements such as iron, aluminum, scandium, titanium and other rare and precious metals, mainly in the form of oxides. Recovering valuable components such as iron, alkali, alumina, and scattered metals and rare and precious metals from red mud is an effective way to achieve the resource utilization, reduction and harmlessness of red mud.

[0003] The content of scandium in red mud is generally between 60 and 120 mg / kg. About 75% to 80% of the scandium reserves in the earth's crust are associated with bauxite. When producing alumina, more than 98% of the scandium in bauxite is enriched in red mud. The scandium in red mud is much greater than the general ore standard (20g / t). Therefore, it is of great significance to extract metallic scandium from red mud. Scandium and its compounds have excellent physical and chemical properties and are currently widely used in defense and military, energy materials, chemical industry, aerospace and other fields.

[0004] In recent years, the research on recovering titanium from red mud has been very active and has become one of the hot spots in the comprehensive utilization of red mud. Titanium is a silvery-white transition metal with the highest strength-to-weight ratio, excellent corrosion resistance and high and low temperature resistance. Titanium and titanium alloys are commonly used materials in the aerospace industry and are known as "space metals". In addition, titanium is also widely used in the manufacture of various excellent alloy materials, coatings, plastics, chemical fibers and other industrial products. Due to the excellent physical and chemical properties of titanium, it is regarded as a strategic metal by many developed countries such as the United States and France.

[0005] Hydrometallurgical technology is characterized by simple operation, low energy consumption, low carbon and green, but its disadvantage is that it cannot achieve the selective leaching of scandium in the leaching stage, and there is a large amount of co-leaching of metal impurities. Due to the similar ion radius, it will have an adverse effect on the purification of scandium. That is, the existing hydrometallurgy has low selectivity for scandium and titanium, and the purification effect is not ideal.

[0006] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0007] The object of the present invention is to provide a method for recovering scandium and titanium from Bayer red mud, so as to overcome the problems that a large amount of silica gel is produced in wet acid leaching, which reduces the metal leaching rate and has low selectivity for scandium and titanium.

[0008] To achieve the above object, the present invention provides a method for recovering scandium and titanium from Bayer process red mud, comprising the following steps:

[0009] (1) drying the red mud;

[0010] (2) The dried red mud is mixed with phosphoric acid for acid leaching reaction, and then filtered and dried to obtain pretreated red mud. Acid leaching with low-concentration phosphoric acid removes a large amount of sodium and silicon elements in the red mud, and enriches scandium and titanium elements.

[0011] (3) The pretreated red mud is acid-leached using a phosphoric acid-hydrogen peroxide system, and after solid-liquid separation, a red mud leachate containing scandium and titanium and an iron-rich leach residue are obtained.

[0012] (4) The red mud leachate containing scandium and titanium is mixed with a P204 extractant, and after stirring, shaking and oil-water separation, a scandium-loaded organic phase and a titanium-containing leachate are obtained. The organic phase is acid-washed multiple times to remove most of the metal impurities in the loaded organic phase.

[0013] (5) Ammonia water is added to the titanium leaching solution to adjust the pH value, and after heating and stirring, the solution is allowed to stand for precipitation, and then the solid and liquid are separated and then acid-washed to obtain pure amorphous titanium phosphate.

[0014] Preferably, in the above technical solution, in step (1), the red mud raw material is ground and dried at 100-150° C. for 1-24 h, and then sieved after cooling to obtain red mud powder.

[0015] Preferably, in the above technical solution, the concentration of phosphoric acid in step (2) is 0.5-1.5 mol / L, and the liquid-solid ratio of the mixture of red mud and phosphoric acid is 5-15:1 mL / g.

[0016] Preferably, in the above technical solution, the acid leaching reaction in step (2) is carried out at 25-30° C. for 10-60 min.

[0017] Preferably, in the above technical solution, the concentration of phosphoric acid in step (3) is 2-7 mol / L, and the concentration of hydrogen peroxide is 0.5-3 mol / L.

[0018] Preferably, in the above technical solution, the conditions for the acid leaching reaction in step (3) are as follows: the reaction temperature is 40-60° C., the liquid-to-solid ratio of red mud to the phosphoric acid-hydrogen peroxide mixed liquid is 8-14:1 mL / g, and the reaction time is 10-60 min.

[0019] Preferably, in the above technical solution, the diluent in step (4) is diluent oil, the concentration of P204 extractant is 2-9%, and the pH value of the leaching solution is 0.9-1.4.

[0020] Preferably, in the above technical solution, the extraction in step (4) is carried out at room temperature, the extraction time is 10-120 min, and the A / O is 1-5:1.

[0021] Preferably, in the above technical scheme, the eluents used for pickling in step (4) are phosphoric acid and hydrochloric acid, the concentration of phosphoric acid is 1-5 mol / L, the concentration of hydrochloric acid is 1-5 mol / L, the elution is carried out at room temperature, the A / O is 1-3:1, the time is 5-20 min, the phosphoric acid is eluted at least once, and then the hydrochloric acid is eluted at least once; the elution is carried out 2-6 times.

[0022] Preferably, in the above technical solution, the pH value of the leaching solution after extraction in step (5) is adjusted to 1-1.5, the precipitation reaction temperature is 90-110° C., the reaction time is 1-5 h, and after filtration, it is rinsed with phosphoric acid with a concentration of 0.5-1.5 mol / L.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The method of the present invention for recovering scandium and titanium from Bayer red mud adopts a combined two-stage acid leaching-extraction-precipitation method to separate and recover scandium and titanium from red mud. The purpose of the first stage low-concentration phosphoric acid leaching is to achieve dealkalization and desiliconization of red mud, and to obtain pretreated red mud enriched with scandium and titanium. Low-concentration phosphoric acid leaching is conducive to the leaching of silicon elements and prevents gel formation. The purpose of the second stage phosphoric acid-hydrogen peroxide system leaching is to prevent the formation of amorphous titanium phosphate that can adsorb scandium by introducing hydrogen peroxide, so that the scandium in the red mud can be migrated into the solution as much as possible, and the leaching rate of scandium and titanium is effectively improved. On the basis of the first stage acid leaching, the new reagent hydrogen peroxide is introduced to adjust the leaching system, which not only improves the scandium leaching rate, but also minimizes the influence of other metal impurities on the purification of scandium, which is more selective than the previous hydrometallurgical extraction of scandium and titanium.

[0025] (2) In the method of the present invention, during the extraction of scandium, the leaching solution is extracted with phosphoric acid and hydrogen peroxide by P204, wherein the phosphoric acid molecules will form a bond with the P204 molecules, thereby improving the extraction capacity. 2+ This substance is not easy to extract into the organic phase, thereby achieving the separation of scandium and titanium. After the extraction is completed, the remaining leachate is heated and precipitated to complete the recovery of titanium.

[0026] (3) The iron content of the iron-rich leaching residue produced after two-stage acid leaching is more than 50%, which is an excellent iron-containing waste residue. The iron element can be recovered by reduction roasting and magnetic separation. The red mud residue after iron extraction has a weak alkalinity close to neutral and can be used for building materials. The residual liquid can be added with sulfuric acid to achieve the recovery and reuse of phosphoric acid based on the principle of strong acid to weak acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A process flow chart of the method for recovering scandium and titanium from Bayer process red mud according to the present invention. DETAILED DESCRIPTION

[0028] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0029] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0030] Example 1

[0031] A method for recovering scandium and titanium from Bayer red mud, the process flow chart of which is as follows Figure 1 As shown, it includes four parts: pretreatment acid leaching of red mud, acid leaching of phosphoric acid-hydrogen peroxide system, extraction of scandium with P204, and precipitation separation of titanium phosphate, and specifically includes the following steps:

[0032] (1) Preparation of red mud raw materials: The red mud raw materials were obtained from Guangxi Pingguo Aluminum Company. The blocky red mud was ground with a grinding dish and dried in a muffle furnace at 120°C for 12 hours. After the red mud was cooled to room temperature, it was sieved with a 120-mesh sieve to obtain a dry red mud raw material test sample;

[0033] (2) Pretreatment acid leaching: Take 10 g of red mud raw material and add 1.0 mol / L phosphoric acid solution at a liquid-to-solid ratio of 10:1 mL / g. Mix the red mud and dilute phosphoric acid evenly, react at room temperature for 20 min, and then filter. Collect the filter residue, dry it, and grind it to obtain a dealkalization and desiliconization pretreated red mud test sample.

[0034] Table 1 Chemical composition analysis results of red mud raw material and acid leaching pretreated red mud (wt%)

[0035]

[0036] (3) Acid leaching in phosphoric acid-hydrogen peroxide system: Take 1 g of pretreated red mud, add 14 mL of a phosphoric acid-hydrogen peroxide mixed solution with a phosphoric acid concentration of 7.0 mol / L and a hydrogen peroxide concentration of 3.0 mol / L and place it in a conical flask, mix the pretreated red mud particles and the leachate evenly, put it in a constant temperature water bath oscillator set at 60 °C to react for 30 min and then filter it, wash the iron-rich leaching residue with ultrapure water to neutrality, and obtain a red mud leachate containing scandium and titanium.

[0037] (4) Extraction of scandium: Take 100 mL of red mud leachate containing scandium and titanium, and extract scandium using the extractant P204. At room temperature, add ammonia water to adjust the pH of the red mud leachate to 1.3, the volume concentration of P204 is 7%, the extraction time is 50 min, the A / O is 3:1, and the mixture is stirred and allowed to stand for oil-water separation to obtain a scandium-rich organic phase and a titanium-containing extract residue. Use phosphoric acid and hydrochloric acid as eluents, and elute 4 times to remove most of the metal impurities in the loaded organic phase. The elution conditions are: phosphoric acid and hydrochloric acid concentrations of 4 mol / L, A / O of 1:1, time of 10 min, and room temperature. Elute 4 times in total, first elute twice with phosphoric acid, and then elute twice with hydrochloric acid.

[0038] (5) Precipitation and separation of titanium: Take 500 mL of the titanium-containing extract residue and heat it to 100°C for 3 hours to completely decompose the hydrogen peroxide in the solution medium, and the titanium water complex combines with the phosphate group in the solution to form an amorphous titanium phosphate precipitate. After filtering, rinse with 1.0 mol / L phosphoric acid to remove the remaining co-precipitated metal impurities.

[0039] In this case, the leaching rates of scandium, titanium, iron and aluminum were 83.85%, 34%, 16.29% and 54.54% respectively. The extraction rate of scandium was 98.94% during the extraction process, and the separation coefficients of scandium, iron, aluminum and titanium were 33.45, 500.78 and 992.84 respectively; the precipitation rate of titanium was 95.32%.

[0040] Example 2

[0041] A method for recovering scandium and titanium from Bayer process red mud comprises the following steps:

[0042] (1) Acid leaching in phosphoric acid-hydrogen peroxide system: Using the pretreated red mud treated in step (1) and step (2) of Example 1, 1 g of the pretreated red mud was taken, and 10 mL of a phosphoric acid-hydrogen peroxide mixed solution with a phosphoric acid concentration of 5.0 mol / L and a hydrogen peroxide concentration of 2.0 mol / L was added and placed in a conical flask, the pretreated red mud particles and the leachate were mixed evenly, placed in a constant temperature water bath oscillator set at a temperature of 50° C., reacted for 30 min, and then filtered, and the iron-rich leaching residue was washed with ultrapure water until neutral, to obtain a red mud leachate containing scandium and titanium.

[0043] (2) Extraction of scandium: Take 100 mL of red mud leachate containing scandium and titanium, and extract scandium using the extractant P204. Adjust the pH of the red mud leachate to 1.1 at room temperature, the volume concentration of P204 is 3%, the extraction time is 50 min, the A / O is 3:1, and stir and stand for oil-water separation to obtain a scandium-rich organic phase and a titanium-containing extract residue. Use phosphoric acid and hydrochloric acid as eluents, and elute 4 times to remove most of the metal impurities in the loaded organic phase. The elution conditions are: phosphoric acid and hydrochloric acid concentration 4 mol / L, A / O 1:1, time 10 min, room temperature. Elute 4 times in total, first elute twice with phosphoric acid, and then elute twice with hydrochloric acid.

[0044] (3) Precipitation and separation of titanium: Take 500 mL of the titanium-containing extraction residue, adjust the pH to 1.3 with ammonia water, and heat to 100°C for 3 h to completely decompose the hydrogen peroxide in the solution medium. The titanium water complex combines with the phosphate groups in the solution to form an amorphous titanium phosphate precipitate. After filtering, rinse with 1.0 mol / L phosphoric acid to remove the remaining co-precipitated metal impurities.

[0045] During the leaching process in this case, the leaching rates of scandium, titanium, iron and aluminum were 78.64%, 60.97%, 7.53% and 40.24% respectively; during the extraction process, the extraction rate of scandium was 94.86%, and the separation coefficients of scandium with iron, aluminum and titanium were 78.23, 837.97 and 1864.73 respectively; the precipitation rate of titanium was 96.75%.

[0046] Example 3

[0047] A method for recovering scandium and titanium from Bayer process red mud comprises the following steps:

[0048] (1) Acid leaching in phosphoric acid-hydrogen peroxide system: Using the pretreated red mud treated in step (1) and step (2) of Example 1, 1 g of the pretreated red mud was taken, and 8 mL of a phosphoric acid-hydrogen peroxide mixed solution with a phosphoric acid concentration of 3.0 mol / L and a hydrogen peroxide concentration of 1.0 mol / L was added and placed in a conical flask, the pretreated red mud particles and the leachate were mixed evenly, placed in a constant temperature water bath oscillator set at a temperature of 40° C., reacted for 30 min, and then filtered, and the iron-rich leaching residue was washed with ultrapure water until neutral, to obtain a red mud leachate containing scandium and titanium.

[0049] (2) Extraction of scandium: Take 100 mL of red mud leachate containing scandium and titanium, and extract scandium using the extractant P204. At room temperature, add ammonia water to adjust the pH of the red mud leachate to 0.9, the volume concentration of P204 is 2%, the extraction time is 50 min, the A / O is 3:1, and the mixture is stirred and allowed to stand for oil-water separation to obtain a scandium-rich organic phase and a titanium-containing extract residue. Use phosphoric acid and hydrochloric acid as eluents, and elute 4 times to remove most of the metal impurities in the loaded organic phase. The elution conditions are: phosphoric acid and hydrochloric acid concentrations of 4 mol / L, A / O of 1:1, time of 10 min, and room temperature. Elute 4 times in total, eluting twice with phosphoric acid and then eluting twice with hydrochloric acid.

[0050] (3) Precipitation and separation of titanium: Take 500 mL of the titanium-containing extraction residue and heat it to 100°C for 3 h to completely decompose the hydrogen peroxide in the solution medium. The titanium water complex combines with the phosphate groups in the solution to form an amorphous titanium phosphate precipitate. After filtering, rinse with 1.0 mol / L phosphoric acid to remove the remaining co-precipitated metal impurities.

[0051] During the leaching process in this case, the leaching rates of scandium, titanium, iron and aluminum were 59.36%, 42.07%, 3.19% and 35.87% respectively; during the extraction process, the extraction rate of scandium was 83.58%, and the separation coefficients of scandium with iron, aluminum and titanium were 28.28, 698.26 and 792.65 respectively; the precipitation rate of titanium was 98.37%.

[0052] Example 4

[0053] A method for recovering scandium and titanium from Bayer process red mud comprises the following steps:

[0054] (1) Acid leaching in phosphoric acid-hydrogen peroxide system: Using the pretreated red mud treated in step (1) and step (2) of Example 1, 1 g of the pretreated red mud was taken, and 12 mL of a phosphoric acid-hydrogen peroxide mixed solution with a phosphoric acid concentration of 5.0 mol / L and a hydrogen peroxide concentration of 0.5 mol / L was added and placed in a conical flask. The pretreated red mud particles and the leachate were mixed evenly, placed in a constant temperature water bath oscillator set at a temperature of 40° C. and reacted for 30 min, and then filtered. The iron-rich leaching residue was washed with ultrapure water until neutral, to obtain a red mud leachate containing scandium and titanium.

[0055] (2) Extraction of scandium: Take 100 mL of red mud leachate containing scandium and titanium, and extract scandium using the extractant P204. At room temperature, add ammonia water to adjust the pH of the red mud leachate to 1.4, the volume concentration of P204 is 5%, the extraction time is 50 minutes, the A / O is 3:1, and the mixture is stirred and allowed to stand for oil-water separation to obtain a scandium-rich organic phase and a titanium-containing extract residue. Use phosphoric acid and hydrochloric acid as eluents, and elute 4 times to remove most of the metal impurities in the loaded organic phase. The elution conditions are: phosphoric acid and hydrochloric acid concentrations of 4 mol / L, A / O of 1:1, time of 10 minutes, and room temperature. Elute 4 times in total, first elute twice with phosphoric acid, and then elute twice with hydrochloric acid.

[0056] (3) Precipitation and separation of titanium: Take 500 mL of the titanium-containing extraction residue and heat it to 100°C for 3 h to completely decompose the hydrogen peroxide in the solution medium. The titanium water complex combines with the phosphate groups in the solution to form an amorphous titanium phosphate precipitate. After filtering, rinse with 1.0 mol / L phosphoric acid to remove the remaining co-precipitated metal impurities.

[0057] During the leaching process in this case, the leaching rates of scandium, titanium, iron and aluminum were 70.59%, 46.18%, 6.86% and 39.35% respectively; during the extraction process, the extraction rate of scandium was 91.69%, and the separation coefficients of scandium with iron, aluminum and titanium were 21.43, 407.28 and 386.36 respectively; the precipitation rate of titanium was 99.37%.

[0058] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for recovering scandium and titanium from Bayer process red mud, characterized in that: The following steps are involved: (1) drying the red mud; (2) mixing the dried red mud and phosphoric acid for acid leaching reaction, and then filtering and drying to obtain pretreated red mud; (3) acid leaching the pretreated red mud using a phosphoric acid-hydrogen peroxide system, and obtaining a red mud leachate containing scandium and titanium and an iron-rich leach residue after solid-liquid separation; (4) mixing the red mud leachate containing scandium and titanium with a P204 extractant, stirring, shaking and separating the oil and water to obtain a scandium-loaded organic phase and a titanium-containing leachate, and washing the organic phase with acid for multiple times; (5) Ammonia water is added to the titanium leaching solution to adjust the pH value, and after heating and stirring, the solution is allowed to stand and precipitate to obtain amorphous titanium phosphate, which is then acid washed after solid-liquid separation.

2. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: Step (1) grinding the red mud raw material, drying it at 100-150° C. for 1-24 h, and sieving it after cooling to obtain red mud powder.

3. The method for recovering scandium and titanium from Bayer red mud according to claim 1, characterized in that: In step (2), the concentration of phosphoric acid is 0.5-1.5 mol / L, and the liquid-solid ratio of the mixture of red mud and phosphoric acid is 5-15:1 mL / g.

4. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: The acid leaching reaction in step (2) is carried out at 25-30° C. for 10-60 min.

5. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: In step (3), the concentration of phosphoric acid is 2-7 mol / L, and the concentration of hydrogen peroxide is 0.5-3 mol / L.

6. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: The conditions of the acid leaching reaction in step (3) are as follows: a reaction temperature of 40-60° C., a liquid-to-solid ratio of red mud to phosphoric acid-hydrogen peroxide mixed liquid of 8-14:1 mL / g, and a reaction time of 10-60 min.

7. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: The diluent in step (4) is diluent oil, the concentration of P204 extractant is 2-9%, and the pH value of the leaching solution is 0.9-1.

4.

8. The method for recovering scandium and titanium from Bayer red mud according to claim 1, characterized in that: The extraction in step (4) is carried out at room temperature, the extraction time is 10-120 min, and the A / O is 1-5:

1.

9. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: In step (4), the eluents used for pickling are phosphoric acid and hydrochloric acid, the concentration of phosphoric acid is 1-5 mol / L, the concentration of hydrochloric acid is 1-5 mol / L, the elution is carried out at room temperature, the A / O ratio is 1-3:1, the time is 5-20 min, the phosphoric acid is used for elution at least once, and then the hydrochloric acid is used for elution at least once; the elution is carried out 2-6 times.

10. The method for recovering scandium and titanium from Bayer process red mud according to claim 1, characterized in that: Step (5) The pH value of the leaching solution after extraction is adjusted to 1-1.5, the precipitation reaction temperature is 90-110° C., the reaction time is 1-5 h, and after filtering, it is rinsed with phosphoric acid with a concentration of 0.5-1.5 mol / L.

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