Method for preparing industrial-grade aluminum oxide from red mud

Abstract

The invention discloses a method for preparing industrial-grade aluminum oxide by using red mud, which comprises the following steps: S1, carrying out ore grinding treatment on the red mud to obtain red mud powder with D90 less than 74 mu m; s2, the red mud powder obtained in the step S1 is added into mixed acid, acid leaching treatment is carried out at the temperature of 30-50 DEG C, ultrasonic treatment is assisted in the acid leaching process, a leaching mixed solution is obtained, solid-liquid separation is carried out on the leaching mixed solution, and leaching residues and a leaching solution containing iron ions and aluminum ions are obtained; the mixed acid is a mixed solution of hydrochloric acid, oxalic acid and phosphoric acid; s3, adjusting the pH value of the leachate obtained in the step S2, carrying out auxiliary stirring reaction under a set temperature condition, aging, and filtering out ferric hydroxide precipitate to obtain filtrate; s4, adjusting the pH value of the filtrate obtained in the step S3, carrying out auxiliary stirring reaction under a set temperature condition, and then aging and filtering to obtain an aluminum hydroxide precipitate; and S5, calcining the aluminum hydroxide precipitate obtained in the step S4, and cooling to obtain the industrial-grade aluminum oxide. According to the method, the aluminum element in the red mud is extracted through an acid dissolution and fractional precipitation technology, and production of industrial-grade aluminum oxide is achieved; the method is simple in step and environment-friendly and efficient in technological process, and a new thought is provided for red mud recycling.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy and resource recovery, and in particular to a method for preparing industrial-grade alumina by utilizing red mud. Background Art

[0002] Red mud is a solid waste produced by the alumina industry in the process of extracting alumina from bauxite. Its main components are iron oxide, aluminum oxide, silicon dioxide, and a small amount of oxides such as titanium and calcium. Due to the huge output, complex composition, strong alkalinity and difficulty in natural degradation of red mud, its storage not only occupies a large amount of land, but also may cause environmental pollution problems. Therefore, how to effectively utilize red mud resources and prepare materials with economic value has become one of the important topics of concern to the global aluminum industry.

[0003] At present, the research on the comprehensive utilization of red mud mainly focuses on its use as low value-added products such as building materials, landfill soil, and soil conditioner. However, with the advancement of technology, researchers have gradually explored the separation and extraction of high value-added components in red mud, such as the resource utilization of iron and aluminum. In particular, the content of alumina in red mud is high and has potential utilization value. Therefore, the development of a method for extracting industrial-grade alumina from red mud has important economic and environmental significance.

[0004] The method of extracting alumina from red mud usually adopts the acid dissolution method, in which the liquid after acid dissolution contains metal ions such as iron and aluminum. By adjusting the pH of the solution, selective precipitation and separation of iron and aluminum can be achieved. However, the pH control of the solution during acid dissolution, the optimization of precipitation and separation conditions, and the calcination and conversion process to alumina all require scientific design to ensure that high-purity alumina products that can be used in industry are obtained. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for preparing industrial-grade alumina using red mud, so as to improve the recovery rate of aluminum in red mud and reduce the pollution of red mud to the environment. The method extracts aluminum from red mud through acid dissolution and step-by-step precipitation technology to achieve the production of industrial-grade alumina. The method has simple steps, and the process is environmentally friendly and efficient, providing a new idea for the resource utilization of red mud.

[0006] In order to achieve the above object, the present invention provides a method for preparing industrial-grade alumina using red mud, comprising the following steps:

[0007] S1, grinding the red mud to obtain D 90 Red mud powder <74μm;

[0008] S2, adding the red mud powder obtained in step S1 to a mixed acid, performing acid leaching at 30-50° C., performing ultrasonic treatment to assist the acid leaching process, obtaining a leached mixed solution, and performing solid-liquid separation on the leached mixed solution to obtain leached residue and a leached solution containing iron and aluminum ions;

[0009] The mixed acid is a mixed solution of hydrochloric acid, oxalic acid and phosphoric acid, the molar ratio of hydrochloric acid to oxalic acid is (2-5):(2-5), the ratio of the amount of phosphoric acid to the amount of iron in red mud is 0.9-1.2:1; H + The molar concentration is 4 to 10 mol / L;

[0010] S3, adjusting the pH of the leachate obtained in step S2, assisting the stirring reaction under the set temperature condition, and then aging and filtering out the iron hydroxide precipitate to obtain a filtrate;

[0011] S4, adjusting the pH of the filtrate obtained in step S3, assisting the stirring reaction under the set temperature condition, and then aging and filtering to obtain aluminum hydroxide precipitate;

[0012] S5. The aluminum hydroxide precipitate obtained in step S4 is calcined and cooled to obtain industrial-grade alumina.

[0013] Furthermore, in step S2, the acid leaching treatment time is 0.5 to 5 hours, and the power of the ultrasonic treatment is 200 to 1000W.

[0014] Furthermore, in step S2, the liquid-to-solid ratio of the mixed acid solution to the red mud powder is 4 to 8:1.

[0015] Furthermore, in step S3, the pH of the leaching solution is adjusted to 2.5-4.5, and the reaction is stirred at room temperature-90° C. for 5-15 minutes to fully precipitate the iron hydroxide.

[0016] Furthermore, in step S4, the pH of the filtrate is adjusted to 4.5-5.0 by gradually adding sodium hydroxide or ammonia solution, and the reaction temperature is room temperature to 90°C to control the particle size and purity of the aluminum hydroxide precipitate. After aging for 15-60 minutes, the aluminum hydroxide precipitate is obtained by suction filtration.

[0017] Furthermore, in step S5, the temperature for calcining aluminum hydroxide is 1000-1200° C., and the calcination time is 1-2 hours.

[0018] In view of the technical difficulties in the resource utilization of red mud, the present invention develops a process for preparing industrial-grade alumina from red mud through ternary mixed acid dissolution, precipitation separation, and calcination treatment steps, thereby achieving efficient extraction and utilization of aluminum resources in red mud and providing a new technical approach for the green treatment and recycling of red mud.

[0019] During the acid leaching process of red mud, the synergistic effect between the ternary mixed acids (hydrochloric acid, oxalic acid and phosphoric acid) significantly improves the leaching efficiency of metals. Hydrochloric acid provides a strong acidic environment to quickly dissolve the metal oxides in the red mud; oxalic acid forms soluble complexes with metal ions through complexation reactions to increase their solubility; phosphoric acid helps to form iron phosphate precipitation and promotes the recovery of iron phosphate. Acid leaching treatment under low temperature conditions (30-50°C) effectively controls the reaction rate, avoids side reactions at high temperatures, and ensures the efficient recovery of major metals. Ultrasonic-assisted acid leaching further improves the dissolution rate and reaction efficiency. The cavitation effect of ultrasound enhances the contact between the acid solution and the solid surface, accelerates the dissolution of metal oxides, and reduces the reaction time. The synergistic effect of the three not only improves the recovery rate of iron and aluminum, but also optimizes the processing conditions, reduces energy consumption, and improves the economy and efficiency of the overall process.

[0020] Beneficial effects of the present invention:

[0021] 1) Improve the recovery rate of aluminum: The present invention effectively extracts aluminum from red mud by acid dissolution and step-by-step precipitation, thereby improving the recovery rate of aluminum. Compared with traditional methods, it reduces the waste of aluminum resources and achieves efficient utilization of resources.

[0022] 2) Simplified process flow: The process steps of the present invention are simple and easy to operate. Through reasonable pH adjustment and temperature control, iron hydroxide and aluminum hydroxide are precipitated in sequence, avoiding multiple separation processes and reducing production complexity.

[0023] 3) Cost saving: The present invention uses common acids such as hydrochloric acid, sulfuric acid or nitric acid as the dissolution medium, and adjusts the liquid-solid ratio and acid concentration to achieve the best effect, thereby reducing the amount of acid used, the consumption of chemical reagents and the process cost.

[0024] 4) Reduce environmental pollution: By utilizing red mud as a resource, the present invention effectively reduces the harm of red mud to the environment. The iron, aluminum and other components in the red mud are extracted and recycled, reducing the potential pollution risk of solid waste storage to the land and water, which meets the requirements of green and sustainable development.

[0025] 5) Obtain high-quality industrial-grade alumina: The process of the present invention optimizes the precipitation conditions of aluminum hydroxide by precisely controlling pH, temperature and aging time, so that the final calcined alumina has high purity and is suitable for industrial production, thereby increasing the added value of red mud utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings and appendices required for use in the embodiments or the description of the prior art. 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.

[0027] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0028] The following are specific implementation cases given by the inventor. It should be noted that these embodiments are only for better interpretation of the present invention and are not intended to limit the scope of implementation of the present invention. All parameter selections within the scope of the technical solution of the present invention belong to the scope of protection of the present invention.

[0029] The following is further described through specific embodiments and drawings.

[0030] Example 1

[0031] A method for preparing industrial-grade alumina using red mud, comprising:

[0032] Grind the red mud to D 90 <74μm red mud powder, then add the red mud powder into a mixed acid solution of hydrochloric acid, oxalic acid and phosphoric acid, the molar ratio of hydrochloric acid to oxalic acid is 5:2, and the mixed acid solution has H + The molar concentration is 7 mol / L, the liquid-solid ratio of the mixed acid solution to the red mud powder is 7:1, the acid leaching treatment is carried out at 40°C, the acid leaching process is assisted by ultrasonic 500W treatment, and a leached mixed solution is obtained after acid leaching for 2 hours. The leached mixed solution is subjected to solid-liquid separation to obtain leached residue and a leached solution containing iron and aluminum ions;

[0033] Ammonia water was added to the leachate to adjust the pH value of the leachate to 3.5, and the reaction was stirred at 60°C, and then aged and filtered to obtain iron hydroxide and a filtrate; the pH value of the filtrate was adjusted to 4.5, and the reaction was stirred at 60°C, and then aged to allow aluminum hydroxide to be fully precipitated, and the aluminum hydroxide precipitate was obtained by suction filtration, and the aluminum hydroxide precipitate was calcined at 1100°C for 1.5 hours, and aluminum oxide was obtained after cooling.

[0034] In Example 1, the aluminum leaching rate is 95.63%, and the aluminum oxide purity is 99.5%, reaching the industrial grade aluminum oxide standard.

[0035] Example 2

[0036] A method for preparing industrial-grade alumina using red mud comprises the following steps:

[0037] Grind the red mud to D 90<74μm red mud powder, then add the red mud powder to grind the red mud to D 90 The red mud powder is less than 74 μm, and then the red mud powder is added to a mixed acid solution of hydrochloric acid, oxalic acid and phosphoric acid, with a molar ratio of hydrochloric acid to oxalic acid of 2:5. + The molar concentration is 7 mol / L, the liquid-solid ratio of the mixed acid solution to the red mud powder is 6:1, the ratio of the amount of phosphoric acid to the amount of iron in the red mud is 1:1, acid leaching is carried out at 40°C, the acid leaching process is assisted by ultrasonic 200W treatment, and a leached mixed solution is obtained after acid leaching for 2 hours, and the leached mixed solution is subjected to solid-liquid separation to obtain leached residue and a leached solution containing iron and aluminum ions;

[0038] Ammonia water was added to the leachate to adjust the pH value of the leachate to 2.0, and the reaction was stirred at 60°C, and then aged and filtered to obtain iron hydroxide and a filtrate; the pH value of the filtrate was adjusted to 5, and the reaction was stirred at 60°C, and then aged to fully precipitate aluminum hydroxide, and filtered to obtain aluminum hydroxide precipitate, and the aluminum hydroxide precipitate was calcined at 1100°C for 1.5 hours, and cooled to obtain aluminum oxide.

[0039] In Example 2, the aluminum leaching rate is 85.23%, and the aluminum oxide purity is 98.3%, reaching the industrial grade aluminum oxide standard.

[0040] Comparative Example 1

[0041] In order to further demonstrate the advantages of the process method of the present invention, especially the effect of improving the aluminum leaching rate and the purity of the final product, Comparative Example 1 did not use all the optimized conditions in the present invention, but adjusted some parameters.

[0042] (1) pre-treating red mud into red mud powder with D90 < 74 μm, adding the red mud powder into a hydrochloric acid solution with a hydrochloric acid concentration of 5 M and a liquid-to-solid ratio of 5:1, dissolving the red mud powder at 70° C., stirring for 2 hours to obtain a leaching mixture, and performing solid-liquid separation on the leaching mixture to obtain leaching residue and a leaching solution containing iron and aluminum ions;

[0043] (2) adding ammonia water to the leachate to adjust the pH value of the leachate to 3.5, stirring the reaction at 60°C, aging and filtering to obtain iron hydroxide and a filtrate; adjusting the pH value of the filtrate to 4.5, stirring the reaction at 60°C, aging to allow aluminum hydroxide to fully precipitate, filtering to obtain aluminum hydroxide precipitate, calcining the aluminum hydroxide precipitate at 1100°C for 1.5 hours, and cooling to obtain aluminum oxide.

[0044] Table 1 Leaching rate and product purity of the embodiments and comparative examples

[0045] project Example 1 Example 2 Comparative Example 1 Aluminum leaching rate 95.63％ 85.23％ 70.12％ Alumina purity 99.5％ 98.3％ 93.4％

[0046] The aluminum leaching rate and product purity of Comparative Example 1 are significantly lower than those of Examples 1 and 2 of the present invention, and the specific analysis is as follows:

[0047] In Comparative Example 1, since hydrochloric acid is used as the leaching solution, the aluminum leaching efficiency and the aluminum oxide purity are relatively low, which are 70.12% and 93.4% respectively. In Examples 1 and 2, by optimizing the mixed acid composition and acid leaching conditions, the aluminum resource utilization efficiency is significantly improved.

[0048] In summary, the present invention significantly improves the aluminum leaching rate and the purity of the product alumina by optimizing the red mud leaching process, which is better than the effect of the comparative example, verifying the advantages of the process method in resource recovery and product purity.

[0049] The preferred embodiments of the present invention are described in detail above, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing industrial-grade alumina using red mud, characterized in that: The following steps are involved: S1, grinding the red mud to obtain D 90 Red mud powder <74μm; S2, adding the red mud powder obtained in step S1 to a mixed acid, performing acid leaching at 30-50° C., performing ultrasonic treatment to assist the acid leaching process, obtaining a leached mixed solution, and performing solid-liquid separation on the leached mixed solution to obtain leached residue and a leached solution containing iron and aluminum ions; The mixed acid is a mixed solution of hydrochloric acid, oxalic acid and phosphoric acid, the molar ratio of hydrochloric acid to oxalic acid is (2-5):(2-5), the ratio of the amount of phosphoric acid to the amount of iron in red mud is 0.9-1.2:1; H + The molar concentration is 4 to 10 mol / L; S3, adjusting the pH of the leachate obtained in step S2, assisting the stirring reaction under the set temperature condition, and then aging and filtering out the iron hydroxide precipitate to obtain a filtrate; S4, adjusting the pH of the filtrate obtained in step S3, assisting the stirring reaction under the set temperature condition, and then aging and filtering to obtain aluminum hydroxide precipitate; S5. The aluminum hydroxide precipitate obtained in step S4 is calcined and cooled to obtain industrial-grade alumina.

2. A method for preparing industrial-grade alumina using red mud according to claim 1, characterized in that: In step S2, the acid leaching treatment time is 0.5 to 5 hours, and the power of the ultrasonic treatment is 200 to 1000W.

3. A method for preparing industrial-grade alumina using red mud according to claim 1 or 2, characterized in that: In step S2, the liquid-to-solid ratio of the mixed acid solution to the red mud powder is 4 to 8:

1.

4. The method for preparing industrial-grade alumina using red mud according to claim 1, characterized in that: In step S3, the pH of the leaching solution is adjusted to 2.5 to 4.5, and the mixture is stirred and reacted at room temperature to 90° C. for 5 to 15 minutes to fully precipitate the iron hydroxide.

5. The method for preparing industrial-grade alumina using red mud according to claim 1, characterized in that: In step S4, the pH of the filtrate is adjusted to 4.5-5.0 by gradually adding sodium hydroxide or ammonia solution, the reaction temperature is room temperature-90°C, and then aged for 15-60 minutes, and filtered to obtain aluminum hydroxide precipitate.

6. The method for preparing industrial-grade alumina using red mud according to claim 1, characterized in that: In step S5, the temperature for calcining aluminum hydroxide is 1000-1200° C., and the calcination time is 1-2 hours.

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