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CN-121992187-A - Method for synchronously extracting and separating iron and aluminum in red mud based on mixed acid leaching

CN121992187ACN 121992187 ACN121992187 ACN 121992187ACN-121992187-A

Abstract

The invention belongs to the technical field of solid waste recycling and hydrometallurgy, discloses a method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching, and effectively solves the problems of long flow, high acid-base consumption or incomplete iron-aluminum separation in the existing process for recovering iron and aluminum from red mud. According to the invention, iron and aluminum in red mud are leached in one step through a mixed acid system of hydrochloric acid and sulfuric acid, then coprecipitation is realized by controlling precipitation pH, and finally aluminum is selectively dissolved by an alkali dissolution method, so that the iron and aluminum are separated and recovered with high efficiency and high purity. The invention has the advantages of simplified process, improved efficiency, good separation effect, high product purity, treatment of waste by waste, low cost, high comprehensive utilization degree of resources and good operation safety.

Inventors

  • ZHANG YAZHOU
  • XIAO FULAI
  • CUI MINGMING
  • ZOU YULAN

Assignees

  • 山东新寰清科技发展有限公司

Dates

Publication Date
20260508
Application Date
20260126

Claims (7)

  1. 1. The method for synchronously extracting and separating iron and aluminum in red mud based on mixed acid leaching is characterized by comprising the following steps of: S1, crushing and grinding red mud to D90<100 mu m to obtain red mud powder; s2, mixing the red mud powder with mixed acid according to the solid-liquid mass ratio of 1:3-5, stirring and reacting for 3-3.5 hours at 90+/-5 ℃, and carrying out solid-liquid separation after the reaction is finished to obtain acid leaching mother liquor and leaching residues; The mixed acid consists of hydrochloric acid and sulfuric acid according to the volume ratio of 1:1; S3, washing the leaching residues with water until the pH value is approximately 6, and obtaining acidic washing liquid and washed leaching residues; S4, diluting the acid leaching mother liquor, then dropwise adding a sodium carbonate solution into the diluted acid leaching mother liquor under the water bath condition of 60 ℃, adjusting the pH value of the acid leaching mother liquor to 6.5-7.0, standing for aging after stirring reaction, and filtering to obtain iron-aluminum mixed hydroxide filter residues and filtrate; S5, treating the iron-aluminum mixed hydroxide filter residues with excessive sodium hydroxide solution, filtering and separating to obtain ferric hydroxide solid and sodium metaaluminate solution, then adjusting the pH value of the sodium metaaluminate solution to 7-8, and precipitating to obtain aluminum hydroxide.
  2. 2. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 1, wherein in the step S2, the total acid concentration of the mixed acid is 8-9mol/L.
  3. 3. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 1, wherein in the step S4, the acid leaching mother liquor is diluted by adopting the acidic washing liquor obtained in the step S3 or the filtrate obtained in the step S4 according to a mass ratio of 2:1.
  4. 4. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 1, wherein in the step S4, the concentration of sodium carbonate solution is 2-3mol/L.
  5. 5. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 1, wherein in the step S5, the concentration of sodium hydroxide solution is 6mol/L, and the addition amount of the sodium hydroxide solution is 100% -120% of the theoretical amount required for completely dissolving aluminum in the filter residue of the iron-aluminum mixed hydroxide.
  6. 6. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 5, wherein in the step S5, the reagent used for adjusting the pH of the sodium metaaluminate solution to 7-8 is dilute hydrochloric acid or carbon dioxide gas.
  7. 7. The method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching according to claim 1, wherein in the step S3, the washed leaching residue is used as a soil conditioner or a raw material of a building material.

Description

Method for synchronously extracting and separating iron and aluminum in red mud based on mixed acid leaching Technical Field The invention belongs to the technical field of solid waste recycling and hydrometallurgy, and particularly relates to a method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching. Background The red mud is a large amount of alkaline solid waste produced by the alumina industry and is rich in iron, aluminum, silicon, sodium, titanium and other elements. At present, the red mud is piled up to occupy a large amount of land and also has environmental risks. Recovery of valuable metals, particularly iron and aluminum, from red mud is an important way to realize the resource utilization thereof. The prior art mostly adopts single acid step leaching or high temperature reduction and other processes, and has the problems of long flow, large acid-base consumption, high energy consumption, incomplete iron-aluminum separation and the like. For example, the step leaching has better selectivity, but the steps are complicated, and when single acid is adopted for simultaneous leaching, the efficient separation of iron and aluminum ions in the subsequent solution becomes a technical difficulty. Therefore, the development of a novel red mud treatment process which has simple flow and low cost and can realize the high-purity separation of iron and aluminum has important practical significance. Disclosure of Invention The invention aims to provide a method for synchronously extracting and separating iron and aluminum from red mud based on mixed acid leaching, which effectively solves the problems of long flow, high acid-base consumption or incomplete iron-aluminum separation in the existing process for recovering iron and aluminum from red mud. In order to solve the technical problems, the technical scheme adopted by the invention is that the method for synchronously extracting and separating iron and aluminum in the red mud based on mixed acid leaching comprises the following steps of S1, crushing and grinding the red mud to D90<100 mu m to obtain red mud powder. S2, mixing the red mud powder with mixed acid according to the solid-liquid mass ratio of 1:3-5, stirring and reacting for 3-3.5 hours at 90+/-5 ℃, and carrying out solid-liquid separation after the reaction is finished to obtain acid leaching mother liquor and leaching residues. The mixed acid consists of hydrochloric acid and sulfuric acid according to the volume ratio of 1:1. And S3, washing the leaching residues with water until the pH value is close to 6, and obtaining acidic washing liquid and washed leaching residues. S4, diluting the acid leaching mother liquor, then dropwise adding a sodium carbonate solution into the diluted acid leaching mother liquor under the water bath condition of 60 ℃, adjusting the pH of the acid leaching mother liquor to 6.5-7.0, standing for aging after stirring reaction, and filtering to obtain iron-aluminum mixed hydroxide filter residues and filtrate. S5, treating the iron-aluminum mixed hydroxide filter residues with excessive sodium hydroxide solution, filtering and separating to obtain ferric hydroxide solid and sodium metaaluminate solution, then adjusting the pH value of the sodium metaaluminate solution to 7-8, and precipitating to obtain aluminum hydroxide. Further, in step S2, the total acid concentration of the mixed acid is 8-9mol/L. In step S4, the acid leaching mother liquor is diluted by the acidic washing liquor obtained in step S3 or the circulating filtrate in the process system (i.e. the filtrate obtained in step S4) according to a mass ratio of 2:1. Further, in step S4, the concentration of the sodium carbonate solution is 2-3mol/L. Further, in the step S5, the concentration of the sodium hydroxide solution is 6mol/L, and the addition amount of the sodium hydroxide solution is 100% -120% of the theoretical amount required for completely dissolving aluminum in the iron-aluminum mixed hydroxide filter residues. In step S5, the reagent used for adjusting the pH of the sodium metaaluminate solution to 7-8 is dilute hydrochloric acid or carbon dioxide gas. Further, in step S3, the washed leaching residue is used as a soil conditioner or a raw material of a building material. Compared with the prior art, the method has the beneficial technical effects that (1) the process is simplified, the efficiency is improved, the method adopts the mixed acid one-step leaching process of hydrochloric acid and sulfuric acid, simultaneously efficiently dissolves iron and aluminum in the red mud, avoids the complicated step leaching process, shortens the treatment period, and improves the equipment utilization rate. (2) The method has the advantages of good separation effect and high product purity, realizes synchronous and complete precipitation of iron and aluminum ions by accurately controlling the pH value (6.5-7.0) of sodium carbonate precipitation, an