Method for separating and recovering iron from red mud

Abstract

The invention relates to a method for separating and recovering iron from red mud. The method is characterized by comprising the steps: of leaching out and removing iron from the red mud by using an oxalic acid solution, and filtering to obtain iron-free red mud and an iron oxalate-containing leaching solution, wherein the obtained iron-free red mud can be used as a raw material for producing cement and fireproof bricks; iron oxalate in the obtained leaching solution is reduced to ferrous oxalate through membrane electrolysis or adding a reducing agent and ferrous oxalate is precipitated out, or iron in the solution is separated by directly neutralizing and precipitating an iron hydroxide and oxalate mixture; obtained ferrous oxalate is decomposed to obtain oxalic acid and an iron-containing compound; the obtained iron hydroxide and oxalate mixture is selectively leached out, separated and recovered to obtain oxalic acid and an iron-containing compound; the process of returning recovered oxalic acid to the red mud to leach out and remove iron is cyclically used. The method has the characteristics of short technological process, good iron separation effect, simplicity and convenience in operation, environmental friendliness and the like, and is suitable for large-scale industrialized application.

Description

technical field [0001] The invention belongs to the field of chemical metallurgy, and in particular relates to a method for separating and recovering iron from red mud, which is suitable for the comprehensive utilization of waste red mud produced in the alumina production process. Background technique [0002] Red mud is a solid waste produced in the alumina production process. It is red because it contains a large amount of iron oxide, so it is called red mud. Red mud is a residue formed in a high-alkalinity sodium aluminate solution. Although rinsed with water, it is still alkaline, which brings great difficulties to the storage and utilization of red mud. The output of red mud is about 1 to 1.2 times that of alumina. At present, the annual output of red mud in the world exceeds 50 million tons, and the stacking of red mud has become a worldwide problem. [0003] In addition to residual alkali, red mud is mainly composed of alumina, silica, calcium oxide, iron oxide, etc....

AI Technical Summary

Problems solved by technology

Reduction of red mud by adding carbon after pickling can solve the problem of excessive alkali and iron oxide. However, the reduction process needs to be heated to 1300°C, which consumes a lot of energy and is not economically cost-effective, so it is difficult to apply in industry

The efficiency of leaching iron oxide in red mud with oxalic acid is very high, but the obtained iron oxalate solution has a slow solar decomposition speed, a fast ultraviolet light decomposition speed, and high energy consumption. The loss of oxalic acid during the photolysis process is serious, and the processing cost is high. accept

In addition, red mud is directly leached with oxalic acid solution to remove iron, and about 10% of the oxalic acid is converted into sodium oxalate or sodium hydrogen oxalate and other oxalates remain in the leaching residue, resulting in a large consumption of reagents for the red mud oxalic acid leaching process for iron removal , economically uneconomical

At present, there is no ideal comprehensive method of separating and recycling iron from red mud in the world, and a large amount of red mud can only be stored, causing serious waste of resources and environmental pollution

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