Method for extracting rare earth from precipitation sludge of rare earth wastewater pool

Abstract

The invention discloses a method for recovering rare earth from precipitation sludge of a rare earth wastewater pool, comprising the main steps: firstly, preroasting the precipitation sludge of the rare earth wastewater pool, then leaching the roasted product with mineral acid to obtain a leach solution containing rare earth, and sequentially adding ammonium sulfate and oxalic acid to the leach solution so the rare earth is separated from soluble impurities in a manner of solid phase precipitation. The method has a simple process, convenient operation and low cost, solves the problem of difficult complete separation in a condition of coexistence of rare earth and calcium in a solution, can efficiently recover the rare earth in the precipitation sludge of the rare earth wastewater pool, and realizes separation of rare earth from calcium, aluminum and iron; the recovery rate of rare earth reaches above 99%; and the recovered rare earth oxide can be returned to a production main flow of a rare earth smeltery.

Description

technical field [0001] The invention relates to the technical field of industrial waste residue treatment, in particular to a method for recovering rare earths from sedimentation residues in rare earth wastewater pools. Background technique [0002] Rare earth is a non-renewable important strategic resource, and its consumption is increasing day by day. A large amount of wastewater is generated in the rare earth smelting and production process. Smelting enterprises usually need to be equipped with special wastewater pools for collection. There are many types of anions and cations in wastewater, and they are easy to combine to produce precipitation. Over time, a large amount of solid sediment residue will accumulate in the wastewater pool. The rare earth content in the slag can reach about 30%, accompanied by calcium, iron, aluminum and other metals. If it is not treated in time and effectively, it will not only cause a waste of precious rare earth resources, but also if the...

AI Technical Summary

Problems solved by technology

The precipitation method is relatively simple. Usually, by adjusting the pH, the rare earth is precipitated with rare earth hydroxide and separated from water. However, when the pH is not controlled properly, impurity metal ions such as Ca 2+ 、Al 3+ , Fe 3+ Co-precipitation of hydroxides will also be generated; and the formed precipitate particles are relatively small, even in a colloidal state, making it difficult to enrich the precipitate

When oxalic acid is used to precipitate rare earth, since the solubility of aluminum oxalate and iron oxalate is much greater than that of rare earth oxalate, the separation of rare earth from iron and aluminum can be realized, but the calcium ion in the solution is also easy to react with oxalic acid to form a precipitate, which is not conducive to the separation of rare earth and calcium. separate

The extraction method has a large enrichment factor and high efficiency, and can realize multi-stage series connection and automatic continuous operation. However, when the content of calcium, iron, and iron impurities exceeds the standard, it is easy to cause emulsification of the organic phase and difficulty in phase separation of the extraction system. After back extraction by special means, The content of impurity ions in the stripping solution is still difficult to reach the standard

Studies have shown that the rare earths in the sediment residue of the rare earth wastewater tank mainly exist in the form of oxalate and carbonate; and the sediment particles are small and densely packed, which makes acid leaching very difficult

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