Method for extracting metal gallium from coal ash

Abstract

The invention relates to a method for extracting metal gallium from coal powder ashes, in particular suitable for the ashes of a circulating fluidized bed. In the method, a mother liquor of sodium meta-aluminate is obtained through acid dissolving and alkali dissolving; then aluminum hydroxide is obtained simultaneously during enriching and spearing the gallium through carbon content by steps. The main steps include as follows: CO2 is led into the mother liquor of sodium meta-aluminate to carry out carbon content decomposing; the primary separation between the aluminum and the gallium is realized by primary carbonatation to filter out sodium hydroxide; secondary carbonatation is carried out on the filtrate to obtain the deposit of the complex salt of gallium and aluminum; a sodium carbonate crystal is obtained after the filtered filtrate is condensed and vaporized; the deposit of the complex salt of gallium and aluminum is dissolved in the mother liquor of sodium meta-aluminate; the processes are repeated until the proportion of gallium and aluminum in the complex salt of gallium and aluminum is larger than 1 / 340; then the complex salt of gallium and aluminum is added into the NaOH liquor and electrolyzed, thus obtaining the metal gallium with a purity larger than 99.9 percent which reaches the level of 3; simultaneously, the byproducts of the aluminum hydroxide and the sodium carbonate during the process of carbonatation by steps are obtained. The method has the advantages of simple technique, easy operation, low cost, high comprehensive benefits, and the like.

Description

Technical field:

[0001] The invention relates to a method for extracting metal elements from fly ash, and is especially suitable for the method for extracting metal gallium from fly ash in a circulating fluidized bed. technical background:

[0002] Gallium is a very important semiconductor material with a wide range of uses, but as a rare metal, gallium-containing mineral reserves are small and smelting is difficult. Therefore, the price of gallium in the international market is extremely high, and the market prospect is promising. Studies have shown that gallium content in fly ash in some areas is very high, reaching or even exceeding the deposit level. However, as a large coal-producing and coal-burning country in the world, the utilization of fly ash is still in its infancy. Circulating fluidized bed combustion technology (CFB) is a new type of clean coal combustion technology developed in the past 20 years. The ash and slag of circulating fluidized bed boiler not only...

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