Scientists from the Siberian Federal University (SFU) have developed a comprehensive method for processing aluminum production waste to produce valuable metal - gallium. This was reported to RT by the press service of the Russian Ministry of Education and Science. The research results were published in the journal Hydrometallurgy.
Let us remember that gallium is a soft, brittle metal with atypical properties. It is capable of taking liquid form at a temperature slightly above room temperature, while practically not evaporating, which is why it is widely used in the production of modern medical thermometers. Moreover, gallium is a strategically important raw material; it is actively used in electronics, optics, satellite communications, and so on.
However, obtaining gallium is complicated by the fact that it is a trace element, that is, there are practically no gallium deposits; it is evenly distributed in the rock. In industry, gallium is obtained as a by-product of processing polymetallic ores or by burning coal. It is also found in fairly high concentrations in carbon-containing waste that is generated during the production of aluminum using electrolysis.
Gallium
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“Carbon concentrate is formed as a result of aluminum production and today is practically not processed, being considered waste,” Olga Buiko, a candidate of chemical sciences from the Siberian Federal University, noted in an interview with RT.
Today, a number of different techniques are used to obtain gallium from aluminum waste. For example, extraction technology is widely used, when the metal is extracted using a special solvent. However, as the authors of the study noted, this technology has a number of disadvantages: it is difficult to use on an industrial scale, and many solvents are flammable, toxic and expensive.
In the new work, scientists proposed an integrated approach to extract gallium.
Aluminum production waste
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The technology includes three main stages. At the first stage, aluminum production waste (carbon concentrate) is subjected to heat treatment at 600 ºС, the resulting ash is washed with a solution of hydrochloric acid, which washes out gallium from it. Then the strongly acidic solution is passed through a column filled with an anion exchange resin - granules of synthetic polymer sorbents. The sorbent removes gallium from the solution, while aluminum and other metals remain in solution. Next, the gallium complexes are “washed off” from the sorbent with distilled water.
“At the end of the process, the metal from alkalized and gallium-concentrated solutions is deposited, for example, “on gallama” (an alloy of gallium with aluminum), the so-called technical gallium is obtained,” continued Olga Buiko.
Scientists have selected optimal temperature conditions for waste combustion and solutions for effective leaching of gallium from ash.
According to experts, the proposed method for processing carbon-containing waste from the aluminum industry will not only produce valuable metal, but also reduce the volume of stored aluminum production waste.
Russia ranks second in the world in aluminum smelting, so it also has great potential in terms of gallium production, scientists noted. Now the main world supplier of this metal is China.