Carbonation Method of Extracting Gallium
Gallium is a rare metal on earth, and its extraction mainly depends on the conversion of gallium compounds in bauxite and other ores. A common way of gallium extraction is carbonation or hydrometallurgical lattice method. It has the advantages that the equipment is simple, the energy consumption is low and the environment is friendly, but the recovery rate of gallium is limited.
The carbonation process for extracting gallium includes two basic steps: acid leaching of raw materials and carbonation of gallium salts. In the stage of acid leaching, the ore is crushed, ground and mixed with sulfuric acid to leach out gallium, and then other insoluble substances are removed by filtration. The filtrate is neutralized and the formed gallium sols are heated to remove impurities further. In the carbonation section, the carbon dioxide gas is bubbled through the material, and ,the gallium salts react with carbon dioxide to form gallium carbonates. Finally, the gallium carbonates are recovered and converted back to gallium to complete the gallium extraction process.
As an important step in gallium extraction process, the carbonation reaction and mechanism of gallium salts are investigated. The gallium carbonates are basically insoluble or easily decomposed in water, and the conversion rate may be slow. The reactivity of the gallium salts is mainly measured by the decomposition temperature, but the decomposition temperature has a great relationship with the nature of the gallium salt, the type of the counterionic and the pH value . The carbonation reaction rate is also affected by other factors such as stirring speed, temperature, pressure, gas-liquid ratio and pressure drop.
In addition to the carbonation process, there are other process technologies for separating and extracting gallium, such as solvent extraction, ion exchange and electrochemical extraction. The combination of these processes can be selected according to the type of gallium ore and the affinity of gallium and other elements. For example, when the gallium ore contains another chloride or sulfate salt, the sulfate or chloride ion exchange may be combined with the carbonation process to realize the efficient extraction and separation of gallium.
Although the process of extracting gallium by carbonation is relatively simple and environmental friendly, the recovery rate of gallium is not very high due to the slow stability of the gallium carbonates. Therefore, optimizing the process parameters and further exploring other process technology combination is necessary to realize the high efficiency extraction of gallium.
