文摘
A large amount of coal gangue from coal mining and processing is regarded as waste and usually stockpiled directly. In order to recycle the valuable elements from the coal gangue, an integrated process is proposed. The process consists of three steps: 1) concentrating alumina from the coal gangue via activation roasting followed by alkali leaching of SiO2 which produces alumina concentrate for alumina extraction by the Bayer process; 2) synthesizing tobermorite whiskers from the filtrated alkali liquor containing silicate via a hydrothermal method and reusing excess caustic liquor; and 3) enriching titanium component from the Bayer process residue by sulfuric acid leaching. Alumina concentrate with 69.5% Al2O3 and mass ratio of alumina to silica (A/S) of 5.9, pure 1.1 nm tobermorite whisker and TiO2-rich material containing 33% TiO2 are produced, respectively, with the optimal parameters. Besides, the actual alumina digestion ratio of alumina concentrate reaches 80.4% at 270 ºC for 40 min in the Bayer process.