Effect of Microwave Roasting on Aluminum Extraction from Diasporic Bauxite-Sodium Carbonate-Calcium Hydroxide Mixtures
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The effect of microwave roasting on aluminum extraction from mixtures of diasporic bauxite with sodium carbonate and calcium hydroxide has been studied. The phase constitution and leaching performance of the clinkers were studied under different roasting conditions. Dielectric and thermal investigations on raw slurry obtained from the mix revealed prominent microwave absorption characteristics. X-ray diffraction patterns established significant promotion of NaAlO2 phase. In the microwave field, the aluminum (Al)-bearing minerals, viz. AlOOH and Al2O3, reacted with Ca(OH)2 to form calcium aluminate and calcium aluminum silicate phases at rather low temperature in short time. Furthermore, increasing the temperature and time promoted the reactions of AlOOH and Al2O3 with Na2CO3 to form NaAlO2, resulting in high Al leaching rates. Remarkably, the Al extraction of the clinker microwave roasted at 800°C for 45 min was 82.24%, while the leaching rates of Na and Si were 90.2% and 8.4%, respectively.
The authors acknowledge the financial support provided by China Postdoctoral Science Foundation Grant (2018M633424), Applied Basic Research Program of Yunnan Province (2015FA017), the first batch of Yunnan Provincial Postdoctoral Research Fund Project, Yunnan Province Post-Doctoral Training Fund in 2018, and Kunming University of Science and Technology for Post-Doctoral Fellowship.
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