Alkaline digestion behavior and alumina extraction from sodium aluminosilicate generated in pyrometallurgical process
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In pyrometallurgical process, Al- and Si-bearing minerals in iron and aluminum ores are easily transformed into sodium aluminosilicates in the presence of Na2O constituents, which alters the leaching behaviors of Al2O3 and SiO2. It was confirmed that sodium aluminosilicates with different phase compositions synthesized at various roasting conditions were effectively digested in the alkaline digestion process. Under the optimum conditions at temperature of 100–120°C, liquid-to-solid ratio (L/S) of 10:2 mL/g, caustic ratio of 4, and Na2O concentration of 240 g/L, the actual and relative digestion ratio of Al2O3 from the synthesized sodium aluminosilicates reached maximums of about 65% and 95%, respectively, while SiO2 was barely leached out. To validate the superior digestion property of sodium aluminosilicate generated via an actual process, the Bayer digestion of an Al2O3-rich material derived from reductive roasting of bauxite and comprising Na1.75Al1.75Si0.25O4 was conducted; the relative digestion ratio of Al2O3 attained 90% at 200°C.
Keywordsalumina sodium aluminosilicate roasting alkaline digestion Bayer process
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This work was financially supported by the National Natural Science foundation of China (Nos. 51234008 and 51174230) and the Program for New Century Excellent Talents in University of Ministry of Education of China (No. NCET-11-0515). The authors also gratefully acknowledge the Co-Innovation Center for Clean and Efficient Utilization of Strategic Metal Mineral Resources.
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