Abstract
Bauxite residue is the voluminous by-product of alumina production after Bayer process. Its high alkalinity causes disposal problems and harmful environmental impacts. However, the residue contains significant amounts of valuable elements, such as rare earth elements, including scandium. Greek bauxite residue contains a high amount of scandium close to its main resources. Taking into account scandium’s limited availability coupled with its high demand in modern technology, bauxite residue could be considered as a potential resource for scandium recovery. In this study, the optimization of scandium extraction from bauxite residue with sulfuric acid is investigated using Taguchi methodology. Based on previous studies, acid molarity, leaching time, solid/liquid ratio, and reaction temperature were selected as control parameters for the selective Sc recovery. Method optimization targeted the highest concentration of scandium combined with the lowest concentration of iron without taking into account application constraints. Maximization of scandium concentration can be achieved only by reduced selectivity. The predicted values resulted from the Taguchi methodology were affirmed by a confirmation experiment conducted at optimal conditions. Regression analysis provided the respective equations to be applied on several conditions, depending on different applications.
Highlights
Bauxite residue (BR) or red mud (RM) is the by-product generated in alumina production after
Many investigations have been performed aiming for a low cost and environmental friendly treatment and utilization of BR in numerous uses [4,5,6], such as an agent in building and constructing materials [7,8,9,10], an agent in the ceramic and glass industry [11,12,13], as an adsorbent for pollutant removal from water and wastewater or in pigments [14,15,16,17,18,19], as a coagulant for waste and water treatment [20,21,22], an absorbent of waste acidic gases [23,24,25], an agent for neutralizing acidic waste and raw materials of low cost for the recovery of valuable elements [26,27,28,29,30,31,32,33,34,35,36,37,38], in catalysts [39,40], and as an agent for soil remediation [41,42,43,44]
Scandium ironTaguchi from bauxite residuedesign by sulfuric leaching depends concentration in the leachate solution is enhanced with high acid concentrations, elevated reaction significantly on the conditions used
Summary
Bauxite residue (BR) or red mud (RM) is the by-product generated in alumina production afterBayer process. Many investigations have been performed aiming for a low cost and environmental friendly treatment and utilization of BR in numerous uses [4,5,6], such as an agent in building and constructing materials [7,8,9,10], an agent in the ceramic and glass industry [11,12,13], as an adsorbent for pollutant removal from water and wastewater or in pigments [14,15,16,17,18,19], as a coagulant for waste and water treatment [20,21,22], an absorbent of waste acidic gases [23,24,25], an agent for neutralizing acidic waste and raw materials of low cost for the recovery of valuable elements [26,27,28,29,30,31,32,33,34,35,36,37,38], in catalysts [39,40], and as an agent for soil remediation [41,42,43,44].
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