Leaching Kinetics of Bauxite in Hydrochloric Acid

Evaluation of Ceramic Properties of Bauxitic Materials from SE of Iberian Range

“…Other studies have shown that iron oxy-hydroxides can deteriorate the refractory properties, cause deformation and decrease the melting point [16,18]. On the contrary, the high content of iron in sample F2-Y did not significantly affect its properties, as the reduction of hematite to magnetite started from 1300 • C, and hematite remained stable up to 1500 • C. However, iron content did impact the color of F2-Y and FR-9, which changed between 1300 and 1350 • C. In terms of alkali content, the relatively high K 2 O content in sample FR-9 (0.47%) appears to have affected its linear shrinkage at 1200 • C and the formation of micro-cracks at 1400 • C. It is known that even low concentrations of alkaline components can decrease the melting temperature [20][21][22].…”

“…In silica-aluminum systems, mullite melting starts at 1828 • C, while the presence of iron decreases the melting point down to 1205 • C [18,19]. Alkaline and alkaline earth oxides constitute fluxes, which decreases the melting temperature even at low concentrations [20][21][22]. Free silica also reduces the refractory properties and the quality of the final product due to its contribution to increased contraction of the refractory [23,24].…”

Mineralogical and Physical–Chemical Characterization of a Bauxite Ore from Lages, Santa Catarina, Brazil, for Refractory Production

“…Silica and titania contents are in the expected limits, and zirconia, SO 3, P 2 O 5 , and Nb 2 O 5 contents are very low; thus, these oxides do not deteriorate the bauxite characteristics as a refractory material. One way to decrease the iron content from the bauxite is leaching it in acid solution in order to remove this element (Jenkins and Sinha 1995;Zafar 2008). After submitting the natural bauxite to chemical leaching using hydrochloric acid, the bauxite iron content decreased from 5.8%wt.…”

“…The free silica content must be low because this component is only desired for mullite (3Al 2 O 3 Á 2SiO 2 ) formation, which contributes in decreasing the dimensional variation of the refractory when it is submitted to high temperatures (Gualtieri and Bellotto 1998;Fielitz et al 2007). In order to avoid the formation of invariant points with low melting temperatures, the alkaline and alkaline earth oxides are allowed in low concentrations (Jenkins and Sinha 1995;Wang et al 2004;Hyun et al 2005).…”

“…These ores form the primary mineral assembly, which, in proper temperature and drainage conditions, as a result of the weathering, transform themselves into a secondary assembly composed of gibbsite and goethite or halloisite=kaolinite and goethite (Pascoal and Pandolfelli 2000;Mutakyahwa, Ikingura, and Mruma 2003). Bauxite weathering is a process that involves silica and alkalis lixiviation, which results in alumina concentration (Jenkins and Sinha 1995;Zafar 2008). The formed bauxite deposit can reach up to approximately 5.10 6 tons, with Al 2 O 3 content higher than 50%.…”