Chemical-Minerаlogical Characterization of Bauxites From Different Deposits

Abstract

From the aspect of their chemical and mineralogical composition, bauxites are very complex multicomponent raw materials. The paper presents the characterization of bauxite from several different deposits: Brazil, Milići, Čitluk and Kosovo. Chemical characteristics were determined by a combination of different analytical methods: gravimetry, potentiometric titration, atomic absorption spectroscopy (AAS) and UV-VIS spectrophotometry. Mineralogical composition was determined using X-ray diffraction and thermal analysis methods. Chemical and structural characterization is complemented by the results of scanning electron microscopy with EDX analysis. The information obtained was used for the assessment of the quality of investigated bauxites from the aspect of their application in the production of alumina.

A comparative review of the mineralogical and chemical composition of African major bauxite deposits

“…The largest deposits with higher concentrations and economic grade are to be found in tropical belts, between latitudes 300 N and 300 S [ 35 ]. It is a type of rock that consists of one or more aluminum hydroxide minerals [ 36 ], most notably gibbsite (Al(OH) 3 ), boehmite {γ-AlO(OH)} and diaspore {α-AlO(OH)}according to Bardossy & Aleva [ 37 ]. Though diaspore has the same general chemical composition as boehmite it is denser and harder.…”

“…In order to analyse extensively the quality of the Bauxite deposits with respect to alumina production, two criteria would be followed. Thus, the relative content of iron oxide and silica modulus, ; of the deposit as proposed elsewhere [ 7 , 8 , 21 , 36 , 51 ]. Other indicators of the Bauxite quality in relation to uses are given in Table 2 .…”

“…The quality of Ore deposit based on recognized classification, informs the use of a particular ore in industrial applications. Amongst the quality indices for Bauxite ore, are Silica modulus ( ), Ruxton ratio ( R ) and Chemical Index of Alteration ( CIA ) [ 8 , 16 , 21 , 25 , 36 , 51 ]. While The two indices; CIA and R ; help in determining the source of the parent rock for Bauxite ore; and that would be considered thoroughly in section 2.7.2…”

“…It was reported [ 16 , 21 , 36 , 51 ], that for the application of bauxite in alumina production it is important to determine the silica modulus. From both Table 3 , Table 4 , it is obvious the higher the silica modulus, the higher the quality of the bauxite as illustrated.…”

“…From both Table 3 , Table 4 , it is obvious the higher the silica modulus, the higher the quality of the bauxite as illustrated. Table 3 dwelt on raw quality and economic viability of the ore with no details [ 36 ]. However, as indicated by Yalcin [ 51 ], there is inverse relationship between the molar compositions of Al 2 O 3 and SiO 2 with respect to determination of the modulus using statistical and inequality analyses.…”