Refinement of Low-Grade Kaolin by Microbial Removal of Iron Compounds

The objective of this study was to evaluate the effects of time on feeding a micro-organism by using maltose as a source of carbon and nitrogen in order to remove iron impurities from kaolin. Therefore, kaolin sample was provided from a deposit located in Abadeh, Fars Province, Iran. Since it contains high amount of iron oxides (6.1% Fe₂O₃), it is not suitable for sanitary manufacturing of ceramic body. X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) techniques were used in order to determine absolute amount of characterization and chemical contents of samples before and after leaching respectively. X Atomic absorption spectroscopy (AAS) analysis was performed to determine concentration of iron ions existing in aqueous solution of samples. Statistical analysis was completed by one Way ANOVA. Differences were considered significant if P<0.05. Scanning Electron Microscopic (SEM) equipped with EDS analysis of the sample was performed to get an atomic level chemical composition of the impurity minerals after bioleaching. According to AAS and XRD measurements, the Abadeh kaolin sample which was taken for this study has different types of impurity mineral species. The major iron impurity mineral species is hematite along with pyrite as minor secondary mineral. The results of EDS analysis confirmed that bioleaching had not made an important change in chemical composition of the samples. Statistical analysis showed that differences between all groups were significant (P<0.05). Regarding the decrease in iron impurity, the processed kaolin can be a suitable candidate to be used in ceramic and porcelain industries.