Characterization of changes of low and high defect kaolinite after bioleaching

Two samples of well and poorly ordered kaolinites KG1 and KG2 (designated according to a Handbook for Clay Minerals) have been studied with the aim to describe their structure after biological leaching and removal of iron that decreases the refractoriness of products made of various kaolins. The influence of the biological treatment by silicate bacteria of Bacillus spp. on the process of impurities dissolution was evaluated by the changes occurring on the surface and in the structure of the minerals. The bioleaching of clays and extraction of Fe, Al and Si were per-formed during 100 days lasting incubation and the products were characterized by XRD, granulometric analyses, EDX and nitrogen adsorption techniques. The qualitative changes of the particles surface charge were measured by the electrophoretic mobility of particles in the electric field. (C) 2007 Elsevier B.V. All rights reserved.