Abstract:
Meetiyagoda Kaolin has both iron and titanium impurities which cause deep coloration in
it. Deep coloration in Meetiyagoda kaolin is the main barrier for most of the applications
where the higher whiteness is necessary. This study was aimed to purify kaolin and
enhance the whiteness properties by removing iron oxide impurities using
microorganisms under bioleaching method. Bacteria and fungi were isolated from iron
rich Meetiyagoda soil. Iron tolerated microorganisms were selected by inoculating the
isolated microorganisms in nutrient media impregnated with different known
concentrations of iron (200, 400, 600 and 900 ppm). Kaolin samples with three particle
sizes (125-150, 63-125, and less than 63 microns) were separately treated with the
screened microorganisms and the soluble iron concentration of the treated samples was
measured under different time intervals using Atomic Absorption Spectroscopy. Out of
screened bacteria and fungi types the most tolerated and the most suitable bacteria type
and fungi type to leach iron impurities was investigated. Bio leaching ability was
increased with the increasing particle size. The most convenient particle size was 125-150
microns. This biological treatment has shown one of the most effective processes for
removing iron impurities and enhancing the whiteness properties of kaolin. The study
concludes that the bioleaching method can be used for purification of kaolin in
Meetiyagoda by using soil microorganisms and it can significantly improve the quality of
kaolin from an industrial point of view.
Keywords: Kaolin, Bacteria, Fungi, Bioleaching
