Bioleaching of kaolin with Bacillus cereus: effects of bacteria source and concentration on iron removal
2020
Cheah, Wan Qi | Yong, Shih Nee | Chieng, Sylvia | Kuan, Seng How | Yap, Hao Jun
The presence of iron impurities in kaolin can negatively affect its whiteness index and refractory properties. Bacteria of the Bacillus species have been found to be effective in removing ferric ions [Fe(III)] from kaolin. This work examines the bioleaching of Fe (III) from kaolin using B. cereus. Two strains were tested: the first procured from an external laboratory and the second isolated from a kaolin sample. Bioleaching experiments were conducted at 30°C for five days. Changes in surface morphology of the kaolin were investigated using scanning electron microscopy, while chemical composition was analysed using energy dispersion X-ray spectroscopy. Dissolved Fe (II) concentration in kaolin leachates was measured spectrophotometrically using the phenanthroline method. Evident changes in the surface morphology of kaolin samples were observed in the presence of bacteria. Results also revealed higher Fe removal by indigenous B. Cereus strain UKMTAR-4 isolated from kaolin (53.9 %) compared to B. cereus procured externally (33.9%). When concentration of bacteria was progressively increased and bioleaching time extended to 10 days, presence of dissolved Fe (II) increased, indicating augmented bioleaching activity with increase of bacteria count.
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