Optimal removal of iron impurities from kaolin by combination of Aspergillus niger & Bacillus subtilis

Abstract

Abstract This study was carried out to remove iron from kaolin using a biological method by two different species of Bacillus sp. and the combination of A. niger isolated from pistachio skin & Bacillus subtilis and comparing them with the control sample. The experiments were carried out for Bacillus sp. at 30 °C and 25 °C and for the combination of A. niger & Bacillus subtilis at 27 °C. The concentration of dissolved iron increased with increasing temperature in the samples treated with Bacillus sp. X-ray fluorescence spectroscopy results of the samples at 25 °C showed a reduction of 31.1% in Fe2O3 and Fe content and a reduction of 37% at 30 °C after 28 days. Therefore, iron removal by Bacillus subtilis at 30 °C achieves better performance than at 25 °C. X-ray fluorescence spectroscopy results of the samples treated with the combination of A. niger & Bacillus subtilis show a decrease of 49% in Fe2O3 and Fe content at 27 °C after 14 days. The results of colour measurement showed that kaolin powder treated with the combination of A. niger & Bacillus subtilis at 27 °C had the highest degree of whiteness compared to other samples.