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.
Compliance with ethical standards
Conflict of interest. The authors declare that there is no conflict of interests with regard to this study.
Ethical approval All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. This article does not contain any studies with human participants performed by any of the authors.
The authors express their appreciation to the Karaj Materials and Energy Institute and Dr. Pazouki, who lent their support to this project.
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