Bioleaching of iron from highly contaminated Kaolin clay by Aspergillus niger

Kaolin is a clay mineral that has a wide application in the industry specially, in paper, ceramic, and porcelain manufacturing. One of the most important factors that affects the value of this raw material is its brightness. Unfortunately, with the iron oxides deposit on mineral particles during kaolin formation, much of this clay has become unusable for industries. So, several chemical methods have been applied in mineral processing plants to reduce these contaminants, but finding a more sustainable approach like biological methods have always attracted a great attention. In this work bioleaching of iron from a highly contaminated kaolin sample was carried out using two different strains of Aspergillus niger, and the effects of strain type, pulp density, and time of clay addition on the iron removal were investigated by employing a 23 full factorial design. Finally, it is concluded that strain type has the most significant effect on the response; also, the highest removal extent was 42.8% that was obtained by using the strain isolated from pistachio shell, and at the pulp density of 20 g/l when the clay was added at the beginning of the experiments.