A Concise Review on the Fungal Beneficiation of Kaolins

The existence of iron oxides in kaolin adversely affects the clay color, and reduces its brightness and refractoriness. These iron oxide/hydroxides may be hematite (red), maghemite (reddish brown), goethite (brownish yellow), lepidocrocite (orange), ferrihydrate (brownish red), etc. These cause a dramatic decrease in its commercial price. Application of bio-beneficiation to remove the iron oxyhydroxides from kaolinite clays has been the center of interest in recent decades since they are environmentally benign (neither use nor release hazardous chemicals), not energy intensive, low in initial and operational costs, and preserve the crystal structure of the clay, its organic component and refractoriness. Generally, fungi acidify the growth environment during respiration by the excretion of organic acids and consequently solubilize the metal compounds through protonation, complexation, or reduction. The present review offers the general concepts and fundamentals of the fungal bioleaching of iron impurities from kaolins along with an outline and critical assessment of the latest studies carried out on the mentioned procedure