Characterization of kaolin from the Capim River region — Brazil

Abstract Kaolin has been intensively used as an industrial mineral, mainly in the paper industry, as coating or filler material. In order to achieve the market requirements for this kind of use, there are several beneficiation processes that kaolin should pass, such as grain size classification, chemical bleaching and magnetic separation. In this work, mineralogical, chemical and physical characterizations were carried out in kaolin samples from the mined ore in Capim 1 deposit being commercially exploited by Para Pigmentos S/A, before and after different steps of the industrial beneficiation processes. X-ray fluorescence and brightness measurement results indicate that all kaolin samples are typified by low iron content and high brightness grade. X-ray diffraction and scanning electron microscopy data exhibit kaolinite as the main mineral phase with minor amounts of quartz. The Hinckley index (> 1.06) as determined with XRD shows that all samples exhibit high structural order. From electron spin resonance and 57 Fe Mossbauer spectroscopy data we obtained essential information about the chemical nature of iron impurities. Results reveal that the highest improvement in kaolin properties is obtained when previous magnetic separation is included in the beneficiation.