Assessing the Suitability of Alkaleri and Itobe Kaolins for High-temperature Refractory Evaporating Dish: A Comprehensive Comparative Study

This study presents a comprehensive comparative evaluation of kaolin deposits from Alkaleri (Bauchi State) and Itobe (Kogi State), Nigeria, with the objective of determining their suitability for producing high-temperature laboratory refractory evaporating dish. Raw kaolin samples from both locations were air-dried, pulverized, and characterized using a suite of advanced analytical techniques, including X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), particle size distribution (hydrometer method), and Atterberg limits. These analyses provided an integrated evaluation of the chemical, mineralogical, thermal, morphological, and plasticity characteristics of each deposit. The XRF results revealed that both kaolins are silica–alumina rich, but Alkaleri exhibited slightly lower Fe₂O₃ and TiO₂ contents, indicating higher purity critical for refractory ceramic performance. XRD patterns showed that Alkaleri kaolin contains better-defined kaolinite peaks, whereas Itobe contains proportionally more quartz and accessory minerals, suggesting lower crystallinity. The TGA–DTA results demonstrated a distinct and sharper dehydroxylation peak for Alkaleri at approximately 495°C, compared with 488°C for Itobe, signifying better structural ordering and higher thermal stability of the Alkaleri deposit. Similarly, weight-loss characteristics indicated more predictable thermal response for Alkaleri, a key requirement for firing stability in ceramic production. Hydrometer analysis confirmed high clay fractions in both deposits, though Itobe showed slightly coarser particles. Atterberg results classified both clays as CH (high plasticity), but Alkaleri displayed a marginally higher liquid limit and plasticity index, contributing to superior molding behavior. SEM-EDS analysis revealed more uniform, platy kaolinite morphology in Alkaleri, with fewer impurity clusters than Itobe, which exhibited irregular particle arrangements and more Fe-bearing inclusions. Overall, the combined mineralogical, chemical, thermal, and physicochemical characteristics indicate that Alkaleri kaolin possesses superior purity, crystallinity, thermal stability, and particle morphology, making it more suitable for producing high-temperature refractory evaporating dish. Itobe kaolin, while workable and plentiful, may require beneficiation or additional processing to meet the stringent requirements of laboratory refractory applications.