INDUSTRIAL CHARACTERISTICS OF SOME KAOLINITIC CLAYS AROUND ILUKUNO AND ISAN-EKITI, SOUTHWESTERN NIGERIA

Abstract

This research work assesses the industrial characteristics of Ilukuno and Isan-Ekiti kaolinitic clays for sustainable development. Geological field studies shows that Ilukuno is characterized by the occurrence of migmatite-gneiss quartzite complex with super crustal rocks, meta-sediment is composed of mica schist and quartzites. pegmatites here are emplaced into a series of schist and gneisses with intercalated amphibolites, while Isan-Ekiti and its environs is underlain by gneisses, granite and charnockite The gneisses are essentially migmatite which grade into biotite gneiss in some areas, contact relationship indicates that it is the country rock into which the other rocks are emplaced. Five (5) representative clay samples each were collected at Ilukuno and Isan-Ekiti from which their particle size distributions, bulk chemical and mineralogical compositions, firing properties and bleaching properties were determined. Vertical Electrical Soundings were used to evaluate the clay thickness, reserve and in the design of exploitable zones of the clay occurrences. The linear shrinkage varied from 2.9% to 3.5%. In Isan samples, specific gravity varies from 2.5- 2.53 and 2.54-2.60 in Ilukuno clay. Water absorption capacity of Isan clay samples ranges from 11.7 to 12.6% Ilukuno clay neither show any shrinkage when fired nor appreciable weight gain was when soaked in water. XRF analysis indicated that Ilukuno clay samples have an average SiO2, Al2O3 and H2O+ contents of 43.86%, 40.14%, 12.42% and Isan clay samples have 54.79%, 27.66% and 10.73% of SiO2, Al2O3 and H2O+ respectively. XRD analysis indicate that the dominant mineral in both Ilukuno and Isan-Ekiti clay samples is kaolinite. Ilukuno clay contains kaolinite (88%), quartz (7%) and illite (5%), while Isan clay has kaolinite (75%), quartz (14 %) saponite (4%) and illite (7%). On the firing test, changes in colour in Isan clay indicated brown to light brown while Ilukuno clay indicated white. The bleaching assessment for the natural and activated clay show colour improvement varied from 8.5% - 9.2% in Isan-Ekiti raw samples and between 3.2 - 5.2 % in Ilukuno raw clay samples. Upon activation with increasing HCl concentrations, there was increase in the readings of oil reduction from 23.5% - 47.4% in Isan clay samples, Ilukuno clay samples however show only a slight increment in colour reduction from (7.2% -12.3%) as the concentration of the HCl used for activation increased from 1M to 3M. Vertical Electrical Soundings show a profile of 2 to 5 layers which include: the topsoil, lateritic clay, kaolinitic clay, weathered and fresh basement. The Ilukuno clay is non- cohesive and consequently non-plastic. Firing tests showed that the clays are good for ceramics and refractories. However, an increase of fluxing agent is needed to improve the mechanical performance of the ceramic products.