UTILIZATION OF SEM-EDX AND FTIR IN THE CHARACTERIZATION OF SELECTED SOILS AND PERIWINKLE SHELL ASH

Abstract

This study presents an integrated framework for characterizing selected clay soils and periwinkle shell ash (PSA) utilising scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) and Fourier-transform infrared spectroscopy (FTIR) with a view to enhancing their geotechnical properties. Soils were selected and collected from six different locations within Ile-Ife and Ede areas of Osun State, Southwest Nigeria, for the study and periwinkle ash was chosen as the additive. The periwinkle shells were obtained from a dump site in Egbeda, Lagos State, Nigeria. The periwinkle shells were immersed or soaked in distilled water to remove the dirt, and thereafter sun-dried. Scanning electron microscope was used to determine the material's morphology, while the coupled energy-dispersive X-ray analysis determined the elemental compositions, and Fourier infrared spectroscopy (FTIR) was utilised to ascertain the functional groups. The results revealed that all the clays are aluminosilicates with hydrogen bonding; iron was detected in minute quantities, and the periwinkle shell ash had phosphates. It was established that, in the presence of phosphates and possible chemical reactions envisaged, there is formation of a hard and highly insoluble cementing compound [Al(OH)₂H₂PO₄.XH₃O] which is due to the occurrence of aluminum in high content in the selected soils. The integrated method is suitable for screening the mineralogical reactivity and potential engineering use of PSA in soil modification, but the interpretation must be supported by geotechnical and durability tests. This study concluded that the FTIR and EDX confirm the dominance of calcium and oxygen in the fired periwinkle shell with residual sodium and magnesium.