Raman-XPS spectroscopy, REE chemistry, and surface morphology of Fe-Ti oxide heavy mineral sands: a case study from Varkala-Kovalam coast, south-west India

ABSTRACT The beach sands of the Varkala-Kovalam coast, south-west India, are enriched with heavy minerals with a high concentration of ilmenite followed by sillimanite, monazite, rutile, zircon, and garnet. The Fe–Ti oxide minerals such as ilmenite, its altered product leucoxene, and rutile were successfully recovered, and their structure, chemistry, and surface morphology were analysed using advanced characterisation techniques like Raman spectroscopy, Energy Dispersive X-ray Fluorescence (ED-XRF), High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS), Thermogravimetric Analysis (TGA), UV-Visible-NIR (UV-Vis-NIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM-EDS). The chemical composition, surface chemistry, the oxidation state of surface elements, anisotropic crystal behaviour of the minerals due to physical or chemical processes, discrimination of polymorphs, and finally the morphological changes due to mechanical impacts were also analysed. The study provides solid information to the scientific community and policymakers for determining the grade and potential applications of these strategic minerals.