Decoding the role of surface area and hydroxyl groups in titanate nanostructures on fluoride adsorption

Adsorption, a simple, economical, and eco-friendly alternative to existing technologies, is a robust technique to remove fluoride ions present in groundwater. Current research mainly focuses on improving the adsorption efficiency and reducing the process time, energy consumption, and product cost. In this study, we developed tri-titanate nanorods (TNRs), a nanostructured adsorbent, with abundant adsorption sites and enhanced fluoride uptake capacity. TNRs were characterized using several techniques, including X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectroscopy, Sorption-based surface area analysis, and X-ray photoelectron spectroscopy. These results indicated that the adsorbent has hydrogen tri-titanate (H 2 Ti 3 O 7 ) as the predominant phase, one-dimensional nanorod morphology, and abundant surface hydroxyl groups. Detailed parametric studies revealed nearly seven-fold enhancement in fluoride removal by these one-dimensional nanorods compared to TiO 2 nanoparticles at optimal conditions. TNRs exhibit potential adsorptive properties, particularly at highly acidic pH, mainly through anion-exchange mechanism. This study further highlights a definitive relationship between material morphology, surface area, and adsorption capacity, illustrating how morphological features govern the exposure of surface hydroxyl groups, the key active sites for fluoride ion adsorption via ion-exchange mechanism. These findings provide new insights into the role of structural design in optimizing the adsorption performance of a material. • TNRs developed as nanostructured adsorbents for enhanced fluoride removal. • Beneficial role of hydroxyl groups as adsorption sites for fluoride ions. • Seven-fold enhanced fluoride removal by TNR compared to that of TiO 2 nanoparticles. • Established the correlation between morphology, surface area, and adsorption capacity. • Insightful findings for designing high-performance adsorbents for water treatment.