Development of titanium doped hydroxyapatite for efficient removal of radioactive strontium from contaminated water

Abstract

The present study explores the potential of hydroxyapatite (HA) and titanium-doped hydroxyapatite (Ti-HA) for the efficient removal of radioactive strontium (Sr-90) from contaminated water. Both the HA and Ti-HA were synthesized by the wet chemical precipitation method and characterized by X-ray diffraction, surface area analysis and scanning electron microscopy coupled with energy dispersive X-ray (SEM–EDX) techniques. Results confirmed the successful synthesis of HA and Ti-HA without changing the intrinsic crystal structure. SEM–EDX results showed a change in the morphology of HA from a needle-like shape to agglomerated sphere-like particles and confirmed the Ti doping. HA and Ti-HA showed 60.2 ± 1.8% and 86.3 ± 1.0% removal efficiencies for Sr(II), respectively, at an initial concentration of 100 μg mL⁻¹ in the pH range of 4 to 7. The adsorption data were well fitted with the Langmuir and Freundlich models. The kinetic data were in good agreement with the pseudo second-order model, indicating the chemisorption process. Thermodynamic data suggested the feasible, spontaneous, and endothermic adsorption of Sr(II) on HA and Ti-HA. The synthesized adsorbents were suitable for Sr(II) removal even in the presence of other interfering ions. Therefore, Ti-HA can be an efficient and promising adsorbent for the removal of Sr(II) from aqueous solutions.