Shape evolution and size controlled synthesis of mesoporous hydroxyapatite nanostructures and their morphology dependent Pb(ii) removal from waste water

Abstract

Nanostructured hydroxyapatite (n-HAp) with tuneable morphology was successfully synthesized by varying the process parameters using a hydrothermal process with CTAB and PEG as surfactants. Systematic experiments were carried out to investigate the influences of process parameters on morphology. The morphology of n-HAp can be modified from nanorods to spheres by replacing the surfactant CTAB with PEG. The prepared materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The specific surface area (SSA) and pore size were determined by N₂ adsorption–desorption isotherms. The obtained specific surface area of the nanorods is greater compared to the nanospheres of HAp. These nanostructures of HAp have been used for removal of Pb(II) ions from waste water. The kinetic mechanism was best described by a pseudo-second order model and the isotherm data were fitted well by the Langmuir isotherm and Freundlich model. The adsorption of Pb(II) was found to be 714.14 and 526.31 mg g⁻¹ for the HAp nanorods and nanospheres respectively. The effect of pH, contact time and initial concentration of Pb(II) were also studied through batch experiments.