Ambient temperature synthesis of nanorod 6-line ferrihydrite and its cation sorption behavior

Abstract

Nano-structured rod-shaped particles of 6-line ferrihydrite were synthesized at ambient temperature under controlled conditions. The phase formation was confirmed through X-ray diffraction (XRD). Shape and size of the particles were observed by transmission electron microscopy. Batch sorption studies for Pb(II), Cd(II), and Cu(II) were carried out. A pseudo second order rate model fitted to the kinetic data was obtained for the three cations. By increasing the pH from 2.0 to 5.3, sorption of the three cations increased. At a pH of 5.3, maximum loading capacities were 0.4, 0.7, and 0.9 mmol g-1. The isothermal data for Pb(II) and Cu(II) fitted to the Langmuir model, the Cd(II) data to a Freundlich isotherm. Cu(II) uptake increased with an increase of Cl- concentration, that of Cd(II) decreased. The Pb(II) uptake capacity passed through a maxima of 25 mg L-1 Cl-. Presence of [image omitted] had beneficial effect on the sorption of both Cu(II) and Pb(II) but affected Cd(II) sorption adversely. Depending on the sorbed metal ion, XRD results showed disappearance, shift in d-values, or variation in relative intensities. The sorption from solutions containing two or all three of the metal ions exhibited some selectivity.