Removal of Co2+ ions from aqueous solutions using iron-functionalized sepiolite

Abstract

The efficiency of iron-functionalized sepiolite for the removal of Co2+ ions from aqueous solutions was determined under different experimental conditions, using the batch method. The ionization constants of the surface functional groups of the sepiolite-iron system, determined from potentiometric titration data, were pK(a1)(int) = 6.7 +/- 0.1 and pK(a2)(int) = 10.2 +/- 0.1. The sorption experiments were performed as a function of initial metal concentration, initial pH value, and the equilibration time. The equilibrium process was well described by the Langmuir isotherm model. The pseudo-second order kinetic model provides the best correlation of the experimental kinetic data. The iron-sepiolite system had a noticeably higher Co2+ sorption capacity than the natural sepiolite sample as a result of higher specific sorption and a higher ion exchange capacity.