Bisorption of chromium(VI) from aqueous solutions by Sargassum thunbergii Kuntze

The potential to remove Cr(VI) from aqueous solutions through biosorption using dried Sargassum thunbergii Kuntze was investigated with respect to initial pH, amount of biosorbent, initial Cr(VI) concentrations and temperature. Cr(VI) removal efficiency was influenced significantly by the variation of pH, and the optimum pH was about 2.0. Moreover, the biosorption kinetics followed the pseudo-second-order model. The adsorption equilibrium was well described by the Langmuir and Freundlich isotherm models. The maximum adsorption capacity was 1.855 mmol/g at 318 K and pH 2.0. The adsorption processes were endothermic and the biosorption heat was 15.8 kJ/mol. Furthermore, the Fourier transform infrared spectroscopy suggested that amido-, hydroxyl-, C = O and C-O groups were involved in the biosorption of Cr(VI) onto S. thunbergii.