Removal of trivalent samarium from aqueous solutions by activated biochar derived from cactus fibres

The efficiency of activated biochar fibres obtained from Opuntia Ficus Indica regarding the sorption of trivalent samarium (Sm(III)) from aqueous solutions was investigated by batch experiments. The effect of various physicochemical parameters (e.g. pH, initial metal concentration, ionic strength, temperature and contact time) on the Sm(III) adsorption was studied and the surface species were characterized by FTIR spectroscopy prior to and after the lanthanide sorption. The experimental results showed that the activated biochar fibres possessed extraordinary sorption capacity for Sm(III) in acidic solutions (q(max)=90 g/kg, pH 3.0) and near neutral solutions (q(max)=350 g/kg, pH 6.5). This was attributed to the formation of samarium complexes with the surface carboxylic moieties, available in high density on the lamellar structures of the bio-sorbent.