Comparative study of Sc(III) sorption onto carbon-based materials

The sorption behavior of Sc(III) on different materials including activated carbon (AC), carbon nanotubes (CNTs), graphene oxide (GO), and the chelating resin Chelex 100 was investigated. In general, the sorption of scandium increases with increasing pH. For pH in the range from 2.5 to 5.5, the sorption of Sc(III) onto CNTs, GO, and Chelex 100 is quantitative, whereas a significantly lower amount of scandium ions was retained on AC. The specific amount of Sc(III) adsorbed at pH 2 attained 2.1, 2.9, 36.5, and 37.9 mg g−1 for AC-COOH, Chelex 100, GO, and CNTs-COOH, respectively. At pH 4, a similar value was obtained for oxidized AC (2.2 mg g−1), whereas the specific amount adsorbed significantly increased for Chelex (23.4 mg g−1). The highest values were obtained for GO (39.7 mg g−1) and oxidized CNTs (42.5 mg g−1). Better kinetic retention was observed at pH 2 for CNTs and GO, whereas at pH 4 the kinetic behavior of Chelex 100, GO, and CNTs toward Sc(III) was comparable.