Enrichment of scandium by carbon nanotubes in the presence of calcium matrix

The sorption behavior of Sc(III) on oxidized carbon nanotubes (CNTs) for the separation and preconcentration of trace amounts of scandium ions from aqueous solutions was investigated. The mechanism of separation and the effects of pH, flow rate, sample volume and interferences, with special focus on calcium, on the recovery of Sc were systematically studied and optimized. Generally, the sorption of scandium increases with increasing pH. For pH in the range of 2.5–5.5 the sorption of Sc(III) onto CNTs is quantitative, but its removal in the pH range of 1–3.5 is mainly attributed to sorption, while at pH > 4 there is overlap with the precipitation curve, indicating insignificant sorption. The adsorbed amount of Sc(III) at pH 2.0 was 42.0 mg g− 1. The procedure was applied to the enrichment of scandium with ICP-OES detection for natural water analysis with a preconcentration factor of 250 and a detection limit (3σ) of 0.05 μg L− 1.