Kinetics Study of Adsorption Behaviors of Trivalent Metal Ions onto Chelating Resin: Comparison between Scandium(III) and Other Metal Ions

Abstract

Scandium (Sc) lacks commercially viable independent deposits and is mainly recovered as a by-product of the smelting of other ores. In the process of recovering nickel from laterite ores, Sc is recovered from leaching solutions. The recovery of Sc requires its efficient separation and purification from other impurities. This study proposes a process for the selective separation and recovery of Sc from other trivalent cations in sulfuric acid solutions using an iminodiacetic acid chelating resin, Diaion™ CR11. The adsorption behaviors of trivalent ions Sc(III), Cr(III), Al(III), and Fe(III) onto CR11 in single- and multiple-metal systems were investigated to determine the appropriate Sc separation conditions. In systems containing single metal ions, pseudo-first-order and pseudo-second-order kinetic models were used to fit the data. Linear and nonlinear methods were used for fitting. The activation energies were calculated from the rate constants at a pH of 2.0 and at three different temperatures of 23°C, 60°C, and 80°C and followed the order: Cr(III) > Fe(III) > Sc(III) > Al(III). In binary systems including Sc(III), the simultaneous adsorption of Sc(III) and other trivalent ions onto CR11 was investigated. Previously adsorbed Sc(III) on CR11 was displaced by the subsequent adsorption of Fe(III) or Cr(III) from the solution. The affinity of the metal ions to iminodiacetic acid and the adsorption reaction rate were critical factors for suitable selective Sc separation, indicating that prior removal of Fe(III) was necessary. Column experiments at 23°C using a synthetic solution without Fe(III) showed that Cr(III) adsorption was suppressed, and that Sc(III) was efficiently adsorbed. Scandium can be efficiently recovered from a solution containing Sc(III) after prior removal of Fe(III) by adsorption at low temperature using CR11.