Experimental and theoretical study of anion-exchange preparative chromatography for neptunium: The first application to thorium(IV) and its equilibrium and kinetics

In order to study equilibrium and kinetic parameters in anion-exchange chromatography for preparatory purpose, a quantitative model for nonlinear anion-exchange chromatography in porous media was constructed, by paying special attention to interstitial length along void structure (cm) distinguished from apparent length (cm*). Langmuir-type adsorption isotherm for thorium(IV), as a natural substitution for neptunium(IV), in 6 mol dm^-3 nitric acid to anion-exchanger MSA-1 (200-400 mesh) was investigated in batch-wise and chromatographic experiments. The equilibrium parameters determined by batch-wise experiments determined as k = 2.4 × 10² mol^-1 dm³ s^-1 and s₀ = 0.5 mol dm^-3 agrees very well with the values of k = 222 mol^-1 dm³ s^-1 and s₀ = 0.5 mol dm^-3 derived from fitting by the numerical calculation. Kinetic parameters of k_s and D affect band profile similarly, thereby maximum value of each parameter was evaluated as k_s = 1.3 mol^-1 dm³ s^-1 and D = 9 × 10^-4 cm² s^-1 by the numerical calculations.