Fluid dynamics simulation of highly loaded anion-exchange chromatography of Np(IV) based on adsorption isotherm determined by ^237+239Np

In order to investigate the optimum condition for anion-exchange chromatography for purification and recovery of actinide(IV) constituting transuranium elements, a convective-diffusion equation model treating mass balance and Langmuir-type kinetics in porous system, which was developed for thorium(IV) by us, was applied to neptunium(IV). Absorption isotherm of neptunium(IV) to anion-exchange (MSA-1) resin was carried out by using ^237+239Np in 6N HNO₃ media and hereby parameters of the Langmuir-type kinetics were determined as k₀ = 2.5 × 10³ and s_max = 1.0. Accompanied with the fluid dynamics parameters already determined for the column system used for ^227+232Th, elution curves of neptunium(IV) at highly loaded condition were estimated by the numerical calculation. According to the result, the loading of more than 10% of resin capacity leads to rapid breakthrough and severe tailing of neptunium which lowers purity and yield in the purification procedure. This numerical calculation will serve as a valuable measure to figure out column operation conditions for purification and recovery of transuranium elements.