Aspects of the fundamental chemistry of cesium extraction from acidic media by HCCD

It is well known that cesium extraction from acidic media by HCCD proceeds through a liquid-liquid ion exchange extraction mechanism. Four data sets with 25 experimental measurements of Cs distribution ratios, D_Cs = [Cs]_org/[Cs]_aq, at a variety of initial conditions (various concentrations of [HCCD] and [HNO₃]) have been modeled using the SXLSQI computer program developed at ORNL. The SXLSQI program was used in this analysis to help elucidate the general chemical equilibria operative in the extraction of Cs⁺ into an organic phase comprised of HCCD in FS-13. The experimental data sets are best modeled with four chemical equilibria (T = 25°C). The equilibrium constant for the primary exchange reaction of log K_eq = 3.07 is in excellent agreement with values reported in the literature of log K_eq = 3.00 for the HCCD/nitrobenzene system. In general, the equilibria representing the mechanism of Cs extraction by HCCD are consistent with earlier literature reports, albeit derived by different experimental and modeling schemes.