Kinetics of sorption of some long-lived fission products on inorganic sorbents

Inorganic oxides: Fe3O4 (magnetite), Fe2O3 (hematite), Sb2O3, and MnO2 were used as granular sorbents for long-lived fission isotopes 137Cs+, 90Sr2+ and 60Co2+. The radioactive cations in aqueous solutions were at tracer concentration level, carrier free, 1.10-9mol Cs+/L, 2.10-10 mol Sr2+/L, and 6.10-12 mol Co2+/L. The sorption amount of these cations was determined by taking liquid aliquotes at desired time intervals from solutions over solid sorbents. The sorption of mentioned cations was investigated in the pH range from 2 to 10. Chemical and physical properties of the sorbents were obtained by conventional techniques. Simple mathematical models have been developed and applied to the obtained experimental data. The sorption kinetics up to first 60-90 minutes, in general, followed the first order equation. Some of the inorganic oxides showed high affinity towards certain radioactive ions, so magnetite removed about 60% of Cs+, hematite about 80% of Co2+, Sb2O3 proved to be a good sorbent for Sr2+, and MnO2 for Co2+. The observed difference in sorption capabilities is discussed in terms of crystal structure and surface properties of the solid phase. (author). 12 refs, 12 figs, 2 tabs