Biosorption and retention of several actinide and fission-product elements by biomass fromMycobacterium phlei

The properties of mobile, 5% w/w cell suspensions ofMycobacterium phlei have been examined for their capacity to adsorb and retain uranyl(VI) and neptuny(V) cations from nitrate-buffered solutions at pH 1. Equilibrium conditions of sorption were attained after 3 hours for concentrations (C) in the range 0.015–18 mM cation and indicated a maximum specific adsorption capacity (Qe _max) of 182 mol/g dry biomass forC10 mM. NpO ₂ ⁺ generally showed higherQe values than UO ₂ ²⁺ at corresponding concentrations. Lixiviation tests with cation-loaded biomass in neutral and acidic media indicated that the extent of desorption did not vary extensively between pH 7 and pH 1 and did not exceed 3% for U and 1% for Np ions at pH 7 during 7-day periods of treatment. Analogous experiments with U-loaded biomass subjected to neutron activation prior to lixiviation enabled retention measurements for various fission-product isotopes produced in situ and showed that retention of²³⁹Np formed within the cellular matrix was >99% at pH 7 and 94% at pH 1.