Sorption of Tc(IV) and Tc(VII) on soils. Influence of humic substances

The technetium sorption behaviour in different samples of soils was studied under aerobic conditions. Tc(VII) was reduced to Tc(IV) by Sn2+ ions. About 99% of reduced technetium is absorbed by the soils under investigation. Sorption of TcO4- was studied in short-term (1-hour) and long-term (1-month) experiments. Sorption of TcO4- in presence of sodium humate (Aldrich) was generally lower than from pure water (from 99% to 12%) and depends on the depth of origin of the ground. Immobilization of TcO4- after sorption on superficial sample of soils was studied by paper chromatography. Oxidation of Tc(IV) in presence of NO3- and NO2- (concentration range 10-1 - 10-5 mol x dm-3) ions was studied as a function of time and concentration of NO3- and NO2- ions. The content of Tc(IV) in NO3- and NO2- solutions decreases with time (46 hours) relatively slowly. (author)