Sorption of Pu(VI) onto TiO2

The sorption of Pu(VI) onto TiO2 was studied as a function of pH (210) and Pu concentration (10−810−4 M) under an N2 atmosphere, in 0.016 and 0.1 M NaClO4. A batch-wise method was used, in which pH was measured in separate experimental containers after removal of a sample to determine the amount of Pu that had been sorbed. As Pu is radioactive, it was used as a tracer and measured by liquid scintillation counting. No ionic strength dependence was discerned, which was taken as an indication of inner sphere complex formation. In the interval of pH 27 the system could be described by the formation of two positively charged surface complexes using a 1-pK Stern model. Sorption of the plutonyl ion (PuO22+) and the first hydrolysis species (PuO2(OH)+) was estimated using FITEQL to logK1=6.9 and logK2=1.4, respectively