Am(III) sorption onto TiO2 samples with different crystallinity and varying pore size distributions

Various parameters influence the kinetics and the thermodynamics (surface complexation) of cation sorption onto minerals, including the pHPZC, the pHIEP, the crystallinity, the pore size distribution, and the surface roughness. In this paper, we address the effect of two of these parameters, i.e., the crystal structure and the pore size distribution on Am3+/Eu3+ sorption onto crystalline (anatase) and amorphous TiO2 microspheres. For both samples, the sorbed cation speciation was found to be the same, as determined by time-resolved laser-induced fluorescence spectroscopy (TRLIFS). As determined from sorption studies, the variation in the crystallinity of TiO2 defines its рНPZC and has a dominant effect on the cation sorption onto a mineral surface, whereas the pore size distribution has a minor effect on the Am3+ distribution. Surface complexation data were obtained from sorption data that fits well with other cation sorption onto TiO2, as determined from the linear free-energy relationship (LFER).