U(VI) sorption on illite in the presence of carbonate studied by cryogenic time-resolved laser fluorescence spectroscopy and parallel factor analysis

Mei, H.  ; Aoyagi, Noboru   ; Saito, Takumi*; Tanaka, Kazuya  ; Sugiura, Yuki  ; Tachi, Yukio  

The sorption of U(VI) on illite at different pH and dissolved inorganic carbon (DIC) levels was investigated by using batch experiments, surface complexation modeling, and cryogenic time-resolved laser fluorescence spectroscopy (cryo-TRLFS) combined with parallel factor analysis (PARAFAC). The inhibiting effect of DIC on U(VI) sorption was revealed by the macroscopic batch experimental results. An updated 2-site protolysis non-electrostatic surface complexation and cation exchange model considering the formation of two uranyl-carbonate sorption complexes was able to reproduce the experimental results well. Based on the PARAFAC analysis on the cryo-TRLFS spectra, there was clear correspondence in the variation trend of the derived components with the sorption species from the modeling results, validating the formation of ternary uranyl-carbonate sorption species.