Journal of Nuclear Fuel Cycle and Waste Technology

The effect of organic acids on the adsorption of U(VI) onto oxide surfaces (TiO2(anatase), SiO2(amorphous) and Al2O3(amorphous)) has been investigated. Two different organic acids, salicylic and picolinic acids, were used. Changes of adsorption ratio of U(VI), which depend on the existence of organic acids in a sample, were measured as a function of pH. Quantities of adsorbed organic acids, which depend on the existence of U(VI) in a sample, were also measured as a function of pH. It is confirmed that the soluble complex formation of U(VI) with organic acids can deteriorate the adsorption of U(VI) onto TiO2 surface. It is noteworthy that salicylic acid does not affect the adsorption of U(VI) onto SiO2 surface, however, picolinic acid enhances the adsorption of U(VI) onto SiO2 surface. The latter effect can be understood by considering the formation of a ternary surface complex on SiO2 surface, which was confirmed by the co-adsorption of picolinic acid with U(VI) and the change in a fluorescence spectra of U(VI) on surface. In the case of Al2O3, organic acids themselves were largely adsorbed onto a surface without deteriorating the adsorption of U(VI). This would support the possibility of a ternary surface complex formation on the Al2O3 surface, and an additional spectroscopic study is required.

Keywords

Adsorption,Oxide,Uranium(VI),Salicylic acid,Picolinic acid,Ternary surface complex