Sorption of uranium(VI) onto strontium titanate in KNO₃ medium

The sorption of uranium(VI) on the perovskite structure of strontium titanate in a 0.5M KNO₃ solution is studied. SrTiO₃ commercial material was characterized by XRD showing a tausonite face, with a specific area of 2.42 m² x g^-1. The electrical surface characterization of the compound was performed by mass and potentiometric titrations. pH_pzc in water was 8.5±0.3 and 9.1±0.2 in 0.5M KNO₃ solution, showing a positively charged surface. FITEQL 4.0 program was used to calculate the sorption curves and the surface acidity constants by the constant capacitance model obtaining: log K₁ = 8.67 and log K₂ = -9.43. The sorption edge was fitted with two different uranium(VI) species sorbed, corresponding to bidentate complexes of UO₂²⁺ and UO₂(OH)₂H₂O on the surface of strontium titanate. (author)