The effects of ionic strength and of ethylenediamin et etraacetic acid (EDTA) on the sorption of uranyl ion, UO22+, to SiO2·xH2O (silica gel) were investigated. It was observed that pH and the ions present in the supporting electrolytes influence the
ionic strength effects. The presence of different sodium salts in the concentration range (0.20 to 1.40M) suppressed the sorption
of UO22+ in the order: NaNO3 < NaClO4 < NaCl < NaOCOCH3 < Na2SO4 [pH 2.75(±0.05)], while the presence of perchlorate salts of Li+, Na+ and Ca2+ (0.20 to 1.40M) promoted the sorption of UO22+ on silica gel in the order: LiClO4∼NaClO4<Ca(ClO4)2 at pH 2.80(±0.05). The ionic strength effect on UO22+ sorption was studied in presence of EDTA (0–1.00·10−3M) in the pH range 2.90 to 5.57. The sorption data and speciation calculation suggest negligible complexation of UO22+ with EDTA at I≥1.00M NaClO4.