Sorption of uranyl ions on gibbsite: effects of contact time, pH, ionic strength, concentration and anion of electrolyte

The sorption of UO22+ on gibbsite was determined at differing experimental conditions. The effects of contact time between the solid phase and aqueous solution, pH, ionic strength (background electrolyte KNO3), concentration of UO22+ and anion of electrolyte (KH2PO4 or KCl) were investigated. The sorption was rapidly increased in the first 30 h, then remained constant in the period 30-50 h and was slightly decreased after 50 h. It was found that the sorption is abruptly increased with increasing pH in the range 3-6; is slightly decreased with increasing ionic strength from 0.01 to 0.1 mol/L KNO3 solutions; that the sorption remains, respectively, constant at pH = 3, 4 and 5 in the concentration range of UO22+ 1.5 × 10−4 to 5 × 10−4 mol/L and enhanced at pH < 6 in the presence of 0.001 mol/L KH2PO4 and reduced at pH range 2-9 in the presence of 0.001 mol/L KCl.