Effects of phosphate and ionic strength upon uranium(VI) sorption onto alumina as a function of pH

Summary The sorption edges and the sorption isotherms of UO22+onto alumina were determined by a batch technique in the presence and absence of phosphate at pH range 3–6, ionic strength range 0.05–0.5 mol/L and UO22+concentrations 10-5–10-4mol/L. The dependence of sorption percentage of UO22+onto Al2O3as a function of initial concentration of phosphate was also investigated. The effects of phosphate and ionic strength on the sorption of UO22+onto Al2O3as a function of pH were emphatically investigated. It was found that the pH value and the presence of phosphate play a very important role in the UO22+sorption onto Al2O3, even if the concentration of phosphate is only a half of the concentration of UO22+. The sorption steeply increases with increasing pH from 3 to 6, and the sorption is enhanced with increasing concentration of phosphate at sorption percentage lower than 97%. The ionic strength is insensitive to UO22+sorption in the ionic strength range from 0.05 to 0.1 mol/L KNO3, while the sorption is slightly decreased with increasing ionic strength from 0.1 to 0.5 mol/L. The enhanced sorption of UO22+is attributed to the formation of ternary surface complexes involving UO22+and phosphate.