Cation adsorption of NpO2+, UO22+, Zn2+, Sr2+, Yb3+, and Am3+ onto oxides of Al, Si, and Fe from aqueous solution: ionic strength effect

The effects of ionic strength on the adsorption behaviors of the monovalent cation NpO2+, the divalent cations UO22+, Zn2+, Sr2+, the trivalent cations Yb3+, AM(3+) onto Al2O3, SiO2 and Fe2O3 from aqueous solutions were investigated. It was found that depending on the adsorption system and solution condition, the ionic strength effects are promotive, reductive and insensitive to increasing ionic strength. Based on the comparison among the various effects of ionic strength on the various adsorption systems and the theoretical considerations, it may be concluded that the factors of ionic strength effect on cation adsorption are very complicated, that there are various effects on a certain adsorption system in the different pH ranges and different concentration ranges of background electrolyte, that the speciation of metals in aqueous solutions plays an important role in the cation adsorption, that the coulombic interaction and the chemical reaction could be directed towards the various ionic strength effects and that the satisfactory interpretation of various effects of ionic strength is very difficult to access and that ionic strength effect on cation adsorption is an open question and worthy of further study, because of the great practical importance and theoretical interest. (C) 2004 Elsevier B.V. All rights reserved.