Abstract
The effect of fulvic acids (FA) on the sorption of europium(III) ions from aqueous solution onto Gluhovsky kaolinite and Cherkasky montmorillonite was studied. Sorption of Eu(III) ions onto the mineral surface increased as the pH value of the aqueous solution increased from 1 to 8, but decreased when fulvic acids were present in solution. Over the concentration range studied, Eu(III) ion sorption occurred as free europium ions which were not bound as fulvate complexes. At pH ≥ 6 and at high Eu(III) ion concentrations (> 200 μmol/dm3), the increase in europium ion adsorption in the presence of fulvic acids was twice that observed in their absence. This demonstrated the formation, under these conditions, of a two-nucleus complex with a chain of the type sorbent-Eu-FA-Eu. In natural waters at pH > 6, Eu(III) exists mainly in the form of soluble complexes where binding occurs via the oxygen atoms of the phenol groups in FA.