EUROPIUM COMPLEXATION BY AN AQUATIC FULVIC-ACID - EFFECTS OF COMPETING IONS

Effects of competing ions, Fe2+/Fe3+ and Al3+, on Eu3+ complexation wi th an aquatic fulvic acid (FA), have been investigated using an ion ex change technique. The influence of different concentrations (10(-6), 1 0(-4) M) of the competing ions on the distribution coefficient for Eu was measured, and the overall complex formation function, B-ov, was re solved for the Eu systems with Fe and Al. All systems showed pH-depend ent beta(ov)-functions. The presence of 10(-4) M concentration of comp eting ion reduced the resolved complex formation function (log beta(ov )) for Eu complexation with fulvic acid by 0.6 and 0.4 log units at pH 5 for Fe and Al, respectively. This indicates that Fe has a more pert urbing effect on Eu-FA complexation than Al. In similar competition st udies Sr and Eu were found not to perturb each others complexation wit h fulvic acid, suggesting therefore that the two metals probably bind to different sites on the fulvic acid molecule. (C) 1997 Elsevier Scie nce B.V.