Europium complexation by an aquatic fulvic acid - Effects of competing ions

Effects of competing ions, Fe2+/Fe3+ and Al3+, on Eu3+ complexation with an aquatic fulvic acid (FA), have been investigated using an ion exchange technique. The influence of different concentrations (10(-6), 10(-4) M) of the competing ions on the distribution coefficient for Eu was measured, and the overall complex formation function, B-ov, was resolved for the Eu systems with Fe and Al. All systems showed pH-dependent beta(ov)-functions. The presence of 10(-4) M concentration of competing 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 perturbing effect on Eu-FA complexation than Al. In similar competition studies Sr and Eu were found not to perturb each others complexation with fulvic acid, suggesting therefore that the two metals probably bind to different sites on the fulvic acid molecule. (C) 1997 Elsevier Science B.V.