EUROPIUM BINDING BY AN AQUATIC FULVIC-ACID - INTERACTION FUNCTIONS FOR THE AVERAGE SITES IN THE FULVIC-ACID MOLECULE

The interaction of a well characterized aquatic fulvic acid, Bersbo FA, with Eu3+ has been studied using ion-exchange distribution studies and an ultrafiltration method. The results indicate that values of overall stability constants, Q(MFA), obtained in the ion-exchange distribution studies (log Q(MFA) = 6.00-8.55), which increased with increasing pH, were higher by as much as two to four orders of magnitude than those obtained using the ultrafiltration technique (log Q(MFA) approximately-equal-to 5.10), and which were insensitive to changes in pH. Formation constants for the complexation of Eu3+ by the various acidic moieties identified in the fulvic acid have been resolved by an iterative procedure taking into consideration the contribution due to separate phase effects. The environmental implications of the studies are discussed.