Application of radiotracer techniques to a kinetic study of the interaction of Eu with humic acid

Abstract

Experimental methods based on the radiotracer technique have been designed to study kinetic aspects of the interaction of humic substances (HS) with metal ions. The rate of dissociation of Eu-HS complexes was observed via the rate of the isotope exchange in the system152Eu - stable Eu - humic acid (HA) determined by the diaphragm method. The rate of exchange was found to be enhanced by decreasing pH value, increasing ionic strength and increasing degree of loading of HA with Eu, and was described with a simple 1-component kinetic model (mono-exponential decay function). Additional information on the kinetics has been derived from the electrophoretic mobilities of Eu depending on metal loading of HA and pH, determined by the free liquid/moving boundary electrophoresis with radiometric and spectrophotometric detection of the electromigration of the Eu/Eu-HA complex.