USE OF THE ION EXCHANGE METHOD FOR THE DETERMINATION OF STABILITY CONSTANTS OF RARE EARTH WITH FULVIC ACID

The stability constants of complexes of Eu,Gd,Tb,Yb with fulvic acid from weathered coal are determined using Schubert's ion exchange method and radioactive tracers. The range of stability constants is 108 - 1014,and the 1:1 and 1 : 2 binding sites complexes are the predominant species.Calculation methods based on Ardakani-Stevenson's ion exchange equilibrium method are developed for determining stability constants of metal with humic and fulvic acids. The methods are verified using Tb(Ⅲ)-fulvic acid from weathered coal. The stability constants range from 1011.93 - 1011.15 at pH 4. 7 and ionic strength 0. 1mol/kg.