Potentiometric and spectroscopic study of uranyl complexation with humic acids.

By potentiometric study using a specific uranyl ion-selective electrode, the formation of 1:1 and 1:2 (metal:ligand) complexes of uranyl with various humic acids (HAs) was found. The conditional stability constants were calculated using the LETAGROP-ETITR program. Possible structures of the complexes are proposed. Stability constants were found to be rather high indicating that immobilized HA can be used, for example, to remove traces of uranyl from waste waters.

Humic acid capillary zone electrophoresis adsorption on capillary walls, separation in metal ion supplemented buffer and the fingerprints.

Capillary zone electrophoresis (CZE) in quartz tubes is often being used for the separation and characterization of humic acids (HA). A method was found to follow adsorption (and kinetics) of humic acids on a fused-silica capillary wall. It was shown that the adsorption of humic acids on an uncoated capillary wall is high. The effect on sorption of additives to the background electrolyte (BGE) was studied. Sorption can be eliminated by adding magnesium(II) salts (14-50 mM) to the BGE (pH 3.40) with resultant highly reproducible electropherograms as well as detailed and expressive fingerprints for HA of different origin.

The acidobasic and complexation properties of humic acids Study of complexation of Czech humic acids with metal ions.

The acid-base and complexation properties of humic acids (HAs) extracted from bohemian brown coals were studied. The acid-base behavior corresponds with the model of HA as a mixture of mono- and diprotic acids. This model was also verified on commercial HA substances (Aldrich and Fluka). HA binds strongly with heavy metal ions and the highest stability constant of HA-metal ion complexes was observed for copper(II). Stability constant values were found to decrease in the order: Cu(2+)>Ba(2+)>Pb(2+)>Cd(2+)>Ca(2+). Both acidobasic models for HA alone and those for HA-metal ion interactions were proposed and the computational methodology for polyelectrolyte equilibria studies demonstrated.