Effect of Humic Acid on the Electrophoretic Mobility of Uranium (VI) in Aqueous Solutions

Radiotracer study of the electrophoretic behavior of Eu and its complexes with humic acid

The interaction of Eu with purified/protonized Aldrich humic acid (HA) was studied by the free liquid/moving boundary electrophoresis used in combination with the radiotracer method. Introductory experiments were carried out to test electrophoretic behavior of Eu in HA-free solutions, and to determine mobility of Eu3+cation. To get the data for evaluation of parameters describing Eu binding to HA, titrations of HA (10 mg/L) with Eu were performed batchwise in the range 3.4×10-8-1.7-3M of Eu total concentration at pH 3, 4, 5 and 6, and 0.01 M ionic strength (NaClO4). In each batch, the degree of Eu complexation with HA was determined from152Eu electrophoretic mobilities in the cathodic direction. The experimental data were fitted with a discrete site model (Scatchard plot-like model) with two types of carboxylic sites. An additional information on the charge characteristics of the Eu-HA complexes has been obtained from the152Eu anodic mobilities.

Analytical separations of lanthanides and actinides by capillary electrophoresis

The separation of lanthanide and actinide elements belongs to one of the most challenging tasks of the separation science, due to a great similarity in their physical and chemical properties. The electrophoretic separation can be accomplished in the presence of suitable complex-forming agents, from which alpha-hydroxyisobutyric acid (HIBA) has been used most often. In the most effective capillary electrophoretic mode--capillary zone electrophoresis (CZE)--a complete separation of lanthanide ions can be accomplished within a few minutes. Various electrophoretic methods can be relatively easily adopted for the determinations of individual lanthanide elements in certain kinds of technical materials, concentrates, precursors, etc., where the high speed and low costs of analysis characteristics of capillary electrophoresis (CE) may be advantageously exploited. Electrophoretic techniques may also be employed for speciation studies, especially for examinations of the behavior of actinides in the environment.