Separation of traces of thorium from large amounts of uranium, by adsorption on lanthanum–ammonium oxalate

The separation of small amounts of thorium from large amounts of uranium was achieved by chromatographic columns loaded with ammonium–lanthanum oxalate LAOX, previously prepared and characterized. Good separation yields were obtained; the recovery of the elements was often greater then 95%. 234Th, naturally occurring in uranium samples, was used as a tracer of 232Th in order to study the behavior of thorium. The separation and preparation of a 234Th carrier free solution was also investigated. During thorium adsorption, trace amounts of uranium may be reduced to the +4 oxidation state. The adsorption step and the washing of the column, before thorium elution, were, therefore, run in the presence of a dilute H2O2 solution in order to prevent uranium reduction.