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 wa s achieved by chromatographic columns loaded with ammonium-lanthanum oxalat e LAOX, previously prepared and characterized. Good separation yields were obtained; the recovery of the elements was often greater then 95%. Th-234, naturally occurring in uranium samples, was used as a tracer of Th-232 in, order to study the behavior of thorium. The separation and preparation of a 234Th carrier free solution was also investigated. During thorium adsorpti on, 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 prev ent uranium reduction. (C) 1999 Elsevier Science Ltd. All rights reserved.