Retention of iron and chromium by an anion-exchange resin under decontamination conditions

The retention of iron and chromium ions on a strong base anion exchange resin (Lewatit M500 KR) in oxalic solution was studied by means of batch and column experiments. The tests performed indicate that more than 99% of the iron is uptaken by the resin, while chromium retention depends on the formation rate of the tri-oxalate complex. The experimental conditions required to improve chromium retention, such as temperature, pH, aging time, etc., were investigated and their consequences on the practical decontamination process are discussed. The available thermodynamic information for Fe(III) and Cr(III) oxalate complexes was reviewed and extended in order to determine the speciation in aqueous solutions in the range from 25 to 100 degrees C. That information would help in searching for the optimal experimental conditions for ion exchange removal of these ions.