The Removal of Pertechnetate from Aqueous Solution by Synthetic Hydroxyapatite: The Role of Reduction Reagents and Organic Ligands

The use of knowledge from technetium radiochemistry (even from nuclear medicine applications) allows us to select an sorbent for Tc radionuclide sorption, which is hydroxyapatite. Using radioisotope indication, the TcO₄ sorption process on synthetic hydroxyapatite was studied by the batch method in the presence of SnCl and FeSO reducing agents. The complexing organic ligands' effect on the TcO₄ sorption under reducing conditions was investigated. In the presence of Sn ions without the addition of organic ligand, the sorption percentage reached above 90% independently of the environment. In the presence of Fe ions without the addition of organic ligand, the sorption of TcO₄ was significantly lower and was at approximately 6%, depending on the concentration of Fe ions in solution. The effect of complexing organic ligands on the TcO₄ sorption on hydroxyapatite from the aqueous solution, acetate buffer and phosphate buffer decreases in the following order for Sn : oxalic acid > ethylenediaminetetraacetic acid > ascorbic acid. In the presence of Fe ions without organic ligands, the sorption reached up to 15% depending on the composition of the solution. The addition of oxalic acid and ascorbic acid increased the sorption up to 80%. The ethylenediaminetetraacetic acid had no significant effect on the sorption of technetium on hydroxyapatite.