Immobilization of U, Ra, and Th compounds with analcime-containing rock and hydrolysis lignin

The capability of wood hydrolysis lignin and analcime-containing rock for immobilization of U, Ra, and Th from aqueous solutions of their salts and radioactively contaminated podzol soil was evaluated. The influence of pH and mineralization of the liquid phase on the uptake efficiency was examined. The sorption mechanisms were identified using sequential leaching procedure and IR spectroscopy. The analcime-containing rock sorbs U and Ra from weakly acidic model solutions, but in soil its sorption properties are inactivated. Hydrolysis lignin firmly absorbs radioelements from aqueous solutions and soil. The sorption firmness is determined by the kind of sorbates and soil contamination level. The maximal contribution of irreversible sorption for Ra, Th, and U reaches 60, 80, and 96%, respectively. The absorption properties of lignin are determined by specific features of its functional groups, structural irregularity, and capability to sorb low-molecular-weight organic compounds. As a result, physicochemical interactions by different mechanisms take place.