Radionuclide separations using pillared layered materials

摘要

This is the final report of a two-year Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Pillared Layered Materials (PLMs) are layered inorganic ion exchangers propped apart by metal oxide pillars. PLMs have been synthesized to sorb strontium from liquid nuclear wastes. A study that compared over 60 sorbers for their ability to sorb strontium from Hanford simulants showed that PLMs were the best sorbers; strontium distribution coefficients ((sup Sr)K(sub d)) > 20000 mL/g were obtained. In addition, PLMs showed a high degree of selectivity for strontium over cesium, transition metals, lanthanides and actinides. The sorption of strontium is, however, inhibited by complexants (EDTA); (sup Sr)K(sub d) values drop to <20 mL/g when they are present. The most promising PLMs were the Cr, Ti, Zr, and Si pillared tantalum tungstate. The K(sub d) values for Sr(sup 2+) and Ba(sup 2+) show a strong pH dependence; K(sub d) values increase to >10(sup 4) above pH 12. The general surface complexation mechanism explains the sorption of these cations on PLMs.