The Extraction of 137Cs and 89Sr from Waste Simulants Using Pillared Montmorillonite
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Two samples of a silica-pillared montmorillonite produced using 3-aminopropyltrimethoxy silane and an alumina-pillared montmorillonite were evaluated for the removal of 137Cs and 89Sr from a simulated nuclear waste solution and a simulated groundwater, and the results were compared to the parent montmorillonite and two zeolites, AW500 (chabazite) and clinoptilolite. The parent and pillared clays were characterized using x-ray powder diffraction and surface area analysis by nitrogen adsorption/desorption studies. The pillared clays exhibited d-spacings of between 17.43 and 18.32 Å after calcination, and surface areas ranging from 71.3 to 264.4 m2.g-1. Both of the silica-pillared clays and the alumina-pillared clay exhibited excellent Kds for 137Cs from simulated groundwater with values of 23650, 23260 and 144 570 mL/g, respectively. These were far better than the Kds obtained by clinoptilolite and AW500 which had Kds of only 14 560 and 9650 mL/g, respectively. None of the pillared clays showed a high selectivity for 89Sr from groundwater or 137Cs from simulated alkaline tank waste. They did, however, show a slight selectivity for 89Sr in the simulated Hanford tank wastes, but this is thought to be due to precipitation mechanism rather than to ion exchange.
author list (cited authors)
Sylvester, P., & Clearfield, A.