The Extraction of ¹³⁷Cs and ⁸⁹Sr from Waste Simulants Using Pillared Montmorillonite

ABSTRACT

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 173 and 182 A after calcination, and surface areas ranging from 71 to 264 m²g^-1. Both of the silica-pillared clays and the alumina-pillared clay exhibited excellent K_dsfor ¹³⁷Cs from simulated groundwater with values of 23,650, 23,260 and 144,570 mL/g, respectively. These were far better than the K_ds obtained by clinoptilolite and AW500 which had K_ds of only 14,560 and 9650 mL/g, respectively. None of the pillared clays showed a high selectivity for ⁸⁹Sr from groundwater or ^l37Cs 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 a precipitation mechanism rather than to ion exchange.

Key Words::

• Pillared clay
• Ion exchange
• Montmorillonite
• Groundwater