Sorption characteristics of neptunium by sodium-smectite

Abstract

The sorption characteristics of237Np by sodium-smectite have been studied by batch type sorption-desorption experiments over a pH range of 2 to 8. The association of237Np with smectite was examined by the sequential extraction technique in which 1MKCl and 1MHCl solutions were used as the extraction agents. Two kinds of neptunium-smectite association were identified by their characteristic desorption properties. In the first association, neptunium is desorbed from smectite by 1MKCl. In the second association, neptunium is stable in the basic solution but is desorbed by 1MHCl. The latter association was observed when neptunium was sorbed at low pH. Powder X-ray diffraction showed an expansion of the basal spacing of smectite from 1.25 to 1.48 nm in low pH solutions, consistent with specific sorption of neptunium at a H+expanded interlayer of smectite. © 1993 Taylor & Francis Group, LLC.