Adsorption of Cadmium Species on Montmorillonite Investigated by 113Cd NMR Spectroscopy

Abstract

Abstract Increasing quantities of montmorillonite (1, 2, and 3% w/v) were added to aqueous CdCl2 solution ([CdCl2] = 4.11 × 10−2 M) and the change in the cadmium and chloride concentrations remaining in the supernatants were measured from the peak intensity and chemical shift data obtained from 113Cd NMR spectra. The decrease of cadmium concentration was not accompanied by any changes in the chloride concentration, indicating that only the free cadmium ion (Cd2+) is adsorbed on the negatively charged solid-surfaces of montmorillonite. A single peak at chemical shift of δ −8 was recorded in the 113Cd magic angle spinning (MAS) NMR spectrum of the sedimented montmorillonite. This value is similar to that obtained for the solid [Cd(H2O)6](ClO4)2, indicating that only Cd2+ ion is selectively adsorbed and are bound to oxygen donors of montmorillonite clays. Keywords: Montmorillonitecadmium speciesadsorption113Cd NMR