STUDIES OF ADSORPTION AND LOCAL ENVIRONMENTS IN THE IRON SOIL MINERALS, LEPIDOCROCITE AND GOETHITE, BY MULTI-NUCLEAR SOLID-STATE NMR SPECTROSCOPY

Goethite (a-FeOOH) and lepidocrocite (g-FeOOH) are very common soil minerals and have large surface areas and strong uptake capacities for toxic cation and anions such as Cs⁺, Cd²⁺, Hg²⁺, and AsO₄^3- in the natural environment and industrial and nuclear wastes. Investigation of the molecular level mechanism of the adsorptions is very important to predict the destiny of the adsorbed toxic cation and anions. Solid-state NMR spectroscopy was used to acquire information about surface and bulk hydroxyl groups, which play a role in immobilizing adsorbates, and to study ion sorption itself and the binding sites and the nature of binding of toxic cation and anions in soil minerals. In this study, ²H, ^6,7Li, ¹³³Cs and ³¹P MAS NMR spectroscopy were applied to study the local deuteron environments and the adsorption of lithium and phosphate as model ions on iron oxyhydroxides, lepidocrocite and goethite.