Thermodynamic Adsorption States of TNT and DNAN on Corundum and Hematite

Adsorption isotherms are a critical tool in determining the transport of environmental contaminants through a particular media. Owing to the inherent heterogeneity of soils, the determination of which soil components are responsible for the adsorption and retention of a particular contaminant remains a challenge. In the current study, we consider several thermodynamic adsorption states in order to predict whether or not 2,4,6-trinitrotoluene (TNT) or 2,4-dinitroanisole (DNAN) would be either a ground-water contaminant or a soil contaminant. In order to reduce the complexity, we only consider two metal oxides (hematite and corundum) that are commonly found in arid regions. We have shown that TNT and DNAN bind favorably across all concentrations, temperatures, and surface hydration considered for alpha-Al2O3; however, only TNT was found to be bound for alpha-Fe2O3. Our results indicate that for soils rich in iron oxides, DNAN would be a ground-water contaminant.