Rizo Vivas, Olga L.

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    Microscopic mass transfer of TNT on Ottawa sand
    (2006) Rizo Vivas, Olga L.; Castro-Rosario, Miguel E.; College of Arts and Sciencies - Sciences; Hernández-Rivera, Samuel P.; Briano-Peralta, Julio G.; Department of Chemistry; Mehta, Narinder K.
    Understanding the transport mechanism of buried explosives in soil is crucial in order to implement an effective system for their detection. A major recurring problem is the representation of diffusion processes of these compounds on soils due their different and complex properties. The aim of this work was to describe the transport of 2, 4, 6 –Trinitrotoluene (TNT) on Ottawa sand using a mathematical model. The microscopic mass transfer of TNT on sand particles was studied using Scanning Electron Microscopy (SEM) coupled to Energy Dispersed X-ray Fluorescence Spectroscopy (EDAX). Samples of TNT on sand were analyzed varying the mass of the explosive and modifying pH conditions of sand in function of time. The images obtained from SEM showed smooth differences in the morphology and spatial distribution of the explosive on sand a few hours after sample preparation. This change in morphology and spatial distribution was found to be dependent both on the mass ratio of TNT in the sample and the pH of the sand. On the other hand, EDAX measurements showed a decrease in the nitrogen fluorescence signal intensity demonstrating that movement of TNT into the sand occurs after about eight hours; carbon measurements showed a similar behavior during this time, that is called dead time. In addition, the kinetics of surface sublimation for TNT was studied. On the basis to the experimental results, a theoretical model incorporates parametric equations to explain a nonlinear sublimation rate of a solid TNT thin film in a very close proximity to the sand surface. A dependency of the diffusion constants and sublimation on the initial amount of explosive was found.