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Accession Number ADA583718
Title Sorption of VX to Clay Minerals and Soils: Thermodynamic and Kinetic Studies.
Publication Date Dec 2012
Media Count 106p
Personal Author A. M. Schenning K. B. Sumpter K. M. Morrissey R. L. Cheicante
Abstract Organophosphorus-based chemical warfare agents are unique military chemicals that are extremely toxic and could be found in the soils of military installations and former production facilities. Little data exists on the fate and transport of these chemicals in soil environments, particularly when the agent is present in low concentrations. This report summarizes data from a study in which isothermal titration calorimetry was used to examine the sorption of VX to clay minerals and soils. Thermodynamic characteristics such as observed enthalpy of binding, entropy, free energy, binding and dissociation constants, and saturation capacity were obtained. Complementary sorption/desorption profiles and batch equilibrium sorption isotherms were also generated during the study. Kinetic time-point samples were analyzed using a variety of analytical techniques to provide insights into the sorption pathways, and to distinguish sorption from degradation occurring in the bulk solutions. In a montmorillonite clay, there was a sharp break in the thermodynamic profile that corresponded to the lower critical temperature (LCT) of VX. The predominant mechanism above the LCT was an exothermic physisorption process, consistent with an ion exchange mechanism. Below the LCT, bimodal behavior was observed, with a second type of endothermic interaction occurring after the initial ion exchange.
Keywords Binding constant
Chemical warfare agents
Clay minerals
Dissociation constant
Exothermic reactions
Free energy
Gibbs free energy
Ion exchange
Isothermal titration calorimetry
Lower critical temperature
Settling rate
Vx agent

Source Agency Non Paid ADAS
NTIS Subject Category 48F - Geology & Geophysics
74D - Chemical, Biological, & Radiological Warfare
Corporate Author Science Applications International Corp., Gunpowder, MD.
Document Type Technical report
Title Note Final rept. Oct 2009-Sep 2010.
NTIS Issue Number 1402
Contract Number DAAD13-03-D-0017

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