Study of Desorption of Contaminant from Synthetic Soil
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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A better understanding of sorption and desorption processes could improve estimates of time and cost required for remedial activities, exposure times and health risk, and bioavailability. Conventional rate-limited sorption models do not accurately define the diffusion domain at the grain scale. Heyse 1994 proposed the multiple sites in series MSS model, which allows more general description of the geometry of the sorption domain than the classical spherical or discrete distributions. A version of this model was tested by deVenoge 1996. The model was able to accurately simulate sorption rate data, but could not estimate unique geometry parameters. This research is to develop techniques to study desorption, and compare the results to the sorption study conducted by deVenoge 1996. This study examines whether sorption and desorption of anthracene by paraffin are reversible processes. The ability of the MSS model to predict geometry parameters was also tested. One finding of this study was the apparent volatilization of anthracene from wax during the heating and molding processes. This phenomenon may be responsible for the non-zero intercept of the desorption isotherm. It may have also confounded the initial conditions required by the MSS model in predicting the sorption distribution. If the initial concentration of anthracene in the wax is adjusted, the desorption process does appear to be the reverse of the sorption process. The equilibrium partition coefficients for sorption and desorption are similar. The diffusion coefficient appears to be faster for desorption than sorption, but this may have been affected by solvation of the paraffin. The MSS model did not successfully predict geometry parameters, possibly due to uncertain initial concentration in wax.
- Economics and Cost Analysis
- Soil Mechanics
- Water Pollution and Control