SORPTION AND DESORPTION OF CONTAMINANTS FROM DIFFERENT HOST MATRICES

Thermogravimetric studies were run in air and nitrogen atmospheres, on sand/oil and sand/PCB mixtures, to determine the effect of surface area on the contaminant sorption and desorption. The contaminant sorption is dependent on the surface area. As the surface area increases, the contaminant concentration increases. In the case of desorption, the onset temperature decreases as the surface area increases. However, this phenomenon was reversed when the surface area included pore structure. An Arrhenius-type kinetic model was used to describe the surface area effects of contaminants with no pore structures on desorption. The model shows that the desorption does not depend on the type of gas (air or nitrogen), but does depend on surface area and contaminant concentration. In addition, the model showed two reaction regions for the desorption of contaminants from materials with pore structure. It was believed that the first region was volatilization of free contaminant at the host matrix surface. The second region is believed to be diffusion controlled, i.e., it is controlled by how fast the contaminant diffuses through the pores to reach the surface and is consequently stripped or volatilized.