Kinetics of 1,4-Dioxane Adsorption by AmberSorb and Granular Activated Carbon

1,4-Dioxane is an emerging water contaminant that is likely to be carcinogenic to humans. Its treatment is challenging due to its high water solubility, low Henry's law constant, and low partition coefficients. Adsorption has been widely studied for removing 1,4-dioxane. Although the adsorption kinetics and isotherms of several water pollutants have been widely studied, little is known about the adsorption kinetics of 1,4-dioxane. In this study, the kinetics of 1,4-dioxane adsorption by AmberSorb and Granular Activated Carbon (GAC) were investigated. A homogeneous surface diffusion model was developed to describe the adsorption of 1,4-dioxane in continuous-flow and batch systems. The external mass-transfer and internal diffusion coefficients of 1,4-dioxane for AmberSorb (1.79 x 10(-3) cm/min and 3.52 x 10(-4) cm(2)/min) were determined about five- and thirty-fold larger than that of their corresponding parameters for GAC. For both adsorbents, the adsorption was limited by the mass-transfer across the fluid film that covers the adsorbent and the adsorbent-adsorbate interaction at the adsorbent surface but not limited by the diffusion within the adsorbent. While the mass-transfer across the external fluid film affected the maximum 1,4-dioxane removal percentage and the adsorption rate, the isotherm parameters mainly controlled the adsorption capacity and adsorbent service life.