Modeling Arsenite Adsorption on Rusting Metallic Iron

Abstract

Experimental data on As(III) adsorption by rusted zero valent iron (ZVI) could be modeled using a simple Langmuir isotherm model. However, the adsorption equilibrium was observed to shift with time, as continued rusting produced additional sites on the rusted ZVI surface for potential arsenic adsorption. A modified Langmuir isotherm model was formulated taking into consideration the temporal variation in the site concentration for potential arsenic adsorption on the rusted ZVI surface. This model simulated the long-term experimental data on As(III) adsorption quite well. The model was further refined by apportioning the arsenic adsorbed on the rusted ZVI surface into labile and irreversibly adsorbed fractions. Finally, the developed model was used to simulate the performance of an adsorption column. The simulation results indicate that an adsorption column of length 0.4 m and diameter 0.056 m, i.e., containing