Modeling arsenic(V) removal from water by sulfate modified iron-oxide coated sand (SMIOCS)

The batch kinetics of arsenic(V) on a novel media developed by coating BaSO4 and Fe on quartz sand, known as sulfate modified iron-oxide coated sand (SMIOCS), was investigated. Batch rate data were analyzed using active available site and chemical reaction rate models. The batch kinetic data were a better fit on an active, available site model as compared to a chemical reaction rate model. The media was characterized for certain chemical properties and surface area. The media showed alkali resistance with the presence of iron, barium, and sulfur on the surface. The Langmuir and Freundlich isotherm equations could be used to describe the partitioning behavior of system at different pH. The removal of As(V) on SMIOCS was pH dependent and maximum removal was observed in acidic pH range. The variation in ionic strength and chloride (Cl-) concentration in the solute do not play a significant role in As(V) removal efficiency but major anions showed some reduction in As(V) removal efficiency. A very small concentration of silica drastically reduced arsenic removal efficiency. However, the presence of Ca2+ and Mg2+ as cations improved arsenic(V) removal efficiency. The fixed bed studies indicated that the breakthrough time for arsenic(V) removal is dependent on the initial influent arsenic concentrations. These results suggest that arsenate adsorption on SMIOCS media may play an important role for arsenic immmobilization.