Adsorption of Aqueous Selenite [Se(IV)] Species on Synthetic Layered Double Hydroxide Materials

Layered double hydroxide materials (Zn/Al, Mg/Al, Zn/Fe) with varying composition (M(2+):M(3+) molar ratio, x = 3, 2, 1, and 0.33) were synthesized and evaluated for their selenium adsorption characteristics in aqueous medium. Zn/Al and Mg/Al LDHs with x = 3 and 2, exhibited very high selenite adsorption capacity. XRD patterns of the pristine LDHs, LDH after selenite adsorption, and chloride ion leaching studies revealed that adsorption of selenium on the LDHs occurred through both surface adsorption and ion-exchange mechanism. The adsorption data was fitted to Langmuir and Freundlich isotherm models. A pseudo second-order kinetic model was used to describe the adsorption kinetics of selenite on LDH materials. Desorption of selenite ions in water from the LDH-Se matrix was Studied up to 5 h.