Adsorption of selenium on hydrous alumina

Adsorption of selenite (SeO 32−) and selenate (SeO 42−) on hydrous alumina (γ‐Al2O3) was studied using batch equilibrium experiments. pH, the single most significant parameter, affected both speciations of selenium (Se) and of surface hydroxo groups on alumina that, in turn, determined the extent of adsorption of the oxyanions. Adsorption of both anions could be described satisfactorily by the Triple Layer Model (TLM). In the presence of SO 42−, Se (VI) adsorption decreased significantly. Fixed bed adsorbers of alumina with an empty bed contact time (EBCT) of 2 minutes or longer provided excellent removal of Se(IV) from dilute aqueous solutions in the pH range of 5 to 8 for a long period. Spent alumina beds were successfully regenerated with 0.25 percent NaOH solution followed by rinsing with deionized water and 0.05 M HCl. While two percent of alumina was lost per cycle on an average, the loss in adsorption capacity of regenerated alumina was insignificant.