Transport model for the adsorption of oxyanions of selenium (IV) and arsenic (V) from water onto lanthanum- and aluminum-based oxides

A model for the adsorption of oxyanions of selenium (IV) and arsenic (V) as a function of time and pH was developed and tested on LA(T) (10% lanthanum oxide/90% activated gamma-alumina mixed-oxide), lanthanum oxide, activated gamma-alumina, and activated alpha-alumina. A good correlation between the transport model and experimental results were observed. The model showed strong evidence that the adsorption of oxyanions of selenium and arsenic at the oxide-water interface is governed by three gradients: concentration, potential, and ionic size. Lanthanum oxide was observed to be a better adsorbent for selenium than activated gamma-alumina and alpha-alumina. At the same initial selenium concentration, gamma-alumina was a better adsorbent for selenium as compared to alpha-alumina. (C) 1997 Academic Press.