AS(V) ADSORPTION ON AMORPHOUS IRON-OXIDE - TRIPLE LAYER MODELING

The adsorption of As(V) by amorphous iron oxide was investigated at 25-degrees-C, 0.01 M NaNO3 background electrolyte as a function of solution pH(4-10) at three initial As(V) concentrations and two Fe(III) concentrations. As(V) adsorption increased with decreasing pH. A modified Langmuir isotherm has been used for describing an equilibrium partition existing between solid and liquid phases. The triple-layer model was used for simulating As(V) adsorption on iron oxide surface. This model was able to describe As(V) adsorption over the pH range 4-10, all at the concentrations of As(V) and Fe(III) studied. =Fe(H2AsO4)0, = Fe(HAsO4)- and = Fe(AsO4)2- have been shown through simulation with inner-sphere complexation products to be more consistent with experimental adsorption observations than complexation with other surface species.