Modeling the additive effects of Pb(II) and Cu(II) on the competitive attenuation of As(V) through solid precipitation versus adsorption to goethite

Resumen

Mine-related activities
cause widespread contamination of aqueous environments with high
concentrations of arsenic and accompanying heavy metals. The natural
attenuation of As(V) in soils and groundwater under oxic conditions
occurs mainly through sorption processes to iron and aluminum
(hydr)oxides; as well as through the formation of highly insoluble
heavy metal(II) arsenates. In the present investigation we used
thermodynamic modeling to predict the environmental geochemical
behavior of As(V) in the presence of Pb(II), Cu(II) and goethite, in
an effort to approach the complexity of multi-component real
contaminated scenarios. The key to this modeling was the coupling of
a highly robust Surface Complexation Model of As(V) adsorption to
goethite, which uses combined tenets of the Triple-Layer and
CD-MUSIC models, together with appropriate metal(II) arsenate solid
formation constants as well as those of all chemical equilibria
taking place in the aqueous phase. Mixed-metal arsenates were
predicted to form and increase the predominance region of the
precipitation reactions for a highly surface-reactive goethite, at
the expense of the adsorption mechanism, but the model yielded no
aqueous As(V) released at any condition investigated.