Influence of the Al-for-Fe substitution in the adsorption of As(V) onto goethites-morphological surface characterization

A.E.TUFO; MARIA CLAUDIA MARCHI; S.M.LANDI; M. DOS SANTOS AFONSO; E.E.SILEO

Buenos Aires

Congreso; 5th International Congress on Arsenic in the Environmen; 2014

International Society of Groundwater for Sustainable Development

Arsenic derived from natural and anthropogenic sources occurs in groundwater, and its mobility is influenced by the presence of goethite and ferrihydrite, that present a great affinity for As(V). As the substitution of Al for Fe in goethites is well documented, in this work we explore the adsorption of As(V) onto pure and Al-substituted goethites. We have obtained the adsorption isotherm ([As]adsorbed vs. [As]solution) and we found an uncommon bell shaped curve with a maximum at 0.25 mmolL-1, after this value the adsorption decreased. In order to explore the possible formation of FeAsO4 as a surface precipitate at [As]>0.25 mmolL-1, we have obtained STEM micrographs of the As-adsorbed Al-goethites. The micrographs indicated that no surface precipitates were formed. Based in this results and PZC measurements we postulate that the decline in adsorption is provoked by the formation of bidentated complexes that decrease the adsorption efficiency by coordinating to two metal sites.