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

ANA E. TUFO; M. C. MARCHI; S. M. LANDI; MARIA DOS SANTOS AFONSO; ELSA E. SILEO

Buenos Aires

Congreso; 5th International Congress on Arsenic in the Enviroment As 2014; 2014

University of Southern Queensland and International Groundwater Arsenic Research Group

Influence of the Al-for-Fe substitution in the adsorption of As(V) onto goethites. Morphological surface characterization/ Influencia de la sustitución Al-por-Fe en goetitas sobre la adsorción de As(V). Caracterización morfológica superficial A.E. Tufoa, M. C. Marchia,b, S. M. Landic, M. dos Santos Afonsoa and E.E. Sileoa a- INQUIMAE. Pabellón II, 3º piso, FCEN. UBA. Ciudad Universitaria. Bs. As. Argentina; b-Centro de Microscopías Avanzadas. FCEN. UBA. Ciudad Universitaria. Bs. As. Argentina;c- Instituto Nacional de Metrologia, Qualidade e Tecnologia, Divisão de Metrologia de Materiais, RJ, Brasil anatufo@qi.fcen.uba.ar Arsenic derived from natural and anthropogenic sources occurs in groundwater, and its mobility is highly influenced by goethite and ferrihydrite. As the substitution of Al-for-Fe in natural goethites is well documented, our aim was explore the adsorption of As(V) onto several Al-substituted goethites, and analyze by STEM micrographs the possible formation of FeAsO4 as a surface precipitate that blocks ulterior sorption. Adsorption isotherms ([As]adsorbed vs. [As]solution) of all samples were obtained, and an uncommon bell shaped curve with a maximum at 0.25 mmolL-1 was found for all goethites. The STEM micrographs of the As-adsorbed Al-goethites were obtained at [As]>0.25 mmolL-1 confirmed that no surface precipitates were formed. Based in these results the formation of bidentated complexes were proposed to explain the decrease of the adsorption by As(V) coordination to two metal sites.