Complexation at the edges of hydrotalcite: the cases of arsenate and chromate

• Autores: Jobbagy, Matias; Regazzoni, Alberto Ernesto
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Layered Double Hydroxides; Chromate; Surface Complexation; Arsenate
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Sorption of CrO2 4 and HAsO2 4 by hydrotalcite, in its chloride form, was studied as a function of anion concentration. In both cases, the shape of the isotherms is langmuirian. The maximum uptake of CrO2 4 equals the ion-exchange capacity of the solid, whereas sorption of HAsO2 4 saturates at a higher value. Chloride ions inhibit the uptake of both anions, the amount of sorbed CrO2 4 declining rapidly to zero. The uptake of HAsO2 4 , however, attains a constant value at high chloride concentrations. The excess of arsenate uptake follows, at constant pH, a langmuirian dependence with equilibrium concentration and decreases with increasing pH, depicting a marked change in slope at pH pQa3. CrO2 4 and HAsO2 4 have notable, albeit different, effects on the electrophoretic behavior of hydrotalcite; the positive particle charge is screened almost completely by CrO2 4 , whereas sorption of HAsO2 4 produces charge reversal. These results reflect the formation of inner-sphere arsenate surface complexes at the edges of hydrotalcite particles. The underlying rationale is discussed in terms of the crystal structure of hydrotalcite surfaces.
Fil: Jobbagy, Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina
Fil: Regazzoni, Alberto Ernesto. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes; Argentina. Universidad Nacional de San Martín. Instituto Sabato; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina