INQUIMAE   12526
INSTITUTO DE QUIMICA, FISICA DE LOS MATERIALES, MEDIOAMBIENTE Y ENERGIA
Unidad Ejecutora - UE
artículos
Título:
Complexation at the edges of hydrotalcite: The cases of arsenate and chromate.
Autor/es:
M. JOBBÁGY; A.E. REGAZZONI
Revista:
JOURNAL OF COLLOID AND INTERFACE SCIENCE
Editorial:
ACADEMIC PRESS INC ELSEVIER SCIENCE
Referencias:
Lugar: Amsterdam; Año: 2013 vol. 393 p. 314 - 318
ISSN:
0021-9797
Resumen:
Sorption of CrO42- and HAsO42-
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 CrO42- equals the ion-exchange capacity of the solid, whereas sorption of HAsO42- saturates at a higher value. Chloride ions inhibit the uptake of both anions, the amount of sorbed CrO42- declining rapidly to zero. The uptake of HAsO42-,
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. CrO42- and HAsO42-
have notable, albeit different, effects on the electrophoretic behavior
of hydrotalcite; the positive particle charge is screened almost
completely by CrO42-, whereas sorption of HAsO42-
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.