CETMIC   05378
CENTRO DE TECNOLOGIA DE RECURSOS MINERALES Y CERAMICA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Adsorption of Cadmium, Chromium and Lead cations on northpatagonic clay minerals
Autor/es:
G. M. SILVA; S. G. ACEBAL; R. M. TORRES SÁNCHEZ
Lugar:
Dresden
Reunión:
Conferencia; MECC14 7th MID-EUROPEAN CLAY CONFERENCE; 2014
Resumen:
Some physicochemical properties related to the adsorption behavior of a bentonite (CATAE) and two common clay minerals (named DTN2 and DTN3) from Cinco Saltos (North-Patagonia, Argentina) were characterized. Cation exchange capacity, exchangeable cations, specific surface area, surface charge density, permanent and pH-dependent charges, point of zero charge, isoelectric point and the elemental composition were determined. Sorption and desorption experiments using Cd2+, Cr3+ and Pb2+ solutions were carried out. To assess the monometal and multicationic adsorptions, batch equilibrium experiments using raw and purified materials, in aqueous solution at 298 K, pH=3.5 and at different ionic strengths were performed. Desorption processes by simple and successive extractions, with solutions of HCl and HNO3 (0.1%) were performed. In all cases, the quantification of the metal ion remaining in solution was determined by atomic emission spectrometry (ICP-AES). CATAE adsorbed significantly higher amounts of metal ionic species than common clays for equal sorption time. The adsorption of each metal ion was greater when the clay minerals were free of accompanying impurities. The retention rates were: 100% for Cr and Pb ionic species and 96% for Cd ionic species when CATAE is free of oxides and oxohydroxides of Fe and CO3 =. The affinities sequence for monometal adsorption was Cr3+>Cd2+>Pb2+. Although the adsorption process was slower when ions compete for the same active sites the sequence remained when the multicationic solution was tested. HNO3 (0.1%) soluction was more effective than HCl (0.1%) solution in the removal of most metal ions. For common clays the differences between the two acid solutions were not significant, although it should be noted that metal ions were more readily desorbed from common clays than CATAE. The desorption process changed when an inert electrolyte was added to the multicationic solution. Thus, for a solution containing 0.1 M KNO3 both acid solutions removed 100% of Cd2+, but only 2% of retained Cr3+ was desorbed, while for Pb2+ the percentage desorbed was 78%. Two surface adsorption mechanisms were dominant, formation of outer-sphere complexes on basal surfaces and internal sphere complexes on edge sites. CATAE showed high effectiveness in removing Cd, Cr and Pb ions from aqueous solutions.