Anion-Exchange Reactions of Layered Double Hydroxides: Interplay between Coulombic and H-Bonding Interactions

Abstract

The NO 3 − - and Cl − -containing layered double hydroxides (LDHs) of Mg with Al interact weakly with anions in solution under equilibrated conditions and yield a type V isotherm. The uptake of anions under nonequilibrated conditions varies monotonically with the layer charge when the outgoing anion is NO 3 −, whereas it goes through a maximum when the outgoing anion is Cl − . These observations suggest that Coulombic interactions play a dominant role in Cl − -LDHs, whereas weak interactions governing the mode of intercalation of NO 3 − ions influence the exchange reactions of NO 3 − -LDHs. These studies have significant implications for the remediation of insidious anions by LDHs.