Formation of Mg-Al layered double hydroxides intercalated with nitrilotriacetate anions

Abstract

The formation, by coprecipitation, of a Mg-Al layered double hydroxide (LDH) intercalate containing nitrilotriacetate (NTA) anions has been observed. The intercalated LDH has a basal spacing close to 12 Å (gallery height 7.2 Å). The rehydration of a Mg-Al mixed oxide (formed by calcination at 500 °C of a Mg-Al carbonate-containing LDH) in the presence of NTA also results in the formation of a NTA intercalated LDH, indicating the ability of the mixed oxide for adsorptive removal of NTA. It was further shown that nitrate-containing LDHs may be ion-exchanged by NTA, whereas for carbonate-containing materials exchange is difficult. In some cases the formation of the intercalate is accompanied by considerable sequestration of the magnesium and aluminium cations. It is proposed that NTA may exist in the interlayer of the LDH as a trivalent or a divalent anion or under certain circumstances as a [Mg-NTA] ^– complex.