$\hbox {NO}_{2}^{-}$ and $\hbox {SCN}^{-}$-intercalated layered double hydroxides: structure and orientation of anions in the interlayer gallery

Abstract

$\hbox {NO}_{2}^{-}$ and $\hbox {SCN}^{-}$ are two common small inorganic anions. The former is a common industrial pollutant. The latter is linear and is a good mimic for the toxic $\hbox {CN}^{-}$ ion. The structures of these two anions are refined within the gallery of the [Zn–Al]-layered double hydroxide (LDH). Both LDHs crystallize as mixed anion phases. The nitrite is found to co-exist with the nitrate ion. The nitrite ion is intercalated with its molecular plane inclined to the metal hydroxide layer. In the case of the $\hbox {SCN}^{-}$ intercalated LDH, no other anion was detected by ion chromatography, suggesting that the $\hbox {SCN}^{-}$ deficiency is compensated by intercalated hydroxyl ions. In this case, the $\hbox {SCN}^{-}$ ion is found to be intercalated with its molecular axis inclined to the metal hydroxide layer.