Hydrocalumite and hydrocalumite-type compounds: a special type of layered double hydroxides

An exhaustive bibliographical review of one of the most peculiar Layered Double Hydroxides, LDH, namely hydrocalumite and hydrocalumite-type compounds, has been carried out. The main differences that make hydrocalumite a special and interesting LDH are described, as well as the main methods of synthesis. A comprehensive comparison is also made with respect to MgAl/carbonate hydrotalcite with a Mg/Al molar ratio of 2. Thermal behavior of hydrocalumite is also different than that of other LDH, leading to the formation of attractive Mixed Metallic Oxides, MMO. Thus, the applications of hydrocalumite, hydrocalumite-type compounds and the derived MMO in environmental remediation and heterogeneous catalysis and photocatalysis are presented. Hydrocalumite, contrary to hydrotalcite, is not currently commercialized on an industrial scale, probably because its preparation is more complicated. Considering the excellent properties of hydrocalumite and the price, abundance and biocompatibility of its components, the scaling of its production should be a key challenge to take advantage in its industrial application.