Hydration enthalpy of hydrotalcite low-temperature metaphases

Abstract

Enthalpies of hydration of low-temperature hydrotalcite(HT) metaphases have been measured by means of the adiabatic water-vapor absorption calorimeter. The metaphases were characterized by the Mg/Al ratio of 3 : 1 and CO₃²⁻ interlayer group. The hydration heat for HT-B (partially dehydroxylated HT with bidentate bonded CO₃²⁻) is 2-3 times larger than that of HT-D (dehydrated HT), if they are treated at the same dehydration temperature. Large absolute values of hydration heat, namely 398±4 and 508±10Jg⁻¹, were obtained for the HT-B at respective low dehydration temperatures, 70 and 110°C . This may promise the HT-B to be a new prospective heat exchanger usable at relatively low temperatures.