Dynamic and controlled rate thermal analysis of hydrozincite and smithsonite

The understanding of the thermal stability of zinc carbonates and the relative stability of hydrous carbonates including hydrozincite and hydromagnesite is extremely important to the sequestration process for the removal of atmospheric CO2. The hydration-carbonation or hydration-and-carbonation reaction path in the ZnO-CO2-H2O system at ambient temperature and atmospheric CO2 is of environmental significance from the standpoint of carbon balance and the removal of green house gases from the atmosphere. The dynamic thermal analysis of hydrozincite shows a 22.1% mass loss at 247 degrees C. The controlled rate thermal analysis (CRTA) pattern of hydrozincite shows dehydration at 38 degrees C, some dehydroxylation at 170 degrees C and dehydroxylation and decarbonation in a long isothermal step at 190 degrees C. The CRTA pattern of smithsonite shows a long isothermal decomposition with loss of CO2 at 226 degrees C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of zinc carbonate minerals via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. The CRTA technology offers a mechanism for the study of the thermal decomposition and relative stability of minerals such as hydrozincite and smithsonite.