Conventional and controlled rate thermal analysis of nesquehonite Mg(HCO3)(OH)•2(H2O)

The understanding of the thermal stability of magnesium carbonates and the relative metastability of hydrous carbonates including hydromagnesite, artinite, nesquehonite, barringtonite and lansfordite is extremely important to the sequestration process for the removal of atmospheric CO(2). The conventional thermal analysis of synthetic nesquehonite proves that dehydration takes place in two steps at 157, 179 degrees C and decarbonation at 416 and 487 degrees C. Controlled rate thermal analysis shows the first dehydration step is isothermal and the second quasi-isothermal at 108 and 145 degrees C. In the CRTA experiment carbon dioxide is evolved at 376 degrees C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of magnesium carbonates such as nesquehonite 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. Constant-rate decomposition processes of non-isothermal nature reveal partial collapse of the nesquehonite structure.