Thermal decomposition mechanisms for cobaltoblodite Na2Co(SO4)(2)4H(2)O and cupper-krohnkite Na2Cu(SO4)(2)2H(2)O have been developed using constant rate thermal analysis technique under controlled residual water vapor pressure above the sample PH2O=hPa. The apparent activation energy of each dehydration process was measured by means of two CRTA curves without any presumption to the kinetic low. Correlation between structure and thermal behavior was highlighted. It has shown that dehydration of cobaltoblodite mineral occurs in two steps with formation of Na2Co(SO4)(2)1.5H(2)O and Na2Co(SO4)(2) as intermediate and final phases, respectively. The activation energies of both dehydration steps are 167kJmol(-1) and 107kJmol(-1), respectively. For cupper-krohnkite mineral, its dehydration occurs in one step leading to Na2Cu(SO4)(2). The corresponding activation energy was found equal to 71kJmol(-1).
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