Thermal analysis and decomposition kinetics of the dehydration of copper sulfate pentahydrate

The thermal decomposition kinetics of individual stages of copper sulfate pentahydrate (CuSO4·5H2O) was investigated by TG–DSC, and the kinetic parameters were calculated by Ozawa method and multivariate nonlinear regression.It is found that CuSO4·5H2O decomposes to CuSO4 in two stages, three steps. The first and the second steps are continuous processes of dehydration reaction; the temperature range of the two steps is from 50 to 150 °C. The first step lost two water molecules which rely on the copper ion as center by coordinate bonds, activation energy of the reaction is 71.26 kJ mol−1, the pre-exponential factor logA is 8.40, and reaction order is 0.09. The second step lost other two water molecules which are not only relying on combination of coordination bonds, but also on hydrogen bonding. Activation energy of the reaction is 112.12 kJ mol−1, the pre-exponential factor is 13.23, and reaction order is 0.18. The third step lost the fifth water molecule which forms hydrogen bonds and is based on sulfate ion binding, activation energy is 165.23 kJ mol−1, the pre-exponential factor is 15.09, and reaction order is 0.90. Reaction mechanism of the above three steps is Fn (n-order reaction).