Dehydration characteristics of struvite-K pertaining to magnesium potassium phosphate cement system in non-isothermal condition

Struvite-K (KMgPO4 center dot 6H(2)O) is the main hydration product of magnesium potassium phosphate cement. Its thermal stability is critical to the properties of magnesium potassium phosphate cement. Therefore, in this study, the dehydration behavior of struvite-K was investigated at N-2 atmosphere in non-isothermal condition. The process was conducted and controlled in a simultaneous TG/DTA analyzer, at heating rates of 2, 5, 10, 15, and 20 K min(-1). The residual mass was always around 58.5% of the initial one, regardless of the heating rate, which corresponds to the dehydration reaction through one step, KMgPO4 center dot 6H(2)O -> KMgPO4. The activation energy (E (a)) corresponding to the dehydration of struvite-K was evaluated by non-isothermal kinetic analysis based on the application of isoconversional methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods). The calculated results show that Flynn-Wall-Ozawa has slightly higher values of activation energy (E (a)) and correlation coefficients (R (2)). Both methods have been proved to be suitable for analyzing dehydration behavior of struvite-K.