Decomposition kinetics study of AlOOH coated calcium carbonate

AlOOH coated calcium carbonate was synthesized by a two-step chemical solution reaction. The phase and microstructure analysis were carried out by X-ray diffraction and scanning electron microscopy. Non-isothermal decomposition kinetics of the AlOOH coated calcium carbonate has been investigated on the basis of the TG-DTA analysis. The model-free and model fitting approaches were applied to the data for non-isothermal decomposition kinetics of AlOOH surface-coated calcium carbonate as well as the reference. Master-plot method was used to determine the decomposition mechanisms based on the kinetic parameter Ea achieved by model-free Kissinger equation. The reference sample decomposed according to the contracting area mechanism R2 and the AlOOH surface-coated calcium carbonate decomposed according to one-dimensional mechanism D1. The kinetic parameters Ea verified by both integral method and differential method showed about 90 kJ mol−1 increase in the decomposition process after being coated. This is possibly due to the as-shell structure of surface AlOOH, which hinders the diffusion of the dissociated CO2 into the outer atmosphere.