Study on Formation Kinetics and Mechanism of Barium-Calcium Phosphoaluminate Mineral

Barium-calcium phosphoaluminate ((C,B)8A6P) mineral was synthesized by introducing Ba2+ into the lattice of calcium phosphoaluminate (C8A6P) mineral and it owned the better hydration activity than C8A6P. In this study, the formation kinetics and mechanism of (C,B)8A6P mineral was firstly systematically explored. The experimental results indicated that calcination temperature had a significant effect on the formation of (C,B)8A6P mineral. The conversion rate of (C,B)8A6P mineral was less than 0.5 and reaction rate was less than 9.4 × 10-7 with the holding time of 8 h at 1500-1530 °C. Nevertheless, the conversion rate and reaction rate reached 0.8 and 9.4 × 10-7, respectively, with the holding time of only 2 h when the calcination temperature ranged from 1540 °C to 1560 °C. In addition, the Jander equation was feasible for the formation of (C,B)8A6P with activation energy of 1310 kJ ∙ mol-1 at 1500-1530 °C, while the Ginstling equation was feasible for use with activation energy of 324 kJ ∙ mol-1 when the calcination temperature ranged from 1540 to 1560 °C.