Industrial & Engineering Chemistry Research, Vol.44, No.18, 7057-7061, 2005
Non-isothermal dehydration kinetics of ceftriaxone disodium hemiheptahydrate
The non-isothermal dehydration behavior of ceftriaxone disodium (CTXN) hemiheptahydrate, investigated by thermogravimetry-derivative thermogravimetry (TG-DTG), proceeds in two steps: (1) the loss of two and one-half water molecules and (2) the loss of one water molecule. The dehydration kinetics were achieved from the TG-DTG curves by both the Achar method and the Coats-Redfern method with 21 frequently cited basic kinetic models. The dynamic dehydration processes for steps 1 and 2 are best expressed by the Zhuralev-Lesokin-Tempelman equation and the Avrami-Erofeyev equation (n = 1), suggesting a three-dimensional diffusion-controlled mechanism and a nucleation-controlled mechanism, respectively. The corresponding kinetic compensation effects (KCEs) for the two steps are found to be: In A = 0.354 54 x 10(-6.5733) and ln A = 0.297 66 x 10(-5.47166), respectively.