Vacuum drying of the Terbinafine HCl powder: A kinetics study and mathematical modeling

Abstract In this paper, Terbinafine HCl antifungal powder is dried by vacuum dryer. A further analysis of the dried product by HPLC is compulsory to guarantee its compliance with quality requirements. Twelve drying kinetics are obtained, adjusted by 40 mathematical models, and the effective diffusivity coefficients Deff and activation energies Ea are calculated by two approaches, the classical linearization of Fick's second equation of diffusion and Arrhenius equation, and by dragonfly swarm optimization method DA-nlinfit. The second approach delivered predictions 3 times closer to actual measured residual moisture ratio MR. Accordingly, precise estimations are conveyed by the method in terms of Deff varying from (1.41 × 10–9 to 7.22 × 10–9) m2/s, Ea projected between (33.37 and 35.64) kJ/mol, and subsequently more accurate enthalpies ΔH∈ (30.52;33.03)kJ/mol, entropies ΔS∈(−0.31;-0.29)kJ/K.mol and Gibbs free energies ΔG∈(136.77;126.58) kJ/mol. The qualitative analysis of the dry powder gives a better quality in the range [40 60] °C, but above this, the results are not satisfactory.