Kinetics, thermodynamics, and mass transfer mechanism of the ultrasound-assisted extraction of bioactive molecules from Moringa oleifera leaves

Abstract

Phenolic antioxidants were extracted from Moringa oleifera leaves by applying ultrasound-assisted extraction (UAE). The feasibility of UAE was studied by analyzing the kinetics, thermodynamics, mass transfer, and effective diffusivity mechanisms to improve the process under several temperature values (298, 300, 306 K). Extraction rate increased with temperature (0.0028, 0.0028, and 0.0029 L mg(-1) min(-1)). Activation energy for the process of UAE was calculated to be 3.5225 kj mol(-1). Based on the results of thermodynamics parameters, UAE process of phenolic extraction from Moringa oleifera leaves was endothermic, random, and spontaneous, where the change in enthalpy, entropy, and Gibbs free energy were 1.6156 kj mol(-1), 0.02977 kj mol(-1) K-1, and - 7.2356, - 7.3247, - 7.4732 kj.mol(-1), respectively. Furthermore, the diffusion and mass transfer model were used in order to evaluate the diffusion coefficients, mass transfer coefficients, and Biot numbers of the process. Diffusion coefficients (1.9800 x 10(-10), 2.3070 x 10(-10), and 2.3905 x 10(-10) m(2) s(-1)) and mass transfer coefficients (0.1320, 0.1447, and 0.1460 m s(-1)) increased with increasing temperature, while Biot numbers (285.00 x 10(3), 268.05 x 10(3), and 261.22 x 10(3)) decreased slightly with increasing temperature. In addition, Biot number indicated that the external resistance is negligible.