Sorption isotherms and isosteric energy of Manihot esculenta leaves

This work presents the study sorption isotherms of Manihot esculenta leaves. Desorption-adsorption isotherms were determined by using static gravimetric method at 30, 40 and 50°C for water activity ranging from 0.10 to 0.90. Results obtained show that at high water activities, adsorption of water increased with increasing temperature and isotherm curves of adsorption and desorption did not follow the same lend: the hysteresis cycle. The sorption isotherms of M. esculenta leaves are of type II. Five different models were used to study these experimental curves and GAB’S model best describes these sorption isotherms (MRE 10% and R² 0.996). The sorption heat of the monolayer HM was 3.073 kJ.mole^-1 while that for the multilayer was 0.970 kJ.mole-1. For M. esculenta isosteric leaves heat of sorption varies from 32.15 to 3.54 kJ.mole^-1 and the values of q0 and X0 for desorption were respectively 71.43 kJ.mole^-1 and 7.643 g water/g (d.b).