Separation of vitamin E from palm fatty acid distillate using silica. III. Batch desorption study

Batch desorption experiments of vitamin E from silica were carried out to study the effects of reaction temperature and agitation rate on the kinetics and equilibrium of desorption. For all systems, it was found that vitamin E desorbed rapidly in the early stages, followed by a much slower release. The two distinct desorption rates might be due to the heterogeneities of the adsorbing surfaces. A first-order two-component four-parameter model described the desorption kinetics well with a coefficient of determination, R² of >0.97. The rate constants for rapid (k_rap) and slow (k _slow) desorption ranging from 0.51 to 2.23 min^-1 and from 0.01 to 0.14 min^-1, respectively, depending on reaction temperature and agitation rate. It was found that the k_rap value increased with increase in reaction temperature, indicating that desorption of vitamin E from silica was endothermic in nature. The desorption rate also increased with increase in agitation rate. Activation energies for the rapid and slow desorption were 38.64 and 73.08 kJmol^-1, respectively. It was found that the desorption isotherm can be fitted by the Fruendlich model. Percentage recovery of vitamin E from silica ranged from 70.36% to 98.74%, depending on the experimental variables. The results from this study provided useful information for achieving high recovery of vitamin E during its separation using an adsorption method.