Modeling of the Mass Transfer Effect in Biphasic Enzyme Membrane Reactor for Hydrolysis of Olive Oil

Abstract

This article presents a model to explain the mass transfer phenomenon of the ions (OH-, Na+ and RCOO-) formed during the hydrolysis reaction on the aqueous side of the reaction sites in the biphasic enzyme membrane reactor (EMR) using lipase immobilized on modified poly (methyl methacrylate-ethylene glycol dimethacrylate) (PMMA-EGDM) clay composite membrane. Our model divides the aqueous side of the system into two regions, an unstirred film (aqueous side) adjacent to the pore end (region I) and charged capillaries of the membrane (region II). The process involves transport of Na+, OH- and RCOO- ions in region I whereas the film is considered as an electro-neutral region. Space charge model (consisting of Nernst-Planck equation for ion transport and nonlinear Poisson-Boltzmann (PB) equation for charge distribution) is used to describe transport of ions inside charged capillaries (pores) in region II. The solution of the nonlinear PB equation is computationally intensive and to overcome this difficulty, a series solution of the PB equation for the charge distribution inside the capillaries is developed. The suggested solution is used to determine the rate of formation of oleic acid using the information on pore size of the membrane (determined from molecular weight cut-off experiment) and diffusivity data from the literature. The result shows that the concentration of RCOO- ions at the boundary of region I of the aqueous phase increases with increasing the duration of reaction. The pore wall charge determined using the model is found to be in the range of 0.715-0.735 mV.