Development of a mass transport model for predicting pervaporative performance of benzene /cyclohexane mixture through Polyurethane membranes

Separation of organic mixtures by membrane based Pervaporation process using dense polymeric membranes is usually analyzed in terms of the solution-diffusion model which assumes that a permeating component is first dissolved in the membrane and then diffuses through the membrane due to its driving force. Therefore the separate evaluation of sorption and diffusion phenomena is necessary to determine the controlling step in overall mass transport in the membrane. In this article, the pervaporative separation of benzene from its mixture with cyclohexane by polyurethane membranes was studied over the entire concentration range 0-100% benzene at 25 C o through a rigorous modeling. The validity of the proposed model was examined by the experimental data available in the literature. The sorption of components into the polyurethane was modeled using classical Flory-Huggins thermodynamic model. The binary (polymer-component and component-component) interaction parameters were calculated using pure component uptake data. Using these parameters, the multicomponent sorption performance was then predicted by the extended Flory-Huggins model. Diffusion step was modeled by Maxwell-Stefan formulation using concentration dependent diffusion coefficients. The results reveal a close agreement between the experimental data and the predicted sorption and permeation values. The results also indicated the aromatic compounds are preferentially sorbed into polyurethane over the entire rage of composition.

Keywords:

Pervaportion , solution-diffusion , Flory-Huggins model , Benzene , Cyclohexane , Stefan- Maxwell model