Separation of Isomeric Xylenes Using Cyclodextrin-Modified Ceramic Membranes

Abstract

Cyclodextrin (CD)-modified ceramic membranes for the separation of xylene mixtures were investigated. CDs were directly immobilized to the surface of TiO2/Al2O3 ceramic nanofiltration membranes, and a cross-linking agent was used to obtain further stabilization of the CD layer. Pervaporation tests showed that the order of permeation from ternary xylene mixtures was m-xylene > o-xylene > p-xylene. In p-xylene/m-xylene binary mixtures, the separation was a strong function of the feed concentration ratio. The selectivity of p-xylene over m-xylene changed from 1.53 at 4 vol % to 0.72 at 32 vol % of p-xylene in the feed. To describe these observations, a mathematical model was derived based on Stefan−Maxwell theory assuming a surface-diffusion mechanism. Model parameters including sorption isotherms were obtained from experiments. The Stefan−Maxwell diffusion coefficients are obtained from molecular dynamics simulations. Finally, this model predicted the experimental observations well and revealed that the sel...