Effect of polymer composition in PEEKWC/PVP blends on pervaporation separation of ethanol/cyclohexane mixture

Abstract

Modified poly(ether ether ketone) (PEEKWC) membranes with different poly(vinyl pyrrolidone) (PVP) content were used to separate ethanol/cyclohexane (EtOH/CHx) azeotropic mixture in a pervaporation lab scale apparatus. Eight blends were prepared with the PVP weight percent up to 24%. Several characterization tests were carried out to investigate mechanical, morphological and operational properties of the membranes. These tests include FTIR-ATR, tensile strength, and water contact angle measurements. Furthermore, swelling and pervaporation tests are reported. All the membranes were EtOH selective. The highest separation factor was observed at 21 wt% of PVP. Permeation total flux was continuously increased from 3.75 × 10 −3 to 14.81 × 10 −3 kg/m 2 h as the PVP content increased from 0 to 24 wt%. The structure of the blends changed to a more porous form at higher PVP percents as shown in the SEM images, resulting in higher fluxes. Furthermore, it increased the tendency of EtOH uptake which caused the separation factor to increase simultaneously. Swelling results at different concentrations confirmed the same affinity to EtOH with respect to the PVP amount. As the result of the mechanical tests, Young's modulus and maximum stress values decreased in the contrary of elongation of the membranes at higher PVP contents and EtOH concentrations. Since EtOH molecules compared to CHx molecules have higher interactions with the polymer chains, the mechanical strength of the membranes is expected to decline at higher EtOH concentrations, particularly at higher PVP amounts.