Polyamide-6 based pervaporation membranes for organic-organic separation

In this work the preparation of homogeneous, composite and mixed matrix membranes (MMMs) based on polyamide-6, was described. Morphology of prepared membranes was investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM) techniques as well as X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) methods. According to AFM images, mixed matrix membranes possess higher roughness compared with unfilled membrane. Based on TEM and TGA analysis it was possible to confirm that metal oxide particles are uniformly distributed in the polymeric matrix. Additionally, XRD analysis results showed that PA-6 is in alpha crystal form. Prepared membranes were used to separate methanol from MeOH/MTBE and MeOH/DMC mixtures by pervaporation. The efficiency of separation was described in terms of permeation fluxes, separation factor and pervaporation separation index. It was found that the membranes efficiently remove methanol from the feed. In the case of 50/50 wt.% MeOH/MTBE mixture as a feed, the separation factor (alpha(AB)) was the highest for the PA-6 membrane filled of 10 wt.% ZrO2 and was equal to 48. The normalized flux of methanol for this membrane was equal to 12.4 mu m kg m(-2) h(-1). The separation factor for a composite membrane with a dense selective top-layer on ultrafiltration support was the highest in contact with 20/80 wt.% MeOH/MTBE mixture and was equal to 35. Based on the Hansen's solubility parameter theory and the PV experimental results, it is concluded that methanol has a higher affinity to DMC than to MTBE. It was also found that the presence of water molecules in the MeOH/MTBE feed mixture causes a substantial decline of methanol transport through the PA-6 membrane. (C) 2013 Elsevier B.V. All rights reserved.