Preparation and Characterization of Polyvinyl Alcohol/Polyhedral Oligosilsesquioxane Hybrid Membrane for Pervaporation Separation of High-Concentration ε-Caprolactam Solution

We used Vinyl-polyhedral oligosilsesquioxane (POSS)as a modified material and polyvinyl alcohol (PVA) to make a hybrid membrane for the pervaporation membrane separation of high-concentration caprolactam solution. The membranes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, contact angle measurement, and swelling test. The PVA/POSS hybrid membrane exhibited unique pervaporation performance due to its hydrophobic cage-type nano-silica particles. We evaluated the permeate flux, separation factor, swelling/diffusion selectivity, and activation energy of the hybrid membrane. Evaluation results showed that POSS in the hybrid membrane hindered the crystallization of PVA. The separation flux greatly improved in the separation process of the high-concentration caprolactam solution. The excellent diffusion selectivity brought by POSS also maintained a high separation factor. When the flux reached 2.13 kg m−2 h−1, an excellent separation factor of 220 was obtained.