Dehydration of caprolactam-water mixtures by composite membranes with nano silica/polyacrylate active layer by emulsion polymerization

A pervaporation separation active layer by emulsion polymerization was prepared by using acrylate monomer and nano silica sol solution. Porous polyacrylonitrile substrate was used to construct composite pervaporation membranes. We used CPL/water mixture system (caprolactam (CPL)) to analyze the pervaporation separation performance of composite membranes, and studied the morphology and properties of the membranes by scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis, X-ray diffraction, and contact angle. Given the formation of composite structures, the thermal stability of the nano silica/polyacrylate composite membrane is enhanced. A pervaporation transport equation was introduced to the permeation flux of normalized emulsion polymerization composite membranes. This equation relates to water permeability, CPL permeability, and membrane selectivity to assess pervaporation performance and potential mechanisms. The results show that the maximum total permeate flux of the CPL/water system reaches 1,138 g/(m(2)h) with a separation factor of 353, which was remarkable compared with previous research. Membrane materials obtained by emulsion polymerization can be introduced to the field of pervaporation, providing a novel way to obtain excellent pervaporation membrane materials.