Studies on the pervaporation membrane of permeation water from methanol/water mixture

This investigation was performed to find if the nanometer SiO₂ added in the membranes can improve the pervaperation performance of the membranes. Acrylic acid (AA) and acrylonitrile (AN) were synthesized by solution polymerization with and without nanometer SiO₂. The copolymer solution was made into main body of the membranes, then composited with the polyvinyl alcohol (PVA) acetal membranes, to make the three-layer sandwich composite pervaporation membranes. The structure and the performance of the membranes were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG), dynamic themomechanical analysis apparatus (DMA) and mechanical property testing. Pervaporation experiments were carried out using these membranes to separate the mixtures of methanol/water over the complete concentration range 70–98%, and results showed that the selectivity of the membranes with nanometer SiO₂ had notable improvement. For the 98% mixture at 60 °C, the separate factor is up to 1458, which is improved more than 10 times compared to the membranes without nanometer SiO₂, the permeate flux is up to 325 g/(m² h). For the 70% mixture at 70 °C, the separate factor arrived at 12, the permeate flux is up to 7097 g/(m² h), which is improved more than 14 times compared to membranes without nanometer SiO₂. It was concluded that the pervaperation performance of the membranes can improve greatly by nanometer SiO₂.