Preparation and characterization of polysaccharides/PVA blend nanofibrous membranes prepared by electrospinning

Apresentação efetuada no Smart & Funcional Coatings–European Conference Turin, 26th September 2013A polyvinyl alcohol (PVA) / cyanobacterial EPS blend nanofibrous membranes were fabricated by electrospinning using polyvinylidene fluoride (PVDF) as a basal membrane, in order to obtain thin-layer composite nanofiltration membranes. The production of the nanofibers using EPS and PVA as plasticizer in different ratios was produced in a NF-103 MECC Nanon electrospinning equipment with an applied electric field between 15 and 25 kV and a flow of 0,2 mL/h. Morphological, mechanical, chemical and thermal characterization of the electrospun fibers deposited on the basal membranes, were evaluated by atomic force microscopy (AFM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), dynamical and mechanical analysis (DMA), thermogravimetry (TGA) and differential scanning calorimetry (DSC). The AFM and SEM results show the presence of fibers with dimensions between 54 and 121 nm with low bead formation. In the EDS analysis presence of sulfur elements was observed confirming the inclusion of EPS in the nanofibers. The morphology and diameter of the nanofibers were mainly affected by the concentration of the blend solution and the weight ratio of the blend, respectively. The best PVA/EPS nanofibers were achieved in a ratio of 12 % PVA and 0.4 % EPS. The solution conductivity was ranging 1500 to 3500 μS/cm with a viscosity of about 100 to 500 cP. The DMA results confirmed the miscibility of PVA/EPS blends. The elastic modulus of the nanocomposite mats increased significantly as a consequence of the reinforcing effect of EPS. Thermal and mechanical analysis demonstrated that there were strong intermolecular hydrogen bonds between the molecules EPS-PVA in the blends. The heat-treated electrospun blended membranes showed better tensile mechanical properties when compared with PVA alone, and resisted more against disintegration. Dead-­end filtration of a standard solutionof hexavalent chromium (2mg/mL) prepared using potassium dichromate (K2Cr2O7). Increase in chromium binding capacity of ~5% in PVA/polysaccharide blended membranes