Development and Characterization of PVDF/PVP/PAA Composites Membranes for Photocatalytic Reactions

The development of catalytic materials has been well studied to promote degradation reactions in treatment of water and wastewater. Particle size diminishing to nanoscale aims to improve reactivity and increase functionality. In the heterogeneous Fenton process, the use of nano zerovalent iron (nZVI) as catalysts has shown effective gains in increasing reactivity. However, due to difficulty of using nanoparticles in solution, its incorporation in polymer matrices have been investigated. In addition, nanofiltration membranes and reverse osmosis are well known as good at rejecting contaminants with low molecular weight and because of this have a fouling facilitated, which can diminish permeate flux and modify the membrane surface, that could augment mass transport through membrane pores. Thus, this work proposes the development of photocatalytic polymer membranes with nZVI to promote photo-Fenton’s reaction onto membrane. Several conditions of PVDF flat-sheet membranes preparation were tested by phase inversion method with immersion precipitation in order to obtain high porosity and hydrophilicity. Parameters that were considered: additive type (propionic acid and polyvinyl pyrrolidone - PVP); additive concentration (5 to 7.5%); PVDF concentration (14 and 17%); exposure time to air (immediate to 30 minutes); and coagulation bath (20 to 100% water). Functionalization with PAA was investigated in order to vary the concentrations of acrylic acid (43 to 20%), initiator (0.5 to 1.4%) and ethylene glycol (1.0 to 4.6%) in the polymerization/crosslinking solution, as well as the membrane exposure time in the solution (5 to 20 min) and presence of stirring. The membranes were characterized by SEM, FTIR-ATR, contact angle, iron loss and water permeability. The impregnation of nZVI was efficiently achieved which provided a small loss of iron (0.005 mg/L) after 3 hours of water permeation. High permeability and porosity hydrophilic PVDF membranes were achieved with 14 % PVDF, 7.5% PVP, 7 minutes of exposure to air and 70/30 : Water/NMP coagulation bath. Tests on the synthesized membranes with UV light are being conducted in order to outline the maximum UV dose that won’t affect the membrane structure and morphology.