Tailoring the Hydrophilicity of Electrospun Membranes for Water Filtration

Saline water provides an alternative source to freshwater, which is becoming scarcer as supply dwindles and demand increases due to industrialization and an increased global population. Desalination membranes, particularly those in reverse osmosis, are susceptible to fouling and scaling, which increases monetary cost through energy, maintenance, and membrane replacement. Pretreatment membranes are used to reduce the concentration of foulants and scaling precursors in saline water, improving membrane lifetime and water flow through the RO membranes while reducing operation costs. Key design parameters for these pretreatment membranes are high fluxes and removal of fouling/scaling components. Electrospinning polymer membranes is an easily scalable process that produces non-woven, micron-to-nanometer scale fibrous membranes with tunable pore sizes (related to flux) and a high surface area for interacting with feed streams. A large body of literature precedents has demonstrated that increasing the hydrophilicity of polymer membranes reduces the propensity of fouling. Therefore, this project examines the combination of hydrophobic poly(vinyl chloride) (PVC) with hydrophilic polymer poly(vinyl alcohol) (PVA) to form porous, electrospun membranes with tailored hydrophilicity. PVA was chosen because it is highly hydrophilic, but displays a limited solubility in water under normal process conditions (e.g., <60 Ë?C). Polymer solutions of PVC/THF and PVA/water were characterized by solution rheology, and electrospun fibrous mats were prepared using side-by-side and layered electrospinning techniques. The fibers were analyzed using scanning electron microscopy (SEM) in order to determine their pore size and fiber diameter. Finally, the relative hydrophilicity was tested via water contact angle measurements. Our results indicate that the fiber diameters of both the PVA and PVC fibers are correlated to the solution concentration and viscosity, which has a subsequent impact on the membrane porosity. Additional experimental factors such as voltage, flow rate, and tip to collector distance have been used to tailor the fiber diameter and porosity.