(485d) Free Surface Electrospun Polyvinylidene Fluoride Membranes for Direct Contact Membrane Distillation

Water scarcity is a problem that affects 2.7 billion people around the world. By the year 2025, water scarcity is expected to affect nearly 2/3 of the worldâ??s population, particularly in regions that do not have the economic stability to provide solutions to this problem. The use of current technologies such as reverse osmosis, multistage flash distillation, electrodialysis reversal and membrane distillation are commonly used methods of water purification. In this study, the use of direct contact membrane distillation (DCMD) has been chosen due to its low operating costs in comparison to processes such as reverse osmosis which operates at high pressures. The current process for manufacturing DCMD membranes is considered to be expensive, inefficient, and does not allow for the optimization of desirable membrane properties. Through this research an alternative method of fabricating membranes has been studied through the means of free surface electrospinning. This process allows for controllability of desirable properties such as fiber diameter (shown to be related to pore size), and membrane thickness. Here, DCMD membranes are produced using polymeric solution of 22 wt% Polyvinylidene Fluoride (PVdF) in Dimethylacetamide (DMAc). In the free surface electrospinning setup, a rotating wire spindle was partially submerged in a solution bath and a voltage of 40 kV was applied. The electric field causes charge to accumulate on the free surface, leading to the formation of electrohydrodynamic jets. Electrospinning was performed in an environment with relative humidity ranging from 50-80 RH%. In the presence of high humidity, water absorbs into the electrohydrodynamic jets resulting in the phase separation of the PVdF. The gelled fibers were collected on a grounded rotating drum and were allowed to solidify under room conditions. The performance of the produced membranes was evaluated using an in-house built DCMD apparatus and the membranes were characterized by DCDM performance and scanning electron micrograph (SEM) images.