(752e) A Simple Approach for Functionalization of Poly(vinylidene fluoride) (PVdF) Membranes for Desalination of Oil-Contaminated Saline Water Using Membrane Distillation

Desalination of oil-contaminated water by using membrane distillation is a promising approach to recover valuable products. The membranes needed for this process must possess special wettability. More specifically, the whole membrane should be hydrophobi, yet the surface in contact with the oil-water emulsion must be oil-repellent. To achieve this, introducing chemical heterogeniety and the desired surface topography to the hydrophobic membranes is required. Creating a hydrophilic surface with the desired surface topography will allow the water to wet the surface. Protecting the surface with a film of water prevents oil adhesion to the surface of the membrane and creates underwater oleophobicity. Here, we developed an approach to control the structure of Poly(vinylidene fluoride) (PVDF) membranes and selectively functionalize the surface intended to be exposed to the oil-water emulsion. We demonstrated that the morphology of the PVDF membrane can be simply adjusted by changing the composition of the polymer solution and the coagulation bath used during the phase inversion process. Additionally, we introduced a one-step process to chemically modify the membrane surface, rendering it more hydrophilic. We confirmed that the membrane surfaces are functionalized using a variety of characterization methods such as x-ray photoelectron spectroscopy (XPS), flourier transformed infrared spectroscopy (FTIR), zeta potential, and under-water oil contact angle. The scanning electron microscopy images showed that alkaline treatment did not damage the membrane structure. Also, we observed an underwater contact angle (c.a. 150^o ) for the Hexane droplets in contact with the modified surface. The membranes were tested in a direct contact membrane distillation process to desalinate a saline solution including 500 ppm oil. The results showed that oil did not wet the membrane during 12 hours of continuous MD operation; the average water flux and salt rejections were measured at 1.6 Lm^-2h^-1 and 99.99%, respectively.