(638e) Hydrophobic Membrane Surface Energy Varied By Plasma Enhanced CVD: Effect on Oil/Water Emulsion Separation

While attention and membrane development has focused on moving the aqueous phase across a membrane, recent materials research has focused on removing the organic phase from water¹ in a method somewhat analogous to the natural geological process whereby streams and rivers are cleaned by rock and soil. However, the mechanism of oil separation from water at a hydrophobic membrane surface is not clearly understood. Tirmizi et al. studied the effect of pore size, surfactant concentration and applied pressure on separation efficiency and flux². They found the separation efficiency to be independent of pore size for polypropylene membranes containing 0.02 to 0.2 µm pores and observed a linear to limiting flux behavior with pressure as they increased the surfactant concentration from zero to 30 kg/m³. Tirmizi et al. did not consider the effect of surface energy. Ochoa et al. considered the effect of material surface energy on membrane fouling for membrane surfaces having intrinsic water contact angles of 50 to 84 degrees³ but lower energy surfaces were not considered.

To better understand the interactions between hydrocarbon in water emulsion and the surface of a hydrophobic membrane, we vary the surface energy of hydrophobic polypropylene membranes using plasma enhanced chemical vapor deposition⁴. Trans-membrane flux and concentrations of hydrocarbon (tetradecane) and water in the permeate and retentate are monitored to determine the rate and efficiency of separation as a function of surface energy.

[1] Zhongxin Xue, Yingze Cao, Na Liu, Lin Feng, and Lei Jiang. J. Mater. Chem. A, 2:2445-2460, 2014.

[2] Neena Pradhan Tirmizi, Bhavani Raghuraman, and John Wiencek. AIChE Journal,

42(5):1263-1276, 1996.

[3] N.A. Ochoa, M. Masuelli, and J. Marchese. Journal of Membrane Science, 226(1{2):203-211, 2003.

[4] Ila Badge, Sarang P. Bhawalkar, Li Jia, and Ali Dhinojwala. Soft Matter, 9:3032-3040, 2013.