Plasma Polymerization Modified Polyvinylidene Fluoride (PVDF) Membrane Development and Characterization for Degumming of Soybean Oil

Unmodified and surface-modified polyvinylidene fluoride (PVDF) membranes were tested for their ability to degum soybean crude oil and crude oil miscellas. The membrane was modified with 1,1,1,3,3,3-hexafluoro-2-propanol or hexamethyldisiloxane (HMDSO) by radio-frequency plasma polymerization at 10–100 W glow discharge power and 1–30 min contact time. The membranes were characterized by contact angle measurements, attenuated total reflectance Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. Modification of the PVDF membrane with HMDSO at 60 W power for 5 min increased the interfacial free energy between water and solid surface from 30 ± 2 to 64 ± 2 mJ/m². This membrane was tested for permeate flux and phospholipid rejection with crude oil and different concentrations of miscella. Although formation of the polymer film on the membrane tended to decrease membrane pore size, the modified membrane had an oil flux as good as the unmodified membrane did. In addition, the modified-membrane improved the phospholipid rejection and removed 76 % of the phospholipids from the crude oil and 81–90 % of the phospholipids from crude oil miscellas.