Fabrication of PDMS/PVDF Composite Pervaporation Membrane for Food Waste Treatment Open Access
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Food waste is becoming a serious problem in the U.S. According to the report, about 40% of the food in the U.S. is wasted. Fermentation is a method to recycle the food waste and it can convert the food waste to organic matters like acetone, butanol, and ethanol (ABE). By pervaporation the ABE can be recovered from the fermentation broth. In this study a type of polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) composite membrane was fabricated to develop a novel pervaporation membrane. Electrospinning was used to fabricate a PVDF nanofiber membrane to be the support layer for the composite membrane, and heat pressing was used to enhance the mechanical structure of the PVDF membrane. Next a PDMS layer was coated on the support layer evenly by spin coating. To improve membrane mechanical strength and integrity, concentration of PVDF solution, temperature and duration of heat pressing, and thickness of PDMS layer were optimized. 15 wt % of PVDF dissolved in DMF/acetone (the solvent volume ratio was 7/3) was the optimized material for electrospinning, and the nanofiber diameter was 0.49 ± 0.11 μm. For heat pressing, with the increase of temperature and duration, the fiber roughness and number of fused fibers increased. The best temperature of heat pressing was 155 °C and the best duration was 60 mins, under which the treated PVDF membranes remained flexibility with improved mechanical strength and integrity. In the spin coating process, the spin rate of 600 rpm, 800 rpm, 1000 rpm, 1200 rpm, and 2000 rpm were tested, and the results showed thickness of PDMS layer and spin rate had a relatively stable negative correlation. With the increase of spin rate the thickness of PDMS layer decreased, and the thinnest PDMS layer was fabricated at 2000 rpm, whose thickness was 41.53 ± 2.71 μm. PDMS membrane is effective for the ABE recovery, especially for the butanol recovery. The PDMS/PVDF composite membrane fabricated in this study would show a great performance on food waste recovery if further study is conducted.