Zwitterion embedded thin film composite forward osmosis membrane for oily wastewater treatment

Abstract

The rising oil consumption in oil and gas industries has exacerbated the disposal of oil waste into the water stream. Hence, oily wastewater treatment is required to prevent threats to the human and environment. With some great advantages such as lower membrane fouling rate, lower energy requirement and higher water recovery rate compared to the conventional pressure-driven membrane processes, forward osmosis (FO) has been recognized as a potential candidate for oily wastewater treatment. In this study, zwitterionic polymer, poly[3-(N-2-methacryloylxyethyl-N,N-dimethyl)-ammonatopropanesulfonate] (PMAPS) was incorporated into thin film composite (TFC) membrane to render excellent anti-fouling properties to the membrane. PMAPS was blended with polyethersulfone (PES) polymer solution and cast into PES support layer. Interfacial polymerization technique was applied to form a thin polyamide layer a top of the PES support layer. The PMAPS incorporated TFC membranes were characterized for their morphology and surface hydrophilicity. The oily wastewater treatment performance of the PMAPS incorporated TFC membrane was evaluated through the FO process. The resultant 1% PMAPS-TFC membrane exhibited high water flux of 15.79±0.3 L/m2.h and oil flux of 12.54±0.8 L/m2.h when tested in FO mode for oil removal from oily wastewater using 1000 ppm emulsified oily solution as the feed solution and 2M sodium chloride as the draw solution. The oil rejection up to 99% was also obtained and most of the clean water was extracted from the feed solution. Most significantly, PMAPS incorporated TFC membrane outperformed neat TFC membrane with a lower fouling propensity for oily waste treatment. When treating 10000 ppm oil emulsion, PMAPS-TFC was able to achieve an average flux recovery rate of 97% while neat TFC was only able to achieve 70.8% of average flux recovery rate. Overall, the PMAPS incorporated TFC membrane has a great potential as it possesses superior hydrophilicity and strong anti-fouling behavior which helps to save the periodic cost of membrane replacement.