Preliminary study on the preparation and characterization of novel organophilic membranes used for organic extraction

Abstract

Extractive membrane bioreactor (EMBR) process has become a new research focus in the treatment of recalcitrant organic pollutants. The membrane applied in this process enables biodegradation performance to be independent of wastewater conditions. However, the commercially available silicone rubber membrane made of PDMS limits the EMBR performance due to a small mass transfer coefficient. Hence, thin film composite (TFC) membrane has been proposed for the membrane extraction process due to its improved mass transfer efficiency. It consists of one non-porous selective layer attached upon the micro-porous support layer. The objective of this paper is to develop a TFC membrane specially for EMBR process. The preparation of the TFC membrane in this work involved non-solvent induced phase inversion and dip coating methods. The characterization of the membrane was conducted, including morphology observation and swelling behaviour test. TFC membrane modules were also assembled into performance test systems to undergo the leakage test and aqueous-aqueous extractive test. These tests analyzed the membrane’s chemical robustness, long-term stability and effects of feed solution pH and hydrodynamic conditions on mass transfer rate. Finally the paper concludes that all of the in-house hollow fiber TFC membranes demonstrated larger overall mass transfer coefficients compared to that of commercial silicone tubings. TFC membrane with PDMS complete intrusion was chemically robust under extreme conditions and long operation period but at an expense of low mass transfer rate. When the feed wastewater was of pH higher than 8, it was suggested to adjust the pH of feed stream to below 5 to ensure the majority of phenol is present in the form of phenol molecule. Lastly, the test proved that increase in Re at two sides of the membrane indeed decreased liquid boundary layer resistance. But membrane resistance remained to be the dominant impedance for phenol mass transfer across the membrane.