Development of high water permeability and chemically stable thin film nanocomposite (TFN) forward osmosis (FO) membrane with poly(sodium 4-styrenesulfonate) (PSS)-coated zeolitic imidazolate framework-8 (ZIF-8) for produced water treatment

The generation of large volume of produced water necessitates a chemically stable membrane with high water permeability for the removal of oil emulsion. In this work, a zeolitic imidazolate framework-8 (ZIF-8) based thin film nanocomposite (TFN) membrane with improved pure water permeability and chemical stability was developed. It was found that poly(sodium 4-styrenesulfonate) (PSS) coating could stabilize the ZIF-8 particles against dissolution in water. This subsequently allowed the proper formation of TFN membrane with comparable separation properties as the thin film composite (TFC) membrane. With the further use of triethylamine (TEA) as an acid acceptor in interfacial polymerization, the pure water permeability of TFN membrane improved significantly over both TFC and TFN membranes synthesized without TEA with minimal loss in NaCl rejection. The enhanced water transport of TFN membrane was further manifested by the higher flux of TFN membrane compared to TFC membrane in forward osmosis (FO) filtration of both synthetic high salinity oil emulsion and real produced water. In addition, due to the chemically stable ZIF-8 particles, the TFN membrane was demonstrated to have a better swelling resistance against produced water than the TFC membrane.