In situ assembly of graphitic carbon nitride/polypyrrole in a thin-film nanocomposite membrane with highly enhanced permeability and durability

Abstract

Although thin-film nanocomposite (TFN) membranes have been proposed as a competitive approach for improved reverse osmosis performance within the last decade, their intrinsically poor organic-inorganic interfacial compatibility and low durability still hinder further upscaling. In this study, a new in situ assembly strategy is proposed to solve this dilemma by using polypyrrole (PPy) to build a bridge between polyamide matrix and nanomaterial (graphitic carbon nitride, g-C3N4) and further fabricate g-C3N4/PPy-incorporated TFN membrane. The synthesized g-C3N4/PPy nanocomposites are hybridized into the interfacial polymerization process, which endows the TFN membrane with a smaller “ridge-valley”, higher hydrophilic and thinner polyamide layer. With 0.005 wt% of g-C3N4/PPy, the water permeability of TFN membrane is increased to 377 % (4.0 L·m−2·h−1·bar−1), while keeping a similar NaCl rejection (99.1 %) to pure polyamide membrane. Importantly, the resulting TFN membrane exhibits high chlorine resistance in acidic, neutral and alkaline environments. Moreover, the TFN membrane has superior antifouling performance for organic, inorganic and mixed organic-inorganic foulants, which is of vital importance for the long service life of TFN membranes. This study offers a facile avenue to solve the application needs of advanced TFN membranes for efficient desalination with stable high-quality water.