Layer-by-layer assembly of graphene oxide (GO) on sulfonated polyethersulfone (SPES) substrate for effective dye removal

In the present study, a water separation GO-based membrane was synthesized such that water molecules can transport through the nanochannels between GO layers, while solutes (especially dye in this study) are rejected by size exclusion and electrostatic charge repulsion. First, polyethersulfone (PES) was sulfonated (SPES) with different degree of sulfonation, and then PES/SPES blend membranes with different content of SPES were prepared using immersion precipitation process. SPES provides efficient –OH groups for immobilizing GO on the substrate. To create the linkages between GO and substrate and also between GO nanosheets, 1, 3, 5-benzenetricarbonyl trichloride (TMC) was applied. Synthesized GO was characterized by Raman spectroscopy and XRD to confirm delamination of graphite and well-created oxygenated groups. FTIR, DSC, SEM, and contact angle techniques as well as pure water flux measurement were employed for characterization of prepared PES/SPES membranes. Finally, GO-coated membranes were examined by rejection test with three different aqueous dye solutions. The GO-based membrane exhibited relatively high rejection of dyes; they are 79.8, 83.73, and 90.38% for C.I. Direct Yellow 12, C.I. Direct Red 23, and C.I. Direct Blue 78, respectively. Our findings suggest that deposition of GO on a hydrophilic substrate i.e., SPES, is a promising approach for the development of novel nanocomposite membranes.