(339b) Improving Dye Removal Performance of Graphene Oxide Membranes By Etching and Polydopamine Intercalation

Graphene oxide (GO) has been extensively investigated for molecular-sieving membranes for water purification owing to the adjustable channel size and featured water transport path. However, its good dispersibility in water leads to poor durability, while conventional approaches of reduction and cross-linking improve the durability but decrease water permeance. Herein, we demonstrate an effective approach to enhance water permeance while maintaining durability by chemical etching to create holey GO (HGO) nanosheets and intercalation with polydopamine (PDA) nanoparticles. Specifically, GO nanosheets were chemically etched for 2 or 4 h using H₂O₂ to obtain HGO2h or HGO4h, which were then co-deposited with dopamine on porous supports. The prepared membranes were thoroughly characterized using SEM, AFM, TEM, and XPS. The nanopores created on the HGO shorten the diffusion path, increasing the water permeance, while the PDA intercalation changes the channel sizes and increases durability. For example, PDA/GO membrane with a thickness of 50 nm shows water permeance of 27 LMH/bar, while the PDA/HGO4h with a thickness of 31 nm shows water permeance of 274 LMH/bar. Increasing the selective layer thickness increases the dye rejection. Besides, centrifugation treatment of HGO could also increase the dye rejection of the PDA/HGO membranes presumably because the removal of small pieces of HGO nanosheets contributes to a more regular stacking of HGO. The optimized membrane with 34 nm PDA/HGO2h exhibits high water permeance of 141 LMH/bar and a Congo Red rejection of 98.0%. Moreover, the membrane exhibits stable performance in a 3-day continuous cross-flow filtration test, indicating its durability and potential for practical applications.