(381c) Separation Applications of Reduced Graphene Oxide Membranes

Reduced graphene oxide (rGO) membranes have attracted increasing attention of the membrane community for aqueous and organic solvent nanofiltration applications. Although polymeric membranes can perform separations in this regime, same polymeric membrane platform cannot be extended to both aqueous and organic solvents. This research demonstrates the potential application of rGO membranes for treatment of water contaminated with emerging contaminants (perfluoroalkyl substance, PFAS) from water and separation of high-value lignin-derived oligomeric compounds from polar organic solvents. PFAS are negatively charged molecules and are expected to experience charge repulsion and steric hindrance from the rGO membranes. High removal of Perfluorooctanoic acid (PFOA) by rGO membranes was achieved, exhibiting 80% removal for 1 ppm feed at pH 7. Extensive retention studies conducted with PFOA suggested a charge-exclusion dominated mechanism for removal of PFOA. High rejection of PFOA at a high recovery of water observed in our study signifies the potential application of rGO membranes in the treatment of trace contaminants. Another application of rGO membranes investigated in this study was in organic solvent nanofiltration. The primary aim of this study was to examine the selective separation of lignin-derived oligomeric units from polar organic solvent media. This study addresses challenges in selective separation of the lignin depolymerization products, which is vital to fractionate and isolate high-value phenolic compounds. Impressive performance, with the rejection of over 70% for the model trimer, was achieved compared to only 20% rejection for dimer in the isopropanol-water mixture as a solvent. This corresponds to an encouraging selective separation with selective permeation of dimer 3.5 times compared to BMP trimer. Furthermore, selective separation of GO can be effectively modulated by controlling the extent of reduction of GO. Retention of trimeric compounds increased upon increasing the extent of reduction of GO. Remarkable performance of GO membranes could enable energy efficient fractionation of lignin oligomeric compounds from polar organic solvents. This research has been supported by NSF KY EPSCoR and by NIEHS-SRP.