Title: Investigation of the pH-induced changes in the properties of polyethyleneimine-crosslinked graphene oxide membranes for desalination and heavy metal ions separation

Conference Name: 2023 International Membrane Conference in Taiwan

Award: Gold Medal Award

Abstract: Graphene oxide (GO) membranes have been extensively investigated and employed in separating various ions and molecules due to their superior physicochemical properties. However, the inconsistency in their pore structure, difficulty in the precise tuning of d-spacing, and instability in aqueous solution – especially at extreme pH values – might hinder their separation efficiency. In this research, we systematically investigate GO’s behavior when dispersed in various pH values and subsequently inspected the properties and nanofiltration (NF) performance of the resulting membranes fabricated from such dispersions. Furthermore, polyethyleneimine (PEI) was used to crosslink GO, and the effect of pH on the crosslinking process and the resulting GO-PEI membranes’ performance were studied. Characterization results revealed that the pH could induce significant changes in the d-spacing, thickness, and free volume of the membranes. Moreover, the protonation and deprotonation of certain functional groups in GO and PEI have a considerable effect on the surface properties and chemical composition of the membranes. These findings contributed to the NF performance of the membranes against different inorganic salts and heavy metal ions. It was discovered that the GO-PEI membrane formed at pH 11 has the highest Pb2+ rejection of >95%, making it a suitable material for heavy metal ions removal.