Smoothing the wrinkle formation and improving dye rejection performance in porous graphene oxide membranes using high surface curvature hollow fiber substrates

Abstract

Assembly of atomic-scale thin two-dimensional (2D) graphene oxide (GO) nanosheets into a membrane with macroscopic three-dimensional (3D) laminar structure is accompanied by the formation of wrinkles. The size and pattern of wrinkles, which depend on the substrate curvature and the thickness of the 3D laminar structure, adversely affect the separation performance of the membrane. Therefore, smoothing the formed wrinkles is essential to boost the separation performance of GO-based membranes. For the first time, we proposed a new approach to prepare porous hollow fiber (HF) yttria-stabilized zirconia (YSZ) substrates with small-diameter (660–790 μm, outer diameter (OD)) by stretching the nascent HF using gravitational force. Also, using a delayed phase inversion, a plurality of radial micro-channels opening from the interior surface of HFs can be realized. The resultant HF substrates show promising permeation characteristics and good fracture strength owing to their open microstructure and the robustness of YSZ. Small-diameter HF substrates (OD = 660 μm) with higher surface curvature ensured the fabrication of porous GO (PGO) membranes with better dye separation performance. The rejection of methyl red (MR, MW = 269.3 g mol−1) dye molecule for small-diameter HF PGO membranes (OD 660 μm) was 10%–167% higher than that of membranes fabricated using large-diameters (OD 1250–2600 μm). This study shed light on the fabrication of high-performance thin film membranes by tailoring the geometric features of substrates.