Graphene Coated Microfiltration Ceramic Membrane Fabricated by Photothermic Conversion of Polyimide

Abstract

In this study, a novel technique has been developed for the fabrication of uniform, stable, and strongly bonded graphene layers on microporous ceramic membranes. A composite ceramic-LIG membrane was obtained following one step scalable methodology. First, the ceramic support was spin-coated with poly (pyromellitic dianhydrideco-4, 4´-oxidianiline, amic acid) (PMDA-ODA) and transformed to polyimide (PI) by thermal imidization. The PI was then irradiated with a CO₂ laser to photothermally convert the sp³-carbon atoms to sp²-carbon atoms. Different PMDA-ODA layers were applied to achieve uniform coating by LIG on the membrane surface. The LIG was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and contact angle (CA) measurements. FTIR results showed a complete conversion of PMDA-ODA to PI following the thermal imidization reaction. The XRD results revealed the crystalline structure of graphene layer, which had a surface area of 130 ± 5.6 m²/g, determined by BET nitrogen adsorption. However, the permeability of uncoated ceramic membranes decreased with increasing number of PMDA-ODA layers, as evidenced by the clean water filtration experiments. The new composite membrane is a promising new material for membrane distillation or electro osmosis, where the hydrophobicity of the graphene layer may provide important advantages over current membrane materials.