Graphene Coated Microfiltration Ceramic Membrane Fabricated by Photothermic Conversion of Polyimide
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Graphene Coated Microfiltration Ceramic Membrane Fabricated by Photothermic Conversion of Polyimide Mohamed Bayati1, Haiming Peng1, Heng Deng2, Jian Lin2, Maria Fidalgo1 1 Civil and Environmental Engineering, University of Missouri, MO 65211, U.S.A. 2 Mechanical & Aerospace Engineering, University of Missouri, MO 65211, U.S.A.
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 ceramicLIG 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.
INTRODUCTION Membranes have become a promising advanced technology for solving massive environmental challenges such as the limited availability of water resources, and its growth is partially related to advances in materials that create opportunities for better performance and new functionality. Compared with conventional separation methods, membrane processes may be an energy-efficient and environmentally type of technology, that has a smaller footprint and can be operated in a continuous manner [1]. An ideal membrane provides high permeate flux, high selectivity and improved stability through controlled pore size and shape. Furthermore, the reduction of membrane thickness is essential to minimize operational pressure, achieve higher throughput and increase membrane performance [2]. Graphene- based nanomaterials have been widely studied because of their unique physical and chemical properties; for instance, ultimate thinness, flexibility, chemical stability, and mechanical strength [3]. Thus, to take advantages of these properties, a novel technique has been used to fabricate a uniform, stable, and strongly bonded graphene layer on a microporous ceramic membrane acting as support material, through laser treatme
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