Graphene Oxide/Titanium Dioxide Membranes

Abstract

During recent years, graphene has been studied intensively because of its unique characteristics, making it usable for a variety of applications. In order to produce graphene, it is rst necessary to oxidize graphite to graphene oxide and then reduce it to graphene. Tests have shown that graphene oxide could possibly be used as a membrane material for water treatment, as its oxygen-rich functional groups provide high hydrophilicity, while the graphene structure ensures excellent selectivity. A major limitation in membrane ltration is the fouling phenomena, which is why TiO2 could be of interest in membrane usage. TiO2 is used to clean surfaces via its photocatalytic properties. The purpose of this project was therefore to investigate graphene oxide as a membrane material and incorporate TiO2. Dierent graphene oxide syntheses were tested and dierent GO/TiO2 ratios were also tested. The thermal treatment process for reducing graphene oxide was also tested in order to nd optimal reduction time and temperature for stable membranes. The thermal reduction was evaluated using X-ray diraction (XRD), dierential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The surface characteristics were examined before and after UV-C irradiation, in order to see if the TiO2 provided signicant changes. Surface characteristics were analyzed using drop shape analysis (DSA), zeta potential measurements and FT-IR. The vapor permeance of the membranes produced was tested with water, ethanol and hexane. Scanning electron microscopy (SEM) was also done in order to see any potential membrane damage as a result of UV-C irradiation. The membrane surface characteristics and permeance were compared to that of two commercial membranes; Alfa Laval NF99HF and NFT50. By comparing the dierent syntheses via XRD and FT-IR, it was concluded that the Tour's method was best suited for further experiments. From the reduction experiments done, it was found that reduction at 140◦C for one hour produced the most stable and hydrophilic membranes. The optimal GO/TiO2 ratio was found to be in the range of 15:1 - 30:1. The TiO2 added to the graphene oxide membranes was found to signicantly enhance hydrophilicity and anti-fouling properties, caused by the formation of hydroxyl groups at the surface. SEM tests were inconclusive as to whether the membrane is damaged by the photocatalytic activity of TiO2. The water vapor permeance was found to be close to unimpeded and at least 55% higher than the commercial membranes tested

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A master thesis from Aalborg University

Graphene Oxide/Titanium Dioxide Membranes