Preparation Of Self-assembly Graphene Oxide Nanofiltration Membrane And Study Of Its Desalination Mechanism

With the development of economy, the public pays more and more attention to the environment problems, among which, the security of water resources has been the key point for countries, companies as well as citizens. As a kind of efficient and energy-saving water treatment technology, membrane separation has been widely used. And the key point of membrane separation technology is the property of membrane materials. The utilization of nano materials on membranes modification has always been the research focus. In recent years, Graphene, a novel carbon material, has made remarkable progress. In addition, Graphene oxide, as the derivative of graphene, which owns oxygen-containing functional groups on the top and edge of grapheme, has attracted increasing attention due to its outstanding properties.In this research, graphene oxide is fabricated based on Hummers’method and the solution is prepared through ultrasonication. Then graphene oxide solution is compounded on the polysulfone ultrafiltration membrane via self-assembly technology to prepare the grapheme oxide membrane. In order to confirm the properties of GO, the synthesized product is characterized by atomic force microscopy(AFM), X-ray diffraction photometer(XRD), infrared spectroscopy(IR), Raman spectra and X-ray photoelectron spectroscopy(XPS) to confirm the properties of GO. The separation performance is also evaluated. The results show that fabricated graphene oxide is mostly monolayer with the thickness about 0.8nm and the grapheme oxide membranes have obvious stratified structures.As the thickness of graphene oxide functional layer increases and the oxidation degree of graphene oxide decreases, the flux of membranes decreases and the salt rejection increases. By means of adjusting the intensity of ultrasonic processing, the flux can be improved. What’s more, compared with the traditional nanofiltration membrane, the augment of temperature can increase the membrane’s permeability and remain the rejection almost invariable.Due to the flexibility of graphene oxide and features of pressure assisted self-assembly method, there are numerous large-sized channels inside the fabricated graphene oxide composite nanofiltration membrane so that the rejection performance is inferior to the estimated theoretical value. Under the constant effect of pressure, the membrane flux drops exponentially. Furthermore, the flux decrement goes up with the increase of the continuous pressure. After compaction, the salt rejection increases to some extent. It proves that the channel dimensions reduce under the effect of pressure.In summary, graphene oxide nanofiltration membranes which are fabricated by pressure assisted self-assembly method have the desalination performance through the size sieving effect of water channel and the surface charge effect of oxygen-containing functional groups. The thickness of functional layer, the number of water channel as well as degree of oxidation can affect the performance of the membrane. While the rejection is constant, graphene oxide nanofiltration membranes have better permeability under the high temperature.