Preparation and Characterization of Graphene Oxide Modified Membranes for Water Treatment

Abstract

Today a third of the global population lives in water shortage country, one of the pressing needs of people throughout the world is adequate supply of drinking water. To satisfy the demand for an enormous amount of water required by expanding global population, there have been much erudite discussions and practical attempts covering a wide scope including wastewater reuse as well as desalination. Among several technologies, in particular, membrane bioreactor (MBR) and reverse osmosis (RO) process have attracted much attention in the field of wastewater treatment and desalination, respectively, due to various strengths such as high quality of treated water and a small footprint. However, MBR have membrane fouling which is the major obstacle in maximizing their efficiency leading to short membrane lifetime and high operating costs. Also, for the RO process, low energy efficiency still remains unanswered as a serious challenge in RO process over the past few decades. In this study, it is demonstrated that the application of graphene oxide (GO) to membrane fabrication can be a novel strategy to overcome the aforementioned residual problems with each membrane process. In detail, GO was applied to fabrication of polysulfone (PSf) ultrafiltration (UF) membrane for the improvement of hydrophilicity and electrostatic repulsion characteristics, and the anti-biofouling capability of GO nanocomposite membrane was proved to be effective in MBR. Furthermore, addition of GO enhanced mechanical strength of GO nanocomposite membrane due to its high modulus and aspect ratio, which enabled the GO nanocomposite UF membrane to have mechanical strength comparable to existing support layer for commercial RO membrane and highly porous structure simultaneously. It is worth noting that RO membrane consisting of the PSf/GO nanocomposite support layer outperformed others including commercial membranes as well as the previously reported membranes in open literature. Also noteworthy is increasing the porosity of support layer could lead to improving the efficiency of RO membrane. To clarify the reason why porous structure of support layer induces higher water permeability of RO membrane, a non-intrusive experimental method was devised for representing the characteristics of the support layer as related to water flux.