Ultrathin graphene-based membrane with precise molecular sieving and ultrafast solvent permeation
Journal: Nature Materials
Publication Date: 13 November, 2017
Graphene-oxide membranes filter organic solutions
The application of graphene-based membranes for organic solvent nanofiltration (OSN) has received very limited attention so far. This could be due to the fact that graphene oxide (GO) membranes were previously shown to be completely impermeable to all solvents except for water. Now an international group of researchers, led from the University of Manchester, have challenged this view. They show that that ultrathin GO membranes are highly permeable to organic solvents (e.g., alcohol) without sacrificing their atomic-scale sieving properties. This is the first clear-cut experiment showing the great potential of GO membranes for OSN, where solutes molecules are separated from organic solvents. Developing OSN membranes has proven extremely challenging because the conventional polymeric membranes are highly unstable in organic solvents while ceramic inorganic membranes are costly and lack separation efficiency. The researchers explain the ultrafast permeation of organic solvents combined with precise sieving by the presence of randomly distributed pinholes in the membrane which are interconnected by 1 nm wide nanochannels provided by aligned GO sheets. They also show how a transition from high permeability to complete impermeability with respect to organic solvents can occur in GO membranes. As the membrane thickness increases, the organic solvent permeance decays exponentially whereas water continues to permeate anomalously fast through graphene nanocapillaries. This behaviour is explained by changing the dominant permeation pathway, from pinholes to graphene capillaries, and resolves some long-standing controversies in this research field. This research is expected to have applications in the pharmaceutical and petrochemical industries.
- Graphene oxide (GO) is like ordinary graphene but is covered with molecules such as hydroxyl groups, and GO sheets can easily be stacked on top of each other to form extremely thin, but mechanically strong, membranes. These membranes consist of millions of small flakes of graphene oxide with nanosized empty channels (or capillaries) between the flakes.
- Organic solvent nanofiltration (OSN) technology separates charged or uncharged organic compounds from an organic solvent.
- Chemical separation is all about energy. Various chemical separation processes consume about half of industrial energy useage. Any new efficient separation process is important because it helps minimize the consumption of energy. By 2030, the world is projected to consume 60% more energy than today.
- National Graphene Institute, The University of Manchester.
- Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, China.
- Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China.
- Department of Physics, University of York, York.
- Imdea Nanociencia, Faraday 9, 28015 Madrid, Spain.