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Posted: Aug 24, 2017
Research to accelerate development of high-efficiency graphene-based membranes
(Nanowerk News) Masdar Institute announced a research breakthrough that provides valuable insights on the development of optimized graphene-based membranes, which aim to make water filtration and desalination more efficient and sustainable. The Masdar Institute is a part of the Khalifa University of Science and Technology.
The breakthrough was made by a team of researchers led by Dr. Linda Zou, Professor of Civil Infrastructure and Environmental Engineering, as they worked to develop membranes made of layered reduced graphene-oxide sheets that are able to block the passage of salt ions in a membrane-based seawater desalination process.
Dr. Linda Zou, Professor of Civil Infrastructure and Environmental Engineering, is improving the way optimized graphene-based membranes are developed. (Image: Masdar Institute)
Seawater desalination is a costly and energy-intensive undertaking that produces over 80% of the UAE’s freshwater. With such a heavy reliance on desalination, there is a critical need for efficient and sustainable technologies that will reduce its environmental and economic costs. One type of technology that may be able to provide those valuable savings is graphene-based membranes.
The tiny weight and size of graphene, which is a nanomaterial about 100,000 times thinner than the diameter of a human hair, coupled with its mechanical strength and durability, make it well-suited for an energy-efficient and environmentally-friendly generation of water membranes. In fact, graphene for water purification is increasingly being seen as a significant commercial market for graphene.
The graphene-based membranes developed in this work are made of multiple of layers of thin reduced graphene oxide sheets. The spacing between the sheets is what ultimately affects the membrane’s efficacy, or its ability to filter impurities like salt ions while still permitting water molecules to pass through. The spaces between sheets must be just right – if they are too large and salt ions are not filtered out, and if they too small and even water molecules are unable to penetrate the membrane.
Being able to fine-tune the spacing size between layers is one of the most difficult challenges to developing efficient layered graphene membranes. Previous studies revealed that the optimal space between graphene sheets could be between 0.6nm and 0.7nm. Given this very narrow size range, a slight variation significantly affects the functionality of the membrane. Dr. Zou believes that her research provides a needed tool which will help scientists better fine-tune the size of inter-layer spacing.
Dr. Zou’s team used atomic force microscopy (AFM) to probe the edges of each graphene sheet to obtain measurements of the exact height of the spaces between each sheet. They then combined these AFM measurements with statistical analysis to reveal the relationship between the amount of the chemical used to make layered reduced graphene oxide membranes, known as a reducing agent, and the resulting size of the spacing between each graphene layer. They described their research in a paper that was published in ACS Applied Materials and Interfaces ("Insights on Tuning the Nanostructure of rGO Laminate Membranes for Low Pressure Osmosis Process").
Dr. Steve Griffiths, Interim Executive Vice President for Research, Khalifa University of Science and Technology, said: “The research and development of technologies aimed at achieving energy-efficient desalination through the use of advanced materials like graphene is at the core of Masdar Institute’s research agenda. The work conducted by Dr. Zou and her team is an important contribution to the development of cost-effective and environmentally-sustainable technologies for growing clean water demand in the UAE and globally.”
Dr. Zou is also leading a collaborative research project with The University of Manchester – credited as the ‘birthplace’ of graphene – that aims to incorporate graphene into membranes for electrically-driven membrane desalination strategies, such as electrodialysis and capacitive deionization.
Developing efficient and sustainable technologies for the production of freshwater is one of the most pressing and crucial challenges currently facing the world. That is why Masdar Institute has several research teams pursuing a range of research projects dedicated to the development of next-generation water filtration and desalination technologies needed to make freshwater production affordable and environmentally friendly.