Water Resources Engineering (WRE) connects engineering hydrology and hydraulics with global, economic, environmental, and societal issues. Our student Daryl Harper makes this connection here…

 

The article, “Precise and Ultrafast Molecular Sieving through Graphene Oxide Membranes”, was posted on the website sciencemag.org on February 14, 2014. The news relates to the WRE domain of hydrology and specifically to the filtration of water. It is basically about a scientific team out of the University of Manchester which has come up with some new filtration applications for graphene oxide, an oxidized crystalline allotrope of carbon. Scientists have been experimenting with how this material can be used as a nanofilter due to its unique interaction with water. Narrow capillaries made from meshing layers of graphene oxide vigorously suck in individual molecules of water allowing its rapid permeation. They permeate through the interconnected nanochannels formed between graphene oxide nanosheets and follow a tortuous path primarily over the hydrophobic nonoxidized surface rather than the hydrophilic oxidized regions. It also blocks all other gases and any solids bigger than the capillaries which scientists have been able to reduce down to 0.45 nanometers. Figure 1 shows an image of the effectiveness the filter.

Figure 1

Figure 1

Based on my engineering education I believe that the data provided in the article is accurate and a great testament to the potential uses of the chemical properties of graphene. The numbers that this article came up with for the size of the capillaries their graphene oxide mesh can have were consistent with data released by another article titled, “Graphene Oxide Membranes for Ionic and Molecular Sieving.” I understand that this is still a relatively new study working with a material for which the cause of its chemical properties and interactions with water are not fully understood, but I believe more information could have been provided about how effective this filter is in a dry vs. aqueous solution. Even the smallest molecules have variance in their diameter depending on whether they are saturated or not and more info could have been provided on how the team is working to overcome this.

 

The end goal of those working on this project is to be able to create a filter that can filter the salt ions themselves out of sea water. This will result in new ways of acquiring fresh water for human use which is a huge global and economic issue we will be facing in the years to come. Water shortages are at all-time highs all over the world and things are beginning to get tense as societies are competing for less available water sources to meet their constantly increasing demand. Some sources have predicted that wars could be started within the next fifty years over this precious resource so any new technology that can add to the collective pool of water resources we all have to work with can prolong such conflicts from arising and also help regions where water shortages are already at dangerous levels.

References

Graphene Oxide Membranes for Ionic and Molecular Sieving. Baoxia Mi Science 14 February 2014: 343 (6172), 740-742. [DOI:10.1126/science.1250247]

Precise and Ultrafast Molecular Sieving Through Graphene Oxide Membranes R. K. Joshi, P. Carbone, F. C. Wang, V. G. Kravets, Y. Su, I. V. Grigorieva, H. A. Wu, A. K. Geim, R. R. Nair Science 14 February 2014: 343 (6172), 752-754. [DOI:10.1126/science.1245711]

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