4 july 2014

JPEG - 9.5 ko


Ph.D. Candidate
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States


Kamitis : The future security of freshwater resources around the world is of increasing concern. Can you present us your research concerning desalination ?

D. COHEN-TANUGI : I am using nanotechnology to make water desalination more energy-efficient, accessible and economical. While we traditionally had access to groundwater and surface water (e.g. rivers) to meet all our needs, these resources are becoming increasingly scarce as well as polluted. As a result, many countries are starting to look at desalination, which involves obtaining fresh water from a saltwater source like the ocean. In the past, only desert countries such as Saudi Arabia relied on desalination, but nowadays cities as diverse as Mumbai, Beijing and San Diego are also resorting to large desalination plants to meet their water needs.

I am in the fourth year of my Ph.D. studies in the Department of Materials Science & Engineering at MIT. Together with my adviser, Professor Jeffrey Grossman, and two fellow graduate students, Shreya Dave and Brendan Smith, we are working to design, produce and test new membranes that would desalinate water more efficiently. In 2012, we predicted using computer simulations that a material called nanoporous graphene would reject salt thanks to sub-nanometer pores while letting water flow at 1000 greater permeability than conventional polymer membranes. This prediction was followed by an avalanche of new interest in water purification applications among physicists and materials science, which is very good news.

Since 2012, we have made significant progress in understanding how such a membrane would work and in exploring the best pathways to produce this material and fully leverage its benefits for society.

Kamitis : You also studied nanostructures like graphene for water desalination. Are nanomaterials a strategic lever for next generation membranes for clean water technology ?

D. COHEN-TANUGI : I believe we need several revolutions in the water sector in the 21st century. We are going to need important changes in the policy, economics and public behavior regarding water production, pricing and usage. At the same time, I believe nanomaterials have a critical role to play in the future of clean water.

Since my work has been focused on nanomaterials for advanced membranes, I can talk about this opportunity more specifically. My group has shown that a desalination membrane that is just three times more permeable to water would allow for up to 15% less energy consumption. This goal is within reach of contemporary materials science, especially because the academic fields of materials science and applied physics have traditionally ignored clean water applications. In other words, I believe there is a lot of low-hanging fruit for nanomaterials science to improve the clean water sector.

Kamitis : Your research suggest that advances in membrane science will continue to make desalination increasingly competitive as an option for fresh water supply in coming decades. In your opinion, what are the issues and challenges that membrane technology can meet tomorrow ?

D. COHEN-TANUGI : Innovative membrane technologies will continue to enable greater efficiencies in existing water applications, and they will also enable new applications altogether. In my opinion, the biggest challenges that membrane technology can meet tomorrow are the treatment of highly polluted waters, for example from shale gas production with hydraulic fracturing, as well as continuing to fill the growing gap between supply and demand for fresh water around the world.

More innovations are still needed, however. Membranes today are still too prone to organic fouling and to mineral scaling, leading to lower fluxes, shorter membrane lifetimes, and much more complex pretreatment steps than would be needed otherwise. RO membranes are also insufficiently selective to uncharged species like boron.

Overall, the future of membrane technologies is bright. The field of nanotechnology has much to contribute to the development of next-generation membranes, and greater R&D initiatives around membrane technology worldwide can help us innovate towards a better, cleaner tomorrow.