A portable seawater desalination device

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A portable seawater desalination device

Chinese scientists have invented a portable seawater desalination device, resembling a thermos in both shape and size and weighing less than a kilogram. This innovative device can provide fresh water for over a week to those stranded at sea.

At the 2023 Shanghai Science and Technology Awards announced on Wednesday, the project titled "Theoretical Study on the Dynamic Properties of Solid-Liquid Microscopic Interfaces and Its Applications" led by Professor Fang Haiping from the School of Physics at East China University of Science and Technology won the First Prize in Natural Science. The portable desalination device is one of the project’s practical applications.

The principle behind this "thermos" desalination device lies in its use of a special graphene oxide membrane, which effectively blocks and filters salt ions while allowing water molecules to pass through, converting seawater into fresh water.

Graphene, a carbon-based material with a honeycomb-like planar membrane, has a unique two-dimensional structure, making it hightly promising for applications in energy, materials, and other fields. Researchers worldwide are now interested in using graphene’s properties to create high-performance separation membranes, addressing core technical challenges in areas like wastewater treatment and seawater desalination.

However, achieving this goal requires controlling the interlayer spacing of graphene with extreme precision -- down to one-tenth of a nanometer. Fang Haiping, who has long been focused on water research, began tackling this challenge in 2008.

Chemists had previously discovered on that graphene's honeycomb structure exhibits a special electronic behavior called π-electrons, which can strongly interact with cations like sodium ions, forming an ion-π interaction. However, this interaction is often overlooked in aqueous solutions due to the presence of hydrated ions.

Based on statistical physics theory, Fang's team recognized the significance of ion-π interactions in aqueous solutions. By combining quantum mechanics calculations, they developed computational software, and proposed using ions to precisely control the interlayer spacing of graphene membranes to accurately achieve ion sieving and seawater desalination. Their theory was successfully validated through experiments, and the related research paper has been published in Nature.

Building on their fundamental research, the team developed a practical graphene composite seawater desalination membrane. According to installation test results, the water flux of this membrane is about 15 times that of Dow's seawater desalination membrane, making it one of the most advanced practical desalination membranes currently available. Additionally, the team developed a portable seawater desalination device the size of a thermos, which has been included in the Shanghai Green Technology Directory.

Haiping Fang is a professor at the School of Science, East China University of Science and Technology. He obtained his bachelor’s degree and master’s degree from Shandong University, in 1985 and 1988, respectively. He received his doctorate from the Institute of Theoretical Physics, Chinese Academy of Sciences, in 1994. He was a postdoctoral fellow at Fudan University from 1994 to 1996. He was a visiting scholar at the Hong Kong University of Science and Technology from 1997 to 1998, and a visiting associate professor at John Hopkins University in the United States from 2000 to 2001. He was a researcher at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences, from 2001 to 2018, and has been the director of the Water Science and Technology Laboratory since 2012. He was the director and researcher of the Water Science and Technology Laboratory at the Shanghai Advanced Research Institute of the Chinese Academy of Sciences from 2018 to 2020. His research mainly focused on the interdisciplinary research of interfacial water, nanobiology, and theoretical physics, and especially the properties of water and ions in confined scale space and the properties of biomolecules induced by them, and the development of new materials. He has been awarded the National Outstanding Youth Science Fund, Shanghai Discipline Leader, and Shanghai Leading Talent awards.

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