In an interview discussing the groundbreaking work of Professor Fang Haiping and his team from the East China University of Science and Technology, we explore the innovative portable seawater desalination device they have developed, as well as their significant achievements in graphene research.
Imagine the struggles faced by the young protagonist in Ang Lee’s film “Life of Pi,” who fights for survival in the vast ocean with the daunting challenge of finding fresh water. Now, what if he had access to a small handheld device that could swiftly convert seawater into drinking water? The survival chances would undoubtedly skyrocket.
On October 23, the Shanghai Municipal Science and Technology Award announced that Professor Fang Haiping’s project, “Theoretical Research on the Dynamic Properties of Solid-Liquid Interfaces and Their Applications,” received the First Prize for Natural Science. A notable outcome of this project is a lightweight portable desalination device resembling a thermos bottle, which weighs less than one kilogram and can provide over a week’s worth of fresh water to someone who has fallen overboard.
So, what is the secret behind this “thermos bottle” that can desalinate seawater? The principle is straightforward: it utilizes a special graphene oxide membrane that effectively blocks and filters out salt ions while allowing water molecules to pass through.
Graphene, known for its honeycomb structure made of carbon atoms, is recognized for its vast potential in energy, materials, and more, primarily due to its unique two-dimensional characteristics. Researchers globally are eager to leverage graphene’s properties to create high-performance separation membranes, tackling key technological challenges in wastewater treatment and seawater desalination.
However, achieving this goal requires precise control over the interlayer spacing of graphene to within one-tenth of a nanometer, a significant scientific hurdle. Professor Fang began tackling this challenge in 2008, dedicating his efforts to water research.
Historically, chemists discovered that graphene’s unique structure showcases a phenomenon involving π electrons, which interact strongly with cations like sodium ions, resulting in ion-π interactions. Yet, this interaction often goes unnoticed in aqueous solutions due to the presence of hydrated ions.
Recognizing the importance of ion-π interactions in solution, Professor Fang’s team applied statistical physics and combined it with quantum mechanical calculations. They developed computational software to propose that ions could be precisely used to control the interlayer spacing of the graphene membrane, facilitating ion sieving and seawater desalination. Successful experimental validation of this theory led to a publication in the prestigious journal Nature.
Building on this foundational research, the team has created a practical graphene composite seawater desalination membrane, which boasts a water flux approximately 15 times greater than that of Dow’s seawater desalination membrane, making it one of the most advanced desalination technologies available today. They have also developed the thermos-sized portable desalination device, which has been included in Shanghai’s green technology directory.
In addition to their contributions to desalination technology, Professor Fang’s team has made another significant discovery: they observed a unique two-dimensional crystal structure of calcium chloride on the surface of graphene. These calcium chloride crystals exhibit remarkable properties, including conductivity and room-temperature ferromagnetism. Notably, they possess both piezoelectric and metallic characteristics, suggesting promising applications in transistors, magnetic devices, conductive electrodes, as well as in hydrogen storage and catalysis.
Another key outcome of Professor Fang’s awarded project is the theoretical prediction of the intriguing phenomenon where “water droplets sit atop a water layer.” The research team designed a model using a solid plane with polarized charges, allowing them to control the lattice constants and charge magnitudes. This design led to the observation of structured water molecules forming droplets instead of spreading out, demonstrating the phenomenon.
Since the publication of their research paper in 2009, this prediction has been rapidly validated by multiple research groups, confirming the existence of such phenomena across various surfaces, including metals, minerals, and oxides. This advancement opens new design strategies for materials that resist contamination and reduce drag, potentially impacting fields such as anti-fouling coatings for ships and medical vascular stents.
“Our work over the years has primarily utilized theoretical physics methods, combined with statistical physics analysis and molecular dynamics simulations, to study the effects of ions on water behavior in various systems,” Professor Fang noted. “We have uncovered some universal patterns, and I am confident that many more discoveries await us as we continue to explore and apply our findings.”
