Researchers from the Technion and the University of Texas at Austin have mapped wet-state membranes for the first time using TEM cryo-tomography, revealing a volume expansion of approximately 30% under water flow, offering insights for designing more efficient membranes; the study was selected for the ACS Nano cover
Joint research conducted at the Technion and the University of Texas at Austin reveals new insights into the structure of membranes used for water desalination. The Journal DHW Nano, in which the work was published, chose the study for its cover article. Unlike previous studies, which focused on characterizing the membrane in its dry state, the current study also characterized the membrane in its wet state and discovered dramatic differences between the two states.These differences affect membrane function and therefore understanding them is very important for improving membranes intended for desalination and purification.
The research was led by Prof. Tamar Segal-Peretz from the Wolfson Faculty of Chemical Engineering, Prof. Guy Ramon from the Faculty of Civil and Environmental Engineering, and Prof. Manish Kumar from the University of Texas at Austin, along with doctoral student Chenhao Yao from the University of Texas at Austin and Dr. Adi Ben-Zvi (Menachem), who conducted the research while she was a doctoral student in the Nanoscience and Technology Program at the Technion and is currently a postdoctoral fellow at Rice University in Houston, Texas.
According to the World Health Organization, about a quarter of the world's population suffers from a shortage of drinking water, and indeed, potable water is included among the 17 UN Sustainable Development Goals. In light of this, the importance of desalination and water reclamation technologies is clear - especially in arid regions like Israel, which has become a powerhouse in these areas. Today, the five desalination plants operating in Israel provide about 70% of domestic water consumption. Israel also stands out in the field of water reclamation: about 85% of wastewater is treated and used for irrigation.
The most common technology for desalination today is Reverse Osmosis. In a simplified description, this is a process in which water passes through a membrane, but salts are unable to pass through it. Osmosis is a natural phenomenon in which water moves from a dilute solution to a more concentrated solution through a membrane, until concentrations are equalized. In contrast, in reverse osmosis, the direction of flow is reversed and water moves – through an investment of energy – from the concentrated solution (e.g. seawater) to the dilute solution (desalinated water). This process allows for the production of freshwater in significant quantities from unconventional water sources such as seawater, brackish water and wastewater. Although reverse osmosis membranes are a central tool in water desalination, there are still gaps in knowledge regarding the relationship between membrane structure and its function. The reason for this is that accurate mapping of the membrane under different conditions is lacking. Since these are very thin membranes (approximately 200 nanometers) and have a complex three-dimensional shape, characterization using previous methods, such as atomic force microscopy (AFM), does not provide a complete understanding of the complex structure.
In a study led by researchers from the Technion and Texas, a first-of-its-kind, high-resolution mapping of The three-dimensional morphology of the membrane After exposure to water – that is, under conditions close to the actual conditions in which reverse osmosis occurs. The three-dimensional characterization was performed using transmission electron microscopy tomography, when the membrane is saturated with water and frozen (cryogenic-TEM tomography). The researchers found that The structure of the membrane changes dramatically when water passes through it., And its volume increased by about 30% or more.Since membranes have so far been characterized only in their dry state, this is a dramatic discovery both scientifically and in terms of its applied implications. The new nanometric characterization is expected to significantly improve the design and performance of future membranes, thus optimizing the technologies used for desalination and water recovery.
The research was supported by the National Science Foundation (Israel), the WoodNext Foundation, the University of Texas Startup Fund, the Ministry of Energy and Infrastructure (Israel), and the Department of Energy (USA). The collaboration between the Technion and the University of Austin was supported by the Rakhmimov Fellowship from the US-Israel Binational Science Foundation (BSF), which helped fund Dr. Ben-Zvi's two-month visit to the University of Texas at Austin.
for the article in the journal DHW Nano click here
More of the topic in Hayadan:
