Reverse osmosis is used worldwide to purify drinking water. It is deployed at extremely large scales in desalination plants and is a leading technology in potable water reuse, also called toilet-to-tap—a nickname that annoys scientists and engineers working on potable water reuse. Though existing reverse osmosis membranes remove salt and most contaminants, a few slip through, such as boron and N-nitrosodimethylamine (NDMA), a toxic byproduct of the chlorination used upstream to kill pathogens. To make a better membrane, a team from China’s State Key Laboratory of Pollution Control and Resource Reuse, the University of Hong Kong, and Vanderbilt University used nanoflakes of an amphiphilic metal-organic framework (MOF) to create a next-generation polyamide membrane. The MOF flakes line up on the interface between the water and hexane emulsion where amide polymerization takes places, regulating the heat and mass transfer associated with the reaction. In this microscope image, the researchers whipped the mixture into an emulsion to probe how the MOFs behave at the interface. The final result is a thin, crumpled membrane material that outperforms conventional membranes in removing salt, boron, and NDMA.
Credit: Zhiwei Wang, Shihong Lin, Sci. Adv. 2022, 10.1126/sciadv.abm4149
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