Our surface and drinking water sources are increasingly threatened by the presence of organic micropollutants (OMPs). OMPs are small molecules (100-1000 Da) that originate from industrial, agricultural and pharmaceutical residues, and can cause long-term harm to humans and ecosystems. While OMPs can be removed from water with existing membrane technologies (e.g. reverse osmosis), these methods have significant limitations: they are energy-intensive and lead to problematic brine waste streams, due to their low water and salt permeability.
In this project we aim to solve these limitations by building charge-mosaic membranes; membranes with small (nm2) oppositely charged patches that allow coupled passage of negative and positive ions. This design, aimed at reducing salt retention, was conceived over 90 years ago, but was never realized in a scalable manner due to its challenging design. Here, we propose a simple and fully scalable approach to achieve such membranes, using polyelectrolyte multilayers (PEMs) of oppositely charged polymers. By adding charged nanoparticles to the final layer and then removing them by changing the pH, nanoscale charged patches are created in an oppositely charged surface. We will apply the same principle to create charged channels across the entire multilayer, by using sacrificial polymers. This approach, sacrificially patterned PEMs, allows exceptional control over the size and ratio of the charged patches. We will build these charge-mosaic membranes using ultrathin, ultradense layers in an asymmetric PEM approach to achieve a very high (> 99%) retention of OMPs and a high water permeability.
Combined with state-of-the-art modelling, this project will also provide new fundamental insights into membrane mass transport. Moreover, the project will directly lead to membranes with unique separation properties, allowing the design of completely new processes to effectively remove OMPs from waste water and drinking water.
