Track membranes excel in both selectivity and permeability
Ionic sieving with membranes has become the most promising way to achieve large-scale and energy efficient water purification and chemical separations. To fulfill its potential in real applications, it has been a long-standing goal to overcome two great hurdles: permeability/selectivity trade-offs and lack of scalability.
Using the high-energy heavy ion irradiation with HIRFL, Feng Liu and Yugang Wang research group at Peking University succeeded in fabricating nanoporous polymeric membranes with unprecedentedly high permeability and selectivity of cations, outperforming all the other reported membranes in fast ion sieving (Figure 1). The newly developed fabrication process, namely, the track-UV technique, is highly reproducible, and potentially scalable and efficient in industrial-scale production. In this study, they tested 2-μm-thick PET Lumirror？ films with stronger UV absorption and higher irradiation resistance. The nanoporous Lumirror？ membranes show highly increased transport rates of alkali metal ions by more than 3 orders of magnitude to about 10 mol h-1 m-2 without significantly compromising the ionic selectivity (Figure 1.a). Furthermore, their study reveals the underlying mechanism of the excellent performance of the membranes using molecular dynamics (MD) simulations with a polymeric nanopore model. This more realistic polymeric nanopore model recapitulates the experimental results in the MD simulations, and suggests that ionic selectivity stems from a new transport mechanism operational in an unexplored regime as the sizes of the channels approach the molecular scale (Figure 2).
This work was published in Nature Communications | (2018) 9:569. The article can be linked as follows: https://www.nature.com/articles/s41467-018-02941-6.
Fig.1 Transport rates and selectivity
Fig.2 Simulated ionic transport phenomena