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Bio-inspired gas-entrapping membranes (GEMs) derived from common water-wet materials for green desalination
- Das, Ratul, Arunachalam, Sankara, Ahmad, Zain, Manalastas, Edelberto, Mishra, Himanshu
- Journal of membrane science 2019 v.588 pp. 117185
- Collembola, Halobates, air, artificial membranes, biomimetics, desalination, distillation, hairs, heat, insect cuticle, perfluorocarbons, polymethylmethacrylate, renewable energy sources, silica, sodium chloride, vapors, water supply
- Widespread stress on global water supplies compels the need for low-cost and sustainable desalination processes. In this regard, desalination through membrane distillation (MD) can harness waste-grade heat or renewable energy. So far, the membranes for MD have been exclusively derived from intrinsically water-repellant materials - mostly perfluorocarbons. However, perfluorocarbons are limiting in terms of operational conditions, and they also introduce economic and environmental concerns. The development of perfluorocarbon-free MD membranes would likely address those challenges. Here, we report on the proof-of-concept for biomimetic gas-entrapping membranes (GEMs) for MD derived from silica and poly(methyl methacrylate) (PMMA) that are water-wet materials. We drew inspiration for our GEM design from the cuticles of springtails and hairs of Halobates germanus, both of which exhibit mushroom-shaped (or reentrant) features. Accordingly, our GEMs comprise arrays of microscale cylindrical pores with reentrant inlets and outlets that can robustly entrap air on submersion in water. Our PMMA-GEMs yielded a vapor flux of J≈ 1 L-m−2-h−1 while separating a solution of ∼0.6 M NaCl at 333 K from deionized water at 288 K under a cross-flow configuration. To our knowledge, this is the first-ever demonstration of MD membranes derived from intrinsically water-wet materials, and these findings suggest that the rational design of membranes towards greener and cheaper desalination processes is possible.