The increasing global need for potable water is critical. While water is available in ample quantities on earth, the vast majority (>98%) is in undrinkable form (e.g., seawater, brackish water, or sewage water). There is a need for new materials and processes that can efficiently purify water by removing debris, biological matter, organic and inorganic impurities, and various salts. The most challenging of these impurities are salt and small neutral organic molecules, because their hydrodynamic size is most comparable to water molecules, complicating size-based separations. Porous materials, crystalline materials are highly resistant to high temperatures and pressure but, these properties are absent in state-of-the-art polymeric membranes, which results in membrane damage or degradation over time and chemical compromise (for example, reported damage after exposure to chlorine).
To address these issues, the innovation puts forward 2D bio-inspired membranes that selectively exclude ions and neutral species but allow rapid water transport so that water purification is energy efficient.
NU researchers have developed a bio-inspired membrane that integrates the properties of crystalline 2D sheets to the programmable use of biomolecules as selectivity-tuning agents. The bio-inspired membrane was prepared by designing cationic and anionic peptides that can self-assemble to create positively and negatively charged surfaces that are bonded together via strong electrostatic interaction to form a layer-by-layer assembly. This design overcomes the inevitable hydration force. The absorbed molecules will be transported across the membrane, resulting in an increase in water driving force. Hence, this design of the crystalline membrane provides an effective filter for the removal of difficult impurities such as salt and small organic molecules.