Atomic-layer-deposition-enabled nonwoven membranes with hierarchical ZnO nanostructures for switchable water/oil separations

Functional membranes with separation ability for water/oil mixtures based on contrasting wetting behavior have recently received significant attention in the application field of water contamination treatment. Herein, we demonstrated a surface functionalization method for cost-efficient nonwoven fabrics with no selectivity of water/oil mixture. This nonwoven membrane was fabricated by hydrothermal growth of ZnO hierarchical nanorods on the surface of atomic-layer-deposited ZnO ultrathin layer. Due to the ZnO nanostructure with roughened morphology and the amphiphilic nature of the nonwoven fabrics, the functionalized nonwoven membranes were endowed with both underwater oleophobicity and under oil hydrophobicity. Separation of any phase in the mixture of water and oil can be achieved simply by pre-wetting the nonwoven membrane surface with the heavier component. Driven by gravity solely, the as-prepared nonwoven membranes can efficiently and selectively separate water/oil mixtures with exceptional stability. These functionalized nonwoven membranes may find potential application against complex water/oil separation systems.