Toward durable and robust superhydrophobic cotton fabric through hydrothermal growth of ZnO for oil/water separation

In this study, an eco-friendly superhydrophobic cotton fabric (CF) with water contact angle of 155° was fabricated via a facile two-step approach: imparting surface roughness through hydrothermal growth of ZnO particles, and using stearic acid to create a low-energy surface. ZnO prepared by hydrothermal reaction was in a rod-like shape and had nano- or micro-scale sizes. It was located on the surface in loose aggregates. After modification with stearic acid, the aggregate structure of ZnO particles was changed from loose packing to compact packing. The superhydrophobic CF could be wetted by oil but could not be wetted by water, showing excellent oil/water separation performance. The superhydrophobic CF was able to absorb oils selectively from their mixtures with water and could be used as a filtering membrane to separate oil/water mixtures directly with separation efficiency and oil flux of 96–99% and 2000–9000 L m−2 h−1, respectively, depending on the intrinsic property of the oils. In addition, the superhydrophobic CF showed excellent mechanical robustness and environmental durability with water contact angle almost remaining unchanged after exposure to sandpaper abrasion, ultrasonication, boiling water treatment and organic solvents erosion. With excellent robustness and durability, the superhydrophobic CF exhibits great potential in oil/water separation even under some harsh conditions.