Indexed on: 27 Jan '17Published on: 27 Jan '17Published in: ACS Applied Materials & Interfaces
The rapid industrial growth has led to the large production of oily wastewater. Necessity to treat the oily wastewater is an inevitable challenge to manage the greater demand of clean water for rapidly growing population and economy. In the present work, we have developed a smart surface mesh with reversible wetting properties via a simple, ecofriendly and scalable approach for on demand oil-water separation. ZnO nanowires (NWs) obtained from chemical vapor deposition method were coated on a stainless steel (SS) mesh. The as-synthesized ZnO NWs coated mesh shows superhydrophilic/underwater superoleophobic behavior. This mesh works in "water-removing" mode, where the superhydrophilic as well as underwater superoleophobic nature allows the water to permeate easily through the mesh while preventing oil. The wetting property of ZnO NWs coated mesh can be switched easily from superhydrophilic to superhydrophobic state and vice versa by simply annealing it at 300°C alternatively under hydrogen and oxygen environment. The separation is solely driven by gravity. Thus, the reversible wettability of ZnO NWs provides a smart surface mesh which can be switched between "oil-removing" and "water-removing" modes. It was found that for more than 10 cycles of mesh reutilization in both modes alternatively, the separation efficiency of 99.9% stayed relatively invariant, indicating a prolonged anti-fouling property and excellent recyclability. This work provides a simple, fast, cost effective and on demand solution for issue of oily wastewater treatment and opens up new perspectives in the field of controllable oil-water separation.