Fabrication of a Superamphiphilic SS-400 Oil Separator Surface Using a Ag-Doped ZnO Nanorod Coating

A simple fabrication technique is described for preparing Ag-doped ZnO nanorods using a rapid hydrothermal technique to create a superamphiphilic surface on SS-400 substrates. The high roughness resulting from Ag-doped ZnO nanorod surfaces is responsible for generating the superamphiphilic property of the SS-400 substrate. The fabricated surface shows contact angles (CAs) of almost 0 degrees for water and olive oil, resulting in complete spreading of water and oily liquids. The fabricated surface also exhibits excellent superamphiphilic properties after long-term storage, thermal, and mechanical testing. However, after modification with a low-surface-energy material (stearic acid), the fabricated surface exhibits superhydrophobic properties with water CAs of 158 degrees and sliding angles (SAs) of less than 5 degrees. We also applied our fabrication method to a helical-type oil separator. The oil separator, when treated with Ag-doped ZnO nanorods with a superamphiphilic surface, improved its oil separation efficiency and pressure drop compared with those of a commercial oil separator. Thus, our surface fabrication technique can be implemented easily to large-area, three-dimensional surfaces. Due to their ease and rapidity of manufacture and long-term wetting stability, these surfaces are potentially suitable for large-scale industrial applications in a variety of fields.