Modulation of Stainless-Steel Wire Sieve-Supported ZnO Nanorods for Optimal De-Ionized Water/Diesel Oil Separation

: ZnO nanorods (ZnONRs) were hydrothermally synthesized on stainless-steel wire (SSW) sieves of various mesh sizes at different Zn2+ concentrations of the growth solution, and then treated with stearic acid (SA) for a specific duration. Using these SSW sieve-supported ZnONRs, a mixture of de-ionized (DI) water and diesel oil was separated. It was found that the SA treatment dramatically diminished the quantity of surface hydroxyl groups attached to the top and upper portions of the ZnONRs, and thus significantly enhanced the hydrophobicity of the ZnONR-coated SSW sieves. The synthesis parameters remarkably affected the surface morphology and wettability of the ZnONRs on the SSWs, which in combination with the mesh size of the SSW sieve, influenced the contact angles (CA) of the ZnONR-coated SSW sieves and the separation efficiency for DI water and diesel oil. In each batch, the ZnONR-coated SSW sieves with mesh sizes of 300, 200, and 100 produced at Zn2+ concentrations of 125, 100, and 25 mM of the growth solution had the most desirable surface morphology, and were the most hydrophobic and oleophilic; further, they gave the optimal separation efficiencies of 93%, 95%, and 90% respectively. Thus, the ZnONR-coated SSW sieve with a mesh size of 200 prepared at Zn2+ concentration of 100 mM of the growth solution can be employed as an effective separator of water and diesel oil.