Materials
with special wettability have drawn considerable attention
especially in the practical application for the separation and recovery
of the oily wastewater, whereas there still remain challenges of the
high-cost materials, significant time, and complicated production
equipment. Here, a simple method to fabricate the underwater superoleophobic
and underoil superhydrophobic brass mesh via the nanosecond laser
ablation is reported for the first time, which provided the micro-/nanoscale
hierarchical structures. This mesh is superhydrophilic and superoleophilic
in air but superoleophobic under water and superhydrophobic under
oil. On the basis of the special wettability of the as-fabricated
mesh, we demonstrate a proof of the light or heavy oil/water separation,
and the excellent separation efficiencies (>96%) and the superior
water/oil breakthrough pressure coupled with the high water/oil flux
are achieved. Moreover, the nanosecond laser technique is simple and
economical, and it is advisable for the large-area and mass fabrication
of the underwater superoleophobic and underoil superhydrophobic mesh
in the large-scale oil/water separation.