One-step fabrication of coating-free mesh with underwater superoleophobicity for highly efficient oil/water separation

Robustly superhydrophilic-underwater superoleophobic stainless steel meshes were fabricated via a simple and cost-effective one-step etching route. The obtained meshes show good underwater superoleophobicity not only in pure water but also in corrosive (acidic, alkaline and saline) aqueous solutions. Such special wettability allows water to permeate through the mesh while the oils are repelled on the mesh surface completely. The mesh can separate a series of oil/water mixtures under the gravity drive with high separation efficiency. Importantly, the etched meshes are capable of separating oil from acidic, alkaline and saline aqueous solutions, and the separation efficiency can reach above 94.3% after repeatedly separating toluene/corrosive water mixture for 16 cycles. In addition, the resulting mesh still possesses high underwater superoleophobicity with oil contact angle of 145 after the abrasion of 100 cycles. Thus, the etched mesh may be a potential candidate for practical oil/water separation applications.