Fabrication and characterization of fluffy mono-coated copper meshes and their applications for oil/water separation

Abstract The textured-metallic meshes with superhydrophilic-superoleophobic and superhydrophobic- superoleophilic wetting have captured a widespread attention especially for oil/water separation. In particular, the design of gravity-driven oil/water separator needs further attention considering the effective mesh-area at which water-barrier formation can be avoided. Herein, the fluffy mono-coating (FMC), a smart single layer of iron palmitate resembling cotton-in-open-bolls, is electrochemically grown on three copper meshes (FMC-Ms) varying in mesh-pore sizes of ~150 µm (FMC-M1), ~250 µm (FMC-M2) and ~300 µm (FMC-M3). At the effective mesh-areas of FMC-Ms, separation efficiency varies between 98.1% and 99.6%, while separation flux substantially varies relying on the oil viscosity and mesh-pore size. For low-viscosity heptane oil, separation flux is reported to be 62,483 Lm−2h−1, 26,437 Lm−2h−1 and 15,390 Lm−2h−1, while it is 971 Lm−2h−1, 740 Lm−2h−1 and 322 Lm−2h−1 for high-viscosity pump oil, on FMC-M3, FMC-M2 and FMC-M1, respectively. In addition, the evaporative contact line dynamics of water is studied together with the derived depinning forces, particularly advancing the physical understanding of water adhesion and ease of oil-evaporation (transient self-recovery) from FMC-Ms. In summary, high separation efficiency, a wide range of separation flux, improved intrusion pressure, strong cyclic durability and promising anti-fouling (salt-fouling and oil-fouling) features are the salient traits of the FMC-Ms.