A Sponge-Type oil skimmer for highly efficient removal of floating Oils: Superabsorbent and oleophilic sponge with Nano-Scale interface roughness

[Display omitted] •The superabsorbent PU@PDA sponge is achieved by polymerization of dopamine.•Nano-roughness of sponge was induced through the self-polymerization of dopamine.•The interface roughness of sponge improved the absorption and wettability of the oil.•The PU@PDA Sponge oil skimmer showed high-efficiency floating oil removal ability.•The PU@PDA sponge skimmer maintained 98% oil absorption rate at 5,000 cycles. In an industrial environment, the contamination by oil has caused manufacturing processes and environmental problems. In this study, the modified polyurethane (PU@PDA) sponge with superabsorbent properties was produced by adjusting the nano-roughness on the surface of the polyurethane (PU) sponge by a simple polydopamine (PDA) self-polymerization method. Nano scale interface roughness which affected the wettability of the sponge was induced through a facile synthesis reaction in alkaline conditions. SEM images and AFM results were used to confirm whether the PDA was uniformly formed on the PU surface and roughness evaluation, and the oil absorption time of PU@PDA sponge was less than 1 s through the contact angle evaluation method of the oil droplet. An oil skimmer device was manufactured on its own to evaluate the floating oil removal rate and durability of sponges in practically applicable industrial environments, and in terms of efficiency, it was confirmed that the oil removal efficiency was 100 times higher than the rubber-type oil skimmer. In the repeated cycle oil removal efficiency experiment, the oil removal efficiency of 5760 (4 days, 1 rpm) and 11,502 (8 days, 1 rpm) times were maintained at 98 % and 82 %, respectively.