Mussel-inspired pH-responsive copper foam with switchable wettability for bidirectional oil-water separation

Stimuli-responsive materials with switchable wettability for bidirectional oil-water separation show great potential in practical applications. Inspired by mussels, we use dopamine as an anchor molecule to construct a polydopamine (PDA) coating on the surface of copper foam (CF). Silver particles are deposited on the PDA coated surface to construct a multiscale composite structure, and the long-chain alkylthiol with carboxyl and methyl groups at the end is subsequently self-assembled to the modified copper foam surface. The as-modified copper foam has unique pH responsiveness, that is, the water contact angle (WCA) is measured to be about 140 degrees under acidic and neutral conditions, while alkaline conditions radically change the surface property from super hydrophobic to superhydrophilic due to the measured WCA turning to 0 degrees. It can be used efficiently for the bidirectional separation of an oil-water mixture, e.g., the separation efficiency of a 1,2-dichloroethane/water mixture can reach as high as 98.2%. Besides, it maintains 98% separation efficiency and stable wettability for an octane/water mixture, together with excellent mechanical durability; the WCA of the surface maintains at about 130 degrees after ten wear cycles.

Automated summary

The study has developed a material with pH responsiveness through dopamine coating and silver particle construction, which can efficiently achieve bidirectional oil-water separation.