Intelligent sponge with reversibly tunable super-wettability: robust for effective oil-water separation as both the absorber and filter tolerate fouling and harsh environments

We fabricate an intelligent and robust sponge by a one-step and low-cost ultrasonic-assisted dip coating (UADC) method, which involves the modification of the commercial sponge with TiO2 nanoparticles and a low-surface-energy compound (octadecanoic acid). The as-prepared sponge shows intelligent reversibly tunable super-wettability and exhibits robustness for effective oil-water separation. It can act as both the absorber and filter for the highly efficient separation of oil-water mixtures under different super-wettability conditions. More importantly, it has remarkably high chemical stability, which can separate oil-water mixtures in the extremely high acidic and alkaline environments as well as the extremely high salt concentration of seawater (such as 10 M H2SO4 and NaOH, and saturated NaCl media). Meanwhile, the as-prepared sponge has excellent antifouling ability, which shows self-cleaning performance during multiple fouling cycles. These extraordinary properties suggest that the as-prepared sponge will be a promising candidate for large-scale oil-water separation.