Fast solar-heating sponge with TEMPO-modified PDA coating for rapid recovery of highly-viscous oil on water

A novel solar-heating sponge with high photothermal conversion efficiency was prepared for rapid cleanup of offshore oil spills. The sponge was fabricated by coating a modified polydopamine (PDA) layer on a thermal conductive sponge containing nanotubes (CNTs), followed by a polydimethylsiloxane (PDMS) layer. The modified PDA layer was copolymerized using 2,2,6,6- tetramethylpiperidine 1-oxyl free radical (TEMPO) and dopamine. The resulting sponge exhibits a UV-Vis sunlight adsorption efficiency as high as 93.0 %, and can be heated to 92 ℃ within 90 s under 1 sun irradiation. The adsorption capacity of the sponge for crude oil reached 733 wt%. Additionally, the high elasticity and stability endows the sponge excellent regenerability. Its adsorption capacity, water contact angle and surface morphology all remain unchanged after 10 adsorption-desorption cycles. For continuous oil spill remediation, the crude oil cleaning rate can attain 30 g/(g·min). The high photothermal efficiency, rapid adsorption efficiency and excellent regenerability suggest the sponge to be a potential candidate for treatment of viscous oil spills. • PDA is modified by TEMPO to improve the photothermal property. • The temperature rises to 92 °C within 90 s under 1 sun irradiation. • The sponge can be 100 % regenerated after desorption. • The synergistic effect of PDMS, TEMPO-PDA and CNTs contributes to the fast solar-heating.