Multifunctional superhydrophobic sponge for efficiently separating various oil-water mixtures from immiscible to emulsions and in-situ recovering crude oil

Effectively separating wide types oil-water mixtures from immiscible to emulsions and in-situ recovering viscous crude oil is an urgent issue in alleviating water pollution and recycling oils. We developed a composite sponge of Cu-HHTP/Fe/PDMS@sponge with superhydrophobicity, excellent photothermal conversion ability and stability for multi-type oils separation from water environments. For light oil-water mixtures, the sponge showed super separation efficiency up to 99.95 % and reusability in the long-term; for oil-in-water emulsion, the separation efficiency was as high as 99.49 %; for recovery of viscous crude oil from water, the absorption capacity of the sponge reached 70 g/g and the continuous absorption rate was up to 6.56 g/min. After soaked in harsh chemical solutions and 500-cycle compression, the sponge still exhibited excellent flexibility and recoverability in viscous oil. The excellent performances of the multifunctional sponge were due to the construction of micro/nano-scale hierarchical structures by PDA and Cu-HHTP, protected with PDMS coating to improve both the hydrophobicity and stability. The introduction of Fe 3 O 4 with Cu-HHTP strengthened the photothermal conversion efficiency with the sponge surface temperature rapidly increased from room temperature to 102.4 °C under simulated sunlight exposure (1 kW/m 2 ), and resulted in the sponge can be remote-controlled magnetically. This simultaneous, fast and continuous oil-water separation and adsorption processes can be readily and widely applied for oily water purification and oil-spill cleanup.