Superhydrophobic and photothermal sponge for effective oil/water separation and solar-assisted recovery of viscous oil

With the occurrence of offshore oil spills, the recovery of viscous oil continues to be a significant issue. The multi-functional sponge with superhydrophobic, absorption of high viscosity oil is an effective approach to settle this problem. In this work, the melamine-formaldehyde (MF) sponge was the backbone and doped with polydopamine (PDA) to mimic mussels. Subsequently, candle soot nanoparticles (CS) and polydimethylsiloxane (PDMS) were applied to modify the MF sponge into a superhydrophobic sponge (P-CS-PDA@MF) (WCA = 153.56°). The P-CS-PDA@MF sponge showed good absorption properties for many oils and organic solvents (33.87–78.90 times of its own weight). In addition, the P-CS-PDA@MF sponge also showed outstanding chemical stability, low density (0.013 g/cm 3 ), emulsion-breaking ability and flame retardancy. More interestingly, the P-CS-PDA@MF sponge showed superior photothermal conversion capability, the temperature of it increased to approximately 91°C within 100 s under simulated sunlight from room temperature (about 25°C), and the sorption capacity of viscous oils was significantly increased. Moreover, the P-CS-PDA@MF sponge exhibited a high efficiency (over 97%) for separating viscous oils/water mixtures with the aid of sunlight. This versatile and efficient multifunctional P-CS-PDA@MF sponge via a simple and low-cost way shows promising prospect in oily wastewater treatment and water ecosystem remediation.