Modified PU sponge for water purification

In this paper, poly-dopamine modified PU sponges were applied for water purification after being modified by different chemicals. Ag NPs were firstly in situ reduced on a polydopamine–modified polyurethane (PU) sponge under mild conditions (PU–PDA–Ag). Ag NPs could be uniformly dispersed and securely immobilized on the skeleton of PU sponge, which efficiently maintained the catalytic activity and stability. The soluble organic pollutants could be catalytically reduced by the PU–PDA–Ag sponge with the appearance of NaBH4. The target organic pollutants, including methylene blue (MB), methyl orange (MO), rhodamine B (RhB), and 4–nitrophenol (4–NP) could be completely reduced. In addition, the PU–PDA–Ag sponge was recycled for five cycles without a notable decrease in catalytic activity for the reduction of MB, exhibiting excellent reusability. To reverse the surface wetting characteristics for oil–water separation, the PU–PDA–Ag sponge was covalently grafted with mercaptan (dodecanethiol) to form a superhydrophobic/superoleophilic sponge (WCA=157.5°, OCA=0 °). The superhydrophobic/superoleophilic sponge (PU–PDA–Ag–SH) presented excellent sorption capacity in the range of 21.6–101.2 g/g for various insoluble oils and organic solvents and also showed superior reusability, which could be reused for 20 cycles without a significant decrease in sorption capacity. The PU–PDA–Ag–SH also provided the capability of continuous oil–water separation for both light oils and heavy oils with separation efficiency as high as 98.35% for diesel and 99.38% for chloroform, respectively.