Bio-inspired fabrication of fire-retarding, magnetic-responsive, superhydrophobic sponges for oil and organics collection

Abstract In this study, durable superhydrophobic sponge with magnetic-responsive and fire-retarding was prepared. In the preparation process, polydopamine (PDA), layered double hydroxide (LDH), Fe3O4 nanoparticles and n-Octadecyl mercaptan (OM) acted as the “bio-glue”, fire retardant, magnetic materials and hydrophobic reagent, respectively. LDH and Fe3O4 nanoparticles were adhered on the skeleton surface of PU sponge via PDA to build micro/nano structure, and then the -NH2 of PDA could react with the -SH of OM (Michael addition reaction), which made the sponge repellent to water. The prepared sponge exhibited remarkable hydrophobicity (water contact angle = 163°)and highly oleophilic (oil contact angle = 0°). When used for absorbing oil and organics, the prepared sponge floated on the surface of oily wastewater, and it could be moved towards oil droplet under magnetic actuation. The as-prepared sponge could absorb various kinds of oils and organics up to 53.6 times of its own weight, and the absorbed oils could be collected through a simple squeezing process. The prepared sponge could be withstood at least 50 cycles of laundering without losing its magnetic properties and superhydrophobicity due to the viscidity of PDA and strong interaction between PDA and OM. In addition, it was difficult to ignite the prepared sponge in air after anchored LDH and Fe3O4 on the sponge skeleton surface. This might offer an environmentally friendly way to prepare “smart and safe” oil-recovery materials.