High-strength and recyclable superhydrophobic magnetic lignin modified polyurethane sponge for efficient oil-water separation

Oil leakage has always been of great concern to researchers. However, developing materials with high oil selectivity and simple recovery capabilities still requires breakthroughs. Here, a novel lignin-based superhydrophobic magnetic polyurethane (PU) sponge was prepared through simple soaking a superhydrophobic magnetic coating using phosphorylated alkaline lignin (PL) as a template for in-situ formation of iron oxides, PDMS and MTMS as hydrophobic modifiers, PDMS as a binder, and PU sponges with excellent mechanical properties as the representative porous material. In the system, PL is prepared by grafting phosphate groups on the surface of alkaline lignin (AL). After adding the phosphate group, PL will be uniformly dispersed in the system and can adsorb Fe 2+ and Fe 3+ to generate Fe 3 O 4 particles that is uniformly dispersed and does not affect the pore structure. PL and Fe 3 O 4 together as rough structures, under the synergistic effect of silane long chain formed by the hydrolysis of PDMS and MTMS achieve superhydrophobic properties, so as to provide a high oil selectivity of the system. Moreover, the uniformly dispersed Fe 3 O 4 enables the porous material to obtain magnetic properties that are easily recovered by magnets after oil-water separation. The prepared modified PL@Fe 3 O 4 composite sponge shows excellent superhydrophobic (water contact angle of 152.2°), oil absorption (7.95–20.48 g/g for various oils or organics) and magnetic properties (2.87 emu/g). This strategy opens up new possibilities for improving the utilization rate of lignin and porous materials.