One-step foam assisted synthesis of robust superhydrophobic lignin-based magnetic foams for highly efficient oil-water separation and rapid solar-driven heavy oil removal

Taking effective measures to remove oil and organic pollutants from water has become a top priority. In this study, we developed a novel superhydrophobic and magnetic lignin-based polyurethane foam for highly efficient adsorption of organic pollutants and removal of viscous crude oil from water. The superhydrophobic bio-based magnetic foam was prepared by the addition of Fe 3 O 4 nanoparticles during the foaming process followed by the immersion in an octadecyltrimethoxysilane (OTMS) solution. After modification by OTMS, the water contact angle (WCA) of the foam adsorbent was increased by 37.1°, exhibiting a high WCA of 156°. Fe 3 O 4 nanoparticles endowed the foam with excellent photo-thermal performance, allowing the efficient adsorption of both crude oil and a wide range of organic solvents. The foam adsorbent had a high adsorption capacity up to 18.8 times of its own weight. The bio-based adsorbent could still retain a high adsorption capacity after over ten cycles. The magnetic property facilitated control and recycling of the foam adsorbent by using a magnetic field. Moreover, the bio-based foam adsorbent was fully degraded in a methanol/sodium hydroxide solution (0.5 mol/L) at 60 °C after 8 h. The outstanding mechanical stability, reusability, and environmental friendliness make these bio-based foam adsorbent highly promising for cleaning up pollutions in water.