Sustainable superhydrophobic lignin-based polyurethane foam: an innovative solution for oil pollutant adsorption

Green, efficient treatment of crude oil spills and oil pollutants is a global challenge, with adsorption technology favored for its efficiency and low environmental impact. The development of an environmentally friendly adsorbent with high hydrophobicity, excellent adsorption performance, and degradability is crucial to overcoming the limitations of petroleum-based adsorbents. Here, a lignin-based polyurethane foam (LPUF) with superhydrophobic and photothermal oil-absorbing properties was fabricated by incorporating octadecyltrimethoxysilane into the foam system. The modified foam showed a 151.4° water contact angle, as long-chain alkyl groups reduced surface energy, giving it superhydrophobicity. The foam adsorbent exhibited remarkable adsorption performance for a variety of organic solvents, achieving a maximum adsorption capacity of 20 g g^-1 and an oil-water separation efficiency exceeding 97%. Due to its outstanding elastic recovery properties, the foam exhibited only a 1.5% reduction in adsorption capacity after 10 adsorption-desorption cycles, indicating its strong potential for repeated adsorption and recovery. Under 1 kW m^-2 sunlight intensity, the surface temperature of the foam adsorbent rose to 79.7 °C within 350 seconds. The excellent photothermal conversion properties of the foam significantly reduced the viscosity of the surface crude oil, thereby increasing the adsorption rate. In addition, the modified foam adsorbent also demonstrated self-cleaning properties and could be completely degraded after 5 hours of treatment in an alkaline solution. The developed LPUF adsorbent exhibited superior hydrophobicity and oil-water separation capabilities, highlighting its potential for efficient oil pollutant removal, while also offering new avenues for the high-value utilization of renewable resources.