High capacity oil absorbent wood prepared through eco-friendly deep eutectic solvent delignification

Frequent occurrence of oil spill accidents and heavy discharge of oily wastewater lead to serious environmental pollution. The sustainable utilization of natural materials offers non-toxic and renewable methods for oil waste adsorption. A new oil absorbent wood material was therefore developed using the deep eutectic solvent (DES) treatment and subsequently hexadecyltrimethoxysilane (HDTMS) hydrophobic coating. Compared to the conventional chemical approach using NaOH-Na2SO3 and NaClO2, the DES delignification was more favorable towards remaining original wood structures attributing to its dissolving mechanism avoiding chemical hydrolysis. Chemical analysis showed that more residual lignin and hemicellulose remained in the DES-delignified wood compared to those treated by conventional chemical approaches. The specific surface area increased approximately 19-fold from 1.3 to 24.9 m2 g−1 after the DES delignification of wood. The DES-delignified wood exhibited excellent mechanical compressibility, i.e., 97% height retention after 100 compression-releasing cycles at 90% strain, which was beneficial to the oil absorption and squeeze application. The DES-delignified wood was then coated by HDTMS to be endowed superhydrophobic surfaces for oil absorption. The developed wood showed high capacity to absorb various types of oils, recording 37 g−1 for absorbing silicone, which is highly competitive compared to current available materials and techniques. This novel oil absorbent wood can be produced using abundantly available wood resource and is eco-friendly in production due to the employ of re-usable DES. This sustainable novel oil-absorber may be widely applicable for cleaning oily wastewater.