A water solvent-assisted condensation polymerization strategy of superhydrophobic lignocellulosic fibers for efficient oil/water separation

Superhydrophobic surfaces have received increasing attention in a broad range of important fields including oily wastewater treatment and oil collection in spills accidents. However, the preparation of such superhydrophobic surfaces has been proven to be energy-intensive and these surfaces are non-degradable. Herein, a naturally abundant fibrous substrate (i.e., lignocellulosic fibers and cotton fabric), mainly composed of cellulose, combining inexpensive bulk chemicals (melamine, formaldehyde, and octadecylamine) was cleverly designed and strategically exploited for the low-cost, easy scale-up, and eco-friendly superhydrophobic surface. These superhydrophobic surfaces can be used to clean different forms of oil-contaminations, including floating light-oil and sedimentary heavy-oil (with an efficiency above 700 wt% for various oils). This study showed that the superhydrophobic surfaces created via a scalable and green water solvent-assisted condensation reaction can achieve high water repellency both in air and in oil, and exhibited a single efficient avenue for gravity-driven active filtration of oil. The superhydrophobicity of the octadecylamine-melamine-formaldehyde (OMF) lignocellulosic fibers remained unperturbed even after long-term exposure to UV radiation (at both 254 nm and 365 nm) for 168 h. The OMF lignocellulosic fibers showed good antifouling properties and maintained high separation efficiency (>95%) as well as a high water contact angle (>150 degrees) after being repeatedly used for 70 cycles. Furthermore, this strategy exhibited good versatility for superhydrophobic cotton fabrics with high contact angles (>160 degrees) and high water/oil separation efficiency (96%).