Lignocellulose and polydopamine composite superhydrophobic and photothermal membrane: A green innovative solution for oil/water separation and high-viscosity oil adsorption

A superhydrophobic CNF/PDA composite membrane has been developed to revolutionize oily wastewater treatment for achieving high efficiency, cost-effectiveness, and environmental sustainability. Inspired by the adhesive properties of mussels and the self-cleaning mechanism of lotus leaves, this innovative material is fabricated through a novel lyophilization and spray modification process using cellulose nanofibers (CNF), dopamine hydrochloride (DA), and octadecylamine (ODA). The membrane is synthesized via an aerobic, weakly alkaline self-polymerization process, which facilitates the formation of robust covalent and non-covalent bonds between the catecholamine structure of DA and CNF. ODA is integrated through hydrogen bonding and Schiff base reactions with polydopamine (PDA), enhancing structural stability. The resulting membrane demonstrates a tensile strength of 2.9 MPa, alongside exceptional separation efficiency (98.5 %) and flux rates (3745 L·m −2 ·h −1 ). Even after five consecutive water-in-oil (W/O) emulsion separation cycles, a separation efficiency exceeding 91.8 % is maintained, with hydrophobicity and structural integrity preserved. Durability tests confirm its robustness, with 98.5 % of initial capacity retained after ten adsorption-desorption cycles. The membrane's porous architecture and photothermal brown-black hue synergistically boost light-to-heat conversion, facilitating swift thermal response and efficient high-viscosity oil uptake. This demonstrates viable applications as a sustainable solution for oily wastewater treatment, promoting greener industrial application.