Facile preparation of fluorine-free superhydrophobic/superoleophilic paper via layer-by-layer deposition for self-cleaning and oil/water separation

Abstract Oil/water separation is highly desired due to increasing industrial oily wastewater and frequent oil spill accidents. Here, superhydrophobic/superoleophilic paper was successfully fabricated by the combination of layer-by-layer (LBL) deposition of chitosan (CS) and hexadecyltrimethoxysilane (HMTS)- g -TiO 2 on paper surface and subsequent heat treatment. The formation of CS/HTMS- g -TiO 2 multilayers on modified papers was characterized. The wettability and physical strength of the modified papers were also examined. The paper modified with (CS/HTMS- g -TiO 2 ) 20 multilayers followed by heat treatment showed superhydrophobicity with a water contact angle of 167.4° and superoleophilicity with an oil contact angle of 0°. This paper had comparable tensile strength to that of original paper and excellent self-cleaning performance. The as-prepared paper could also effectively separate both immiscible oil–water mixtures and water-in-oil emulsions solely driven by gravity. The obtained paper exhibited stable recyclability, high environmental and mechanical durability. Therefore, this LBL-modified paper could be useful for oil spill cleanup and industrial oily wastewater treatment. Graphical abstract