Recyclable, Fire-Resistant, Superhydrophobic, and Magnetic Paper Based on Ultralong Hydroxyapatite Nanowires for Continuous Oil/Water Separation and Oil Collection

The frequent occurrence of oil spilling and industrial oily wastewater have serious negative effects on the marine ecosystem and human health. For this reason, high performance, effective, and continuous oil adsorption materials are highly desirable. Herein, a new kind of recyclable, magnetic, fire-retardant, and superhydrophobic large-sized paper based on environmental friendly inorganic ultralong hydroxyapatite nanowires is reported. The ultralong hydroxyapatite nanowires not only act as building blocks for binding magnetic nanoparticles and coating a polydimethylsiloxane layer to form the free-standing composite paper but also endow the paper with high thermal stability, excellent fire resistance, porous structure, and high permeation flux. Moreover, the scaled-up production of ultralong hydroxyapatite nanowires and a large-sized composite paper has been demonstrated. The as-prepared composite paper exhibits a high separation selectivity (>99.0%), high permeation flux (2924.3 L m(-2) h(-1)), and good recycling ability (at least 10 times). More importantly, a mini-boat made from the composite paper acting as an oil-collecting device is fabricated for continuous oil collection. The mini-boat can be magnetically driven to the oil-polluted region, and the selective collection, convenient transportation, and recovery of oil from water are achieved. The oil-collecting device shows a high separation efficiency (>99.2%) and good reusability (at least 10 times). The present work may inspire the development and application of high-performance paper-based oil-collecting devices for continuous oil/water separation and oily contaminant collection in the field of oily wastewater treatment.