Metaplexis japonica seed hair fiber: a hydrophobic natural fiber with robust oil–water separation properties

Natural fiber materials exhibit numerous advantages in the fields of oil absorption and oil–water separation owing to their abundant resources, low-cost, renewable and degradable characteristics. Herein, metaplexis japonica seed hair fiber (Mj-fiber), a hydrophobic natural fiber, is proposed as a promising candidate of oil-absorbing and oil–water separation fiber materials with excellent features such as surface superhydrophobicity, high hollow and cross-section heteromorphy. In particular, the oil-absorbing and oil–water separation abilities of such fibers are investigated for the first time. Some featured critical parameters, such as the surface static contact angle and spreading wetting process, oil absorption and oil–water separation performance of fiber assembly are systematically clarified. Mj-fibers possess outstanding superhydrophobic properties with remarkable static contact angle of 151.12°, whereas excellent lipophilicity with static contact angle of 0° against vegetable oil, motor oil and diesel oil. Mj-fibers also have good sorption capacities for vegetable oil, motor oil and diesel oil with 81.52, 77.62 and 57.22 g/g respectively, and oil retention capacities after 12 h with 79.1%, 75.4% and 72.0% respectively. More importantly, Mj-fibers as the filters exhibit an effective oil–water separation performance with high separation efficiency of 98% after four cycles, demonstrating its prominent reusability. Therefore, this work points out a new pathway of bio-based oil absorption material for water pollution caused by oil spill and other accidents with economical, environment-friendly and efficient solution.