Environmentally friendly superhydrophobic osmanthus flowers for oil spill cleanup

Abstract

Herein, we found osmanthus flowers (osmamthus fragrans var. thunbergii) showing interesting wetting behaviors. Fresh flowers manifested high-adhesion hydrophobicity with the water contact angles (WCAs) of 128.6 ± 3.5°. Dry flowers exhibited low-adhesion superhydrophobicity (WCA = 158.3 ± 2.7°) and superoleophilicity with the oil contact angles (OCA) of 0°. When crushed osmanthus flowers into powders, strong water repellency and oil wetting were still found. Both of osmanthus flowers and powders displayed efficient oil absorption capacities (OACs), whereby osmathus powders showed high OACs for different organic solvents ranging 5.3 ± 2.2–27.3 ± 1.8 g/g. Moreover, flowers and powders samples were featured with the abilities of emulsion purification. Importantly, from experimental result analysis and theoretical derivations, we concluded that OACs were varied regardless of sample masses while increased almost linearly upon the product of densities and surface tensions (ρ × γ) of absorbed solvents. This research not only provides a new kind of low-cost, easy-to-access and environmentally friendly raw superwettable material applied for future oil cleanup but also will be advantageous for optimizing the selection of oil-absorbing materials for certain solvents.