A facile two-step method to construct environmental-friendly Janus coconut wood membrane for oil/water separation

The Janus structure and the super hydrophilicity of cellulose inspired to develop of low-cost and environmentally friendly Janus membrane materials with opposite wetting behavior for unidirectional water/oil transport and selective water/oil separation. However, it remains a challenge to prepare pollution-free, fluoride-free, low-cost Janus membranes in a simple way. A facile two-step top-down approach is utilized to prepare the Janus coconut wood (JCW) membrane using natural coconut wood in the transverse direction as raw material. The lignin and hemicellulose were removed from the coconut wood to prepare super-hydrophilic coconut wood (SCW). The SCW was then sprayed with hydrophobic silica gel to form a super-hydrophobic surface on one side which the water contact angle reached 153.4°. It was observed that the Janus membrane maintained chemical stability in highly saline and varied pH conditions, as well as at a long friction distance. Meanwhile, Janus coconut wood membrane oil/water separation devices readily achieve on-demand unidirectional oil/water transportation due to their superior separation efficiency of over 98 % and separation flux of over 4125 L/m 2 ·h. The Janus coconut wood membrane provides a practical and effective solution for separating the oil/water mixture.