Flexible Janus wood membrane with asymmetric wettability for high-efficient switchable oil/water emulsion separation

Wenbo Che; Lingyue Zhou; Qiaoru Zhou; Yanjun Xie; Yonggui Wang

doi:10.1016/j.jcis.2022.09.109

Flexible Janus wood membrane with asymmetric wettability for high-efficient switchable oil/water emulsion separation

J Colloid Interface Sci. 2023 Jan;629(Pt B):719-727. doi: 10.1016/j.jcis.2022.09.109. Epub 2022 Sep 24.

Authors

Wenbo Che¹, Lingyue Zhou², Qiaoru Zhou², Yanjun Xie³, Yonggui Wang⁴

Affiliations

¹ College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou 311300, China. Electronic address: chewenbo@zafu.edu.cn.
² College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou 311300, China.
³ Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), Northeast Forestry University, Harbin 150040, China.
⁴ Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), Northeast Forestry University, Harbin 150040, China. Electronic address: wangyg@nefu.edu.cn.

PMID: 36183650
DOI: 10.1016/j.jcis.2022.09.109

Abstract

Janus membranes have attracted much attention for switchable oil/water separation because they have opposite wetting behavior on each side. However, it remains a challenge to fabricate Janus membranes with asymmetric wettability from biomass by simple methods. Herein, we prepared a flexible Janus wood (JW) membrane by cutting the natural wood along the longitudinal direction, followed by a facile top-down approach. The hydrophobic lignin was removed from the wood to prepare a highly porous and superhydrophilic wood (SW) with underwater superoleophobicity. Then, one side of the SW was sprayed with a mixture of 1H,1H,2H,2H-perfluorooctyltrichlorosilane/SiO₂ nanoparticles to form a superhydrophobic surface that hardly affected the wettability of the other side. The obtained JW membrane maintains its selective wettability in harsh environments owing to its durability and stability. Furthermore, it has a switchable, high separation efficiency of >99% for both oil-in-water and water-in-oil emulsions, which can be attributed to the unique wettability and hierarchical micro/nano structure of the JW membrane. Notably, the three-dimensional interconnected micro/nanochannels (pits and nanopores) of the JW membrane are beneficial to the size-sieving effect during emulsion separation. At the same time, the layered channels (tracheids and vessels) enable multiple separations. JW membrane is sustainable, inexpensive, stable, and easy to manufacture, providing more implications for the innovation of biomass-based Janus separation materials in industrial wastewater treatment.

Keywords: Asymmetric wettability; Emulsion separation; Janus membrane; Micro/nano structure; Wood.