A biomimetic Janus delignified wood membrane with asymmetric wettability prepared by thiol-ol chemistry for unidirectional water transport and selective oil/water separation

Abstract

Inspired by the amazing intelligent water manipulation behavior of cactus, spiders, and desert beetles, tremendous efforts have been devoted to developing intelligent Janus membrane materials with asymmetric wettability for unidirectional water transport and selective water/oil separation. However, the remaining challenges include tedious procedures, harsh conditions, expensive devices, and scaling-up problems. Inspired by the oriented tubular porosity and hierarchical scaffold of wood, biomimetic Janus wood membranes with asymmetric wettability were prepared by direct ultraviolet-induced thiol-ol chemistry. The delignified wood membranes were first prepared by the partial removal of hemicellulose and lignin from the natural balsa wood; Subsequently, an octadecanethiol/ethanol solution was sprayed onto the one side of the delignified wood membrane surfaces. After ultraviolet irradiation under ambient conditions, Janus wood membranes with asymmetric wettability were successfully prepared. The resultant Janus wood membranes exhibited unidirectional water-transport ability and selective oil/water separation; both heavy oil/water and light oil/water mixtures could be separated by merely changing the orientation of the membrane. In addition, the Janus wood membranes showed excellent separation efficiency and recyclability. This novel, facile, scalable, and low-cost strategy for preparing Janus membranes holds great potential for applications in several fields, such as droplet manipulation, multi-liquid separation, purification of industrial wastewater, and microfluidics.