A lignin-wood Janus membrane with three-dimensional interconnected layered micro/nano channels for on-demand separation of surfactant-stabilized oil/water emulsions

Oil/water emulsion wastewater is a typical industrial and domestic wastewater that is harmful to human health and the environment. However, it is still challenging to fabricate membrane materials for separating complex surfactant-stabilized oil/water emulsions from biomass in a facile and sustainable approach. Herein, paper industry waste lignin was prepared by self-assembly and hydrophobization into modified lignin nanospheres, which were sprayed onto delignified wood to develop a lignin-wood Janus membrane with superhydrophilic and superhydrophobic surfaces. The prepared Janus wood (JW) membrane maintains its selective wettability even under harsh conditions, demonstrating excellent durability and stability. Moreover, it can efficiently separate surfactant-stabilized oil-in-water (O/W) and water-in-oil (W/O) emulsions on demand, with a separation efficiency of >99 %. It is due to the distinct wettability and hierarchical structure of JW membranes, which feature three-dimensional interconnected layered micro/nano channels (tracheids and vessels) that enable multiple and continuous separation of oil/water emulsions. In addition, the JW membrane maintains a stable and efficient oil/water emulsion separation efficiency after 10 cycles, which offers an efficient, cost-effective, sustainable, and scalable approach for applications of all-wood-based separators in the oily wastewater treatment field.