Stabilized Janus micro/nano-paper with lignin nanoparticle bridges for efficient oil-water emulsion separation

Oil-spill issues are an international environmental challenge, and Janus membranes, as a great potential solution, have currently drawn lots of attention. However, the separation flux is still limited by layer structure bridging stability and microporous porosity. Herein, a photo-induced antifouling Janus micro/nano-paper with a microchannel stability was fabricated using multiscale cellulose and lignin nanoparticles (LNPs) with spherical topology via granular bridge strategy for separating oil–water emulsions. The porosity of hydrophobic layer were improved by adding multiscale cellulose and LNPs and enbowed antifouling properties. The antifouling properties of the hydrophilic layer were realized by the introduction of a photo-induced molecular switch. Under interfacial interaction, a unique “hydrophilic-amphiphilic-hydrophobic” longitudinal fluid-directed transport structure was formed under self-propulsion. In addition, a stable granular bridge structure and suitable open pore size were ingeniously integrated given the ordered distribution of spherical LNPs among cellulose. In the field of oil-water separation, it exhibited superior separation efficacy for surfactant-stabilized emulsions (separation efficiency >99 % and 98 %), recurrent and superior antifouling performance. The flux of surfactant-stabilized heavy oil emulsions (O/W and O/W) higher than 6289 and 5499 L × m⁻² × h⁻¹ × bar⁻¹ under pumping, which is 100 times higher than commercially available nanofiltration membranes. Particularly, it could effectively separate heavy oil emulsions in an ultrastable manner, flux >5500 and 5750 L × m⁻² × h⁻¹ × bar⁻¹ after 10 times cycles. The unique structure design strategy could also open up possibilities of Janus membrane in desalination and directional conveying equipment field.