Facile and sustainable fabrication of high-performance cellulose sponge from cotton for oil-in-water emulsion separation.

Given complexity and diversity of oily wastewater, developing highly efficient separation materials through green and facile strategy are urgently needed. Herein, a smart strategy is demonstrated to transform raw cotton into uniform cellulose sponge for separation oil-in-water emulsion. The raw cotton is directly treated in zinc chloride aqueous solutions through a controllable dissolution process. After regeneration without any further chemical modification and freeze drying, the evolved cellulose sponge, which is composed of partially dissolved cotton fiber and exfoliated regenerated cellulose, exhibits interesting three-dimensional (3D) interconnected hierarchical porous network structure and stable wettability of superoleophobicity (θoil>150º) under water. Cellulose sponge has excellent underwater superoleophobicity and antifouling property due to the natural hydrophilicity of cellulose. Based on the beneficial 3D hierarchical structure and superwettability, the cellulose sponge can separate highly emulsified oil-in-water emulsions with efficiency up to 99.2% solely under the driving of gravity. Our strategy provides a generic way to convert cellulose-based materials into cellulose porous materials with excellent permeability, separation efficiency, antifouling, and reusability property for oil/water emulsions separation. This economical, environmentally friendly and functional cellulose sponge not only allows natural cotton resources to be used rationally with high value-added, but also effectively solves the problems of oily wastewater.