Asymmetric Wettable Three-Dimensional Janus All-Cellulose Aerogels: Controllable Construction with a Similar Phase Self-Assembling Strategy and Oil-Water Separation Performance

Abstract

Aqueous ecological environment is exacerbated by indiscriminate discharge of industrial and municipal wastewater, particularly oily contaminants. Janus materials with unique asymmetric wettability have been considered potential candidates for oil-water separation. Herein, we developed a novel approach to accomplish controllable construction of three-dimensional Janus all-cellulose aerogels with asymmetric wettability based on a similar phase self-assembling strategy. Significantly, the asymmetric structure could be controlled easily by tailoring thickness of hydrophobic/hydrophilic layers. Three-dimensional Janus all-cellulose aerogels had both super-hydrophilic/oleophilic and super-hydrophobic/oleophilic cellulose layers simultaneously. The adsorption capacity of three-dimensional Janus all-cellulose aerogels to oil reached up to 34.38g/g. Three-dimensional Janus all-cellulose aerogels could effectively separate a variety of oil-water mixtures and water-in-oil emulsions only driven by gravity, even surfactant-stabilized emulsions. The separation efficiency of three-dimensional Janus all-cellulose aerogels was more than 99% with the corresponding high separation flux. The ‘Trade-off’ effect in the field of membrane separation was avoided effectively. Three-dimensional Janus all-cellulose aerogels exhibited good stability and recyclability. Moreover, the demulsification and separation mechanism was analyzed in details. This work provided not only an environmental-friendly, facile and flexible approach to construct controllable three-dimensional asymmetric wettable Janus materials, but also a scientific understanding and development of the separation mechanism of three-dimensional Janus materials.

Keywords: Controllable construction, Similar phase self-assembly, Janus material, Cellulose aerogel, Oil-water separation