Strong cellulose hydrogel as underwater superoleophobic coating for efficient oil/water separation

Cellulose hydrogels with high compressive strength were constructed by physical dissolution/regeneration process. Cellulose was dissolved in lithium hydroxide/urea aqueous solvent and lithium tetrafluoroborate aqueous solution was used for regeneration, to obtain hydrogels with compact structure. Compressive strength of the hydrogel reached 14.5 MPa, higher than cellulose based hydrogels of same kind in literature. The cellulose hydrogel was further used as coatings on stainless mesh, to separate oil/water mixtures by gravity. The hydrogel covered uniformly the mesh, and demonstrated underwater superoleophobicity. The coated mesh exhibited separation efficiency over 98.90 %, high permeate flux up to 38064 L m^-2 h^-1 and excellent reusability, when separating mixtures of water and various oil. Furthermore, the coated mesh remained underwater superhydrophobic in salty condition (contact angel of 154.2 ± 2.2°). The facile approach to fabricate cellulose hydrogel coated mesh demonstrated great potential in water treatment, as well as sustainability in utilizing biomass resources.