Acid-resistant supramolecular nanofibrous hydrogel membrane with core-shell structure for highly efficient oil/water separation

Hydrogel is an ideal material for oily sewage treatment due to its strong hydration ability, low-adhesive and antifouling properties. Advanced hydrogel separation membranes with harsh-environment-tolerant (such as strong acidic environments) superoleophobicity are of significance but rarely reported. Herein, a supramolecular nanofibrous hydrogel membrane was designed via one-step coaxial electrospinning method with polyvinylidene fluoride (PVDF) as the reinforced core material. Dimethyl sulfoxide (DMSO) regulates hydrogen bond crosslinking between tannic acid (TA) and polyvinylpyrrolidone (PVP). With the evaporation of DMSO, the water-insoluble supramolecular shell was formed between PVP and TA, which was tightly wrapped around the PVDF core. The pore size and wettability of the resulting membrane could be tuned by the core/shell velocity ratio. The stable superwetting properties and interspatial connectivity endow the fibrous hydrogel membranes with high separation performance for various oil-in-water emulsions and even for strong acidic oil-water emulsion. The separation permeance can reach 22,293 L m−2 h−1 bar−1 for SDS stabilized acidic oil-water emulsion (pH = 1) and maintain at approximately 17,834 L m−2 h−1 bar−1 after 3 h continuous separation, exhibiting significant applicability for large-scale filtration.