A Sponge-like Hydrogel with Squeeze-Regenerability for Effective Water Removal from Immiscible Oil/Water Mixtures

The treatment of water-contaminated oil is an important challenge in the global energy industry. However, the oil/water separation materials suffer from oil fouling, pore blockage, and poor operational stability, hindering their practical applications. Here, cryo-assembled templating and polymerization are proposed to synthesize PAM-GO hydrogel sponge (PGHS) with interconnected porous topology and outstanding mechanical properties. The capillary effect and reduced diffusion resistance caused by the porous structure of PGHS enhance the internal water transport rate by approximately 2 orders of magnitude compared with that of PAM dense hydrogel. The water trapped by the hydrophilic sponge-like structure endows PGHS with underwater superoleophobicity. Consequently, PGHS demonstrates an ultrahigh separation efficiency for immiscible oil/water mixtures, with the purity of the separated oil exceeding 99.9%. Besides, a portion of free water can be released via mechanical squeezing from the elastic sponge-like structure, enabling facile cyclic regeneration of PGHS. This work provides a promising pathway toward effective oil/water separation.