Superhydrophilic polyvinyl alcohol-formaldehyde composite sponges with hierachical pore structure for oil/water emulsion separation

Regarding emulsion separation using porous materials, two keypoints, i.e. proper average pore size and wettability, should be carefully considered. Herein, three-dimensional (3D) superhydrophilic polyvinyl alcoholformaldehyde (PVA-PVF) sponges with tunable pore size are successfully prepared through crosslinking reaction of polyvinyl alcohol (PVA) in the polyvinyl alcohol-formaldehyde (PVF) network under acidic condition. The introduction of PVA containing chitosan, diatomite and sodium alginate can effectively decrease the average pore size of PVF from approximately 75 mu m to 23 mu m along with a few hundred nanometers pore channels, while maintaining porosity above 73.4%. These PVA-PVF composite sponges with hierachical pore structure are applied to separate various surfactant-stabilized oil-in-water emulsions solely by gravity. The separation efficiency can reach up to 97.40% with a high water flux of 2.40 x 104 L m-2 h-1 bar- 1. Meanwhile, the separation efficiency of different charged PVA-PVF composite sponges (i.e. PVA-CS-PVF, PVA-Si-PVF, PVA-SA-PVF) for oilin-water emulsions stabilized by different types of surfactants, including anionic, nonionic, and cationic surfactants, is also evaluated. Definitely, the PVA-PVF composite sponges with outstanding hydrophilic, excellent stability, simple preparation method can be regarded as a new candidate of emulsion separation material in practical applications.

Automated summary

The study focuses on emulsion separation using PVA-PVF composite sponges, highlighting the importance of controlling pore size and wettability. The experimental results show that these composite sponges can efficiently separate various oil-in-water emulsions, with tunable pore structures contributing to high separation efficiency.