3D Multiscale Superhydrophilic Sponges with Delicately Designed Pore Size for Ultrafast Oil/Water Separation

Developing novel filtering materials with both high permeation flux and rejection rate presents an enticing prospect for oil/water separation. In this paper, robust porous poly(melamine formaldehyde) (PMF) sponges with superwettability and controlled pore sizes through introducing layered double hydroxides (LDH) and SiO2 electrospun nanofibers are reported. The LDH nanoscrolls endow the sponge with inherent superhydrophilicity and the SiO2 nanofibers act as pore size regulators by overlapping the PMF mainframe. This approach allows the intrinsic large pores in the pristine sponge to decrease quickly from 109.50 to 23.35 µm, while maintaining porosity above 97.8%. The resulting modified sponges with varied pore sizes can effectively separate a wide range of oil/water mixtures, including the surfactant‐stabilized emulsions, solely by gravity, with ultrahigh permeation flux (maximum of 3 × 105 L m−2 h−1 bar−1) and satisfactory oil rejection (above 99.46%). Moreover, separation of emulsions stabilized by different surfactants, such as anionic, nonionic, and cationic surfactants has been investigated for further practical evaluation. It is expected that such a pore size tuning technology can provide a low cost and easily scaled‐up method to construct a series of filtering materials for high‐efficient separation of target oil/water mixtures. A series of multiscale sponges with controlled pore sizes have been successfully developed via the adsorption of SiO2 electrospun nanofibers and following hydrothermal treatment. With their combined superhydrophilicity, high porosity, and delicately designed pore size compatible with oil/water mixtures, the obtained sponges can effectively separate a wide range of oily wastewater with ultrahigh permeation flux and satisfactory oil rejection.