Lotus-Root-like Supermacroporous Cryogels with Superphilicity for Rapid Separation of Oil-in-Water Emulsions

The separation of surfactant-stabilized oil-in-water emulsions is a challenging issue as such state-of-art technologies usually suffer from energy-intensive, time-consuming, and inefficient processes. Here, we constructed a series of superphilic cryogels of regular, ordered, and oriented porous structures that are similar to that of lotus root. Using dimethyl sulfoxide as a solvent and its crystals as porogens, monolithic cryogels were obtained by polymerization of polyethylene glycol diacrylate (PEGDA) embedded with polydivinylbenzene (PDVB) particles at the nondeeply frozen condition. The as-prepared cryogels were of interconnected micrometer-sized porous structure in the range of several micrometers to several tens of micrometers in pore diameter. The pristine polyPEGDA cryogels displayed superphilicity in air, superhydrophilicity under oil, and oleophobicity underwater, and the addition of PDVB particles into the matrix increased the surface roughness and thus led to a higher oleophobicity underwater as well as an enhancement in mechanical strength. The composite cryogels showed a rapid separation of the surfactant-stabilized oil-in-water emulsion with high separation efficacy up to 99.9% driven solely by gravity, and they exhibited a good recyclability after eight time treatments. Owing to the combination of the special interfacial interactions and pore-size effect, the three-dimensional supermacroporous monoliths with superwettability are a potential alternative for separation of oil-in-water emulsion with high separation efficacy and low cost.