Enhancing oil-in-water emulsion separation performance of polyvinyl alcohol hydrogel nanofibrous membrane by squeezing coalescence demulsification

The membrane fouling is the obstruction that limits the efficiency and durability of the nanofibrous membrane in oil-water emulsion separation. Herein, a polyvinyl alcohol (PVA) hydrogel nanofibrous membrane could continuously separate emulsion by using squeezing coalescence demulsification (SCD). During this SCD process, the small oil droplets can coalesce into bigger ones under the mandatory compression of the pore wall. And then the coalesced oil droplets will pass through the nanofibrous membrane and form an oil layer, and the oil layer can be easily removed. Furthermore, a two-phase numerical model is proposed to demonstrate this coalescence process of oil droplets in the pore. The numerical results also indicate that the pore size, wettability of membrane, and the interface tension coefficient between oil and water can control the efficiency of SCD. This SCD method endows PVA hydrogel nanofibrous membrane with a sustained separation capability, which implys that this method has great potential in practical application.