Synchronous and parallel separation of opposing emulsions enabled by a heterowettability membrane

Abstract

Conventional membrane separation technologies are constrained by their inherent sequential operating mode, making it difficult to synchronously and efficiently purify emulsions. This study breaks the norm and proposes a new strategy for synchronous separation and parallel treatment of opposing emulsion using heterogeneous wetting membranes. Here the membrane features spatially distributed hydrophilic/hydrophobic regions, combined with a bidirectional gradient contraction channel module, enabling a single device to synchronously and continuously separate opposing emulsion, such as oil-in-water (O/W) and water-in-oil (W/O) emulsions. The non-uniform shear field of the gradient contraction channel destabilizes emulsion droplets and enables gradual demulsification at the membrane interface. Membrane with patterned wettability guides the dispersion to migrate in the opposite direction, coupled with shear demulsification and directional phase transport. The two-phase separation efficiency of this mechanism exceeds 99.9%, and its anti-fouling performance and long-term stability have been notably enhanced. This work establishes a new paradigm for synchronous separation and parallel processing of opposite emulsions, paving the way for efficient integrated oil–water separation technology. A heterogeneous wetting membrane integrated with bidirectional gradient contraction channels enables the synchronous and continuous separation and parallel processing of opposing oil-in-water and water-in-oil emulsions with over 99.9% efficiency while delivering enhanced anti-fouling performance and long-term operational stability.