Janus Channel with Photothermal Effect for Efficient Oil−Water Separation

Abstract To address the difficulties in demulsification and coalescence, as well as the high flow resistance caused by viscous oils in the separation of stable emulsified oil-water systems, this study designed a three-dimensional MoS2@Fe3O4 particulate channel integrating photothermal responsiveness with Janus wettability to achieve efficient separation. Hydrophilic and hydrophobic MoS2@Fe3O4 particles were synthesized via a hydrothermal method and assembled into a Janus channel. Under light irradiation, the MoS2@Fe3O4-based channel generated localized heating via its efficient photothermal conversion capability, significantly reducing the viscous resistance of high-viscosity oil and promoting droplet coalescence, demulsification, and separation. The surface temperature of the material rapidly increased to 113.9 °C under 2 sun irradiation. For a high-viscosity industrial water-in-oil emulsion (viscosity 691.57 mPa s at 20 °C), the separation flux increased from 507 ± 14 L m−2 h−1 under no-light conditions to 860 ± 31 L m−2 h−1 under illumination, corresponding to an enhancement of approximately 70%, while the separation efficiency improved from 99.2 ± 0.03% to 99.4 ± 0.05%. For a surfactant-stabilized toluene-in-water emulsion, light irradiation similarly enhanced performance, increasing the flux from 4947 ± 144 L m−2 h−1 to 5393 ± 43 L m−2 h−1, while the separation efficiency from 99.7 ± 0.03% to 99.8 ± 0.06%. Furthermore, over 20 cycles of separation, the efficiency remained consistently above 99% for the toluene-in-water emulsion, and as high as 95.2% for the high-viscosity industrial water-in-oil emulsion, indicating satisfactory operational stability. The photothermal-Janus synergistic separation system developed in this study provides an effective strategy for the efficient separation of stable, high-viscosity emulsified oil-water systems.