Janus electrospun MXene-based photothermal membrane for efficient solar-driven interfacial evaporation and simulated...

High-salinity radioactive wastewater is challenging to treat because it contains radionuclides together with abundant coexisting ions. Solar-driven interfacial evaporation (SDIE) offers a low-energy method for radioactive wastewater treatment, but salt accumulation remains a key limitation. Herein, an electrospun MXene-based Janus membrane (PMPJ) was developed by integrating a hydrophobic PVDF/MXene photothermal layer with a hydrophilic PAN water-transport layer. Regulating the thickness ratio of the hydrophilic to hydrophobic layers of the Janus membrane reveals that appropriate adjustment of the bilayer ratio balances water delivery, heat localization, vapor escape, and suppresses salt accumulation. The optimized PMPJ-7 membrane exhibited strong light absorbance of 91.78%, asymmetric wettability, and structural stability. A relatively thin hydrophobic layer optimized the balance between heat generation, water transport, and vapor escape within the membrane, while a two-dimensional water transport structure improved water supply and heat localization at the evaporator level. Under 1 sun irradiation, PMPJ-7 exhibited an evaporation rate of 1.84 kg m^-2·h^-1 and a photothermal conversion efficiency of 96.5%. When treating high-salinity simulated radioactive wastewater (HSCW), PMPJ-7 significantly reduced radionuclide concentrations in the condensate, achieving decontamination factors of 10^5.82, 10^5.09, 10^5.58, and 10^4.11 for Co²⁺, Sr²⁺, Cs⁺, and I^-, respectively, with removal efficiencies exceeding 99.99% for all target ions. More importantly, the Janus membrane maintained stable cyclic evaporation by separating water supply from photothermal evaporation and vapor release under high salinity. This work provides a Janus membrane design strategy for stable SDIE and solar-assisted treatment of simulated radioactive wastewater.