Janus-structured MXene-PA/MS with an ultrathin intermediate layer for high-salinity water desalination and wastewater purification

Abstract

Solar-driven interfacial evaporation presents significant potential for seawater desalination and wastewater purification. However, prolonged operation in marine environments often results in salt accumulation, which adversely impacts the performance and lifetime of system. Despite the progress in material design, achieving efficient evaporation while mitigating salt crystallization remains challenging in high-salinity water. In this study, we synthesized a hierarchically structured C18H37-MXene/PA/MS evaporator employing a simple yet effective methodology specifically designed for applications in high-salinity water environments. The evaporator features a dual-region configuration, with an upper hydrophobic light-absorbing layer comprising modified MXene and polyamide (PA) membranes and a hydrophilic lower layer consists of hydrophilic melamine sponge (MS). This innovative design, incorporating an ultra-thin polyamide interlayer, significantly enhances interfacial stability, thereby mitigating the interfacial separation typically observed in conventional Janus materials during prolonged usage. Furthermore, the meticulous control over the thickness of the hydrophobic layer (5.54 μm) ensures optimal thermal insulation properties of the material. Consequently, the C18H37-MXene/PA/MS evaporator demonstrates an impressive evaporation rate of 1.49 kg m−2 h−1 under 1 sun illumination, with a high energy efficiency of 92.8 %. Furthermore, the Janus architecture ensures steady performance in high salinity conditions, sustaining a high evaporation rate of 1.46 kg m−2 h−1 even in a 20 wt% NaCl solution. Furthermore, under natural sunlight, the daily freshwater yield reaches 8.91 kg m−2. The exceptional evaporation efficiency and robust salt resistance highlight its strong potential for water desalination and wastewater treatment, contributing to the advancement of sustainable water resource management.