Highly Energy-Efficient 3D-Printed Solar Evaporator with Integrated Salt Self-Collection for Zero Liquid Discharge Desalination

Solar-driven interfacial evaporation (SDIE) has emerged as a promising technology for sustainable desalination and brine management. However, conventional SDIE systems have struggled to enhance evaporation efficiency while mitigating salt scaling. Here, we introduce an innovative 3D-printed photothermal stainless steel SDIE system designed to address these limitations. By leveraging the high thermal conductivity of stainless steel, our design creates a strategic temperature differential across the SDIE, maximizing energy harvesting from solar radiation, ambient air, and feedwater. The unique edge-protruding structure facilitates localized salt crystallization and autonomous detachment, achieving effective salt self-collection. Numerical simulations reveal that Marangoni convection drives liquid flow toward the edge for the controlled salt crystallization. Under one sun radiation, our system achieves a remarkable evaporation rate of 3.18 kg m-2 h-1 and a salt collection rate of 1.57 kg m-2 h-1 with highly concentrated brine (25 wt % NaCl solution). Outdoor and real brine tests validated its capability for zero liquid discharge desalination, demonstrating both enhanced desalination efficiency and sustainable brine management through simultaneous water recovery and salt collection. This study offers a new strategy for designing highly efficient SDIE systems, addressing the challenges of sustainable desalination and paving the way for future advancements in water treatment technologies.