Solar-driven brine evaporation with directional salt crystallization and passive removal

Hypersaline brines (salinity >10 wt%) generated by the water, energy, and agricultural sectors present a significant challenge for sustainable wastewater management. Although solar-driven interfacial evaporation offers an energy-efficient route for brine treatment and zero-liquid-discharge operation, persistent salt accumulation hinders long-term performance and operational stability. Here, we report a solar interfacial evaporator-crystallizer comprising a bilayer, two-support-span architecture that integrates a nanostructured titanium (Ti) mesh with a photothermal b‑PDMS layer. Localized top-surface light absorption and unidirectional vapor generation promote edge-directed salt crystallization, mitigating surface fouling. Under extreme salinity (20 wt%), the device maintains net solar-driven evaporation flux ≥1.2 kg·m ‒2 h ‒1 , redistributing salt to span edges, limiting crust coverage to <10% during the 12 h illumination test. Owing to the b-PDMS layer, low interfacial adhesion enables passive salt shedding overnight, supporting cyclic stability. Time-lapse imaging and environmental scanning electron microscopy elucidate the coupled dynamics of evaporation, crystallization, dissolution, and shedding across diurnal cycles. Furthermore, indoor cyclic and outdoor tests using real seawater brine demonstrate operational robustness and scalability, establishing this platform as an effective, zero-liquid-discharge solution for hypersaline brine management.