Water Lily-Inspired CNT@cotton towel solar evaporator with Marangoni effect and optimal water supply for achieving zero liquid discharge desalination and irrigation

Solar-driven interfacial evaporation is an environmentally friendly technology to address the global water scarcity crisis by efficiently purifying unavailable water resources (seawater, brackish water, high salinity wastewater and various water resources). However, the inevitable contradiction between salt deposition and highly efficient water evaporation during long-term desalination remains a major challenge. In this work, we report a self-floating bionic water lily evaporator with zero liquid discharge, consisting of CNT@cotton towel with the uneven-gap structure as the photothermal material and the square groove insulation foam with controllable water supply as edge-preferred crystallization support. The formed four-building-in ramp structure generates different surface tensions along the whole ramp and brings Marangoni flow. With the combination of Marangoni flow and optimal water supply volume, salt is spatially isolated from the CNT@CT surface, the biomimetic design can achieve continuous water evaporation and salt collection (79 g m^-2h⁻¹) for 84 h in 10 wt% NaCl under edge-preferred crystallization. The purified water meets drinking water standards and is applied to growing crops. This distinctive solar evaporator provides new insights for designing a low-cost and zero-liquid-discharge evaporator, advancing its application in high-saline brines, various water resources, and irrigation.