Ternary hierarchical structure based solar-driven evaporator for long-lasting concentrated brine treatment

Solar-driven evaporation has been a promising desalination method for treating concentrated seawater, since it is cost-effectiveness, simplicity, and environmentally friendly. However, this method faces an unavoidable long-term problem that the salt generated in the evaporation processes would affect and hinder its evaporation efficiency. Because the salt inevitably crystallizes on the surface of photothermal evaporation materials, and this crystallization process increases with time to impair the material area of the sunlight absorption and evaporation. Here, we show a ternary hierarchical structure based solar-driven evaporator that reduces the evaporation material surface coverage of the salt to get long-lasting concentrated brine treatment capacity. This evaporator is constructed by plugging vertically arranged hollow tube arrays across a porous plate. The top, middle, and bottom of the evaporator respectively serve as the salt crystallization site, the evaporation site, and the light absorption site. Meanwhile, the self-cleaning of the evaporator can be achieved by back diffusion of the crystallized salts. As a result, this efficient and durable evaporator exhibits freshwater production of 10.21 kg/(m²·day) in outdoor experiment in the treatment of the concentrated natural seawater (21.3 wt%).