Self-assembled porous salt crystals for solar-powered crystallization

Thermally localized solar evaporation has been recognized as an efficient and suitable pathway for desalination and brine treatment. However, the annoying salt crystallization inside the porous evaporator brings challenges for hypersaline brine evaporation. Here we argue that salt crystals can serve as an ideal structure for evaporation with proper manipulations. Taking advantage of the self-amplifying salt creeping and efflorescence effects, the salt crystals self-assemble to form a hierarchical porous salt evaporator (HPSE), enabling passive liquid supply and efficient evaporation. With a low-cost, solar-powered device based on HPSE, we achieve stable evaporation and crystallization when treating the hypersaline brine with 27.3 wt% salinity under one-sun illumination, resulting in a high evaporation rate of 18.78 kg m-2 h-1. This work bridges the important knowledge gap between fundamental salt crystallization and brine treatment, paving a path toward sustainable water economy.