Insights into Localized Crystallization in the 3D-Cone Solar Evaporator for High-Salinity Desalination

Solar-driven interfacial evaporation desalination is regarded as a promising solution to address freshwater scarcity. However, salt deposition remains a significant challenge. While structural designs such as designated deposition sites can control crystallization, the mechanisms of salt precipitation at specific locations are still unclear. In the present work, we designed a three-dimensional conical evaporator using low-cost cellulose paper for efficient solar-driven desalination. This innovative evaporator design achieves controlled salt crystallization by meticulously balancing the rates of salt diffusion and accumulation, thereby directing salt precipitation to a predetermined location approximately 1.4 cm above the conical base. This phenomenon arises from temperature variations across the evaporator's three-dimensional surface, which induce differences in water surface tension and create favorable sites for salt precipitation. Such a salt management strategy allows for continuous operation for up to 8 h in high-salinity conditions (24.5 wt.%) without compromising performance. Under one sun irradiation, the evaporator demonstrates exceptional performance, with an evaporation rate of 2.54 kg·m^-2·h^-1 and an impressive energy conversion efficiency of 93.7%. This approach provides valuable insights into the salt precipitation mechanism, contributing to the future design of three-dimensional evaporators and innovative salt collection strategies.