Key factor in continuous salt harvesting via solar interfacial evaporation: Water supply to evaporation ratio

Solar interfacial evaporation (SIE) as an emerging green desalination technology has been widely concerned in recent years. However, the interfacial salt fouling associated with evaporation has been limiting the development of this process. The effective separation of salt crystals from interface can avoid the salt fouling and realize resource recovery. Here, we developed a low-cost laser-printing evaporator and enabled salt crystals to drop from the interface autonomously by gravity. The water supply and evaporation capacity of evaporator would affect the location of the crystallization. Interestingly, we proposed a method to predict whether the salt crystals will drop from interface or not. To control the ratio of water supply to evaporation (Q_s/Q_e) is the critical factor to trigger the salt continuous drop process. This method is also applicable in highly concentrated salt solutions, mixed salt solutions, and salt solutions containing organic matters. This study provides new strategy for the design of salt crystallization recovery systems for solar interfacial evaporators.