Marangoni Effect Drives Salt Crystallization Away from the Distillation Zone for Large-Scale Continuous Solar Passive Desalination.

Solar desalination shows great potential in dealing with global water scarcity. A multistage passive solar distiller with thermal localization is especially attractive for its high-water yield. However, achieving long-term stability in large-scale devices remains a challenge because of the easy accumulation of crystallized salt inside the distiller. Here, we reported that the Marangoni effect can drive crystallized salt away along a long distance in a capillary wick, which endow the multistage passive solar distiller with the ability of salt-rejecting. In a 36 h continuous testing, the salinity of the distillation zone is limited below 12 wt % and crystallized salt only accumulates outside the device. The water yield is about 1.7 kg m h in a three-stage device, with a solar-to-vapor conversion efficiency of 114% under one sun. This novel design proves a new principle for high efficiency and long-term stable solar desalination.