Solar evaporation with solute replacement towards real-world applications

Abstract

As a promising pathway for sustainable desalination and wastewater treatment, thermally-localized solar evaporation has been successfully demonstrated, mainly with water or NaCl solution. However, the evaporated solution can vary a lot from these ideal choices in real applications, which can easily trigger evaporation failure. Herein, we propose a solute-replacement strategy for solar evaporation, guided by a comprehensive understanding between solar evaporation and solution properties. By decoupling the heat loss and salt rejection pathways, stable evaporation of highly viscous and low-solubility solution was demonstrated, while significant performance degradation was observed with conventional design. The evaporation rate was enhanced up to 478% for the evaporation of NaAlg solution with 225 times higher viscosity than water. A high evaporation rate of 2.46 kg m⁻² h⁻¹ and a water collection rate of 2.12 kg m⁻² h⁻¹ were also demonstrated in outdoor solar evaporation and three-stage solar distillation tests of NaAlg solution, respectively. The fundamental understandings and proposed strategy regarding extreme solution properties could promote solar evaporation one-step further towards real-world applications.