A hierarchical salt-rejection strategy for sustainable and high-efficiency solar-driven desalination

Abstract

<p>Solar steam generation (SSG) is widely regarded as one of the most sustainable technologies for <a href="https://www.sciencedirect.com/topics/materials-science/seawater" title="Learn more about seawater from ScienceDirect's AI-generated Topic Pages">seawater</a> desalination. However, salt fouling severely compromises the evaporation performance and lifetime of evaporators, limiting their practical applications. Herein, we propose a hierarchical salt-rejection (HSR) strategy to prevent salt precipitation during long-term evaporation while maintaining a rapid evaporation rate, even in high-salinity brine. The salt diffusion process is segmented into three steps—insulation, branching diffusion, and arterial transport—that significantly enhance the salt-resistance properties of the evaporator. Moreover, the HSR strategy overcomes the tradeoff between salt resistance and evaporation rate. Consequently, a high evaporation rate of 2.84 ​kg ​m⁻² ​h⁻¹, stable evaporation for 7 days cyclic tests in 20 ​wt% NaCl solution, and continuous operation for 170 ​h in natural seawater under 1 sun illumination were achieved. Compared with control evaporators, the HSR evaporator exhibited a >54% enhancement in total water evaporation mass during 24 ​h continuous evaporation in 20 ​wt% salt water. Furthermore, a water collection device equipped with the HSR evaporator realized a high water purification rate (1.1 ​kg ​m⁻² ​h⁻¹), highlighting its potential for agricultural applications.<span> </span></p>