High-rate long-lasting solar desalination towards hypersaline brine enabled by introducing a siphon-drop mode

Abstract

Direct solar steam generation (DSSG) is well-proven to be a sustainable and effective technique to provide high-quality freshwater supply. However, it customarily suffers from severe salt accumulation, especially for treating strong brine, becoming a fatal bottleneck for approaching its commercial applications. Herein, we developed a DSSG with potent siphon-drop mode to achieve powerful self-absorbing and self-desalting, in which the 3D cone-shaped self-supporting polydopamine and polyethyleneimine co-coated poly(acrylonitrile-styrene-acrylate) (PDA-PEI@ASA) used as photothermal material (PTM). Source water can be spontaneously and continuously pumped to the top of water-evaporating surface of PTM via strong siphon effect, and the top-down active water diffusion on evaporating surface can effectively take the salts away from the system. Such above features give the DSSG real-time antifouling nature and hence address the fatal issue of salt accumulation. Accordingly, when continuously treating a near-saturated brine (20% NaCl) for at least 168 h, no obvious salts deposition can be found with a steady water evaporation rate of ∼2.550 kg m–2 h−1. This work could help shed novel light on the design of practical DSSG systems toward efficient lasting freshwater extraction, holding great promise for global water scarcity.