Integrating solar steam generation with electrocatalysis to achieve simultaneous fouling–resistant desalination and accelerated organics degradation

Abstract

Solar steam generation is an emerging technology of desalination using renewable solar energy, but when treating saline water containing organics, the solar absorber is subject to fouling by low-surface-tension organics. Also, volatile organic compounds (VOCs) present in the source water may evaporate concurrently with water vapor and penetrate into the condensate, causing health concerns to the quality of the distilled water. In this work, we developed a unique water desalination process by integrating solar steam generation with electrochemical degradation to treat saline water containing organics, and strong synergistic effects have been experimentally demonstrated. The process used a dual-functional solar absorber that simultaneously served as a cathode of the electrochemical reactor, whose structural design was optimized by numerical simulation to balance heat transfer and mass transport. Degradation of three model organic pollutants, bisphenol A, phenol (VOC), and humic acid (natural organic matter) was evaluated, and the degradation rate constants were doubled under simulated sunlight compared to that without illumination, likely due to the high local temperature in the electrochemical reactor induced by the photothermal effect and preserved by the rational thermal insulation design. Furthermore, the concentration of VOCs in the condensate was reduced by 20 folds when electrochemical degradation of feed water was applied. In addition, the electrochemical degradation effectively mitigated humic acid fouling on the solar absorber, improving the steam generation rate by 20% after 12 h treatment, compared to the conventional solar evaporation process. Finally, the integrated solar desalination system achieved a thermal efficiency of 92.6% under real sunlight testing.