Chitosan aerogel-carbon nanotubes double layer solar evaporator for efficient desalination

Solar-driven interfacial evaporation technology has been regarded as one of the most promising desalination technologies due to its features of high efficiency, energy-saving and low cost. However, designing a sustainable evaporator integrating light absorption, thermal management, water transport and salt resistance remains a significant challenge. Herein, we report the fabrication of a chitosan aerogel-carbon nanotubes (CA-CNT) double-layer structured evaporator by depositing CNT on the top part of CA substrate, prepared through unidirectional freezing method. The hydrophilic CA substrate exhibits low thermal conductivity and internal vertical aligned pore structure, benefiting evaporation efficiency, water transportation and salt resistance. The upper CNT layer shows an outstanding optical absorption rate of 95.04%. At one solar intensity (1 kw m-2), the evaporation rate of the evaporator was 1.55 kg m-2h-1 with an evaporation efficiency of 97.15%. Its practical applicability was tested under outdoor natural light condition, and the freshwater yield was 7.15 kg m-2 d-1. In addition, the evaporator showed good heavy metal and organic sewage purification capacity. This work provides a facile strategy for recovering freshwater from seawater and sewage.