A carbon black floating film for seawater desalination based on interfacial solar heating

Superhydrophobic carbon black (CB) nanoparticles were prepared by deposition of a monolayer of 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) on their surfaces. A thin CB floating film was assembled under solar light irradiance with the assistance of the water's surface tension and the water molecules' thermal motion. The formation of a thin floating film with suitable CB dose significantly enhanced the water evaporation rate, which was 1.9, 3.0, and 7.2 times higher than that without formation of a CB film, CB nanoparticles uniformly dispersed in water, and pure water, respectively. The temperature difference between the two air–water interfaces with and without the CB floating film was as high as 20.1 °C, which strongly confirms the interfacial heating behavior. There was no decrease of water evaporation rate over the whole measured period of 30 days, which undoubtedly reveals the excellent stability and durability of the CB floating film. Finally, a real seawater sample was used for solar distillation and the typical water-quality indexes before and after solar distillation were compared.