Figure 18.

Solar water heating for wastewater purification. (a) Self-floating aerogel composed of CNTs and hydroxyapatite nanowires for highly efficient solar-energy-assisted water purification. The middle panel shows the concentrations of three types of heavy metal ions in the simulated wastewater before and after photothermal wastewater purification. The right panel shows the UV–visible absorption spectra and photographs of a rhodamine B aqueous solution before and after photothermal purification. Reprinted with permission from ref (457). Copyright 2019 Elsevier. (b) A superwicking and super-light-absorbing aluminum surface for efficient solar-based water sanitation. The schematics show the black aluminum sheet with a rotatable platform to maximize the incident solar flux, and an open capillary architecture for easy cleaning. The histogram demonstrates the water sanitation of four types of heavy metals. The right panel shows the photographs of a Cr²⁺ (top) and a rhodamine 6G dye (bottom) aqueous solution before (left) and after (right) photothermal purification. Reprinted with permission from ref (501). Copyright 2020 Singh et al., published under the CC BY 4.0 license http://creativecommons.org/licenses/by/4.0/.