Plasmonic chemically modified cotton nanocomposite fibers for efficient solar water desalination and wastewater treatment

Water desalination and wastewater treatment via solar photothermal energy conversion are among the most important technologies to address the increasing pressing global water scarcity. Solar energy is the cleanest, most abundant, renewable natural resource available. Herein, we report the development of highly efficient, flexible, low weight, and cost effective Plasmonic Functionalized Cotton (PFC) nanocomposite materials for solar steam generation through the efficient evaporation of surface water pools. The PFC nanocomposites contain metallic nanoparticles that exhibit strong solar absorption followed by non-radiative relaxation causing the absorbed energy to be converted into heat for efficient water evaporation. The chemically modified cotton leads to a partial hydrophobic surface that allows the material to float on the water's surface and provide excellent thermal insulation properties in addition to facile and scalable synthesis. The PFC nanocomposites containing Au and Ag nanoparticles are demonstrated to be among the most efficient solar thermal converters reported to date for solar water desalination. The Au/Ag-PFC fibers exhibit average water evaporation rates of 1.4 and 11.3 kg m-2 h-1 with superb solar thermal efficiencies of up to 86.3% and 94.3% under 1 and 8 sun illumination, respectively. Furthermore, the Au/Ag-PFC fibers display stable evaporation rates over more than 10 repeated evaporation cycles without any performance decline under acidic solution at pH 2 or basic solution at pH 10. The successful application of the Au/Ag-PFC fibers for the removal of organic dyes from contaminated water through the solar steam generation is also demonstrated. The high solar thermal evaporation efficiency, excellent stability and long-time durability make the PFC nanocomposites excellent candidates for applications in seawater desalination and wastewater treatment by solar-steam generation.