Solar steam generation on filament textile evaporators of polysaccharide/polypyrrole/Fe3O4 composite compared to membrane evaporators

Solar-steam generation is an ecological and energy-efficient technology to compensate for the lack of clean water by utilizing a photothermal steamer to evaporate water with solar energy. The development of highly efficient systems may make a significant contribution to communities that need clean drinking water. Here, in a dispersion of TEMPO-oxidized cellulose nanofiber (TOCNF) filament, polypyrrole (PPy) was chemically polymerized and Fe₃O₄ nanoparticles were deposited in-situ on a filament, and TOCNF/PPy/Fe₃O₄ filaments were woven into the textiles. The prepared textiles achieved a maximum evaporation rate of 1.68 kg/m²h. This rate is 10 % higher than conventional membrane steamers containing the same photothermal materials. The high efficiency of filament textile steamers is even more evident under outdoor irradiation: Compared with the maximum evaporation rate (1.98 kg/m²h) of chitosan/PPy/Fe₃O₄ membrane steamer, the evaporation rate of TOCNF/PPy/Fe₃O₄ filament textile steamer was 2.86 kg/m²h. The results show a 44 % increase in the rate of the textile steamer. This is because the inter-filament space of the latter steamer can provide a sufficient steam-passage channel. In addition, the evaporation rates of solar steam generated from seawater and aquarium water were lower than that from pure water, because the non-volatile solute dissolved in water causes a decrease in vapor pressure, that is, an increase in the boiling point. This study suggests the necessity of a channel in a reactor to allow steam to flow during evaporation, besides the choice of photothermal materials. This investigation provides the ultimate solution for effectively ensuring potable water evaporated by solar heat from ponds and oceans.