All-weather-available down carbon fiber hydrogel with enhanced mechanical properties for simultaneous efficient clean water generation and dye adsorption from dye wastewater

Solar-driven photothermal conversion can produce clean water from dye wastewater while leaving the dye in the evaporation medium. Herein, a biomass-based composite hydrogel via down-fiber carbon (DFC) aerogel modified with chitosan-polyvinyl alcohol (CS-PVA) hydrogel was designed to address the aforementioned problem. The CS-PVA@DFC hydrogel integrated the capacity of simultaneous clean water production/dye adsorption during the day and continuous dye adsorption during the night. Furthermore, the modification of the CS-PVA hydrogel endowed the composite hydrogel with enhanced compression stress of 190.07 kPa (76.03 times that of DFC aerogel of 2.50 kPa) and impressive resilient recovery. Moreover, the CS-PVA@DFC hydrogel possessed solar light absorption of 99.56 % and strengthened water replenishment capacity due to the high porosity and CS-PVA hydrophilic network structure. The CS-PVA@DFC hydrogel demonstrated a stable, high evaporation rate of 2.34 kg·m-2·h-1 and simultaneous dye adsorption capacity of 70.39 % for treating methyl orange dye solution within 5 h. Additionally, the 24-h outdoor test showed that the CS-PVA@DFC hydrogel possessed excellent clean water production capacity during the daytime (reaching 4.17 kg·m-2·h-1 at 1:00p.m.) and continuous satisfactory dye adsorption capacity all day (89.68 %). These findings will inspire researchers seeking opportunities to improve the mechanical properties of aerogel and its application for treating wastewater, especially wastewater with harmful dyes.