Covalently doping polyaniline-based photothermal fabric for continuous recovery of salt and freshwater from seawater via solar-driven interfacial evaporation

Herein, we present a new three-step route to prepare a covalently doped polyaniline (PANI) -based photothermal fabric with high evaporation capacity. In which, polyacrylamide (PAM) was covalently grafted onto the cotton yarns coupling with poly(glycidyl methacrylate) via electron beam irradiation induced co-graft polymerization as primary graft layer, while PANI was subsequently grafted onto the primary graft layer in situ, which was pre-functionalized by 2-(4-aminophenyl)ethylamine, as secondary graft layer. It has been found that the PAM-doped PANI-based photothermal fabric achieved high evaporation rate 1.60 kg m−2 h−1 from pure water, 1.54 kg m−2 h−1 from 3.5 wt% NaCl solution, and 1.49 kg m−2 h−1 even in 10 wt% NaCl solution under 1 sun irradiation. Furthermore, the evaporation-induced salt crystallization did not appear on the surface of fabric, but preferentially occurred on the area of supporting platform off the fabric. This characteristic endowed the doped fabric with average recovery rate of freshwater at 1.54 kg m−2 h−1 and salt at 0.03 kg m−2 h−1 from simulated seawater. This work provides a novel strategy to the enhancement of conductive polymer based photothermal materials via covalently doping, which could popularize the application of solar-driven evaporation to resource recovery from saline waters.