Double-layered cellulosic interfacial evaporator via upcycling of waste cotton fabrics for efficient solar desalination

Constructing efficient solar-driven interfacial evaporators (SDIEs) derived from biomass or waste stream materials (e.g., cellulose) is still challenging due to their less elaborate porous structure. Herein, we showed waste cotton fabrics could be dissolved and regenerated into aerogels with tunable channels suitable for constructing a double-layered SDIE. The evaporator consists of a polypyrrol-coated top layer featuring vertical channels with larger pores and a hydrophilic bottom layer featuring smaller pores. With such design, the photothermal and pro-evaporative capabilities of the top layer was coupled with the strong capillary effect of the bottom layer to drive effective evaporation. A desirable evaporation rate of 3.20 kg m−2h−1, 80.0 % solar-to-vapor conversion efficiency under 1 sun irradiation, and a reduced evaporation enthalpy of 962 J g−1 was achieved. The SDIE also exhibits high purification efficiency (exceeding 99 %) during long-term operation of seawater desalination and shows great potential in treatment of waste streams of high salinity dyeing effluent. In summary, this work demonstrates a case of upcycling waste cotton fabrics for water desalination.