A bio-based 3D evaporator nanocomposite for highly efficient solar desalination

Interfacial solar desalination (ISD) is one of the best approaches to mitigate drinkable water shortages. However, finding an optimum ISD structure having high evaporation rate, high efficiency, low-cost, biocompatibility, self-floatable and salt rejecter, is still a challenging area. Here, a 3D modified bio-based floatable assembly (3D-MBFA) is reported which separates the evaporation area from bulk water. A superhydrophilic wicking fabric was chosen as both porous substrate for solar absorber and water transporter to evaporation area. The wicking fabric was modified by nanocomposite of cross-linked calcium alginate having Au nanoparticles. Thereafter, the modified wicking fabric was fixed on the piece of sunflower stem. The sunflower stem with its fantastic characteristics, such as low thermal conductivity, water transportation by micro-vessels and self-floatability, can guarantee the heat localization, surface water supply and high evaporation efficiency of the 3D-MBFA for solar steam generation. The fabricated 3D-MBFA solar steam generator demonstrates a very high evaporation rate, 3.2 kg m−2h−1, and evaporation efficiency under 1 Sun (1000 W m−2) illumination. Additionally, the 3D-MBFA shows excellent salt rejection property that is necessary for continually working without salt accumulation.