Development of a novel cellulose foam augmented with candle-soot derived carbon nanoparticles for solar-powered desalination of brackish water

Scarcity of clean water is a worldwide challenge, hampering the further development of human civilization. Solar driven water desalination using solar stills (SS) provides an attractive and sustainable approach to solve this severe challenge by converting brackish water to freshwater using solar energy. However, the low thermal performance and water productivity of this approach are bottlenecks for realizing efficient clean water harvesting from brackish water. Here, we designed and implemented a tubular SS for brackish water purification using fully renewable and locally available materials, namely a novel porous 3-dimensional cellulose foam (CF) modified by deposition of carbon nanoparticles synthesized from candle soot (CSCNPs). With its rough surface, the modified CF could absorb more than 92% of the energy across the solar spectrum. The 3-D interconnected hydrophilic micro-channels of the CSCNP modified foam fibers augment heat localization and promote excellent water transportation. The solar driven evaporation efficiency of the modified tubular SS resulted in a full day water production of 6.40 L m(-2) (compared to 2.32 L m(-2) for the conventional tubular SS) with peak evaporation efficiency of 360% and significantly lower water cost per liter. The CSCNP modified CF based tubular SS unit thus offers a low-cost and efficient choice for improved solar driven evaporation and freshwater production. The presented work provides new insights into solar driven evaporation/condensation processes and thermal performance during sustainable brackish water desalination and waste-water management.