Ultra-low cost cotton based solar evaporation device for seawater desalination and waste water purification to produce drinkable water

Steam generation using solar energy has been impractical for years ascribable to its low efficiency. In recent years, interfacial heating of water has been touted as the practical solution to harvest large scale steam generation. In this paper, we present an extremely low cost candle soot coated cotton as an ideal floating absorber to generate highly efficient steam using the concept of interfacial solar heating. The floating absorber was synthesized from traditional household materials and a photothermal efficiency of 80% was achieved under 1 sun illumination. In addition, the novel floating absorber is easy to fabricate as it requires no sophisticated laboratory instruments or expertise. The floating absorber was tested for solar desalination of actual sea water using a homemade solar still where the purified water had salinity levels comparable to other drinking water levels like tap water, packaged drinking water and so on. In addition to the salinity levels of water, the purified water obtained from water purification of sewage was tested for bacteria colonies and no colony forming units (CFU) were present which again suggests the obtained purified water being drinkable. The results of this work should motivate further research in simplistic, low cost photothermal materials and its application in the production of clean drinkable water.