Graphene hydrogels for enhanced solar distillation of water

The lack of pure water is one of the major challenge of the contemporary society, especially in the low populated and arid areas of the world. Desalination is an efficient way to produce pure water, and direct solar distillation processes (by solar stills) are the most suitable for rural areas, even though their productivity is low. To increase the productivity of these systems, in this work graphene hydrogels were synthetized to increase water evaporation yield to produce pure water by using solar energy. Graphene nano-powders were successfully dispersed and embedded in thin gum arabic cross-linked gelatin membranes. The very high thermal conductivity of graphene at room temperature, with its higher absorption ability of solar energy, leads water to reach higher temperature compared to pure water. Therefore this light to heat conversion process enables an enhancement of evaporation rate and of evaporation efficiency of water by using graphene hydrogels. The advantages of this hybrid material are the enhanced pure water production, the possibility to collect and re-use the membrane several times thanks to its long time stability in water, the simplicity in synthesis. Graphene hydrogels were characterized by means spectroscopy techniques (Raman, XPS), SEM, and the dispersion stability of graphene was studied by spectrophotometry, while evaporation rate and evaporation efficiency were evaluated by gravimetric measurements under UV-Visible irradiation (generated by a solar simulator).