Reduced graphene oxide-based calcium alginate hydrogel as highly efficient solar steam generation membrane for desalination

Solar-driven evaporation has been considered as one of the potential methods for desalination and sewage treatment. However, optical concentrators and complex multi-component systems are essential in advanced technologies, resulting in low efficiency and high cost. Here, we synthesize a reduced graphene oxide-based porous calcium alginate (CA-rGO) hydrogel which exhibits good performance in light absorption. More than 90% of the light in the whole spectrum can be absorbed. Meanwhile, the water vapor escapes from the CA-rGO film extremely fast. The water evaporation rate is 1.47 kg center dot m(-2)center dot h(-1), corresponding to the efficiency 77% under only 1 kW center dot m(-2) irradiation. The high evaporation efficiency is attributed to the distinctive structure of the film, which contains inherent porous structure of hydrogel enabling rapid water transport throughout the film, and the concave water surfaces formed in the hydrophilic pores provide a large surface area for evaporation. Hydrophobic rGO divides the evaporation surface and provides a longer three-phase evaporation line. The test on multiple cyclic radiation shows that the material has good stability. The CA-rGO hydrogel may have promising application as a membrane for solar steam generation in desalination and sewage treatment.

Automated summary

A porous calcium alginate-based reduced graphene oxide hydrogel was synthesized, showing excellent light absorption performance and high efficiency in water evaporation, making it a promising membrane for solar-driven desalination and sewage treatment. The high efficiency is attributed to its unique structure and the hydrophobic nature of reduced graphene oxide.