Solar water recycling of carbonaceous aerogel in open and colsed systems for seawater desalination and wastewater purification

Solar-driven water evaporation plays an important role in the recycling of low-energy water resources. Here, we have prepared porous hydrophilic/hydrophobic cellulose graphene aerogel (CGA) to achieve efficient water recycling in solar-driven desalination and purification of heavy metal wastewater. The aerogel can reach water evaporation of 7.2 kg·m−2 for 4 h from simulated or actual seawater under 1 sun irradiation, which meets the daily water demand of two adults. Due to the interfacial evaporation and the formation of hydrogen and chelating bonds between heavy metal ions and oxygen-containing functional groups, CGA can effectively reduce the amount of heavy metal sewage to obtain water without biotoxicity. The efficient water recycling of aerogel is mainly attributed to the photothermal conversion of hydrophobic reductive graphene oxide (rGO), the interconnected porous structure formed by random stacking and cross-linking of hydrophilic cellulose sheets as well as holes in it serve as supply channel of water evaporation. In addition, ambient factors such as wind, humidity and ambient temperature boost the water evaporation of CGA in open system, while in closed system reducing the light reflection of condensed water and the relative humidity of the space is more conducive to improving evaporation efficiency.