Multilayer graphite nano-sheet composite hydrogel for solar desalination systems with floatability and recyclability

Abstract

The application of carbon-based nanomaterials with high photothermal conversion efficiencies in solar desalination has the advantages of economy, environmental protection, availability and sustainability. In this work, a floating magnetic hydrogel is successfully synthesized with multilayer graphite nano-sheets, polyvinyl alcohol, SiO₂ aerogels and Fe₃O₄ nanoparticles. In this floating magnetic hydrogel, the multilayer graphite nano-sheets act as both a photothermal conversion material and supporting material for the mechanical structure. The introduction of SiO₂ aerogels reduces the density of the hydrogel, enabling it to float at the gas–liquid interface, and improving the photothermal conversion efficiency. The Fe₃O₄ nanoparticles endow the hydrogel with magnetism, making the recycling of the floating magnetic hydrogel easy. The seawater evaporation rate of the floating magnetic hydrogel is 3.77 times that of the control group under an irradiation of 1 kW m⁻². Furthermore, a semi-automatic fresh water collection device is designed and prepared successfully for the practical application of the floating magnetic hydrogel. These results prove that this floating magnetic hydrogel is a promising candidate for seawater desalination and water purification.