Reusable Floating Spherical Hydrogel Evaporator for Solar Desalination with Salt Mitigation and Contaminant Elimination

The generation of clean and drinkable fresh water from seawater and contaminated water holds great potential to mitigate water scarcity. Herein, a floating spherical hydrogel evaporator (SHE) is designed to achieve sunlight-driven desalination, self-salt cleaning, and removal of environmental contaminants. The spherical lightweight polystyrene is coated with a porous carbon-embedded sodium alginate/PVA/CMC photothermal hydrogel to generate a spherical hydrogel evaporator (SHE) that floats naturally. The SHE is very sensitive to the weight imbalance (500 mg) and can respond quickly to the accumulation of salt by rotation to the fresh evaporation surface, realizing excellent antisalt fouling performance. Remarkably, with energy localization by porous carbon, the spherical floating evaporator achieved a high evaporation rate of 2.65 kg m^-2 h^-1 with an evaporation efficiency of 98%. At the same time, SHE is also capable of adsorbing both organic contaminants and heavy metal ions through functional groups of the hydrogel, attaining 99% removal efficiency. Overall, this low-cost spherical floating evaporator may offer solution for eco-friendly and sustainable production of fresh water on a large scale.