Embedded solar-powered hydrogel evaporator for enhancing uranium extraction from seawater

Compared to the 6.08 million tons of uranium found on land, the oceans contain a staggering 4.5 billion tons, offering nearly limitless potential fuel for the nuclear industry. Extracting the meager 1/3 billionth concentration of uranium from seawater is crucial yet immensely challenging. This study utilized a method involving reduced graphene oxide, polyvinyl alcohol, and poly(acrylamide oxime) (rGO/PVA/PAO) co-gelation to create an embedded solar-driven hydrogel evaporator (GPPH). The rGO hydrogel acted as a photothermal material, while the PVA/PAO (PP) hydrogel served as both the evaporator's water source and uranium adsorbent. The highly porous and hydrophilic PP hydrogel exhibited a uranium adsorption capacity of 1289 mg g⁻¹ m_U/m_PAO in 64 ppm U-spiked simulated seawater. Under solar radiation, the evaporation facilitated by the rGO hydrogel accelerated uranium ion diffusion in the hydrogel, further elevating the uranium adsorption capacity to a remarkable 56.7 %, or 2019 mg g⁻¹ m_U/m_PAO, surpassing most PAO-based uranium adsorbents. Additionally, due to the high water transport rate and water content of the polypropylene hydrogel, coupled with low evaporation enthalpy and superior structural design, the GPPH evaporator achieved a solar thermal evaporation rate of 2.85 kg m⁻² h⁻¹, significantly outperforming the 1.9 kg m⁻² h⁻¹ of the rGO hydrogel.