Multifunctional hydrogel platform for efficient Photothermal seawater evaporation and high-capacity uranium extraction

Abstract

Fresh water scarcity and the sustainable utilization of nuclear energy are two pressing and intertwined global challenges. Herein, a novel multi-functional hydrogel-based platform (PSHDU) is proposed to address the issues through simultaneous photothermal interfacial solar seawater evaporation (ISSE) and seawater uranium extraction (SUE). The PSHDU operates efficiently through the synergistic interaction of three core components: the photothermal conversion unit, uranium adsorption unit, and substrate material. The photothermal conversion unit employs mesoporous polydopamine nanospheres (mPDA), while the uranium adsorption function is achieved by amine-ratio-regulated UiO-66-NH₂ (U6N). The solvent-induced phase-separated polyzwitterionic hydrogel (PSH_X) integrates a solvent-tunable porous architecture with its unique anti-polyelectrolyte effect, demonstrating rapid swelling and efficient water transport capabilities in high-salinity environments, which formed a more stable and highly hydrated evaporation platform. This design not only enhances the system salt resistance and hydration properties but also achieves efficient water transport by optimizing the pore structure. Benefiting from the synergistic promotion of mPDA and U6N, PSHDU not only shows an efficient natural seawater evaporation rate up to 4.55 kg m⁻² h⁻¹ but also exhibits a uranium extraction capacity of 289.33 mg g⁻¹ under simulated solar sunlight (1 kW m⁻²), simultaneously, which is 37.05% higher than that of PHSD (without the addition of U6N) and 36.48% higher than that of itself without light. Meanwhile, PSHDU maintains outstanding antifouling property, salt resistance and 96% of its evaporation performance after a 72 h cyclic stability test. Therefore, as a multi-functional evaporation platform, PSHDU can simultaneously alleviate the existing shortages of freshwater and uranium and provide ideas and possibilities for integrating more novel functions into ISSE materials.