Enhanced uranium extraction using a nanostructured photothermal hydrogel membrane

Uranium is the basic resource in nuclear energy and a sword of two sides. The accidental release of radioactive uranium to the environment may cause serious impact on the environment and living creatures. Herein, a nanostructured hydrogel-based solar evaporator with in-situ formed nanostructures is designed for simultaneous solar evaporation and uranium extraction from polluted water. To be specific, poly(acrylic acid) and gelatin with embedded carbon black nanoparticles coated on a cotton cloth self-assemble into nanostructures via salting-out and acid treatment to reduce the light reflectivity and enhance the specific surface area for uranium adsorption. Numerical simulation confirms that the evaporation-induced flow accelerates the diffusion of uranyl ions towards the adsorbent. Under solar irradiation of 1 kW m−2 a maximum uranium adsorption capacity of 443.2 ± 18.1 mg g−1 is achieved in 20 ppm uranium-spiked water, meanwhile a high solar evaporation rate of 3.75 kg m−2 h−1 is reached, hence, the solar evaporator is ranked among the most powerful adsorbents/evaporators. This work provides a cost-effective and scalable approach for dealing with uranium-polluted water.