Photothermal Promotion of Uranium Extraction from Seawater with Self-Supporting Functionalized Polyurethane Sponge

Abstract

Extracting uranium from seawater at an ultralow concentration (3.3 ppb) is a promising approach for the sustainable development of nuclear energy, which presents a critical obstacle. Herein, we report a photothermal-promoted extraction strategy by utilizing a self-supporting covalent organic polymer-based sponge (named TpPa-SO₃H@PU sponge) composed of black polyurethane sponge substrate and β-ketoenamine covalent organic polymer with sulfonic acid groups. The adequate water transport induced by photothermal conversion significantly improves the mass transfer of uranyl ions. Compared with the dark condition, a 25.8% increase of uranyl extraction capacity, up to 36.4 mg g⁻¹, is achieved under simulated sunlight irradiation. In 1 L of seawater, 83.8% of uranyl is extracted after exposure to natural sunlight for 48 h. Furthermore, 20 mL of concentrated solution containing 1 ppm uranyl is obtained from 9 L seawater after nine consecutive extraction-elution cycles. These results demonstrate that TpPa-SO₃H@PU sponge holds significant potential for practical uranium extraction from seawater under natural sunlight.