Amidoxime-functionalized carbon dot-incorporated cyclized polyacrylonitrile nanofibrous mats for photothermal-enhanced uranium extraction from seawater†

Uranium extraction from seawater provides a sustainable source of uranium for the nuclear industry. Amidoxime (AO)-based fibrous materials are among the most promising chemical adsorbents due to their high efficiency. However, further improvements in adsorption capacity and mechanical durability are required. Herein, we developed amidoxime-grafted photothermal-enhanced cyclized polyacrylonitrile nanofibrous mats (AOCPAN NFs) incorporated with carbon dots (CDs). The incorporation of CDs into PAN NFs enhanced their mechanical strength and antibacterial properties. Among different CDs ratios (0–20%), PAN NFs with 10 wt% CDs exhibited the highest performance with a tensile stress of 5.7 MPa, which improved to 8.1 MPa after the cyclization. Remarkably, the AOCPAN-10%CDs mats maintained a high tensile stress (6.8 MPa), twofold that of the AOCPAN mats. The AOCPAN-10%CDs mats exhibited significant photothermal efficiency, with surface temperatures rising to 49.6 °C under simulated sunlight. Under sunlight, the AOCPAN-10%CDs mats exhibited a high adsorption capacity of 455.3 mg g⁻¹ at pH 8, compared to the AOCPAN (390 mg g⁻¹), and achieved 1152.5 μg g⁻¹ after flow-through 25 L natural seawater at a flow rate of 5 mL min⁻¹. The AOCPAN-10%CDs mats exhibited higher uranium selectivity over coexisting ions and adsorption capacity surpassed many reported photothermal-enhanced adsorbents, demonstrating their potential for efficient seawater uranium extraction.