Sunlight-induced uranium extraction with triazine-based carbon nitride as both photocatalyst and adsorbent

[Display omitted] •A sunlight-driven photocatalysis-assisted extraction (SUPER) method was developed.•A bifunctional material CN550 was synthesized with molten salt method.•CN550 showed much improved adsorption and photocatalytic activity than g-C3N4.•The uranium extraction capacity could reach 1057 mg g−1 in spiked real seawater.•The SUPER method could work at natural sunlight illumination. Extracting uranium from high salinity seawater at ultralow concentrations would beneficially contribute to the sustainable utilization of nuclear energy, but it poses a significant challenge. Here we report a sunlight-driven photocatalysis-assisted extraction (SUPER) method by utilizing a bifunctional carbon nitride material, CN550, which has shown about a tenfold improvement in both adsorption capacity and photocatalytic activity compared to g-C3N4. Uranyl ions could be captured on the surface of CN550, and then deposited as metastudtite nanoparticles with light illumination. Compared with the pure physicochemical adsorption (PA) method, a tenfold higher uranium extraction capacity, up to 1556 mg g−1, has been attained. Additionally, a 25 times improvement of the partition coefficient (PC), from 0.312 to 7.778 L g−1, has also been achieved. In spiked real seawater, the extraction capacity can still achieve more than 1000 mg g−1, and the SUPER method has been found to work under natural sunlight illumination as well.