Efficient uranium biosorption by marine diatom Phaeodactylum tricornutum from simulated seawater: performances and mechanism

Abstract

Nuclear power stands as a linchpin in decarbonization efforts, primarily due to its dense energy output per unit and the virtual absence of emissions when operational. Exploiting the vast uranium reserves in the ocean is crucial for overcoming land resource scarcity and providing a sustainable, long-term solution. This research aimed to evaluate the adsorptive capacity of a novel marine-derived diatom species, Phaeodactylum tricornutum, for low-concentration uranium in simulated seawater. Biosorption results across varying experimental conditions demonstrate that Phaeodactylum tricornutum exhibits outstanding uranium adsorption capacity (q_max = 13.67 mg g⁻¹). Additionally, Phaeodactylum tricornutum sustained exceptional uranium (U(VI)) selectivity and demonstrated favorable reusability in aqueous solution systems. A chemisorption process featuring uniform monolayer adsorption was corroborated by the pseudo-second-order and Langmuir model fittings. Thermodynamic analysis revealed that the adsorption process was spontaneous, endothermic, and characterized by increased randomness. The dominant adsorption mechanism was identified as coordination between uranyl ions and hydroxyl, carboxyl and amino groups. Owing to its abundant sources, easy accessibility, eco-friendliness and recyclability, the marine diatom Phaeodactylum tricornutum demonstrates significant promise for application in seawater uranium extraction.