Phosphate-modified hydrothermal biochar: Green and efficient uranium adsorption

•Green and low-energy solvent thermal polymerization strategy.•Environmental value and economic potential of biomaterials adsorbents.•Interaction of −PO4 groups with U(VI) is critical for adsorption.•Hydrothermal mesoporous carbon materials grafted with phosphate for efficient removal of hexavalent uranium. Green and efficient treatment of low-concentration uranium-contaminated water caused by uranium mining and recycling risks of depleted fuel is one of the focus issues in the field of nuclear materials. This study addresses the efficient treatment of low-concentration uranium-contaminated water using phosphate-modified hydrothermal biochar (PHBB) derived from waste bamboo. BET reveals that the modified PHBB has a larger specific surface area, increasing the probability of contact with U(VI). FT-IR, XRD and XPS confirm the successful embedding of the phosphate component with increased active sites and specific chemical complexation with U(VI). The adsorption capacity of PHBB for U(VI) at pH 4 is 157.79 mg L−1, significantly higher than unmodified biochar (48.54 mg L−1), following Langmuir isotherm and pseudo-second-order kinetics. This research offers a green, cost-effective approach to radioactive pollutant adsorption.