Phosphonic Acid-Functionalized Mesoporous Carbon for Efficient Removal of Uranium from Highly Acidic Waste Streams

To address the challenge of efficiently removing uranium from strongly acidic nuclear waste liquids, this study developed a solvothermal in situ polymerization method to graft phosphonic acid groups onto the surface of ordered mesoporous carbon CMK-3, yielding the novel adsorbent CMK-3/P(DMVP) (dimethyl vinyl phosphonate, DMVP). This material exhibits superior uranium adsorption performance, achieving a maximum adsorption capacity of 117.2 mg·g–1 in 4 mol·L–1 nitric acid solution, with exceptional selectivity against various coexisting ions. Notably, the adsorption performance is governed by a trade-off between phosphonic acid group density and mesoporous structure integrity, with CMK-3/P(DMVP)-3 striking the optimal balance. The adsorption process follows pseudo-second-order kinetics and the Langmuir isotherm model, maintaining stable adsorption capacity after 5 cycles. SEM-EDS and XPS analyses indicate that uranium adsorption primarily occurs through coordination between U(VI) and the P═O group in the phosphonic acid moiety. Combining high capacity, robust acid stability, and excellent reusability, this adsorbent provides an efficient solution for uranium separation and recovery from strongly acidic nuclear waste streams.