Fabricating polyphosphonic acid-based ion exchanger with spatially symmetric structure for efficient removal of uranium

Effective elimination of uranium (VI) from wastewater is critical to environmental remediation. Herein, a novel polyphosphonic acid-based ion exchanger PDVA/SiO 2 with spatially symmetric structure was designed and fabricated, and its adsorption behavior towards uranium in pH 4 solution was investigated at both mg/L and μg/L concentration levels using batch and column experiments respectively. The adsorbent could rapidly recognize and complex with uranium and reach adsorption equilibrium within 5 min, with the adsorption efficiencies of uranium in pure water, tap water, lake water and seawater were about 99.9%, 98.7%, 96.5% and 71.5% respectively. Uranium could be consistently and efficiently removed using a column separation device, with the concentrations in the purified solution less than 30 μg/L. The adsorption mechanism was dominated by ion exchange between UO 2 2+ and H + (in P–OH). Density functional theory (DFT) calculations demonstrated that the complex formed by the phosphate group with bi-deprotonated binding to UO 2 2+ possessed higher stability, and the binding process was accompanied by charge transfer and energy reduction.