Synthesized Ettringite\nfor Sequestration of Inorganic <sup>14</sup>C from the Waste Solution

Carbon-14 (<sup>14</sup>C), a radionuclide generated\nin a nuclear\npower plant’s operation, is a serious environmental threat\ndue to its long half-life (5730 years) and potential mobility in the\nenvironment. Herein, we present the sequestration behavior of inorganic <sup>14</sup>C as carbonate (CO<sub>3</sub><sup>2–</sup>) and bicarbonate\n(HCO<sub>3</sub><sup>–</sup>) species from a simulated waste\nsolution using synthesized ettringite under various experimental conditions.\nThe ettringite was synthesized via the solution route and characterized\nby XRD, FT-IR, N<sub>2</sub> adsorption/desorption isotherms, and\nFE-SEM/EDS analyses. Synthesized ettringite exhibited an efficient\ninorganic <sup>14</sup>C removal capacity (∼92–94%)\nas compared to CO<sub>3</sub><sup>2–</sup> and HCO<sub>3</sub><sup>–</sup> anions from the waste solution. The mechanism\nfor the sequestration of CO<sub>3</sub><sup>2–</sup> and HCO<sub>3</sub><sup>–</sup> anions from the waste solution using ettringite\nsuggested that the removal of CO<sub>3</sub><sup>2–</sup> and\nHCO<sub>3</sub><sup>–</sup> anions was achieved via ligand\nexchange and framework dissolution–precipitation, respectively.\nTo investigate the <sup>14</sup>C retention capacity onto ettringite,\nthe study also performed desorption experiments in simulated groundwater\n(SGW) and the obtained results suggested that the desorption % of\nboth anions was significantly lowered (7 and 4.5% for HCO<sub>3</sub><sup>–</sup> and CO<sub>3</sub><sup>2–</sup> anions,\nrespectively) in SGW. We believe that our results will be highly significant\nin interpreting the immobilization behavior of dissolved inorganic <sup>14</sup>C as bicarbonate and carbonate anions present in alkaline\nwaste solutions/aqueous environments.