Highly Efficient Removal of Barium(II) from Nuclear Wastewater by Calcined Magnesium-Aluminum Layered Double...

Radioactive Ba²⁺ poses significant risks to nuclear safety and environmental protection, yet its efficient removal from nuclear wastewater remains a considerable challenge. Herein, Mg-Al layered double hydroxides (LDHs) were synthesized via a co-precipitation method and systematically optimized by tuning the Mg/Al molar ratio and calcination temperature. The optimal material, obtained by calcining Mg-Al LDH with a Mg/Al ratio of 4:1 at 450 °C (denoted as HT-450), exhibited a high apparent Ba²⁺ uptake capacity of 416 mg g^-1 and reached equilibrium within 15 min. Structural and spectroscopic analyses indicate that Ba²⁺ immobilization is more appropriately described as a reconstruction-coupled, interfacially mediated mineralization process, in which insoluble BaCO₃ forms in close association with the reconstructed HT-450 surface rather than through simple reversible adsorption or ion exchange. HT-450 also exhibited stable performance over a wide pH range of 3-7, high selectivity toward Ba²⁺ in the presence of competing mono-, di-, and trivalent cations, and excellent radiation tolerance, retaining approximately 95% of its initial uptake capacity after exposure to 200 kGy high-energy electron irradiation. These results demonstrate that HT-450 is a promising candidate for the rapid and stable immobilization of Ba²⁺ from Ba-containing radioactive wastewater.