Enhanced mechanism of calcium towards uranium incorporation and stability in magnetite during electromineralization

Doping uranium into a room-temperature stable Fe3O4 lattice structure effectively reduces its migration. How-ever, the synergistic or competitive effects of coexisting ions in an aqueous solution directly affect the uranium mineralization efficiency and the structural stability of uranium-bearing Fe3O4. The effects of calcium, carbonate, and phosphate on uranium electromineralization were investigated via batch experiments and theoretical cal-culations. Calcium incorporated into the Fe3O4 lattice increased the level and stability of doped uranium in Fe3O4. Uranium and calcium occupied the octahedral and tetrahedral sites of Fe3O4, respectively; the formation energy was only-10.23 eV due to strong hybridization effects between Fe1s, U4f, O2p, and Ca3d orbitals. Compared to the uranium-doped Fe3O4, uranium leaching ratios decreased by 19.2 % and 48.9 % under strongly acidic and alkaline conditions after 120 days. However, high concentrations of phosphate inhibited Fe3O4 crystallization. These results should provide new avenues for the development of multi-metal co-doping tech-nologies and mineralization optimization to treat uranium-containing complex wastewater.