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.

Automated summary

Doping uranium into a stable Fe3O4 lattice structure reduces migration, but the presence of coexisting ions in an aqueous solution affects uranium mineralization efficiency and the stability of uranium-bearing Fe3O4. Calcium incorporation increases the level and stability of doped uranium in Fe3O4 due to strong hybridization effects. Phosphate, however, inhibits Fe3O4 crystallization. These findings offer new possibilities for multi-metal co-doping technologies and optimization in treating uranium-containing complex wastewater.