U(VI) removal efficiency by the oxidation of Fe(II) under the only injection of O2 and co-injection of CO2 and O2

Abstract

Batch experiments were carried out to investigate the U(VI) removal efficiency by the oxidation of Fe(II) under the only injection of O2 and co-injection of CO2 and O2. Experiment results show that under the only injection of O2, the synergistic effect of Fe(II) and O2 could effectively remove U(VI) from the solution. For the different initial concentrations of Fe(II) at 2, 5, 10, 25, 50, 100 mg/L, almost all the removal rates of U(VI) reach up to 90% in the neutral conditions. There is no inevitable correlation between the removal efficiency of U(VI) and the initial concentration of Fe(II), revealing that the coprecipitation of U(VI) with Fe-oxides plays a dominant role in the removal of U(VI) rather than the simple sorption to the surface of Fe-oxides. Under the co-injection of CO2 and O2, the generated carbonate ions have a significant effect on the removal efficiency of U(VI) by the synergistic effect of Fe(II) and O2. The removal efficiency of U(VI) increases with the initial concentration of Fe(II). In the presence of carbonate ions, U(VI) is easy to bind with HCO3- to form uranyl carbonate complexes such as UO2(CO3)20 and UO2(CO3)42-, which would hinder the process of sorption and co-precipitation of U(VI) with Fe-oxides.