Subjects: Nuclear Science and Technology >> Nuclear Materials and Techniques submitted time 2023-06-18 Cooperative journals: 《Nuclear Science and Techniques》
Abstract： Diffusion behaviors of Se(IV) and Re(VII) in bentonite were investigated by a through-diffusion method in nitrate, sulfate, carbonate and silicate solutions. SEM-EDS analysis showed that Se(IV) was reduced to red precipitate Se(0) by sulfite. Se(IV) was sorbed on bentonite with distribution coefficient Kd of (2.6–5.3)×10-4 m3/kg in sulfite, nitrate and sulfate solutions, whereas it was hardly sorbed in carbonate and silicate solutions. The effective diffusion coefficients were De= (0.81–7.0)×10-11 m2/s for Se(IV) and De= (1.4–4.4)×10-11 m2/s for Re(VII). The De value of Se(IV) exhibited a dependence on the inorganic salts in the order of sulfite ≈ nitrate ≈ sulfate > silicate > carbonate, whereas the salts had insignificant effect on Re(VII) diffusion. The results suggest that the discrepancy in diffusion mechanism may lead to the different impact of the salts on the diffusion of Se(IV) and Re(VII) in GMZ bentonite.
Subjects: Nuclear Science and Technology >> Nuclear Materials and Techniques submitted time 2023-06-18 Cooperative journals: 《Nuclear Science and Techniques》
Abstract： The effect of humic acid (HA) on the diffusion of Re(VII) was investigated in compacted Gaomiaozi (GMZ) bentonite by the through- and out- diffusion method. The effective diffusion coefficient, De, and accessible porosity, acc, were measured in order to evaluate the impact of humic acid on Re(VII) diffusion. The De value was in the range of (5.2–8.3)×10-12 m2/s. The diffusion of Re(VII) was enhanced in the presence of HA, and the De value increased with the increase of ageing time, indicating that the formation of HA-Re complexes was slow. Moreover, the acc was in the range of (0.06– 0.16), which is less than the total porosity. It implies that the HA-Re complexes are anions.
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