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The oxygen concentration and inherent Fe in bentonite have a significant influence on the Se(IV) sorption process.In this study,the sorption of selenite on natural bentonite was investigated using a batch experiment method,and the distribution coefficient(K_d)values were obtained in the pH range from 2.0 to 10.0 under oxic/anoxic conditions.The K_d values always reached a maximum value at a pH of 4 under oxic conditions and at a pH of 8 under anoxic conditions;meanwhile,the K_d value under anoxic conditions was larger than the value under oxic conditions,especially in regard to the maximum K_d values.The oxygen conditions have a significant influence on the ratio of redox-sensitive Fe~(2+)/Fe~(3+),which was closely related to the difference in the K_d values under both oxic/anoxic conditions.Ferric selenite and green rust could be responsible for the maximum K_d values under oxic/anoxic conditions.In the leaching experiments,we found that the Fe~(2+) in bentonite could replace Mg~(2+) and Al~(3+) in the octahedral sheet.Spectroscopy methods,such as Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD) and X-ray absorption spectroscopy(XAS) were used to characterize the surface properties of the samples after reaction.Overall,this study shows that the addition of Fe~(2+)-containing materials into backfill/buffer materials under anoxic condition could enhance the sorption of ~(79)Se(IV).
The oxygen concentration and inherent Fe in bentonite have a significant influence on the Se (IV) sorption process. In this study, the sorption of selenite on natural bentonite was investigated using a batch experiment method, and the distribution coefficient (K_d) values were obtained in the pH range from 2.0 to 10.0 under oxic / anoxic conditions. K_d values always reached a maximum value at a pH of 4 under oxic conditions and at a pH of 8 under anoxic conditions; meanwhile, the K_d value under anoxic conditions was larger than the value under oxic conditions, especially in regard to the maximum K_d values. The oxygen conditions have a significant influence on the ratio of redox-sensitive Fe ~ (2 +) / Fe ~ (3 +), which was closely related to the difference in the K_d values under both oxic / anoxic conditions. Ferric selenite and green rust could be responsible for the maximum K_d values under oxic / anoxic conditions. the leaching experiments, we found that the Fe ~ (2+) in bentonite could replace Mg ~ (2+) and Al ~ (3+) in the octahedral sheet.Spectroscopy methods, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) were used to characterize the surface properties of the samples after reaction. Overall, this study shows that the addition of Fe ~ (2 +) - containing materials into backfill / buffer materials under anoxic condition could enhance the sorption of ~ (79) Se (IV).