Zhao, Q.*; Saito, Takeshi*; Miyakawa, Kazuya; Sasamoto, Hiroshi; Kobayashi, Taishi*; Sasaki, Takayuki*
Journal of Hazardous Materials, 428, p.128211_1 - 128211_10, 2022/04
The influence of humic acid and its radiological degradation on the sorption of Cs and Eu by sedimentary rock was investigated to understand the sorption process of metal ions and humic substances. Aldrich humic acid (HA) solution was irradiated with different doses of gamma irradiation using a Co-60 gamma-ray source prior to the contact between the metal ions and the solid sorbent. The HA molecule decomposed to smaller molecules with a lower complexation affinity. Batch sorption experiments were performed to evaluate the effect of gamma-irradiated HA on the sorption of Cs and Eu ions. The addition of non-irradiated HA weakened the sorption of Eu because of the lower sorption of the neutral or negatively charged Eu-HA complexes compared with free Eu ions. The sorption of monovalent Cs ions was barely affected by the presence of HA and its gamma irradiation. The concentration ratio of HA complexed species and non-complexed species in the solid and liquid phases was evaluated by sequential filtration and chemical equilibrium calculations. The ratios supported the minimal contribution of HA to Cs sorption. However, the concentration ratio for Eu in the liquid phase was high, indicating that the complexing ability of HA to Eu was higher than that of HA to Cs ions. Therefore, the sorption of free Eu would predominate with the gamma irradiation dose applied to the HA solution under a radiation field near the HLW package.
Fueda, Kazuki*; Takami, Ryu*; Minomo, Kenta*; Morooka, Kazuya*; Horie, Kenji*; Takehara, Mami*; Yamasaki, Shinya*; Saito, Takumi*; Shiotsu, Hiroyuki; Onuki, Toshihiko*; et al.
Journal of Hazardous Materials, 428, p.128214_1 - 128214_10, 2022/04
Kozai, Naofumi; Sato, Junya; Osugi, Takeshi; Shimoyama, Iwao; Sekine, Yurina; Sakamoto, Fuminori; Onuki, Toshihiko
Journal of Hazardous Materials, 416, p.125965_1 - 125965_9, 2021/08
Guo, B.*; Xiong, Y.*; Chen, W.*; Saslow, S. A.*; Kozai, Naofumi; Onuki, Toshihiko*; Dabo, I.*; Sasaki, Keiko*
Journal of Hazardous Materials, 389, p.121880_1 - 121880_11, 2020/05
Yin, X.; Zhang, L.*; Meng, C.*; Inaba, Yusuke*; Wang, X.*; Nitta, Ayako; Koma, Yoshikazu; Takeshita, Kenji*
Journal of Hazardous Materials, 387, p.121677_1 - 121677_10, 2020/04
Sato, Junya; Shiota, Kenji*; Takaoka, Masaki*
Journal of Hazardous Materials, 385, p.121109_1 - 121109_9, 2020/03
Lead is a hazardous heavy metal that can be stabilized by incorporation into the matrix of aluminosilicate bearing phases as they solidify. The actual mechanism by which lead is stabilized, however, continues to be unclear because the individual mechanisms of Pb incorporation into crystalline and amorphous aluminosilicate phases have not yet been studied separately. A detailed investigation of the incorporation of Pb into the amorphous phase of aluminosilicate solids was therefore performed. Amorphous aluminosilicate solids were synthesized with 0.7, 1.5, and 3.7 wt% of Pb from aluminosilicate gel produced from chemical reagents. Based on Raman spectroscopy, the Si-O stretching vibration bond shifted to lower wavenumbers with increasing Pb concentration. This shift suggested that covalent bonding between Pb and O in the matrix of the aluminosilicate solids increased. In addition, sequential extraction revealed that most of the Pb (75-90%) in the aluminosilicate solids was in a poorly soluble form (i.e. reducible, oxidizable, and residual fractions). These findings indicate that most of Pb is bonded covalently to the amorphous phase in aluminosilicate solids.
Tokunaga, Kohei; Kozai, Naofumi; Takahashi, Yoshio*
Journal of Hazardous Materials, 359, p.307 - 315, 2018/07
In the present study, we looked at the removal efficiency of Sr by using barite (BaSO) under various experimental conditions to develop techniques for the direct removal of Sr from seawater. The uptake of Sr by barite was found to be dependent on pH, saturation state, and [Ba]/[SO] ratio in initial aqueous solution, showing that most of the aqueous Sr can be removed from the aqueous solution by adjusting these parameters. However, the effects of ionic strength and competitive ions were negligible, suggesting the effectiveness of its application to removal of Sr from seawater. Batch experiments were also conducted in a seawater system, and a rather high removal efficiency of Sr from seawater (more than 90%) was achieved. Considering its high removal and retention efficiency of Sr in seawater systems, barite is a reliable material for the removal of Sr from seawater.
Awual, M. R.; Yaita, Tsuyoshi; Suzuki, Shinichi; Shiwaku, Hideaki
Journal of Hazardous Materials, 291, p.111 - 119, 2015/06
Awual, M. R.; Yaita, Tsuyoshi; Taguchi, Tomitsugu; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro
Journal of Hazardous Materials, 278, p.227 - 235, 2014/08
Awual, M. R.; Kobayashi, Toru; Miyazaki, Yuji; Motokawa, Ryuhei; Shiwaku, Hideaki; Suzuki, Shinichi; Okamoto, Yoshihiro; Yaita, Tsuyoshi
Journal of Hazardous Materials, 252-253, p.313 - 320, 2013/05