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Aosai, Daisuke*; Saeki, Daisuke*; Iwatsuki, Teruki; Matsuyama, Hideto*
Colloids and Surfaces A; Physicochemical and Engineering Aspects, 495, p.68 - 78, 2016/04
Times Cited Count：1 Percentile：1.66(Chemistry, Physical)The transport of radionuclides by organic colloids in deep groundwater is one of the important issues for the geological disposal of high-level radioactive waste. Because of their low concentration, it is difficult to directly analyze organic colloids in deep groundwater. In this study, hydrodynamic conditions were optimized, and surfaces of nanofiltration membranes were modified using a cationic phosphorylcholine polymer for preventing membrane fouling. Deep groundwater, obtained at the Mizunami Underground Research Laboratory in Japan, was condensed. The recovery yield of the organic colloids in the deep groundwater condensation test at 5-fold condensation was improved from 62% to 92% by the optimized hydrodynamic conditions and membrane surface modification for prevention of membrane fouling. The composition of organic colloids in the condensates was analyzed using pyrolysis gas chromatography coupled with mass spectrometry.
Aosai, Daisuke*; Saeki, Daisuke*; Iwatsuki, Teruki; Matsuyama, Hideto*
Colloids and Surfaces A; Physicochemical and Engineering Aspects, 485, p.55 - 62, 2015/11
Times Cited Count：5 Percentile：11.49(Chemistry, Physical)To analyze organic colloids in deep groundwater, concentration techniques using adsorption resins and reverse osmosis membranes have been widely applied, because their concentrations in deep groundwater are very low and detection of the organic colloids in raw groundwater is difficult. However, these techniques have respective disadvantages such as chemical disturbance and membrane fouling caused by cations. To overcome their disadvantages, we propose a new concentration method using nanofiltration membranes to concentrate organic colloids rapidly without chemical disturbance and to selectively remove monovalent and divalent ions, which may cause inorganic and/or organic fouling. Concentration performance of the NF and RO membranes for aqueous solutions for humic acids was evaluated using a laboratory-scale membrane test unit. The time course of permeate flux and concentration of humic acids were measured. These membranes were applied to the concentration of actual groundwater.
Aosai, Daisuke*; Yamamoto, Yuhei*; Mizuno, Takashi; Ishigami, Toru*; Matsuyama, Hideto*
Colloids and Surfaces A; Physicochemical and Engineering Aspects, 461, p.279 - 286, 2014/11
Times Cited Count：10 Percentile：24.86(Chemistry, Physical)In studies of colloids in deep groundwater, a serious problem exists because the properties of the colloids are influenced by changes in the chemistry of groundwater upon exposure to the atmosphere and pressure release during sampling. Then, ultrafiltration technique, while maintaining in situ hydrochemical conditions was developed. As the result of the investigation using the method at the Mizunami underground Research Laboratory (MIU), different types of colloids consisting of inorganic and organic substances were observed and complex formation between the colloids and REEs was suggested. Furthermore, characteristic partitioning of REEs depending on colloids size was observed in complex natural environments without chemical disturbance. The current findings are useful for understanding migration of radionuclides.
