佐伯 誠一; 柴田 卓弥; 保科 宏行; 植木 悠二; 笠井 昇; 瀬古 典明
日本イオン交換学会誌, 25(4), p.170 - 175, 2014/11
After Fukushima Daiichi Nuclear Power Plant accidents, a lot of contaminated wastes have been produced by decontamination works at contaminated areas around Fukushima prefecture, Japan. At some temporary storage sites, it was found that contaminated leaching water was accumulated under stacks of contaminated "plant" wastes. To handle the wastes and the solution properly, decontamination tests of the leaching water were examined with molybdophosphate type cesium adsorbents synthesized by radiation-induced grafting method. At batch adsorption tests, 75% of radioactive cesium was successfully removed with cesium adsorbents. At column adsorption tests, radioactivity concentration of the leaching water could be reduced under provisional limit value up to around 500 times volume as large as an adsorbent volume. For development of volume reduction method of contaminated plant wastes, radioactive cesium extraction tests from the wastes and removal tests from the extracts were executed using contaminated oil cakes of sunflower seeds as a model of contaminated plant wastes. As a result, 65% of radioactive cesium was successfully extracted from the oil cakes to liquid phase, and more than 65% of radioactive cesium could be collected from the extract by grafted cesium adsorbents. These results showed a possibility of an application of these processes to volume reduction method for contaminated plant wastes.
林 菜月*; 保科 宏行; 天田 春代; 山延 健*; 瀬古 典明
日本イオン交換学会誌, 25(4), p.105 - 108, 2014/11
A fibrous phosphoric acid adsorbents for scandium were synthesized by radiation graft polymerization of glycidyl methacrylate (GMA), subsequent chemical modification, and direct grafting with a phosphoric monomer having both vinyl and phosphoric groups onto a polypropylene coated by polyethylene nonwoven fabric. The resultant grafted fibrous phosphoric acid adsorbent (HMP-g) having long side grafted chains has high affinity for scandium (Sc) ions even under the coexistence with Fe ion. The breakthrough capacity for Sc of 0.5 ppm with Fe coexistence was 10.9 mol-Sc per kg-adsorbent for the GMA derivative phosphoric adsorbent, and 17.8 mol-Sc per kg-adsorbent for HMP-g, respectively.
保科 宏行; 笠井 昇; 天田 春代; 高橋 牧克*; 田中 和也*; 瀬古 典明
日本イオン交換学会誌, 25(4), p.248 - 251, 2014/11
An adsorbent for Scandium (Sc) recovery was developed with radiation-induced graft polymerization of phosphoric acids that have a high affinity for Sc onto polyethylene fabrics. The adsorption performance of Sc was evaluated with the Sc adsorption equipment, consisting of 155 mm internal diameter columns and a pump that were set up near Yukawa River in Kusatsu town. To achieve a practical use of Sc recovery, the adsorbent requires repeated use with maintaining its efficiency in terms of cost reduction. So, the reusability of the adsorbent was investigated by repeating adsorption and elution. The breakthrough curves of Sc adsorption showed similar behavior in all tests. The adsorbed Sc from the 19th adsorption test was 56 mg, which was comparable capacity to the average amount of the adsorbed Sc during the 19 tests. These results indicated that the adsorbent was used more than 19 times with maintaining high adsorption performance of Sc.
天田 春代; 高橋 牧克*; 保科 宏行; 瀬古 典明
日本イオン交換学会誌, 25(4), p.109 - 113, 2014/11
A large amount of arsenic waste solution which was dissolved in neutral aqueous media, was generated from the manufacturing process of gallium arsenide component in semiconductor industry. As for arsenic removal, an adsorbent was developed by radiation graft polymerization and subsequent chemical modification with N-methyl-D-glucamine (NMDG) as a functional group. Furthermore, the grafting and the modification were carried out using water based solvent instead of organic solvent in view of an environmental emission and a working environment. The solvents were comprised of water and surfactant, and the adsorption performances compared with a conventional method synthesized in 1,4-dioxane of organic solvent. Total amount of arsenic for arsenic(III) and arsenic(V) at pH 6.5 were 3.2 times and 2.1 times higher than our previous fibrous adsorbent. From the pH dependency studies, the developed grafted adsorbent gave high removal ratio in a neutral media area for both arsenic species. Breakthrough capacities in the column mode tests for arsenic(III) and arsenic(V) were 0.3 and 18 mg/g at pH 6.5, respectively.
植木 悠二; 佐伯 誠一; 瀬古 典明
日本イオン交換学会誌, 25(4), p.99 - 104, 2014/11
The dynamic adsorption/elution properties of an ethyl p-styrenesulfonate (EtSS)-based fibrous graft adsorbent having sulfonic acid (SOH) groups were evaluated by column-mode adsorption/elution tests for various cations. The EtSS-based fibrous graft adsorbent could work to capture various cations rapidly even under high flow rate conditions, compared with a commercial granular resin. The reason for this difference of adsorption rates was thought to be that the target ions were easily and rapidly transported near the SOH groups of graft chains by fluid convection. The affinity order of the fibrous graft adsorbent for cations depended on the cationic size and valence. It was found that the EtSS-based fibrous graft adsorbent preferentially adsorbed more multiply-charged cations having a larger cationic radius. The adsorbed cations could be easily eluted and concentrated by 1 M HNO aqueous solution, and the recovery of each cation was reached over 90%. Based on the above results, it was found that the EtSS-based fibrous graft adsorbent could be available as a sophisticated metal adsorbent in the industrial processes.
山田 裕久*; 横山 信吾*; 渡部 雄二郎*; 鈴木 正哉*; 鈴木 伸一; 八田 珠郎*
日本イオン交換学会誌, 25(4), p.207 - 211, 2014/11
We investigate the Cs-adsorption behavior of weathered biotites collected from Domiki, Mankei, Tozawa, and Yatsuzaku (in Fukushima) by changing the initial concentration of Cs in a solution. The degree of weathering of the samples increased in the following order: Domeki sample Tozawa Mankei Yatsuzaku. A characteristic feature of the Domeki sample was distortion of the biotite layer. The Tozawa sample had an even greater degree of distortion of the biotite layer. In the Mankei sample, hydrobiotite and randomly interstratified biotite-vermiculite were observed with distorted biotite. The Yatsuzaku sample contained vermiculite with hydrobiotite and distorted biotite. The Cs adsorption ratio was associated with the initial Cs concentration of the solution. The Cs adsorption ratio of samples in an initial solution of 1 to 100 ppm Cs was about 99%; it decreased with increasing Cs concentration in the solution. Dependency of Cs adsorption behavior on the degree of weathering of biotite was clearly observed in the Cs concentration range of 300 to 1000 ppm. With increasing degree of weathering, the rate of decrease in Cs adsorption ratio with increasing initial Cs concentration in the solution became slower and the maximum amount of Cs adsorbed by the sample increased. These results confirm that weathered phyllosilicates, vermiculite, interstratified biotite-vermiculite, and distorted biotite play important roles in Cs adsorption.
柴田 卓弥; 瀬古 典明; 天田 春代; 笠井 昇; 佐伯 誠一; 保科 宏行; 植木 悠二
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It is important task for recovering of Cs from the contaminated area caused by the accident at the Fukushima Daiichi Nuclear Power Station. Therefore, we developed a new grafted Cs adsorbent, which contained a crosslinked structure onto the grafted chains to stabilize the adsorption ligand for applying to a drinking water. As the optimal synthesis condition, 1 mol% of 9G (G: dimethacrylate) which is a type of polyethylene glycol dimethacrylate (PEGDM) was used for Cs adsorbent as a crosslinker. The resultant grafted Cs adsorbent could work to maintain the performance of Cs removal from pH 5.8 to 8.6 without any damage. Finally, the developed Cs adsorbent could use as a filter of a water purifier.