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Large amounts of tritium would be handled in D-T fusion power plants. Tritium is the radioisotope of protium, and is easily taken into the human body. With regard to nuclear fusion reactor facilities, the concept of multi-confinement system is applied to prevent tritium leaking to the environment. The last barrier to confine tritium is a building itself containing all equipment and facilities. If a severe accident takes place, tritium gas could leak into the facilities. In order to prevent tritium leaking to the environment, a secure air cleanup system (ACS) needs to be installed in the building. In ACS, the tritium gas, which leaks to rooms by an accident, is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents. This method can remove tritium effectively, whereas which has a problem related to large ventilation force required to overcome high pressure drop in catalyst and adsorbent beds. Ventilation force could be substantially reduced by applying honeycomb catalysts a...

Recovery of tritium released into working areas in nuclear fusion plants is a key issue for safety. A large volume of air in the last confinement of fusion power plants should be processed by air c...

Geothermal water from geothermal plants often contains high levels of boron (B), above the Japanese effluent standard level. To establish an effective utilization system for geothermal resources, boron removal using non-calcined and calcined hydrotalcite was investigated using geothermal water from the Sumikawa geothermal plant in Japan. Calcined hydrotalcite removed large amounts of boron, and changed the solution pH to 12, while non-calcined hydrotalcite removed little boron. Calcined hydrotalcite are also more effectively removed from other anions including Si, As, F−, Cl−, and . The concentrations of boron dropped to below the Japanese effluent standard level of 10 mg L−1 with a 6 h treatment with calcined hydrotalcite. The ability of calcined hydrotalcite to remove boron from geothermal water was almost constant over the temperature range 25–80°C.

We attempted to prepare sulfur-impregnated adsorbent from coal for removal of heavy metals. A two-step process (pyrolysis and sulfur impregnation) was used. Raw coal was rapidly pyrolyzed to prepare char with a high specific surface area. It was sulfurized by H2S impregnation to obtain sulfur-impregnated char that could adsorb heavy metals. Pyrolysis char with high specific surface area can be obtained by rapid pyrolysis; sulfur can be added to rapid-pyrolysis char using H2 gas. Sulfur-impregnated char was more effective for adsorption of Pb2+, Cd2+, and Zn2+ than raw coal, rapid-pyrolysis char, and commercial charcoal.

We attempted to develop a new process to remove NaCl content in seawater using natural zeolite. Na+ in seawater can be reduced by ion exchange of natural zeolite, and Cl− can be reduced by AgNO3 or calcined hydrotalcite. The two-step process, which comprised natural zeolite treatment and anion reduction treatment (AgNO3 or calcined hydrotalcite), was applied to remove NaCl from the seawater. The possibility of cultivation using the obtained solution for the growth test of radish sprouts was then examined. The latter did not grow in the seawater, the solution treated with natural zeolite, the solution treated with AgNO3 after zeolite treatment, and in the solution treated with natural zeolite after AgNO3 treatment, due to the high contents of Cl− and remaining in these solutions. Radish sprouts also did not grow in the solution treated with calcined hydrotalcite because of high pH and high content of Na+ in the solution. By combination of anion reduction treatment using calcined hydrotalcite and zeolite tr...

Thermodynamic and kinetic studies on the adsorption of Cs+ and Sr2+ by Na-exchanged clinoptilolite-rich zeolite rock from Akita (Northern Japan) were performed for the purpose of nuclear waste treatment. The thermodynamic parameters such as selectivity coefficient, thermodynamic equilibrium constant, and standard free energy of exchange were evaluated. These values indicated that the selectivity order was determined as Cs+ > Na+ > Sr2+. In order to discuss the adsorption mechanism of Cs+ and Sr2+ onto Na-exchanged clinoptilolite, the effective diffusion coefficients were calculated and two kinetic models, pseudo-first-order and pseudo-second-order kinetic model, were tested. For all systems studied, chemisorption seems significant in the rate-controlling step, and the pseudo-second-order kinetic model provided the best correlation of the experimental data.

Cryogenic adsorption is effective for the separative recovery of hydrogen isotopes of small concentrations from the bulk helium gas. The authors performed a screening test to find candidate adsorbents for the recovery of hydrogen isotopes from the bulk helium gas at liquid nitrogen temperature. The screening test indicates that a natural mordenite adsorbent has a quite high adsorption capacity for hydrogen under the helium atmosphere. The effect of the ion exchange for the natural mordenite on the adsorption capacity of hydrogen was also investigated using protium and silver as well. With regard to the adsorbent examined in the screening test, the adsorption characteristics of deuterium were also investigated. For the adsorption of deuterium, it was found that the natural mordenite adsorbent have a high adsorption capacity. The isotope effect on the adsorption of hydrogen isotopes on the natural mordenite adsorbent is not large compared with the MS5A adsorbent.

We describe the synthesis of zeolite-A using rice husk ash (RHA)as starting material. Synthesis comprised alkali activation at low temperature (

Paper sludge ash (PSA) typically has a low Si abundance and significant Ca content due to the presence of calcite fillers. Acid leaching with HCl was used to reduce the Ca content so that a zeolitic product with a high cation exchange capacity (CEC) could be synthesized. Zeolitic products were synthesized from raw ash and leached ash through reaction with 2.5 M NaOH solution at 80°C. In the case of the original ash without acid leaching, the concentration of Al in the alkali solution always exceeded that of Si during the synthesis, and hydroxysodalite with a low Si/Al ratio (1:1) was formed. In the case of the leached ash, the concentration of Si always exceeded that of Al during the synthesis, and zeolite-P with a higher Si/Al ratio (5:3) was formed. Hydroxysodalite and zeolite-P crystallization was saturated after 6 h of reaction, and the product from leached ash had a higher CEC (approximately 150 cmol/kg) than that from original ash (approximately 40 cmol/kg). Both the decrease in the Ca phase in the ...

The objective of this study was to investigate the synthesis of zeolites from paper sludge ash, and to evaluate their applications for water purification to simultaneously remove NH4+ and PO43- in aqueous solution. Paper sludge ash had a low abundance of Si and a significant Ca content, due to the presence of calcite that was used as paper filler. Na2SiO3 was added to the NaOH solution to increase Si content in order to synthesize zeolites with high cation exchange capacity. The original ash without addition of Si yielded hydroxysodalite with a cation exchange capacity of ca. 50 cmol/kg. Addition of Si to the solution yielded Na-P1 (zeolite-P) with a higher cation exchange capacity (ca. 120 cmol/kg). The observed concentrations of Si and Al in the solution during the reaction explain crystallizations of these two phases. The product with Na-P1 could simultaneously remove NH4+ and PO43- from the solution between pH 4 and 9.