A charged polymer chain was immobilized onto various components and shapes of trunk polymers by radiation-induced graft polymerization and subsequent chemical modifications. The resultant charged graft chain expands or shrinks due to mutual electrostatic interaction among the charged groups in response to the pH and ionic strength of the liquid surrounding the charged graft chain. The charged graft chain immobilized onto a porous hollow-fiber membrane captured proteins in multilayers via multipoint binding. A positively-charged-graft-chain-immobilized, i.e., anion-exchange, porous hollow-fiber membrane was commercialized in 2011 for the removal of undesirable proteins in the purification of pharmaceuticals. On the contrary, a negatively-charged-graft-chain-immobilized, i.e., cation-exchange, porous hollow-fiber membrane exhibited a low permeation flux for pure water; however, pre-permeation of magnesium chloride aqueous solution through the membrane restored the permeation flux because of ionic crosslinking of the graft chains with magnesium ions. The charged graft chains provide a precipitation field of inorganic compounds such as insoluble cobalt ferrocyanide and sodium titanate. The graft chain will entangle or penetrate the precipitate due to electrostatic interaction with the surface charge of the precipitate. Braid and wound filter consisting of insoluble-cobalt-ferrocyanide-impregnated fiber are used for the removal of radioactive cesium ions from contaminated water at the TEPCO Fukushima Daiichi Nuclear Power Plant.

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The thermochemical IS process is a promising hydrogen production method that can produce hydrogen in large amounts and stably with high efficiency by the thermal splitting of water. Research and development on chemical reaction technology with membranes was conducted for the purpose of improving the efficiency of the IS process and application of solar heat. The basic technology of ceramic membranes applied to decomposition reactions of hydrogen iodine and sulfuric acid was developed, and it is expected that the conversion rate on decomposition in each reaction can be remarkably improved. The basic technology of a cation exchange membrane applied to Bunsen reaction was developed with a radiation-induced grafting technique, and it is expected that the amount of iodine can be reduced to about one-fifth compared to the conventional method. These achievements are important technologies for the practical use of the IS process.

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For applications to saline water concentration by electrodialysis, we prepared nano-structure-controlled cation and anion exchange membranes（CEMs and AEMs）by a so-called ion-track grafting technique. This new technique involves irradiation of a polymer substrate with an MeV-GeV heavy-ion beam to form the nano-sized cylindrical ion tracks and the graft polymerization only into the ion tracks for the creation of one-dimensional transport pathways. A 25-μm-thick poly（ethylene-co-tetrafluoroethylene）film was irradiated with 560 MeV ¹²⁹Xe or 310 MeV ⁸⁴Kr at fluences of 3.0×10⁸ －1.0×10⁹ ions/cm². The irradiated films were immersed in grafting solutions of ethyl p-styrenesulfonate（EtSS）and chloromethylstyrene（CMS）, and then subjected to the hydrolysis of EtSS units and quaternization of CMS units to prepare CEMs and AEMs, respectively. These CEMs and AEMs showed lower resistance than the commercially-available membranes even at the very low water uptake. This would be due to the significantly-efficient transport of ions through the unique one-dimensional highly-connected transport pathways. In the saline water concentration experiment, a pair of our CEM and a commercial AEM or vice versa led to a higher salt concentration in the concentration chamber than did a pair of the commercial membranes. This result demonstrated great applicability of our ion-track-grafted CEMs and AEMs for saline water concentration.

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In this review, the production method of commercial IEMs and research stage IEMs prepared using various production methods as well as their membrane structure were introduced. Novel IEMs using an ion track graft polymerization method with high performance were also introduced. Moreover, the principle of ionic transport through a mosaic charged（CM）membrane was explained. Because the cation-exchange and anion-exchange domains of a CM membrane are alternately arranged and these charged domains are passed through the membrane, the membrane shows high electrolyte permselectivity. Here, we have also introduced the preparation methods and the structure of a novel CM membrane prepared using the ion track graft polymerization method. In a piezodialysis system consisting of the CM membrane and two NaCl solutions of 500 ppm, the concentration at the high pressure side increased while that at the low pressure side decreased, indicating that the CM membrane has potential application to desalination of salt solutions with low salt concentrations.

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The harvest of Manila clam Ruditapes phillipinarum has been drastically declining in Japan. One of the reasons is likely due to the nationwide spread of Perkinsus olseni in the clams. Here, we report that a P. olseni infection has occurred in Manila clams on Shodoshima Island facing severe depletion of its natural resources. 132 Manila clams were collected five times in 2016. The percentage of nested PCR-positive clams was 6.7-92.9 ％ from October 22 to December 8. The findings showed that the prevalence of the Perkinsus protozoan infection was different largely depending on the season. 176 Manila clams were collected six times in 2017. The percentage of nested PCR-positive clams was 3.1-17.2 ％ from May 18 to October 25. Among them, the clams with shell length ≤15 mm were included, and the increasing trend in infection intensity was suggested by differences among band intensities of their PCR products. 30 nested PCR products were randomly chosen for sequencing. The obtained sequences were clustered into two genotypes. The maximum likelihood phylogenetic tree based on the ITS1-5.8S rRNA-ITS2 sequences of eight Perkinsus species showed that both genotypes were located in P. olseni/atlanticus clade, and therefore were identified as P. olseni.

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In this study, we used a molecular layer-by-layer （mLbL） deposition technique to synthesize polyamide active layers without nano-scale imperfections. In the first part of this study, the hydrolysis conditions of polyacrylonitrile （PAN） support membranes were optimized. Experimental data showed that the hydrolysis of PAN was favored at higher NaOH concentration. Also, the pressure from the backside of the PAN membrane hindered the penetration of the NaOH aqueous solution into the inside of the PAN membrane, resulting in higher water permeability of the PAN membrane without sacrificing the hydrolysis efficiency at the surface of the PAN membrane. In the second part of this study, the influence of the number of mLbL deposition cycles on the membrane performance was investigated. It was found that water permeability of RO membranes with 5 and 10 mLbL deposition cycles were higher than that of commercial RO membranes investigated in this study. It was also found that the NaCl rejection of RO membranes with 15 and 20 mLbL deposition cycles was higher than that of the commercial RO membrane. Modeling analysis showed that the higher NaCl rejection by RO membranes with 15 and 20 mLbL deposition cycles was due to smaller presence of nano-scale imperfections.

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Regarding the practical application of a reverse electrodialysis （RED） system using seawater and river water, RED performance depends on water temperatures as well as the salinity gradient. In this study, we have evaluated the water temperature dependence of power generation performance of a pilot-scale RED stack with an effective area of 40 m². The generated power linearly increased with increasing water temperature even at different flow rates, and this linear relationship provided a temperature coefficient for the maximum power output of the RED stack. The obtained temperature coefficients were from 1.0 to 2.0 ％/℃（25 ℃ as a standard）, promising to be useful for predicting the power output performance of a practical RED system at various water temperatures.

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