Neutral and small molecules such as boric acid（H 3 BO 3 ）are poorly rejected by state-of-the-art reverse osmosis（RO）and nanofiltration（NF）membranes. Therefore, the objective of this study was to investigate physico-chemical properties of active layers controlling the H 3 BO 3 rejection by polyamide composite RO/NF membranes. To achieve the this objective, we measured the concentration of deprotonated carboxy group（R-COO －）of polyamide active layer of eight commercial RO/NF membranes by probing R-COO － with the Ag ＋ at pH 6.0 and 10.0 and quantifying the Ag ＋ using a Rutherford backscattering spectrometer. We also characterized polyamide active layers using thermal gravimetric analysis. These physico-chemical properties of RO/NF membranes were then used to investigate the relationship with water/H 3 BO 3 transport parameters obtained by modeling experimental data using the solution-diffusion model allowing for the existence of unhindered advection through nano-scale imperfections. It was found that the H 3 BO 3 permeability and water selectivity of RO/NF membranes were most strongly related to the temperature at which 20 ％ weight loss occurs, an indicator of molecular weight of polyamide active layers. Positive correlation, although weak, was also observed with the concentration of R-COO － at pH 6.0. These results indicate that aggregate pores in polyamide active layers play an important role in water and H 3 BO 3 permeation through RO/NF membranes.
We attempted to make an agricultural cultivation solution from seawater with a simple process using Ca-A zeolite. By treating seawater with Ca-A zeolite, the pH of the treated solution became neutral, and the salinity decreased to be about 1/3 because the main elements in seawater, Na ＋ and Cl －, were decreased to be less than half. Although radish sprouts did not grow in seawater, they did grow in the solution obtained from seawater treated with Ca-A zeolite. These results suggest that it is possible to make a solution for agricultural cultivation from seawater using Ca-A zeolite.
Tannic acid（TA）was immobilized onto a glycidyl methacrylate-grafted fiber. The TA-immobilized fiber（TA fiber）with a TA content of 25 ％ was applicable to the collection of vanadium（V）from the spring water of Mt. Fuji. The contact in a batch mode for 1 day of the 1 g TA fiber with 1 L spring water containing V at a concentration of 58 μg-V/L led to collection of 70 ％. The amount of V adsorbed onto the TA fiber was quantitatively eluted with 0.5 M hydrochloric acid. In addition, the amount of V adsorbed remained constant after the third cycle of repeated adsorption and elution of V.
The selective removal of Cl - and SO 4 2- from seawater using Ag- and Pb-exchanged natural zeolites was examined for effective seawater desalination. Japanese clinoptilolite zeolites were treated with AgNO 3 and Pb（NO 3 ） 2 solutions to prepare Ag- and Pb-exchanged natural zeolites. Ag-exchanged natural zeolite can selectively remove Cl - from seawater without any Ag + remaining in the seawater after treatment, while Pb-exchanged natural zeolite can selectively remove SO 4 2- from seawater but Pb 2+ remains in the seawater after treatment.
In this paper, a novel desalination system called circulating diffusion dialysis（CDD）was set up by connecting two stacks using salt bridges, with the stacks consisting of cation-, and anion-exchange membranes and three types of water flow channels of two salt solutions（HS: high salt concentration, LS: low salt concentration）and desalting water（DW）solution. By feeding 30,000 mg/dm 3 NaCl as HS and various initial concentrations of NaCl as LS and DW to the CDD system, the salt concentration of DW decreased to less than 500 mg/dm 3 . In conclusion, we confirmed that the CDD system can desalinate saline water without applying any heat and electrical power from outside; but just by feeding salt solutions with different concentrations into the system.
Our previous study demonstrated that the high-performance liquid chromatographic technique utilizing a plastic tube as a separation field allowed for analysis of amyloid fibrils. The method features the separation of analytes utilizing a polytetrafluoroethylene tube as a separation column, and detection of eluents using a fluorescence detector. In this study, we applied the method to the investigation of the effects of Al3+, Fe3+ and Zn2+ ions on the formation process of amyloid fibrils from hen egg white lysozyme. The increase in the number and intensity of peaks observed in the chromatograms suggests that amyloid fibrillation can be rapidly induced in the presence of metal ions.
In this study, we prepared novel PVA-based cation-exchange membranes having monovalent cation permselectivity by coating one of the membrane surfaces with an aqueous solution of PVA-based block copolymers. To determine the permselectivity between Na+ ions and Ca2+ ions through the membrane, electrodialysis was carried out using a mixed NaCl and CaCl 2 solution. The permselectivity for Na+ ions against Ca2+ ions through the membrane increased with increasing coating concentration while membrane resistance was almost independent of the coating concentration. These results indicate that our modification method can be used to prepare a membrane with high permselectivity for monovalent ions without changing its membrane resistance.