Hiroshi Nakamichi

Preparation of water and alkali durable porous glass membrane coated on porous alumina tubing by sol-gel method

Abstract Composite porous glass membranes were prepared by the sol-gel method. A thin porous glass layer, about 2 μm thick, was coated on the surface of the porous ceramic tubing (Al 2 O 3 :99.9 wt.%, pore diameter: 200 nm). The composition of the porous glass layer of the composite membrane was SiO 2 -ZrO 2 . Considering from the fact that the desalination ratio of the feed aqueous NaCl solution (NaCl 0.5 wt.%) was about 90% by use of these membranes, they were defect-free. The best composition of the porous glass layer was 70 SiO 2 -30 ZrO 2 from the standpoint of preparing membranes. These membranes had a large water and alkali durability. These membranes can be expected to apply to recovering dyes and paints from organic solvents and to be used as a gas separation membrane.

Stabilizing effect of the third components on ZnBr2KBrMBr2 glasses

Abstract Glass formation has been examined for ZnBr2KBrMBr2 systems in which M = alkaline earth metals (Mg, Ca, Sr, Ba), and 3d transition metals (Mn, Fe, Co, Ni), and Cd, Pb. The systems of M = Ba, Sr, Ca, and Pb, divalent cations of which have large ionic radii, are vitrified in large composition regions containing MBr2 up to 40 mol% and the devitrification stability increases with increasing MBr2 contents. On the other hand, 3d transition metal bromides with small cationic radii can be contained less than 5 mol% and the glasses are unstable to the devitrification. The ionicity and the softness of M2+ ion are related to the effect of the third component on the stability of the glass against devitrification.

Ion Exchange Ability of Porous Glass

The ion exchange abilities of two kinds of porous glasses with pore diameters of 4 and 48nm was studied in the aqueous solutions of M(NO3)n (M=Li, K, Mg, Ca, Mn, Co, Ni, Cu, Zn, Cr, Fe), and NiX (X=Br2, I2, SO4, (NO3)2, (ClO4)2, C2O4, (CH3CH(OH)COO)2). The ion exchange ability of Fe3+ was high, but that of the other chemical species were also the same. Porous glasses were modified by treatment with trimethylchlorosilane (TMS), γ-aminopropyltriethoxysilane (γ-APTES) and 1, 3-propanesultone (PS). The porous glass treated with TMS had no ion exchange ability. The ion exchange ability of glass treated with PS was three times and by γ-APTES was ten times as high as that of the untreaded glass.

Distribution of Impregnated Component and Nonuniformity of Colloidal Silica in Porous Glass

Porous glass prepared by acid leaching of phase separated glass contains colloidal silica, resulting in the nonunif ormity in the porous glass. Porous glass rods were impregnated with aluminum nitrate solutions, and some of them were treated subsequently with ammonia to precipitate aluminum hydroxide. Then the porous glasses were sintered to form nonporous glasses. The concentration profile of aluminum in the sintered glasses was studied with reference to the nonunif ormity. The aluminum concentration in the impregnated and ammonia-treated specimens was high at the surface region and decreased toward the center. This fact coincides with the distribution of porosity which is high at the surface region. The concentration difference between the as-impregnated and impregnated and ammonia-treated specimens was large at the center and decreased toward the surface, in good correlation with the distribution of the surface area which is high at the center. A narrow gap with a low aluminum concentration was observed at the center of the impregnated specimen and was ascribed to the very densely deposited colloidal silica.