Tadao Hakushi

Active transport of transition metal ions through poly(vinyl alcohol) and poly(acrylic acid) blend membrans.

Water-insoluble PVA-PAA membranes were prepared by casting method from poly (vinyl alcohol), poly (acrylic acid) and formaldehyde. The transport behaviors of transition metal ions through the membrane were investigated under various conditions.Transition metal ions were actively transported through the PVA-PAA membrane against their concentration gradient from alkaline side (source phase) to acidic side (receiving phase). The high transport ratio for Cu2+ was maintained for a long time, and the transport from neutral side to acidic side was not observed. It is interesting to note that the active transport was observed even when pH of receiving phase is in a range of neutrality. The rate of active transport depends strongly on pH of the source phase of metal ions rather than pH of the receiving phase. On the other hand, the transport through PVA membrane was negligibly small.Although the separation factor is approximately constant for the PAA content in the PVA-PAA membrane, the premselectivity coefficient and the transport rate of metal ions varied with PAA content. When the PAA content in the membrane is about 10 mol%, Cu2+ was most selectively transported. For the competitive transport of transition metal ions, the transport selectivity is in following order : Cu2+>Ni2+=Zn2+>Co2+.

Studies on the Ion Exchange Membranes. III. Permselectivity of Hydroxide and Sulfate Ionthrough Anion Exchange Membranes

陰イオン交換膜に対する硫酸イオンと水酸イオンの選択透過性を調べるために,硫酸ナトリウムと水酸化ナトリウムの混合溶液について,電解濃縮法により実験を行なった。その結果,ここで用いた陰イオン交換膜に対する硫酸イオンの通りやすさは,水酸イオンに比べて約1/10～1/20で非常に通り難いことがわかった。また,原液中の水酸イオン濃度が低く,電流密度が高いほど,硫酸イオンの透過性が増大する傾向が認められたが,この現象は陰イオン交換膜中での水酸イオンの当量分率が低下するためだと考えられる。