Solvent Permeation Behavior of Alginate Sulfate Electrolyte Membranes under Pressure Gradient
Chikara KATSUNO, Yutaka KASAI, Hideyuki MORITA, Junichi HORINAKA, Kenji URAYAMA and Toshikazu TAKIGAWA
Abstract:We have investigated the flow rate of methanol aqueous solutions through alginate sulfate (AS) electrolyte membranes under a constant pressure gradient. The solvent flow rate for the AS membranes with low cross-linking densities is considerably higher than that of alginic acid membrane when the methanol fraction (ƒÓ) is low. The solvent flow rate drastically decreases as ƒÓ Increases, and no solvent permeation is observed when ƒÓ > 0.6. This strong ƒÓ Dependence of flow rate is not simply explained by the ƒÓ Dependence of swelling degree (ƒ¦), because the reduction in ƒ¦ By increasing ƒÓ Is considerably small. The confocal microscopy reveals a higher order network structure with a mesh size of ca. 10 ƒÊm in the water-swollen AS membrane. The network structure results from the phase separation of the hydrophilic and hydrophobic domains. The hydrophilic and hydrophobic domains are mainly composed of the sulfated blocks and non-sulfated blocks, respectively. The mesh size of the network structure becomes considerably smaller as ƒÓ Increases. The solvent permeability of the AS membranes is mainly controlled by the mesh size of the higher order network structure. Key Words:Alginate sulfate, Permeation behavior, Confocal laser scanning microscopy, Swelling, Electrolyte membrane