Electrophoretic Deposition Mechanism of Zeolite Powder in N-Propanol under Constant Voltages

抄録

Zeolite has been recognized as one of the materials used for inorganic membranes. To improve the reproducibility of preparation and high permselectivity, the seed technique has been applied to the zeolite membrane under hydrothermal synthesis. Here, electrophoretic deposition (EPD) mechanism of zeolite (A-4) powder, as with the fabrication of the separation membrane, has been investigated under constant applied voltages as one of seed crystal coating techniques. Zeolite- n-propanol suspension is used as the EPD bath. The potential gradient in the n-propanol depended on the distance between the electrodes and the applied voltages. The zeta potential of zeolite particles was -26.5 mV in n-propanol and the resistibility of the EPD bath decreased by dispersing zeolite powder. On the other hand, potential gradient in the bulk EPD bath was constant with the progress of EPD, and the actual working potential gradient decreased 35% against the applied potential and electrode distance. Moreover, current density was constant with the progress of EPD, and the deposition layer in the EPD bath had low resistivity. Therefore, the velocity of zeolite particles was constant in the progress of EPD and the amount of deposited zeolite powder increased linearly against the deposition time and applied voltage. In addition, EPD efficiency is approximately 80% up to the amount of deposit at 25 g/m². EPD is a useful technique for the coating of zeolite particles onto substrates because deposition can be easily controlled and it has high deposition efficiency.