Effect of specific adsorption on the electrochemical on/off switching of ion transport

A number of ion separation methods successfully separate ions by controlling the ion's transport. In general, transport rate of ions depends on their charge, size or hydrated radii. However, methylene blue (MB) used in this study showed different transport tendency compared to other ions. The results indicate that the transport of MB is affected by its adsorption property. Thus, we tried to elucidate the special transport mechanism of MB in detail. The conducting polymer modified membrane used in this study was prepared by the electrochemical polymerization of pyrrole on a gold-sputtered polycarbonate (PC) membrane in aqueous solution. Characterization of the polypyrrole (PPy) modified membrane was performed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The transport of MB through the PPy membrane was controlled by applied potentials. The concentration change of MB in permeated cell was detected by high performance liquid chromatography (HPLC) equipped with a UV-Vis detector.