Potential dependent transport property of BA through a polypyrrole-modified membrane and its selectivity for the organic ions

It is well established that mixture of inorganic ions including heavy metals can be simply separated into components by using a conducting polymer membrane (CPM) system because each component has a unique charge or size of hydrated radius. However, studies about organic ion separations with the CPM system were hardly found even though organic ions are used in so many fields. Unlike inorganic ions, organic ions usually have complex characters can cause some specific interactions with the membrane and the specific interactions can affect their transport. However, in the case that the specific interactions are weak enough, the organic ion transport may be similar to that of inorganic ions. Thus, investigation of the organic ion transport should be done case by case. In this study, we investigated the transport phenomenon of an organic ion which has weak specific interactions with the membrane under different applied potentials and demonstrated its transport mechanism in detail. Benzylamine (BA) was chosen as the transporting ion and the experimental results showed that its transport was similar to that of inorganic ions even though it has different characters with them. In addition, we compared the transport property of BA to that of methylene blue (MB) which has a strong specific interaction with the membrane under same applied potential and suggested a possibility that organic ions could be separated based on the membrane selectivity.