An experimental investigation of streaming potentials through homogeneous ion-exchange membranes

Streaming potentials through homogeneous ion-exchange membranes (IEMs) were studied with several anion-exchange membranes prepared in our laboratory. Discussions are mainly concentrated on the effects of the chemistry, concentration and pH of the outer solution as well as the thickness and ion-exchange capacity of the IEMs. Results show that except for the membrane thickness hardly affecting the streaming potential coefficient, the remaining factors influence it more or less. The difference of the streaming potential coefficient for different electrolyte solutions with equal concentrations is due to different mobilities of the cations or anions of those electrolytes; the pH of outer solution only alters the magnitude of the streaming potential coefficient, but has no influence on its sign; and the streaming potential coefficient increases with increasing IEC and with decreasing concentration of the outer solution. The desalination rate of the IEMs can be also roughly estimated by the difference of the electrical potential in two opposite pressure directions including the pressure-increase direction (+) and the pressure-reduced direction (−).