Electrical impedance spectroscopy characterisation of conducting membranesI. Theory

An electrical impedance spectroscopy (EIS) method for measuring changes in the electrical properties of synthetic membranes is investigated as a possi ble way of monitoring, in situ, the separation performance of these membran es including membrane fouling. Unlike other EIS methods, which require trad itional electrodes in the feed and permeate solutions, alternating current is injected directly into the membrane via external electrical contacts wit h the edges of the membrane. A metal layer sputtered onto the surface of th e membrane can be used to enhance its conduction properties. The impedance models of these systems is shown to be sensitive to membrane surface proper ties, including porosity, as well as electrical properties of solutions and the interfacial regions between the membrane surfaces and the solutions. T he investigation indicates that fouling along the surface of the membrane m ight be more readily detectable than inside the pores. (C) 2002 Published b y Elsevier Science B.V.