Influence of roughness of microfiltration membranes in Electrical Impedance Spectroscopy measurements.

D. DIAZ; N. A. OCHOA; L.PALACIO; P. PRADANOS; F. J. CARMONA; A. HERNANDEZ

Valencia

Congreso; Euromembrane 2018; 2018

Universidad Politecnica de Valencia

The Electrical Impedance Spectroscopy (EIS) is a technique which is very used tocharacterize membranes. It has been used for the determination of conductivity ofionic solutions inside pores. In order to use this technique, a pore model needs to beassumed to assign an equivalent electric circuit. The simplest way to affront this is toassume the membrane pores are taken as a bunch of parallel cylinders. This wouldcorrespond to an equivalent circuit formed by a resistance in parallel to a capacitor(parallel R-C circuit). This circuit would give a perfect semicircle in the Nyquistdiagram. Nevertheless, most experimental results show flattened lobes caused by asuperposition of slightly different relaxation times.In this work, we propose an explanation of such detected flattening based on themembrane roughness. This roughness is reproduced on the electrodes when liquidmetal electrodes of Hg are used. On the other hand, roughness and the correspondingfractal dimension from Atomic Force Microscopy (AFM) measurements wereevaluated. This fractal dimension was compared with that obtained from EISexperiments, by fitting the Nyquist lobe to a constant phase element (CPE), Díaz etal.(2018).