Evaluation of membrane fouling by electical and surface chemical composition measurements.

Adsorption of charged macromolecules on the surface of a membrane in microfiltration processes produces membrane fouling and, as a result of this, a reduction in the flow across the membrane. Membrane fouling can be easyly detected by variation of: i) electrochemical parameters such as electrical resistance and salt permeability, which are directly related to the porosity of the membrane; ii) atomic concentrations of characteristic elements of the membrane surface, which can be determined by X-ray Photoelectron spectroscopy (XPS). For alumina commercial membranes (Anopore(TM), 0.1 mu m pore size) in contact with salt solutions containing 0.5 g/l bovine serum albumin (BSA), electrochemical parameters indicate a decrease around 50% for membrane porosity. XPS results show: i) the adsorbed layer of protein on the membrane surface does not directly increase depending on the membrane-protein interaction time, since most of it is adsorbed in the first 24 h.; ii) the protein layer does not uniformely cover the alumina membrane surface.