INFLUENCE OF ELECTROLYTE ON ELECTRICAL-PROPERTIES OF THIN CELLULOSE-ACETATE MEMBRANES

The electrical behavior of thin cellulose-2.5-acetate membranes for ch emical semiconductor sensor applications was investigated. The influen ce of electrolyte on the electrical membrane properties was studied by means of electrochemical impedance spectroscopy. The polymeric membra nes can be described using the electrical model of Cole and Cole. The membrane-electrolyte distribution equilibria were investigated by mean s of an absorption-desorption method using conductivity measurements. The desorption kinetics for thin cellulose acetate membranes differ si gnificantly from those of thicker cellulose acetate reverse osmosis me mbranes because here the rate of the ionic exchange at the membrane in terface cannot be neglected. The experimentally determined distributio n coefficients were used for the discussion of the electrolyte influen ce on the electrical membrane parameters. A functional dependence was found between the specific membrane resistance of cellulose acetate me mbranes and the ionic hydration enthalpy. The effect of electrolyte on the relative permittivity can be explained by a theoretical model. (C ) 1994 John Wiley & Sons, Inc.