Preparation and Characterization of 18-Crown-6 Modified Cellulose Acetate Membrane in Uni-Univalent Aqueous Electrolyte Solutions

Abstract

In present study, a cellulose acetate/18-crown-6 blend membrane (selective for K⁺ ions) was prepared by the solvent vapourization method. The surface morphology of the modified membrane was characterized by scanning electron microscopy (SEM) analysis, which indicate the smooth and homogeneous membrane surface. The effect of water and electrolyte (KCl and NaCl) concentration on the rate of water sorption and porosity was explained on the basis of physico-chemical parameters i.e. water content and water activity of the membrane phase. The variation of ionic transport number with respect to water activity, i.e. [dt^mK⁺/da^m_w > dt^mNa⁺/da_m^w] has been observed in the present system. The transport of ions under concentration gradient in term of permeability, flow and flux was estimated by membrane/solution conductance-time data. The variations of permeability, flux and flow values with respect to time for K⁺ and Na⁺ ions were found to be different. Membrane water activity (a^m_w) decreases with the increase of external electrolyte concentration. The effective fixed charge density of the membrane increases with increase of external electrolyte concentration. Permselectivity parameter of the membrane in both cases decline with increase of external electrolyte concentration.