New approach to a collodion membrane composite via fluorocarbon polymer (Nafion) blending in terms of a diffusion coefficient of redox substances and transport properties

Nafion (fluorocarbon polymer) and collodion blended with Nafion in the ratio of CN5:5 composite solutions were used to produce thin membrane films on Au electrodes. It was found that the transport properties of water and KCl, such as the filtration coefficient, Lp, reflection coefficient, σ and salt permeation, ω, across the two composite collodion (C) and Nafion (N) membranes depended on the quantities of the Nafion component. Moreover, the study indicated that a better diffusion coefficient of redox substances can be achieved by blending the Nafion solution with an ionic group to collodion solution compared to Nafion only. The uptake of neutral species of ferrocenedimethanol (FcDM), positively charged species of methyl viologen (MV2+), and negatively charged potassium ferrocyanide [Fe(CN)6]4− ions were studied by cyclic voltammetry and chronopotentiometry. The diffusion coefficient of MV2+ and FcDM in blended Nafion:collodion showed higher values compared to that in Nafion alone. The diffusion of positively charged species, MV2+, was decreased in the membrane matrix compared to the neutral species, FcDM. This may be attributed to the existence of an interaction between SO3− functional groups of the fluorocarbon polymer and MV2+ that led to mobility restriction of MV2+ compared to FcDM. The diffusion of the [Fe(CN)6]4− species was not clearly observed due to the electrostatic repulsion effect between SO3− functional groups of the flourocarbon polymer and the negative species, [Fe(CN)6]4−.