Metal ion transport through a polystyrene-based cobalt arsenate membrane: application of irreversible thermodynamics and theory of absolute reaction rates

Abstract

Polystyrene-based cobalt arsenate membranes have been prepared by sol–gel method for various 1:1 electrolytes (KCl, NaCl and LiCl) at different concentrations. The conductance values of cobalt arsenate membranes have been found to increase with increase in concentration (0.1 ≤ c (M) ≤ 0.01) as well as temperature (10–50) ± 0.1 °C. The conductance values of the investigated electrolytes have been found to follow the sequence K+ > Na+ > Li+. The larger the positive hydration of ions, the higher the activation energies of conductivity of the salt and the sequence for energy of activation followed this order: Ea K+ > Ea Na + > Ea Li+. The changes of Gibbs free energy (ΔG), entropy (ΔS), and enthalpy (ΔH) for the transition of ions from one quasi-equilibrium state were calculated at different concentrations.The values of ΔH, ΔG and ΔS were found to be positive and negative respectively. Among the ions of the same valence the order of ΔS was as follows Li+ > Na+ > K+. The prepared membranes were characterized by thickness, porosity, water uptake, swelling, chemical stability, morphology analysis and particle size. The membranes were found to be stable in acidic as well as basic environment.