Modelling of anion-exchange membrane transport properties with taking into account the change in exchange capacity and swelling when varying bathing solution concentration and pH

摘要: Abstract In this paper we take into account the variation of anion-exchange membrane swelling and effective exchange capacity with changing concentration and/or pH bathing solution when simulating transport characteristics (the electric conductivity, diffusion permeability ion numbers). Two main structural elements are distinguished: a microporous polyelectrolyte gel assumed homogeneous, macropores including defects voids. It is supposed that only exerts osmotic pressure, which causes described in our model by Gregor equation, employs mole fractions free bound water. Three types ion-exchange functional groups, namely, secondary, tertiary quaternary amino groups taken account. The degree dissociation these depends on internal pH, equilibriums between protonated deprotonated forms. Donnan equations electroneutrality condition used to calculate membrane. microheterogeneous based Nernst-Planck describe transport. We coefficients depend swelling, dependence Mackie-Meares equation. parameters include equivalent volume dry gel, fraction macropores, others. results calculations compared experimental data numbers for two heterogeneous membranes MA-40 MA-41 (Shchekinoazot, Russia) differed weakly basic groups. A good quantitative agreement theory experiment found both using same set hydration chemical equilibrium constants secondary particular, it shown increasing solution, passes through maximum, explained corresponding maximum water content. higher content larger pores, leads values amount sorbed electrolyte. Together varying content, as function external determines non-trivial behavior equilibrated NaCl solutions different pH.