Model of non-equilibrium thermodynamics of competitive diffusive transport in ion exchangers under conditions of excess-equivalent sorption

Abstract

Objects of research are partially dissociated ion exchangers as non equilibrium systems under conditions of relaxation and selective excess-equivalent exchange of counter-ions and their solutions of strong electrolytes with common co-ions. Subject is the description of relaxation of nonequilibrium partially dissociating medium at non-equivalent exchange and its management on individual interdiffusion coefficients as the main practical indicator of the efficiency of the competing transport of ions in ternary ion exchange systems. Objective: to identify the relationship of coefficients of interdiffusion counterions with the compositions of the phases and other factors of effect on the state of non-equilibrium system. Method of research is based on the application phenomenological method to the description of a competing diffusion transport of laws of thermodynamics of non equilibrium processes under conditions in a partial dissociation of ion exchange medium and excess equivalent exchange of electrolytes between interacting phases.
The proposed model is based on application of thermodynamics of nonequilibrium processes at partial dissociation of ion exchanger and excess absorption of ions and co-ions from the external electrolyte solution. It is shown, that in this case, the transport of ions inside ion exchanger, in contrast to the equivalent exchange, is carried out at least on the base of three parallel diffusion mechanisms. It is also proved that inthe first approximation, a phenomenological description of counterions flows can be reduced to Fick's law with the individual coefficients of interdiffusion coordinated with diffusion of co-ions (physical-chemical determinate and statistically conditioned). Expressions of their current local depending on the mobility counterion for each of the transport mechanisms, concentration and mobility of the absorbed co-ions, grossion composition and dissociation of the functional groups of the ion exchanger in the elementary (nanoscale) volume of its phase are found in analytical form.