Modeling of Ionic Transport in Neutralization Dialytic Deionization

A deionization process by neutralization dialysis was studied. The dialyzer had both cation- and anion-exchange membranes and three parallel-plate channels. A theoretical model for the continuous process was developed on the basis of transport equations in terms of diffusion, migration and convection of each ion. The basic equations obtained were solved numerically, using a finite-difference technique. For a circulating process in which a feed solution circulated with a reservoir, numerical calculations were also conducted by applying the model for the continuous process with a pseudo-steady state assumption. Simultaneously, deionization experiments of neutralization dialysis for a KC1 feed solution were carried out in both continuous and circulating processes. The validity of the model and the numerical calculations was checked by comparing with experimental results. The effect of Reynolds number on mean dialytic rates and fractional attainment of deionization of each ion was quantitatively elucidated for the continuous process. The effect of the pH of the feed solution on the mean dialytic rates was also discussed on the basis of the data for the circulating process.