(463g) Mixed Ion Sorption and Transport in a Cation Exchange Polymer Based on Sulfonated Polystyrene

Sorption and transport of sodium chloride, sodium fluoride, sodium nitrate, calcium chloride and their mixtures in a commercial cation exchange membrane based on cross-linked polystyrene with fixed sulfonate ions was investigated. For mixed salt sorption and permeation experiments, binary salt mixtures 50:50 wt were considered. 

Pure and mixed ion transport parameters were correlated to the ion size and valence, as well to the membrane water content. The effects of the second component on salt transport parameters were investigated. When considering mixtures of salts having the same counter-ion (Na⁺), mixed salt sorption and permeability coefficients do not change significantly relative to the values measured in the case of single salt, if they are reported as a function of salt activity coefficient in the contiguous, external solution. When considering mixtures of salts having different counter-ions (Na⁺/Ca²⁺), mixed salt transport parameters depart significantly from the respective values for single salt. The experimental findings were rationalized based on the Donnan theory [1].

[1] F.G. Donnan, Chem. Rev. 1924 1 73-90