Methodology of isotherm generation: Multicomponent K+ and H+ ion exchange with strong acid cation resin

摘要

This study addressed a need to better understand the influence of experimental parameters employed during the generation of equilibrium ion exchange isotherms. The hypothesis concerned the use of the "constant normality and resin mass" bottle point method to analyse multi-component solution isotherms. In particular, mixed solutions of potassium chloride and hydrochloric acid were investigated in relation to exchange with the acid form of a strong acid cation resin. Initially, a solution of 5.58 meq/L normality was equilibrated with various fixed amounts of resin (0.1 to 0.9 g), and it was found that inaccurate estimates of the maximum loading of potassium ions on the resin were obtained if the experimental parameters were not carefully chosen to ensure a plateau of the potassium ion uptake. Overlaying of all the data recorded at 5.58 meq/L normality showed that a single isotherm was created which suggested the maximum potassium ion loading was 101.5 g K/kg resin. Examination of the impact of changing the solution normality revealed that for the same resin mass used, the isotherm profiles were different in shape, with the general observation that potassium uptake was preferred when the solution normality was decreased. When the presence of H+ counter ions was taken into account, the total resin capacity was consistent with previous studies of strong acid cation resin with potassium chloride in solution. In addition, the separation factor between potassium ions and protons on the resin surface was found to be 2.54 under the experimental conditions used.