STUDY OF THE INFLUENCE OF THE CO-ION NATURE ON THE NITRATE-CHLORIDE ION-EXCHANGE IN DILUTED AND CONCENTRATED-SOLUTIONS

The influence of the co-ion nature on the nitrate-chloride selectivity coefficient in diluted/concentrated media has been studied. The varia tion of this selectivity coefficient as a function of the water activi ty of the solution was determined for three anion exchangers of variou s crosslinking degrees (X16, X4, and X2) in solutions of XCl-XNO(3) mi xtures when X is K+, NH4+, Na+, and Li+. This study was performed unde r conditions in which the concentrations of both exchangeable anions ( nitrate and chloride) in solution were similar and also when one of th e exchangeable anions was predominant in solution. Results show that t he nature of the co-ion can have an important influence on the nitrate -chloride selectivity coefficient and that this influence is higher wh en the resin crosslinking degree and solution concentration increase, that is, when the water activity of the solution decreases. The ratio of the concentrations in solution of both exchangeable anions may or m ay not modify the selectivity coefficient depending on the co-ion's na ture.