Absence of Donnan Exclusion at High-Concentration Ion Exchange for Macroporous Anionic Resin
High-concentration ion exchange has been studied for an anionic macroporous resin. The mechanism of interaction of Lewatit MP-500 (strong base resin) with several high-concentration inorganic salts was analyzed in order to determine the effect of the Donnan potential in the process. The systems under study were Cl-, SO42- as counter-ions and K+, Na+ as co-ions in different combinations as single electrolytes. These salts were chosen because of their interest as raw materials in the fertilizer industry. The study focuses mainly on the behavior of high-concentration (over 1 M) counter- and co-ions in the anionic resin. The results showed that Donnan exclusion does not take place completely and that electrolyte penetration inside the resin is observed. Furthermore, a certain amount of ion exchange was observed for the co-ions (K+ and Na+) when the resin was presaturated with sulphate and chlorides that were present in the solution. Equilibrium and kinetics data were obtained under these special experimental conditions. Equilibrium constants were obtained for counter-ions and adsorption constants for co-ions using a constant separation factor isotherm, while diffusion coefficients were obtained using a pore diffusion model.
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Document Type: Research Article
Affiliations: 1: Chemical and Environmental Engineering Department, University of Oviedo, Oviedo, Spain 2: Project Management Area, University of Oviedo, Oviedo, Spain
Publication date: July 1, 2007