Lysine Adsorption on Cation Exchange Resin. II. Column Adsorption/Desorption Behavior and Modeling

Abstract

Column adsorption and desorption of lysine on the strong acid cation exchanger Dowex HCR‐W2 are studied experimentally and theoretically. The lysine breakthrough curves have a complex behavior that depends on the pH of the feed solution. At high pH, when lysine is predominately monovalent, an equilibrium binding capacity approaching the total resin ion exchange capacity is obtained but the breakthrough curve is gradual. Conversely, at low feed pH, when lysine is predominately divalent, a sharper breakthrough curve is obtained but the equilibrium binding capacity is only about one half of the total resin ion exchange capacity. Finally, at intermediate feed pH, when divalent and monovalent lysine forms coexist in the feed solution, a breakthrough curve comprising an initial gradual wave followed by a plateau and then by a sharper front is obtained. A local equilibrium model is developed to describe the wave shapes. The model is in agreement with the experimentally observed wave shapes although it only affords a qualitative prediction of the effluent concentration profiles. A rate model, taking into account the coupled diffusion of lysine cations, ammonium ion, potassium ion, and hydrogen ion in the resin as well as the reversible interconversion of divalent and monovalent lysine, is thus developed for a quantitative prediction. The rate model is in excellent agreement with experimental effluent concentration profiles and provides a means to rationally design and optimize lysine ion exchange processes.