Adsorption behavior and kinetics for L-valine separation from aqueous solution using ion exchange resin

Separation of L-valine (L-val) using ion exchange resins from a aqueous solution was successfully performed. Multifactor equilibrium isotherm, adsorption mechanism and kinetics were systematically studied. A multifactor empirical isotherm model was constructed and could demonstrate the equilibrium experimental data at different pH values well. A theoretical model integrating both ion exchange and proton transfer reactions was developed to describe the adsorption capacity of resin, and the theoretical model allowed us to verify the multilayer adsorption at a higher concentrations. Meanwhile, the results of quantum chemistry confirmed the existence of proton transfer reaction and multilayer adsorption on resin. The adsorption of L-val on resin was a spontaneous and endothermic process. Adsorption amount of L-val on cation exchange resin increased with increasing the L-val solution concentration and the temperature but decreased with increasing the diameter of resin. The rate constant (k0) and the apparent reaction coefficient (α) of lumping kinetics and the apparent activation energy of reaction (Ea) were also determined by analyzing the mass transfer process from the main liquid to the active sites of resin.