Uptake of phenylalanine and tyrosine by a strong-acid cation exchanger

The equilibrium and rate of uptake of the amino acids phenylalanine and tyrosine by Amberlite 252, a strongly acidic, cation‐exchange resin, have been investigated. Uptake of the amino acids by the hydrogen form of the resin occurs primarily by the stoichiometric exchange of hydrogen ions and amino acid cations. The amount of amino acid taken up by the resin can be calculated as a function of solution pH and amino acid concentration from a model that takes into account both solution and ion‐exchange equilibria. The rates of uptake of the two amino acids have been determined experimentally for a closed batch system. The results of experiments in which the resin particle size, the flow rate, and the concentration were varied show that intraparticle transport is dominated by the slow diffusion of amino acid cations through the macroreticular polymer structure of the resin, with some contribution from macropore transport of amino acid cations and zwitterions. An intraparticle diffusion model has been developed to describe these results and predict the performance of fixed‐bed operations.