Separation of phenylalanine and tyrosine by ion-exchange using a strong-base anionic resin. II. Cyclic adsorption/desorption studies

Cyclic adsorption and desorption dynamics of phenylalanine (Phe) and tyrosine (Tyr) was investigated in a column packed with a strong anionic resin, Diaion PA316, under different pH conditions. Experiments were performed in order to study the effect of the pH in two sequential bed saturations keeping constant the feed concentration. A adsorption step at isoelectric pH (approximate to 6) followed by a desorption step at high pH (12-13) causes an overshoot in the breakthrough curves due to lower affinity resin by amino acid under alkaline conditions. Contrarily to this behaviour, the solution that leaves the column reaches a zero concentration of amino acid during a certain time in two consecutive saturations at high pH and isoelectric pH. The regeneration bed with 0.14 M NaOH is almost effective for conditions less favourable of sorption of amino acid by the resin. Satisfactory agreement was achieved between experimental and simulated results using a mathematical model that considers axial dispersed plug flow and intraparticle mass transfer described by the linear driving force model. Preliminary pH parametric pumping experiments, in semi-continuous mode, enabled to achieve a concentration factor of the top product of approximate to 2.3 and 2.0 for Phe and Tyr during 10 cycles of operation. (C) 2012 Elsevier B.V. All rights reserved.