Conditions for reagent-free (non-exchange) separation of amino acids containing mixtures on anion exchangers
Since in non-exchange sorption the development along the column is accompanied by a significant blurring due to molecular diffusion and leads to a significant decrease in the efficiency of separation in comparison with ion exchange, the aim of the work is establish rational conditions for the separation of amino acid-containing mixtures by ion exchangers at non-exchange absorption conditions. The work is devoted to the study of the influence of the sorbent layer height, diameter, the density of its packaging, the characteristics of hydrodynamic regimes, as well as the concentration and ratio of the solution components on the appearance of output curves in sorption-desorption processes. Since the main condition of reagentless separation amino acids’s mixtures is what use of ion exchangers in salt form, which eliminates overcharging and securing zwitterion ion exchange, demineralization of amino acid solutions was studied on the mixture of tryptophan and calcium chloride with different content of highly basic components at high based anion exchanger AV-17-2P in Cl-form. It was found that the separation of amino acid-containing mixtures should be carried out under the follow conditions: the low and wide layer of fine sorbent in salt form in the absence of free volume in the upper and lower parts of the column; low rates of solution supply; alternating stages of sorption and desorption. The process is repeated several cycles to completely separate the components with using of water for desorption. For studying system tryptophan passes into the sorbent and the solution is depleted in amino acid the salt concentration remains unchanged at the sorption stage. Thus, at the first stage of desorption, a pure solution of this amino acid is obtained. Desorption of the absorbed component is effectively carried out by water using quantities comparable to the volume of the solution with the separated mixture.