Some sorption patterns of phenylalanine and tryptophan from one- and two-component solutions by super-crosslinked sorbent MN-150

Abstract

At the moment, of significant scientific interest is the study of sorption systems where hydrophobic interactions prevail over polar interactions, which makes the separation of components possible due to the difference in interactions of nonpolar components with the sorbent matrix.

In our study, we investigated the sorption of tryptophan and phenylalanine amino acids and their mixtures by an MN-150 super-crosslinked sorbent under static and dynamic conditions. The study demonstrated that in the entire range of concentrations studied, tryptophan, being more hydrophobic, is absorbed better than phenylalanine, which is less hydrophobic. In a case of joint sorption, the absorption rate decreases for both compounds because of the competition for sorption sites in the MN-150 phase. The study demonstrated that the sorption isotherms are best described by the Freundlich equation. As a result, we obtained equilibrium constants and the values of the limiting sorption for the studied amino acids.

When studying the sorption of phenylalanine, tryptophan, and their mixture under dynamic conditions, we determined that sharp fronts can be ensured when the sorption is performed on the layers of sorbent thicker than 6 cm and with large concentrations of the solution (0.03 М). Using a method based on the asymptotic equation of the output curve, when the front was stationary, we obtained the kinetic characteristics of sorption in the studied systems. We also determined the intradiffusion limiting stage of the sorption kinetics for both amino acids. The study determined the diffusion coefficients of amino acids in the sorbent phase. The diffusion coefficient of phenylalanine was higher than that of tryptophan. When adsorbed from two-component solutions, the speed of each component in the grain increases, because when two aromatic amino acids are introduced into the sorbent, the grid of hydrogen bonds is significantly destroyed, and the compounds move faster.

We investigated the sorption/desorption of a tryptophan-phenylalanine mixture by an MN-150 sorbent under dynamic conditions. During the sorption stage, both amino acids are absorbed, and the resulting solution is weakened by tryptophan, which is better absorbed. During the desorption stage, first a solution of amino acids with predominant tryptophan flows out (until phenylalanine is washed out completely). Then a pure tryptophan solution is obtained. Since the ionic form of the sorbent remains unchanged, there is no need for the regeneration of the sorbent. The process is cyclic and is performed until the complete separation of the components.