Separation of aliphatic amino acids from aqueous media with an aminophosphonic ion exchanger

The sorption of the aliphatic amino acids glycine and α-alanine by an aminophosphonic ion exchanger is studied and the dynamics of sorption is described using a kinetic equation. Experimental studies were carried out on a designed experimental setup with a fixed ion exchanger layer, in which the purified and regenerating solutions are passed through the sorbent layer in various directions. The heterogeneous ion exchange process includes the transport of sorbent ions in the liquid phase to the grain surface and the removal of desorbed ions from it, interphase transfer, diffusion of sorbed and desorbed ions inside the grain, since not all functional groups of the sorbent are localized on the surface, and a reversible ion exchange reaction. The kinetic equation of the Thomas model takes into account the multistage sorption and adequately describes the dependence of the degree of extraction of the component on the duration of contact of the solution with the ion exchanger layer. The equation of the Thomas model has been modernized taking into account the effect on the dynamics of the process of diffusion resistances in the channels of the layer and the grains of the ion exchanger in a column with a fixed loading. The upgraded model is applied to describe the dynamics of ion exchange of aliphatic amino acids on an aminophosphonic ion exchanger and the possibility of using a one-dimensional capillary flow model to estimate the diffusion resistance during fluid movement in the channels of the ion exchanger layer is shown. The agreement of the calculated and experimental output curves of sorption of aliphatic amino acids from aqueous solutions of various concentrations has been verified. It is shown that the upgraded model adequately describes the dependence of the degree of amino acid extraction on the duration of contact of the solution with the polyampholite layer at different feed rates of the purified solution.