Modeling of closed-loop recycling dual-mode counter-current chromatography based on non-ideal recycling model

Closed-loop recycling dual-mode counter-current chromatography (CLR DM CCC) includes two separation stages: 1 - closed-loop recycling separation of solutes with mobile x-phase (CLR CCC); 2 - separation of solutes with the mobile y-phase in the opposite flow direction. Previous analysis of CLR DM CCC separations has been limited to the ideal recycling model, which neglects extra-column dispersion. In this study, the analysis of CLR CCC separations is based on the non-ideal recycling model, which takes into account the extra-column dispersion caused by the recycling system. This is of great practical importance, since by selecting the optimal parameters of the recycling system the separation can be significantly improved. Comparative analysis of CLR CCC and CLR DM CCC separations has shown that at low separations factors compounds with low partition coefficients can be separated by CLR CCC using recycling systems with a long recycling line; the separation of compounds with high partition coefficients and the separation of complex mixtures can be performed by CLR DM CCC. Simple equations for simulation and design of CLR DM CCC separations are developed. Several variants of the implementation of this separation method are discussed; examples of simulation are presented in "Mathcad" program. (C) 2019 Elsevier B.V. All rights reserved.