Optimized design of recycle chromatography to isolate intermediate retained solutes in ternary mixtures: Langmuir isotherm systems.

Batch chromatography with a recycle stream is a popular and simple technique to separate a single target component in a complex mixture with moderate operating conditions. Design of recycle chromatography depends on the retention behaviors of the mixture components. In this work, four nucleosides were considered as solutes. Feed concentration and recycle methods were optimized to isolate only the intermediate retained solute in ternary and pseudo-ternary mixtures. Two recycle methods introduced in our previous work for linear isotherms, the desorbent and feed recycle methods, were compared in terms of productivity and desorbent to feed ratio, D/F, with various feed concentrations for competitive Langmuir isotherm systems. The simulation results show that the target (intermediate retained solute) was separated with over 99.76% purity and 99.88% yield. Productivity of the feed recycle method was increased by up to 162% and D/F was decreased by up to 59% compared to the desorbent recycle method. For the separation of nucleosides, recycle chromatography was compared to eight column simulated moving bed (SMB) cascades with a recycle stream and D/F of the SMB cascades was 58% lower than D/F of recycle chromatography at the same productivity. However, recycle chromatography is much simpler.