Optimization of preparative chromatographic separation of multiple rare earth elements

Area of Science:

• Chemical Engineering
• Separation Science
• Process Optimization

Background:

• Chromatographic systems are crucial for separating complex mixtures, particularly in rare earth element (REE) processing.
• Optimizing multi-product chromatography requires balancing multiple, often conflicting, objectives like yield, purity, and productivity.
• Existing models may not fully capture the dynamics of multi-component separations, necessitating advanced optimization techniques.

Purpose of the Study:

• To develop and apply a method for optimizing multi-product chromatographic systems with multiple objective functions.
• To investigate the separation of a neodymium, samarium, europium, and gadolinium mixture using ion exchange chromatography.
• To establish an efficient pooling strategy based on component value and Pareto front analysis.

Main Methods:

• Calibration of a homogeneous Langmuir Mobile Phase Modified (LMPM) model to experimental data.
• Application of a multi-objective Differential Evolution algorithm for optimization.
• Integration of component relative value for objective weighting and pooling order prioritization.
• Analysis of the Pareto front to identify optimal operating points and inform pooling strategy.

Main Results:

• Successful calibration of the LMPM model for the specified chromatographic system.
• Identification of optimal operating points along the Pareto front, balancing weighted productivity and weighted yield.
• Demonstration of a prioritizing scheme for pooling order based on relative component values.
• A rule of thumb for pooling strategy selection emerged from the Pareto front analysis, indicated by a gap in objective functions.

Conclusions:

• The developed method effectively optimizes multi-product chromatographic separations by considering multiple objectives.
• The study provides a framework for efficient REE separation, balancing economic factors (relative value) with process performance.
• The Pareto front analysis offers valuable insights into trade-offs and guides the selection of optimal pooling strategies.