Project Summary
A federal research organization engaged us to develop a robust mathematical model based on physical and chemical behaviour of an electrochemical system to simulate the separation of rare earth elements (REEs) using electrodialysis-assisted solvent extraction. The goal was to optimize the process performance and to predict the purity and yield of critical REEs, specifically Neodymium (Nd), Praseodymium (Pr), Cerium (Ce), and Lanthanum (La), under varied chelation and membrane transport conditions.
Challenge
Conventional separation techniques for rare earths, such as solvent extraction and ion exchange, are complex, capital-intensive, and slow, often requiring 40–50 stages to achieve high purity. Electrodialysis offers a promising alternative but suffers from limited ion selectivity when separating chemically similar REEs. A predictive mathematical model was required to simulate the system’s chemistry, membrane behavior, and transport dynamics with chelation-assisted separation.
Solution
A detailed mathematical model was developed to capture all key aspects of the process, including:
Ion Complexation:
Simulated HEDTA-assisted chelation behavior for REEs, accounting for dissociation equilibria and stability constants.
Membrane Ion Exchange:
Modeled transport across cation exchange membranes, factoring in partitioning, ion competition, and membrane capacity.
Electrodialysis Dynamics:
- Current density and voltage-resistance relationships
- Diffusion and electromigration flux
- Nernst–Planck-based transport mechanisms
- Membrane resistances and system tortuosity
Key Performance Indicators:
- Purity and Yield for Nd+Pr product
- Separation factor
- Process time to reach equilibrium
The model was implemented using a time step function and user-adjustable parameters (voltage, pH, HEDTA to Rare Earths ratio, and number of compartments) to simulate dynamic system behavior.
Key Results
Optimal Separation Conditions:
Identified optimum HEDTA to Rare Earths ratio that delivered highest purity with maximum yield.
Increasing chelation ratio improved yield but lowered purity due to cross-chelation with Ce and La.
Model Validation:
Experimental data from the client confirmed model predictability within reasonable purity and yield margins.
Design Flexibility:
Model supports scenario analysis to design multi-stage electrodialysis systems for yield enhancement.
Business Impact
The modeling tool empowers researchers and process engineers to:
- Rapidly assess Rare Earths separation performance across chelation strategies and membrane configurations
- Minimize experimental trial-and-error by simulating process conditions
- Accelerate development of efficient, scalable electrodialysis systems for clean tech supply chains
This work established a quantitative foundation for future pilot projects, guiding the design of energy-efficient, low-waste technologies for the separation of Rare Earths.
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