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Charging and Transport Dynamics of a Flow-Through Electrode Capacitive Deionization System
Yatian Qu1,2, Patrick G Campbell2, Ali Hemmatifar1
1Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.
The Journal of Physical Chemistry. B
|January 3, 2018
Summary
Capacitive deionization (CDI) systems performance depends on charging rate, capacitance, and mass transport. Our models and experiments reveal how these factors govern salt removal in flow-through electrode systems.
Area of Science:
- Electrochemistry
- Chemical Engineering
- Environmental Science
Background:
- Capacitive deionization (CDI) is a promising technology for water desalination.
- Understanding the complex interplay of parameters governing CDI performance is crucial for optimization.
Purpose of the Study:
- To investigate the dynamics of salt removal in flow-through electrode CDI systems.
- To develop and validate models that capture the coupled transport and electro-adsorption processes.
- To elucidate the influence of charging rate, capacitance, and mass transport on CDI efficiency.
Main Methods:
- Development of two computational models: a zero-dimensional volume-averaged model and an area-averaged model.
- Experimental validation of the models using flow-through electrode CDI systems.
- Analysis of salt transport under advection-limited and dispersion-limited regimes.
Main Results:
- In advection-limited regimes, differential charge efficiency dictates initial salt adsorption, transitioning to a quasi-steady state.
- Salt removal rate in the quasi-steady state is proportional to applied current scaled by inlet flow rate.
- In dispersion-dominated regimes, adsorption dynamics are governed by differential charge efficiency, cell volume, and diffusion rates, with minimal flow rate effect.
Conclusions:
- Salt removal in flow-through electrode CDI is governed by the combined effects of mass transport, differential charge efficiency, cell capacitance, and charging current.
- The developed models accurately represent the spatial and temporal responses of CDI systems.
- The study provides critical insights for optimizing CDI system design and operation for efficient desalination.
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