For laboratory-scale Capacitive Deionization (CDI) testing, the cell design is critical for accurately measuring salt adsorption capacity (SAC) and average salt adsorption rate (ASAR). Most research setups utilize one of two primary configurations: static (batch) cells or flow-through/flow-between stacks.

The choice of cell usually depends on whether you are focusing on material characterization or system kinetics. (1) Flow-Between (Parallel Plate): The feed solution flows between two parallel electrodes separated by a thin spacer. This is the most common lab setup as it mimics industrial stack designs. (2) Flow-Through: The solution is pumped directly through the thickness of porous electrodes. This typically offers higher kinetics but requires electrodes with high permeability. (3) Membrane CDI (MCDI): Any of the above but with Ion Exchange Membranes (IEMs) placed in front of the electrodes to block co-ions, significantly increasing charge efficiency.

Regarding the cell design, seveal critical points are worth of noting: (1) Dead Volume: Minimize the "extra" volume between the cell outlet and the conductivity probe. High dead volume smears the concentration profile and leads to inaccurate kinetic data. (2) Degassing: Ensure the cell is oriented so that air bubbles can escape easily (usually by pumping from bottom to top), as trapped air blocks the active electrode surface. (3) Compression: Use a torque wrench to tighten the cell assembly. Uneven pressure can lead to high contact resistance or internal leakage.

References:

1. K. Fang, et al., Revealing the intrinsic differences between static and flow electrode capacitive deionization by introducing semi-flow electrodes, Environ. Sci.: Water Res. Technol., 2020,6, 362-372. 

2. C. Zhang, et al. Flow Electrode Capacitive Deionization (FCDI): Recent Developments, Environmental Applications, and Future Perspectives, International Journal of Electrochemical Science, 2021, 16, 210627.