Process parameters of Capacitive Deionization (CDI) was investigated and optimized in this study. The effect of adsorption period (7–13 min), flow rate (5–20 ml min−1), and NaCl concentration (2–22 mM) on salt adsorption capacity was examined via Box-Behnken experimental design approach. A quadratic regression model (R2 = 0.9987) was developed, revealing significant individual and binary effects between process parameters and salt adsorption capacity. The ANOVA results demonstrated its high significance with the p-value<0.0001. Optimal conditions varied with salt concentration, indicating significant interactions between the parameters. Maximum salt adsorption capacity occurred at 5 ml min−1 flow rate and 13 min adsorption period for 22 mM NaCl, whereas for 12 mM and 2 mM NaCl concentrations, maximum adsorption capacity was obtained at the flow rate of 20 ml min−1 and duration of 13 min. This study provided deep insights into CDI modelling and optimization, crucial for water treatment advancements.