Modeling of nitrate removal for ion exchange resin in batch and fixed bed experiments

In this study, nitrate removal from aqueous solutions was studied using a nitrate selective ion exchange resin in both batch and fixed bed experiments. Nitrate retention experiments were carried out using nitrate-rich groundwater and several synthetic waters with different initial nitrate concentrations and the presence of competitive ions, such as sulfate. The equilibrium data were modeled and compared using the Langmuir adsorption isotherm and the mass action law and both models described the experimental data well. However, different values of Langmuir coefficients were obtained for different operating conditions, whereas it is possible to state all equilibrium data with a simple general equation obtained by applying the mass action law. A mathematical model (advection–dispersion equation) was solved numerically to predict the dynamic behavior of the columns. The experimental breakthrough curves from column experiments were in good agreement with the model predictions. The mass action isotherm parameters obtained from these column experiments were confirmed by the results of the batch experiments. Consequently, column behavior can be predicted from the batch equilibrium data by using the mass action isotherm. Finally, sensitivity analysis showed that the variation of dispersion coefficient between two times higher and two times lower than the base value was negligible.

► Equilibrium data was modeled by Langmuir adsorption and mass action law isotherm.
► The mass action law model can simulate ion exchange under diverse operating conditions.
► Advection dispersion equation was used to model the ion exchange process in column.
► Model predictions were in agreement with experimental data at different conditions.
► Sensitivity analysis was performed on the column model parameters.