Removal of ammonia nitrogen from water by mesoporous carbon electrode-based membrane capacitance deionization

The removal of ammonia nitrogen from wastewater is always a focus in current water treatment. In this study, a combination of mesoporous carbon electrode and selective ion exchange membrane was used to assemble a membrane capacitor deionization system (MCDI). The optimal process parameters were determined as follows: the plate spacing was 1 mm, the voltage was 1.2 V, and the flow rate was 23.8 mL/min. Under the optimal conditions, the removal efficiency of ammonia nitrogen can reach more than 80%. The quasi-first order kinetics and Langmuir adsorption isotherm model can well describe the adsorption process of MCDI. The nature of physical adsorption between ammonia nitrogen cations and mesoporous carbon electrode was demonstrated by the calculation of activation energy and thermodynamic parameters. Moreover, 1500 mg/L NH₄Cl, NaNO₂, and NaNO₃ solutions were tested respectively. The results showed that the removal efficiencies of NH₄⁺, NO₂^-, and NO₃^- were 82.33%, 90.96%, and 97.73% respectively, indicating that MCDI is feasible to removal different forms of inorganic nitrogen from water.