An experimental study on the effect of composite electrode on the membrane- assisted electrode in CDI and MCDI processes towards nitrate ion selectivity

The removal of nitrate concentrations above international drinking water standards is a prominent task of governments. In this regard, various technologies such as reverse osmosis, biological denitrification, electrodialysis, and capacitive deionization (CDI) as an electrochemical approach have been used for nitrate removal from water. In the present research study, a novel composite electrode named E2 was synthesized and used to improve the efficiency of the membrane capacitive deionization (MCDI) process for increasing the electrosorption capacity of nitrate from water. E1 as a based electrode composed of activated carbon (AC), PVDF, and E2 as an optimal electrode containing (AC), PVDF, ZrO2, and PANi -ES were utilized. The morphology and structure of the composite electrode were determined using field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller (BET), Fourier-transform infrared spectroscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDAX) techniques. Also, the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods were applied to investigate the electrochemical behavior of the electrodes. In the MCDI process with the presence of the E2 electrode, the amounts of separated nitrate ion and its adsorption efficiency were 7.51 mg/g and 81.6%, respectively; this demonstrated that the capacity of the adsorbed nitrate ion by the MCDI process was 30.34% higher than the CDI process. On the other hand, the E2 electrode, compared to the E1 electrode, ameliorated the performance by almost 50% of the amount of adsorbed nitrate ion and also ion adsorption efficiency during the CDI and MCDI processes.