چكيده به لاتين
The capacitive deionization (CDI) method is one of the new technologies used in the field of removal of nitrate from water, which is based on the performance of an electrochemical system. One of the key elements in this process is the electrodes, which play a basic role, so in this study, in order to remove nitrate from feed solution using this technology, it was attempted introduce a new composite electrode, its manufacturing, and to be employed. To determine the optimal percentage composition of materials of the electrodes to improve wettability, electrical conductivity and surface properties of the electrode t[bfo achieve higher capacitance, the experimental design method based on "mixture design" (by the D-optimal method) was used by design-expert software. The percentage composition of materials were included activated carbon (80 wt.%), polyvinylidene fluoride powder (8 wt.%) zirconium dioxide (6 wt.%) nanoparticles and polyaniline emeraldine salt (6 wt.%) nanoparticles. The cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FESEM), porosity and special surface area measurement, and calculation of contact angle, fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and x-ray energy diffraction spectroscopy (EDS) were used to investigate the electrochemical behavior and to determine the physical properties, structural, elemental mapping, and functional groups of the electrodes, respectively. Next, the cyclic voltammetry and the electrochemical impedance spectroscopy tests were performed to determine the absorption capacity and electrical resistance to ionic charge transfer in a three-electrode cell with the carbon composite electrodes size (1cm2) and the presence of 1 M solution of NaNO3. Results showed the maximum specific capacitance and charge transfer resistance of 90.24 Fg-1 and 2.4 Ω, respectively, for E4 as an optimized composite electrode determined by CV and EIS analysis, respectively, which its performance was better than other electrodes. Then, the composite electrode with 5×5 cm2 size manufactured based on the ex situ technique(with the percentage composition of the above ), and was employed. Removal of nitrate ions performed by setup of CDI and MCDI using these electrodes ( with size 5×5 cm2, thickness 220µm, and weight 0.985 g) in the presence of 200 mL of binery salt feed solution (NaNO3 and NaCl) with initial concentration 100 mg/L and flow rate of 10 mL/min during the batch process with constant voltage 2.0 volts The absorption-desorption cycle was carried out with the applied voltage of 2.0 volts and the short-circuit mode (zero voltage), respectively. The results showed that the amount of adsorbed nitrate ions and the ion removal efficiency by MCDI process were determined 7.51 mg/g and 81.06%, while those parameters were calculated 5.23 mg/g and 56.49% for CDI process. These results indicated the capacity of adsorbed nitrate ions by MCDI process was 30.34% higher than CDI process. In addition, the selectivity of nitrate ion in comparison with chloride ion was about 2 times in MCDI process than CDI process.
