Evaluation of synergistic effects of coupling capacitive deionization (CDI) and UV oxidation processes for saline water treatment

Abstract

In the present study, the synergistic effects of capacitive deionization (CDI) and ultraviolet (UV) based advanced oxidation process (AOP) have been investigated for the simultaneous removal of NaCl salt and humic acid (HA), by an organic contaminant approach. A specific CDI rod geometry setup was utilized to allow for direct UV irradiation on the electrodes’ surface during CDI experiments. The characteristics of the coated electrodes were examined by scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). The results of desalination experiments showed that the maximum salt adsorption capacity (mSAC) and salt removal efficiency were 3.96 mg/g and 52.5%, respectively under constant operating conditions (i.e., an applied voltage of 1.2 V and an initial salt concentration of 20 mM). Also, experiments involving simultaneous removal of salt and organic contaminant, demonstrated that the presence of HA in water has little impact on the desalination efficiency. After combining CDI and AOP under constant operating conditions (i.e., an applied voltage of 1.2 V, UV irradiation with a fluence rate of 6.8 mW/cm2, and initial concentrations of 20 mM of salt and 10 ppm of HA), the HA removal efficiencies in the charge and discharge reservoirs were 76.0% and 75.4%, respectively after 200 min of experimental time.