Electrochemical treatment of simulated wastewater containing nitroaromatic compound with cobalt-titanium electrode

The Co₃O₄-Ti electrodes were successfully prepared via calcination method to degrade nitrogen-containing (TNP) simulate wastewater in this reaserch. SEM and EDS were employed to analyze the morphology and element composition on Co₃O₄-Ti electrode, revealing the successful load of cobalt element. Then the electrochemical performance was evaluated by CV and indicated a better redox performance of electrode. Furthermore, five factors as processing time (A), electrolyte concentration (B), pH (C), initial concentration of TNP (D), and current density (E) were systematic studied in electrical treatment process. The removal rate of TN could be 77%. After the optimization work by RSM, the removal rate of TN raised up to 81% with the condition as: A of 180 min, B of 0.05 M, C of 3, D of 400 mg L^-1, and E of 20 mA cm^-2. The sequence of significants is: C > D > A > E > B. Mechanism analysis revealed that the entire process could be divided into two stages. In the first stage, organic nitrogen compounds were converted into inorganic nitrogen species, such as NO₃-N. The oxidation and reduction would react owing to the generating of ·OH at second stage in order to turn the NO₃-N into NO₂-N, NH₄-N or N_2. The activation of ·OH on the surface of Co₃O₄-Ti electrode possesses the exothermic nature with transition theory. The energy calculation of 1.168 eV indicated these reactions could occur spontaneously.