Green electrochemical process for metronidazole degradation at BDD anode in aqueous solutions via direct and indirect oxidation

• Anodic oxidation, an environmentally friendly process has been deeply investigated to remove the antibiotic metronidazole.
• The efficiency of electrochemical oxidation at boron doped diamond anode was investigated.
• The influence of main operating parameters affecting the removal of this antibiotic was determined.
• The addition of chloride ions in the electrolyte caused an increase in COD removal efficiency.

Anodic oxidation, an environmentally friendly process has been deeply investigated to remove the antibiotic metronidazole (MTZ), dissolved in synthetic wastewaters, via direct and indirect oxidation. Experiments were conducted by boron-doped diamond (BDD) anode in the absence and presence of sodium chloride (NaCl) in the solution. However, no studies have focused on the removal of MTZ using BDD anode or under chlorination process. The chemical oxygen demand (COD) measurement during the processing allowed the evaluation of the kinetics of organic matter decay and the instantaneous current efficiency (ICE). The results have shown that the degradation of MTZ is dependent on its initial concentration, pH, applied current density and NaCl concentration. COD decay follows a pseudo first-order kinetics, and the process was under mass transport control within the range studied, regardless of the experimental conditions. The electrochemical degradation is significantly accelerated by the presence of NaCl in the solution (94% COD removal in just 120 min).