Metronidazole Electro-Oxidation Degradation on a Pilot Scale

In this investigation, metronidazole was degraded in an aqueous solution through electro-oxidation. A DiaClean® cell was used to accommodate a stainless-steel electrode as a cathode and a boron-doped diamond (BDD) electrode as anode. This setup provides several electrochemical advantages, including low currents, a high operational potential, and, frequently, low adsorption compared to conventional carbon materials. The physicochemical parameters were estimated after 180 min of treatment, applying different current densities. The concentration of metronidazole was monitored by HPLC to assess degradation, resulting in 30.67% for 30 mA cm−2, 79.4% for 50 mA cm−2, and 100% for 100 mA cm−2. The TOC mineralization percentages were 12.71% for 30 mA cm−2, 14.8% for 50 mA cm−2, and 29.9% for 100 mA cm−2. Also, biodegradability indices of 0.70 for 30 mA cm−2, 0.81 for 50 mA cm−2, and 0.93 for 100 mA cm−2 were obtained. The byproducts found were formic acid and acetic acid. A pseudo-first order kinetic model was thus obtained due to the quasi-stable concentration achieved through hydroxyl radicals, given that they do not accumulate in the medium, due to their high rate of destruction and short lifespan.