Competition between Electrochemical Advanced Oxidation and Electrochemical Hypochlorination of Sulfamethoxazole at a Boron-Doped Diamond Anode

Abstract

Sulfamethoxazole (SMX) was used as a model substrate for electrochemical oxidation at a boron-doped diamond anode in the presence of chloride ion, which is present in many waste streams. In the absence of chloride, oxidation of SMX involves mineralization, an electrochemical advanced oxidation process (EAOP) that is initiated by attack of anode-derived hydroxyl radicals. The rate of disappearance of SMX increased monotonically upon addition of chloride ion but without inhibiting mineralization in the early stages of oxidation. This demonstrated that electrochemical hypochlorination (EH) and EAOP are not mutually exclusive reaction pathways; products of EH can undergo EAOP and vice versa. Persistent chlorinated byproducts were formed in the presence of chloride ion, indicating that chloride is a significant detriment to the success of EAOP. No mineralization was observed upon chemical hypochlorination of SMX with sodium hypochlorite.

Anodic oxidation of organic pollutants on a Ti/SnO2–Sb2O4 anode

“…3 to the experimental data. This behavior is often observed during the anodic oxidation of pollutants containing chlorine in its structure or when chloride salts are used as the electrolyte, as hypochlorite is formed at lower electrochemical potentials than other possible oxidants, like persulfate or hydroxyl radicals [51]. Furthermore, the absorbance removal at 275 nm was much low at the lowest current density, but very similar to the removals of COD and TOC for the same applied current density (Fig.…”

An experimental and modelling study of the electrochemical oxidation of pharmaceuticals using a boron-doped diamond anode

“…An irreversible oxidation peak of CIP appears before the water discharge at 1 V/SCE. Similar electrochemical behaviour was obtained by Boudreau et al [36] and Karuwan et al [37] in a synthetic solution of SMX and SALBU on a BDD anode, respectively. For both cases, the authors observed the deposition of a polymeric film on the anode, before the water discharge.…”

Total mineralization of sulfamethoxazole and aromatic pollutants through Fe2+-montmorillonite catalyzed ozonation

“…Even more oxidative treatments of wastewaters failed in producing total mineralization [30][31][32][33][34][35][36][37][38], generating unavoidably even more toxic derivatives [28].…”