Comparison of electro-oxidation coupled with UV irradiation (UV/EO) versus conventional oxidation processes (UV irradiation, chlorination, electro-oxidation, and UV/chlorine) for atenolol removal: role of operating parameters, energy performance, and toxicity

Abstract

In this study, electro-oxidation combined with UV irradiation (UV/EO) was used for atenolol (ATL) removal, and the results were compared with those of electro-oxidation (EO), UV irradiation, UV/chlorine, and chlorination. In addition, effects of current density (CD), UV intensity, electric potential, electrolyte (NaCl) concentration, ATL concentration, pH, and free radicals were studied. The UV/EO process was the most effective for ATL removal, followed by UV/chlorine, EO, chlorination, and UV irradiation. The ATL degradation was described by a pseudo-first-order rate model, and the observed rate constant (k') for UV/EO exhibited a direct proportionality to CD, NaCl concentration, and UV intensity. In contrast, the results were opposite for pH and ATL concentration. A change in the electric potential did not affect the UV/EO efficiency. The energy consumption of the UV/EO process exhibited an inverse proportionality to the k' value. ˙OH played the major role in ATL removal, while the role of RCS was minor. The kinetic degradation of ATL by ˙Cl (k_Cl˙) was 1.55 × 10¹¹ M⁻¹ s⁻¹. Intermediate products formed during ATL oxidation exhibited higher toxicity than the parent compound. This finding highlights the potential risks associated with the formation of highly toxic byproducts. Therefore, it is necessary to optimize the design and operating parameters of the UV/EO system to prevent the formation and accumulation of harmful intermediates.