Ozone photolysis of paracetamol in aqueous solution: Fid-Bau Portal

Ozone photolysis of paracetamol in aqueous solution

Neamţu, Mariana / Bobu, Maria / Kettrup, Antonius / Siminiceanu, Ilie

The degradation of a paracetamol (N-acetil-para-aminofenol) aqueous solution (C ⁰ _P = 5 mmol L⁻¹) is studied in a bench-scale setup by means of simple ozonation (O₃) and ozonation catalyzed with UV light (O₃/UV) in order to quantify the influence of UV light on the degradation process. The results have shown that under the adopted experimental conditions (25°C, applied ozone dose = 9.8 mg L⁻¹ and gas flow rate of 20 L h⁻¹) both oxidative systems are capable of removing the substrate with mineralization degrees up to 51% for ozonation and 53% for O₃/UV. HPICE chromatography allowed the detection of nitrate ions and maleic and oxalic acids as ultimate carboxylic acids. The experimental data have been interpreted through 5 indicators: the conversion of paracetamol (X_P), the conversion degree of TOC (X_TOC), the apparent rate constant (k_ap), the Hatta number (Ha) and the enhancement factor (E). The main advantage of photo-ozonation compared to simple ozonation was a more advanced conversion (79% vs. 92% after 90 min). The paracetamol decay follows a pseudo–first-order reaction with a superior rate constant (higher by 54%) for the UV catalyzed system in comparison with direct ozonation. Mineralization is slightly accelerated (+4%) in the O₃/UV system, due to the additional production of hydroxyl radicals induced by the UV light and a higher Hatta number (+24%). Nevertheless, the process was still in the slow reaction kinetic regime (Ha < 0.3), and the enhancement factor was not significantly increased. The results are useful for the design and scale-up of the gas-liquid processes.